Exosome-derived LncRNAs in bone remodeling: recent advances and future directions for bone disease therapy

Abstract

Background

Exosomes derived from various cellular sources play a pivotal role in mediating and regulating bone and cartilage regeneration for conditions such as bone defects, fractures, cartilage repair, osteoporosis, and osteoarthritis.

Maintext

As essential intercellular communication vehicles, exosomes transmit long non-coding RNAs (lncRNAs) to modulate cellular behaviors in the bone microenvironment, which has been a central focus of contemporary research.This review consolidates existing evidence on exosome-derived lncRNAs in bone remodeling, revealing their regulatory roles through signaling pathway networks on osteoclasts, osteoblasts, and related bone/cartilage lineage cells, including mesenchymal stem cells, chondrocytes, and osteoclasts. Exosome-encapsulated lncRNAs that regulate osteogenic differentiation of bone marrow mesenchymal stem cells, osteoclast activity, bone-vascular coupling, and bone metastasis show promise as minimally invasive biomarkers for diagnosis, risk stratification, and therapeutic monitoring of bone metabolic disorders.

Conclusion

Moreover, harnessing exosomes as natural, engineerable delivery vehicles can advance the development of bone-targeted, precise, and low-toxicity therapeutic strategies to complement existing pharmacologic and regenerative treatments.

Introduction

The dynamic remodeling capacity of the skeletal system is a fundamental basis for maintaining mechanical stability and mineral homeostasis in the body. The regeneration process of bone and cartilage within the bone microenvironment exhibits high dynamism and complexity. Bone remodeling, as the core regulatory process of skeletal homeostasis, achieves precise renewal of bone tissue through the spatiotemporal coupling of osteoclast-mediated bone resorption and osteoblast-driven bone formation, thereby adapting to the body’s metabolic demands and mechanical functional regulation. The osteoblast lineage (comprising mesenchymal stem cells, committed progenitors, active osteoblasts, bone lining cells, and osteocytes) directs the synthesis and deposition of the bone matrix, while osteoclasts are responsible for its degradation and resorption [1, 2]. The coupled regulation of these two processes constitutes the core mechanism for maintaining bone remodeling homeostasis. Its molecular regulatory network primarily includes three categories: the release of matrix-stored factors, direct cell-to-cell contact signaling, and exosome-mediated intercellular communication. The diverse cellular composition of the bone microenvironment endows it with extensive intercellular communication capabilities. As key carriers of intercellular communication, exosomes have become a research focus in both basic research and clinical therapeutic applications of bone diseases such as osteoporosis. They coordinate bone remodeling-related metabolic pathways by transporting bioactive substances, playing an indispensable role in maintaining bone homeostasis.

Circulating exosomes can carry various molecules such as proteins, microRNAs, lncRNAs, and circular RNAs, which are involved in intercellular information transfer, regulation of gene expression, and disease progression [3]. Among these, lncRNAs—a subclass of non-coding RNAs longer than 200 nucleotides—represent an important regulatory category whose roles in bone metabolism are gradually being elucidated [4, 5]. Studies have shown that the expression of lncRNA TCONS_00072128 in serum exosomes from postmenopausal osteoporosis patients is significantly down‑regulated. This molecule can enhance osteogenic capacity through caspase‑8‑mediated activation of the NLRP3 and nuclear factor‑κB pathways, and its deficiency markedly suppresses osteogenic differentiation [6]. These findings suggest that exosome-derived lncRNAs are important regulators in bone remodeling.

The advancement of genetic engineering technologies has established exosomes as ideal carriers for the targeted delivery of non‑coding RNAs to specific tissues and organs [7]. This offers new strategies for therapeutic intervention in various diseases, while the central role of exosome-derived lncRNAs in the regulation of the skeletal system is being progressively substantiated (Fig. 1). Current research on exosome-derived lncRNAs in the regulation of bone remodeling has made some progress; however, several key scientific questions remain to be addressed. The specific molecular mechanisms by which lncRNAs from different cellular sources regulate the functions of bone-lineage cells are not fully elucidated; their coordinated regulatory networks in intercellular communication within the bone microenvironment remain unclear, and systematic theoretical support for clinical translation in bone-related diseases is still lacking. In light of this, the present review focuses on exosome-derived lncRNAs as core regulatory molecules. Moving beyond the perspective of studying single molecules or cells, we examine their regulatory roles and application potential in bone diseases from the viewpoint of the overall regulatory network of bone remodeling. We focus on the regulatory mechanisms of exosome-derived lncRNAs in bone remodeling and their therapeutic potential for bone diseases. A literature search was conducted using keywords such as “exosome-derived lncRNAs,” “bone remodeling,” and “bone diseases” in academic databases, including PubMed, Web of Science, and Google Scholar. High-impact journals were also manually screened, and reference lists were traced. Basic experimental and clinical studies focusing on the regulation of bone diseases by exosome-lncRNA interactions were included, while irrelevant publications such as case reports were excluded. After independent screening by two authors and arbitration of discrepancies, more than 130 representative and innovative articles were ultimately selected, forming the core evidence for this review.

Fig. 1.

Key cells involved in bone turnover and their exosome-mediated signaling interactions. Exosome-mediated bone remodeling is a highly coordinated dynamic process involving multiple steps, including angiogenesis, cell recruitment, differentiation, matrix synthesis, and degradation. In the bone microenvironment, exosomes serve as crucial carriers for intercellular communication. By delivering bioactive molecules, they precisely regulate the biological behaviors of various cells, such as endothelial cells (ECs), osteoblasts, osteoclasts, mesenchymal stem cells (MSCs), and chondrocytes, thereby maintaining skeletal homeostasis. Dysregulation at any step or disruption in signal transmission can lead to an imbalance in bone homeostasis, potentially triggering diseases such as osteoporosis, osteoarthritis, and bone tumors. Hematopoietic stem cells (HSC, Hematopoietic Stem Cells) also contribute to bone remodeling by regulating osteoclast formation and supporting the vascular niche. This figure was created with BioRender.com (https://biorender.com/)

The purpose of this review is to synthesize the regulatory roles and molecular mechanisms of exosome-derived lncRNAs in the dynamic process of bone remodeling, thereby laying a theoretical foundation for the application of lncRNAs in bone health and providing new research perspectives and strategies for the prevention and rehabilitation of skeletal diseases. The scope of the review centers on the regulatory effects of exosome-derived lncRNAs from different cellular sources on osteoclasts, osteoblasts, and related bone/cartilage-lineage cells (such as MSCs and chondrocytes), as well as their mechanisms of action in metabolic bone diseases. The overall structure of the review will first outline the biological functions of exosomes, followed by a sequential analysis of the regulatory mechanisms of exosome-derived lncRNAs in the osteogenic differentiation of bone marrow mesenchymal stem cells (BMSCs), osteoblast-osteoclast interactions, chondrocyte and osteochondral regulation, and osteogenic-angiogenic coupling. It will further explore their roles and therapeutic potential in various bone diseases, and conclude by summarizing the current research status, highlighting existing limitations, and proposing future research directions.

Biological functions of exosomes

Exosomes, a major subtype of extracellular vesicles, exhibit significant heterogeneity in size, biogenesis pathways, and cellular origins. This heterogeneity is not random but profoundly influences the types and functions of the lncRNAs they carry, thereby determining the specificity and precision of intercellular communication [8]. The typical diameter of exosomes ranges from 30 to 150 nm, yet there is notable variation in size distribution within the population. Smaller exosomes have limited internal space and may preferentially load lncRNAs with lower molecular weight or more compact structures. Studies indicate that differences in the membrane-invagination process lead to variations in vesicle size, which in turn affect cargo loading [9]. The constrained volume implies that cells must actively select the cargo to be packaged into exosomes. This selective pressure likely drives the evolution of specific molecular mechanisms that preferentially sort particular, functionally important lncRNAs (rather than random cytoplasmic RNAs) into exosomes, ensuring the efficiency of information transmission.

Exosomes secreted by different cell types—and even by the same cell under different physiological or pathological conditions—exhibit significant differences in their lncRNA cargo profiles, which form the core basis for their functional specificity [8]. This specificity is primarily determined by cell-specific sorting mechanisms: the selective packaging of lncRNAs into exosomes is not a passive process. Specific RNA-binding proteins (e.g., hnRNPA2B1) can recognize particular sequences or structural motifs on lncRNAs, thereby loading them into multivesicular bodies, the precursors of exosomes. Additionally, the secondary structure of lncRNAs themselves may also participate in this sorting process [10, 11]. These sorting mechanisms and the expression profiles of the involved proteins are markedly distinct across different cell types. Moreover, the cargo of exosomes serves as a “molecular snapshot” of the parental cell state. For instance, exosomes secreted by tumor cells are enriched with lncRNAs associated with proliferation and metastasis (e.g., BCYRN1), whereas exosomes from mesenchymal stem cells may carry lncRNAs involved in tissue repair (e.g., MALAT1) [12, 13]. Consequently, the cellular origin directly defines the “biological address” and functional instructions of exosomal lncRNA cargo. Therefore, we propose that the heterogeneity of exosomes in both size and cellular origin collectively confers dual specificity to lncRNA cargo loading: physical size constraints and active molecular sorting. This enables exosomes to function as highly specialized “information packets” that convey precise regulatory instructions between cells.

