三维可视化肾输尿管芽树状结构基础上其分支模式区域特征及分子机制研究

统计资料表明，出生时肾单位数量（nephron endowment）存在个体差异且受宫内环境影响，决定生后心血管系统健康及肾脏衰老进程。输尿管芽（UB）分支是决定肾单位数量的首要因素。它以出芽方式从中肾管侵入到后肾，在后肾内进行反复二杈分支，分支末端在被膜下的生肾区诱导后肾肾单位祖细胞产生肾单位。然而，UB二杈分支模式难以解释其与最终产生肾单位数量的悬殊比例，侧支模式也只被体外实验证实。“存在其它可调控分支模式”是该领域尚需解决的课题之一。课题组前期采用三维可视化技术观察到，肾发生晚期，生肾区出现大量短茎芽泡与UB二杈分支相连，每个芽泡常连接2~3个肾单位，故提出本项目工作假说：UB在生肾区以“出芽”模式分支，这种区域及时间依赖的分支模式是分子驱动的。为此，本项目拟三维可视化多个时间节点UB树状分支结构，检测并定位UB分支区域差异基因及蛋白，并分析其可能的信号通路及可调控的机制，同时进行结构定位，刻画分支模式的区域特征，从而揭示肾单位数量的可控机制，进一步完善肾发生理论。

Statistical data show that nephron endowment varies individually under the intrauterine environment, and determines the post-natal cardiovascular system health and renal aging. Ureteric bud (UB) branching is the primary determinant for nephrogenesis. It invades the metanephros by budding from nephric duct, then repeatedly bifurcates. The tip of the branch induces nephron progenitors to initial nephrogenesis at subcapsular area, nephrogenic zone. However, the UB bifurcation model fails to explain the large ratio of UB branches tips to the ultimate number of nephrons, and the lateral branching model is only confirmed by in vitro experiments.The existence of the modulated branching model is one of the unsolved problems in this field. Previously, using 3D visualization technology, our group observed at the serial sections of late stage of the developing mouse kidneys, that at nephrogenic zone, appearred thousands of sprouting UB branches with ampullary tips connecting 2 to 3 nephrons, like sprouting in spring. We, therefore, put forward the present project working hypothesis: UB at nephrogenic zone branches in the pattern of "the budding" mode, this region-dependent branching mode must be molecular driven. To this end, this project intends to visualize in 3D UB arborization structure at multiple developing time points, detects the difference of the regional molecules, analyze the probable signal pathway, therefore the mechanisms. Meanwhile, the regional differential genes or proteins will be localized in the structures, in order to describe the regional characteristics of the branching modes, so as to reveal the controllable mechanism of nephron number, and further improve the theory of nephrogenesis.