骨关节炎髌骨软骨中Ⅱ型胶原的表达和超微结构研究

Expression of type Ⅱ collagen and ultramicroscopic study on patellar cartilage in osteoarthritis

目的研究骨关节炎中髌骨软骨的病理变化特点。方法采用电镜及免疫组化技术等研究手段观察29例31膝骨关节炎患者和2例2膝对照组髌骨软骨标本的超微结构和基质中Ⅱ型胶原表达变化。结果透射电镜下:Ⅰ期关节软骨退变表现为胶原纤维网断裂,软骨细胞内脂滴、糖原及空泡增多,细胞器肿胀、增多。Ⅱ期表现为核不规则,染色质浓集,细胞器减少。Ⅲ期表现为胶原纤维紊乱严重,胞质内见巨大脂滴和大量空泡。Ⅳ期见核固缩或破裂,细胞收缩成脂肪性碎屑,也可形成空陷窝或微瘢痕。Ⅱ型胶原免疫组化显色指数Ⅰ～Ⅳ期分别为:48.43±11.96,53.36±10.12,8.01±3.89,4.34±2.39,与正常软骨(31.37±9.74)比较差异均有统计学意义(P<0.05)。结论骨关节炎髌骨软骨的病理变化特点首先是软骨基质中胶原纤维网的破坏和蛋白多糖的丢失,进而导致软骨细胞的变性和坏死,由浅及深,最终出现软骨全层消失及软骨下骨增生。

Objective To investigate the characteristics of histopathological changes of osteoarthritic cartilage. Methods The specimens of patellar articular cartilages from 31 knees of 29 patients with osteoarthritis and 2 knees of 2 young adults were studied under transmission electron microscope (TEM) and immunohistochemistry. The ultramicroscopic changes of patellar cartilage and the expression of type Ⅱ collagen in the extracellular matrix were analyzed. Results In Stage Ⅰ, the immunohistochemical staining of type Ⅱcollagen enhanced in all layers of articular cartilage, especially in the superficial layer, the staining was positive, particularly at the peripheral area of chondrocytes. TEM showed broken collagen fibrous networks, more lipid droplets, glycogen and vacuoles in cytoplasm, organelles swelling and increasing. In Stage Ⅱ, the immunohistochemical staining of type Ⅱcollagen increased in the superficial and middle layer of articular cartilage, especially in the chondrocytes around fissures; it was also positive in extracellular matrix, besides, there was irregular nucleus, chromatin concentration and organelles decreasing. In StageⅡ, severe disordered arrangement of collagen fibers, macrolipid droplets and a great number of vacuoles appearing in cytoplasm. In Stage Ⅲ the nuclear pycnosis, cells breaking into numerous fatty debris and forming a micro-scar or an empty lacuna. Index of staining of the immunohistochemical characteristics of type Ⅳ collagen from StageⅠ-Ⅳ were 48.43±11.96, 53.36±10.12, 8.01±3.89, 4.34±2.39 respectively, while in comparison with the normal cartilages, there were significant difference in all stages (P< 0.05). Conclusion The initial damage of osteoarthritic cartilage starts at the matrix of cartilage, the collagen network disrupts, and then proteoglycan is lost. The microenvironment of chondrocytes consists of changes with degradation of matrix. The chondrocytes become degenerated and necrosis presents from superficial to deep layer, and then affects the matrix again. Finally, the total cartilage layer disappears, and the underlying bone proliferation happens.