Rethinking Mitochondria: The Extracellular Dimension

Abstract

Mitochondria are essential organelles that transform the energy contained in metabolic substrates into ATP while supporting numerous cellular processes. Traditionally regarded as strictly intracellular, growing evidence now demonstrates that mitochondria and mitochondria-derived components can also be released into the extracellular space, giving rise to extracellular mitochondria (ex-Mito). ex-Mito display remarkable heterogeneity, ranging from intact organelles to individual molecular components, free to vesicle encapsulated structures, and with functional states spanning from severely damaged to metabolically active. Their release is mediated by tightly regulated mechanisms in both living and dying cells, and is influenced by cellular stress, activation state, and pathways that control mitochondrial selection, compartmentalization, trafficking, and extrusion. Extracellular release fulfills multiple functions across the organism, including quality control, modulation of cellular identity, inflammatory signaling, and functional support of recipient cells. In the cardiovascular system, ex-Mito contribute to both homeostasis and disease progression. This review summarizes current knowledge of ex-Mito forms, mechanisms of release, and patho-physiological relevance, and highlights their emerging potential as therapeutic targets in cardiovascular patho-physiology and beyond.

2). Introduction

Mitochondria are dynamic and multifunctional organelles found in nearly all eukaryotic cells, best known for their critical role in converting the energy stored in metabolites into adenosine triphosphate (ATP) through oxidative phosphorylation¹. This essential process has earned mitochondria the widely recognized epithet “powerhouses of the cell”. However, their contribution to cellular physiology extends far beyond their role in converting metabolic energy into ATP², regulating key processes such as metabolic homeostasis³, calcium flux⁴, reduction-oxidation balance⁵, programmed cell death⁶, or cell signaling⁷. Moreover, their functions can be tailored to the specific needs of the cell type in which they reside and even specialize at the subcellular level⁸.

According to the endosymbiotic theory, mitochondria originated from a free-living bacterium, likely an α-proteobacterium⁹, that established a symbiotic relationship with an ancestral eukaryotic cell, or its precursor. Although the exact process that led to this symbiotic relationship is still a subject of active debate and research¹⁰, the bacterial evolutionary origin of mitochondria is widely accepted¹¹ and remains evident today in their characteristics, including a double-membrane structure, a circular genome, and a semi-autonomous replication and translation machinery. These properties not only support the functional versatility of mitochondria but also render their components potent activators of inflammation and innate immune responses when exposed to the extracellular environment¹². Historically, this ability to elicit immune responses^13,14 supported the view that extracellular mitochondria were primarily associated with pathological conditions, particularly cell injury and death.

Indeed, early in vitro and in vivo observations of mitochondria or mitochondria-derived components in the extracellular space were largely attributed to passive release from dying or damaged cells upon compromised plasma membrane stability^15,16 (Fig.1A). However, accumulating evidence now indicates that mitochondria can also be actively released from viable cells in diverse forms and physiological contexts across multiple tissues and species. This emerging paradigm has been supported by advances in imaging¹⁷, biochemical detection¹⁸, and sequencing-based methods^19,20 that have enabled the visualization, tracking, and characterization of mitochondria outside the cellular environment (comprehensively addressed in²¹). Despite these technological improvements, our understanding of the biology of extracellular mitochondria remains incomplete. Compared to the well-established roles of mitochondria within cells, the mechanisms governing their extracellular release, biological functions, and impact on tissue physiology and pathology, especially within the cardiovascular system, are still not fully understood and a matter of intense debate.

Figure 1. Cellular pathways involved in mitochondria release.

Cells can release mitochondria and mitochondria-derived components through multiple mechanisms that depend on their physiological state and stress conditions. In dying cells (left), (A) plasma membrane rupture results in the passive release of intact or fragmented mitochondria in free form. (B) Certain non-lytic forms of cell death can also eject these components within extracellular vesicles (EVs). In live cells (right), mitochondrial stress or damage activates quality control pathways that can lead to mitochondrial release. (C) Damaged mitochondria and their components may be packaged into mitochondria-derived vesicles (MDVs), which are routed to endosomes and multivesicular bodies (MVBs). While MVB content is generally destined for intracellular lysosomal degradation, some fuse with the plasma membrane, releasing mitochondria-derived components in the form of exosomes. (D) Damaged mitochondria can also be recruited to autophagosomes. Some autophagosomes can escape lysosomal degradation and fuse with plasma membrane to release mitochondria in different forms. Simultaneously, (E) cell migration and (F) outward budding of the plasma membrane can generate large EVs containing functional or damaged mitochondria. (G) Additionally, free mitochondria may be released through less well-defined mechanisms of mitochondrial extrusion that do not involve vesicles. Collectively, different pathways allow cells to expel mitochondria in diverse functional states and forms. (H) While EV-enclosed forms of extracellular mitochondria require packaging at the cell level, free extracellular mitochondria and mitochondria-derived components may be released as such from cells or result from vesicle rupture at the extracellular space. https://BioRender.com/b1dq5rv.

Some of the key outstanding questions in this area include: what triggers mitochondria release? What are the mechanisms behind their release? What are their fates? And how do these events influence physiological homeostasis or contribute to disease?

In this review, we examine the emerging field of extracellular mitochondria across multiple systems and patho-physiological contexts by addressing (1) the defining characteristics of mitochondria in the extracellular environment, (2) the cellular and molecular mechanisms underlying their release, (3) their functional roles, (4) their implications in physiological and pathological settings, and (5) their emerging relevance in therapeutic strategies. Our aim is to provide a broad mechanistic and conceptual framework to better understand the significance of extracellular mitochondria in the cardiovascular system. To this end, we also include a dedicated section that focuses specifically on their roles in cardiovascular physiology and patho-physiology, where the interplay between extracellular mitochondrial signaling and tissue function is particularly compelling and clinically relevant.

3). Extracellular mitochondria (ex-Mito) definition and heterogeneity

Different cell types, including those of the cardiovascular system, have been reported to release mitochondria or mitochondria-derived components into the extracellular environment under a variety of conditions (Table 1). In this review, we use the term extracellular mitochondria (ex-Mito) to refer broadly to the pool of mitochondria and mitochondria-derived material found outside cells. This extracellular pool is highly heterogeneous and can be further classified based on several key features, including: (i) degree of structural integrity, ranging from intact organelles to fragmented structures or individual components; (ii) functional state, spanning from metabolically active to damaged or compromised forms; and (iii) form in which the released material is presented, whether free or enclosed within membrane-bound vesicles.

Table 1.

Extracellular mitochondria (ex-Mito) released from viable cells

In the Cardiovascular System
Cell Type	Organism	Experimental setup	Reported Structural Integrity	Reported Functional State	Reported Form (EV-diameter)	References
Cardiomyocytes (ventricular)	Mouse, human	In vitro and in vivo	Compromised (damaged cristae and outer / inner membranes)	Dysfunctional (low membrane potential, unresponsive to hyperpolarizing agents, reduced citrate synthase activity, altered proteomic composition)	EV-encapsulated (1–5 μm) and free	18,30
Endothelial cells (ECs)	Mouse, human	In vivo	N/A	Varied (a fraction of them retain membrane potential)	EV-encapsulated (2–6 μm)	47,48
Monocytes	Human	In vitro	N/A	N/A	EV-encapsulated (50 nm-1.5 μm)	49
Neutrophils	Mouse	In vivo	N/A	N/A	Free and EV-encapsulated (0.4–1 μm)	17,50
Platelets	Human	In vitro	Varied	Mixed (O2 consumption suggests functionality, but the electron transport system seems dysfunctional)	Both as free and EV-encapsulated (50 nm-1 μm) in a 2:1 ratio approximately.	19,51–53
Reticulocytes (erythrocyte precursors)	Dogs, chickens	In vivo and in vitro	N/A	N/A	EV-encapsulated (0.5–2 μm)	54–56
In Other Tissues and Contexts
Cell Type	Organism	Experimental setup	Reported Structural Integrity	Reported Functional State	Reported Form (EV-diameter)	References
Astrocytes	Rat, mouse	In vitro and in vivo	Varied	Functional (ATP production, membrane potential and oxygen consumption)	EV-encapsulated (0.3–10 μm)	25,57,58
Brown adipocytes	Mouse	In vivo	Compromised (mitochondria fragments)	Dysfunctional (oxidative damage)	EV-encapsulated (50 nm-0.4 μm)	26
Cancer cells (MDA-MB-231 breast cancer cells)	Human	In vitro	N/A	N/A	EV-encapsulated (0.1–0.5 μm)	39
Cancer cells (PC12 pheochromocytoma)	Rat	In vitro	Compromised (damaged cristae and outer / inner membranes)	N/A	Free and EV-encapsulated (0.3–1.5 μm). 99:1 ratio approx.	46
Cancer cells (DKO-1 colon, Gli36 glioblastoma, MDA-MB-231 breast, CCD-18Co colon, B16-F1 melanoma cancer cells)	Mouse, human	In vitro	Apparently intact	Functional (retain membrane potential)	EV-encapsulated (2–20 μm)	24
Epithelial cells (kidney proximal tubules)	Mouse	In vivo	Varied	N/A	EV-encapsulated (2–10 μm)	59
Fibroblasts (mouse embryonic fibroblasts, MEFs)	Mouse	In vitro	N/A	N/A	EV-encapsulated (50 nm-0.5 μm)	27
Fibroblasts	Mouse, human	In vitro	Compromised (swollen, damaged cristae and outer / inner membranes)	N/A	EV-encapsulated (0.1–0.25 μm)	17,60
Mesenchymal stem cells (MSCs)	Human, rat	In vitro	Varied	N/A	EV-encapsulated (0.1–0.5 μm)	61,62
Microglia	Mouse, rat	In vitro	Compromised (damaged cristae and outer / inner membranes)	Dysfunctional (low membrane potential)	N/A	63
Muscle cells	C.elegans	In vivo	Apparently intact	N/A	EV-encapsulated (2–15 μm)	22
Neurons (retinal ganglion cells)	Mouse	In vivo	Varied	N/A	EV-encapsulated (2–5 μm)	45
Neurons (touch)	C.elegans	In vivo	N/A	Dysfunctional (oxidative damage)	EV-encapsulated (2–8 μm)	31
Osteoblasts	Mouse	In vitro	Compromised (fragmented and altered morphology)	N/A	EV-encapsulated (0.2–0.5 μm)	29
Photoreceptors (cones)	Zebrafish	In vivo	Compromised (reduced cristae and swollen)	N/A	N/A	28
Spermatozoids	C.elegans	In vivo	Apparently intact	Functional (retain membrane potential)	EV-encapsulated (0.5–5 μm)	64
White adipocytes	Mouse	In vivo	N/A	Mixed (respiration competent, but presence of oxidative damage)	EV-encapsulated (30 nm-0.5 μm) and free	32,65,66

While these categories and their implications are discussed in more detail below, the diversity of ex-Mito reflects a complex and tightly regulated extension of mitochondrial biology beyond the cell, arising from cells under various conditions and involving distinct biogenesis mechanisms.

