| Osteoporosis is a disease characterized by breaking bone microarchitecture and low bone mass which lead to increased risk of fracture. With the advent of an aging society, osteoporosis has become a major threat to human health, especially to women. Reduced estrogen and exercise are common reasons of osteoporosis for postmenopausal women. However, currently there are few study of such phenomenon. So this paper will pay attention to cases which are caused by both estrogen deficiency and exercise reduce. In our experiment, we separately used four-month-old female SD rats as models of ovariectomy(OVX), hindlimb unloading(HLU),as well as ovariectomy combined with hindlimb unloading(OVX+HLU).Through comparing changes inproximal tibia of these models, we could explore the effect of lack of estrogen and mechanical unloading alone or in combination on bone mass and strength。The most serious complication of osteoporosis is osteoporotic fracture of hips, spine, wrist, ankle, etc. Reducing risk of fractures in these areas will greatly reduce the damage caused by osteoporosis. Studies have shown that mechanical stimulation can promote new bone formation, which could be used to treat osteoporosis. Extracorporeal shock wave(ESW) is a kind of sonic with mechanical properties as well as an effective mechanical stimulation. When the energy flux density(EFD) is suitable, ESW could promote new bone formation. So it is very suitable for local treatment of osteoporosis. In the experiment, we used four-month-old female SD rats to establish OVX+HLU osteoporosis model, so as to study the effects and mechanism of extracorporeal shock wave on the model.Part I The establishment and evaluation of osteoporosis modelsObjective: To establish OVX, HLU, OVX+HLU models and explore the changing of bone mass and strength caused by loss of estrogen, mechanical loading,or both.Methods: 24 4-month-old female SD rats were randomly divided into Control group, OVX group, HLU group, OVX+HLU group. Six rats per group. Rats in OVX group underwent ovariectomized, at the same time, rats in HLU group received tail suspension and rats in OVX + HLU group accepted both of the two actions. One month later all of the rats were sacrificed and their left tibias were collected with soft tissue removed. And then we used Micro-CT, Dual-energy X-ray absorptiometry and three-point bending test to observe the bone. The data were analyzed by SPSS 21.0 statistical software.Results: The Micro-CT showed that the value of BV/TV, Tb.N and Tb.Th of HLU + OVX group was the lowest in the four groups. Compared with the Control group, the value of BV/TV, Tb.N and Co.Th of HLU+OVX group decreased 43.15%(P<0.01), 36.91%(P<0.01) and 33.33%(P<0.05) respectively, and rabecular bone mineral density decreased 8.14%(P<0.01). Whereas no significant change was seen in Tb.Th value. Dual-energy X-ray absorptiometry results revealed that the BMD of HLU group, OVX group and OVX + HLU group decreased 20%(P<0.05), 24%(P<0.05), 32%(P<0.01) when compared with the Control group. Biomechanical test showed that the peak force of OVX+HLU group decreased 24.67%(P<0.05). In conclusion, HLU+OVX caused bone biomechanical performance degradation by reducing the number of trabecular bone and thinning the wall of the cortical bone.Conclusion: OVX + HLU is viable to establish osteoporosis model for female rat. The time needed for this model is one month.Part II Experimental study of unfocused extracorporeal shock waves on bone of osteoporotic ratsObjective: The aim of this study was to investigate whether unfocused extracorporeal shock waves affected bone micro-architecture of a osteoporotic rat model or not, which was established by ovariectomy(OVX) combined with hindlimb unloading(HLU).Methods: 18 4-month-old female SD rats were randomly divided into Control group, OVX+HLU group and ESW group. Six rats per group. Every rat in OVX+HLU group underwent ovariectomized as well as tail suspension. The rats in ESW group received ESW treatment after OVX+HLU. The ESW treatment(energyfluxdensity:3m J/mm2, frequency:5Hz, 1500 pulses) was applied to the hind leg of osteoporotic rats for four weeks and once per week. One month later all of the rats were sacrificed and the left tibias were collected with soft tissue removed. Then we used Micro-CT, Dual-energy X-ray absorptiometry, three-point bending test and scanning electron microscopy(SEM) to observe the bone. The data were analyzed by SPSS 21.0 statistical software.Results: When compared with OVX + HLU group, the value of BV/TV and Tb.N in ESW group increased by 25.47%(P<0.05) and 13.50%(P<0.05) respectively. OVX + HLU caused significantly decrease of BV/TV as well as trabecular number in rat tibia, whereas ESW could delay the decline extent obviously. But the value of Tb.Th, Co.Th, BMD and other indicators showed that there was no significant difference. SEM results showed that in the Control group, the trabecular connected with each other closely and network structure was integrity; while in the OVX+HLU group,the trabecular network structure was completely destroyed and trabecular number was reduced significantly. And the trabecular structure in the ESW group was partly destroyed. The quantity and integrity of trabecular was higher than OVX+HLU and lower than Control.Conclusions: Unfocused Extracorporeal shock wave could significantly improve relative trabecular bone volume and trabecular number in the OVX+HLU rats, thereby delaying the progression of osteoporosis. Therefore, Extracorporeal shock wave in the divergent treatment of osteoporosis has great potential. Unfocused ESW might be promising in the treatment of osteoporosis. |
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