Characterization of immortalized MSC. MSCs and Bmi-1/hTERT-immortalized MSCs were visualized (A) after the 2nd passage. The attached cells appeared fibroblast-like, spindle morphology (B) at the 40th passage (12 months after isolation). The MSCs (hMSC) and the TERT-transduced MSCs (hTERT-MSC), or the double TERT/Bmi-1 transduced MSCs (BMI/hTERT-MSC) were studied for cumulative population doubling level (PDL) (C). Flow cytometry analysis confirmed the presence of CD90/CD105 in primary MSCs after isolation (D) and in BMI/hTERT-MSCs (E). All cells were depleted of CD35/CD45 hematopoietic stem cell markers (F). The endogenous and exogenous expression of Bmi-1, TERT in all cell types were studied using quantitative real-time PCR (G). The expression of hepatocyte-selective genes (i.e., albumin (ALB), α-fetoprotein (AFP), cytokeratin18 (CK18), glucose-6-phosphate dehydrogenase (G6PD), hepatocyte nuclear factor (HNF-4α), and tyrosine aminotransferase (TAT)) of BMI/hTERT-MSC after hepatic differentiation was presented as fold change over the untreated MSCs in comparison with HepG2 and the primary hepatocyte (H).