3.1. Structural integrity and functional state of ex-Mito

ex-Mito can present with varying levels of structural integrity and functional capacity (Table 1). These two features are typically interrelated and will therefore be discussed together. For instance, mitochondria that appear structurally intact often retain greater functional capacity, whereas those that are structurally compromised usually exhibit impaired functionality.

In some cases, ex-Mito appear as intact organelles under transmission electron microscopy (TEM)^18,19,22,23 and contain mitochondrial DNA (mtDNA) of sufficient quality to allow polymerase chain reaction (PCR) amplification^19,20, suggesting preservation of functionality. Consistently, some ex-Mito released in both in vitro and in vivo settings have been shown to retain mitochondrial membrane potential, lost upon treatment with depolarizing agents^18,23,24, as well as residual respiratory capacity, as evidenced by oxygen consumption and ATP production assays^19,20,23,25.

In other cases, ex-Mito present as clearly fragmented or structurally altered organelles, displaying disrupted cristae and ruptured membranes observable by TEM^{17,18,26–28}. These morphological changes are often accompanied by alterations in the expression of proteins critical for mitochondrial integrity^18,29, such as reduced levels of OPA1 (involved in mitochondrial fusion), FIS1 (involved in mitochondrial fission), and loss of CYTC and AIFM1, which are typically released from damaged mitochondria¹⁸. These structurally compromised ex-Mito generally exhibit hallmarks of functional decline, including loss of membrane potential^18,30, lack of response to hyperpolarizing agents^18,30, reduced citrate synthase activity¹⁸, and elevated levels of reactive oxygen species (ROS) and oxidized components^17,26,31,32.

Importantly, the distinction between “intact/functional” and “damaged/dysfunctional” ex-Mito should not be viewed as binary but rather as a continuum. Although intact ex-Mito typically exhibit higher membrane potential and respiratory activity, structurally altered or biochemically compromised mitochondria may still retain partial functionality. Such residual activity, while diminished relative to fully intact organelles, can nonetheless be sufficient to ameliorate severe respiratory deficiencies in recipient cells^25,33,34, as discussed in more detail below.

Additionally, mitochondria-derived components such as mtDNA, mitochondrial proteins, and membrane fragments have been detected extracellularly^15,35–39. Although these molecular constituents lack the functional properties of intact mitochondria, they may nonetheless have biological activity, including triggering responses in recipient cells³⁵, and serving as inflammatory mediators^40,41. It remains unclear whether these elements are directly released in fragmented form or result from the breakdown or incomplete clearance of larger ex-Mito particles.

The diversity in the structural and functional states of ex-Mito can be interpreted in several ways. One possibility is that different cell types selectively release mitochondria with varying degrees of integrity and functionality to fulfill distinct biological purposes. For example, functional mitochondria may be released to support or restore mitochondrial function in neighboring cells, whereas damaged mitochondria may be extruded as part of a cellular quality control mechanism. Alternatively, cells might release mitochondria in a broad spectrum of forms and states, with the balance between intact and compromised ex-Mito shaped by the physiological context and intrinsic properties of the releasing cells. In either case, this heterogeneity offers valuable insights into the origins, fate, and potential functions of ex-Mito, as discussed further below.

3.2. ex-Mito forms: free or EV-encapsulated

Based on their contact with the extracellular media, ex-Mito can be classified into two primary forms: (i) as free, naked mitochondria or mitochondria-derived components directly exposed to the extracellular environment, or (ii) enclosed within membrane-bound vesicles.

ex-Mito are often observed enclosed within extracellular vesicles (EVs), lipid bilayer-bound particles that originate from different cellular compartments⁴². Multiple pathways, described in more detail in the next section, contribute to the formation of these ex-Mito-containing EVs, including: apoptotic bodies and other EVs formed during cell death (Fig.1B); multivesicular bodies (MVBs), endocytic vesicles that capture mitochondrial-derived components or vesicles (MDVs) and release them as exosomes (Fig.1C); autophagy, a degradative pathway that can result in the ejection of cargo into the extracellular space (Fig.1D); migrasomes, EVs formed at the trailing pole of migrating cells through a process called mitocytosis (Fig.1E); and ectosomes, large vesicles generated by outward budding of the plasma membrane through a process called ectocytosis (Fig.1F). Vesicles derived from these pathways vary widely in size, ranging from nanometers for exosomes to several microns for ectosomes⁴³.

Mitochondria size and shape can also vary considerably between different cell types, but usually average around 0.5–1 μm in width and 1–2 μm in length⁴⁴. Thus, while small EVs such as exosomes (30–200 nm diameter) can accommodate mitochondrial components like mtDNA³⁵ or proteins³², the encapsulation of whole mitochondria or mitochondrial fragments of larger size typically requires larger vesicles, ranging from 200 nm to several microns in diameter. Notably, some of these larger EVs can even enclose multiple mitochondria simultaneously^{17,18,22,24,31,45,59}, suggesting that certain cells possess specialized mechanisms to expel mitochondria in bulk. The relatively large size of these ex-Mito-containing vesicles has facilitated the live visualization of mitochondria ejection across different cell types and organisms^18,31 and helped establish EV-mediated packaging as a key route for the regulated release of extracellular mitochondria.

Non-membrane-bound (“free”) ex-Mito have been observed in a wide range of contexts, both in vivo and in vitro^{15,16,18,20,46}, highlighting their relevance in organismal patho-physiology. However, their presence in free form does not necessarily imply that they were originally released in this form, since multiple mechanisms can explain the appearance of free ex-Mito. For example, direct release of free ex-Mito can occur passively, as a consequence of plasma membrane rupture during necrotic cell death¹⁶ (Fig.1A), or actively, via secretory pathways that do not involve cell lysis⁴⁶. Such pathways may involve currently undefined mechanisms (Fig.1G); alternatively free ex-Mito may arise secondarily, through the rupture or degradation of mitochondria-containing vesicles (Fig.1H), further contributing to the pool of extracellular mitochondria. In favor of this last source of ex-Mito, conditions affecting the clearance of EV-encapsulated mitochondria lead to the accumulation of free ex-Mito over time¹⁸.

The distinction between EV-encapsulated and free ex-Mito is not merely structural; it has important implications for the stability, functional potential, immune recognition, and signaling capacity of ex-Mito, as discussed further below. In contrast to the better-established functional divide between healthy and damaged ex-Mito, it remains unclear whether the physical form, free or vesicle-enclosed, reflects specific biological roles. While it is reasonable to hypothesize that these forms may differ in their physiological consequences, further studies are needed to determine whether cells actively direct mitochondria into different forms of ex-Mito based on context, or if these forms result from separate cellular processes with independent patho-physiological outcomes.

4). Mechanisms and conditions involved in mitochondria release

Substantial evidence indicates that ex-Mito can be released passively as byproducts of membrane rupture in dying cells, or actively through tightly regulated processes in both dying and living cells. While mitochondria release can occur under normal conditions, various stressors and signaling cues can markedly influence the amount and type of ex-Mito, highlighting the complexity and regulation of this process. As previously discussed, ex-Mito can take multiple forms and the mechanisms governing their formation and secretion vary depending on cell type and context.

In this section, we will discuss the mechanisms and conditions involved in mitochondrial release that have been described across different cell types and experimental setups. While this broader perspective provides a better understanding of ex-Mito biology, we note that some of these pathways have not been tested in all contexts and may not necessarily apply to cells of the cardiovascular system or to cardiovascular patho-physiology. We summarize current knowledge on the pathways and triggers that regulate mitochondria release, from both dying and viable cells, discussing the cellular machinery involved and the conditions that influence this process across different systems and patho-physiological contexts. Cardiovascular-related examples are specifically highlighted to illustrate how these general mechanisms can impact cardiovascular physiology and disease. Understanding these molecular mechanisms is critical, as they not only reveal fundamental aspects of mitochondrial biology but also offer potential therapeutic targets for modulating ex-Mito in contexts such as cardiovascular health and disease.

4.1. Mitochondria release from dying cells

Different types of cell death (reviewed elsewhere^67,68) can result in the release or dissemination of intracellular material, including mitochondria, to the extracellular media in both free and EV-encapsulated forms (Fig.1A–B). This process is particularly relevant to cardiovascular diseases, as ex-Mito are commonly observed in conditions such as atherosclerosis^69–71, stroke⁷² and myocardial infarction^73–76, which are discussed in more detail below. Here, we briefly summarize how different cell death mechanisms may influence the extracellular presence of mitochondria or mitochondrial components.