The biogenesis of exosomes is not a random "packaging" process but a highly regulated cellular event. This process directly determines which functional lncRNAs can be selectively loaded, secreted, and delivered to recipient cells, thereby mediating precise intercellular communication. On one hand, the biogenesis process determines the selective loading of lncRNAs. Exosome formation begins with early endosomes, which mature into multivesicular bodies (MVBs) where intraluminal vesicles (ILVs) are generated by inward budding of the MVB membrane; these ILVs are ultimately released upon fusion of the MVB with the plasma membrane. The key step for lncRNA entry into this pathway is an active sorting mechanism mediated by RNA-binding proteins (RBPs). For example, hnRNPA2B1 can recognize and bind specific sequences on certain lncRNAs, guiding them to MVBs for loading into ILVs [14]. Other RBPs, such as members of the hnRNPs family, also participate in this process, ensuring that lncRNAs are not passively leaked but actively selected [15]. The sorting of lncRNAs relies on both ESCRT-dependent and ESCRT-independent pathways of MVB formation. The ESCRT-dependent pathway is driven by the endosomal sorting complex required for transport (ESCRT), which recognizes ubiquitinated proteins and may also be involved in recruiting specific lncRNA-protein complexes [15]. In contrast, the ESCRT-independent pathway involves lipid microdomains (e.g., ceramide generated by sphingomyelinase 2/nSMase2) and tetraspanins (such as CD63 and CD81). These components likewise participate in cargo sorting, providing an alternative regulatory channel for lncRNA loading [15, 16]. The activation state of the biogenesis pathway and the composition of the sorting machinery (e.g., expression of specific RBPs) directly determine the specificity of the lncRNA cargo in exosomes. On the other hand, specific loading is a prerequisite for functional delivery. The precision of loading ensures the efficiency and functional relevance of delivery. The lipid bilayer structure of exosomes protects lncRNAs from degradation by extracellular RNases, enabling them to remain stable in body fluids and be transported over long distances to target cells. After exosomes are taken up by recipient cells (via membrane fusion, endocytosis, etc.), the carried lncRNAs are released into the cytoplasm and can exert regulatory functions in the target cell through multiple mechanisms, such as acting as competing endogenous RNAs, serving as scaffolds or decoys [17], or directly interacting with proteins [18]. The specificity guaranteed by biogenesis makes exosomes “signal packages” with well-defined functions; dysregulation of the loading process may lead to disease.

In summary, biogenesis acts as the “controller” while functional delivery is the “goal.” Through active sorting mechanisms (e.g., RBP recognition) and specific formation pathways (ESCRT-dependent/independent), exosomes strictly select and package lncRNAs, endowing them with cargo specificity. Based on this specific loading, exosomes can stably and precisely deliver lncRNAs with clear regulatory functions to target cells, where they execute tasks such as gene-expression regulation, thereby mediating important physiological and pathological processes.

Exosome-derived lncRNAs regulate the osteogenic differentiation of BMSCs

BMSCs, derived from the bone marrow cavity, are multipotent stromal cells with multidirectional differentiation potential, capable of differentiating into various cell types such as osteoblasts, adipocytes, chondrocytes, and neural lineage cells [19]. They serve as the core cellular component for bone regeneration. The proper maintenance of their osteogenic differentiation capacity is crucial for bone homeostasis, fracture repair, and the prevention and control of osteoporosis, whereas excessive adipogenic differentiation leads to bone marrow adipose accumulation and bone loss. The regulation of this differentiation balance represents a central issue in bone metabolism research. With advancing age, the osteogenic differentiation potential of BMSCs gradually diminishes while their adipogenic capacity increases, contributing to age-related bone loss. High-throughput gene sequencing studies have revealed that over 1,000 lncRNAs exhibit differential expression during the osteogenic differentiation of BMSCs [20, 21], highlighting their sensitivity as indicators of osteogenic differentiation capability. Exosomes, as important carriers of intercellular communication, can precisely regulate the osteogenic-adipogenic fate of BMSCs by loading and delivering lncRNAs. This regulatory mechanism heavily relies on the construction of competing endogenous RNA (ceRNA) networks, activation/inhibition of classical signaling pathways, and mediation of protein–protein interactions. Exosomal lncRNAs from different cell sources achieve precise control over BMSC osteogenic differentiation through conserved or specific regulatory modes, and are involved in the dysregulation of bone metabolism under pathological conditions such as age-related and postmenopausal osteoporosis.

Exosomal lncRNA regulatory mechanisms based on the ceRNA network

The ceRNA mechanism represents the most central and conserved pathway through which exosomal lncRNAs regulate the osteogenic differentiation of BMSCs. In this model, lncRNAs function as "molecular sponges" that adsorb microRNAs (miRNAs), thereby relieving the inhibitory effect of miRNAs on their target genes and subsequently activating osteogenic differentiation-related molecular pathways. This is currently the most extensively studied regulatory mode, with several key lncRNAs exerting their functions via this mechanism.

For instance, exosomal lncRNA NEAT1 derived from MSCs can act as a ceRNA by adsorbing miR-221-3p, which regulates the expression of the sirtuin (Sirt) family. Through the Sirt signaling axis, it enhances the osteogenic differentiation capacity of BMSCs. Concurrently, this molecule can activate the Sirt family to alleviate cell apoptosis, providing dual protection for the survival and differentiation of BMSCs during bone repair [22, 23]. Exosomal lncRNA XIST targets and adsorbs miR-30a-5p, relieving its inhibition on the core osteogenic transcription factor Runx2. This significantly upregulates Runx2 expression and induces osteogenic differentiation in human BMSCs. This mechanism can effectively inhibit the decline in osteogenic capacity of BMSCs during osteoporosis progression and represents a potential regulatory target for postmenopausal osteoporosis [24]. Exosomal lncRNA MSTRG25 binds to miR-939-5p, promoting BMSC osteogenic differentiation by activating PAX8 gene expression, further enriching the diversity of the ceRNA network in this regulatory process [25].

Furthermore, in the pathological context of osteoporosis, the expression of exosomal lncRNA SNHG14 derived from BMSCs is downregulated. Its function as a ceRNA to adsorb miR-27a-3p is weakened, leading to suppressed expression of lamin B1. This ultimately results in reduced osteogenic differentiation and enhanced adipogenic differentiation of BMSCs. Supplementation with SNHG14 can restore this ceRNA network, rebalancing the osteogenic-adipogenic differentiation equilibrium in BMSCs [26].

Regulatory mechanisms of exosomal lncRNAs dependent on activation of classical signaling pathways

Exosomal lncRNAs can regulate the osteogenic differentiation of BMSCs by directly or indirectly mediating the activation of classical bone-metabolism signaling pathways. Among these, the TGF-β signaling pathway and the Wnt/β-catenin signaling pathway are two core pathways and are key routes mediating bone-metabolism disorders under pathological conditions.

Bioinformatics analysis of the GSE35956 dataset revealed that exosomal lncRNA RAD51-AS1 is a significantly down-regulated key molecule in BMSCs from osteoporosis patients. By interacting with the YBX1 protein, it regulates the transcription and translation of Smad7 and Smurf2, thereby activating the TGF-β signaling pathway and up-regulating the expression of molecules such as proliferating cell nuclear antigen and SIVA1, ultimately enhancing BMSC proliferation and promoting osteogenic differentiation [27]. Conversely, loss of RAD51-AS1 expression directly leads to insufficient activation of the transforming growth factorβ (TGF-β) pathway, resulting in inhibition of osteogenic differentiation and apoptosis of BMSCs, which constitutes an important molecular mechanism underlying osteoporosis [27]. The Wnt/β-catenin signaling pathway is a core positive regulatory pathway for osteogenic differentiation. Exosomes can activate this pathway by delivering specific lncRNAs, forming a positive-feedback regulatory loop for osteogenic differentiation. LncRNAs from BMSC-derived exosomes significantly influence the pathogenesis of osteoporosis by regulating transcriptional cascades involved in bone-matrix homeostasis. In postmenopausal osteoporosis patients, BMSC-derived exosomes contain 286 differentially expressed lncRNAs, of which 148 are up-regulated and 138 are down-regulated. These molecules can indirectly regulate the Wnt/β-catenin pathway through mechanisms such as ceRNA competition, while also affecting the activity of other pathways including MAPK and PI3K-Akt, ultimately leading to a decline in the osteogenic differentiation potential of BMSCs and serving as an important molecular basis for postmenopausal bone loss [28].

Regulatory mechanisms of exosomal lncRNAs in mediating the balance between osteogenic and adipogenic differentiation

In the bone marrow microenvironment, the interrelationship between osteogenic differentiation and adipogenic differentiation of mesenchymal stem cells governs bone mass homeostasis. A shift in the balance between these two differentiation pathways constitutes an important pathological basis for the development of osteoporosis, with aging and obesity being key drivers of this pathological shift. Osteoporosis arises from a pathological transformation in the differentiation potential of BMSCs, in which the adipogenic pathway predominates at the expense of osteogenic capacity [29–31]. Observational studies have shown that the incidence of central obesity increases sharply with age, especially in postmenopausal women. Clinical observations indicate a significant positive correlation between increased bone marrow fat content, visceral fat accumulation, and decreased bone mineral density as well as bone loss, a phenotypic association that is a typical clinical feature of age-related and postmenopausal osteoporosis [32–34]. The core pathological manifestation of osteoporosis is the pathological shift in the differentiation potential of BMSCs, characterized by a dominant adipogenic differentiation pathway and impaired osteogenic differentiation. This cellular-level phenotypic change directly corresponds to the clinical phenotypes of bone loss and fat accumulation, providing cellular-level phenotypic evidence for the link between aging, obesity, and bone metabolism disorders.

Meanwhile, mechanism-verified evidence has confirmed that bone marrow adipocytes are key effector cells mediating the imbalance between osteogenic and adipogenic differentiation and bone metabolism disorders in the context of aging and obesity. A research team from the University of Michigan Medical School conducted mechanistic studies using a bone marrow adipocyte-specific Cre mouse model. They demonstrated that clearing bone marrow adipocytes by expressing diphtheria toxin A and knocking down peroxisome proliferator-activated receptor γ (PPARγ) directly enhanced bone formation capacity and increased bone mass in adipocyte-enriched sites in mice. This intervention also protected mice from bone loss induced by caloric restriction or ovariectomy and promoted fracture healing, confirming the direct role of bone marrow adipocytes in bone mass regulation [35]. Further mechanistic experiments verified that bone marrow adipocytes can directly inhibit osteogenesis, promote adipogenesis, and enhance bone resorption through multiple molecular pathways, serving as a key molecular node linking obesity and osteoporosis. First, IL-6, IL-1β, and TNF-α released by bone marrow adipocytes establish an inflammatory microenvironment in the bone marrow by activating the JAK-STAT/NF-κB signaling pathway, thereby significantly inhibiting the osteogenic differentiation of BMSCs [36, 37]. Second, they also secrete PPARγ and C/EBPα to promote adipogenic differentiation of BMSCs while suppressing osteoblast function, exacerbating bone metabolism disorders [38]. Third, they secrete receptor activator of nuclear factor-κB ligand (RANKL), which directly enhances osteoclast activity, further disrupting the balance between bone resorption and formation and accelerating the progression of osteoporosis [39]. These mechanistic studies delineate the molecular pathways through which bone marrow adipocytes mediate bone metabolism disorders associated with obesity and aging, providing direct experimental evidence for the regulation of osteogenic-adipogenic differentiation imbalance. The imbalance between osteogenic and adipogenic differentiation of BMSCs is a core pathological feature of age-related and postmenopausal osteoporosis. Exosomal lncRNAs can achieve precise regulation of this balance by targeting key differentiation factors [40–42]. Some molecules can also indirectly regulate this balance through intercellular communication that mediates muscle-bone and macrophage-bone interactions.

