In our previous study of the healthy human kidney, we identified a small subpopulation of PT cells that coexpressed the intermediate filament vimentin, which typically marks mesenchymal cells such as fibroblasts and pericytes.36 Vimentin-positive PT cells have previously been isolated in human and murine models of ischemia and postulated as a phenotypically distinct population of transiently dedifferentiated epithelial cells that may be injured, fibrotic, or regenerative37-39 and thus may serve as a precursor to allograft fibrosis.40 This evidence concerns the gene VIM and ischemia.