Figure 1.

Patterns of injury after ischemic kidney injury.A, the nephron segments of the proximal tubule (red outline) involved in acute kidney injury and their position in the gross structure of the kidney. For clarity, distal segments including the loop of Henle, distal tubule, and collecting ducts are not labeled. B, H&E-stained mouse kidney section 2 days after ischemia–reperfusion injury (IRI) showing injured tubules in the S3 segment. Note tubular dilation, simplification of the epithelium, and intratubular debris (examples: black arrowheads) and casts (example: yellow arrowhead). C, immunofluorescence staining 2 days after IRI for kidney injury marker 1 (KIM-1, purple) and Ki67 (light blue), which mark injured epithelium and proliferating cells, respectively. Note that KIM-1 staining is highly localized to the S3 segment at the border between cortex and medulla. D, H&E staining of a mouse kidney 28 days after IRI. Note the focal area of fibrosis and tubular atrophy with inflammatory infiltrate (white arrow) surrounded by normal tubules. Scale bars represent 1 mm (whole section) and 100 μm (regions of interest).