TELOMERE

Telomere attrition is a primary hallmark of aging and plays a key role in the development of various age-related diseases, including cardiovascular pathologies, idiopathic pulmonary fibrosis, and Alzheimer’s disease. Interestingly, shorter telomeres have also been linked to both female and male fertility, making telomere length a valuable biomarker candidate for personalized reproductive health diagnostics and treatments. Monitoring telomere length provides valuable insights into biological aging and the effectiveness of interventions to reduce, slow or reverse age-related diseases risk.

Telomeres, situated at the termini of eukaryotic cell chromosomes, are not just passive structures. They are active guardians of our genome stability and integrity. These protective caps, composed of non-coding DNA sequence repeats (3’-[TTAGGG]-5’) in tandem, with a G-rich single-stranded 3’-overhang, play a pivotal role in our health and lifespan. After each cell division, telomeres naturally shorten by 50-150 base pairs due to the 'End Replication Problem'. This shortening acts as a biological clock, limiting cell proliferation and leading to cell senescence and/or apoptosis. The implications of this process for human health and lifespan are profound.‍

Current technologies for telomere length analysis include telomere restriction fragment (TRF),  based on the Southern blot assay, quantitative polymerase chain reaction (qPCR), flow fluorescence in situ hybridization (flow-FISH) and quantitative FISH (qFISH). TRF is the only method to determine absolute telomere length, but the technique is time-consuming, requires a substantial amount of DNA, and overestimates telomere length due to the inclusion of subtelomeric regions in the total length. qPCR is the most used technique for basic and clinical research, as it is the simplest available solution, in addition it only requires small amounts of DNA samples for the analysis, but it has major limitations including low reproducibility, sensitivity and specificity. Flow-FISH, while efficient, demands expensive equipment, complex procedures and technically challenging systems preventing its scalability. In addition to the limitations that affect the precision, applicability and scalability in clinical settings of the above methods, their major downside is the impossibility of analyzing telomeres in single cells as they only permit their assessment in cells’ bulks. Due to such constraints, only samples’ average telomeres length can be measured which prevents access to major data that can only be collected if single cells are analyzed. This data includes the percentage of super short telomeres (senescence biomarker), telomere distribution (age related diseases signature), scoring of telomere loss, telomere deletion, telomere doublet formation etc.