Effect Of Calcitonin On Femoral Fracture Healing In Ovariectomized Rats

Objective : To study the effects and mechanism of calcitonin on osteoporotic fracture healing from treating rats with bilateral ovariectomy and femur fracture .Methods:Female SD rats of 12 weeks old were randomly divided into four groups of 10 animals each: Sham operation (Sham) group; Ovariectomized operation (OVX) group; Ovariectomy+fracture +saline Control (OVX+Fx+V) group; Ovariectomy+fracture +calcitonin (OVX+Fx+CT) group. All rats except Sham group received bilateral ovariectomy, Right midshaft femur facture model was estbalished 4 weeks after ovariectomy and fixed with intramedullary pin in OVX+Fx+V group and OVX+Fx+ CT group . Calcitonin(16IU/kg) were injected subcutaneously in the neck once per two days in OVX+Fx+CT group,while those in OVX+Fx+V group was given equal volume of normal saline. Rats in Sham group and OVX group were killed 4 weeks after overiectomy/sham operation for femoral bone mineral density evaluation by dual-energy X-ray absorptiometry (DEXA). Right femurs in OVX+Fx+V group and OVX+Fx+CT group were harvested at the 3rd week after fracture.All samples were assessed by CR film, (DEXA) bone mineral density measurement, and then were decalcified for paraffin section, and stained with HE staining, TRAP staining, as well as BMP-2 and VEGF immunohistochemical staining.Results:1. Compared with Sham group, tBMD and mBMD of OVX group were decreased 4 weeks after ovariectomy(P<0.05), rats in OVX group gained more weight than those in Sham group (P<0.05).2. CR film and HE stain: At the 3rd week after fracture, cartilage bone callus was dominant in both OVX+Fx+CT group and OVX+Fx+V group, no continuous bone callus was observed, and fracture line showed clearly. New bone trabeculae arranged loosely and irregularly.3. TRAP stain:Positive expression of TRAP in OVX+Fx+CT group was weaker at the 3rd week after fracture than that in OVX+Fx+V group (P<0.05).4. BMD of right femur: tBMD,mBMD and dBMD in OVX+Fx+CT group were higher at the 3rd week after fracture than that in OVX+Fx+V group, but no significant differences existed between the two groups (P>0.05).5. Immunohistochemistry of BMP-2 and VEGF showed that no significant difference existed between OVX+Fx+CT group and OVX+Fx+V group at the 3rd week after fracture (P>0.05).Conclusions:1. The obvious inhibition effect of calcitonin on osteoclast cell at fracture cite in ovariectomized rat was supported by current study.2. Treatment of calcitonin(16IU/kg) couldn't significantly promote femoral fracture healing in ovariectomized rat.