Reversing coma by senolytics and stem cells: the future is now

Abstract

Global cerebral ischemia (GCI) caused by impaired blood flow to the brain—typically following cardiac arrest or traumatic brain injury—remains the leading cause of coma and disorders of consciousness (DoC). In certain cases, the recovery potential of these patients may be significantly underestimated. Historically, these patients were often given little hope for recovery, particularly due to longstanding, outdated dogmatic views such as the presumed absence of adult neurogenesis. However, recent advances suggest that we have been discounting ongoing mental activity in comatose patients; additionally, emerging evidence shows that some patients in coma retain the capacity for communication through non-traditional means. The authors believe that the exponential progress in the field and the increase of our understanding in neurophysiology, regenerative medicine, and the biology of cellular senescence now makes it plausible to initiate experimental interventions that offer a realistic chance of reversing disorders of consciousness. The proposed strategy involves a two-step therapeutic paradigm: first the use of senolytic approaches to remove senescent cells and reduce neuroinflammatory burden (“clear the debris”); second, stimulation of neural regeneration through stem cell therapies, combined with electrophysiologic/pharmacological stimulation. The authors propose, that this integrated approach offers a novel treatment paradigm to address the previously insurmountable challenge of coma reversal.

Introduction

The classical definition of coma, established by Plum and Posner, define it as a state of deep unawareness where patients cannot be roused, lack a normal sleep–wake cycle, and having closed eyes [1]. As a medical emergency, coma often results in death or poor outcomes if not quickly identified and managed. It impacts individuals globally across all ages and social groups, but comprehensive worldwide epidemiological data on coma by diagnosis and setting remain unavailable. Coma is a significant medical disorder with approximately 200 per 100,000 individuals diagnosed with coma annually [2].

In many cases the initiation of coma results from cardiac arrest which leads to an immediate stop in cardiac output and oxygen supply to all vital organs. This no-flow state begins at the onset of cardiac arrest and persists until cardiopulmonary resuscitation (CPR) partially restores blood flow. Despite making up only 2% of body weight, the brain receives 15–20% of the heart’s output to maintain tissue stability [3]. The brain’s viability depends on a continuous supply of oxygen and glucose, and any cessation of cerebral blood flow (CBF) instantly disrupts brain activity. Human studies indicate that consciousness is lost within 4–10 s of absent CBF [4], and the electroencephalogram (EEG) becomes flat after 10–30 s of asystole [5].

Due to their lack of energy reserves, neurons are highly vulnerable to ischemia, with damage beginning immediately upon loss or reduction of CBF. At the cellular level, ischemia halts aerobic metabolism, rapidly depleting adenosine triphosphate (ATP) [6]. This ATP depletion disrupts the energy-dependent Na+/K + ion pump, causing a massive influx of sodium and water, resulting in cytotoxic edema. Potassium efflux and membrane depolarization occur soon after, leading to the opening of voltage-sensitive Ca + + channels and an influx of intracellular calcium. Experimental evidence shows signs of brain edema on MRI during cardiac arrest and resuscitation [7].

When CPR is initiated, CBF is partially restored (low-flow state), but it remains insufficient to preserve neuronal health, as CPR provides only about 25% of normal CBF, well below the 40–50% required to sustain cellular integrity and prevent further ischemic damage [3]. Upon achieving the return of spontaneous circulation, CBF is reestablished, but reperfusion of the ischemic cerebrovascular system initiates mechanisms that cause secondary brain injury [8]. The elevated intracellular Ca + + from the initial injury triggers the release of glutamate, an excitatory neurotransmitter that binds to cell membranes, causing additional Ca + + influx into the cytoplasm from the endoplasmic reticulum. This activates Ca++-dependent lytic enzymes (proteases, phospholipases), worsening neuronal damage. Ca++-induced mitochondrial dysfunction also occurs, leading to energy failure, release of pro-apoptotic proteins, and reactive oxygen species, further harming neurons [9].

Another aspect of reperfusion injury involves activation of the innate immune system and subsequent tissue inflammation. This process is driven by resident macrophages, known as microglia [10–13], and circulating leukocytes that adhere to endothelial cells in the cerebral microvasculature and infiltrate neuronal tissue [14]. Cytokines, as well as platelet activating factor [15], released by activated leukocytes amplify the inflammatory response. Increased blood–brain barrier permeability facilitates leukocyte migration and contributes to vasogenic edema [16–22].

