Bromodeoxyuridine Methodology for Labeling Renal Stem Cells During Kidney Development of Mice

A continuous Bromodeoxyuridine (BrdU) labeling approach was used during the whole process of the mice kidney development to explore the best BrdU-labeling time, the distribution of BrdU-retaining cells, and to probe into the niche of stem cells in adult kidney. BrdU was injected intraperitoneally to the mice once daily for 3 consecutive days from day 11.5 of embryonic period (E11.5) to the postnatal day 21.5 (P21.5). The kidneys were harvested 24 h after the last BrdU injection and 6 months of age. A renal injury model of subtotal nephrectomy (Nx) in adult mice treated with BrdU was used to observe the response of BrdU-retaining cells to renal injury. When BrdU labeled at E11.5-13.5, the BrdU-retaining cells were mainly detected in the papilla and inner medulla in adult mice. When BrdU labeled at P0.5-11.5, the BrdU-retaining cells were mainly detected in the inner medulla and outer medulla. When BrdU labeled at P12.5-17.5, the BrdU-retaining cells were mainly detected in the outer medulla. When BrdU labeled at P18.5-21.5, almost no BrdU-positive cells could be found, except the cortex. Seventy-two hours after Nx operation in adult mice by BrdU-labeling at P0.5-2.5 or P15.5-17.5, a significant increase of BrdU-retaining cells was found in many cortical proximal tubules, while a dramatic decrease was detected in medulla near the incision edge. Moreover, most of BrdU-positive cells were not costained with proliferating cell nuclear antigen. The distributions of label-retaining cells in the mice kidney were different if BrdU was administered in different periods of kidney development. Most of BrdU-retaining cells were quiescent, the proximal tubules were the only segments that always contained BrdU positive cells, which may have the niche of stem cells in adult kidney.