Brain‐derived neurotrophic factor (BDNF) has been reported to participate in fracture healing, whereas the mechanism is still unclear. Since osteoblast migration is important for fracture healing, investigating effects of BDNF on osteoblasts migration may help to reveal its mechanism. Here, MC3T3‐E1 cells were used in vitro while closed femur fracture mice were applied in vivo. Cells migration was assessed with Transwell assay. The protein expression was analysed by immunoblotting. X‐ray and Micro‐CT were performed at different time after fracture. Our results showed that BDNF promoted MC3T3‐E1 cells migration, integrin β1 expression and ERK1/2 and AKT phosphorylation. K252a, a specific inhibitor for TrkB, suppressed BDNF‐induced migration, integrin β1 expression and activation of ERK1/2 and AKT. PD98059 (an ERK1/2 inhibitor) and LY294002 (an AKT inhibitor) both inhibited BDNF‐induced migration and integrin β1 expression while integrin β1 blocking antibody only suppressed cell migration. X‐ray and Micro‐CT analyses showed that the adenoviral carried integrin β1 shRNA group had slower fracture healing at 7 and 21 days, but not 35 days compared to the control group. Thus, we proposed that BDNF stimulated MC3T3‐E1 cells migration by up‐regulating integrin β1 via TrkB mediated ERK1/2 and AKT signalling, and this may help to enhance the fracture healing.

BackgroundGIT1, a scaffold protein with ubiquitous multi-domain, is involved in many cellular processes. In recent years, it was proved that GIT1 participated in various tumors’ growth or metastasis. However, the biological function of GIT1 in osteosarcoma is still unclear. In this study, we aimed to investigate the role and mechanism of GIT1 in osteosarcoma.Materials and methodsHuman osteosarcoma tissues were obtained to investigate the distribution of GIT1. Adequate osteosarcoma cells were stably infected with lentivirus to knockdown GIT1 level and then was used to carry out cell invasion and vascular endothelial growth factor (VEGF) assay in vitro. Orthotopic femoral osteosarcoma model was constructed to investigate the growth, invasion, and angiogenesis in vivo. Western blot was used to detect extracellular signal-regulated kinase (ERK1/2) activation and hypoxia-inducible factor-1 (HIF-1α) expression.ResultsIn this study, we found that GIT1 was distributed in human osteosarcoma tissues and highly expressed in osteosarcoma (OS) cells. Knockdown of GIT1 inhibited cell invasion and VEGF release in vitro and suppressed tumor growth, invasion, and angiogenesis in vivo. Furthermore, knockdown of GIT1 substantially downregulated the protein levels of p-ERK and HIF-1α in OST cells and inhibition of p-ERK by PD98059 could significantly decrease the expression of HIF-1α and concentration of VEGF in GIT1-shRNA-treated cells.ConclusionGIT1 knockdown can effectively inhibit the growth, invasion, and angiogenesis of osteosarcoma. Thus, GIT1 might act as an oncogenic factor in osteosarcoma and could be a potential molecular target for osteosarcoma gene therapy.