Exosomal lncRNA SNHG1 interacts with polypyrimidine tract-binding protein 1, upregulates DNA methyltransferase 1 expression, promotes osteoprotegerin methylation and expression inhibition, drives BMSCs toward adipogenic differentiation, and exacerbates osteoporosis progression [41]. Knockdown of SNHG1 reverses this effect, increasing the expression of osteogenic-related factors and inhibiting adipogenic factor activity. In contrast, exosomal lncRNA NEF functions through the miR-155/PTEN axis, positively promoting osteogenic differentiation of BMSCs while significantly inhibiting their adipogenic differentiation [43]. LncRNA SNHG5, through the SNHG5/miR-582-5p/RUNX3 regulatory axis, achieves dual effects of promoting osteogenic differentiation and inhibiting adipogenic differentiation. Its expression is upregulated during osteogenic differentiation and downregulated during adipogenic differentiation, making it a specific molecule regulating the differentiation fate of BMSCs [44, 45].

Indirect regulation mediated by exosomal intercellular communication is equally important: Myoblast-derived exosomal Prrx2 can bind to the lncRNA MIR22HG promoter and upregulate its expression. MIR22HG acts as a ceRNA that sequesters miR-128, thereby activating the YAP pathway. YAP activation suppresses the Hippo pathway, promotes osteogenic differentiation of BMSCs, and significantly improves bone loss in osteoporotic mice [46]. In fracture microenvironments stimulated by hypoxia or cerebrospinal fluid, macrophage-derived exosomes can deliver lncRNAs such as LOC103691165. This molecule is stably expressed in both M1 and M2 macrophages and is a key factor enhancing the osteogenic capacity of BMSCs. Inhibition of exosome secretion completely blocks the promotive effect of macrophages on osteogenic differentiation of BMSCs [47].

The regulation of osteogenic differentiation in BMSCs by exosome-derived lncRNAs exhibits both mechanistic conservation and molecular specificity. The ceRNA network serves as the most central conserved regulatory mechanism, through which key molecules such as NEAT1, XIST, and SNHG14 exert their effects. Classic signaling pathways, including TGF-β and Wnt/β-catenin, act as core downstream targets that mediate osteogenic differentiation, forming common pathways utilized by different lncRNAs. At the same time, distinct lncRNAs display clear pathological specificity: for example, RAD51-AS1 and SNHG14 are down-regulated molecules associated with osteoporosis, LOC103691165 acts as a pro-osteogenic molecule in the fracture-repair microenvironment, and MIR22HG serves as a key mediator of muscle–bone crosstalk. This specificity renders them potential targets for precise intervention in bone diseases. However, several core scientific questions in this field remain unresolved. First, the cooperative network of exosomal lncRNAs derived from different cell sources (e.g., MSCs, macrophages, myoblasts) in regulating BMSC osteogenic differentiation has not been elucidated, and the regulatory hierarchy among various exosomes in pathological microenvironments remains unclear. Second, among the 286 differentially expressed exosomal lncRNAs in osteoporosis, the target miRNAs, downstream pathways, and functions of most molecules have not been validated; the molecular mechanisms through which they coordinately regulate bone metabolism still require systematic dissection. Third, research on post-translational modifications (e.g., methylation, ubiquitination) that govern the balance between osteogenic and adipogenic differentiation of BMSCs by exosomal lncRNAs is insufficient, and the specific interaction sites and molecular patterns with proteins need further exploration. Fourth, the clinical translation of exosomal lncRNAs as therapeutic targets remains rudimentary; issues such as targeted delivery efficiency, in vivo stability, and off-target effects have yet to be addressed, posing major obstacles to translating basic research into clinical applications.

Overall, MSC-derived exosomal lncRNAs regulate the osteogenic differentiation of BMSCs, bone regeneration, and disease progression through multiple mechanisms, demonstrating promising potential for the treatment of degenerative disorders such as osteoporosis (Fig. 2).

Fig. 2.

Exosome-derived lncRNAs regulate the osteogenic differentiation of BMSCs. The figure uses functional annotations and directional arrows to clearly illustrate the regulatory effects of exosomal long non-coding RNAs (lncRNAs) derived from different cell sources on the osteogenic differentiation of BMSCs. It distinguishes the cellular origins of exosomes, such as BMSCs, macrophages, and the mouse myoblast cell line C2C12, reflecting the heterogeneity of exosomal lncRNA secretion within the bone microenvironment. Among them, paired related homeobox 2 (Prrx2)-enriched exosomes derived from C2C12 cells upregulate lncRNA MIR22HG, which promotes the osteogenic differentiation of BMSCs through a dual mechanism involving transcriptional activation and a competing endogenous RNA (ceRNA) network by sponging microRNA-128 (miR-128) and regulating Yes-associated protein (YAP) in the Hippo signaling pathway. The regulation of BMSC osteogenic differentiation by lncRNA LOC103691165 also involves macrophage polarization, including classically activated macrophages (M1) and alternatively activated macrophages (M2). This figure created with BioRender.com (https://biorender.com/)

Exosome-derived lncRNAs regulate osteoblast‒osteoclast crosstalk to trigger bone remodeling

Bone morphogenesis constitutes a homeostatic equilibrium sustained through spatiotemporal coordination among osteoblasts, osteoclasts, and chondrocytes. Osteoclasts remove the old matrix, releasing space and minerals; osteoblasts deposit new bone to complete structural reconstruction; and chondrocytes construct the growth framework and guide direction. Bone growth can be divided into three core stages: embryonic ossification, longitudinal bone growth, and bone remodeling. Embryonic ossification includes intramembranous ossification (such as in the cranial bones) and endochondral ossification (such as in long bones). Longitudinal bone growth is facilitated by endochondral ossification at the epiphyseal growth plate. Bone remodeling persists in adulthood, with osteoblasts and osteoclasts dynamically balancing to sustain bone mass [48]. Under physiological homeostasis, the equilibrium between osteoblast-mediated bone deposition and osteoclast-mediated bone degradation governs the rate of bone formation. While osteoblasts primarily govern bone matrix formation and mineralization, osteoclasts breakdown skeletal organic/inorganic substances—a dual mechanism critical for proper bone functionality [49]. Although the physiological processes governed by these three cell types differ, they often influence one another. Osteoblasts secrete RANKL and OPG, which directly modulate osteoclast formation and function, thus controlling bone resorption. Their coordinated action regulates bone remodeling via the RANK-RANKL-OPG signaling pathway, along with various growth factors and cytokines [50]. Exosomes from osteoclasts can inhibit osteoblast activity in vitro and impede new bone formation in vivo [51]. Osteoblast‒osteoclast crosstalk is a crucial physiological process in bone remodeling. LncRNAs are critical players in regulating this crosstalk.

LncRNAs independently regulate osteoblast and osteoclast activity. They typically regulate osteoblast and osteoclast differentiation and function via ceRNA mechanisms, epigenetic modifications, and signaling pathway regulation. The lncRNA H19 enhances bone formation via the Wnt/β-catenin pathway and simultaneously suppresses osteoclast activity [52]. Similarly, the lncRNA DANCR inhibits osteoblast maturation through the Runx2 signaling axis [53, 54]. Both of these processes involve key osteogenic signaling pathways. The lncRNA MALAT1 facilitates osteoclastogenesis by modulating miR-124, leading to increased expression of NFATc1 [53]. These studies highlight the important role of lncRNAs in maintaining the dynamic balance between osteogenesis and osteoclastogenesis, although their regulatory mechanisms differ. Exosomes act as biological carriers for lncRNAs, enabling signal exchange between osteoblasts and osteoclasts. Exosomes are key mediators of intercellular signaling during various physiological and pathological conditions, particularly for transporting and modulating lncRNAs. Exosomes influence bone metabolism by carrying lncRNAs, and their involvement in the communication between osteoblasts and osteoclasts is increasingly understood. Exosomal lncRNAs significantly influence bone remodeling by modulating pathways such as the RANKL and TGF-β pathways [55]. RAW264.7-secreted exosomes harbor the lncRNAs NONMMUT000375.2 and NONMMUT071578.2, which drive osteoclast differentiation and suppress osteoblastic activity [56]. Notably, the regulatory mechanisms of exosome-mediated lncRNAs vary. For example, the lncRNAs NONMMUT000375.2 and NONMMUT071578.2 exert dual regulatory effects on both osteoclasts and osteoblasts. However, current studies show that most lncRNAs do not have dual regulatory effects on bone formation or resorption. This review categorizes the regulatory roles of exosome-derived lncRNAs in bone metabolism by examining their effects on osteoblasts, osteoclasts, and chondrocytes.

It is noteworthy that exosome-mediated lncRNA regulation exhibits significant heterogeneity. The function of lncRNAs as dual regulators is not constant but is co-influenced by cell source specificity and microenvironmental factors. On one hand, cell-type specificity determines the regulatory bias of exosomal lncRNAs. lncRNAs from osteoblast-derived exosomes primarily regulate osteoblast activation and inhibit osteoclast formation, whereas lncRNAs from osteoclast-derived exosomes predominantly promote osteoclast differentiation and suppress osteoblast function.