Overall, brain injury caused by ischemia and the subsequent reperfusion has a particularly higher level of damage in specific brain areas. For example, the hippocampus, particularly the CA1 region [23], is among the most vulnerable, exhibiting delayed neuronal death 24–72 h post-reperfusion due to excitotoxicity from glutamate-mediated calcium overload, oxidative stress, and apoptosis [24, 25]. The cerebral cortex, especially pyramidal neurons in layers 3, 5, and 6, also sustains significant damage, with laminar necrosis and reperfusion-induced oxidative and inflammatory injury leading to deficits in cognitive, motor, and sensory functions [26]. The striatum, particularly the caudate-putamen, suffers rapid necrosis of medium spiny neurons driven by energy depletion and dopamine-related oxidative stress, impairing motor control and reward processing [27]. In the cerebellum, Purkinje cells are highly susceptible to calcium dysregulation and excitotoxicity, resulting in ataxia and coordination deficits following ischemic insult [28], this is particularly relevant in preterm birth [29, 30]. The thalamus, notably the reticular nucleus and relay nuclei, experiences neuronal loss and gliosis, disrupting sensory relay and attention, often secondary to cortical and hippocampal damage [31]. These regions’ selective vulnerability stems from mechanisms including excitotoxicity, ATP depletion, oxidative stress, and inflammation, which collectively drive neuronal death [32].

Coma patients still have functioning brains

Numerous studies have demonstrated that despite an outward appearance of unconsciousness, brain activity persists in many patients – sometimes including the capacity for thought and even responsive behavior like answering questions. In 2005, the medical community was stunned by a landmark study by Schiff et al., who described a 41-year-old woman with prolonged comatose unresponsiveness following traumatic brain injury, that was examined with functional magnetic resonance imaging (fMRI) to assess brain activity. Structural MRI revealed bilateral midbrain damage and ventriculomegaly; however, fMRI showed robust cortical responses to visual, auditory, and tactile stimuli. Notably, speech stimuli activated Broca’s and Wernicke’s areas—regions essential for language processing. Familiar voices and direct addressing elicited stronger activation of the amygdala compared to unfamiliar voices or neutral phrases, suggesting preserved emotional processing and responsiveness. This highly cited study notable for its pioneering use of fMRI in disorders of consciousness, demonstrates the potential for residual higher-order cortical functions in unresponsive patients. This underscores the value of functional neuroimaging for detecting covert consciousness and guiding clinical prognosis [33]. Essentially, this work proved that coma patients retain the ability to process stimuli and still have some meaningful responsiveness.

In a subsequent study along the same lines, Boly et al. performed positron emission tomography (PET) investigations to examine brain responses to noxious electrical stimulation in 15 patients in a persistent vegetative state (PVS) and 5 in a minimally conscious state (MCS), compared to healthy controls. In MCS patients, noxious stimulation activated the entire cortical pain matrix—including primary somatosensory cortex, thalamus, insula, frontoparietal, and anterior cingulate cortices—similar to comparable healthy individuals, with preserved functional connectivity between primary somatosensory cortex and associative cortices. In contrast, PVS patients showed only localized activation in the thalamus and primary somatosensory cortex and associative cortices, lacking higher-order cortical integration. This study demonstrates that MCS patients retain substantial capacity for pain processing, suggesting preserved sensory awareness, while PVS patients show limited responsiveness. These findings highlight the critical diagnostic and ethical importance of distinguishing between these states through advanced neuroimaging [34]. Importantly, this evidence suggests that coma patients can feel pain.

