Abrahamson Dale R, Prettyman A Corinne, Robert Barry, St John Patricia L
Department of Anatomy and Cell Biology, University of Kansas Medical Center, Kansas City, Kansas 66160, USA.
Kidney Int. 2003 Mar;63(3):826-34. doi: 10.1046/j.1523-1755.2003.00800.x.
Alport disease is a heritable basement membrane disorder caused by mutations in genes encoding the alpha3, alpha4, or alpha5 chains of type IV collagen, which normally comprise the collagenous network of mature glomerular basement membranes (GBMs). In Alport disease, the alpha3(IV), alpha4(IV), alpha5(IV) collagen network is absent and substituted for by alpha1(IV), and alpha2(IV) collagen, which normally is present only in developing, immature GBMs. The disease is marked by progressive GBM thickening and delamination, proteinuria, and renal failure. In addition to collagen IV dysregulation, abnormal GBM laminins also occur and may contribute to the pathogenesis of Alport glomerulopathy.
To investigate laminin dysregulation in a mouse model of Alport disease, we used antibodies specific for laminin-alpha1 and -beta1 chains (to recognize laminin-1), and -alpha5 chain (to recognize laminin-11), and evaluated their distribution during glomerular development in alpha3(IV) collagen-deficient mice.
Developing glomeruli of infant alpha3(IV) collagen knockout mice underwent normal down-regulation of laminin-1, but laminin-1 chains were then reexpressed in maturing glomeruli, becoming concentrated in the subepithelial GBM projections typical of Alport disease. Immunoelectron microscopy showed that laminin-1 reexpression took place in both glomerular endothelial cells and podocytes.
The absence of a alpha3(IV), alpha4(IV), alpha5(IV) network may stimulate reexpression of laminin-1 by Alport mouse endothelial cells and podocytes. This abnormal GBM, which is more characteristic of immature glomeruli, may promote podocyte foot process effacement and reversion to a less differentiated state.
Alport综合征是一种遗传性基底膜疾病，由编码IV型胶原α3、α4或α5链的基因突变引起，这些链通常构成成熟肾小球基底膜（GBM）的胶原网络。在Alport综合征中，α3（IV）、α4（IV）、α5（IV）胶原网络缺失，被通常仅存在于发育中的未成熟GBM中的α1（IV）和α2（IV）胶原所取代。该疾病的特征是GBM进行性增厚和分层、蛋白尿和肾衰竭。除了IV型胶原失调外，GBM层粘连蛋白也异常，可能参与Alport肾小球病的发病机制。
为了研究Alport综合征小鼠模型中层粘连蛋白失调情况，我们使用了针对层粘连蛋白α1和β1链（识别层粘连蛋白-1）以及α5链（识别层粘连蛋白-11）的特异性抗体，并评估它们在α3（IV）胶原缺陷小鼠肾小球发育过程中的分布。
幼年α3（IV）胶原敲除小鼠发育中的肾小球经历了层粘连蛋白-1的正常下调，但随后层粘连蛋白-1链在成熟肾小球中重新表达，集中在Alport综合征典型的上皮下GBM突起中。免疫电子显微镜显示，层粘连蛋白-1的重新表达发生在肾小球内皮细胞和足细胞中。
α3（IV）、α4（IV）、α5（IV）网络的缺失可能刺激Alport小鼠内皮细胞和足细胞重新表达层粘连蛋白-1。这种更具未成熟肾小球特征的异常GBM可能促进足细胞足突消失并恢复到分化程度较低的状态。