Exosome-derived lncRNAs regulate osteoblast differentiation

Exosome-derived lncRNAs that regulate osteoblast proliferation or differentiation primarily originate from MSCs and osteoclasts. The role of exosomes derived from BMSCs in bone metabolism has attracted early attention. BMSCs, as highly plastic stem cells, can regulate bone repair and regeneration by secreting exosomes. LncRNAs from BMSC-derived exosomes are vital in osteoblast regulation. Therapeutically, BMSC-secreted exosomes rescued KLF3-AS1 deficiency in the serum of fracture patients, which activated osteoblast migration/proliferation and concurrently inhibited apoptosis [57]. The overexpression of exosome-derived LINC00520 in human umbilical cord mesenchymal stem cells (hucMSCs) enhances osteoblast proliferation and calcium deposition, whereas its knockdown reduces osteoblast activity. LINC00520 is essential for calcium deposition, indicating its utility as a therapeutic option against osteoporosis [58]. The exosome-derived lncRNA lncTUG1 from BMSCs regulates osteoblast activity via a ceRNA mechanism, controlling the miR-22-5p/Anxa8 axis [59]. The lncRNA MALAT1 encapsulated in BMSC exosomes functions as an epigenetic modulator that potentiates osteoblast mineralization capacity through the miR-34c/SATB2 signaling axis. This pathway effectively counteracts bone loss in osteoporotic conditions, highlighting its therapeutic potential [56]. This study suggests that exosomal lncRNAs from BMSCs have considerable potential in osteoporosis treatment.

Exosomal lncRNAs secreted by osteoclasts also play pivotal regulatory roles in osteoblastogenesis and osteoblast differentiation. Liu et al. conducted RNA sequencing to screen for differentially expressed lncRNAs and mRNAs in RANKL-induced osteoclast models and characterized osteoclast-derived exosomes. The identification of the lncRNA AW011738 in osteoclast exosomes as a regulator of the miR-24–2-5p/TREM1 axis clarifies a key mechanism for impaired osteoblast differentiation in osteoporosis, highlighting exosomal lncRNAs as potential therapeutic targets [60]. In a titanium particle-induced osteolysis model, osteoclast-derived exosomes containing the lncRNAs NONMMUT000375.2 and NONMMUT071578.2 hindered osteoblast differentiation and intensified the imbalance between osteoclastogenesis and osteogenesis by modulating genes such as Bcl2, Wnt11, TGF-β, and Pdk1 [56]. Inflammatory osteoclast-derived exosomes (iOCL-exos) are enriched with the lncRNA LIOCE. This molecule enhances osteoblast function by inhibiting ubiquitination and subsequent degradation of the transcription factor Osterix. In inflammatory bone resorption models, the injection of exosomes encapsulating LIOCE effectively reduces bone loss, providing a potential intervention strategy for bone metabolic diseases [61].

Exosome-derived lncRNAs regulate osteoclast differentiation

The mechanisms by which lncRNAs regulate osteoclast activation can be broadly classified into two main pathways. First, lncRNAs function as ceRNAs, acting as molecular sponges to sequester downstream miRNAs and target genes involved in osteoclast activation. Second, lncRNAs interact with transcription factors and various other proteins to modulate osteoclast activation.

Elevated plasma levels of lncRNA TUG1 in osteoporotic cohorts serve as a diagnostic biomarker, with experimental evidence confirming its role in stimulating osteoclast proliferation, suppressing apoptosis, and downregulating PTEN expression. Silencing lncRNA TUG1 via siRNA resulted in the opposite effects [62]. The RANKL-induced osteoclastic differentiation of RAW264.7 cells is augmented by lncRNA-MIR22HG [63]. Exosome-derived lncRNAs affect osteoclast differentiation and bone resorption via intricate ncRNA regulatory networks, including miRNAs, circRNAs, and lncRNAs. Abnormal osteoclast activity can lead to disruption of subchondral bone remodeling, resulting in bone-related diseases [64]. For example, in multiple myeloma (MM)-related bone disease research, the lncRNA MALAT1 was found to stabilize its expression via m5C methylation (NSUN2-YBX1 axis), and exosomes transported this lncRNA to osteoclasts, activating the RANKL-AKT/MAPK signaling pathway to promote bone destruction, with its level positively correlated with RANKL expression and the extent of bone damage [65]. The exosome-derived lncRNA MALAT1 from osteoblasts promotes osteoclastogenesis by acting as an endogenous sponge, competitively binding to miR-124 and regulating NFATc1 expression [66]. Bioactive glass nanoparticles (BGNs) induce the secretion of exosomes by BMSCs, which significantly inhibits osteoclast differentiation. The mechanism involves the binding of the lncRNA NRON in BGN + BMSC exosomes to NFATc1, preventing its nuclear translocation and inhibiting osteoclast differentiation, thus alleviating bone loss and restoring femoral mechanical properties in osteoporotic mice [67]. LncRNAs mediate osteoblast‒osteoclast coupling through various regulatory mechanisms, influencing bone homeostasis, with exosomes playing crucial roles in signal transmission. A comprehensive examination of the lncRNA–exosome relationship in bone metabolism will offer novel theoretical perspectives and intervention approaches for fracture healing, osteoporosis, and bone-destructive conditions (Fig. 3).

Fig. 3.

Exosome-derived lncRNAs regulate osteoblast‒osteoclast crosstalk to trigger bone remodeling. The figure illustrates the comprehensive molecular regulatory network of exosome-derived lncRNAs in modulating osteoclast differentiation, activation, and bone resorption function, as well as the bidirectional crosstalk between osteoblasts and osteoclasts in the bone microenvironment. Osteoblast-derived exosomal metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) sequesters miR-214, relieving its inhibition of nuclear factor of activated T-cells, cytoplasmic 1 (NFATC1) and promoting osteoclast differentiation. BMSCs-derived exosomal MALAT1 regulates osteoblast mineralization through the miR-34c/Special AT-rich sequence-binding protein 2 (SATB2) axis, whereas bioactive glass nanoparticle-modified BMSC-derived exosomal noncoding repressor of NFAT (NRON) directly binds NFATC1 and inhibits its nuclear translocation, thereby suppressing osteoclast differentiation. Multiple myeloma cell (MM-cell)-derived exosomal MALAT1 undergoes m⁵C methylation via the NOP2/Sun RNA methyltransferase family member 2 (NSUN2)–Y-box binding protein 1 (YBX1) complex and activates the receptor activator of nuclear factor κB ligand (RANKL)–Protein kinase B/Mitogen-activated protein kinase (AKT/MAPK) pathway in osteoclasts, inducing osteolytic bone destruction. Osteoclast-derived exosomes carry lncRNAs NONMMUT000375.2, NONMMUT071578.2, and AW011738, which regulate osteoblast differentiation through the B-cell lymphoma 2/Wnt11 axis and the miR-24–2-5p/Triggering receptor expressed on myeloid cells 1 (TREM1) axis, respectively; exosomal LncRNA Inflammatory Osteoclast Exosomes (LIOCE) stabilizes the key osteogenic transcription factor Osterix by inhibiting its ubiquitination and indirectly modulates osteoclast activity. Exosomal lncRNAs TUG1 (Taurine Upregulated Gene 1) and miR-22 Host Gene (MIR22HG) directly promote osteoclast proliferation and RANKL-induced osteoclast differentiation, respectively. Paired Related Homeobox 2 (Prrx2) is delivered via C2C12 myocyte-derived exosomes to target BMSC. All regulatory pathways have been validated in vitro and/or in vivo, highlighting the central role of exosomal lncRNAs in mediating physiological bone remodeling and pathological bone destruction via osteoblast–osteoclast crosstalk. This figure was created with BioRender.com (https://biorender.com/)

The physicochemical properties and inflammatory status of the bone microenvironment can significantly alter the regulatory functions of exosomal lncRNAs. In the pathological microenvironment of a titanium particle-induced osteolysis model, exosomal NONMMUT000375.2 and NONMMUT071578.2 from osteoclasts exacerbate the imbalance of bone formation and resorption by regulating genes such as Bcl2 and Wnt11. Conversely, in an inflammatory bone resorption model, the lncRNA LIOCE in exosomes derived from inflammatory osteoclasts can inhibit the ubiquitination and degradation of the osteoblast transcription factor Osterix, thereby enhancing osteoblast function and reversing abnormal bone resorption under pathological conditions. Furthermore, microenvironmental factors such as hypoxia and mechanical stress can also alter the expression profiles of lncRNAs within exosomes, subsequently affecting their bidirectional regulatory effects on osteoblasts and osteoclasts. Current research indicates that most lncRNAs do not possess the dual function of simultaneously regulating both bone formation and bone resorption. Therefore, this study categorizes and elaborates on the regulatory roles of exosome-derived lncRNAs in bone metabolism based on their distinct effects on osteoblasts, osteoclasts, and chondrocytes.

Exosome-derived lncRNAs in osteochondral cartilage cells

The longitudinal growth of long bones is regulated by the growth plate cartilage, whose development and homeostasis are closely associated with the biological behavior of MSCs [68, 69]. MSCs are the core stem-cell population in the skeletal system responsible for osteochondral lineage commitment. Under the regulation of key chondrogenic transcription factors (e.g., SOX9, RUNX2), MSCs first differentiate into chondroprogenitor cells and subsequently develop into mature chondrocytes. This process constitutes the cellular basis for growth-plate cartilage formation, longitudinal bone growth, and osteochondral repair.Exosomes, serving as pivotal intercellular communication vehicles, mediate the crosstalk between stem cells and chondrocytes within the osteochondral microenvironment, significantly promoting chondrocyte proliferation and migration,two core processes in the in vivo and in vitro regenerative repair of articular cartilage. Articular cartilage degeneration primarily relies on chondrocytes for repair; however, the limited proliferative and differentiation capacities of mature chondrocytes impose substantial constraints on cartilage regeneration. MSCs possess strong chondrogenic differentiation potential and paracrine regulatory abilities, making them a key stem-cell source for osteochondral regeneration. Exosomes secreted by MSCs, acting as functional “effector molecules,” can transport lncRNAs and other bioactive substances, thereby bridging the gap between stem-cell biology and chondrocyte metabolism in osteochondral regulation (Fig. 4).

