Hypoxia promotes mineralization of human dental pulp cells

Introduction

Dental pulp can be exposed to hypoxic conditions in case of trauma or inflammation. Dental pulp cells (DPCs) have mineralization potential, which plays a key role in pulp repair and reparative dentinogenesis process. Little information is available about DPC mineralization in hypoxic condition. The purpose of this study was to assess the influence of hypoxia on DPC mineralization to pave the way for a better understanding of dental pulp regeneration and reparative dentin formation.

Methods

Human DPCs were obtained by using tissue explant technique in vitro and cultured in normoxia (20% O₂) or hypoxia (5% O₂). Cell viability was investigated by methyl-thiazol-tetrazolium assay. Cell mineralization was assessed by von Kossa staining and alizarin red S staining. Important mineral genes such as osteocalcin (OCN), dentin matrix acidic phosphoprotein-1 (DMP-1), bone sialoprotein (BSP), and dentin sialophosphoprotein (DSPP) were determined by real-time polymerase chain reaction.

Results

Cell viability of DPCs increased more in hypoxia than in normoxia from day 3 to day 5. Von Kossa staining and alizarin red S staining showed DPCs in hypoxia had higher mineralization activity than in normoxia. Expression of mRNAs for OCN, DMP-1, BSP, and DSPP was greater in hypoxia than in normoxia.

Conclusions

These results imply that hypoxia promotes DPC mineralization.