辛伐他汀对尾悬吊再负重大鼠长骨骨量恢复的影响

Effect of simvastatin on bone mass recovery in rats with reloading after tail-suspension

目的观察尾悬吊大鼠再负重骨量的变化及辛伐他汀干预对该过程的影响及机制。方法 5月龄大鼠24只分为4组,每组6只:正常对照组(CL组)、尾悬吊6周组(UL组)、尾悬吊3周再负重3周组(UL+RL组)、尾悬吊3周再负重加辛伐他汀干预3周组(10 mg/kg/d,UL+RL+SIM组);实验持续6周,处死大鼠取左侧股骨进行骨密度分析,取左侧胫骨行骨组织形态计量学分析;取右侧股骨经生物力学试验分析最大载荷和弹性模量;取右侧胫骨制备组织匀浆,提取RNA和蛋白,分别采用real-time PCR和western blot检测Ⅰ型胶原(Col Ⅰ)的表达。结果 (1)骨密度:CL组显著高于其余3组(P<0.05),UL+RL组和UL+RL+SIM组均显著高于UL组(P<0.05);(2)骨组织形态计量学:BV/TV:CL组显著高于其余3组(P<0.05),UL+RL组和UL+RL+SIM组均显著高于UL组(P<0.05);Tb.N:CL组显著高于其余三组(P<0.05);Tb.Th:CL组显著高于UL组(P<0.05);Tb.Sp:CL组显著低于其余三组(P<0.05),UL+RL组和UL+RL+SIM组均显著低于UL组(P<0.05)。(3)生物力学检测结果:CL组最大载荷、弹性模量显著高于其他3组(P<0.05)。(4)Realtime PCR检测结果:各组间ColⅠ的mRNA表达水平无显著差别。(5)Western blot:UL组ColⅠIOD值显著低于CL组(P<0.05),其余组间差异无显著性。结论大鼠尾悬吊诱发下肢骨量丢失、微结构退变、力学性能下降、Ⅰ型胶原含量减少,而再负重后上述指标可得到部分恢复,辛伐他汀干预不能促进这一过程。

Objective To observe the changes of bone mass in reloaded rats after tail-suspension, and the effect and mechanism of simvastatin on this process. Methods Twenty-four 5-month old rats were divided into 4 groups of 6 animals in each group： Control （CL） group without tail-suspension, unloaded （UL） group with tail-suspension for 6 weeks, other 12 rats received tail-suspension for 3 weeks, then reloaded for subsequent 3 weeks （ UL ＋ RL） or combined with simvastatin treatment （ UL ＋ RL ＋ SIM） at a dose of 10 mg/kg/d. All rats were sacrificed 6 weeks later, and the left femur was used for examination of bone mineral density, left tibia was used for bone histomorphometry analysis, the right femur and tibia were harvested for biomechanical test, and expression levels of type I collagen by real-time PCR and Western blot, respectively. Results 1. BMD of the CL group was significantly higher than those of the other three groups （P〈0.05）, and was markedly lower than those in the UL＋RL and UL＋RL＋SIM groups （P〈0.05）. 2. The bone histomorphometry showed that BV/TV in the CL group was significantly higher than those in the other 3 groups, and the UL ＋ RL and UL ＋ RL ＋ SIM groups showed a significantly higher BV/TV than that of UL group （P 〈 0. 05 ）. The Tb. Th was significantly higher in the CL group than in the UL group. The Tb. Sp in the CL group was significantly lower than those in the other 3 groups （ P 〈 0.05 ）. The UL ＋ RL and UL ＋ RL ＋ SIM groups showed significantly lower Tb. Sp than that of the UL group （P 〈 0.05）. 3. Biomechanical test showed that the maximal load and elastic modulus in the CL groups were significantly higher than those of the other three groups （ P 〈 0. 05 ）. 4. Real-time PCR showed that no significant difference in the mRNA expression level of Col I was found between any two groups. 5. Western blot showed that the IOD of Col I is significantly lower than that in the CL group. Conslusions Bone loss, destruction of trahecular bone microarchitecture and biomechanical properties and reduction of type 1 collagen are present in tail-suspension treated rats, which are partially restored after reloading, and this recovery process is not enhanced by simvastatin treatment.