Development and evaluation of controllable axial loading-induced rabbit lumbar disc degeneration model

[Objective] To develop a new rabbit lumber disc degeneration model by imposing controllable axial olading upon corresponding segment, and to evaluate the features of the new model. [Method] Forty Japanese white rabbits (4 months old) were randomly divided into groups 1, 2, 3, 4 and 5 (8 rabbits in each group). A self-made Loading device based on 2 K-wires that punctured through the adjunctive vertebras of corresponding intervertebral discs, was utilized to impose 98 N pressure on the discs for 1, 2, 4 and 8 weeks in groups 2, 3, 4 and 5 respectively. And no pressure was imposed on the group I as sham-operated group (control group). Degeneration of the discs was evaluated by Thompson's grading system. magnetic resonance imaging (MRI) scanning, haematoxylin and eosin (HE) staining, and immunohistochemical staining for type Ⅰand type Ⅱ collagen. [Result] (1) According to the Thompson' a system, 7 discs reached grade Ⅰ in group 2, 6 discs reached grade Ⅲ in group 3, 5 discs reached grade Ⅵ in group 4, and 4 discs reached grade Ⅴ in group 5, respectively. (2) MRI scan displayed that the discs in group 2 demonstrated mile degeneration, and those in group 3 moderate degeneration, while the discs in group 4 and 5 respectively severe degeneration. (3) HE staining indicated that the changes of disc degeneration exhibited more homogeneous than those of annulus fibrosus injury model. (4) Immunohistochemical staining showed that the trend of matrix degeneration was similar to that of human disc degeneration. Conclusion The new model is capable of simulating lumbar disc degeneration effectively, especially for establishment of mild or moderate degeneration model. This model can he used in studies on the mechanism and therapy of intervertebral disc degeneration.