小鼠肾发育过程中输尿管芽与肾单位关系的计量学分析

Quantitative analysis on the relationship between ureteric bud and nephron number in developing mouse kidney

目的观察小鼠肾发育过程中输尿管芽（UB）生长方式及其与诱导产生的肾单位数目之间的变化规律。方法应用免疫组织化学技术结合体视学方法，对不同胚（日）龄小鼠输尿管芽发育及肾单位数目进行系统观察和定量分析。结果免疫组织化学结果显示，胚龄12d时，输尿管芽及其分支出现，输尿管芽是以二叉分支方式生长；胚龄14d，输尿管芽诱导的。肾单位出现；胚龄16d至生后5d，输尿管芽不断分支，输尿管芽尖数目及肾单位数目不断增加；生后7d，输尿管芽消失，肾单位数目固定。体视学测量结果显示，胚龄14d至胚龄18d，每个输尿管芽尖可诱导1个肾单位发生；生后1d至生后5d，每个输尿管芽尖可诱导4个肾单位发生。在整个肾发育过程中，输尿管芽可发生10—11次分支。结论肾单位数目与输尿管芽分支程度成正比，但两者之间的比例关系不固定。

Objective To investigate the growth pattern of ureteric bud （UB） and nephron number induced by UB in developing mouse kidney. Methods Immunohistochemical technology and stereological method were used to observe and measure UB and nephron at different developmental stages of embryonic and postnatal mice. Results Immunohistochemical examination showed that ureteric buds surrounded by metanephrogenic tissue were observed in embryonic day 12, and each UB tip branched dichotomisously. In embryonic day 14, nephrons induced by UB emerged. From embryonic day 16 to postnatal day 5, the number of UB tip and nephrons were increased. In postnatal 7, UB disappeared and nephron number was not changed. Stereological examination showed that from embryonic day 14 to 18, each UB tip induced one nephron . From postnatal day 1 to 5, each UB tip induced four nephrons. Those data indicated that a total of 10-11 UB branching events occurred during mouse kidney morphogenesis. Conclusion It is well established that nephron number is proportional to the extent of UB branching that occurs during developing kidney, but it is not constant.