Fibroblasts cellular aging

Telomeres play an important role in defining the replicative life span of cells, i.e., the maximal number of cell divisions or the so-called Hayflick limit. Normal human somatic cells, such as fibroblasts, after isolation ftom the body are only able to undergo a limited number of cell divisions, dependent on the age of the donor, before they stop cycling and go into the senescent state , which becomes manifest in phenotypic charges like cellular (lattenii and expression of a senescence-associated. alactosidase. Such cells ate arrested in G, which is different from quiescent cells, which arrest in Gq. After acquirir the senescent phenotype cells are still viable and can be maintained in culture for up to several months. The telomeres in fibroblasts shorten with each di ion due to the end-replication problem , because conventional DNA polymerases need a free 3 -hydroxyl toup lor DNA synthesis. This is usually provided by the activity of the polymerase o/ptimase complex, which synthesizes an initial RNA o%onucleotide primer. Durit strand synthesis, the most distally located primer... 

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