Study on Telomerase Activity of Human Bone Marrow Mesenchymal Stem Cells.

Human mesenchymal stem cells(hMSCs) have multiple differentiate potential, and it can differentiate into adipocytes, osteogenic cells, chondrocyte and neural cells et al. It has been reported that telomerase activity in hMSCs is negative, but it is still controversial and telomerase activity in hMSCs-derived adipocytes has not been reported. We investigate the telomerase activity in hMSCs before and after their committed differentiation into adipocytes in vitro and cryopreservation. hMSCs were isolated from normal human bone marrow fellowed by cell culture in DMEM with low glucose containing 10% FBS. The FACS was performed to examine the expression of cell surface molecules and analyze cell cycle of primary hMSCs.Then some of hMSCs were induced to differentiate into adipocytes in vitro by being treated with adipocytic medium fellowed by being stained with oil red O, and the others were cryopreserved in liguid nitrogon for three months. TRAP assay(telomerase repeat amplification protocol assay)was employed to detect telomerase activity in those hMSCs. T293 cells and α-Interferon were analyzed with each test as an additional positive control and negative control respectively. Telomerase activity was expressed as a percentage of the relative telomerase activity (RTA) of the hMSCs relative to the RTA of T293 cells. The results indicated the cells were positive for SH2, SH3, CD90 and negative for CD34, CD45, AC133. It was showed that the majority of primary hMSCs(85%) was at cell cycle of G₀/G₁ phase and the minority of hMSCs was at S, G₂ or M phase. 80% hMSCs was orange adipocytes after they were treated with adipocytic medium for 3–4weeks. Telomerase activity was negative in hMSCs both at the beginning of culture and at the later stages during cell expansion,telomerase activity in hMSCs-passage 1–3(n=10) and hMSCs-passage 4–7(n=9) made no significant difference(1.46±0.83% vs 1.46±0.67%, p=0.99). Cryopreservation did not affect the telomerase activity in hMSCs. Telomerase activity in fresh hMSCs(n=13) and frozen hMSCs(n=6) made no significant difference(1.41±0.44% vs 1.51±1.07%, p=0.64). Telomerase activity in hMSCs-derived adipocytes(n=3) was significantly higher than in hMSCs(n=19)( 11.8±2.52% vs 1.46. ±0.67%, p<0.00001). It is concluded that hMSCs are telomerase-negative, and the stage of culture or cryopreservation does not affect their telomerase activity. After being induced to differentiated into adipocytes, hMSCs telomerase activity is upregulated.