Horster M F, Braun G S, Huber S M
Physiologisches Institut, Universität München, München, Germany.
Physiol Rev. 1999 Oct;79(4):1157-91. doi: 10.1152/physrev.1999.79.4.1157.
Embryonic metanephroi, differentiating into the adult kidney, have come to be a generally accepted model system for organogenesis. Nephrogenesis implies a highly controlled series of morphogenetic and differentiation events that starts with reciprocal inductive interactions between two different primordial tissues and leads, in one of two mainstream processes, to the formation of mesenchymal condensations and aggregates. These go through the intricate process of mesenchyme-to-epithelium transition by which epithelial cell polarization is initiated, and they continue to differentiate into the highly specialized epithelial cell populations of the nephron. Each step along the developmental metanephrogenic pathway is initiated and organized by signaling molecules that are locally secreted polypeptides encoded by different gene families and regulated by transcription factors. Nephrogenesis proceeds from the deep to the outer cortex, and it is directed by a second, entirely different developmental process, the ductal branching of the ureteric bud-derived collecting tubule. Both systems, the nephrogenic (mesenchymal) and the ductogenic (ureteric), undergo a repeat series of inductive signaling that serves to organize the architecture and differentiated cell functions in a cascade of developmental gene programs. The aim of this review is to present a coherent picture of principles and mechanisms in embryonic renal epithelia.
胚胎后肾在分化为成体肾脏的过程中，已成为器官发生普遍接受的模型系统。肾发生意味着一系列高度受控的形态发生和分化事件，始于两种不同原始组织之间的相互诱导相互作用，并在两个主流过程之一中导致间充质凝聚和聚集的形成。这些细胞经历间充质到上皮细胞转变的复杂过程，由此启动上皮细胞极化，并继续分化为肾单位高度特化的上皮细胞群。发育性后肾发生途径中的每一步都由信号分子启动和组织，这些信号分子是由不同基因家族编码的局部分泌多肽，并受转录因子调控。肾发生从深部向皮质外层进行，并由第二个完全不同的发育过程引导，即输尿管芽衍生的集合小管的导管分支。肾源性（间充质）和导管源性（输尿管）这两个系统都经历一系列重复的诱导信号传导，这些信号传导通过一系列发育基因程序来组织结构和分化细胞功能。本综述的目的是呈现胚胎肾上皮细胞中原理和机制的连贯图景。
