Masquelet's induced membrane promotes the osteogenic differentiation of bone marrow mesenchymal stem cells by activating the Smad and MAPK pathways

The Masquelet's induced membrane (IM) technique is widely used to treat large segmental bone defects due to its physical priority and biological function. However, the underlying molecular mechanism of the IM on bone formation remains unknown. In the present study, rat bone marrow-derived mesenchymal stem cells (BMSCs) were used as an in vitro model and bone morphogenetic protein 2 (BMP-2) was used as a positive control to evaluate the effects of the IM on the osteogenic differentiation of BMSCs. Although the IM group did not exhibit a significant increase in the expression of Runt-related transcription factor 2 (Runx2), Collagen I (Col I), osteocalcin (OCN) and alkaline phosphatase (ALP) relative to the BMP-2 administration, the IM was considerably effective compared with the untreated group. Mechanistically, we found that the IM activated the Smad and mitogen-activated protein kinase (MAPK) pathways, which was further confirmed by application of specific inhibitors of Smad1/5/8 (LDN-193189) and ERK1/2 (U0126). After the combined treatment of the IM and LDN-193189 as well as U0126, the IM-induced increase in Runx2, Col I, and OCN expression was significantly inhibited. These results suggest that IM promotes the osteogenic differentiation of rat BMSCs by activating the Smad1/5/8 and MAPK pathways.