Marx M, Daniel T O, Kashgarian M, Madri J A
Department of Pathology, Yale University School of Medicine, New Haven, Connecticut.
Kidney Int. 1993 May;43(5):1027-41. doi: 10.1038/ki.1993.145.
The aim of this study was to test the hypothesis that changes in the extracellular matrix environment regulate rat mesangial cell growth by modulation of the expression of both PDGF-receptor alpha- and beta-subunits. We investigated the mitogenic effects of the PDGF isoforms AA, AB and BB in conventional two-dimensional (2D) culture on laminin, fibronectin, type I, IV and V collagen and in the different spatial organization of matrix in type I collagen gels in three-dimensional culture (3D). In 2D culture PDGF BB was a potent mitogen, AB elicited an intermediate response while AA had no effect on cell proliferation. Extracellular matrix did not modify the PDGF responsiveness in 2D-culture. The different effects of the three PDGF isoforms were due to differential expression and isoform specific association of the PDGF-receptor subunits. Specifically, the beta-receptor was strongly expressed, whereas the alpha-receptor was only barely detectable on the cell surface. Metabolic labeling revealed synthesis and intracellular accumulation of the complete alpha-receptor protein, and treatment with suramin increased its surface expression, suggesting continuous receptor down-regulation by endogenous PDGF. Morphological and ultrastructural analysis in 3D culture revealed a change in mesangial cell phenotype, forming a branching network of multicellular structures. Assessment of proliferation in 3D culture showed quiescent cells and PDGF unresponsiveness. Investigation of the PDGF beta-receptors revealed a rapid down-regulation in 3D culture; both receptor subunits were not detectable on the cell surface. We conclude that 3D culture promotes the induction of a different mesangial cell phenotype.(ABSTRACT TRUNCATED AT 250 WORDS)
细胞外基质环境的变化通过调节血小板衍生生长因子（PDGF）受体α和β亚基的表达来调控大鼠系膜细胞的生长。我们研究了PDGF同工型AA、AB和BB在传统二维（2D）培养中对层粘连蛋白、纤连蛋白、I型、IV型和V型胶原蛋白的促有丝分裂作用，以及在三维培养（3D）中I型胶原蛋白凝胶中不同空间组织的基质上的作用。在2D培养中，PDGF BB是一种有效的促有丝分裂原，AB引发中等反应，而AA对细胞增殖无影响。细胞外基质在2D培养中未改变PDGF的反应性。三种PDGF同工型的不同作用归因于PDGF受体亚基的差异表达和同工型特异性结合。具体而言，β受体强烈表达，而α受体在细胞表面仅勉强可检测到。代谢标记显示完整α受体蛋白的合成和细胞内积累，用苏拉明处理可增加其表面表达，提示内源性PDGF持续下调受体。3D培养中的形态学和超微结构分析显示系膜细胞表型发生变化，形成多细胞结构的分支网络。3D培养中增殖评估显示细胞静止且对PDGF无反应。对PDGF β受体的研究显示在3D培养中受体迅速下调；在细胞表面未检测到两种受体亚基。我们得出结论，3D培养促进诱导不同的系膜细胞表型。（摘要截断于250字）
