Role of ILK/p38 pathway in mediating the enhanced osteogenic differentiation of bone marrow mesenchymal stem cells on amorphous carbon coating

Amorphous carbon (a-C) film is a promising candidate for metallic implant surface coatings to improve corrosion resistance and osteogenesis in vivo. However, the molecular mechanism of how the bioinert carbon can induce osteogenesis has not been elucidated yet. In the present study, an a-C film was deposited on a smooth pure titanium (Ti) implant surface (C-Ti) by a vacuum evaporator. The scanning electron microscopy (SEM) observation showed a homogeneous coating with dispersed granules on the C-Ti surface. Raman spectroscopy revealed the standard a-C shift bands. Rat bone marrow mesenchymal stem cells (MSCs) were cultured on different implant surfaces. In agreement with other publications, the C-Ti surface exhibited enhanced cell adhesion, proliferation and osteogenic differentiation. In addition, a western blot analysis of the mitogen-activated protein kinase (MAPK) signaling pathways revealed that only the p38 phosphorylation level was increased significantly on the C-Ti surface. Inhibition of p38 by SB203580 obliterated the enhanced osteogenic differentiation ability of the C-Ti surface. Furthermore, integrin-linked kinase (ILK) was significantly upregulated on the C-Ti surface during the initial three days. Specific knockdown of ILK by siRNA sharply decreased p38 phosphorylation and also resulted in reduced osteogenic differentiation on the C-Ti surface. Above all, our study indicates that the a-C coating is able to promote osteogenic differentiation of MSCs through the ILK/p38 signaling pathway.