Ectopic expression of telomerase enhances osteopontin and osteocalcin expression during osteogenic differentiation of human mesenchymal stem cells from elder donors

Age related bone loss is one of the most prevalent diseases in the elder population. The osteoblasts are the effectors cells of bone formation and regeneration. With the aging the osteoblasts become senescent reducing their ability to produce bone. Cellular replicative senescence is triggered by telomers shortening. Telomerase elongate the telomers length and maintain the cell proliferative capacity. Here, we demonstrated that the expression of human telomerase reverse transcriptase mediated by an adenovirus vector increases the levels of osteopontin and osteocalcin mRNA during the in vitro osteogenic differentiation of elderly human mesenchymal stem cells. Bone marrow human mesenchymal stem cells were obtained from old donors (>65 years) and induced to differentiate into osteoblasts for 14 days. The levels of mRNA of human telomerase reverse transcriptase, osteopontin and osteocalcin during the differentiation were assessed by semi-quantitative PCR before and during the differentiation on days 7 and 14. Infected cells showed 1.5 fold increase in telomerase expression. Also telomerized cells exhibit 1.5 fold increase in osteopontin and 0.5 fold increase in osteocalcin expression compared to primary osteoblasts isolated from the same donors. The transformed cells were not able to form tumours in NUDE mice.