Immortalization of human osteoblasts by transferring human telomerase reverse transcriptase gene.

In the current study, in order to establish an immortalized osteoblast cell line, human mesenchymal stem cells (hMSCs) had been inducted into osteoblasts directionally by an osteo-inductive conditioned medium, then the osteoblasts were steadily transduced by a retroviral vector containing human telomerase reverse transcriptase (hTERT) gene. The expression of hTERT, the telomerase activity, the telomere lengths, the tumorigenesis and the osteogenesis characteristics of transduced cells at different population doublings (PDs) and the primary normal human osteoblast (hOB) were identified. The results demonstrated that hTERT gene had been transferred into human osteoblasts successfully; the transduced cell line-clone5 expressed telomerase activity and divided vigorously and now have undergone more than 120 PDs; The telomere length of clone5 elongated and was stable; Different eras of clone5 (PD 40 and PD 88) both expressed bone-specific markers, such as alkaline phosphatase (ALP), collagen type I, and osteopontin. And the quantitative assay of ALP activity showed that there were no significant differences among untransduced cells, PD 40 and PD 88 clone5 cells. Furthermore, the immortalized cell line was benign in nude mice tumor formation and soft agar colony formation assay.