Fig. 4.

Exosome-derived lncRNAs regulate chondrocyte proliferation and differentiation. The figure illustrates the molecular network through which exosome-derived lncRNAs regulate chondrocyte proliferation and differentiation. BMSC-derived exosomal lncRNA Kruppel-like factor 3 antisense RNA 1 (KLF3-AS1) acts as a competing endogenous RNA (ceRNA) by sequestering miR-338-3p, thereby promoting chondrocyte function. Umbilical mesenchymal stem cell (UMSC)-derived exosomal lncRNA H19 upregulates Forkhead box O3 (FoxO3) expression through sponging miR-296-3p, enhancing chondrocyte proliferation and differentiation. Circulating exosomal lncRNA Immune System-Related lncRNA (ISSRL) modulates chondrocyte activity by targeting the miR-877-3p/Granzyme B (GZMB) axis, and its dysregulation in idiopathic short stature (ISS) patients suggests its potential as a biomarker for chondrocyte developmental disorders. Together, these exosomal lncRNAs constitute a paracrine network that regulates chondrocyte homeostasis and pathological cartilage dysfunction. This figure was created with BioRender.com (https://biorender.com/)

Idiopathic Short Stature (ISS) is a common pediatric disorder of unknown etiology. Its pathogenesis is closely associated with impaired chondrogenic differentiation of mesenchymal stem cells within the growth plate and abnormal proliferation of chondrocytes. Co-culture of human chondrocytes with exosomes derived from the plasma of ISS patients results in impaired chondrocyte growth and bone formation [3]. This phenomenon is attributed to the aberrant expression of exosomal lncRNAs, which disrupts the chondrogenic differentiation program of growth‑plate progenitor cells. Silencing the idiopathic short stature‑related lncRNA (ISSRL) in plasma exosomes from patients with idiopathic short stature reverses its inhibitory effects on chondrocyte proliferation and bone formation. The underlying mechanism involves the elevated ISSRL in plasma exosomes interacting with miR‑877‑3p to regulate the GZMB axis, thereby reducing the proliferative capacity of chondrocytes and the growth plate as well as bone formation, ultimately impairing the stem cell‑osteocyte crosstalk within the growth‑plate microenvironment [3]. Researchers have also designed engineered exosomes, CT-Exo-siISSRL-oeGH, which successfully deliver small interfering RNA (siRNA) and growth hormone (GH) to the growth-plate cartilage. These exosomes can not only silence the aberrant lncRNA ISSRL but also up-regulate GH expression, thereby promoting chondrogenic differentiation of mesenchymal stem cells within the growth plate. This approach effectively alleviates the short-stature phenotype and provides a stem-cell-based exosomal lncRNA intervention strategy for osteochondral developmental disorders [3].

Exosomes derived from monocytes promote cartilage repair in osteoarthritis by modulating macrophage polarization and the chondrogenic differentiation potential of mesenchymal stem cells. Among them, lncRNA MM2P can induce M2-type macrophage polarization and facilitate the transfer of SOX9 from M2-type exosomes to chondrocytes, thereby enhancing chondrocyte function [70]. As a core chondrogenic transcription factor in mesenchymal stem cells, SOX9 is crucial for initiating and maintaining the chondrogenic phenotype. Exosome-mediated transfer of SOX9 connects macrophage polarization, chondrogenic regulation of stem cells, and maintenance of chondrocyte function, forming a multi-cellular regulatory network centered on stem-cell biology for osteochondral repair. Recent studies have shown that exosomes derived from BMSCs are enriched with lncRNA KLF3-AS1, which in vitro enhances chondrocyte proliferation while promoting the chondrogenic differentiation of BMSCs themselves, thereby achieving a dual role of stem-cell self-differentiation and paracrine regulation of chondrocytes. Bioinformatics analyses have confirmed that KLF3-AS1 can act as a ceRNA for miR-338-3p, up-regulating the expression of chondrogenic target genes in BMSCs by sequestering miR-338-3p, thereby promoting their differentiation toward chondroprogenitors [71, 72]. Consequently, exosomes derived from mesenchymal stem cells can promote the chondrogenic differentiation of endogenous mesenchymal stem cells at the injury site and enhance the functional activity of local chondrocytes, thereby facilitating cartilage regeneration in osteoarthritis [73]. Zhou et al. [74] investigated the protective effects of extracellular vesicles secreted by human umbilical cord mesenchymal stem cells (hucMSCs-EVs) in a mouse model of osteoarthritis. HucMSCs-EVs interact with methyltransferase-like 3 (METTL3), reducing N⁶-adenosine methylation of NLRP3 inflammasome-mediated mRNA in macrophages. This interaction promotes the ubiquitination of the NLRP3 inflammasome and alleviates its inhibitory effect on chondrocyte proliferation [74]. More importantly, it alleviates the inflammatory suppression mediated by NLRP3 on the chondrogenic differentiation of BMSCs within the osteochondral microenvironment. HucMSC-EVs establish a multi-target regulatory mode for osteochondral protection based on stem cell biology by simultaneously regulating macrophage inflammation, stem cell chondrogenic potential, and chondrocyte proliferation.

LncRNA H19 is a crucial chondrogenic regulatory lncRNA in exosomes derived from mesenchymal stem cells. Exosomes derived from human umbilical cord mesenchymal stem cells (UMSCs) that overexpress lncRNA H19 play significant roles in both osteogenesis and cartilage regeneration [75]. H19 is a core long non-coding RNA that maintains the chondrogenic differentiation potential of human umbilical cord mesenchymal stem cells. After being delivered to chondrocytes via exosomes, it can act as a competitive endogenous RNA to enhance osteochondral activity. To validate the interactions among miR-29b-3p, lncRNA H19, and the target mRNA FoxO3, Yan et al. [76] conducted dual-luciferase reporter assays, RNA pull-down experiments, RNA immunoprecipitation (RIP), and fluorescence in situ hybridization (FISH). Apoptosis, migration, senescence, and matrix secretion assays were performed on chondrocytes exposed to exosomes derived from human umbilical cord mesenchymal stem cells overexpressing lncRNA H19. The results demonstrated that exosomal H19 from human umbilical cord mesenchymal stem cells not only promotes the chondrogenic differentiation of endogenous mesenchymal stem cells at cartilage defect sites via the H19/miR‑29b‑3p/FoxO3 axis but also directly inhibits chondrocyte apoptosis and enhances matrix secretion [76]. The mechanism of lncRNA H19/miR-29b-3p was validated in a cartilage-defect model in SD rats. It was confirmed that lncRNA H19, delivered to chondrocytes via exosomes derived from human umbilical cord mesenchymal stem cells, can act as a competitive endogenous RNA for miR-29b-3p, up-regulating FoxO3 expression and enhancing the chondrogenic activity of both mesenchymal stem cells and mature chondrocytes. The cartilage-repair effect of intra-articular injection of exosomes overexpressing lncRNA H19 could be inhibited by an miR-29b-3p agonist, further substantiating the central role of stem-cell-derived exosomal lncRNA H19 in coordinating MSCs chondrogenesis and chondrocyte function, and its involvement in osteochondral repair [76]. Therefore, exosome-derived lncRNA H19 plays a pivotal role in cartilage defect repair strategies. The H19/miR-29b-3p/FoxO3 axis mediated by H19 bidirectionally regulates chondrocytes and MSCs, promoting their migration and matrix secretion while inhibiting apoptosis and senescence both in vitro and in vivo.

It should be clarified that current research findings regarding exosome-derived lncRNAs in the regulation of bone-cartilage cells and cartilage repair remain at the preclinical stage; no human clinical trials have been conducted thus far. Numerous unresolved issues persist for their therapeutic application, including batch preparation and standardized purification of exosomes, the efficiency of lncRNA-targeted delivery to cartilage tissue, as well as the unverified biosafety and long-term regulatory effects in vivo and in vitro. Consequently, the existing results cannot yet be directly translated into clinical treatment protocols. Further in-vivo animal experiments and preclinical mechanistic studies are still required to lay the foundation for future clinical translation.

Exosome-derived lncRNAs regulate osteogenesis-angiogenesis crosstalk in triggering bone remodeling

Bone remodeling is an ongoing metabolic activity that replaces bone tissue to heal injuries, responds to mechanical loads, and preserves skeletal integrity and mineral homeostasis. Osteogenesis is believed to be linked with angiogenesis [77]. Bone, which is highly calcified and vascularized, relies on its vasculature to supply ECs for growth. Osteoblasts release proangiogenic factors such as VEGF, which interact with VEGFR-expressing cells, including endothelial cells and osteoclasts, to regulate cell migration, proliferation, and angiogenesis [49]. Endothelial progenitor cells (EPCs) facilitate vasculogenesis during bone regeneration, indirectly supporting osteogenesis [78]. Exosomes regulate bone metabolism by modulating both bone formation and vascularization and originate from various cells in the bone microenvironment. EPCs enhance bone repair by promoting blood vessel development. Aging decreases the expression of CD31, PDGF, and PDGFRβ in vascular ECs, diminishing osteogenic capacity and causing bone mass loss [79, 80]. LncRNA TUG1 enhances EPC migration, invasion, and differentiation by upregulating VEGF expression. TUG1 acts as a ceRNA for miR-6321, thereby attenuating EPC migration and differentiation through posttranscriptional regulation of ATF2 [81]. Additionally, exosomes from ECs show notably greater targeting efficiency to bone tissue than those from osteoblasts or BMSCs. Mechanistically, miR-155, which is specifically enriched in EC exosomes, downregulates Socs1 gene expression, directly inducing osteoclast lineage differentiation and enhancing bone resorption activity [82]. The exosomal lncRNA NEAT1 from HUVECs promotes M2 polarization and reduces LPS-induced inflammation, while the resulting macrophage-conditioned medium indirectly enhances BMSC migration and osteogenic differentiation [83].

