Imai K, Ohta S, Matsumoto T, Fujimoto N, Sato H, Seiki M, Okada Y
Department of Molecular Immunology and Pathology, School of Medicine, Kanazawa University, Japan.
Am J Pathol. 1997 Jul;151(1):245-56.
Matrix metalloproteinases (MMPs) are expressed in osteoarthritic (OA) cartilage and are thought to be involved in the degradation of cartilage extracellular matrix (ECM). Among these proteinases, MMP-2 (gelatinase A) demonstrates a wide range of substrate specificity against the ECM present in cartilage. Although MMP-2 expression increases in OA cartilage, the activation mechanism of the corresponding zymogen (pro-MMP-2) in cartilage is unknown. In this study, we examined the expression pattern of membrane-type 1 MMP (MT1-MMP) in human OA articular cartilage and its correlation with the activation of pro-MMP-2. Immunohistochemical studies demonstrate that MT1-MMP localizes to the chondrocytes in the superficial and transitional zones in all of the samples examined directly correlating with cartilage degradation. Reverse transcription polymerase chain reaction confirmed the predominant expression of MT1-MMP mRNA in the OA cartilage. In situ hybridization revealed the site of expression of MT1-MMP in OA cartilage to be the chondrocytes. Through gelatin zymography and a sandwich enzyme immunoassay it was demonstrated that OA cartilage explants secrete significantly higher levels of pro-MMP-2 than normal samples. Pro-MMP-2 activation was enhanced in the OA cartilage samples and correlated with MT1-MMP expression in the cartilage. Plasma membranes prepared from cultured chondrocytes with MT1-MMP expression and those directly isolated from OA cartilage could activate pro-MMP-2. MT1-MMP gene expression in cultured chondrocytes was induced by treatment with interleukin-1 alpha and/or tumor necrosis factor-alpha. These data suggest that cytokine-induced MT1-MMP in the chondrocytes may play a key role in the activation of pro-MMP-2 in the OA articular cartilage, leading to cartilage destruction through ECM degradation.
基质金属蛋白酶（MMPs）在骨关节炎（OA）软骨中表达，被认为参与软骨细胞外基质（ECM）的降解。在这些蛋白酶中，MMP-2（明胶酶A）对软骨中的ECM表现出广泛的底物特异性。尽管OA软骨中MMP-2的表达增加，但其在软骨中相应酶原（前MMP-2）的激活机制尚不清楚。在本研究中，我们检测了人OA关节软骨中膜型1基质金属蛋白酶（MT1-MMP）的表达模式及其与前MMP-2激活的相关性。免疫组织化学研究表明，在所有直接与软骨降解相关的检测样本中，MT1-MMP定位于表层和过渡区的软骨细胞。逆转录聚合酶链反应证实了MT1-MMP mRNA在OA软骨中的主要表达。原位杂交显示OA软骨中MT1-MMP的表达位点为软骨细胞。通过明胶酶谱法和夹心酶免疫测定法表明，OA软骨外植体分泌的前MMP-2水平明显高于正常样本。OA软骨样本中前MMP-2的激活增强，且与软骨中MT1-MMP的表达相关。用表达MT1-MMP的培养软骨细胞制备的质膜以及直接从OA软骨中分离的质膜均可激活前MMP-2。用白细胞介素-1α和/或肿瘤坏死因子-α处理可诱导培养软骨细胞中MT1-MMP基因的表达。这些数据表明，细胞因子诱导的软骨细胞中的MT1-MMP可能在OA关节软骨中前MMP-2的激活中起关键作用，通过ECM降解导致软骨破坏。
