Figure 5.

[^99mTc]-PBT-Fc detects acute kidney injury in mice. A. Post IRI injury (with 30 min clamping) as early as 1 and 3 days already showed reduced tracer signals (arrows) as compared to the contralateral healthy kidneys. Concurrent bladder signal (arrowheads) of the tracer was also observed, likely attributed to tracer leakage from the injured kidneys. Heatmap scale in %ID/cm³. B. Masson trichrome stain of sham and IRI surgery kidneys showed no fibrosis in these acute stages (1- and 3- days post-surgery). However, extensive tubular damage was observed as early as 1 or 3 days after IRI. The arrows indicate impaired/necrotic tubules. The lower panel shows semi-quantification results of the injured tubules (IRI vs. sham). Ten randomly chosen images in each group were used for the quantification. ***, p < 0.001. C. Immunofluorescence detection of PBT-Fc (with DAPI counterstaining) in acutely injured kidneys (1 h after IRI) with a range of severity (20 min, 30 min or 45 min IRI). Sham kidneys from unclamped contralateral kidneys were used as controls, which showed relatively even level of PBT-Fc staining at tubular basement membrane in a mesh-like pattern (middle panels). In contrast, the IRI kidneys all had areas of loss-of-signal (between dotted lines and arrows), suggesting nephron dysfunctions either in glomerular filtration or in tubular reabsorption, or in both. IRI severity seemed correlate with the degree and extend of loss-of-tracer incorporation.