糖皮质激素对大鼠腰椎松质骨密度和微结构的动态影响

Dynamic effect on the bone mineral density and microarchitecture of trabecular bone in rats lumbar vertebra exposed to glucocorticoid

目的应用显微CT研究糖皮质激素(GC)随时间延长对大鼠腰椎松质骨密度和微结构的影响。方法52只3.5个月龄雌性SD大鼠随机分为基线组、糖皮质激素造模组(GCT)和对照组(Control)。基线组大鼠(10只)实验开始即处死,GCT组(22只)和Control组(20只)分别在实验开始后1周、9周各处死11只和10只,分别保存第6腰椎,行显微CT扫描,并在扫描完成后进行三维重建,获取骨小梁三维结构图像,最后进行松质骨定量分析。结果 GCT组的体积骨密度(vBMD)、组织骨密度(tBMD)、骨体积分数(BVF)、骨小梁数量(Tb.N)和骨小梁连接密度(Conn.D)均较Control组下降,9周时vBMD、tBMD、Tb.N、Conn.D改变显著(P<0.05),而骨小梁厚度(Tb.Th)、骨小梁间隔(Tb.Sp)和结构模型指数(SMI)较Control组升高;GCT组随造模时间的延长,BVF、Tb.N、Conn.D进一步下降,Tb.Th和Tb.Sp进一步增加(Tb.Sp的P<0.05～0.01)。GCT组1周和9周时,Tb.Th分别为(0.076±0.006)mm和(0.077±0.008)mm,高于基线组(0.072±0.010)mm,也高于Control组1周(0.073±0.009)mm和9周(0.076±0.004)mm。结论 GC可引起大鼠腰椎松质骨进行性骨量下降和骨微结构破坏,但残余的骨小梁有代偿性肥厚表现。

【Objective】 To investigate the time-related changes of trabecular bone in bone mineral density （BMD） and microarchitecture in glucocorticoid （GC）-treated rats lumbar vertebra. 【Methods】 Fifty-two three and half-month-old female SD rats were recruited： ten of them were killed as the baseline group; and the others were randomly assigned to the GC-treated group （GCT） or control group, and each group included 22 rats or 20 rats. The sixth lumbar vertebra were harvested in the baseline group at the beginning, first week and ninth week post -experiment in GCT and control groups respectively. A high resolution micro -CT was used to identify the densimetric and microarchitectural properties of trabeculae in the sixth lumbar vertebra. 【Results】 Compared with the control rats at each time-point, there was a decrease in the volumetric BMD （vBMD）, tissue BMD （tBMD）, bone volume fraction （BVF）, trabecular number （Tb.N） and trabecular connectivity （Conn.D） in the trabecular bone of the GCT rats, the decrease was more in the ninth GCT rats （P 0.05）.In addition, there was a increase in the trabecular thickness （Tb.Th）, trabecular separation （Tb.Sp） and structure model index （SMI） in GCT rats. A time-related analysis within the GCT groups showed there was a declination in BVF, Conn.D and Tb.N with administration time, but Tb.Sp was increased significantly （P 0.05）. The mean values of Tb.Th at the first week and the ninth week in GCT rats were （0.076 ±0.006） mm and （0.077±0.008） mm, respectively, higher than those at the baseline （0.072±0.010） mm and the control group, both at the first week （0.073±0.009） mm and the ninth week （0.076±0.004） mm. 【Conclusions】 The administration of GC is associated with a decrease in BMD and deterioration in microarchitecture of trabecular bone in rats lumbar vertebra; the remaining trabeculae seems thicken to increase their strength as compensation.