Proliferative capacity of stem/progenitor-like cells in the kidney may associate with the outcome of patients with acute tubular necrosis

Abstract

Animal studies indicate that adult renal stem/progenitor cells can undergo rapid proliferation in response to renal injury, but whether the same is true in humans is largely unknown. To examine the profile of renal stem/progenitor cells responsible for acute tubular necrosis in human kidney, double and triple immunostaining was performed using proliferative marker and stem/progenitor protein markers on sections from 10 kidneys with acute tubular necrosis and 4 normal adult kidneys. The immunopositive cells were recorded using 2-photon confocal laser scanning microscopy. We found that dividing cells were present in the tubules of the cortex and medulla, as well as the glomerulus in normal human kidney. Proliferative cells in the parietal layer of Bowman capsule expressed CD133, and dividing cells in the tubules expressed immature cell protein markers paired box gene 2, vimentin, and nestin. After acute tubular necrosis, Ki67-positive cells in the cortex tubules significantly increased compared with normal adult kidney. These Ki67-positive cells expressed CD133 and paired box gene 2, but not the cell death marker, activated caspase-3. In addition, the number of dividing cells increased significantly in patients with acute tubular necrosis who subsequently recovered, compared with patients with acute tubular necrosis who consequently developed protracted acute tubular necrosis or died. Our data suggest that renal stem/progenitor cells may reside not only in the parietal layer of Bowman capsule but also in the cortex and medulla in normal human kidney, and the proliferative capacity of renal stem/progenitor cells after acute tubular necrosis may be an important determinant of a patient's outcome.

Fig. 1

Presence of Proliferative cells in the adult normal human kidney. Immunocytocehmistry was performed on the sections from normal adult human kidney. Ki67-positive cells were found in cells located in the tubule, intersititium, the parietal layer of Bowman’s capsule and glomerulus as indicated (A). High magnification of images from panel A (B). Double-immunostaining was performed using anti-Ki67 and MCM2, and images were recorded using a two photon laser-scanning confocal microscope. Ki67-positive cells (green) co-expressed MCM2 (red). DAPI (blue) was used to counterstain the nuclei (C). High magnification of images from panel C (D).

Fig. 2

Co-expression of CD133 and Notch1 with Ki67 in the adult normal human kidney. CD133 was expressed in cells located in the parietal layer of Bowman’s capsule (left panel) and brush border of tubule in normal human kidney (right panel) (A). Low magnification of the glomerulus staining with DAPI (blue) (top left panel). Double labeling showed that Ki67-positive cells (red) expressed CD133 (green) (B). Notch1 (green) was highly expressed in the cells located in the parietal layer of Bowman’s capsule and the glomerulus (left panel). Double immunolabeling indicated that Ki67-positive cells (red) in the tubule of kidney expressed Notch1 (green) (right panel) (C). DAPI was used for nuclei counterstaining.

Fig. 3

Co-expression of PAX2, vimentin and nestin with Ki67 in the adult normal human kidney. PAX2 (right panel), vimentin (middle panel) and nestin (right panel) were expressed in cells located in the tubule and intersititium and in the parietal layer of Bowman's capsule and glomerulus of normal human kidney (A). PAX2-positive cells (red) in the tubule co-expressed Ki67 (green) (B). Vimentin-positive cells (red) in the tubule co-expressed Ki67 (green) (C). Immunocytochemistry showed that nestin (red) was expressed in the interstitial cells and glomerular cells (insert). Some of nestin-positive cells in the intersititium co-expressed Ki67 (red). Left panel: low magnification; right panel: high magnification. Nuclei were counterstained with DAPI (blue) (D).

Fig. 4

Expression pattern of proliferative cells in normal and ATN kidney. Expression pattern of Ki67, MCAM2 and PAX2 in normal and ATN kidney (A). Double immunostaining shows that Ki67-positive cells (red) expressed CD133 (green) (top panel) and Ki67-positive cells (green) expressed PAX2 (red) on the section from ATN (bottom panel) (B). Double immunostaining shows that Ki67-positive cells (green) did not express cell death marker, activated caspase-3 form (red) (C).

Fig. 5

Proliferative index in normal and ATN kidney. The ratio of Ki67 positively immunostained nuclei to total nuclei per each section of normal and ATN kidney was considered as a proliferative index (A). The ratio of MCM2 positively immunostained nuclei to total nuclei per each section of normal and ATN kidney was considered as a proliferative index (B). The percentage of PAX2-positive cells in normal and ATN kidney with different outcome (C).