Virchows Arch (2006) 448: 485–492 DOI 10.1007/s00428-005-0134-9 ORIGINAL ARTICLE Jun Zou . Eishin Yaoita . Yusuke Watanabe . Yutaka Yoshida . Masaaki Nameta . Huiping Li . Zhenyun Qu . Tadashi Yamamoto Upregulation of nestin, vimentin, and desmin in rat podocytes in response to injury Received: 20 July 2005 / Accepted: 15 November 2005 / Published online: 18 January 2006 # Springer-Verlag 2006 Abstract Podocytes in the renal glomerulus express un- usual intermediate filament (IF) proteins for epithelial cells. To gain insight into the role of IF proteins in podocytes, we investigated the expression of nestin, vimentin, and desmin in puromycin aminonucleoside (PAN) nephrosis. A West- ern blot analysis for nestin, vimentin, and desmin demon- strated their exclusive expression in glomeruli and showed their increase in expression in nephrotic glomeruli. Immu- nolocalization studies showed nestin and vimentin to be located predominantly in the podocytes in both normal and nephrotic glomeruli and that enhancement of desmin stain- ing only occurred in podocytes. A ribonuclease protection assay showed high levels of vimentin and nestin expression in normal glomeruli and an upregulation of all three IF transcripts in nephrotic glomeruli. One day after the PAN injection, however, the vimentin transcripts were found to already have significantly increased, whereas those of nestin or desmin showed no such increase. These findings indicate that podocytes express three IF proteins, namely, vimentin, desmin, and nestin, which are differentially reg- ulated in response to injury. An upregulation of IF proteins may increase the mechanical stability of cells, thus enabling podocytes to undergo morphological changes on the tensile glomerular capillary wall. Keywords Kidney . Intermediate filament . Nestin . Vimentin . Injury Introduction Visceral epithelial cells of renal glomeruli, referred to as podocytes, are located on the glomerular basement mem- brane (GBM) as the terminal element in the filtration barrier. They have adapted themselves to facilitating the bulk flow of the glomerular filtrate through the intercellular spaces or filtration slits. Such adaptation has made podo- cytes a unique epithelium regarding their morphology, es- pecially their cytoskeleton. Podocytes consist of a cell body, several primary processes, and numerous foot pro- cesses. In their cell body and primary processes, micro- tubules and intermediate filaments (IFs) dominate, whereas microfilaments are densely accumulated in the foot pro- cesses. Among the known cytoskeletal proteins, IF proteins are the most characteristic of podocytes. IF proteins are characterized by a considerable divergence, which derives from a variety of gene products employed in a fashion that is specific to both the cell type and stage of differentiation. Cytokeratins are typically found in epithelia, vimentin in mesenchyme, desmin in muscle, glial fibrillary acidic protein (GFAP) in astrocytes, and nestin in neuroepithelial stem cells [4, 29]. Although podocytes can be considered epithelial cells according to the classic definition [2], IFs of podocytes do not contain cytokeratins, but instead, react strongly to immunostaining for vimentin [1, 10, 16, 25, 30]. IFs form a continuous structural network extending from the nuclear surface to the cell periphery. In addition to their significant contribution to the mechanical integrity of cells and tissues, IFs play a crucial role in a variety of cellular functions, which range from the determination of cell shape and motility to cell cycle control and signal transduction [4, 29]. Tissue injury is often accompanied by changes in the IF J. Zou . E. Yaoita (*) . Y. Yoshida . H. Li . Z. Qu . T. Yamamoto Department of Structural Pathology, Institute of Nephrology, Niigata University Graduate School of Medical and Dental Sciences, 1-757 Asahimachi-dori, Niigata 951-8510, Japan e-mail: ren-path@med.niigata-u.ac.jp Tel.: +81-25-2272152 Fax: +81-25-2270768 Y. Watanabe Department of Nephrology, Saitama Medical College, Saitama, Japan M. Nameta Cooperative Laboratory of Electron Microscopy, Niigata University, Niigata, Japan