Role of p38 MAPK in Odontogenic Differentiation of Dental Pulp Stem Cells in Hypoxia

The multipotent nature of dental pulp stem cells (DPSCs) promises regenerative endodontic potential. A specific microenvironment controls the differentiation capability of DPSCs. Oxygen is known as a crucial regulator in the microenvironment. Certain dentin matrix proteins may help to promote the p38 mitogen activated protein kinase (MAPK) pathway. Understanding this molecular signaling mechanism could aid in obtaining predictable clinical outcomes. The aim of this study is to examine the role of p38 MAPK under oxygen-deprived conditions to reveal its effect on odontogenic DPSC differentiation. Human DPSCs were isolated from healthy molars and cultured in basic and odontogenic media. The experimental group was treated with SB203580, a p38 inhibitor, under normoxic and hypoxic conditions. Immunocytochemistry and quantitative PCR analysis for various differentiation markers were performed. Our PCR data demonstrate that p38 MAPK inhibition in normoxic conditions results in a significant upregulation of odontogenic genes such as DMP-1, DSPP, RUNX2, and OSX. Under hypoxia, this effect was reversed. These results were also supported by DSPP immunocytochemistry. When p38 MAPK was inhibited, the DSPP expression under hypoxia was significantly weaker as compared to normoxia. Our results indicate that p38 MAPK constitutes a positive regulator of the odontogenic DPSC differentiation under hypoxia, demonstrating its essential role in designing for successful pulp-dentin complex regeneration engineering strategies.