Fujita Yoshinari, Shiomi Takayuki, Yanagimoto Shigeru, Matsumoto Hideo, Toyama Yoshiaki, Okada Yasunori
School of Medicine, Keio University, Tokyo, Japan.
Arthritis Rheum. 2006 Oct;54(10):3233-43. doi: 10.1002/art.22140.
The proenzyme of matrix metalloproteinase 7 (proMMP-7), which can degrade various extracellular matrix (ECM) and non-ECM molecules after being activated, is overexpressed in osteoarthritic (OA) articular cartilage, but the process of its activation in the cartilage remains unknown. The present study was undertaken to investigate the expression of tetraspanin CD151 in OA cartilage and its involvement in proMMP-7 activation.
The expression of CD151 in articular cartilage was examined by reverse transcription-polymerase chain reaction (RT-PCR), real-time PCR, immunohistochemistry, in situ hybridization, and immunoblotting. Chondrocytes were used to study the interaction between CD151 and proMMP-7, and activation of proMMP-7.
RT-PCR revealed expression of CD151 messenger RNA in all OA cartilage samples, but in only 30% of normal control cartilage samples. Immunohistochemistry and in situ hybridization findings indicated that CD151 was coexpressed with proMMP-7 in chondrocytes, mainly in the superficial and transitional zones of OA cartilage. CD151 immunoreactivity directly correlated with the Mankin score (r = 0.757, P < 0.0001 [n = 30]) and the degree of chondrocyte cloning (r = 0.83, P < 0.0001 [n = 30]) in the cartilage samples. Complexes CD151 and proMMP-7 and their colocalization on the cell membranes were demonstrated by immunoprecipitation and double fluorescence immunostaining of the OA chondrocytes. In situ zymography indicated that chondrocytes exhibit pericellular proteolytic activity, which was abolished by treatment with MMP inhibitors, anti-MMP-7 antibody, or anti-CD151 antibody.
These data demonstrate that CD151 is overexpressed in OA cartilage and suggest that CD151 plays a role in the pericellular activation of proMMP-7, leading to cartilage destruction and/or chondrocyte cloning.
基质金属蛋白酶7原酶（proMMP - 7）在被激活后可降解多种细胞外基质（ECM）和非ECM分子，其在骨关节炎（OA）关节软骨中过表达，但其在软骨中的激活过程尚不清楚。本研究旨在探讨四跨膜蛋白CD151在OA软骨中的表达及其在proMMP - 7激活中的作用。
采用逆转录 - 聚合酶链反应（RT - PCR）、实时PCR、免疫组织化学、原位杂交和免疫印迹法检测关节软骨中CD151的表达。利用软骨细胞研究CD151与proMMP - 7之间的相互作用以及proMMP - 7的激活情况。
RT - PCR显示所有OA软骨样本中均有CD151信使核糖核酸表达，但正常对照软骨样本中仅有30%表达。免疫组织化学和原位杂交结果表明，CD151与proMMP - 7在软骨细胞中共表达，主要在OA软骨的表层和过渡区。软骨样本中CD151免疫反应性与Mankin评分（r = 0.757，P < 0.0001 [n = 30]）以及软骨细胞克隆程度（r = 0.83，P < 0.0001 [n = 30]）直接相关。通过免疫沉淀和OA软骨细胞的双荧光免疫染色证实了CD151与proMMP - 7复合物及其在细胞膜上的共定位。原位酶谱分析表明软骨细胞表现出细胞周围蛋白水解活性，用MMP抑制剂、抗MMP - 7抗体或抗CD151抗体处理后该活性被消除。
这些数据表明CD151在OA软骨中过表达，并提示CD151在proMMP - 7的细胞周围激活中起作用，导致软骨破坏和/或软骨细胞克隆。
