急性创伤后2周软骨下骨未发生明显力学变化*

摘要

背景：既往研究主要集中于退行性软骨损伤及软骨下骨的修复机制，而对于急性创伤后软骨下骨的组织、形态研究比较少。目的：观察软骨急性损伤后软骨下骨的早期组织形态学、分子生物、生物力学的变化。方法：健康成年新西兰兔24只，建立股骨头软骨缺损模型，分别收集模后即刻、造模后4，7，14 d兔股骨头软骨及软骨下骨标本，大体观察造模后兔股骨头软骨及软骨形态变化，番红-固绿染色观察软骨及软骨下骨形态变化、免疫组织化学法测定骨转换标志物骨保护素/核因子κB受体活化因子配体的表达、Micro-CT扫描分析软骨下骨超微结构改变、力学检测法评估软骨下骨机械强度变化。结果与结论：大体粗测可见股骨头缺损模型于造模后7 d出现软骨缺损面积扩大，深度增加及退变表现，利用染色法观测进一步证实了造模后7 d其软骨厚度降低，软骨下骨骨小梁吸收。免疫组织化学及免疫荧光检测发现，造模后7-14 d软骨下骨中骨保护素表达明显减少，核因子κB受体活化因子配体表达量显著增加，骨保护素/核因子κB受体活化因子配体比值降低，提示骨转化减弱甚至逆转。采用Micro-CT分析发现造模后7-14 d软骨下骨的骨小梁数量增加，骨小梁数目及间距减小，通透性降低。抗压力学试验分析抗压强度和弹性模量未见统计学差异。结果提示，软骨损伤后软骨下骨可在早期造模后7 d后即发生显著组织形态变化和骨转换能力的下调，从而导致软骨进一步破坏；造模后2周内未见软骨下骨从在明显力学改变，基于此的修复手段可为软骨损伤修复提供治疗靶点。%BACKGROUND: Previous studies mainly focused on the degenerative cartilage damage and repair mechanisms of the subchondral bone. However, studies on the histopathology and biomechanics of the subchondral bone after acute cartilage injury are few. OBJECTIVE: To investigate morphology, molecular biology and biomechanical changes of the subchondral bone after acute cartilage injury. METHODS: Twenty-four healthy adult New Zealand rabbits were used to establish the femoral head cartilage defect model. The specimens of femoral head cartilage and subchondral bone were col ected immediately and at 4, 7 and 14 days after modeling, and then the morphological changes of femoral head cartilage and cartilage were general y observed. Safranin-fast green staining was used to observe the morphological changes of femoral head cartilage and subchondral bone; expression of osteoprotegerin/nuclear factor kappa B receptor activating factor ligand was tested with immunohistochemistry; ultrastructural changes and the biomechanical assessment of the subchondral bone were observed with Micro-CT scan and biomechanical assessment, respectively. RESULTS AND CONCLUSION: Gross visualization revealed that degenerative aggravation of the cartilage defect which was evidenced by enlargement of the area and the depth of the defect at 7 days after modeling. The reduced cartilage thickness and subchondral trabecular bone absorption were observed at 7 days after modeling with the staining methods. Imunohistochemistry and immunofluorescence found that the expression of osteoprotegerin was decreased significantly at 7-14 days after modeling, while the expression of nuclear factor kappa B receptor activating factor ligand was increased significantly, and the ratio of osteoprotegerin/nuclear factor kappa B receptor activating factor ligand was reduced, indicating that bone conversion was weak or even reversed. Micro-CT analysis demonstrated that the trabecular number and spacing of the subchondral bone were greatly reduced, while the number of the trabeculae was increased with reduced permeability at 7-14 days after modeling. Biomechanical test showed that there was no significant difference in the compressive strength and elastic modulus. The results indicate that notable histomorphologic change and down-regulation of turnover of the subchondral bone were identified at 7 days after cartilage injury, which resulted in aggressive damage to the articular cartilage. However, no mechanical changes of subchondral bone observed in 2 weeks after modeling, and the therapeutic strategy based on these findings may present potential targets for cartilage regeneration.