During bone development, angiogenesis and osteogenesis are tightly coordinated. The critical molecular networks that mediate intercellular crosstalk within the bone microenvironment—including exosomal signaling and cytokine cascades—remain underexplored, and their precise mechanistic roles require systematic investigation. Exosomal lncRNA-H19, identified in BMSC-Exos by Behera et al. [84], serves as a pivotal epigenetic regulator that orchestrates bone morphogenesis through tissue-restricted expression in osseous structures. They reported that the miR-106a seed sequence, which is capable of binding to H19, targets angiopoietin-1 (Angpt1). In vivo angiogenesis induction by BMSC-Exos was assessed in immune-deficient murine models, with concomitant monitoring of trabecular bone microarchitecture remodeling through quantitative micro-CT analysis. In vitro, BMSC-derived exosomes significantly enhanced both angiogenesis and osteogenesis. Through ceRNA-mediated regulation, exosomal H19 antagonizes miR-106 activity, leading to disinhibition of Angpt1 expression and increased angiogenesis. Angpt1 upregulation activates the exosomal lncRNA H19-mediated Tie2-NO signaling cascade in mesenchymal and ECs, potentiating their pro-osteogenic and proangiogenic activities. Furthermore, exosomes derived from BMSCs (BMSC-Exos) enhance bone formation and biomechanical properties in vivo. BMSC-Exo administration significantly enhances bone formation capacity and biomechanical properties in vivo through the lncRNA-H19/miR-106a/Angpt1-Tie2-NO signaling axis [84]. Bone repair involves osteoclast-mediated bone resorption coupled with EPC-induced neovascularization and osteogenesis. However, the molecular mechanisms by which EPCs regulate osteoclastogenesis remain elusive for an extended period. Studies on the regulation of bone repair by EPC-derived exosomes revealed that the lncRNA MALAT1 promotes osteoclast differentiation. In a murine fracture model, exosomes derived from EPCs markedly improved the recruitment of bone marrow-derived macrophages and their maturation into osteoclasts. Further investigations revealed that EPC-derived exosomes upregulated the expression of the lncRNA MALAT1, which interacts with miR-124 to negatively regulate its activity, thereby facilitating the migration and differentiation of BMMs [85]. The integrin ITGB1 plays a critical role in this process. Additionally, EPC-derived exosomes promote angiogenesis at the fracture site, accelerating bone healing. MALAT1 within EPC-derived exosomes functions as a pivotal effector molecule that enhances the migratory and differentiation capacity of osteoclast precursors, identifying a novel therapeutic target for bone repair [85]. Exosomal lncRNA-MALAT1 derived from EPCs mediates the recruitment and osteoclastic differentiation of precursors, contributing to bone regeneration processes [85].

Exosome-derived lncRNAs mediate the synergistic regulation of osteogenesis-angiogenesis through ceRNA networks and signaling pathway activation by modulating the biological behaviors of core cells including vascular endothelial cells, endothelial progenitor cells and BMSCs, and the molecular mechanisms involved in bone remodeling are illustrated in Fig. 5.

Fig. 5.

Exosome-derived lncRNAs mediate osteogenesis-angiogenesis crosstalk to coordinate bone remodeling. The figure illustrates the regulatory network of exosome-derived lncRNAs in orchestrating osteogenesis-angiogenesis coupling and osteoclast differentiation during bone remodeling. BMSC-derived exosomal lncRNA H19 acts as a ceRNA to sponge miR-106a, thereby activating the ANGPT/Tie2 signaling axis to promote both osteogenic differentiation and EC angiogenesis. EPC-derived exosomal lncRNA MALAT1 sequesters miR-124 to upregulate NFATc1, directly driving osteoclast differentiation, while also enhancing EC activation. In ECs, miR-155 further amplifies angiogenic signaling by targeting SOCS1, forming a feedback loop that supports osteoclastogenesis. Collectively, these exosomal lncRNAs coordinate osteogenesis, angiogenesis, and osteoclastogenesis, maintaining the dynamic balance of physiological bone remodeling. This figure was created with BioRender.com (https://biorender.com/).

Bone diseases

Owing to their stability, strong targeting ability, and low immunogenicity, exosomes can be used for the treatment of various diseases [86, 87]. Exosomes remodel the bone microenvironment by transporting specific molecules (such as miRNAs and lncRNAs), promoting osteoclast activation or inhibiting osteoblast function, and accelerating bone metastasis.

LncRNAs from exosomes modulate cancer-associated bone metastatic progression

Exosomes in tumors function similarly to scout troops, conducting pathfinding missions ahead of tumor cell metastasis. They remodel the tumor microenvironment before primary tumor cells influence future metastatic sites. For example, by activating oncogenic pathways in target cells, they facilitate tumor metastasis [88–91]. Advanced breast cancer is associated with a 65–75% risk of bone metastasis, prostate cancer 65–90%, and lung cancer 30–40%, collectively forming the epidemiological backbone of skeletal metastases. Exosome-derived lncRNAs participate in regulating the various pathways involved in bone metastasis in these cancers.

Exosomes, which potentially serve as novel biomarkers or therapeutic targets, hold significant promise in the treatment of bone metastasis in patients with breast cancer. Research on exosome-derived lncRNAs in this context highlights key regulatory pathways, including the miR-21/PDCD4, lncRNA-MIR193BHG/miR-489-3p/DNMT3A, and SNHG3/miR-1273 g-3p/BMP3 axes. As the predominant metastatic destination in breast cancer, bone tissue often exhibits pathological osteolysis or dysregulated osteogenic activity due to osteoclast dysfunction [92, 93]. Exosomes secreted by breast cancer cells encapsulate miR-21, a molecule that modulates osteoclastogenesis and functional activation through the suppression of PDCD4. Collectively, these mechanisms accelerate osseous metastasis and establish a premetastatic niche conducive to tumor colonization [91]. Tumor-derived exosomes transport lncRNA-MIR193BHG to osteoclasts, where it acts as a ceRNA by binding to miR-489-3p, thereby inhibiting its suppression of DNA methyltransferase 3A (DNMT3A). This activation of DNMT3A triggers gene methylation (silencing of the osteoclast inhibitor IRF8), upregulates key osteoclast differentiation genes (such as NFATc1 and CTSK), enhances osteoclast formation and bone-resorbing activity, and ultimately accelerates the vicious osteolytic cycle in breast cancer-induced bone metastasis [94]. Knockdown of exosomal lncRNA-MIR193BHG attenuates osteoclast differentiation and bone resorption experimentally, as this lncRNA operates via a ceRNA network: sequestering miR-489-3p to upregulate DNMT3A and fuel osteoclastogenesis [94]. Sun et al. [95] characterized the lncRNA SNHG3 in breast cancer bone metastasis. In BCa cells, SNHG3 overexpression increases the level of miR-1273 g-3p, which subsequently represses BMP3 expression in BMSCs. SNHG3 knockdown attenuated tumor cell proliferation and migration while upregulating OPG during osteoclast differentiation, identifying the SNHG3/miR-1273 g-3p/BMP3 axis as a promising therapeutic target.

The poor prognosis associated with lung cancer stems from its inherently aggressive biological behavior and frequent ability to metastasize to the skeletal system [93, 96]. Approximately 40% of non-small cell lung cancer (NSCLC) patients experience bone metastasis, with an average survival time of approximately six months [97]. In lung cancer patients with skeletal metastases, osteolytic lesions predominate (≈70% incidence) and commonly induce debilitating skeletal-related events (SREs), such as pathologic fractures, spinal cord compression, hypercalcemia, and intractable pain [98, 99]. MALAT1—initially linked to lung cancer metastasis [100]—is enriched in the serum exosomes of NSCLC patients. Zhang et al. [101] demonstrated its role in accelerating cancer migration and progression via antiapoptotic effects and cell cycle inhibition. Targeting exosomal MALAT1 can suppress DC-driven T-cell activation, suggesting new therapeutic approaches for autoimmune diseases. These findings indicate that exosomal MALAT1 acts as a liquid biopsy biomarker, with expression levels positively correlated with NSCLC stage, indicating high specificity for minimally invasive diagnosis.

Osteolytic bone metastasis (BoM) involves irregular osteoclast differentiation and dysfunction through the TGF-β/pTHrP/RANKL signaling pathway. In bone metastasis by tumors, cancer cells produce osteolytic agents such as CTGF, promoting the differentiation of osteoclast precursors derived from monocytes. Research has shown that lncRNAs are involved in this process [102]. Ni et al. [103] identified the role of lncRNA-SOX2OT-loaded exosomes in osteoclast polarization-mediated NSCLC bone metastasis, which is mechanistically linked to the miRNA-194-5p/RAC1 axis interaction and alterations in the TGF-β/pTHrP/RANKL pathway. Elevated HOTAIR expression represses osteogenic differentiation through miR-138 downregulation. Zhang et al. [104] demonstrated that exosomal HOTAIR from lung cancer cells regulates bone resorption and that its knockout in these exosomes mitigates bone mass loss. Compared with normal fibroblast exosomes, oncogenic exosomes from lung adenocarcinoma cells (A549/H1299) carry increased amounts of HOTAIR cargo. When engineered to overexpress HOTAIR, these vesicles promote osteoclast maturation and preferentially accumulate in bone microenvironments to disrupt anabolic processes. Molecular dissection revealed that the TGF-β/PTHrP/RANKL pathway is the critical effector of HOTAIR-mediated osteolytic destruction [105]. Thus, lncRNA-HOTAIR holds immense potential as a therapeutic biomarker for the targeted delivery of small molecules to bone tissue [104].

Prostate cancer (PCa) commonly presents with bone metastasis. Research indicates that exosomes from PCa cells are rich in the lncRNA NEAT1, which promotes osteogenic differentiation in hBMSCs. NEAT1 functions as a ceRNA for miR-205-5p, influencing the SFPQ/PTBP2 axis to upregulate RUNX2, which in turn enhances alkaline phosphatase activity, mineralization, and bone-related gene expression. In vivo studies confirmed that exosomal NEAT1 from PCa promotes osteogenic differentiation in hBMSCs, suggesting a potential target for treating PCa bone metastasis [106].