The most important was a study that coma patients can actually respond to outside stimuli. The seminal study by Owen et al. published in Science, fundamentally reshaped the understanding of brain function in patients diagnosed with vegetative state (VS) by demonstrating covert consciousness in a 23-year-old woman post-traumatic brain injury. Using functional magnetic resonance imaging (fMRI), the researchers instructed the patient to perform two mental imagery tasks—imagining playing tennis and navigating her home—which elicited specific brain activation patterns in the supplementary motor area and parahippocampal gyrus, respectively, mirroring those observed in healthy controls. These responses indicated the patient’s ability to follow commands willfully, despite exhibiting no overt behavioral signs of awareness, thus challenging the clinical diagnosis of VS. This highly cited study [35], underscored the potential for preserved cognitive function in some VS patients, highlighting the limitations of standard bedside assessments like the Glasgow Coma Scale and the need for advanced neuroimaging to detect residual awareness. The findings of Owen et al. have profound implications for the clinical management and ethical considerations surrounding comatose and VS patients. By demonstrating that some patients may retain covert consciousness undetectable by conventional methods, the study advocates for the routine integration of fMRI or similar neuroimaging techniques, such as EEG-based command-following paradigms, into diagnostic protocols to differentiate VS from minimally conscious states (MCS) or locked-in syndrome. This distinction is critical, as it informs prognosis and treatment decisions, potentially justifying continued life-sustaining interventions or rehabilitation efforts for patients with preserved cognitive capacity. Furthermore, the evidence of willful brain activity raises ethical questions about end-of-life decisions, emphasizing the need for caution in withdrawing care from patients who may be aware but unable to communicate. The study also gives the potential that neurorehabilitation strategies, such as regenerative medicine or brain-computer interfaces, to facilitate communication or recovery in such patients, urging clinicians to adopt a more nuanced, individualized approach to coma care that prioritizes detecting and nurturing residual brain function.

Senescence revolution as relates to brain injury

Senescent cells, characterized by irreversible cell cycle arrest and a distinct secretory phenotype, play a detrimental role in brain health by contributing to neuroinflammation, neurodegeneration, and cognitive decline. These cells accumulate with age or following stressors like ischemia, trauma, or oxidative damage, secreting pro-inflammatory cytokines, chemokines, and matrix-degrading enzymes collectively known as the senescence-associated secretory phenotype (SASP).

The “senescence revolution” was catalized by discoveries showing that these cells, express cell cycle arresting molecules such as p16^INK4a^ and p21^CIP1^, as well as SASP components and play an actively detrimental role in many chronic diseases [36–38]. A growing number of studies has shown that the reduction of senescent cell numbers, by administration of agents called “senolytics” results in improvement in pathologies including stroke [39–47], heart attack [48–55], heart failure [56–65], liver failure [66–88], kidney failure [89–101], multiple sclerosis [102–108], lower back pain (disc degeneration) [109–121], pulmonary dysfunction [122–126], radiation damage [127–129], and cancer [130–133].

In addition to their intrinsic dysfunction, senescent cells can propagate senescence to neighboring cells. This was elegantly illustrated in a study in which exploring the effects of transplanting aged (older) organs into younger recipients. In clinical organ transplantation, donor and recipient ages often differs significantly. Old donor organs with accumulated senescent cells have the capacity to induce senescence in naïve cells of host tissues. The authors of the study hypothesized that the engraftment of old organs may induce senescence in younger recipients, promoting age-related pathologies. When performing isogeneic cardiac transplants between age-mismatched C57BL/6 old donor (18 months) mice and young and middle-aged C57BL/6 (3- or 12- month-old) recipients, they observed augmented frequencies of senescent cells in draining lymph nodes, adipose tissue, livers, and hindlimb muscles 30 days after transplantation. These observations went along with compromised physical performance and impaired spatial learning and memory abilities. Systemic levels of the senescence-associated secretory phenotype factors, including mitochondrial DNA (mt-DNA), were elevated post-transplant in recipients. Notably, direct injections of mt-DNA recapitulated these aging phenotypes. A Single treatment of (old) donor animals with senolytics prior to transplantation attenuated mt-DNA release and improved physical capacities in young recipients. This study compellingly demonstrated, that senescent cells from (older) donor organs can induce systemic aging in recipients, while senolytic therapy can mitigate these effects [134].

In the brain, SASP components, such as interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α), disrupt the delicate balance of the neural microenvironment by promoting chronic inflammation that impairs neuronal signalling and synaptic plasticity. Senescent glial cells—including microglia and astrocytes—lose their neuroprotective functions and exacerbate neuroinflammation, contributing to diseases like Alzheimer’s (AD) and Parkinson’s (PD). For example, Bussian et al. [135] demonstrated that senescent glia drive tau pathology and cognitive deficits in tauopathy mouse models.

