Urinary Podocyte Loss Is a More Specific Marker of Ongoing... : Journal of the American Society of Nephrology (original) (raw)

Pathophysiology of Renal Disease and Progression

Urinary Podocyte Loss Is a More Specific Marker of Ongoing Glomerular Damage than Proteinuria

Yu, Donghai*,†; Petermann, Arndt*; Kunter, Uta*; Rong, Song*,†; Shankland, Stuart J.‡; Floege, Juergen*

* Department of Medicine, Division of Nephrology and Clinical Immunology, University of Aachen, Germany; † Tongji Medical College, HuaZhong University of Science and Technology; Wuhan; China; ‡ Department of Medicine, Division of Nephrology, University of Washington School of Medicine, Seattle, Washington

Address correspondence to: Dr. Arndt Petermann, Division of Nephrology and Clinical Immunology, RWTH Aachen, Pauwelstrasse 30, Aachen NRW 52057, Germany. Phone: +49-0-241-8089-531; Fax: +49-0-241-8082-446; E-mail: [email protected]

Received February 11, 2005. Accepted March 4, 2005.

Published online ahead of print. Publication date available atwww.jasn.org.

D.Y. and A.P. contributed equally to the study.

Abstract

Podocyte loss contributes to the development of glomerulosclerosis. Although podocyte detachment has been recognized as a new mechanism of podocyte loss in glomerular diseases, its time course and relationship to disease activity are not known. Urinary excretion of viable podocytes was quantified in two models of transient glomerular injury, i.e. , rats with puromycin aminonucleoside-induced nephrosis (PAN) and mesangioproliferative nephropathy (anti-Thy 1.1 nephritis model), as well as in a model of continuous glomerular injury, i.e. , hypertensive nephropathy (5/6-nephrectomy model), and in aging rats. The number of glomerular Wilm's tumor (WT)-1-positive podocytes and the glomerular expression of cell-cycle proteins in vivo were assessed. Urinary podocyte loss occurred in both primary (PAN) and secondary (anti-Thy 1.1 nephritis) in parallel to the onset of proteinuria. However, subsequently proteinuria persisted despite remission of podocyturia. In continuous glomerular injury, i.e. , after 5/6-nephrectomy, podocyturia paralleled the course of proteinuria and of systemic hypertension, whereas no podocyturia became detectable during normal aging (up to 12 mo). Despite podocyte detachment of varying degrees, no decrease in glomerular podocyte counts ( i.e. , WT-1 positive nuclei) was noted in either disease model. Podocyturia in the PAN and anti-Thy 1.1 nephritis model was preceded by entry of glomerular podocytes into the cell cycle, i.e. , cyclin D1, cdc2, and/or proliferating cell nuclear antigen (PCNA) expression. Podocyturia is a widespread phenomenon in glomerular disease and not simply a reflection of proteinuria because it is limited to phases of ongoing glomerular injury. The data suggest that podocyturia may become a more sensitive means to assess the activity of glomerular damage than proteinuria.