Exosome-derived lncRNAs promote tumor proliferation, invasion, and metastasis by regulating intercellular communication within the tumor microenvironment

Osteosarcoma (OS), the most common primary malignant bone tumor excluding marrow-origin malignancies, predominantly occurs in the metaphyseal regions of long bones, particularly near the knee joint, and has a significant incidence rate globally [107, 108]. Current research emphasizes angiogenesis as a critical driver of OS progression, characterized by dysregulation of proangiogenic and antiangiogenic mediators that coordinately modulate tumor cell proliferation, migration, and metastatic dissemination [109]. LINC00265 potentially enhances OS proliferation, migration, invasion, and angiogenesis by targeting the miR-382-5p/SAT1 and miR-382-5p/VAV3 pathways [110]. LOC100129620 facilitates angiogenesis and macrophage polarization. The LOC100129620/miR-335-3p/CDK6 signaling pathway enhances osteosarcoma metastasis by influencing cell proliferation, angiogenesis, and macrophage polarization [111].

Clinically, elevated XIST expression is correlated with advanced Enneking stage and metastasis in osteosarcoma, suggesting that it is a molecular driver of disease progression [112–116]. EWSAT1 promotes angiogenesis in the OS tumor microenvironment through exosomes, exhibiting a "dual additive effect," enhancing the sensitivity of ECs while upregulating angiogenic factor expression. In vivo experiments have shown that silencing EWSAT1 significantly inhibits tumor growth, suggesting that EWSAT1 and exosomes are novel targets for OS diagnosis and treatment [117]. Moreover, BMSCs can be recruited to OS tissues and influence progression by secreting exosomes. Mechanistically, exosomal XIST from BMSCs suppresses the ability of miR-655 to derepress ACLY expression, thereby triggering lipid accumulation and β-catenin stabilization—phenotypes that are reversible upon miR-655 overexpression. Additionally, animal studies confirmed that exosome-derived XIST from BMSCs promoted OS growth and lung metastasis through interactions with miR-655. Mechanistic studies revealed that BMSC-derived exosomal XIST, alongside miR-655, increases ACLY protein levels, resulting in lipid accumulation and activation of the β-catenin signaling pathway, thereby increasing OS cell proliferation, migration, and invasion [118]. By sponging miR-29a (which targets NFIA), the lncRNA LIFR-AS1 in macrophage-derived exosomes promotes OS progression. Depleting exosomal LIFR-AS1 inhibits these oncogenic effects, but miR-29a blockade rescues exosome functionality [119]. The macrophage-derived exosomal lncRNA LIFR-AS1 enhances osteosarcoma cell proliferation and invasion and inhibits apoptosis via the miR-29a/NFIA pathway, suggesting its potential as a novel therapeutic target for osteosarcoma treatment [119].

Exosome-derived lncRNAs regulate chondrocyte metabolism and the inflammatory response in joint degeneration

Osteoarthritis (OA) is a degenerative joint disease and a major cause of disability in adults. Articular cartilage degradation is a hallmark of osteoarthritis, with chondrocytes being the sole cell type in this tissue. Research has revealed a significant increase in apoptotic cells in both early- and late-stage OA cartilage compared with normal cartilage [120]. Increasing evidence suggests that exosomes have significant therapeutic effects on OA. First, exosomes primarily exert therapeutic effects by regulating chondrocyte proliferation and apoptosis. Mechanistically, BMSC-Exos rescue IL-1β-impaired chondrocyte motility and growth by normalizing TGF-β‒PCNA axis activity and inhibiting caspase-3 proteolysis [121]. Exosomes enhance extracellular matrix (ECM) synthesis and prevent its degradation in chondrocytes. The ECM of cartilage, which accounts for 95% of the cartilage, is a complex network consisting of proteoglycans, collagen, water, minerals, and fibrin, providing biomechanical properties to the cartilage. An imbalance in ECM synthesis and degradation by chondrocytes results in increased ECM breakdown, a crucial factor in OA onset and progression [122, 123]. Wang et al. [124] demonstrated the dual regulatory role of embryo MSC-exosomes: increasing anabolic collagen II while blocking catabolic ADAMTS5 to counteract IL-1β-induced phenotypic loss in osteoarthritic chondrocytes. Joint cavity injection of embryo-derived MSC-Exos effectively prevented cartilage damage progression in OA model mice, demonstrating that MSC-Exos balance ECM synthesis and degradation, exerting beneficial therapeutic effects in OA. Third, exosomes can repair damaged mitochondria in chondrocytes. OA chondrocytes experience mitochondrial dysfunction and loss of metabolic flexibility, which leads to increased apoptosis and reduced collagen II secretion [125]. Chen et al. [126] reported that BMSC-Exos provide mitochondrial proteins to restore the normal morphology of damaged mitochondria, inhibit ROS production, increase mitochondrial mass and DNA content, and restore mitochondrial function, thereby reestablishing chondrocyte metabolic synthesis.

Targeting miR-485-5p/FSP1 with exosomal SNHG7 represents a potential strategy to alleviate cytokine-induced chondrocyte degeneration [127]. BMSC-Exo treatment mitigated IL-1β-induced inflammation, oxidative stress, and ferroptosis in chondrocytes, with SNHG7 overexpression in BMSC-Exos amplifying these effects. Notably, silencing FSP1 in chondrocytes eliminated the beneficial effects of exosome-mediated SNHG7 [127]. BMSC-derived exosomes containing Lnc TUG1 may increase BLIMP1 expression, influencing the Th17 and Treg cell balance [128]. This mechanism ultimately reduces damage caused by rheumatoid arthritis (RA), suggesting that LncRNA TUG1-enriched BMSC-derived exosomes may be a potential therapeutic strategy for RA. The expression level of Hotair in blood monocytes and serum exosomes is significantly elevated in RA patients, promoting the migration of activated macrophages. The expression of Hotair is notably decreased in differentiated osteoclasts and rheumatoid synovial cells. Hotair overexpression significantly decreases MMP-2 and MMP-13 levels. This exploratory study provides new evidence suggesting that Hotair may be a potential biomarker for RA diagnosis [129].

Exosome-derived LncRNAs regulate multiple myeloma development

MM is a malignant plasma cell disorder characterized by bone resorption and immune suppression, resulting in skeletal lesions, anemia, hypercalcemia, renal dysfunction, and recurrent infections. MM cells induce bone resorption by activating osteoclasts and suppress bone formation by inhibiting osteoblasts. Exosomes are crucial in transmitting miRNAs, lncRNAs, and cytokines to interact with the TME. Studies have confirmed that exosomes contain unfolded proteins that block the interaction between the BiP protein, an endoplasmic reticulum molecular chaperone, and the transmembrane protein IRE1α, thereby inducing the phosphorylation of IRE1α and activating XBP1 miRNA and NFATc1 gene expression to promote osteoclast differentiation [130]. Exosome-derived AREG stimulates osteoclast proliferation by activating the EGFR pathway [131, 132]. Additionally, MM-derived exosomes downregulate Runx2, Osterix, and collagen 1α1 expression via DKK1, inducing osteoblast apoptosis [131, 133]. Blocking the transfer of exosome-derived DKK1 reduces bone resorption and improves patient prognosis. miR-129-5p is upregulated in MM exosomes and transferred to BMSCs, where it inhibits the transcription factor Sp1 and its target gene alkaline phosphatase, thus impeding osteoblast differentiation [134]. Exosome-derived miR-let-7c is involved in angiogenesis and is linked to MM progression. MSCs-derived exosomes promote macrophage polarization to the M2 phenotype, significantly advancing MM progression [135]. In addition to miRNAs, exosomes also secrete lncRNAs. In vitro studies demonstrated that the lncRNA RUNX2-AS1 suppresses RUNX2 expression, thereby hindering osteogenic differentiation. In BMSC-derived exosomes, miR-103a-3p expression is elevated, suppressing osteogenesis [136]. Despite the established role of exosomes in MM progression, their specific modulation of bone-destructive gene pathways remains poorly characterized. Song et al. [137] reported that exosomes derived from 5TGM1 cells lacking H19 significantly inhibited bone resorption and promoted osteogenesis in C57Bl6/KalwRij mice, increasing both osteoclast differentiation and osteoblast differentiation and thus promoting bone resorption activity. H19 interacts with hnRNPA2B1 and stabilizes BET proteins, promoting osteoclast differentiation and MM progression [137]. H19, a crucial element of exosomes in the bone marrow milieu, could serve as a therapeutic target for MM. Representative exosome-derived lncRNAs, their targets, associated bone-related diseases, and mechanisms of action are summarized in Table 1.

Table 1.