It may be expected that different forms of cell death lead to distinct modes of mitochondrial release, for example apoptosis producing EV-encapsulated mitochondria and lytic processes such as necrosis releasing free mitochondria. Nevertheless, evidence indicates that different forms of ex-Mito can also occur across various cell death programs. During apoptosis, cells typically package their mitochondria within apoptotic bodies, which are subsequently disseminated into the extracellular milieu⁷⁷. However, the nature of the apoptotic stimulus has been shown to influence the mode of mitochondria release. For example, TNFα-induced but not cisplatin-induced apoptosis leads to the release of free fragmented mitochondria rather than their inclusion in apoptotic bodies⁷⁸. Necrotic and necroptotic cell death, characterized by plasma membrane rupture, often results in the leakage of free mitochondria⁷⁹. Yet exceptions also exist, as necroptotic macrophages can release mitochondria enclosed in EV-encapsulated microparticles⁸⁰, whereas fibroblasts and Jurkat T cells undergoing necroptosis have been reported to release intact free mitochondria prior to membrane rupture¹⁶, raising the possibility that mitochondria release in this context may involve alternative processes rather than being solely a passive consequence of lysis.

Taken together, these observations suggest that the release of extracellular mitochondria from dying cells is not exclusively determined by the type of cell death but instead reflects a more complex and context-dependent phenomenon. The underlying mechanisms remain poorly understood, including whether ex-Mito arise from active export pathways or represent passive byproducts of membrane rupture, and if ex-Mito released during different forms of cell death retain functional properties.

4.2. Mitochondria release from live cells

The release of mitochondria from viable cells has been extensively documented in vitro and in multiple animal models (Table 1), including key components of the cardiovascular system like cardiomyocytes^18,30 or endothelial cells^47,48. ex-Mito can arise under physiological conditions or in response to specific stimuli, and their release is driven by distinct molecular pathways depending on the biological context. Despite the diversity of experimental settings and cell types studied, consistent patterns have emerged that begin to reveal some of the regulatory principles underlying this process. In the following sections, we discuss and summarize some of the better-documented factors and cellular mechanisms that affect mitochondria release from live cells.

4.2.1. Conditions influencing mitochondria release.

A variety of conditions influence mitochondrial release, supporting the idea that this process is actively regulated. These observations are informative not only for identifying the potential regulatory pathways governing mitochondria release but also for understanding the patho-physiological roles that extracellular mitochondria play in biological processes.

Cellular and mitochondrial stress.

Cellular and mitochondrial stress are among the strongest triggers of mitochondria release across diverse cell types. Under these conditions, ex-Mito are typically damaged and can appear either as free mitochondria⁴⁶ or encapsulated in vesicles of varied size and composition^{17,18,22,26,31,39,46,60,81,82} (Table 1). Mitochondrial stress (Fig.2A) is a well-documented inducer of this process, including respiratory complex inhibition by rotenone⁴⁶ or antimycin A⁸², proton gradient-dissipation with carbonyl cyanide m-chlorophenylhydrazone (CCCP)^17,46 or -imbalance with oligomycin⁸², redox stress induction by juglone³¹ or hydrogen peroxide²², and mitochondrial DNA damage caused by ultraviolet light⁶⁰.

Figure 2. Molecular regulation of mitochondria release.

Different molecular pathways coordinate the release of mitochondria or mitochondrial material into the extracellular space. (A) Mitochondrial stress promotes mitochondrial damage, triggering quality control and release pathways. (B) Widespread mitochondrial damage activates the PINK1-Parkin pathway, leading to ubiquitination of outer mitochondrial membrane proteins. Ubiquitin-binding adaptors such as p62 recruit LC3-II-positive phagophores to damaged mitochondria. (C) Damaged mitochondria can also be targeted for autophagic removal through direct interactions with mitophagy receptors such as BNIP3 and NIX, which bind LC3-II independently of ubiquitination. (D) DRP1- and Fis1-mediated fission promotes segregation of individual mitochondria from the mitochondrial network, facilitating downstream degradation or release. (E) Fusion proteins including OMA1, OPA1, and Mitofusins (Mfn1/2) stabilize the mitochondrial network and limit mitochondrial fragmentation and release. (F) Autophagosome formation around damaged mitochondria following LC3 lipidation mediated by ATG3, ATG5, and ATG7. (G) When damage is localized, mitochondria generate mitochondrial-derived vesicles (MDVs) that are trafficked to multivesicular bodies (MVBs) and released as exosomes via Rab27-dependent fusion with the plasma membrane. (H) Pharmacological modulation of actin polymerization (e.g., phalloidin, latrunculin, CK636) significantly alters mitochondrial release. Motor proteins such as (I) MYO19, (J) MYO6, KIF5B and (K) Dynein, drive mitochondrial trafficking and extrusion through actin- and microtubule-interactions. (L) Autophagosomes containing mitochondria may fuse directly with the plasma membrane in a SNAP23-dependent manner, releasing mitochondrial contents extracellularly instead of undergoing lysosomal degradation. (M) Autophagosomes fuse with lysosomes in a Rab7-dependent process, forming phagolysosomes that degrade damaged mitochondria intracellularly limiting their release to the extracellular media. https://BioRender.com/sz1lthz.

Other forms of cellular stress that indirectly compromise mitochondrial fitness, including adrenergic signaling^18,26, cold exposure²⁶, osmotic stress⁸¹, or proteostatic imbalance^31,63, also increase the release of ex-Mito or vesicles enriched in mitochondrial components. Metabolic perturbations, particularly those affecting lipid handling and oxidative metabolism, have also emerged as potent drivers of mitochondrial ejection. In adipocytes, energetic stress induced by mitochondrial ferritin overexpression or exposure to saturated fatty acids such as palmitate leads to increased formation of mitochondria-derived vesicles and enhanced ex-Mito levels³². Consistent with this, adipocytes isolated from obese mice, where lipid overload and mitochondrial dysfunction are prominent, also display elevated release of ex-Mito^32,83. On the contrary, strategies that reduce cell and mitochondrial stress, like ROS scavenging, can reduce mitochondria release⁴⁹.

Together, this evidence supports the idea that, in some cases, mitochondria release functions as a cellular strategy to cope with overwhelming stress. However, because cells have numerous intracellular quality pathways to deal with damaged mitochondria⁸⁴, these observations raise the question of why some cells choose to eject mitochondrial material rather than degrade it intracellularly. Evidence from multiple cell types, both in vitro and in vivo, shows that lysosomal inhibition markedly increases mitochondrial secretion via EVs^26,27,32, suggesting that when intracellular quality control mechanisms are overwhelmed or limited, cells may activate alternative pathways to dispose of damaged components, including mitochondria. Supporting this notion, inhibition of the early steps of autophagosome formation has also been shown to increase mitochondrial secretion via EVs from C. elegans neurons³¹. Notably, some studies report that mild stress enhances mitochondria release, whereas excessive stress can suppress it and lead to the intracellular accumulation of damaged material^18,81. These findings highlight extracellular mitochondria release as an adaptive quality control mechanism for coping with cellular stress, while also revealing a threshold beyond which cells can no longer rely on this pathway, and proteostasis is severely compromised.

While the coexistence of intracellular and extracellular quality control mechanisms may provide evolutionary advantages in coping with cellular stress, these pathways do not seem to be entirely independent, as some key regulators governing autophagy have also been shown to influence mitochondria release (discussed below). Moreover, some studies report that enhancing intracellular quality control through autophagy activation (e.g., with rapamycin) can paradoxically lead to an increased release of mitochondria^18,47.

Despite extensive evidence linking mitochondrial stress to mitochondria release, the underlying mechanisms remain incompletely understood. Current findings suggest that mitochondrial stress may redirect damaged mitochondria toward extracellular disposal through alternative quality control pathways, bypassing their canonical degradation within the cell.

Cell activation.

In addition to stress, cellular activation is a potent trigger of ex-Mito release. Under these conditions, ex-Mito can be ejected in different forms and functional states. This has been observed in several immune and non-immune cell types, where activation-dependent signaling cascades stimulate the release of mitochondria either as free organelles or within extracellular vesicles.

In circulating immune cells, including monocytes and neutrophils, cell activation through ligand-receptor engagement has been shown to promote mitochondria release^49,50. Similarly, platelet activation in response to pro-inflammatory cytokines also induces the release of mitochondria^19,53, suggesting that activation-driven mitochondria release is a general feature of diverse cell types. Active cell migration, induced by various stimuli, can also increase mitochondrial release via vesicles known as migrasomes in a process termed mitocytosis¹⁷.

Rather than quality control, the functional consequences of mitochondria release during cell activation appear to be largely geared toward intercellular communication. These transition from serving as danger signals that amplify immune responses through engagement of pattern recognition receptors^49,50, to serving as metabolic support to recipient cells by transferring intact and functional organelles⁵³.

4.2.2. Regulatory mechanisms of mitochondria release.

Different layers of regulation contribute to the release of mitochondria from cells, beginning with their identification and selection for export, and culminating in their ejection. While the knowledge about the molecular mechanism regulating mitochondria release into the extracellular space is still very limited, we briefly summarize here some of the better-defined processes, from earlier to later steps.

Identification and targeting of mitochondria destined for release.

The identification and targeting of mitochondria for ejection represents a critical step in regulating mitochondrial release. Yet, how do cells target mitochondria for ejection, and based on what criteria? Although the mechanisms selecting functional mitochondria for release remain poorly understood, specific features of dysfunctional mitochondria, such as loss of membrane potential, exposure of inner membrane components, oxidative damage, or post-translational modifications (Table 1), may serve as signals directing them toward release. Several factors have been implicated in recognizing these damaged mitochondria for intracellular degradation pathways, and many of the same molecules seem to be also involved in marking mitochondria for extracellular release.

