甲状旁腺激素1-34促进尾悬吊再负重大鼠骨质量恢复

PTH1-34 Promoted Bone Mass Recovery in Rats with Reloading After Tail-suspension

关键词:  甲状旁腺激素1-34  尾悬吊  骨密度  骨组织形态计量学  生物力学  骨钙素

Key words:  PTH1-34  tail-suspension  bone mineral density  bone histomorphometry  biomechanical test  osteocalcin

摘要:

目的 观察尾悬吊大鼠再负重骨量的变化及甲状旁腺激素1-34（PTH1-34）干预的效果及机制。方法 5月龄大鼠24只分为4组，对照组（CL组）、尾悬吊4周组（UL组）、尾悬吊2周再负重2周组（UL+RL组）、尾悬吊2周再负重加PTH1-34干预2周组（UL+RL+PTH组），每组6只。4周后处死大鼠，分离左侧胫骨行骨组织形态计量学分析；检测左侧股骨骨密度；取右侧胫骨提取蛋白和RNA，分别采用Western blotting和realtime PCR检测骨钙素（osteocalcin，OCN）的表达；三点弯曲试验分析右侧股骨最大载荷和弹性模量。结果 CL组骨密度显著高于其余3组（P<0.05），UL+RL组和UL+RL+PTH组均显著高于UL组（P<0.05）；UL+RL+PTH组显著高于UL+RL组（P<0.05）。CL组骨小梁体积比（bone volume per total volume，BV/TV）显著高于UL、UL+RL、UL+RL+PTH组（P<0.05），UL组显著低于UL+RL组和UL+RL+PTH组（P<0.05）；UL+RL+PTH组显著高于UL+RL组（P<0.05）。CL组骨小梁数量显著高于其余3组（P<0.05），UL+RL+PTH组显著高于UL组（P<0.05）。CL组骨小梁分离度显著低于UL、UL+RL、UL+RL+PTH组（P<0.05），UL组显著低于UL+RL组和UL+RL+PTH组（P<0.05）。UL组最大载荷显著低于其余3组，UL+RL组显著低于CL组（P<0.05）；CL组弹性模量显著高于其余3组（P<0.05），UL+RL+PTH组显著高于UL组、UL+RL组（P<0.05）。Western blotting检测OCN蛋白表达在CL组和UL+RL+PTH组显著高于UL组（P<0.05）。Realtime PCR检测各组间的OCN mRNA表达水平无显著差别。结论 尾悬吊2周可诱发大鼠下肢骨量丢失、力学性能下降、OCN含量减少，再负重2周后上述改变可得到部分恢复，PTH1-34干预能促进这一过程。

Abstract:

OBJECTIVE To observe the changes of bone mass in tail-suspended and subsequent reloaded rats, as well as the effects and mechanism of PTH1-34 on these process. METHODS Twenty four 5 month old rats were divided into 4 groups:control(CL) group, tail suspension for 4 weeks(UL) group, tail suspension for 2 weeks and reloading for 2 weeks(UL+RL) group, tail suspension for 2 weeks and reloading plus PTH1-34 intervention for 2 weeks(UL+RL+PTH) group, 6 rats in each group. All rats were sacrificed 4 weeks later, left tibia was used for bone histomorphometry analysis, left femur was used for bone mineral density, and right tibia was assigned to biomechanical test, tibia were harvested for detecting expression levels of osteocalcin(OCN) by Western blotting and realtime PCR, respectively. The maximum load and elastic modulus of the right femur were analyzed by a three-point bending test. RESULTS Bone mineral density(BMD) in CL group was significantly higher than other three groups(P<0.05), UL+RL and UL+RL+PTH rats showed markedly higher values than UL rats(P<0.05), UL+RL+PTH rats showed markedly higher BMD than UL+RL rats(P<0.05). CL group showed markedly higher bone volume per total volume (BV/TV) values than those in the UL, UL+RL and UL+RL+PTH groups, UL+RL and UL+RL+PTH groups showed significantly higher BV/TV than that of UL group(P<0.05), UL+RL+PTH group showed markedly higher BV/TV than UL+RL group(P<0.05). Trabecular number in CL group was significantly higher than other three groups, UL+RL+PTH group showed markedly higher trabecular number than UL group(P<0.05); Trabecular separation in CL group was significantly lower than those in the UL, UL+RL and UL+RL+PTH groups(P<0.05), UL+RL and UL+RL+PTH groups showed significantly lower trabecular separation than that of UL group(P<0.05). UL group showed markedly lower maximal load compared to the other three groups, UL+RL group showed significantly lower maximal load than CL group(P<0.05). Rats in CL group showed markedly higher elastic modulus compared to other three groups(P<0.05); UL+RL+PTH group showed significantly higher elastic modulus than UL and UL+RL groups. Western blotting showed IOD of OCN in UL group was significantly lower than CL group and UL+RL+PTH group(P<0.05). No significant difference between any two groups was found of the mRNA expression level of OCN. CONCLUSION Two weeks of tail-suspension induced disuse of hindlimb caused bone loss, deterioration of biomechanical properties and reduction of OCN expression, which were partially restored after reloading and enhanced by PTH1-34 treatment.