Effects of extracellular matrix PDMS stiffness on proliferation and osteogenic differentiation of dental pulp stem cells

PURPOSE To investigate the effects of extracellular matrix stiffness on proliferation and osteogenic differentiation of dental pulp stem cells (DPSCs) in polydimethylsiloxane (PDMS)-based cell culture substrate model. METHODS The premolars removed during orthodontic treatment in Changzhou NO.2 People's Hospital were collected for DPSCs culture. PDMS matrix membranes were prepared, and divided into three groups according to the different stiffness degrees, group A (binder/hardener: 10∶1; 135 kPa), group B (binder/hardener: 20∶1; 54 kPa), and group C (binder/hardener: 30∶1; 16 kPa). Group free from PDMS was set as control group. Thereafter, DPSCs cells were cultured on PDMS matrix, and various indexes were detected. The proliferation rate of DPSCs was detected by CCK-8, the osteogenic differentiation of DPSCs was detected by alizarin red staining, and the protein expression levels of osteocalcin(OCN), RUNX2, Wnt1 and β-catenin were detected by Western blot. The data were processed with SPSS 22.0 software package. RESULTS Alizarin red staining showed that DPSCs cells in group A had obvious morphological changes, and the cell arrangement showed obvious orientation, its morphology gradually changed from polygon and spindle shape to square shape, and calcified nodules were also observed. The number of calcified nodules among four groups were the most in the group A, followed by group B and group C, which was the lowest in control group, with significant difference (P<0.05). The cell proliferation rate and the expression of OCN, RUNX2, Wnt1 and β-catenin were the highest in group A, followed by group B and group C, which was the lowest in control group, with significant difference(P<0.05). CONCLUSIONS The extracellular matrix with high stiffness may promote the proliferation and osteogenic differentiation of DPSCs by activating Wnt/β-catenin signaling pathway, which may provide a theoretical basis for periodontal tissue engineering.