The role of ubiquitination in tagging mitochondria for degradation has long been recognized in intracellular quality control processes such as autophagy and mitophagy. More recently, similar mechanisms have been shown to operate in the regulation of damaged mitochondria release from cells. One well-characterized example is the PINK1/Parkin system^85,86. In compromised mitochondria, loss of membrane potential leads to the accumulation of full-length PINK1 on the outer mitochondrial membrane. Accumulated PINK1 phosphorylates substrates such as Parkin, which, upon activation by PINK1-mediated phosphorylation, ubiquitinates damaged mitochondria, marking them for degradation⁸⁵ (Fig.2B). Similar mechanisms appear to operate in the selection of mitochondria for extracellular release, although the literature is not entirely consistent. On one hand, studies have shown that loss of PINK1 or Parkin function reduces the incorporation of mitochondrial proteins into small extracellular vesicles^32,39,87, suggesting a role for the PINK1/Parkin pathway in targeting mitochondria for release. Accordingly, PINK1 overexpression increases the release of EV-encapsulated ex-Mito³⁹. Additionally, the presence of adaptors that recognize ubiquitinylated cargo, like p62/SQSTM-1⁸⁸, LC3¹⁸, or ARRDC1⁸⁹, in different EVs carrying mitochondria, together with evidence of their role in regulating vesicle formation^88,89, further supports the involvement of ubiquitination in targeting mitochondria for release. On the other hand, alternative studies report that modulation of PINK1 does not affect mitochondrial secretion in large extracellular vesicles²⁷ or that Parkin knockdown increases rather than reduces mitochondrial release⁴⁶. In the latter study, ex-Mito were found in free form, suggesting that in the absence of Parkin, cells cannot efficiently package mitochondria for lysosomal degradation or vesicle-mediated secretion, and instead release them freely⁴⁶.

The differences observed in the studies mentioned above may be explained by alternative mechanisms that mediate mitochondrial targeting for degradation, which are independent of ubiquitin and PINK1/Parkin. One such pathway is regulated by BNIP3 and NIX (Fig.2C). Under mitochondrial damage or stress, BNIP3 and NIX accumulate on the outer mitochondrial membrane and provide direct docking sites for the autophagy machinery through their interaction with LC3, thereby bypassing the requirement for ubiquitination⁹⁰. Notably, overexpression of BNIP3 or NIX decreases the release of extracellular mitochondria⁴⁶, while NIX knockout increases the secretion of EV-encapsulated mitochondria following UVB irradiation⁶⁰. These findings suggest that BNIP3 and NIX are primarily involved in directing mitochondria toward intracellular degradation, thus limiting the extracellular release of mitochondria.

Together, these data indicate that mechanisms targeting mitochondria for degradation can directly or indirectly influence their release. Pathways involving ubiquitin tagging may generate substrates that are subsequently sorted for either extracellular release or intracellular degradation. In contrast, pathways such as those regulated by BNIP3 and NIX appear to reduce mitochondrial release by directing damaged mitochondria specifically toward digestion inside the cell.

Isolation of mitochondria destined for release.

In some cells, mitochondria destined for release must undergo isolation to ensure their selective export once targeted. This requirement stems from the fact that, in most cell types, mitochondria exist as a dynamic network rather than a collection of isolated organelles⁹¹.

Mitochondrial fission and fusion play critical roles in this regard, allowing the mitochondrial network to preserve functionality under various metabolic or environmental stresses⁹². Specifically, mitochondrial fission (Fig.2D) enables the isolation of compromised mitochondria or mitochondrial fragments, facilitating their removal. This process is regulated by several proteins, including DRP1 and FIS1. Notably, Drp1 knockdown has been shown to reduce the release of EV-encapsulated mitochondria from various cells and organisms^17,93, while in other contexts, its inhibition produces minimal effects^26,63. Fis1 overexpression in mature osteoblasts promotes the secretion of EV-encapsulated mitochondria through increased mitochondrial fragmentation, a process regulated by CD38/cADPR/calcium signaling²⁹. Similarly, activation of CD38/cADPR/calcium pathway triggers the release of mitochondria in astrocytes²⁵ and MSCs⁶² in both free and EV-encapsulated forms. Together, these studies support a role for mitochondrial fission in isolating mitochondria and their components to favor extracellular release.

The role of mitochondrial fusion (Fig.2E) regulators in mitochondrial release is less clear. In C. elegans, overexpression of Fzo-1, the homolog of Mitofusin (Mfn1/2), reduces the production of mitochondria-containing vesicles in neurons, whereas mutations that impair its fusion-inducing activity increase vesicle formation⁹³. Similarly, knockdown of another positive regulator of mitochondrial fusion, OPA1, enhances the secretion of mitochondria in both free and EV-encapsulated forms in mature osteoblasts²⁹. In cardiomyocytes, EV-encapsulated mitochondria display reduced levels of both OPA1 and FIS1. In these cells, loss of OMA1, the protease that processes OPA1 and negatively regulates mitochondrial fusion, diminishes stress-induced mitochondrial ejection¹⁸. Together, these findings suggest that positive regulators of mitochondrial fusion inhibit mitochondrial release, while negative regulators of mitochondrial fusion promote it. However, the deletion of OPA1 in mouse embryonic fibroblasts (MEFs) has been shown to reduce rather than increase mitochondria secretion⁹⁴.

These findings indicate that fission and fusion processes work in concert to regulate the isolation of mitochondria marked for release. Generally, fission favors the segregation and packaging of mitochondrial material, whereas fusion maintains mitochondria network cohesion and limits release. The divergent outcomes observed across cell types suggest that mitochondrial isolation need for release is context-dependent and likely shaped by the cellular conditions and signals that trigger this process.

Compartmentalization of mitochondria destined for release.

In some cases, mitochondria or mitochondria-derived components are compartmentalized in membrane-enclosed particles before or during their release at the plasma membrane. Multiple pathways involving mitochondrial compartmentalization have been proposed to contribute to their extracellular export, with autophagy and exosomes being the two that have been studied in more detail.

Autophagy is a cellular process in which cytoplasmic material is sequestered into double-membrane vesicles and delivered to lysosomes for degradation and recycling. In the context of mitochondria, bulk (macroautophagy) or mitochondria-selective (mitophagy) autophagy eliminate damaged organelles, preserving mitochondrial quality and cellular homeostasis⁸⁴. Importantly, several studies have uncovered strong links between autophagy and mitochondria release (Fig.2F). For instance, induction of autophagy with rapamycin, an mTOR inhibitor, enhances the secretion of mitochondria-enriched vesicles from cardiomyocytes¹⁸ and endothelial cells (ECs)⁴⁷. Additionally, deletion of the autophagy-related gene ATG7 impairs the release of mitochondria-containing vesicles in cardiac and muscle cells^18,22, suggesting that canonical autophagy machinery contributes to the formation or trafficking of mitochondria destined for secretion. Alternatively, other works propose that some EV-encapsulated ex-Mito may arise through a switch from degradative to secretory autophagy. Supporting this view, cells treated with mitochondrial depolarizing agents in the absence of mATG8-conjugation machinery components (ATG3, ATG5, ATG7) still recruit early autophagy factors to damaged mitochondria, but the resulting vesicles fuse with the plasma membrane rather than with lysosomes. Conversely, deletion of genes required for autophagosome biogenesis upstream of the mATG8-conjugation system reduces mitochondria encapsulation and clearance⁸². Despite these findings, the role of autophagy in mitochondria release is neither universal nor easy to interpret. In some settings, deletion of ATG5 or ATG7 has little or no effect on ex-Mito secretion^39,47,89, and in HeLa cells, knockout of multiple autophagy genes, including early-acting ones, even increases mitochondrial release⁴⁶.

Exosomes have been proposed to contribute to the pool of ex-Mito in certain contexts (Fig.2G). Exosomes are small EVs formed when late endosomes, or multivesicular bodies (MVBs), fuse with the plasma membrane, releasing their intraluminal vesicles as cargo. Supporting a role for exosomes in ex-Mito production, some EV-encapsulated ex-Mito have been shown to co-localize with canonical exosome markers such as ALIX, CD63, and CD92^27,32, and inhibition of exosome formation with GW4869 reduces the formation of EV-encapsulated ex-Mito^27,32. However, similar to autophagy, this contribution appears to be cell type- or context-dependent, as some studies have shown that blocking exosome biogenesis is not required for ex-Mito formation in other settings³¹. Mitochondrial components can reach MVBs in the form of mitochondria-derived vesicles (MDVs), small vesicles that bud directly from stressed mitochondria to remove damaged components. MDVs are frequently generated in response to oxidative stress³², and their formation is enhanced under conditions of increased mitochondrial fragmentation, such as Fis1 overexpression or Opa1 deficiency²⁹. Once formed, MDVs are typically routed to MVBs for lysosomal degradation; however, not all MDVs follow this degradative route. Some MDVs can be released extracellularly via EVs, including exosomes, after MVB fusion with the plasma membrane, and this release is enhanced by lysosomal inhibition^27,32.

Taken together, these observations indicate that autophagy and MDVs contribute to the selective release of mitochondria via extracellular vesicles. However, their roles are highly cell type- and context-dependent, suggesting that multiple pathways can mediate ex-Mito secretion. Additionally, since intracellular quality control and extracellular export mechanisms may compete for the same cargo, such as damaged mitochondria, some of the results discussed here could reflect indirect effects of cargo re-routing rather than a direct involvement of these pathways in mitochondrial export.

Transport of mitochondria targeted for release.

Regardless of the mode in which mitochondria are released, or the intermediate steps involved, their relocation from the cytoplasm to the extracellular space involves transport mechanisms. How are mitochondria transported toward the plasma membrane for final ejection? Both the cytoskeleton and cytoskeleton-associated molecules have been shown to play active roles in this process.