The accumulation of senescent cells also undermines brain health by impairing neurogenesis and vascular integrity. In the hippocampus, a region vital for learning and memory, senescent neural progenitor cells exhibit reduced proliferation and differentiation, limiting the brain’s regenerative capacity. Additionally, senescent endothelial cells in the cerebral vasculature compromise the blood-brain barrier (BBB), increasing permeability and allowing inflammatory mediators to infiltrate neural tissue, as demonstrated in studies of age-related cognitive decline [135]. This vascular dysfunction exacerbates ischemic damage and reduces cerebral blood flow, further stressing neurons already vulnerable to energy deficits. Moreover, senescent cells disrupt extracellular matrix remodeling, leading to amyloid-beta and tau accumulation in AD, creating a feedback loop that amplifies neurodegeneration. Collectively, these mechanisms illustrate how senescent cells act as a driver of brain aging and pathology, accelerating functional decline across multiple neurological domains.

Senolytics—drugs, that selectively eliminate senescent cells—offer a promising approach to mitigate these detrimental effects and to improve brain health. Compounds such as dasatinib and quercetin, or navitoclax, target anti-apoptotic pathways (e.g., Bcl-2 family proteins) upregulated in senescent cells, inducing their clearance without harming healthy cells. Preclinical studies in aged mice show that senolytic treatment reduces senescent cell burden in the brain, decreases neuroinflammation, and restores hippocampal neurogenesis, leading to improved cognitive performance in spatial memory tasks [136]. Similarly, in mouse models of AD, senolytics have been shown to reduce amyloid-beta plaques and tau pathology, alleviating memory deficits [137]. By clearing senescent glial and endothelial cells, senolytics restore BBB integrity, reduce SASP-mediated inflammation, and create a more favorable microenvironment for neuronal repair and synaptic function, offering a multifaceted approach to combating age-related brain dysfunction.

The clinical implications of senolytics for brain health are profound, though challenges remain in translating these findings to humans. Early-phase clinical trials, such as those exploring dasatinib and quercetin in age-related frailty, have shown reduced systemic senescent cell markers, suggesting potential applicability to brain health [138]. However, the brain’s unique complexity, including its limited regenerative capacity and the blood-brain barrier’s role in drug delivery, demands careful optimization of senolytic agents to ensure efficacy and safety. Off-target effects, such as transient inflammation from rapid senescent cell clearance, must also be addressed. Nevertheless, the ability of senolytic drugs to target a root cause of brain aging—senescent cell accumulation—positions them as a transformative strategy to counter neurodegenerative diseases and age-related cognitive decline. Continued research into brain-penetrant senolytics and combination therapies with anti-inflammatory or neurotrophic agents may enhance brain resilience against neurodegeneration and improve cognitive health and quality of life in aging populations.

Senolytic for treatment of global cerebral ischemia induced coma

A recent study by Gu et al. [139], investigated the role of senescent cells in brain injury following global cerebral ischemia (GCI) and evaluated the therapeutic potential of senolytics to promote brain regeneration and functional recovery in a mouse model. GCI, commonly resulting by cardiac arrest, causes widespread neuronal injury and can lead to coma through severe hypoxia and secondary inflammation. The study demonstrated that GCI induces senescence in glial cells (astrocytes and microglia) and endothelial cells, which secrete a senescence-associated secretory phenotype (SASP) composed of pro-inflammatory cytokines (e.g., IL-1β, TNF-α) and matrix metalloproteinases. This SASP exacerbates neuroinflammation, impairs the blood-brain barrier (BBB), and promotes neuronal death in vulnerable regions like the hippocampus and cortex, contributing to prolonged unconsciousness. By treatment with the senolytic drug navitoclax, the researchers demonstrated a significant reduction in senescent cell burden, which attenuated inflammation and preserved neuronal integrity, suggesting a potential pathway for brain regeneration post-GCI.

Senescent cells’ detrimental effects in GCI stem from their disruption of the neural microenvironment, as detailed in the study. Post-ischemic reperfusion leads to oxidative stress and DNA damage, prompting glial and endothelial cells to enter a senescent state. These cells release SASP factors that amplify excitotoxicity, disrupt synaptic plasticity, and impair neurogenesis, particularly in the hippocampal CA1 region, critical for memory and consciousness. The study found that senescent microglia fail to clear damaged neurons, while senescent astrocytes lose their neuroprotective functions, leading to a neurotoxic microenvironment that sustains coma. Additionally, senescent endothelial cells compromise BBB integrity, allowing inflammatory mediators to infiltrate and exacerbate secondary brain injury. Navitoclax treatment in the mouse model reduced these effects by clearing senescent cells, decreasing SASP-mediated inflammation, and restoring BBB function, which facilitated neuronal survival and synaptic repair, essential steps for post-GCI brain regeneration.

