Molecular biological approach to the abnormalities of extracelluar matrix of the diabetic nephropathy.

细胞外基质由胶原蛋白、层粘连蛋白和蛋白多糖组成。在糖尿病肾病中，IV型胶原生化性质的改变和蛋白多糖表达减少被认为是糖尿病肾病的主要病理改变，并与肾小球细胞表型变化有关。糖尿病肾病伴肾病综合征患者肾小球基底膜增厚，IV型胶原量增加，密度降低，硫酸乙酰肝素蛋白多糖减少。这些细胞外基质成分的改变可能是导致基底膜的大小和电荷屏障受损以及蛋白尿的原因之一。此外，我们还克隆了一条新的IV型胶原链，即α4链，该链包含NC-1结构域，全长1.9kb。Northern印迹分析显示-9.5kb转录本。Alpha1、Alpha2、Alpha3、Alpha4和基底膜相关胶原(BAC)的免疫荧光研究显示，Alpha1和Alpha2定位于肾小球系膜区和肾小球毛细血管，而Alpha3和Alpha4主要定位于毛细血管壁上。肾小球系膜区有BAC免疫反应。在糖尿病患者的肾脏中，肾小球系膜基质扩张，基底膜增厚，α1-α4链和BAC的表达增加。此外，我们还分析了间质胶原III、V、VI的表达。III型胶原仅在肾脏间质表达，V型和VI型胶原有系膜表达。糖尿病大鼠肾小球系膜区胶原增多。

Extracellular matrix has been shown to be consisted of collagens, laminins and proteoglycans. In diabetic nephropathy, the altertions of biochemical properties of type IV collagen and the decreased expression of proteoglycans are considered to be major pathological changes of the disease and related to the phenotypic changes of glomerular cells. Immunoelectron microscopic studies of diabetic nepropathy patients with nephrotic syndrome showed the thicking of glomerular basement membranes (GBM), increased amount of type IV collagens with decreased density, and decreased heparan sulfate proteoglycan. These alterations of extracellular matrix components seems to contribute to the the impairment of size and charge barrier of the GBM and proteinuria. Furthermore, we cloned a novel chain of type IV collagen, i.e.alpha4 chain, which cDNA (NK4) included NC-1 domain and expands 1.9 Kb. Northern blot analyzes showed -9.5 Kb transcript. Immunofluorescence studies of alpha1, alpha2, alpha3, alpha4, and basement membrane associated-collagen (BAC) showed alpha1 and alpha2 localized to the glomerular mesangial area and glomerular capillary, while alpha3 and alpha4 localized mainly along the capillary wall. BAC immunoreactivity was observed in the mesangial area. In the kidney of diabetic patients, expanded mesangial matrix and thickened GBM showed increased expression of alpha1-alpha4 chains and BAC.Furthermore, we analyzed the expression of the interstitial collagens, such as III,V,VI collagens. Type III collagen exclusively expressed in the interstinum of the kidney and type V and VI collagens had mesangial expressions. In diabetic kidney, these collagens were increased in the mesangial area.