The actin cytoskeleton is a key regulator of mitochondrial release. In C. elegans spermatids, inhibition of actin polymerization using latrunculin A or CK-636 reduces the release of EV-encapsulated mitochondria, whereas stabilization of filamentous actin with phalloidin significantly enhances this process⁶⁴ (Fig.2H). Similar effects are observed in platelets, where disruption of actin polymerization markedly decreases the number of free and EV-encapsulated ex-Mito¹⁹. Supporting this role, several actin-associated motor proteins regulate the extracellular release of mitochondria. For instance, Spe-15 (the C. elegans homolog of myosin VI) inhibits mitochondrial release from spermatids by moving mitochondria toward the minus-end of actin filaments⁶⁴ (Fig.2I). Additionally, Myosin19 (MYO19) tethers dysfunctional mitochondria at the trailing edge of migrating cells, facilitating their packaging into EVs¹⁷ (Fig.2J).

Microtubules also contribute to mitochondria release, primarily serving as tracks for motor proteins that transport mitochondria toward the cell periphery. MIRO-1 (encoded by Rhot1), a key mitochondrial transport protein, drives mitochondrial movement along microtubules toward the plasma membrane, and its knockdown reduces mitochondria release from both osteocytes⁹⁵ and astrocytes⁹⁶. In migrating neutrophils, KIF5B selectively binds damaged mitochondria and transports them outward along microtubules for release in EVs¹⁷. Dynein, in contrast, opposes KIF5B by transporting mitochondria inward toward the cell center, and its knockdown further enhances mitochondrial release in EVs¹⁷ (Fig.2K).

Overall, mitochondrial ejection is a highly regulated process that relies on coordinated transport along the cytoskeleton. Both actin filaments and microtubules, together with their associated motor proteins, control the positioning and trafficking of mitochondria (or mitochondria-containing vesicles) to the cell periphery, ensuring their efficient packaging and release. Understanding these transport mechanisms provides critical insight into how cells regulate mitochondria release.

Membrane fusion events leading to mitochondrial release.

In cases where mitochondria are compartmentalized within intracellular vesicles prior to their release from live cells, such as in autophagosomes or exosomes, fusion of these vesicles with the plasma membrane may be a necessary step for extracellular release. Consistent with this, the disruption of molecules that mediate vesicle plasma membrane fusion markedly reduces mitochondrial secretion. For example, knockout of SNAP23, a SNARE protein that mediates autophagosome fusion with the plasma membrane (Fig.2L), decreases mitochondrial release into the extracellular space in HeLa cells⁸². Similarly, knockdown of Rab27, a small GTPase that regulates the fusion of multivesicular bodies with the plasma membrane to release exosomes (Fig.2G), reduces the secretion of small EVs containing mtDNA³⁹.

Interestingly, deletion of Rab7, which normally mediates autophagosome-lysosome fusion (Fig.2M), leads to increased production of large EVs containing mitochondrial proteins. Mechanistically, in Rab7-deficient cells, mitochondria remain enclosed within intracellular vesicles that are unable to fuse with lysosomes and are instead rerouted toward the plasma membrane²⁷.

Together, these findings highlight the critical role of membrane fusion regulators in controlling the release of mitochondria versus intracellular degradation.

5). Patho-physiological roles of extracellular mitochondria

ex-Mito are present under both physiological and pathological conditions. The diverse contexts and mechanisms underlying mitochondrial release provide valuable insights into their potential functional significance, both for the cells that secrete mitochondria and for the cells that interact with or incorporate this material. In the following sections, we examine the key functional roles of ex-Mito across diverse biological contexts to gain insight into their evolutionary origins and how they contribute to tissue patho-physiology. This broad perspective is essential for understanding the multifaceted roles and patho-physiological relevance of ex-Mito, setting the stage for a more detailed discussion of their specific functions within cardiovascular patho-physiology in the next section.

5.1. Quality control: outsourcing mitochondrial degradation

To maintain proteostasis and optimal cellular function over time, cells employ a robust network of quality control mechanisms that monitor the integrity and performance of various cellular components, including mitochondria. Traditionally, mitochondrial quality control has been considered an intrinsic, cell-autonomous process, exemplified by pathways such as proteasomal degradation, autophagy, and mitophagy⁹⁷. However, recent studies have revealed an alternative strategy in which mitochondrial quality is regulated through the selective release of damaged mitochondria (Fig.3A).

Figure 3. Patho-physiological significance of mitochondrial release.

Cells can release mitochondria under both stress and homeostatic conditions. The released organelles can be either functional or damaged, resulting in distinct outcomes depending on the physiological context and the identity of both the releasing and recipient cells. (A) Damaged mitochondria can be extruded as part of a quality control mechanism, enabling their recognition and clearance by supporting phagocytes. (B) Some cells actively expel mitochondria to reduce their mitochondrial content during differentiation or (C) to preserve stemness. (D) When mitochondria or their components (e.g., mtDNA) are released into the extracellular space, they act as damage-associated molecular patterns (DAMPs) that engage pattern recognition receptors (e.g., TLRs) on immune cells, inducing inflammatory cytokine production and systemic inflammation. (E) In certain settings, healthy mitochondria are transferred to neighboring cells, enhancing their oxidative phosphorylation (OXPHOS) capacity and promoting recovery or tissue repair. (F) Extracellular mitochondria can also enter the circulation, where they influence endothelial and immune cell function or exert effects on distant tissues. Overall, mitochondrial release represents a multifaceted process with context-dependent consequences, ranging from metabolic support and maintenance of stemness to activation of immune and inflammatory responses. https://BioRender.com/arjyv7m.

The release of damaged mitochondria as a quality control strategy to adapt to stress was first recognized in vitro, where cells exposed to uncouplers of oxidative phosphorylation expelled damaged mitochondria in order to survive under stress conditions⁹⁸. In vivo, one of the first demonstrations of mitochondria release for quality control was provided by a study showing that retinal ganglion cells in the optic nerve extrude mitochondria for degradation by the lysosomes of neighboring astrocytes⁴⁵. Since this initial discovery, multiple studies have documented examples of damaged mitochondria extrusion across organisms and tissues, including C. elegans touch neurons³¹, zebrafish cone photoreceptors²⁸, mouse and human cardiomyocytes^18,27,30, or mouse brown adipocytes²⁶. In these cases, the presence of damaged traits in the released mitochondria (summarized in Table 1), coupled with their capture and degradation by local populations of phagocytic cells, underscores their function as bona fide quality control mechanisms.

The quality control mechanism described above has been referred to as transmitophagy^28,45 when focusing specifically on the transfer of mitochondria in isolation, or heterophagy⁹⁹ when encompassing the transcellular transfer of damaged mitochondria along with other cellular cargo. Both processes highlight the heterologous, transcellular nature of this alternative quality control pathway. These pathways are critical for tissue physiology, as their inhibition leads to the accumulation of damaged mitochondria within mitochondria-secretory cells and consequent tissue dysfunction, including deterioration of heart function¹⁸ and impaired thermogenesis²⁶. Notably, cells that employ these strategies to dispose of their damaged mitochondria often share characteristics such as high energetic demand, intense mitochondrial activity, long lifespan, high specialization, and strong subcellular compartmentalization. Such features, discussed in more detail in this review⁹⁹, likely contribute to the need for alternative strategies to complement intracellular degradation pathways.

Another mechanism of mitochondrial quality control is mitocytosis, in which migrating cells dispose of damaged mitochondria via migrasomes, vesicular structures formed at retraction fibers and released into the extracellular milieu^17,100. Mitocytosis provides an additional route for selective mitochondrial clearance in highly dynamic or polarized cells, further expanding the diversity of strategies for maintaining mitochondrial health.

Altogether, these findings reinforce the importance of extracellular mitochondrial release as a complementary quality control mechanism. By outsourcing the degradation of damaged mitochondria to neighboring cells or extracellular structures, cells can maintain homeostasis under conditions of high cellular stress, ensuring both mitochondrial fitness and overall tissue function. This process reflects a broader principle in cellular organization: when intrinsic, cell-autonomous mechanisms are insufficient or constrained, cells can leverage their environment and intercellular interactions to preserve fitness and function.

5.2. Cell identity: reducing mitochondrial content

Mitochondria elimination serves not only quality control purposes. In some cases, cells may need to reduce their mitochondrial abundance and activity to support specific cellular states. This regulation is essential for processes such as cell activation (discussed above), cellular maturation, and the maintenance of stemness.

In C. elegans, sperm maturation involves the selective elimination of mitochondria as spermatids transition into motile, transcriptionally inactive sperm. Excess or damaged mitochondria are extruded into small vesicles and degraded by neighboring cells, ensuring that mature sperm retain only the mitochondria needed for motility and fertilization⁶⁴. Similarly, during erythropoiesis, reticulocytes actively reduce their mitochondrial content before maturing into organelle-free red blood cells (Fig.3B). In this case, mitochondria from differentiating erythrocytes are packaged into vesicles or autophagosomes and released for degradation by macrophages, optimizing oxygen transport, cell deformability, and overall homeostasis^54–56.

Stem cells also regulate their mitochondrial pool to preserve stemness and prevent premature differentiation (Fig.3C). Because oxidative stress and ROS can trigger differentiation or senescence, stem cells maintain a low mitochondrial load and a glycolytic profile by reducing mitochondrial content¹⁰¹. Notably, mesenchymal stem cells (MSCs) have been shown to release mitochondria in free or EV-encapsulated form that are subsequently engulfed and degraded by macrophages. This transcellular quality control mechanism allows MSCs to sustain their metabolic fitness and differentiation potential⁶¹.

Taken together, these observations suggest that mitochondria release can serve as a strategic process to reconfigure metabolic states, preserve specialized functions, and ensure tissue-level homeostasis. Investigating whether other cell types that actively reduce their mitochondrial content also employ mitochondrial extrusion may reveal additional, yet unrecognized, roles for this process in cellular differentiation, tissue specialization, and organismal physiology.

