Urinary WNT1: a Biomarker of WNT/Beta-Catenin Signaling Activity in Chronic Allograft Dysfunction

Elisenda Banon-Maneus^1,2, Melanie Königshoff¹, Luis F Quintana², Daniel Moya-Rull², Natalia Hierro², Jordi Rovira², Maria Jose Ramirez-Bajo², Fritz Diekmann², Josep M Campistol².

¹Comprehensive Pneumology Center, Ludwig-Maximilians-Universität und Helmholtz Zentrum München, München, Germany; ²Laboratori Experimental de Nefrologia i Trasplantament (LENIT), Hospital Clinic de Barcelona, Barcelona, Spain.

Background: Despite advances in therapeutics, graft loss associated with chronic allograft dysfunction (CAD) remains high. Urinary proteomic analysis is a noninvasive method that could be used to detect and evaluate CAD in renal transplant recipients. Proteomic analysis of the urine showed us that wnt1 it is really increased in patients with advanced CAD. Wnt/b-catenin signaling has been shown to determine epithelial cell fate during development. As aberrant reactivation of developmental signaling pathways has been suggested to contribute to fibrosis, we hypothesized that Wnt/b-catenin signaling is activated in renal grafts. Thus, we quantified the expression and activity of the Wnt/b-catenin pathway in IFTA renal biopsies.

Methodology/Principal Findings: Morning spot urine samples that were collected from kidney transplant recipients with biopsy-proven interstitial fibrosis and tubular atrophy (IFTA) stages 0-I-II/III (n_8/group) under immunosuppressive treatment with tacrolimus plus mycophenolate with or without prednisone. 2DE silver staining and mass spectrometry analyses were used to establish the normal proteome map, and 2DE-DIGE and mass spectrometry were used to identify proteins exhibiting differential abundance. Twenty two proteins were identified as biomarker candidates, but wnt1 looks the most interesting and never related with IFTA.

The expression of 19 Wnt ligands, the 10 receptors (Fzd1-10), as well as the intracellular signal transducers Gsk-3b, b-catenin and Tcf1 was analyzed in healthy kidneys by quantitative real-time (q)RT-PCR. And Wnt ligands (WNT1, 3, 7a, 10b), receptors and co-receptors Fzd1-3, 6 and 8 and intracellular signal transducers Gsk-3b, b-catenin and Lef 1 were analyzed in renal biopsies with different degrees of interstitial fibrosis and tubular atrophy (IFTA 0-I-II and III).

The Wnt/b-catenin pathway is expressed in healthy adult kidney and Wnt1 and 3, Fzd2, 3, 6, and 8, and Lef1 expression was significantly increased in IFTA.

Conclusions/Significance: Our study demonstrates that the Wnt/b-catenin pathway is expressed in adult kidney. Increased Wnt/b-catenin signaling may be involved in epithelial cell injury and hyperplasia, as well as impaired epithelial-mesenchymal cross-talk in IFTA. Thus, modification of Wnt signaling may represent a therapeutic option in IFTA.