Development of a Novel Rat Intervertebral Disc Degeneration Model by Surgical Multifidus Resection-Induced Instability

-OBJECTIVE: This study aimed to investigate whether surgical resection of multifidus in rats could generate a reliable model of intervertebral disc degeneration (IVDD).-METHODS: Instability of the lumbar spine in Sprague- Dawley rats was induced by multifidus resection. Long-issimus changes were examined by hematoxylin and eosin staining and immunohistochemistry. Specific protein and mRNA changes in the nucleus pulposus (NP) were quan-tified by Western blot and reverse transcription- polymerase chain reaction. Bone alterations were assessed using X-ray imaging, and disc changes were evaluated by hematoxylin and eosin staining, immunoflu-orescence, and immunohistochemistry.-RESULTS: Fat infiltration and increased tumor necrosis factor -a expression in the longissimus were detected following surgery. Reverse transcription-polymerase chain reaction and Western blot results demonstrated that the inflammation and catabolism in the NP were increased after the surgical intervention. Moreover, X-ray imaging showed that the disc height had decreased and bone spurs had formed at the vertebral rims. Histological analyses further revealed degeneration of the annulus fibrosus, endplate, and NP. Furthermore, in contrast to the sham group, the collagen II expression was reduced, while matrix metalloproteinase-13 was increased in the surgery group.-CONCLUSIONS: Surgical resection of the multifidus in rats resulted in a reproducible IVDD model. Because the present procedure does not impart direct injury to the intervertebral disc, it can better imitate the pathological states in humans. Therefore, our rat multifidus resection model might help us further understand the intrinsic path-ophysiology of IVDD.