SUN-316 Binding of β-catenin to TCF1 and FoxO1 controls TGF-beta fibrogenic signalling pathways and predicts adverse outcomes in transplanted kidneys

Abstract

Chronic injury and maladptive fibrotic repair in kidney transplants remains the major cause of allograft loss. Transforming growth factor β (TGF-β) is a key cytokine causing fibrosis. Our recent work has demonstrated that β-catenin binding to Foxo or TCF determines the signaling direction of TGF-β, oscillating between profibrotic and anti-inflammatory pathways in murine models of kidney fibrosis. To explore the relevance of our findings to human disease, we examined β-catenin/FoxO1 and β-catenin/TCF1 in relation to the severity of kidney inflammation, fibrosis and dysfunction in biopsies of kidney transplant patients. Our aim was to examine control of fibrogenic pathways, and determine their prognostic value in clincially relevant outcomes in kidney transplantation. We simultaneously quantified binding of FoxO1 and TCF1 to β-catenin within tubular cells using a proximity ligation assay in 164 transplanted kidneys. eGFR and serum creatinine were measured on the day of biopsy and all biopsies were evaluated for fibrosis by renal pathologists according to the Banff classification. The ratio of β-catenin/TCF1 to β-catenin/FoxO1 binding (TF ratio) was calculated, and multivariable linear and logistic regression models were used for predictive analysis. Cox regression analysis was used to explore the relationship between TF ratio and chronic fibrosis. ROC curve was used for specificity and sensitivity analysis. The one month TF ratio correlated with reduced eGFR (r=-0.556, P<0.001) and increased serum creatinine (r=0.507, P<0.001), albuminuria (r=0.276, P=0.036) Banff ci (r=0.273, P=0.002) and ct scores (r=0.316, P<0.001) at 12 months in kidney transplant patients. Using multivariable linear regression, one year eGFR was only predictable by eGFR (β=0.548, p<0.001) and TF ratio (β=-5.905, p=0.002) at one month. Progression to 1-year moderate fibrosis (Banff ci≥2), was predicted by one month TF ratio (OR=3.221, 95%CI 1.610-6.444, P<0.001) adjusted for baseline pathology using logistic regression. Multivariable models confirmed TF ratio was a consistent and independent risk factor for progressive fibrosis, withstanding adjustment for multiple confounding clinical risk factors. The adjusted hazard ratio of one month TF was 1.773 (95%CI 1.416-2.221, P<0.001). The one month TF ratio predicted Banff ci≥1 fibrosis (AUC=0.717, 95%CI 0.522-0.712, P<0.001) or ci≥2 fibrosis (AUC=0.769, 95%CI 0.660-0.857, P<0.001) at 12-months. The predictive ability of one month TF ratio for 12 month functional impairment was impressive (AUC 0.817, 95%CI 0.746-0.887, P<0.001). The full model including TF ratio was optimal and highly predictive of late renal impairment (AUC 0.914, 95%CI 0.863-0.964, P<0.001). This study demonstrated that differences in binding of TCF1 or FoxO1 to β-catenin affects the direction of fibrogenic signalling and renal transplant outcomes, including intra-renal fibrogenesis and inflammation. The TF ratio at one month was associated with adverse renal fibrosis and clinical outcomes at one year. It may serve as a novel and powerful prognostic biomarker of progressive fibrosis, proteinuria and graft dysfunction. Altering the balance of β-catenin-associated transcriptional activity may be an interventional target for preventative anti-fibrotic therapy.