Discussion
Anti-osteoporosis medication SR treatments not only maintain bone mass and prevent fractures, but early intervention could also potentially delay degenerative conditions linked to osteoporosis. Taken together, our results suggested that SR might be a promising approach for the intervention of fusion-induced ASDD with osteoporosis.
Methods
Fifth three-month-old female Sprague-Dawley rats that underwent L4-L5 posterolateral lumbar fusion (PLF) with spinous-process wire fixation 4 weeks after bilateral ovariectomy (OVX) surgery. Animals were administered vehicle (V) or SR (900 mg/kg/d) orally for 12 weeks post-PLF as follows: Sham+V, OVX + V, PLF + V, OVX + PLF + V, and OVX + PLF + SR. Manual palpation and X-ray were used to evaluate the state of lumbar fusion. Adjacent-segment disc was assessed by histological (VG staining and Scoring), histomorphometry (Disc Height, MVD, Calcification rate and Vascular Bud rate), immunohistochemical (Col-II, Aggrecan, MMP-13, ADAMTS-4 and Caspase-3), and mRNA analysis (Col-I, Col-II, Aggrecan, MMP-13 and ADAMTS-4). Adjacent L6 vertebrae microstructures were evaluated by microcomputed tomography.
Results
Manual palpation and radiographs showed clear evidence of the fused segment's immobility. After 12 weeks of PLF surgery, a fusion-induced ASDD model was established. Low bone mass caused by ovariectomy can significantly exacerbate ASDD progression. SR exerted a protective effect on adjacent segment intervertebral disc with the underlying mechanism possibly being associated with preserving bone mass to prevent spinal instability, maintaining the functional integrity of endplate vascular microstructure, and regulating matrix metabolism in the nucleus pulposus and annulus fibrosus.