The application of senolytics like navitoclax offers a promising strategy for regenerating the brain and potentially reversing GCI-induced coma by targeting key drivers of neural inflammation and degeneration as evidenced by the study’s findings. In GCI mice, navitoclax administration post-ischemia reduced senescent cell markers (e.g., p16^INK4a, SA-β-gal) and SASP factors, leading to decreased microglial activation and cytokine levels. This created a more regenerative environment for neurogenesis and synaptic remodeling, with treated mice showing improved hippocampal neuron counts and enhanced performance in cognitive and motor tasks compared to controls. For coma patients these findings suggest that clearing senescent cells may alleviate inflammation in arousal-regulating circuits—such as the thalamocortical network—and facilitate the recovery of consciousness. The study’s observation of reduced tau pathology in treated mice further suggests that senolytics may mitigate protein aggregation, a common feature in post-ischemic brains that contributes to prolonged neurological deficits.

Endogenous stem cells are activated after global cerebral ischemia and contribute to recovery

The brain possesses a remarkable capacity for repair through the activation of endogenous neural stem cells (NSCs), primarily located in the subventricular zone (SVZ) of the lateral ventricles and the subgranular zone (SGZ) of the hippocampal dentate gyrus. Following GCI, hypoxic stress and subsequent reperfusion stimulate NSC proliferation as part of the brain’s intrinsic repair mechanism. Studies, such as those by Nakatomi et al. [140], demonstrate that ischemia upregulates growth factors like brain-derived neurotrophic factor (BDNF) and vascular endothelial growth factor (VEGF), which enhance NSC division and migration toward damaged areas. This proliferative response is driven by signaling pathways, including Notch and Wnt, which promote cell cycle re-entry and reactivation in quiescent NSCs. The increased NSC activity post-GCI represents a critical first step in regenerating lost neurons and restoring neural networks, offering hope for recovery from ischemic brain damage and associated neurological deficits.

The proliferation of endogenous NSCs after GCI is tightly regulated by the ischemic microenvironment. Hypoxia-inducible factor-1α (HIF-1α), activated during low oxygen conditions, induces the expression of erythropoietin and other trophic factors that stimulate NSC expansion in the SVZ and SGZ. Additionally, inflammatory cytokines, such as interleukin-6 (IL-6), released by reactive microglia and astrocytes, paradoxically have been shown to enhance NSC proliferation in the acute phase post-ischemia, as shown in rodent models [141]. These newly generated neural progenitor cells migrate to ischemic lesions, particularly in the hippocampus, cortex, and striatum, guided by chemokines like stromal cell-derived factor-1 (SDF-1). In the hippocampus, a region critical for memory and often severely affected in GCI, proliferating NSCs differentiate into immature neurons, contributing to the repopulation of the CA1 region, which is highly vulnerable to ischemic death. This migration and differentiation process is essential for rebuilding functional neural circuits and mitigating cognitive impairments observed in GCI survivors.

Endogenous stem cells contribute significantly to recovery from GCI by promoting both neurogenesis and angiogenesis, which together support brain repair. Newly formed neurons integrate into existing circuits, restoring synaptic connectivity and improving functional outcomes, such as memory and motor coordination. For instance, studies have shown that post-ischemic neurogenesis in the SGZ correlates with improved spatial learning in rats, suggesting a direct link between NSC activity and cognitive recovery. Concurrently, NSCs secrete angiogenic factors like VEGF, which stimulate blood vessel formation, enhancing cerebral blood flow and nutrient delivery to damaged areas [142]. This vascular repair is crucial for sustaining the metabolic demands of regenerating tissue and preventing further neuronal loss. In the context of GCI-induced coma, the restoration of hippocampal and cortical circuits through neurogenesis may facilitate the reactivation of arousal networks, potentially aiding in the recovery of consciousness by supporting thalamo-cortical connectivity.

