Age is just a number? Your cells think so too.
- Myiesha Kumar
- Aug 13, 2025
- 4 min read
Aging is the irrefutable law of the universe-all living beings must move towards a state of progressive degeneration and eventually die.
Aging mechanisms, as research indicates, play a significant role in the development of diseases like cancer, cardiovascular abnormalities and Alzheimer's. As global healthcare standards advance, 2.1 billion individuals are expected to be older than 60 by 2050. In the absence of new medical and wellness paradigms, the world will experience an unsustainable burden of chronic disease that already extracts a significant social and economic toll.
But the million-dollar question is, why must all living organisms gradually decay and ultimately perish?
The answer lies deeply engraved in our cellular biology- our cells are a ticking time bomb, capable of dividing a set number of times before the destruction machinery of the body kicks in. What drives this? Telomeres.
Telomeres and Telomerase
Eukaryotic cell replication poses an innate problem- each cycle of replication leaves a small gap on one of the DNA strands which cannot be filled. Daughter chromosomes, as a result, will have shortened DNA molecules and may lose important genes- a problem that is greatly solved by telomeres.
Telomeres are repetitive DNA sequences combined with proteins (shelterins), found at the ends of eukaryotic chromosomes. They function as protective caps, preventing chromosome ends from degrading, sticking together, or fusing with other chromosomes, which would result in genomic instability.
Telomeres are maintained by the enzyme telomerase. It is a specialized enzyme that adds repetitive DNA sequences (e.g., TTAGGG in vertebrates) to the ends of telomeres that act as a template for telomere extension, counteracting the shortening that occurs during DNA replication.
However, most somatic cells have limited capacity to repair or extend telomeres, so once telomeres reach a critical length, cells undergo either senescence (growth arrest) or apoptosis (programmed cell death), considered a biological clock for aging. This limits the number of times a cell can divide- referred to as the Hayflick limit.
Role in Aging
Limiting telomere reserves serve as a roadblock to cellular immortalization, but the loss of telomere function coincides with both age-related decline in fitness and cancer-inducing genome instability. Telomere dysfunction has been described as one of the nine cellular and molecular hallmarks of aging (Lopez-Otin et al., 2013).
Stem cell exhaustion triggered by genomic instability, mitochondrial dysfunction that catalyses an increase in reactive oxygen species (ROS) and therefore, inflammation and loss of protein homeostasis are all aging mechanisms intimately linked with telomeres.
Role in age-related diseases
Numerous studies have implicated telomere dysfunction in age-related diseases. First, in high-proliferative tissues such as the skin, gastrointestinal tract, and hematopoietic system, low levels of telomerase in progenitor cell compartments and continual tissue renewal cause progressive telomere attrition over decades. This attrition ultimately triggers DNA damage responses such as cell cycle arrest, apoptosis, impaired differentiation, and/or senescence. Second, low-proliferative tissues such as the heart, brain, and liver could experience ROS-induced damage of telomere sequences, causing attrition and uncapping over time.
Research shows that in individuals carrying mutations in TERT and TERC (crucial protein components of a telomere), the severity of pathologies correlates with the abundance of short telomeres, so the onset of disease is anticipated with increasing generations (a phenomenon known as “genetic anticipation”).
The role of telomerase in cancer has been extensively studied. As telomeres shorten with age, genomes become unstable and tumour suppressor mechanisms are bypassed-a key initiation point for cancers. Subsequently, almost all human cancers present activation of telomerase as a mechanism to allow unlimited cell proliferation of tumour cells. Telomerase can stimulate tumour progression by ensuring maintenance of telomeres above a critically short length, thus preventing induction of cellular senescence or apoptosis
DDR: DNA Damage Response
In neurodegenerative diseases like Alzheimer’s, research indicates that telomere shortening is linked with loss in neuronal regenerative capacity, build-up of amyloid plaques (Aβ) and hyper-phosphorylated tau proteins- all major features of the disease.
Therapeutic Value and Future Prospectives
The link between telomere shortening and cellular senescence has catalysed interest in telomerase restoration therapy as a potential anti-aging strategy. Telomerase activation in adult or old mice by means of a gene therapy strategy was shown to be sufficient to improve metabolic fitness, neuromuscular capacity, and prevent bone loss, as well as significantly increase both median and maximum longevity, without increased cancer incidence.
Telomerase targeting (inhibitors and vaccines) is emerging as a major treatment approach for cancers as it can potentially limit cancer cell growth by inducing telomere shortening and triggering cellular senescence or apoptosis.
In Alzheimer’s Disease (AD), neurons treated with TERT were able to protect themselves from Aβ-induced apoptosis, neuronal damage from pathological proteins and alleviate memory impairment in an experimental model of AD. TERT may be a promising target for AD treatment and provide a new direction for research.
Conclusion
The link between telomeres and aging opens countless venues for the treatment of age related diseases like cancers and neurodegenerative diseases like Alzheimer’s and Parkinson’s. Research opportunities in this area are limitless and have unmeasurable potential in improving global health if harnessed effectively.
References
Chakravarti D, LaBella KA, DePinho RA. Telomeres: history, health, and hallmarks of aging. Cell [Internet]. 2021 Jan 1;184(2):306–22. Available from: https://pmc.ncbi.nlm.nih.gov/articles/PMC8081271/#S19De
Jesus BB, Blasco MA. Telomerase at the intersection of cancer and aging. Trends in Genetics [Internet]. 2013 Jul 19;29(9):513–20. Available from: https://pmc.ncbi.nlm.nih.gov/articles/PMC3896987/#S5
Yu X, Liu MM, Zheng CY, Liu YT, Wang Z, Wang ZY. Telomerase reverse transcriptase and neurodegenerative diseases. Frontiers in Immunology [Internet]. 2023 Mar 29;14. Available from: https://pmc.ncbi.nlm.nih.gov/articles/PMC10091515/#s3
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