5.3. Signaling: ex-Mito as inflammatory modulators

Given their prokaryotic origin⁹, many mitochondria-derived components including mitochondrial DNA (mtDNA), N-formyl peptides, and cardiolipin, are potent activators of inflammation and innate immune responses when exposed extracellularly¹². Upon intra- or extracellular recognition, these molecules act as danger-associated molecular patterns (DAMPs), activating Toll-Like Receptors (TLRs) and triggering downstream signaling pathways that promote inflammatory responses^13,14 (Fig.3D). Additionally, capture of ex-Mito by other cells may affect their production of inflammatory mediators. Thus, in some contexts, cells may actively eject mitochondria to alert neighboring cells of stress or damage, or to modulate their production of inflammatory mediators, contributing to immunomodulation.

Among mitochondria-derived DAMPs, mtDNA is particularly potent. Extracellular mtDNA is recognized by endosomal TLR9, initiating a cascade in which engagement of MyD88 activates IRF7, which translocates to the nucleus to drive transcription of type I interferons (IFNs). Secreted IFNs then act in autocrine and paracrine manners to coordinate immunomodulatory programs¹⁴. ex-Mito have been shown to induce pro-inflammatory responses in both immune and non-immune cells. While these have been reviewed elsewhere¹⁴, some examples include ex-Mito released from activated monocytes stimulating type I IFN and TNF responses in ECs⁴⁹, neutrophil extracellular traps (NETs) rich in oxidized mtDNA activating IFN responses in monocytes⁴⁰, and plasmacytoid dendritic cells exposed to oxidized mtDNA producing robust IFN-α and upregulating inflammatory genes⁴¹. Tissue injury¹⁰² and many other conditions (discussed below) can lead to the release of large amounts of ex-Mito in tissues and into the circulation. Importantly, chronic exposure to ex-Mito can drive the production of autoantibodies against mitochondrial components, further amplifying their immunogenicity by engaging adaptive immune responses, as observed in systemic lupus erythematosus¹⁰³, autism³⁶, or heart disease¹⁰⁴. Further, circulating levels of mitochondria-derived components in blood are highly associated with poor prognosis and mortality in several disease conditions, including COVID-19¹⁰⁵, sepsis¹⁰⁶, or aging¹⁰⁷. Thus, extracellular mitochondria may serve to initiate or amplify inflammatory signaling.

While previous data support a role for ex-Mito as potent inducers of inflammation, evidence also indicates that they can exert anti-inflammatory effects in certain contexts. For example, mesenchymal stromal cell-derived EV-encapsulated mitochondria have been shown to inhibit NET formation in liver-infiltrating neutrophils after ischemia-reperfusion injury¹⁰⁸, and they promote an anti-inflammatory, highly phagocytic phenotype in macrophages cultured in vitro^109,110. These findings indicate that not all ex-Mito are necessarily proinflammatory and that their immunomodulatory properties may depend on the form in which they are presented (e.g., free versus EV-encapsulated). In this context, free ex-Mito, but not those encapsulated in extracellular vesicles, induce strong inflammatory responses in macrophages⁹⁴.

Collectively, these findings emphasize that ex-Mito can function as an active signaling mechanism to modulate immunity. Elucidating how ex-Mito influence both innate and adaptive immune responses may provide critical insights into the initiation and perpetuation of inflammatory and autoimmune diseases and could inform novel therapeutic strategies to treat these pathologies.

5.4. Support: ex-Mito to enhance function of acceptor cells

Given their central roles in provision of energetic molecules and metabolic regulation, the transfer of mitochondria between cells has been proposed as a mechanism to modulate and sustain the metabolism of recipient cells. This concept has attracted increasing attention and has become an active area of investigation in recent years. Several studies (thoroughly and recently reviewed in¹¹¹) provide substantial evidence supporting this possibility, showing that uptake or exposure to exogenous mitochondria can modify the metabolic activity of multiple cell types^25,33,34. These findings have strengthened the concept of mitochondrial transplantation, in which foreign mitochondria, whether present in the extracellular environment or transferred directly between cells, may integrate into the recipient mitochondrial network and enhance its metabolic function (Fig.3E). However, several interpretations of these findings remain possible, and not all reported cases of mitochondrial transfer, either physiological or therapy-induced, necessarily involve an extracellular phase.

In many experimental settings showing transfer of functional mitochondria, the route by which mitochondria move between cells remains unclear. It is often uncertain whether mitochondria are truly extracellular at any point or are exchanged directly between cells through alternative mechanisms such as tunneling nanotubes (TNTs). TNTs are thin, actin-based membrane projections that form direct cytoplasmic bridges between cells, facilitating the exchange of cytoplasmic material and organelles, including mitochondria^112–116. Because mitochondrial transfer through TNTs does not involve an extracellular intermediate, these events will not be further discussed here, and the following discussion will focus on evidence supporting a role for ex-Mito.

As previously discussed, a broad spectrum of extracellular mitochondria exhibiting varying functional capacities has been reported in several physiological and pathological contexts (see Table 1). These findings suggest that mitochondria with different levels of functionality can be released or secreted into the extracellular environment, where they may be taken up by neighboring cells and potentially incorporated into their mitochondrial compartment to enhance their respiratory activity. Supporting this view, in vitro studies have shown that ex-Mito can be delivered into recipient cells^62,117–119, resulting in measurable changes in their metabolic activity^62,117,118. Similarly, in vivo studies have also demonstrated that systemic delivery of mitochondria can partially restore mitochondrial function in stressed cells^62,120, and alleviate tissue dysfunction in animals with pathological mitochondrial mutations⁶². Supporting the relevance of this phenomenon in patho-physiological conditions, mitochondrial transfer has been observed in several specific contexts, including the movement of mitochondria from adipocytes to cardiomyocytes in obesity³², and from astrocytes to neurons in stroke²⁵, both involving ex-Mito forms.

While these findings support a functional role for mitochondria transfer in regulating metabolic activity, the mechanisms underlying these effects remain to be fully defined. Most studies attribute the metabolic benefits observed in recipient cells to the integration of exogenous mitochondria into their endogenous mitochondrial network. However, direct evidence for stable incorporation and sustained contribution of donor-derived mitochondria to host mitochondrial respiration remains limited. Other studies indicate that internalized mitochondria may influence recipient cell metabolism primarily through their degradation rather than by functioning as intact organelles in the recipient cells¹¹⁶. This possibility indicates that the beneficial effects of mitochondrial transfer may not exclusively depend on the functional integration of those organelles within the recipient cell mitochondrial network.

In summary, mitochondrial transfer can influence the metabolic activity of recipient cells, but the underlying mechanisms remain incompletely understood. Key questions include whether the metabolic improvements arise from the functional incorporation of exogenous mitochondria or from the utilization of metabolites derived from their degradation, and whether additional components within the transferred cargo contribute to these effects.

5.5. Regulation of distal cells and tissues

Although most examples of ex-Mito discussed above act locally, the detection of distinct ex-Mito populations in circulation suggests a broader role as inter-organ communicators with potential impact on organismal health (Fig.3F). Circulating ex-Mito have been identified in both healthy humans and mice⁴⁸, and their abundance often increases under pathological conditions such as COVID-19¹⁰⁵, sepsis¹⁰⁶, or aging¹⁰⁷. While blood cells and ECs release ex-Mito into circulation (discussed below), other cell types not normally found in the bloodstream can also contribute to the circulating ex-Mito pool under specific contexts. For instance, in obesity, white adipocytes release ex-Mito into circulation^32,65, eliciting an antioxidant response in the heart³². Similarly, endothelial cells shed ex-Mito that are captured and cleared by splenic macrophages, though the consequences of this process for the receiving cells remain unclear⁴⁷.

In smaller organisms such as C. elegans, ex-Mito have also been shown to travel throughout the body. Neurons, for example, release EVs containing damaged mitochondria into the pseudocoelomic fluid, where they are ultimately taken up and degraded by coelomocytes³¹. Additionally, body wall muscle cells release mitochondria and nutrient-rich vesicles that are delivered to the gonads and incorporated by oocytes, providing metabolic support and enhancing reproductive capacity²².

Together, these findings highlight the ability of ex-Mito to circulate and act on distant targets, thereby influencing systemic physiology. Whether circulating ex-Mito display selective tropism for particular tissues or niches, however, remains an open question.

6). Extracellular mitochondria in cardiovascular patho-physiology

Extracellular mitochondria have emerged as important mediators in cardiovascular patho-physiology, functioning at the intersection of cellular homeostasis, immunity, and stress responses. Their release serves multiple functions, ranging from intracellular quality control to active intercellular signaling. Depending on their origin and functional state, ex-Mito can either exacerbate pathology by promoting inflammation through mitochondrial DAMPs or support tissue homeostasis by facilitating the clearance of damaged organelles and transferring bioenergetic capacity to recipient cells. A detailed understanding of ex-Mito dynamics may uncover novel biomarkers and therapeutic strategies to limit cardiovascular disease progression and improve clinical outcomes. In this section, we review several well-characterized examples and their implications for cardiovascular health and disease.

6.1. Ejection of damaged mitochondria from cardiomyocytes as a quality control mechanism

Cardiomyocytes, the contractile muscle cells responsible for driving the heartbeat, experience continuous mitochondrial damage due to their exceptionally high oxidative metabolism¹²¹. In addition to canonical mitochondrial quality-control pathways such as autophagy, recent mouse models enabling fluorescent tracking of these organelles have revealed that cardiomyocytes can expel mitochondria in large EVs that often contain multiple organelles^18,27,30. In addition, TEM has allowed observation of similar vesicles in human myocardial tissue¹⁸, supporting the physiological relevance of this process in humans.

It is important to note that although mitochondrial ejection from cardiomyocytes occurs under basal conditions, this process is markedly amplified by diverse stimuli including autophagy activation with rapamycin¹⁸, beta-adrenergic stimulation with isoproterenol¹⁸, myocardial infarction¹⁸, sepsis³⁰ and lysosomal inhibition²⁷, indicating that mitochondrial release may function as a stress-responsive adaptation. The involvement of molecules such as Rab7²⁷ or ATG7¹⁸ in EV-mediated mitochondrial export further supports the idea that this is an active, tightly controlled pathway, and highlights the potential for pharmacological strategies aimed at modulating this process to facilitate heart adaptation to stress or pathological contexts.