Despite their potential, the contribution of endogenous NSCs to recovery is limited by several factors, including the hostile post-ischemic microenvironment. Chronic inflammation, oxidative stress, and glial scarring inhibit NSC survival and differentiation, reducing the efficiency of neurogenesis. For example, excessive SASP (senescence-associated secretory phenotype) from senescent glial cells, as noted in related studies, can suppress NSC function, highlighting the need to modulate the inflammatory milieu. Therapeutic strategies, such as the administration of growth factors (e.g., epidermal growth factor) or anti-inflammatory agents, have been shown to enhance NSC proliferation and improve outcomes in animal models [143]. In GCI-induced coma, augmenting endogenous NSC activity could accelerate brain repair, potentially shortening coma duration by restoring critical neural circuits. Combining these approaches with rehabilitation may further amplify functional recovery, addressing both motor and cognitive deficits in survivors.

Administration of exogenous mesenchymal stem cells for treatment of coma induced by global cerebral ischemia

Global cerebral ischemia (GCI), often resulting from cardiac arrest, causes widespread neuronal damage due to oxygen and glucose deprivation, frequently leading to coma and severe neurological deficits. Exogenous mesenchymal stem cells (MSCs), derived from sources like bone marrow, adipose tissue, or umbilical cord, have emerged as a promising therapeutic approach for GCI due to their broad-spectrum regenerative properties. MSCs are highly versatile, exhibiting anti-inflammatory, neuroprotective, and angiogenic effects that address the complex pathophysiology of ischemic brain injury. When administered post-GCI, MSCs migrate to damaged brain regions, guided by chemokines like stromal cell-derived factor-1 (SDF-1), and modulate the neuroinflammatory cascade. Studies demonstrate that MSC transplantation in rodent models of GCI reduces neuronal apoptosis in vulnerable areas like the hippocampus and cortex, promoting functional recovery. By mitigating secondary brain injury, MSCs create a conducive environment for neural repair, offering potential to improve outcomes in GCI-induced coma [144–146].

The primary mechanism by which MSCs aid GCI recovery is their potent immunomodulatory effect, which counters the neuroinflammatory storm that exacerbates ischemic damage. Following GCI, activated microglia and infiltrating immune cells release pro-inflammatory cytokines (e.g., TNF-α, IL-1β), worsening neuronal loss and prolonging coma. MSCs secrete anti-inflammatory factors, such as IL-10 and transforming growth factor-beta (TGF-β), which suppress microglial activation and shift the immune response toward an anti-inflammatory phenotype [147]. Research shows that intravenous MSC administration in rats post-GCI reduces pro-inflammatory cytokine levels and enhances M2 (anti-inflammatory) microglial polarization, preserving neuronal integrity in the CA1 region of the hippocampus. This reduction in inflammation not only limits secondary damage but also supports the survival of endogenous neural stem cells (NSCs), facilitating neurogenesis and synaptic repair. For coma patients, this anti-inflammatory action could stabilize arousal circuits, such as the thalamo-cortical network, increasing the likelihood of regaining consciousness [148].

Beyond immunomodulation, MSCs promote brain regeneration through paracrine signaling and angiogenesis, critical for restoring function after GCI. MSCs release trophic factors, including brain-derived neurotrophic factor (BDNF), vascular endothelial growth factor (VEGF), and nerve growth factor (NGF), which enhance neuronal survival, stimulate endogenous NSC proliferation, and promote synaptic plasticity. One study [149] found that MSC-derived VEGF in ischemic mouse models increased cerebral blood vessel density, improving blood flow to hypoxic regions and supporting metabolic recovery. This angiogenic effect is particularly relevant for coma recovery, as restored cerebral perfusion enhances the delivery of oxygen and nutrients to damaged areas, such as the cortex and brainstem, which are essential for consciousness. Additionally, MSC-secreted factors create a neurogenic niche that supports the integration of new neurons into damaged circuits, potentially aiding cognitive and motor recovery in GCI survivors.

