虽然相邻节段性椎间盘退变(ASDD)是腰椎融合术后最常见的并发症之一,其确切机制尚不清楚。作为RANKL的抗体,denosumab(Dmab)有效地减少骨吸收和刺激骨形成,可以增加骨密度(BMD)并改善骨质疏松症。然而,目前尚未证实Dmab对ASDD是否有逆转或阻滞作用。
3月龄雌性Sprague-Dawley大鼠双侧卵巢切除(OVX)术后4周行L4-L5后外侧腰椎融合术(PLF),并在PLF术后4周给予Dmab(OVXPLFDmab组)。此外,定义了以下对照组:假,OVX,PLF,和OVX+PLF(每个n=12)。接下来,采用手工触诊和X线评估腰椎融合状态。通过显微计算机断层扫描(μCT)评估了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Safranin-O绿色染色鉴定了ASDD的特征性改变。使用抗酒石酸酸性磷酸酶(TRAP)染色检测破骨细胞,并对椎骨的生物力学特性进行了评价。Aggrecan(Agg),金属蛋白酶-13(MMP-13),通过免疫组织化学和实时聚合酶链反应(RT-PCR)分析检测椎间盘中具有血小板反应蛋白基序4(ADAMTS-4)表达的去整合素和金属蛋白酶。此外,通过免疫组织化学评估CD24和Sox-9的表达。
手动触诊显示融合节段不活动的明显证据。与OVX+PLF组相比,在OVX+PLF+Dmab组通过X线检查观察到更多的新骨形成。Dmab通过保留椎间盘高度指数(DHI)显着减轻ASDD,降低端板孔隙率,增加椎体的生物力学特性和骨密度。TRAP染色结果显示Dmab治疗后活性破骨细胞数量显著减少,尤其是软骨下骨和软骨终板。此外,椎间盘(IVD)中的蛋白质和mRNA表达结果表明,Dmab不仅通过降低MMP-13和ADAMTS-4来抑制基质降解,而且还通过增加Agg来促进基质合成。Dmab通过增加CD24但减少Sox-9来维持脊索细胞的数量。
这些结果表明Dmab可能是ASDD治疗的新治疗靶标。
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.