张力载荷诱导下兔椎间盘退变体内模型的建立及意义

Establishment of an in vivo rabbit model of intervertebral disc degeneration under tensile load and its significance

背景:异常应力被认为是导致椎间盘退变的重要因素。随着对椎间盘退变发生机制研究的不断深入,建立一种理想的力学相关性椎间盘退变体内动物模型具有重要的实践意义。目的:建立兔椎间盘体内模型,施以持续的张力载荷,探究其对椎间盘退变的影响。方法:25只6月龄新西兰大白兔随机分为3组,空白对照组5只,假加力组10只,加力组10只。空白对照组不作任何处理,于实验第1天手术获取L_(4/5)椎间盘;加力组和假加力组均固定椎间盘加力器,加力组施以L_(4/5)椎间盘1 MPa(10 kg/cm^2)轴向牵张力,假加力组仅固定加力器但不加力,2组分别在14,28 d手术获取椎间盘。X射线观察L_(4/5)椎间隙高度变化和邻近骨质改变;苏木精-伊红染色观察椎间盘组织形态学变化;NBT染色观察椎间盘细胞存活状态;RT-PCR检测各时间点椎间盘组织中蛋白聚糖、Ⅱ型胶原和SOX9 m RNA表达变化。结果与结论:(1)假加力组各时间点与空白对照组相比,X射线表现、苏木精-伊红染色、细胞存活状态和蛋白多糖、Ⅱ型胶原、SOX9 m RNA表达差异均无显著性意义;(2)与空白对照组相比发现,加力组随着张力载荷时间的延长,L_(4/5)椎间隙逐渐变窄,关节面毛糙,上下椎体前缘骨质增生呈唇状改变;椎间盘细胞分布不均匀、紊乱;髓核脱水缩小,纤维环排列混乱,脊索细胞空泡状组织趋于消失;蛋白多糖、Ⅱ型胶原、SOX9表达显著下调;(3)结果提示,成功建立了兔椎间盘体内模型,并在此模型基础上阐明持续张力载荷可直接导致椎间盘退变。

BACKGROUND：Abnormal stress is an important factor causing intervertebral disc degeneration. To establish an ideal in vivoanimal model of intervertebral disc degeneration is of great significance for in-depth study on the related pathogenesis. OBJECTIVE：To develop anin vivo rabbit intervertebral disc model and to investigate the relationship between continuous tensile load and intervertebral disc degeneration. METHODS：Twenty-five New Zealand white rabbits aged 6 months old were randomly divided into three groups： blank control （n=5）, sham （n=10） and experimental （n=10） groups. The blank control group received no intervention, and the L4/5 segments were removed at the 1st day. The intervertebral disc assistor was used to fix the L4 and L5 vertebral bodies in the experimental and sham groups, the L4/5 segments in the experimental group were loaded 1 MPa axial tensile force, and the L4/5 segments in both two groups were then removed at 14 and 28 days. The changes of L4/5 intervetebral space height and surrounding bone substance were observed by X-ray examination, the morphological changes of the intervertebral disc were observed by hematoxylin-eosin staining, the cell survival was detected by nitro blue tetrazolium staining and mRNA expression levels of aggrecan, collagen type Ⅱ and SOX9 in the intervertebral disc tissues were assessed by RT-PCR at each time point. RESULTS AND CONCLUSION：The radiological manifestations, histological changes, cell survival and mRNA expression levels of aggrecan, collagen type Ⅱ and Sox9 showed no significant difference between the blank control and sham groups. Comparied with the blank control group, in the experimental group, the L4/5 intervertebral space was narrowed with time, the articular surface was coarse, and the upper and lower corpus vertebrae edge appeared to have lip-shaped hyperplasia; the intervertebral disc cells distributed irregularly; the nucleus pulposus was in dehydration and deflation, annulus fibrosus arranged irregularly, and the vacuoles in notochord cells tended to disappear; the expression levels of aggrecan, collagen type Ⅱ and SOX9 were markedly downregulated. These findings suggest that the in vivo rabbit model of intervertebral disc is successfully established, in which continuous mechanical tensile load is further proved to directly cause intervertebral disc degeneration.