Stimulation of osteogenic protein expression for rat bone marrow stromal cells involved in the ERK signalling pathway by the ions released from Ca7Si2P2O16 bioceramics

Protein is the basis of biological and cellular functions. Ca7Si2P2O16 (CSP) is a new kind of bioceramic with excellent apatite-mineralization and osteostimulation properties; however, the osteogenic mechanism of CSP bioceramics is unclear. Especially, the effect of CSP on the osteogenic protein expression and its possible signaling pathway is unknown. In order to elucidate the possible osteogenic mechanism, the bone-related protein expressions of rat bone marrow stromal cells (rBMSCs) cultured with the bioceramic disk extracts were systematically studied, in which we mainly investigated whether the up-regulated osteogenic genes could be translated effectively to lead to the stimulation of the corresponding protein expressions at the protein level. In addition, the role of the ERK pathway in the process of osteogenic differentiation for rBMSCs was further explored. The results showed that calcium (Ca) and silicon (Si) ions released from the CSP ceramic could not only enhance cell viability and osteogenic gene expression of rBMSCs but more importantly, they significantly promoted the expression of RUNX2, ALP, OPN, COL1 and OCN proteins. Western blot results further indicated that the possible mechanism might involve the activation of the ERK/RUNX2 pathway. Moreover, the CSP ceramic-induced osteogenic protein expression was significantly inhibited by treatment with PD98059, a specific ERK inhibitor, which in turn inhibited the protein expression level of P-ERK1/2, RUNX2, OPN and COL1. In summary, our findings suggest that the bioactive ions from the Ca7Si2P2O16 ceramic are the main chemical signal for stimulating the bone-related protein synthesis of rBMSCs and the osteogenic differentiation of rBMSCs may be involved in the activation of the ERK signalling pathway.