The Function And Mechanism Of GIT1 On Chondrocyte Deffereniation In Bone Healing

ObjectiveTo study the function and mechanism of GIT1 on chondrocyte differeniation in bone healing process.Methods:We hypothesized that GIT1 was involved in bone healing process. In the present study, we used GIT1-/- murine to investigate its exact role in this process. The bonefracture models were established according to the Xie's method. The mice were divided into two groups (n=12/each group). The wild-type mice(GIT1+/+) were control group. The GIT1-/- mice were experimental group. X-ray and micro CT were obtained under anesthesia. The protein expression was detected by western blot. Collagen expression was detected by immunohistochemistry and cell apoptosis was checked with immunofluorence. Results:Our result showed that fracture healing was delayed in GIT1-/- mice compared to wild-type littermates (GIT1+/+). Alcian blue staining indicated an increased deposition of extracellular matrix (ECM) in day 14 callus samples from GIT1-/- mice.This finding was further consolidated by the immunohistochemical observation with increased type II collagen (Col-2) staining in callus from GIT1-/- mice. Callus samples from GIT1-/- mice showed an increase both in proliferation and apoptosis as evidenced by immunostaining with cell nuclear antigen (PCNA) and TUNEL labeling. In addition, the number of the tartrate resistant acid phosphatase (TRAP) positive osteoclasts was decreased in day 21 fracture samples in GIT1-/- mice.Conclusion:Our results indicate that GIT1 is closely involved in fracture healing mainly by regulating chondrocyte differentiation.