Exosome-derived lncRNAs play crucial roles in bone-related diseases through various mechanisms

LncRNA	Target	Associated disease/condition	Mechanism of action	Refs.
MIR193BHG	miR-489-3p/DNMT3A/IRF8/NFATc1/CTSK	Breast cancer bone metastasis	Osteoclast activation	[94]
SNHG3	miR-1273 g-3p/BMP3/OPG	Breast cancer bone metastasis	BMP3 suppression	[95]
MALAT1	–	NSCLC bone metastasis	Tumor progression/biomarker	[101]
SOX2OT	miR-194-5p/RAC1/TGF-β–PTHrP–RANKL	NSCLC bone metastasis	Osteoclast polarization	[103]
HOTAIR	miR-138/TGF-β–PTHrP–RANKL	Lung cancer bone metastasis	Osteogenesis inhibition	[104] [105]
NEAT1	miR-205-5p/SFPQ/PTBP2/RUNX2	Prostate cancer bone metastasis	RUNX2 upregulation	[106]
HOTAIR	–	Rheumatoid arthritis	MMP-2/13 downregulation	[129]
LINC00265	miR-382-5p/SAT1; miR-382-5p/VAV3	Osteosarcoma	Proliferation, migration, invasion, angiogenesis	[110]
LOC100129620	miR-335-3p/CDK6	Osteosarcoma	Angiogenesis, macrophage polarization	[111]
XIST	miR-655/ACLY	Osteosarcoma	Lipid accumulation, β-catenin activation	[118]
EWSAT1	–	Osteosarcoma	Angiogenesis promotion	[117]
LIFR-AS1	miR-29a/NFIA	Osteosarcoma	Proliferation, invasion, apoptosis inhibition	[119]
SNHG7	miR-485-5p/FSP1	Osteoarthritis	Inflammation, oxidative stress, ferroptosis inhibition	[127]
TUG1	BLIMP1	Rheumatoid arthritis	Th17/Treg balance	[128]
HOTAIR	MMP-2, MMP-13	Rheumatoid arthritis	Macrophage migration, MMP-2/13 downregulation	[129]
RUNX2-AS1	RUNX2	Multiple myeloma	Suppress osteogenic differentiation	[136]
H19	hnRNPA2B1/BET proteins	Multiple myeloma	Osteoclast differentiation, MM progression	[137]

This section systematically analyzes the regulatory roles of exosomal lncRNAs in four categories of bone-related diseases: tumor-associated bone metastasis, osteosarcoma, bone-joint degeneration, and multiple myeloma. By adopting a dual-dimensional framework of disease-specific molecular regulatory patterns and cross-disease core common pathways, we have clarified the functional principles of exosomal lncRNAs in the pathogenesis and progression of bone diseases. The distinction and connection between these two dimensions are clearly reflected across different disease subtypes.

Regarding disease-specific mechanisms, the regulation by exosomal lncRNAs exhibits marked target and effector specificity in distinct bone diseases. In tumor-associated bone metastasis: breast cancer bone metastasis relies on exosomal MIR193BHG to specifically activate osteoclast formation; non-small-cell lung cancer bone metastasis is mediated by exosomal SOX2OT, which promotes osteoclast polarization and initiates osteolytic damage; the core feature of prostate cancer bone metastasis is exosomal NEAT1 targeting the miR-205-5p/SFPQ/PTBP2 axis to specifically upregulate RUNX2, inducing osteoblastic metastasis-a clear contrast to the osteolytic metastasis observed in other tumors. In osteosarcoma, exosomal EWSAT1 specifically regulates vascular endothelial cell sensitivity and angiogenic factor expression through a “dual-superimposition effect,” serving as a unique regulatory factor for angiogenesis in osteosarcoma. In bone-joint degeneration, rheumatoid arthritis specifically depends on exosomal TUG1 to modulate BLIMP1-mediated Th17/Treg cell balance, while osteoarthritis involves exosomal SNHG7 specifically inhibiting chondrocyte ferroptosis and inflammatory responses via the miR-485-5p/FSP1 axis. The specific mechanism in multiple myeloma is exosomal H19 binding to hnRNPA2B1 to stabilize BET proteins, concurrently regulating osteoclast differentiation and myeloma cell proliferation, representing a unique molecular basis coupling bone damage with tumor progression in this disease.

Regarding cross-disease common regulatory pathways, exosomal lncRNAs exert conserved regulatory effects across different bone diseases through core signaling pathways and regulatory modes, constituting a shared molecular foundation for bone disease pathogenesis. First, the ceRNA molecular sponge mechanism is a universal regulatory mode for exosomal lncRNAs. For example, MIR193BHG in breast cancer bone metastasis, LIFR-AS1 in osteosarcoma, and SNHG7 in osteoarthritis all function by sequestering specific miRNAs to relieve their repression of target genes; this pattern spans all subtypes of neoplastic and degenerative bone diseases. Second, the RANKL-RANK-OPG osteoclast regulatory pathway is a common route for osteolytic bone damage. Breast cancer bone metastasis, lung cancer bone metastasis, and multiple myeloma all activate this pathway via exosomal lncRNAs to promote osteoclast differentiation and bone resorption. Third, the TGF-β signaling pathway serves as a cross-disease core regulatory axis. HOTAIR in lung cancer bone metastasis and MIR193BHG in breast cancer bone metastasis both modulate this pathway to remodel the bone microenvironment, while other core bone-homeostasis pathways such as Wnt/β-catenin and NF-Κb are also conservatively regulated by exosomal lncRNAs in different bone diseases. Fourth, angiogenesis regulation is a common feature of neoplastic bone diseases. Exosomal LINC00265 and EWSAT1 in osteosarcoma, as well as MALAT1 in lung cancer bone metastasis, all promote angiogenesis in the tumor microenvironment through exosome-mediated pathways, accelerating tumor proliferation and metastasis.

Summary and prospects

Exosomes are pivotal mediators of intercellular communication. Exosome-derived lncRNAs exert important influences on bone remodeling by regulating osteogenic differentiation of BMSCs, osteoclast activity, bone-vascular coupling, and the bone metastasis process in disease models. Consequently, exosome-derived lncRNAs have become a central research focus in the field of bone remodeling. Exosomal lncRNAs secreted by various cells in the bone microenvironment—such as BMSCs, osteoclasts, and vascular endothelial cells—can regulate the biological activities of osteoblasts, osteoclasts, and chondrocytes through mechanisms including ceRNA, epigenetic regulation, and key signaling pathways such as Wnt/β-catenin, TGF-β, and NF-κB. These processes establish a molecular foundation for maintaining bone homeostasis and are closely associated with the pathogenesis of multiple bone disorders, including osteoporosis, osteoarthritis, bone tumors, and tumor-associated bone metastasis, highlighting the considerable potential of exosomal lncRNAs for therapeutic applications in bone diseases.

Although significant progress has been made in elucidating the biological functions and regulatory mechanisms of exosomal lncRNAs in bone remodeling, several key limitations and unresolved challenges currently hinder deeper investigation and clinical translation. First, the lack of standardization in exosome isolation and characterization remains a major technical bottleneck. Existing methods—such as ultracentrifugation, size-exclusion chromatography, immunoaffinity capture, and commercial precipitation kits—yield exosomes with notable differences in yield, purity, and structural integrity. The cargo composition (including lncRNAs) of exosome populations isolated by different methods also varies substantially. Second, the ability to trace exosomal lncRNA delivery in vivo and monitor its functional dynamics is severely limited. While in vitro experiments have confirmed that exosomal lncRNAs mediate intercellular communication, the precise in vivo trafficking routes of exosomes, the efficiency of lncRNA delivery to target bone cells/tissues, and the spatiotemporal dynamics of lncRNA expression and the duration of regulatory effects after delivery remain unclear. The lack of highly specific, non-invasive, real-time in vivo tracking tools (e.g., optimized fluorescent labeling and imaging systems) for exosomal lncRNAs restricts accurate assessment of their biological activity and therapeutic efficacy in animal models of bone diseases. Third, the clinical translation of exosomal lncRNA-based therapies faces multiple serious challenges. These include low bioavailability and potential off-target effects of exosomal lncRNA delivery systems in vivo, the immunogenicity of heterologous cell-derived exosomes, and the difficulty of scaling up the production of GMP-compliant exosomes stably loaded with lncRNAs. Future research should prioritize addressing these limitations and challenges to accelerate the translation of exosomal lncRNA studies into clinical applications.

In summary, exosomal lncRNAs represent a novel and highly promising class of molecular targets for the diagnosis and treatment of bone-related diseases. By overcoming the current technical bottlenecks and clinical translation hurdles, therapeutic strategies based on exosomal lncRNAs are expected to provide innovative, precise, and effective approaches for the intervention of skeletal disorders.

Abbreviations

Angpt1

Angiopoietin-1

ApoBDs

Apoptotic bodies

BGNs

Bioactive glass nanoparticles

BMSC-Exos

BMSC-derived exosomes

BMSCs

Bone marrow mesenchymal stem cells

BoM

Bone metastasis

ceRNA

Competing endogenous RNA

CSF

Cerebrospinal fluid

DNMT3A

DNA methyltransferase 3A

ECM

Extracellular matrix

EPCs

Endothelial progenitor cells

EVs

Extracellular vesicles

H19

Imprinted maternally expressed gene H19

HOTAIR

HOX transcript antisense intergenic RNA

huBMSCs

Human bone marrow mesenchymal stem cells

hucMSCs

Human umbilical cord mesenchymal stem cells

IDD

Intervertebral disc degeneration

ISS

Idiopathic short stature

iOCL-exos

Inflammatory osteoclast-derived exosomes

LIFR-AS1

LIF receptor antisense RNA 1

LINC00265

Long intergenic noncoding RNA 265

LncRNA

Long noncoding RNA

MALAT1

Metastasis-associated lung adenocarcinoma transcript 1

METTL3

Methyltransferase-like 3

MM

Multiple myeloma

NEAT1

Nuclear paraspeckle assembly transcript 1

NLRP3

Nod-like receptor protein 3

NSCLC

Non-small cell lung cancer

OA

Osteoarthritis

OPG

Osteoprotegerin

OS

Osteosarcoma

PCa

Prostate cancer

PMOP

Postmenopausal osteoporosis / postmenopausal osteoporotic

RA

Rheumatoid arthritis

SNHG3

Small nucleolar RNA host gene 3

SNHG7

Small nucleolar RNA host gene 7

SOX2OT

SOX2 overlapping transcript

SREs

Skeletal-related events

TUG1

Taurine-upregulated gene 1

UMSCs

Umbilical mesenchymal stem cells

Author contributions

Z.L., Y.Y., and X.T. were responsible for the conceptualization, preparation, and revision of the manuscript; Preparation of the manuscript, S.Z., H.W., C.Z., C.Z., Z.S., X.L., Z.J., and C.W. All the authors reviewed and approved the final version of the manuscript for publication.

Funding

This study is supported by the National Natural Science Foundation of China (Grant No. 81901430), the Shandong Province Research and Development Plan (Grant No. 2017G006043), and the National Science and Technology Major Project of China-Major Project on Four Major Chronic Diseases (2024ZD0531803).

Data availability

Not applicable.

Declarations

Ethics approval and consent to participate

Not applicable.

Competing interests

The authors declare no competing interests.