Morphometry of the ureteric bud branching in the developing mouse kidney / 解剖学报

ABSTRACT

[Abstract] Objective To investigate the branching pattern of the ureteric bud and the number of the nephron induced by each ureteric bud tip, through the three-dimensional tracing of the ureteric tree, combined with the morphological analysis and measurement of the ureteric tree. Methods The kidneys were obtained from three mice at various developing time points and prepared for paraffin and epoxy sections. Then the microscopic images were digitized and aligned from these sections. Based on the computer-assisted tracing and visualization of ureteric tree, the number of branches and the nephron induced by each ureteric bud tip were obtained by counting. In addition, paraffin sections were stained with HE staining for morphological observation of nephrogenic zone and ureteric bud, while in order to reflect the density of the ureteric bud tips at nephrogenic zone, the distance between two neighboring ureteric bud tips was measured aided with the Claudin-7 immunohistochemical staining. Results The ureteric bud branching tree revealed that the initial bifid iterative branching formed the framework of renal medulla, the branching became complicated and dense in cortex and nephrogenic zone, while the distance between ureteric bud tips were also decreasing. The number of the nephron induced by each ureteric bud tip increased from one (E14. 5) to two (E17. 5), and occasionally to three. Conclusion Threedimeasional Visualization of ureteric bud branching tree reveals regional complication, suggesting molecules in different regions drive different branching patterns; While the density of the ureteric bud tips at nephrogenic zone increases corresponding to decreasing of thickness of the nephrogenic zone, and the disappearance of the ureteric bud tips after birth is also consistent with the gradual consumption of nephron progenitor cells.