Department of Orthopedic Surgery, Hebei Medical University, Shijiazhuang, People's Republic of China.
Medical Research Center, North China University of Science and Technology, Tangshan, People's Republic of China.
Arthritis Res Ther. 2021 May 28;23(1):152. doi: 10.1186/s13075-021-02525-8.
Although adjacent segmental intervertebral disc degeneration (ASDD) is one of the most common complications after lumbar fusion, its exact mechanism remains unclear. As an antibody to RANKL, denosumab (Dmab) effectively reduces bone resorption and stimulates bone formation, which can increase bone mineral density (BMD) and improve osteoporosis. However, it has not been confirmed whether Dmab has a reversing or retarding effect on ASDD.
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 were given Dmab 4 weeks after PLF surgery (OVX+PLF+Dmab group). In addition, the following control groups were defined: Sham, OVX, PLF, and OVX+PLF (n=12 each). Next, manual palpation and X-ray were used to evaluate the state of lumbar fusion. The bone microstructure in the lumbar vertebra and endplate as well as the disc height index (DHI) of L5/6 was evaluated by microcomputed tomography (μCT). The characteristic alterations of ASDD were identified via Safranin-O green staining. Osteoclasts were detected using tartrate-resistant acid phosphatase (TRAP) staining, and the biomechanical properties of vertebrae were evaluated. Aggrecan (Agg), metalloproteinase-13 (MMP-13), and a disintegrin and metalloproteinase with thrombospondin motifs 4 (ADAMTS-4) expression in the intervertebral disc were detected by immunohistochemistry and real-time polymerase chain reaction (RT-PCR) analysis. In addition, the expression of CD24 and Sox-9 was assessed by immunohistochemistry.
Manual palpation showed clear evidence of the fused segment's immobility. Compared to the OVX+PLF group, more new bone formation was observed by X-ray examination in the OVX+PLF+Dmab group. Dmab significantly alleviated ASDD by retaining disc height index (DHI), decreasing endplate porosity, and increasing vertebral biomechanical properties and BMD. TRAP staining results showed a significantly decreased number of active osteoclasts after Dmab treatment, especially in subchondral bone and cartilaginous endplates. Moreover, the protein and mRNA expression results in discs (IVDs) showed that Dmab not only inhibited matrix degradation by decreasing MMP-13 and ADAMTS-4 but also promoted matrix synthesis by increasing Agg. Dmab maintained the number of notochord cells by increasing CD24 but reducing Sox-9.
These results suggest that Dmab may be a novel therapeutic target for ASDD treatment.
尽管邻近节段椎间盘退变（ASDD）是腰椎融合术后最常见的并发症之一，但确切的发病机制尚不清楚。作为 RANKL 的抗体，地舒单抗（Dmab）可有效减少骨质吸收并刺激骨质形成，从而增加骨密度（BMD）并改善骨质疏松症。然而，Dmab 是否对 ASDD 具有逆转或延缓作用尚未得到证实。
4 周龄雌性 Sprague-Dawley 大鼠行双侧卵巢切除术（OVX）后 4 周行 L4-L5 后路腰椎融合术（PLF）并采用棘突钢丝固定，在 PLF 术后 4 周给予 Dmab（OVX+PLF+Dmab 组）。此外，还定义了以下对照组：假手术（Sham）组、OVX 组、PLF 组和 OVX+PLF 组（每组 n=12）。然后，采用手动触诊和 X 射线评估腰椎融合情况。通过微计算机断层扫描（μCT）评估腰椎和终板的骨微结构以及 L5/6 的椎间盘高度指数（DHI）。通过番红 O 绿染色鉴定 ASDD 的特征性改变。采用抗酒石酸酸性磷酸酶（TRAP）染色检测破骨细胞，并评估椎体的生物力学性能。通过免疫组化和实时聚合酶链反应（RT-PCR）分析检测椎间盘内聚集蛋白（Agg）、基质金属蛋白酶-13（MMP-13）和解整合素金属蛋白酶与凝血酶样 4（ADAMTS-4）的表达。通过免疫组化检测 CD24 和 Sox-9 的表达。
手动触诊显示融合节段的活动度明显降低。与 OVX+PLF 组相比，OVX+PLF+Dmab 组 X 线检查可见更多新骨形成。Dmab 通过保留椎间盘高度指数（DHI）、减少终板多孔性以及增加椎体生物力学性能和骨密度，显著缓解了 ASDD。TRAP 染色结果显示，Dmab 治疗后破骨细胞的活性明显减少，尤其是在软骨下骨和软骨终板中。此外，椎间盘（IVD）的蛋白和 mRNA 表达结果表明，Dmab 不仅通过降低 MMP-13 和 ADAMTS-4 抑制基质降解，还通过增加 Agg 促进基质合成。Dmab 通过增加 CD24 减少 Sox-9 来维持脊索细胞的数量。
这些结果表明，Dmab 可能是治疗 ASDD 的一种新的治疗靶点。
