BACKGROUND:Because of convenient source, multi-lineage differentiation and low immunogenicity, bone marrow mesenchymal stem cels are the ideal cel type to serve as vectors of transgenic cels in pain management. However, the replicative senescence and smal amount of cels obtained from the bone marrow restrict the application of bone marrow mesenchymal stem cels in pain research. OBJECTIVE:To construct human telomerase reverse transcriptase (hTERT)-immortalized rat bone marrow mesenchymal stem cels as transgenic celular vectors for pain therapy. METHODS:Bone marrow mesenchymal stem cels were obtained from whole rat bone marrow, and then transfected with a lentivirus containing the hTERT (pLV-Puro-EF1α-hTERT) folowed by puromycin selection. hTERT expression and telomerase activity in these transfected cels were determined by RT-PCR and TRAP. Morphological changes, capacity of cel growth and multi-lineage differentiation, chromosome karyotype and tumorigenicity were observed in vitro. Moreover, the expression of cel surface molecule, Nestin, MHC-I and MHC-II in transfected cels were also detected by flow cytometry and immunocytochemistry. RESULTS AND CONCLUSION: The bone marrow mesenchymal stem cels geneticaly modified by hTERT could be cultured and passaged through 30 generations in vitro. Compared to the primary and negative transfected cels, the hTERT-modified bone marrow mesenchymal stem cels showed higher expression of hTERT mRNA, telomerase activity and cel proliferation. Most of transfected cels stayed at G2/M and S stages. The proliferation index of the transfected cels were increased dramaticaly. The positive rates of CD29, CD44 and CD90 were over 70%, but the positive rates of CD34 and CD45 were less than 5%. Transfected cels were positive for Nestin in the cytoplasm, but negative for MHC-1 and MHC-11. In addition, this cel line continued to exhibit the characteristics of fibroblastic bone marrow mesenchymal stem cels, including phenotype, differentiation into osteoblasts, adipocytes and neuron-like cels. No chromosome abnormality and tumor formation were observed in this experiment. Taken together, these data suggests that the rat bone marrow mesenchymal stem cels immortalized by hTERT gene are constructed successfuly and stil maintain major stem cels characteristics, which provide safe and stable cel vectors as research base for pain therapy.