FIG. 1.

Phenotype and growth characteristics of human mesenchymal stem cell (hMSCs) and hMSC telomerase reverse transcriptase (TERT) cells. (A) Late-passage [P15(19)] hMSC TERT cells still exhibit the characteristic fibroblastic phenotype of early-passage (P3) hMSCs. (B) Mock-transduced hMSCs and hMSC TERT cells were serial passaged in cell culture, and the population-doubling level (PDL) was calculated at each passage number. At early passages [P2(6)–P7(11)], the PDLs are similar for the two cell lines, but after P8(12), hMSCs proliferate at a slower rate and ceased growth at P16(20) with a maximum PDL of 14. hMSC TERT cells continually proliferate even after PDL 70 [P40(44)].