The clinical potential of exogenous MSCs for GCI-induced coma is further enhanced by their ability to modulate the blood-brain barrier (BBB) and reduce secondary injury. GCI disrupts BBB integrity, allowing inflammatory mediators to infiltrate and exacerbate brain edema, which can prolong coma. MSCs stabilize the BBB by upregulating tight junction proteins and reducing matrix metalloproteinase activity, as demonstrated in preclinical studies. This protective effect minimizes vasogenic edema and limits further neuronal damage, creating a more favorable environment for recovery. Moreover, MSCs’ low immunogenicity allows allogeneic transplantation with minimal risk of rejection, making them a practical therapeutic option. Early-phase clinical trials, such as those for ischemic stroke, have shown that MSC therapy is safe and improves neurological outcomes, suggesting applicability to GCI. For coma patients, MSC administration could accelerate the restoration of neural networks critical for arousal, potentially shortening coma duration and improving long-term prognosis [150].

A practical plan for coma recovery: senolytic mediated cleaning followed by stimulation of regeneration

It is known that increased inflammation is associated with both, severity and duration of coma [151]. Neuroimaging (FDG-PET) and electroencephalography (EEG) demonstrate severely depressed brain metabolism but preserved islands of activity in frontal lobes, distinguishing prolonged coma from brain death. It is believed that chronic inflammation contributes to ongoing multilevel damage of the ascending reticular activating system (ARAS) thereby sustaining long term coma, with inflammation likely playing a role due to the traumatic and hypoxic insults [152].

The authors propose that the brain damage caused by the initial insult, together with sustained inflammation, leads to an acculumaltion of senescent cells in the microglia and astrocytes in the brain, particularly in the hippocampal areas as observerd in animal studies [139]. Indeed, there is supporting evidence for senescent cell accumulation in the brain of long term coma patients due to the higher level of SASP associated proteins found in the systemic circulation of long-term coma patients, including TNF-alpha [153]. Elevated SASP protein have been correlated with severity and length of coma [154].

Importantly, patients with lower SASP levels regained consciousness faster than those with higher levels.

We propose a conceptual treatment framework for patients with coma or persistent vegetative state in which assessment of senescent cell burden is quantified based on SASP production and quantification of senescent associated glial exosomes using sandwich ELISA, followed by administration of senolytic and regenerative therapies.

In the first treatment scenario immunization against senescent cells using the polyvalent senolytic immunotherapy SenoVax™ is proposed. SenoVax™ has been previously demonstrated to induced generation of senolytic antibodies which selectively kill senolytic cells and induce therapeutic effects in a preclinical lung cancer model [155]. Treatment efficacy can be assessed through reduction of SASP levels or restoration of regenerative molecules such as BDNF which are deficient in coma patients [156].

Once senescent cell burden has been reduced, various regenerative interventions are possible to restore critical regions of the brain such as ARAS which plays a central role in maintaining consciousness [157, 158]. Neurogenesis—mediated by endogenous progenitor cells—has been observed in various regions of the brain, and is hypothesized to be the key to recover from coma [159]. The ability of exogenous stem cells to active endogenous stem cells has been previously shown and established [160, 161]. As of today, conventional stem cell therapies face limitations as autologous stem cells are only available in limited quantities, while allogeneic stem cells carry the risk of immune rejection.

To overcome these barriers, the authors have developed a novel class of mesenchymal stem cells, termed “personalized mesenchymal stem cells” (pMSC) based on a new platform for cellular regeneration—StemcellRevivify™. The pMSCs are derived from autologous peripheral blood, dedifferentiated into personalized pluripotent stem cells, and subsequently re-differentiated into youthful pMSCs. This approach enables the generation of unlimited supply of autologous pMSCs, optimized for neuro-regenerative applications. .

We believe that by combining advances in senolytic therapies—such as our first-in-class SenoVax™ immunotherapy—as well as advanced regenerative technologies, such as our Stemcell Revivify™ pMSC platform, we can begin to address disorders of consciousness and facilitate the awakening and recovery of patients from long-term coma.

Author contributions

All the authors contributed to the conceptualization, discussion, writing and proof-reading the manuscript.

Funding

This work was supported by Immorta Bio Inc, a scientific longevity company holding patents on use of senolytics and regenerative medicine for treatment of coma.

Declarations

Ethics approval and consent to participate

Not applicable.

Consent for publication

All authors consent for publication.

Competing interests

TEI, RAR, AR, NEM, EL, GEI and BNR are affiliated with Immorta Bio Inc as management, shareholders and consultants. EJW Cofounder and Chief Scientific Officer of Ossium Health Inc.