Exported mitochondria display hallmarks of structural and functional impairment, including disrupted cristae and inner/outer membranes, low membrane potential, lack of response to hyperpolarizing agents, reduced citrate synthase activity, and altered proteomic profiles^18,30. Once released, these large, mitochondria-containing EVs are captured and degraded by specialized, tissue-resident cardiac macrophages^18,27,30. This disposal route is critical for myocardial homeostasis: depletion of macrophages specialized in engulfing these vesicles or inhibition of their phagocytic functions leads to their extracellular accumulation, followed by progressive buildup of damaged mitochondria within cardiomyocytes and in the extracellular space, triggering inflammation, impairing cardiac performance¹⁸, and increasing susceptibility to arrhythmias¹²².

Collectively, these findings indicate that the ejection of damaged mitochondria within EVs represents an alternative and complementary quality-control route in cardiomyocytes, functioning in tight coordination with resident macrophages to maintain mitochondrial integrity, cellular homeostasis, and overall heart function. However, several important questions remain unresolved. How this extrusion pathway coordinates with other mitochondrial quality-control mechanisms operating in cardiomyocytes, such as autophagy and mitophagy^123–125, is still unclear. The molecular machinery that mediates mitochondrial packaging and export in cardiomyocytes also remains to be defined, including the signals that trigger extrusion and the vesicle-sorting components involved. It is likewise unknown whether enhancing mitochondrial release during stress conditions could improve cardiomyocyte fitness, reduce intracellular accumulation of damaged organelles, or ultimately support better cardiac performance. Addressing these open questions will be essential to understand the full physiological significance of this pathway and its potential therapeutic relevance.

6.2. Ejection of mitochondria from maturing erythrocytes as a maturation mechanism

Erythrocytes, or red blood cells, are responsible for transporting oxygen and carbon dioxide throughout the circulation. In mammals, mature erythrocytes adopt a biconcave shape and lack nuclei, organelles, and proteins unnecessary for their primary functions, including mitochondria. Consequently, mitochondria must be selectively eliminated during the transition from erythroid precursors (reticulocytes) to mature erythrocytes.

The mechanisms underlying mitochondrial clearance in reticulocytes remain incompletely understood and are the subject of ongoing investigation. Genetic studies have identified key mediators of mitophagy, such as the cargo receptor NIX/BNIP3L¹²⁶ and the autophagy protein ATG7¹²⁷, supporting the view that most mitochondria are degraded intracellularly within reticulocytes. However, evidence from classic ultrastructural studies⁵⁵, along with more recent observations^54,56, indicates that mitochondria can also be released extracellularly during reticulocyte maturation. Indeed, mitochondria or mitochondrial components have been detected within both small^54,55 and large⁵⁶ EVs produced by these cells, suggesting that vesicular export may complement mitophagy in maturing reticulocytes as an alternative route of mitochondrial disposal.

Efficient mitochondrial removal is essential for the production of fully mature erythrocytes. Failure to clear mitochondria compromises red cell deformability, increases oxidative stress, and promotes exposure of procoagulant signals, thereby impairing hemocompatibility and cardiovascular health¹²⁸. Thus, mitochondrial elimination, whether via intracellular degradation or extracellular release, is a critical process in erythrocyte maturation, ensuring the optimal function and lifespan of these cells and, by extension, supporting oxygen delivery and cardiovascular homeostasis in large organisms.

6.3. Platelet release of mitochondria into circulation

Platelets are small, anucleate cell fragments derived from megakaryocytes that circulate in the blood, where they play a central role in hemostasis by detecting vascular injury and promoting clot formation. Platelets are not exactly cells but rather fragments produced by megakaryocytes through the release of long, microtubule-lined proplatelets into circulation.

Upon activation, such as by thrombin, collagen, or during storage/processing of platelet concentrates, platelets externalize mitochondria either as free organelles or enclosed within EVs¹⁹. The functional state of these platelet-derived ex-Mito is debated: two studies from the same group report that ex-Mito released from activated platelets are respiratory competent and contain the machinery required for ATP generation^19,52, whereas an independent study concluded the opposite⁵¹.

In healthy conditions, circulating vesicles containing mitochondria can display platelet surface markers (e.g., CD41)^48,52, indicating that platelets contribute substantially to the circulating ex-Mito pool alongside other sources such as ECs and leukocytes (discussed below). Alternatively, platelet markers may arise from the attachment of non-platelet ex-Mito to platelets in circulation, a phenomenon observed in other contexts¹²⁹. Functionally, platelet-derived ex-Mito have been linked to adverse transfusion reactions^19,130, suggesting a role in inflammatory signaling. Mechanistically, they can serve as endogenous substrates for phospholipase A₂ IIA, leading to the release of pro-inflammatory mediators and EC activation that promote leukocyte recruitment¹⁹. They can also be incorporated by leukocytes, including neutrophils and monocytes, to enhance mitochondrial function⁵². Notably, this latter effect appears to require functional donor mitochondria, as pre-treatment of platelet-derived ex-Mito with antimycin A (a mitochondrial electron transport chain inhibitor) abolished the enhancement of leukocyte mitochondrial activity⁵². Additionally, mitochondria released by platelets can stimulate pro-angiogenic properties of MSCs to enhance their pro-reparative functions in wound healing⁵³.

Collectively, these findings suggest that platelet-derived ex-Mito are not merely byproducts of activation but can actively modulate systemic inflammatory responses, with potential implications for cardiovascular and immune patho-physiology.

6.4. Endothelial cell release of mitochondria into circulation

Endothelial cells, which line the entire vascular network and serve as critical regulators of circulation, are an important source of ex-Mito. Most endothelial cell-derived ex-Mito released in the absence of necrosis are reported to be enclosed within EVs, and intravital microscopy has directly visualized these events in vivo⁴⁷. Following release, EV-encapsulated ex-Mito released by ECs expose “eat-me” signals such as phosphatidylserine, which facilitates their engulfment by multiple immune cell populations in the circulation and peripheral tissues⁴⁷.

In both humans and mice, circulating mitochondria-positive microparticles also display endothelial markers (e.g., CD144), supporting the contribution of ECs to the ex-Mito pool in blood⁴⁸. Clinically, numerous studies have shown that endothelial cell-derived EVs are elevated in cardiovascular disease (CVD) conditions, including acute coronary syndromes^131,132, hypertension^133,134, diabetes¹³⁵, and heart failure¹³⁶. Although most of these studies did not specifically assess mitochondrial cargo, one report demonstrated that endothelial stress induced by acute myeloid leukemia-driven vascular remodeling leads to an increase in mitochondria-containing vesicles⁴⁷.

Together, these findings suggest that EC-derived EVs containing mitochondria may serve as candidate biomarkers of vascular stress and cardiovascular disease progression. In addition, they are likely to act as paracrine mediators that influence leukocyte function, although the precise consequences of this crosstalk remain to be defined.

6.5. Leukocyte release of mitochondria into circulation

Leukocytes, the cellular components of the immune system, are abundant in circulation and represent an important source of ex-Mito. These cells can export mitochondrial material into the bloodstream in the form of intact organelles, mitochondrial fragments, or derived molecules, with distinct biological functions.

Upon stimulation, viable neutrophils can externalize mtDNA to form NETs, which entrap and kill pathogens⁵⁰ while simultaneously contributing to the circulating ex-Mito pool¹³⁷, and activating IFN responses in monocytes⁴⁰. A similar mtDNA-based trap formation has been reported in eosinophils, although their overall contribution to circulating ex-Mito remains less well defined¹³⁸. In addition, activated monocytes release intact mitochondria both as free organelles and packaged within EVs⁴⁹. These mitochondria are not inert: they can induce type I IFN and TNF responses in ECs⁴⁹.

Together, these findings suggest that the release of both free and EV-enclosed mitochondria is a characteristic feature of leukocyte activation. This process may have evolved as a host defense mechanism, acting as a potent mediator of vascular inflammation in response to bacterial-like components present in mitochondria and connecting immune activation to cardiovascular patho-physiology.

6.6. Cell death-mediated release of ex-Mito in cardiovascular disease

As previously discussed in this review, cell death can lead to the production of different forms of ex-Mito in various settings^16,77–80 and those contain bacterial-like components that act as DAMPs. These molecules engage innate sensors such as TLR9, cGA-STING, and NLRP3 in vascular and immune cells, linking tissue injury to sterile inflammation¹⁰² and secondary pathological events¹³⁹.

This mechanism is relevant across many cardiovascular diseases. In myocardial infarction, necrotic cardiomyocytes release mtDNA and mitochondrial fragments into the interstitium and circulation, amplifying inflammation and contributing to adverse remodeling^73–76. Similarly, in stroke, necrotic cells increase the extracellular presence of mtDNA⁷², while in atherosclerosis, necrotic foam cells, stressed ECs, and vascular smooth muscle cells release ex-Mito that activate innate immune sensors and accelerate plaque progression^69,70. Moreover, in infections and trauma, cellular necrosis likewise liberates mtDNA and mitochondrial fragments, promoting systemic inflammation¹⁴⁰.

Together, these findings highlight ex-Mito as a common feature of necrosis-associated cardiovascular diseases, serving as potent inflammatory mediators. Therapeutic strategies aimed at reducing mito-DAMP production, inhibiting their sensing, or enhancing their clearance may mitigate disease progression. In addition, circulating ex-Mito may serve as valuable biomarkers of disease activity and cardiovascular risk.

