Extracellular Heat Shock Protein 70 Promotes Osteogenesis Of Human Mesenchymal Stem Cells

Objective:To investigate the relationship between extracellular heat shock protein 70 and osteogenesis of human bone marrow mesenchymal stem cells.Methods:Human bone marrow mesenchymal stem cells (hMSCs) were cultured in osteogenic differentiation medium with different concentrations of heat shock protein 70 (HSP70). We used alkaline phosphatase (ALP) Viability and alizarin red staining to study whether HSP70 can affect osteogenic differentiation in early and late period. PCR and WB were used to detect the expression of osteogenic markers. Finally, microarray and pathway analyses were used to investigate the mechanism of HSP70 promoting osteogenic differentiation of hMSCs.Results:HSP70 significantly increased ALP activity and promoted hMSCs mineralization with time-dependent and dose-dependent manners. PCR results showed that HSP70 upregulated the expression of osteogenesis related genes RUNX2, OSX and ALP. WB results showed that HSP70 significantly upregulated the expression of SP7, ALP and BMP2. Microarray and pathway analyses indicated that ERK signaling pathway was closely related to the promoting osteogenesis of HSP70.Conclusion:HSP70 could promote osteogenesis of hMSCs through activation of the ERK signaling pathway.