Differential effects of p38 and Erk1/2 on the chondrogenic and osteogenic differentiation of dental pulp stem cells

Abstract

The extracellular signal-regulated protein kinase 1/2 (Erk1/2) and p38 mitogen‑activated protein‑kinase pathways serve important roles in the regulation of osteogenic and chondrogenic differentiation in mesenchymal stem cells (MSCs). However, the exact mechanism remains unclear, and the effect is controversial. In the present study, the effects of Erk1/2 and p38 on the osteogenic and chondrogenic differentiation of dental pulp stem cells (DPSCs) were compared in vitro. The results indicated that inhibition of Erk1/2 is able to enhance the osteogenic differentiation of DPSCs and inhibit chondrogenic differentiation, whereas inhibition of p38 demonstrated the opposite effect. When compared with previous studies, the present study further confirmed that Erk1/2 and p38 serve important, but complicated, roles in regulating the differentiation of MSCs. Different chemical and physical stimuli, cell types, culture methods, times of inhibitor administration and the dosage of the inhibitor may influence the effect of Erk1/2 and p38 on the differentiation of MSCs. The present study aims to better understand the mechanisms that control the differentiation of MSCs and may be helpful in creating more effective tissue regeneration.

Figure 1.

Features of DPSCs. (A) DPSCs direct outgrowth from dental pulp tissue explants. Magnification, ×40. (B) The colony formation of the P3 DPSCs was visualized by Giemsa staining. (C) Immunohistochemical staining results demonstrated that some DPSCs expressed the mesenchymal stem cell marker stromal cell antigen-1. Magnification, ×40. (D) P3 DPSCs present a sigmoidal growth curve. DPSCs, dental pulp stem cells; P3, third passage.

Figure 2.

Effect of Erk1/2 and p38 on the osteogenic differentiation of DPSCs. (A) The expression of Erk1/2, p-Erk1/2, p38 and p-p38 in DPSCs was detected by western blotting. The expression of (B) ALP and (C) Runx2 mRNAs in treated DPSCs was investigated using the reverse transcription-quantitative polymerase chain reaction. (D) ALP staining and (E) alizarin red staining of DPSCs. The data are presented as the mean ± standard deviation. *P<0.05, **P<0.01. Erk1/2, extracellular signal-regulated protein kinase 1/2; DPSCs, dental pulp stem cells; ALP, alkaline phosphatase; Runx2, Runt-related transcription factor 2; Dx, dexamethasone.

Figure 3.

Effect of Erk1/2 and p38 on the chondrogenic differentiation of DPSCs. The expression of (A) Sox9, (B) ACAN and (C) Col2 mRNAs in treated DPSCs was investigated using the reverse transcription-quantitative polymerase chain reaction. (D-G) The expression of Col2 in DPSCs pellets was detected by immunohistochemical staining. Scale=50 µm. The data are presented as the mean ± standard deviation. *P<0.05, **P<0.01. Erk, extracellular signal-regulated protein kinase; Sox9, SRY-box 9; ACAN, aggrecan; DPSCs, dental pulp stem cells; TGFβ, transforming growth factor β.