去势手术联合激素注射对绵羊腰椎骨密度及微观结构的影响

Effect of ovariectomy combined with hormone injection on bone mineral density and microstructure in sheep lumbar vertebrae

目的评价去势手术联合激素注射对绵羊腰椎骨密度(bone mineral density,BMD)及微观结构的作用。方法将10只健康成年绵羊随机分为假手术组(n=5)和实验组(n=5)。假手术组仅显露双侧卵巢;实验组行双侧卵巢切除术(ovariectomy,OVX),且术后1月开始肌肉注射甲基强的松龙(0.45 mg/kg.d),注射时间共为10月。测量术前和术后1年两组中绵羊腰椎的BMD。术后1年,处死所有绵羊并取出绵羊腰椎标本,通过micro-CT技术对微观结构进行三维重建及空间参数的测量分析,通过组织学观察评价绵羊腰椎微观结构的病理改变。结果术前两组平均BMD之间的差异无统计学意义(P>0.05),假手术组手术前后的平均BMD无显著变化(P>0.05);术后1年实验组平均BMD显著下降(P<0.05),从术前的1.13±0.13 g/cm2下降为术后的0.83±0.11 g/cm2,平均下降26.5%,且术后1年实验组中平均BMD显著低于假手术组(P<0.05)。实验组的组织骨密度(TMD)、骨体积分数(BVF)、骨小梁厚度(Tb.Th)和骨小梁数目(Tb.N)均显著低于假手术组,差异均具有统计学意义(P<0.05);实验组的骨表面积体积比(BS/BV)和骨小梁间隙(Tb.Sp)均显著高于假手术组,差异均具有统计学意义(P<0.05)。三维重建及组织学观察发现:与假手术组相比,实验组中骨小梁数量减少,排列稀疏、骨小梁多处断裂,失去正常的髓腔结构。术后1年实验组中的骨组织微观结构显著差于假手术组。结论去势手术联合激素注射的方法可以显著降低绵羊腰椎的BMD,可以显著破坏绵羊腰椎的微观结构,显著降低绵羊腰椎的骨质条件。去势手术联合激素注射的方法可用于建立骨质疏松动物脊柱模型。

Objective To evaluate the effect of ovariectomy combined with hormone injection on bone mineral density （BMD） and microstructure in sheep lumbar vertebrae. Methods Ten healthy adult sheep were divided into sham group （n = 5 ） and experiment group （ n = 5 ） randomly. Both ovaries were exposed without any treatment in sham group. In experiment group, bilateral ovariectomy （OVX） was performed. One month after OVX, sheep were injected intramuscularly with methylprednisolone （0.45 mg/kg, d） , and the whole treatment lasted for 10 months. BMD of all sheep lumbar vertebrae was examined before surgery and 1 year after surgery. One year after surgery, all sheep were killed and all lumbar vertebrae samples were collected. Three dimensional reconstruction of mierostructure was performed and spatial parameters were examined using micro-CT technique. The pathological changes of sheep lumbar vertebrae were evaluated through histological observation. Results There was no significant difference of mean BMD between two groups before surgery （P 〉 0. 05） , and there was no significant difference of mean BMD between before and after surgery in sham group （P 〉 0.05）. There was significant decrease of mean BMD in experiment group before and one year after surgery （P 〈0. 05）. The BMD decreased from 1.13 ±0. 13 g/cm^2 before surgery to 0. 83 ± 0. 11 g/cm^2 one year after surgery, with 26.5% decrease. Furthermore, the mean BMD in experiment group was significantly lower than that in sham group one year after surgery （P 〈 0. 05 ）. Tissue mineral density （ TMD）, bone volume fraction （ BVF）, trabecular thickness （ Tb. Th）, and trabecular number （Tb. N） in experiment group were significant lower than those in sham group （ P 〈 0. 05 ）. Bone surface/bone volume （BS/BV） and trabecular spacing （Tb. Sp） in experiment group were significant higher than those in sham group （ P 〈 0. 05 ）. Three dimensional reconstruction and histological observation showed that, compared to sham group, fewer amount of bone trabeculae arranged sparsely with many breakage of trabecular bone, lacking of normal structure of cavitas medullaris in experiment group. One year after surgery, the microstructure of bone tissue in experiment group was markedly worse than that in sham group. Conclusion The method of ovariectomy combined with methylprednisolone injection can significantly decrease BMD in sheep lumbar vertebrae, significantly destroy microstructure of sheep lumbar vertebrae, and markedly reduce bone condition of sheep lumbar vertebrae. This method can be used to establish osteoporotic animal spinal model.