Telomeres and Human Life: the Possibility to Wind Back Our Clock

Immortality. The distant hope that humans have pursued for centuries has long been confined to mythology, religion, and science fiction. From the elixirs sought by ancient emperors to modern anti-aging industries, the desire to overleap biological limits remains deeply rooted in human curiosity. In recent decades, however, this aspiration has begun to shift from imagination to scientific investigation.

At the center of this discussion lie telomeres and telomerase, microscopic structures within our cells that play a decisive role in regulating cellular aging and lifespan. By influencing how long cells can divide before they cease functioning, these components raise a provocative question: if aging occurs at the cellular level, could intervening in this process one day extend not only cell life, but human life itself?

1.     What are Telomeres?

      The beginning of this expedition takes place in a seemingly trivial point in our body: the telomere. Telomeres are structures made from DNA sequences that are found at the ends of chromosomes and act as “protective caps”. Their role is essential, as they prevent chromosomal deterioration and abnormal fusion events that are commonly associated with aging and cancer.

Source: SciTech Daily

To understand how cellular lifespan might be expanded, it is first necessary to address a fundamental question: why are humans mortal? The key lies in the length of telomeres. Every time cell division takes place – which is essential for the growth and repair of cells – in our body, the telomeres decrease in length by approximately 30 to 200 base pairs. Once telomeres reach a critically short length, the cell can no longer divide and instead enters senescence or programmed cell death (apoptosis). For this reason, telomeres are often described as a biological “clock” that reflects the replicative age of a cell.

            Suppose our body has lost its telomeres, with our DNA sequences being completely exposed. In this case, two major issues may arise, with the first problem being gene mutation. DNA polymerase – enzymes that build new DNA by adding nucleotides to an existing strand – do not replicate the very ends of the chromosome, known as the end-replication problem. As a result, every time DNA is replicated, small portions of it are lost during each replication cycle, leading to a loss of genetic information. Ultimately, this will engender genetic instability and increase the risk of mutations and diseases such as cancer. The second detrimental consequence is the disruption of cell division. Within the nucleus, there are multiple DNA-damage recognition and repair activity that occurs to preclude mutations. Without telomeres, chromosome ends would be repeatedly mistaken for DNA breaks, activating these repair pathways and preventing normal cell division.

Fortunately, our telomeres are safely attached to our DNA. Serving as a buffer against reaching nearby genes and protecting natural chromosome ends from being recognized as damaged DNA, telomeres are crucial for maintaining genomic stability and preventing catastrophic cellular outcomes

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2. Telomeres: Not the Worst, but Not the Best Guardians

Although telomeres serve as vital guardians of genetic material, they do so at a cost. With every round of cell division, telomeres themselves shorten, gradually losing their protective capacity, as indicated in the diagram below.

Source: The Wild Genes Group

Does this mean it is impossible to lengthen the telomere? Or extend cell life? The answer is not entirely negative. Cells possess two known mechanisms that can counteract telomere shortening. The first involves telomerase, an enzyme that adds telomeric repeat sequences to the ends of chromosomes, effectively replenishing lost DNA. The second is the Alternative Lengthening of Telomeres (ALT) mechanism, in which a shortened telomere uses a homologous telomeric sequence from another chromosome as a template for extension through recombination-based processes.

            However, a critical limitation remains. In most normal human somatic cells, telomerase activity is extremely low or absent, and ALT mechanisms are rarely active. As a result, natural telomere elongation is uncommon in healthy adult tissues. In contrast, high telomerase activity is frequently observed in stem cells and cancer cells, highlighting both the regenerative potential and the risks associated with telomere maintenance.

3. Telomerase Gene Therapy: Giving Cells a Second Chance

To tackle these issues, scientists have been researching telomerase gene therapy as a way to transiently restore telomerase activity in cells. Simply put, RNAs – the messengers that copy the genetic code of DNA to build proteins – are modified to contain the coding sequence for Telomerase Reverse Transcriptase (TERT), which is the component of telomerase. This is then expressed in stem cells and other somatic cells that normally exhibit little to no telomerase activity, allowing telomeres to be elongated and delaying the onset of cellular senescence.

