Immortalization and characterization of human dental pulp cells with odontoblastic differentiation

Objective: To immortalize human dental pulp (HDP) cell showing stable growth and high mineralization activities in vitro. Design: HDP cells were obtained from a healthy third molar and immortalized by transfection with human telomerase transcriptase (hTERT) gene. To examine the characters of hTERT transfected HDP (HDP-hTERT) cells, we examined expression of mRNA for dentin sialophosphoprotein (DSSP), type I collagen (COLI), alkaline phosphatase (ALP) and bone sialoprotein (BSP) by RT-PCR. In addition, we examined ALP activity by biochemical method and nodule formation by alizarin red S (ALZ) staining. Results: HDP-hTERT was obtained by transfection. with hTERT gene. These cells bypassed the senescence and grew over 120 population doublings (PDLs) without significant growth retardation. High expression of hTERT was confirmed in HDP-hTERT by RT-PCR and showed remarkable telomerase activity. Both HDP-original (HDP-ori) and HDP-hTERT expressed DSSP, COLI, ALP and BSP mRNA and showed ALP activity and ALZ staining at the same levels. Conclusions: We were able to establish a cell line of immortalized human dental pulp cells with odontoblastic differentiation which will be a useful cell model for studying the mechanism of proliferation and differentiation of odontoblasts. (C) 2007 Elsevier Ltd. All rights reserved.