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Telomere Attrition and Autophagy-Associated Cell Death

Progressive telomere shortening destabilizes chromosomes and can trigger cell death through autophagy. This process is mediated by DNA breakage, cytosolic DNA accumulation, and activation of the cGAS–STING pathway. Autophagy, typically a survival mechanism that clears damaged cellular components, under certain stress conditions becomes a driver of cell death. Experimental models using human fibroblasts and epithelial cells with impaired RB and p53 pathways revealed that cells bypass senescence but succumb to telomere crisis through autophagy. Notably, suppression of autophagy allowed these cells to evade the crisis and continue proliferating, highlighting the dual role of autophagy in both protection and cell elimination. Furthermore, loss of telomere protection via TRF2 depletion independently activated autophagy, with chromosome fusions producing cytosolic DNA that amplified this effect.

Stem Cell Fate Alterations with Aging

Cardiac progenitor cells (CPCs) undergo profound changes with aging. Shortened telomeres activate p53, which in turn induces autophagy and promotes a shift from quiescence toward irreversible senescence. This results in stem cell exhaustion and reduced regenerative capacity. Experimental interventions that blunt telomere shortening, including TERT overexpression or pharmacologic inhibition of p53 and autophagy pathways, have been shown to restore proliferative potential and reverse aged CPC phenotypes.

Circadian Regulation of Telomerase

Telomerase activity and TERT expression follow circadian rhythms governed by CLOCK–BMAL1 heterodimers. Disruption of these circadian controls, such as in CLOCK-deficient mice or in physicians with irregular shift work, leads to impaired telomerase oscillation and accelerated telomere shortening. This identifies circadian rhythm as a key regulator of telomere dynamics, linking daily biological rhythms to genomic stability and aging processes.

Metabolic Influence on Telomere Dynamics

Nutrient metabolism strongly influences telomere regulation through energy-sensing pathways. Caloric restriction increases AMP and NAD levels, activating AMPK and SIRT1. SIRT1, in turn, reduces telomere attrition and promotes mitochondrial function by deacetylating PGC-1α. As a circadian regulator, PGC-1α coordinates energy metabolism and telomere protection. Conversely, oxidative stress in circadian rhythm-deficient states accelerates telomere shortening, contributing to premature aging.

Cardiovascular Consequences of Telomere Shortening

In the heart, telomere erosion limits cardiomyocyte proliferation and promotes hypertrophy, ventricular dilation, and progressive heart failure. Clinical studies associate short leukocyte telomeres with cardiovascular risk factors such as obesity, smoking, hypertension, and inactivity. Low telomerase activity has been detected in atherosclerotic plaques, correlating with instability and higher risks of myocardial infarction and stroke. Thus, telomere length serves as both a biomarker of cardiovascular health and a mechanistic contributor to heart disease.

Telomerase and Cardiac Regeneration

Therapeutic telomerase activation shows promise for cardiac repair. In experimental models, hTERT delivery enhanced pro-regenerative signaling in mesenchymal stem cells, improved cardiac fibroblast differentiation, and protected cardiomyocytes from apoptosis. Mitochondrial localization of TERT was particularly protective, enhancing vascularization and myocardial repair after ischemic injury.

Neuroprotection Through Telomerase Activity

Telomerase reactivation also shows benefits beyond telomere elongation in the nervous system. Introduction of TERT in Alzheimer’s models reduced amyloid beta accumulation, decreased neuroinflammation, improved neuronal health, and enhanced cognitive performance. Remarkably, these effects were partly independent of telomere length maintenance, indicating additional neuroprotective roles for TERT through SIRT1 activation and regulation of synaptic genes.

Neural Stem Cells and Age-Related Decline

In neural stem cell niches, telomere shortening impairs neurogenesis and neuronal differentiation. This dysfunction is largely mediated by p53, which cooperates with the Notch pathway to upregulate RhoA–Rock signaling, inhibiting neurite extension. Deletion of p53 rescues proliferative and differentiation deficits in telomerase-deficient models, underscoring p53 as a central checkpoint linking telomere dysfunction, neurogenesis, and stem cell aging.

Clinical Perspective

Telomeres function as guardians of genomic stability, yet their attrition drives aging-related processes across multiple organ systems. Autophagy, circadian regulation, metabolic pathways, and p53 signaling intersect with telomere biology to dictate cellular survival, regeneration, and disease progression. Therapeutic strategies that stabilize telomeres, modulate telomerase activity, or fine-tune autophagy hold promise for interventions in cardiovascular disease, neurodegeneration, and age-associated tissue decline.

REFERENCES

1. Yeh, J.-K., & Wang, C.-Y. (2016). Telomeres and Telomerase in Cardiovascular Diseases. Genes, 7(9), 58. https://doi.org/10.3390/genes7090058
2. Ablation of telomerase and telomere loss leads to cardiac dilatation and heart failure associated with p53 upregulation
3. Zlotorynski, E. Telomere crisis activates autophagic death. Nat Rev Mol Cell Biol 20, 133 (2019). https://doi.org/10.1038/s41580-019-0105-7
4. The circadian rhythm controls telomeres and telomerase activity
5. Le, T.Y.L., Pickett, H.A., Yang, A. et al. Enhanced cardiac repair by telomerase reverse transcriptase over-expression in human cardiac mesenchymal stromal cells. Sci Rep 9, 10579 (2019). https://doi.org/10.1038/s41598-019-47022-w

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