Vainio S, Lehtonen E, Jalkanen M, Bernfield M, Saxén L
Department of Pathology, University of Helsinki, Finland.
Dev Biol. 1989 Aug;134(2):382-91. doi: 10.1016/0012-1606(89)90110-3.
Morphogenesis of the kidney is regulated by reciprocal tissue interactions between the epithelial ureter bud and the metanephric mesenchyme. The differentiation of the kidney involves profound changes in the extracellular matrix, and therefore matrix receptors may have an important role in this process. We studied the expression of syndecan, a cell surface proteoglycan acting as a receptor for interstitial matrix materials, by using a monoclonal antibody against the core protein of the molecule. Syndecan was not detected in the uninduced metanephric mesenchyme. During the formation of the ureter bud from the Wolffian duct, syndecan appeared in the mesenchymal cells around the invaginating bud. Simultaneously with the first branching of the ureter bud, the whole nephric mesenchyme became syndecan positive, but a 3- to 10-cell-thick layer around the branching ureter bud, representing the presumptive tubular cells, was most intensely stained. During the assembly of the mesenchyme cells into pretubular aggregates, syndecan was detected in these aggregates and, to a lesser degree, in the morphologically undifferentiated mesenchyme. Thereafter syndecan was found only in the differentiating epithelium, from which it was gradually lost during maturation of the nephron. It was last detected in the periphery of the kidney, where tubulogenesis still continued. In transfilter cultures we showed that syndecan appeared in the nephric mesenchyme during the period when the mesenchyme becomes programmed to transform into epithelial structures. By using interspecies recombinations and a species-specific antibody we excluded the possibility that syndecan in the mesenchyme would originate from the inductor. We conclude that syndecan expression is regulated by epithelial-mesenchymal interactions. The findings that syndecan appeared as an early response to induction and that its distribution showed both spatial and temporal correlation with kidney morphogenesis suggest an important role for this molecule in development.
肾脏的形态发生受上皮输尿管芽和后肾间充质之间相互的组织相互作用调节。肾脏的分化涉及细胞外基质的深刻变化，因此基质受体可能在这一过程中发挥重要作用。我们使用针对该分子核心蛋白的单克隆抗体，研究了syndecan（一种作为间质基质材料受体的细胞表面蛋白聚糖）的表达。在未诱导的后肾间充质中未检测到syndecan。在输尿管芽从沃尔夫管形成的过程中，syndecan出现在内陷芽周围的间充质细胞中。与输尿管芽的首次分支同时，整个肾间充质变为syndecan阳性，但在分支输尿管芽周围3至10个细胞厚的一层，代表假定的肾小管细胞，染色最为强烈。在间充质细胞组装成肾小管前聚集体的过程中，在这些聚集体中检测到syndecan，在形态上未分化的间充质中也有较少程度的检测到。此后，syndecan仅在分化的上皮中发现，在肾单位成熟过程中逐渐从其中消失。它最后在肾脏周边被检测到，那里肾小管发生仍在继续。在滤膜培养中我们表明，在间充质被编程转化为上皮结构的时期，syndecan出现在肾间充质中。通过种间重组和种特异性抗体，我们排除了间充质中的syndecan源自诱导物的可能性。我们得出结论，syndecan的表达受上皮-间充质相互作用调节。syndecan作为对诱导的早期反应出现，且其分布与肾脏形态发生呈现时空相关性，这些发现表明该分子在发育中起重要作用。
