RESUMO
Mesenchymal stem cells [MSCs] are presently isolated from various human tissues such as bone marrow. These cells have relatively high replication potential and can differentiate into various cell lineages with mesodermal and non-mesodermal origin and therefore, show promising in treatment of diseases. Their striking features like availability of source, ease of isolation and replication, and migration to lesions have made them appropriate for disease treatment and tissue engineering. The low frequency of MSCs in bone marrow necessitates their in-vitro expansion prior to clinical use. However, over-expansion may lead to aging or replicative senescence of MSCs and other complications for the patient. In this study, we isolated BM MSCs and cultured them in vitro. After the first passage cell surface markers were determined by flowcytometry and the cells propagated in culture for more passages. Telomere length was assessed using Telo TAGGG Telomere Length Assay kit after each cell passage. Our data showed that there is a direct correlation between in-vitro expansion of MSCs and reduction of telomere length. The telomere length was shortened by 1 kb after nine passages. This means that expansion induces aging through reduction of telomere length. These data suggest that in-vitro expansion of MSCs may restrict their future clinical application due to telomere length shortening which happens in each cell division. Thus, it would be much better to consider early passages of MSCs for cell and gene therapy due to their proliferation, differentiation and homing ability