Barasch J, Pressler L, Connor J, Malik A
Department of Medicine, College of Physicians and Surgeons, Columbia University, New York, New York 10032, USA.
Am J Physiol. 1996 Jul;271(1 Pt 2):F50-61. doi: 10.1152/ajprenal.1996.271.1.F50.
Nephrons develop from mesenchymal cells that have contacted the ureteric bud (UB). To determine whether cell associated or secreted ureteric molecules induce the mesenchyme, we have isolated UB cell lines from mice transgenic for T antigen. These cells express epithelial and ureteric (Dolichos lectin staining, c-ret, c-met without hepatocyte growth factor) specific markers, which identifies them as authentic UB cells. Medium conditioned by our cells rescues mesenchyme from apoptosis without inducing the appearance of epithelial aggregates. The same was found by culturing mesenchymes upon the apical surface of a UB monolayer. In contrast, tubules were induced in mesenchymes contacting trypsinized pellets of UB cells. As revealed by staining for T antigen and Dolichos lectin or by prelabeling UB cells with 1,1'-dioctadecyl-3,3,3',3'-tetramethylindocarbocyanine perchlorate (DiI), we found that our cells encapsulated the mesenchyme but did not incorporate in the tubules. These data demonstrate that nephrogenesis is stimulated by two distinct ureteric signals, secreted molecules rescue the mesenchyme from apoptosis, whereas diffusion-limited basolateral molecules trigger mesenchymal/epithelial conversion.
肾单位由与输尿管芽（UB）接触的间充质细胞发育而来。为了确定细胞相关的或分泌的输尿管分子是否诱导间充质，我们从转染了T抗原的小鼠中分离出输尿管芽细胞系。这些细胞表达上皮和输尿管特异性标志物（Dolichos凝集素染色、c-ret、无肝细胞生长因子的c-met），这表明它们是真正的输尿管芽细胞。我们细胞的条件培养基可挽救间充质细胞免于凋亡，而不会诱导上皮聚集体的出现。在输尿管芽单层细胞的顶表面培养间充质细胞时也发现了同样的情况。相反，在与经胰蛋白酶处理的输尿管芽细胞团块接触的间充质细胞中诱导出了小管。通过T抗原和Dolichos凝集素染色或用1,1'-二辛基-3,3,3',3'-四甲基吲哚羰花青高氯酸盐（DiI）对输尿管芽细胞进行预标记发现，我们的细胞包裹了间充质细胞，但未融入小管。这些数据表明，肾发生受到两种不同的输尿管信号的刺激，分泌的分子可挽救间充质细胞免于凋亡，而扩散受限的基底外侧分子则触发间充质/上皮转化。
