关键词: 组织构建, 软骨组织构建, 关节软骨, 软骨下骨, 重建与吸收, 骨小梁, 形态学, 生物力学, 国家自然科学基金

Abstract:

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 collected immediately and at 4, 7 and 14 days after modeling, and then the morphological changes of femoral head cartilage and cartilage were generally 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.

Key words: tissue construction, cartilage tissue construction, articular cartilage, subchondral bone, reconstruction and absorption, trabecular bone, morphology, biomechanics, National Natural Science Foundation of China