Objective The rel iable animal model of intervertebral disc degeneration, can provide important experimental carrier to research pathogenesis and treatment of intervertebral disc degeneration. To establ ish three kinds of injury induced rabbit intervertebral disc degeneration models and to compare the characteristics among them by using biochemical and radiological methods. Methods Twenty-five healthy New Zealand white rabbits (weighing 2.0-2.5 kg) were randomly divided into 5 groups (n=5). The L3, 4, L4, 5 and L5, 6 discs in each rabbit were used for study. Groups A and B were forannulus puncture with an 18-gauge needle and a 22-gauge needle, respectively; group C was for nucleus aspiration; group D was for endplate injury and group E was used as a control. The lumbar spinal plain radiographs and magnetic resonance images (MRI) were evaluated, the raltive height of intervertebral disc was measured and the grades of disc degeneration were recorded 2, 4, 8, 16, and 32 weeks after operation. The water and the sulfated-glycosaminoglycan (s-GAG) contents of the nucleus were measured after sacrifice (randomly choose one rabbit from each group at each time point). Results In groups A, B, C and D, the height of intervertebral space in plain radiograph gradually decreased after operation. The anterior bony excrescences of vertebral body and varying degrees of calcification of endplate were also observed. The signal intensity of disc in T2-weighted magnetic resonance imaging decreased with time too. Compared with group E, the significant changes of height of intervertebral discs and grades of disc degeneration in MRI occurred at different time points within 4 weeks in groups A-D (P lt; 0.05). The significant change in groups C and D occured earl ier than in groups A and B. The water and s-GAG contents of discs decreased gradually in groups A-D after operation, while the significant change occurred at varying time points within 8 weeks compared with group E (P lt; 0.05). The apparent downward trend in groups C and D occured earl ier than in groups A and B. Conclusion All three methods are successful in inducing intervertebral disc degeneration. The degenerative process induced by endplate injury and nucleus aspiration is faster and more severe than that induced by annulus puncture.
Objective Polylactic acid (PLA) patch has proper steric configuration, sufficient mechanic strength, and flexibil ity, to investigate the blocking effect on the intra-discal inflammation after annulus puncture sticked by medical glue so as to seal the pinhole left after annulus puncture. Methods Twenty healthy New Zealand white rabbits (weighing 2.0-2.5 kg) were randomly divided into 4 groups (n=5): groups A, B, C, and D. In group A, the rabbits underwent exposure of intervertebral disc and transverse process at L2-7 as a control; in group B, the rabbits received annulus puncture at L2-7 with an 18-gauge needle; and in groups C and D, the pinholes were sealed respectively with a PLA patch sticked with medical gel and medical gel alone after annulus puncture at L2-7. General condition of rabbits was observed after operation. The intervertebral disc tissue was harvested 1 week after operation. The tissue structure was observed by HE and Masson staining. And the expressions of inflammatory factors l ike interleukin 1β (IL-1β), tumor necrosis factor α (TNF-α), and inducible nitric oxide synthase (iNOs) were detected with immunohistochemistry and ELISA. Results All the animals survived till the end of the experiment. In group A at 1 week, the nucleus pulposus tissue had normal structure. In group B at 1 week, leak of nucleus pulposus from the pinhole and sl ight adhesion to the adjacent tissue could be seen, and the nucleus pulposus tissue had significant degenerative change by histological observation. In groups C and D, clots of coagulated medical gel and extensive adhesion to the adjacent tissue could be seen; histological observation suggested that the nucleus pulposus tissue of group C had similar histology manifestation to that of group A; while group D had similar histology manifestation to group B with obviously-decreased cells and disorder of matrix. ELISA test showed remarkably elevated expression level of inflammatory factors including IL-1β, TNF-α, and iNOs in groups B and D when compared with groups A and C, showing significant differences (P lt; 0.05), and similar expression level were observed in groups A and C, groups B and D (P gt; 0.05). Conclusion The PLA patch sticked with medical gel is effective in blocking the intra-discal inflammation 1 week after annulus puncture.