The role of heme oxygenase-1 in the proliferation and odontoblastic differentiation of human dental pulp cells.

INTRODUCTION: It was recently reported that heme oxygenase-1 (HO-1) activity is related to stem cell differentiation; however, the involvement of HO-1 in pulp cell growth and differentiation has not been well explored. The purpose of this study was to investigate the role of HO-1 in the growth and differentiation of human dental pulp cells (HDPCs).

METHODS: We evaluated cell growth by MTT assay, mineralization by alizarin red staining, and differentiation marker mRNA expression by reverse transcriptase polymerase chain reaction.

RESULTS: HO-1 induction by cobaltic protoporphyrin IX (CoPP) in HDPCs increased cell growth and mineralization and up-regulated the messenger RNA expression of such odontoblastic markers as alkaline phosphatase, osteopontin, bone sialoprotein, dentin matrix protein-1, and dentin sialophosphoprotein. Carbon monoxide scavenger, iron chelator, HO-1 inhibitor, and HO-1 small interfering RNA (siRNA) attenuated HDPC growth and differentiation.

CONCLUSIONS: CoPP treatment results in dental pulp cell proliferation and odontoblast differentiation that appears partly mediated by HO-1. Our results suggest that odontoblastic differentiation and growth are positively regulated by HO-1 induction and negatively regulated by HO-1 inhibition. Thus, pharmacologic HO-1 induction might represent a potent therapeutic approach for pulp capping and the regeneration of HDPCs.