Establishment of a Rabbit Model of Adjacent Intervertebral Disk Degeneration After Lumbar Fusion and Fixation and Evaluation of Autophagy Factor Expression in Nucleus Pulposus Cells

Background: The objectives of this research were to establish an animal model of adjacent segment degeneration (ASD) bordering lumbar fusion and to investigate the expression of autophagy factors in nucleus pulposus cells of adjacent intervertebral disks. Materials and Methods: Twenty-four adult New Zealand white rabbits were enrolled and divided into two groups: group A (n=12) and group B (n=12). Posterolateral fusion and fixation were performed after intervertebral disk degeneration occurred in group A, and the rabbits were monitored for 6 months. Group B was the control group and did not undergo fusion surgery. These rabbits were monitored for 6 months. Real-time quantitative polymerase chain reaction and immunohistochemistry were performed to detect the mRNA and protein expressions of PTEN-induced kinase 1 (PINK1), Parkin, ADAMTS-4, and MMP-3. An external database, the GEO database, was used to examine the expression of these genes and analyze them for differential expression. Results: After lumbar fusion in rabbits, the animal model of ASD exhibited gradual degeneration of adjacent intervertebral disks over time. Group A displayed significantly higher mRNA and protein expressions of PINK1 and MMP-3 but lower expression of ADAMTS-4 compared with group B ( P <.05). The results analyzed in the GEO database showed that the expression of PINK1 was higher in group A than in group B, while the expression of ADAMTS-4 was lower in group A than in group B. Conclusion: After posterolateral lumbar fusion in rabbits, the animal ASD model showed gradual deterioration of adjacent intervertebral disks with prolonged follow-up. The findings indicate the important role of autophagy in the apoptosis of nucleus pulposus cells in adjacent intervertebral disks. [ Orthopedics . 2024;47(4):e167–e173.]