One of the clinicians’ major concerns is the biological safety of MSC. The critical question for clinical application of human MSC is their ability to undergo spontaneous malignant transformation in a recipient organism. The goal of our research was to study umbilical cord hMSC proliferative and differentiation capacities, karyotype stability, telomerase activity and telomere length, oncomarkers expression and tumorigenicity during long-term (6 months) cultivation ex vivo. Here we report on the establishing the primary culture of human umbilical cord MSC, MSC_0714, that was capable to proliferate ex vivo for up to 59 passages (6 months). During this period, the cells preserved their normal karyotype, morphology and MSC immunophenotype. Telomeres started to shorten only after the passage 20, while hTERT was inactive in these cells for the whole period of expansion. At the beginning of cultivation the number of SA-β-gal positive cells did not exceeded 3-5%, after the 22th passage their number started to increase and reached 49% at the passage 57. Thus, it was shown that MSC during long-term culture retain their characteristics and undergo cell senescence.

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