Localization of proliferating cell nuclear antigen, vimentin, c-Fos, and clusterin in the postischemic kidney. Evidence for a heterogenous genetic response among nephron segments, and a large pool of mitotically active and dedifferentiated cells.

Abstract

The mechanisms leading to the recovery of the kidney after ischemic acute renal failure are poorly understood.To explore the role played by mitogenesis and dedifferentiation in this re- pair process and to identify whether the genetic response of the nephron segments reflects the level of susceptibility to injury, the temporal and nephron segment expressions of various pro- teins implicated in mitogenesis, differentiation, and injury were determined.Proliferating cell nuclear antigen (PCNA), a marker for the G1-S transition in the cell cycle and hence mito- genesis, was detected primarily in the S3 segment of the proxi- mal tubule, with maximal expression at 2 d postischemia.Vimentin, normally present in mesenchymal cells but not epithelial cells, and hence a marker for the state of differentiation, was prominently expressed in the S3 segment 2-5 d postische- mia.In the S3 segments in the outer stripe of the medulla cells that stained positively for PCNA also stained positively for vimentin.Clusterin, a marker for cell injury, was expressed primarily in the S3 segment and in the distal tubule with dis- tinct staining patterns in each segment.None of the cells that stained with clusterin antibodies were positively stained with PCNA or vimentin antibodies.Likewise, none of the PCNA or vimentin-positive cells expressed clusterin at detectable levels.Thus, in the S3 segment, where there is significant ischemic injury, surviving cells express markers indicating that they un- dergo mitogenesis and dedifferentiate in the postischemic pe- riod.While there is some expression of c-Fos in the S3 seg- ment, c-Fos was expressed predominantly, at 1 and 3 h postischemia, in the nuclei of the distal nephron, particularly in the thick ascending limb.The data support the view that the ma- ture renal S3 segment epithelial cell can be a progenitor cell.(J.Clin.Invest.1994.93:2175-2188.) Key words: acute renal fail- ure * gene expression -ischemia -kidney -tissue repair Proliferating cell nuclear antigen (PCNA), I a DNA polymer- ase 6-associated protein, was used as a marker for cell prolifera- tion.PCNA-labeled nuclei identify a population of cells in late GI and early S phases ofthe cell cycle (10).Vimentin was used as a marker of differentiation.Vimentin is an intermediate filament protein that is expressed in mesenchymal tissue but not in normal differentiated kidney epithelial cells.The expres- sion pattern of c-Fos, the product of the c-fos immediate-early gene, was also evaluated.This gene is induced in a number of 1. Abbreviation used in this paper: PCNA, proliferating cell nuclear antigen.