6.7. Transfer of mitochondria to stressed cells to improve performance in cardiovascular patho-physiology

Mitochondrial transfer between cells has emerged as a novel mechanism by which stressed or damaged cells can acquire functional mitochondria from donor cells, thereby restoring bioenergetic capacity and supporting tissue homeostasis. In the cardiovascular system, this process has been implicated in diverse patho-physiological contexts and may occur through different routes: either via extracellular release of mitochondria, in free form or encapsulated within EVs^25,32,34,141, or through direct cell-cell contact mediated by TNTs^116,142.

Evidence for mitochondrial transfer between cells has been observed in different patho-physiological situations related to the cardiovascular system. For instance, astrocytes have been shown to donate mitochondria to neurons after stroke, promoting neuronal survival and functional recovery²⁵. In metabolic stress during obesity or high-fat diet exposure, adipocytes release mitochondria which are taken up by cardiomyocytes^32,65. Interestingly, rather than exacerbating injury, this transfer activates an adaptive oxidative stress response that ultimately protects the heart against ischemia/reperfusion injury in mice³². Following this concept, several studies have attempted to deliver mitochondria to stressed cells by either injecting donor cells or isolated mitochondria. For example, induced pluripotent stem cell (iPSC)-derived MSCs injected into mice have been proposed to transfer mitochondria to stressed cardiomyocytes, thereby improving their bioenergetics and reducing oxidative stress¹⁴². Similarly, bone marrow stromal cells have been reported to donate mitochondria to alveolar epithelial cells in mice, protecting them against acute lung injury³⁴. An alternative strategy involves the direct injection of isolated mitochondria into recipient organisms. For instance, intravenous administration of mitochondria derived from femoral artery smooth muscle cells attenuated chronic hypoxia-induced pulmonary vascular remodeling in a mouse model of hypoxic pulmonary hypertension¹⁴³. Likewise, injection of brain endothelial cell-derived EVs containing mitochondria has been shown to reduce blood-brain barrier permeability and infarct size in mouse models of brain ischemia¹⁴¹. Collectively, these studies highlight mitochondrial transplantation as a potential therapeutic approach to counteract mitochondrial dysfunction and vascular inflammation in cardiovascular diseases^144,145 as well as in other pathological contexts^21,146.

Thus, although certain aspects of this process remain incompletely understood from a basic biology perspective, preclinical studies indicate that mitochondrial transfer can influence cellular function and support tissue homeostasis in the cardiovascular system. Gaining a deeper mechanistic understanding will be critical to harness mitochondrial transplantation as a therapeutic strategy for cardiovascular diseases associated with mitochondrial dysfunction.

7). Therapeutic potential

The recognition of ex-Mito in tissue patho-physiology has spurred the exploration of therapeutic strategies aimed at modulating their release, clearance, and downstream signaling in cardiovascular and other diseases. We briefly discuss some of them here.

Given the high levels of ex-Mito observed in major cardiovascular pathologies such as myocardial infarction^73–76, or atherosclerosis^69–71, and their association with heightened inflammation and poorer prognosis, one major avenue is to enhance the clearance of ex-Mito and mitochondria-derived DAMPs to alleviate their proinflammatory effects. Approaches such as DNase administration to degrade mtDNA⁷⁵, or boosting professional phagocytes like macrophages to engulf extracellular mitochondrial material^18,30, have been shown to reduce systemic and local tissue inflammation. In line with this concept, intrapericardial administration of specific macrophage subpopulations to promote clearance of ex-Mito and other cellular debris has been reported to attenuate sepsis-induced cardiomyopathy³⁰. While these preclinical studies support the notion that targeting ex-Mito clearance or degradation may reduce inflammation and tissue injury, there are, to our knowledge, no established clinical therapies that deliberately target ex-Mito to treat atherosclerosis or improve outcomes following myocardial infarction.

A second strategy is to promote intracellular degradation to avoid mitochondria release. Compounds inducing intracellular quality control mechanisms, such as rapamycin or spermidine, promote intracellular degradation of damaged mitochondria and have demonstrated cardioprotective effects in models of ischemia-reperfusion and heart failure^147,148. By reducing the pool of dysfunctional mitochondria available for extracellular ejection, these approaches may limit inflammation and oxidative stress, thereby complementing strategies aimed at removing ex-Mito discussed above.

Conversely, in certain contexts, facilitating mitochondrial extrusion while ensuring efficient disposal may be beneficial. Given that cells like cardiomyocytes^18,27 and erythrocytes^54,56 eject their mitochondria as part of their normal physiology, supporting this quality control pathway, either by enhancing mitochondria release or their phagocytic uptake, may reduce the accumulation of dysfunctional organelles and improve the fitness of these cells. This concept may be particularly relevant in aging¹⁴⁹ and metabolic diseases^150,151, where cardiac dysfunction is often accompanied by the buildup of damaged cellular components, including mitochondria, due to impaired intracellular quality-control mechanisms. In such settings, stimulating the extrusion of damaged material may help bypass stalled intracellular degradation pathways and contribute to the restoration of cardiomyocyte homeostasis.

Finally, therapeutic mitochondrial transfer has emerged as a promising regenerative strategy. While the underlying mechanisms remain incompletely understood, both transplantation of isolated mitochondria and stimulation of cell-mediated mitochondrial exchange have been shown to restore bioenergetics and enhance tissue resilience across diverse pathological contexts^144–146. In cardiac disease settings, some groups have explored the therapeutic delivery of mitochondria derived either from the same organism (autologous) or from healthy donors (allogeneic). These mitochondrial transfer approaches have demonstrated protective effects against ischemia-reperfusion injury and have been associated with improved myocardial contractile performance^152,153. Consistent with these findings, preclinical studies in multiple cardiac models have provided proof-of-concept that this strategy can enhance tissue resilience and limit injury^154,155. However, whether these benefits primarily arise from the direct incorporation of transplanted mitochondria into stressed cardiomyocytes, or instead reflect alternative local or systemic effects, remains an important question requiring further investigation.

Collectively, these findings underscore the therapeutic potential of ex-Mito while also highlighting the importance of developing carefully tailored approaches that both minimize their potential pro-inflammatory effects and harness their capacity as mediators of intercellular communication and vehicles for therapeutic delivery.

8). Final Conclusions

Recent advances have revealed that ex-Mito are far more abundant in circulation and tissues than previously recognized, overturning the long-held view that mitochondria operate exclusively within cells. Far from being a uniform entity, ex-Mito exist in multiple forms, from free molecular components to intact mitochondria packaged within extracellular vesicles, and display striking variation in their metabolic activity, membrane integrity, and molecular composition. This heterogeneity appears to be functionally relevant, enabling ex-Mito to act as both signals of cellular stress and as transferable bioenergetic units capable of supporting neighboring cells. In the cardiovascular system, these distinct populations have been implicated in processes as diverse as sustaining cellular homeostasis, modulating immune and inflammatory responses, and influencing tissue remodeling under stress or injury. Together, these discoveries mark a paradigm shift in our understanding of mitochondria, positioning them as dynamic extracellular communicators. The growing appreciation of their abundance, diversity, and biological impact opens new opportunities to harness ex-Mito, such as diagnostic markers, intervention targets, and even therapeutic tools in cardiovascular disease and beyond.

Nonstandard Abbreviations and Abbreviations.

AIFM1

Apoptosis-Inducing Factor, Mitochondrial 1

ALIX

ALG-2-interacting protein X

ARRDC1

Arrestin Domain Containing 1

ATGs

Autophagy-related genes

ATP

Adenosine triphosphate

BNIP3

BCL2/adenovirus E1B 19 kDa-interacting protein 3

cADPR

Cyclic ADP-Ribose

CCCP

Carbonyl cyanide m-chlorophenylhydrazone

CD38

Cluster of Differentiation 38

CD41

Cluster of Differentiation 41

CD63

Cluster of Differentiation 63

CD92

Cluster of Differentiation 92

CD144

Cluster of Differentiation 144

cGAS

Cyclic GMP-AMP synthase

CYTC

Cytochrome c

DAMPs

Danger-associated molecular patterns

DNA

Deoxyribonucleic acid

DRP1

Dynamin-Related Protein 1

EC

Endothelial Cell

EV

Extracellular vesicle

ex-Mito

Extracellular Mitochondria

FIS1

Mitochondrial Fission 1

FZO-1

Transmembrane GTPase fzo-1

IFN

Interferon

iPSC

induced pluripotent stem cell

IRF7

Interferon Regulatory Factor 7

GTPase

Guanosine triphosphate hydrolyzing enzyme

KIF5B

Kinesin Family Member 5B

LC3

Microtubule-associated proteins 1A/1B light chain 3

mATG8

Mammalian autophagy-related protein 8

MEFs

Mouse embryonic fibroblasts

MFN-1/2

Mitofusin-1/2

MIRO-1

Mitochondrial Rho GTPase 1

MSCs

Mesenchymal stem cells

mtDNA

Mitochondrial DNA

mTOR

Mechanistic Target of Rapamycin

MyD88

Myeloid differentiation primary response 88

NETs

Neutrophil Extracellular Traps

NLPR3

NOD-, LRR-, and pyrin domain-containing protein 3

NIX

BNIP3-like X

OMA1

Overlapping with the m-AAA protease 1 homolog

OPA1

Optic Atrophy 1

PCR

Polymerase chain reaction

PINK1

PTEN-induced kinase 1

Rab7

Ras-related in brain 7

Rab27

Ras-related in brain 27

Rhot1

Rho GTPase Transport 1

ROS

Reactive oxygen species

SPE-15

Spermatogenesis 15

SQSTM-1

Sequestosome 1

SNAP23

Synaptosome-Associated Protein 23

SNARE

Soluble NSF Attachment Protein Receptor

STING

Stimulator of Interferon Genes

TEM

Transmission electron microscopy

TLR9

Toll-like receptor 9

TNF

Tumor Necrosis Factor

TNTs

Tunneling nanotubes