Establishment of anin vivo rabbit model of intervertebral disc degeneration under tensile load and its significance / 中国组织工程研究

ABSTRACT

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.