Nephronectin Stimulates the Differentiation of MDPC-23 Cells into an Odontoblast-like Phenotype.

INTRODUCTION: The present study investigated the in vitro effects of nephronectin (Npnt) on the proliferation, differentiation, and mineralization of a rat odontoblast-like cell line (MDPC-23 cells).

METHODS: MDPC-23 cells were cultured on Npnt-coated polystyrene or in the presence of soluble Npnt. Cell proliferation was analyzed using a Cell Counting Kit-8 kit (Dojindo, Kumamoto, Japan). Alkaline phosphatase (ALP) activity was quantified using an ALP activity assay. A reverse-transcription polymerase chain reaction was performed to evaluate the messenger RNA (mRNA) expression level of odontogenic markers and integrin(s). Alizarin red staining was conducted to quantify the calcium deposition.

RESULTS: Soluble Npnt had no adverse effect on the proliferation of MDPC-23 cells, but it exhibited concentration-dependent inhibitory activity toward differentiation. In contrast, coated Npnt promoted cell proliferation dramatically and significantly up-regulated the mRNA expression of odontogenesis-related genes; moreover, mRNA expression of integrin α1, α3, α5, β1, and β5 was found to be augmented. MDPC-23 cells cultured on Npnt-coated polystyrene displayed markedly higher ALP activity as early as day 3 after inoculation. In addition, mineralization was accelerated on Npnt-coated polystyrene.

CONCLUSIONS: Npnt in its immobilized form enhanced the proliferation of MDPC-23 cells and induced this odontoblastic precursor cell line to differentiate into a mineralizing phenotype.