Gustafsson Erika, Aszodi Attila, Ortega Nathalie, Hunziker Ernst B, Denker Hans-Werner, Werb Zena, Fassler Reinhard
Department of Experimental Pathology, Lund University, 22185 Lund, Sweden.
Ann N Y Acad Sci. 2003 May;995:140-50. doi: 10.1111/j.1749-6632.2003.tb03217.x.
The cartilage extracellular matrix is composed of a dense collagen network that entraps a range of other specialized proteins important for the proper formation and function of the tissue. Loss of two abundant cartilage components, type II collagen and perlecan, has drastic effects on skeletal development. Both collagen II and perlecan mutants have severe and lethal chondrodysplasia characterized by disorganized growth plate, lack of collagen network, defective endochondral bone formation, and abnormal intervertebral disk development. To test whether the reduced collagen density in the perlecan-null cartilage is due to enhanced activity of collagen-degrading proteinases, we have analyzed gelatinase expression and activity in the mutant tissue. Immunohistochemical analysis revealed a weak, but clear, expansion of MMP-9 deposition into the hypertrophic zone of the perlecan-null growth plate. However, in situ and SDS-PAGE zymography showed that the activity of gelatinases (MMP-2 and MMP-9) is not altered in perlecan-null cartilage, suggesting that they are not primarily linked to the reduced fibrillar network observed in the mutant. Likewise, intercrossing of perlecan mutants onto an MMP-9-null background could not rescue the ultrastructural abnormalities of the perlecan-deficient cartilage.
软骨细胞外基质由致密的胶原网络组成，该网络包裹着一系列对组织的正常形成和功能至关重要的其他特殊蛋白质。两种丰富的软骨成分，即II型胶原蛋白和基底膜聚糖的缺失，对骨骼发育有显著影响。胶原蛋白II和基底膜聚糖突变体均有严重的致死性软骨发育不良，其特征为生长板紊乱、缺乏胶原网络、软骨内骨形成缺陷以及椎间盘发育异常。为了测试基底膜聚糖缺失的软骨中胶原密度降低是否是由于胶原降解蛋白酶活性增强所致，我们分析了突变组织中明胶酶的表达和活性。免疫组织化学分析显示，MMP - 9在基底膜聚糖缺失的生长板肥大区的沉积有微弱但明显的增加。然而，原位和SDS - PAGE酶谱分析表明，基底膜聚糖缺失的软骨中明胶酶（MMP - 2和MMP - 9）的活性没有改变，这表明它们与突变体中观察到的纤维网络减少没有直接关联。同样，将基底膜聚糖突变体与MMP - 9缺失背景杂交也无法挽救基底膜聚糖缺陷软骨的超微结构异常。