(For a more advanced context, please proceed to read the following.)

Bernardes de Jesus et al. conducted a more specific experiment on this therapy. Researchers used gene therapy vectors – modified viruses that carry therapeutic genetic material – to deliver the telomerase reverse transcriptase gene (TERT) into cells. Specifically, they engineered a recombinant adeno-associated virus (rAAV) to carry the TERT gene, because rAAV vectors integrate into the host’s genome at very low rates and are less likely to cause harmful mutations. This makes them safer for therapeutic use.

Scientists selected a version of rAAV called AAV9, which can spread widely through the body and even cross the blood-brain barrier. They injected this AAV9 carrying the mouse TERT gene into adult mice through the bloodstream. Once inside the body, the viral vectors entered many different tissues and delivered the TERT gene into those cells. The introduced gene was then expressed, producing telomerase protein in cells that normally have little or no telomerase activity.

Source: Springer Nature Link

4. For Our Next Step

Immortality, for now, remains out of touch. While the presence of telomere and its potential to elongate is a major discovery, scientists are still left with the question of how the virus should be targeted to specific cells and which type of cell should be selected. What’s more, ethical concerns surrounding lifespan extension, such as fairness of access and the consequences of altering natural aging, remain unresolved. Still, telomere research has already shifted the conversation from simply prolonging life to understanding its biological limits, leaving us to reflect on not only how far science can go, but how far it should.

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Citations

Fernandez, Elizabeth. “Archive: Lifestyle Changes May Lengthen Telomeres, A Measure of Cell Aging.” University of California San Francisco, 14 Sept. 2013, www.ucsf.edu/news/2013/09/108886/lifestyle-changes-may-lengthen-telomeres-measure-cell-aging#:~:text=Diet%2C%20Meditation%2C%20Exercise%20Can%20Improve,Cell%20Aging%2C%20UCSF%20Scientists%20Report&text=A%20small%20pilot%20study%20shows,of%20chromosomes%20that%20affect%20aging.

Lee, Jenna, and Mark V. Pellegrini. “Biochemistry, Telomere and Telomerase.” StatPearls - NCBI Bookshelf, 11 Dec. 2022, www.ncbi.nlm.nih.gov/books/NBK576429/#:~:text=The%20main%20functions%20of%20a,DNA%2C%20and%20accidental%20DNA%20recombination.

Methodist, Houston. “Researchers develop technology to make aged cells younger.” Medical Xpress, 31 July 2017, medicalxpress.com/news/2017-07-technology-aged-cells-younger.html.

Ojiakor, Dika, PhD. “Gene Therapy Offers New Hope for Telomere Diseases.” Drug Discovery News, 6 May 2025, www.drugdiscoverynews.com/gene-therapy-offers-new-hope-for-telomere-diseases-16356.

Leiden University. “Can We Live Longer? Physicist’s Breakthrough Discovery in Genetic Protective Layer.” SciTechDaily, 18 Sept. 2022, scitechdaily.com/can-we-live-longer-physicists-breakthrough-discovery-in-genetic-protective-layer.

“Telomere Extension Turns Back Aging Clock in Cultured Human Cells, Study Finds.” News Center, 1 July 2025, med.stanford.edu/news/all-news/2015/01/telomere-extension-turns-back-aging-clock-in-cultured-cells.html.

“Telomere Length, Environmental Factors and Return Rate in Migratory Birds.” The Wild Genes Group, 18 Feb. 2015, wildgenesgroup.com/telomere-length-environmental-factors-and-return-rate-in-migratory-birds.

Boccardi, Virginia, and Utz Herbig. “Telomerase Gene Therapy: A Novel Approach to Combat Aging.” EMBO Molecular Medicine, vol. 4, no. 8, May 2012, pp. 685–87. https://doi.org/10.1002/emmm.201200246.