Effects Of Alendronate On Femoral Fracture Healing In Ovariectomized Rats

Objective: To investigate the effects and mechanism of alendronate on osteoporotic fracture healing based on the establishment of ovariectomized rats model, using the histology, immunohistochemistry and other experimental methods.Methods:1. Establishment of an animal model of osteoporotic fracture: Thirty 3-month female SD rats of 260 to 300 grams were randomly divided into 3 groups of 10 animals each: Sham group, OVX group, and ALN group. ALN group and OVX group received bilateral ovariectomy. Fracture model was established on the middle of the right femur by an opening operation 4 weeks later.2. Administation method: After the operation of the fracture,Rats in ALN group and OVX group received injection subcutaneously of 30ug /(kg·week) of Alendronate or saline separately ,all rats were sacrificed 3weeks later.3. Observation and determination: NORLAND EXCELL dual-energy X-ray absorption test was applied to Sham and OVX rats for right femur BMD four weeks after Sham/ovarectomy and to OVX and ALN group for right femur BMD three weeks after fracture operation.3.2 Imaging Observation: Computer X-ray camera meter (DR) was appled to OVX and ALN rats 3 weeks after fracture operation.3.3 Histological observation:The callus specimens were excised from the 3 weeks after fracture, and were stained in HE and TRAP stain to observe the histological changes of cells in the callus.3.4 Immunohistochemical observation: test the expression of BMP-2,VEGF in the callus at the 3 weeks, using S-P method,and analyze with HPIAS-1000 system.Result:1. BMD measurement: Compared to Sham rats ,the BMD of the right femur decreased in OVX rats, (P<0.01), which demonstrated the animal model of osteoporosis was established successfully. As compared with the OVX group, the tBMD and dBMD of femur in ALN group increased significantly(P<0.01). 2. Imaging observation: Three weeks after fracture, the change of radiation in both groups is similar. There is fusiform-like callus around the fracture,but the fracture line is clear. 3. HE staining:At 3 weeks,there is cartilage callus instead of fibrous callus, and early cartilage island in fibrous callus in both groups, and there is newborn trabecular around cartilage island, and the chondrocytes in ALN group is more than OVX group (P<0.05). 4. TRAP staining:There is less osteoclast in ALN group,while the osteoclast in ALN group is larger and more nuclei than those of OVX group(p<0.05). 5. Immunohistochemical staining: At 3 weeks,the positive expression of BMP-2 in ALN group is lower, and VEGF in ALN group is higher than those in OVX group.(P>0.05)Conclusion: Alendronate(30ug /kg·week) for three weeks do not have significiantly effect on fracture healing in ovariectomied rats, though with a larger callus and higher BMD, which may be partially because of the inhibition of alendronate on osteoclast activity.