Avaliação imuno-histoquímica dos marcadores de lesão endotelial fator de von Willebrand, t-caderina e caveolina-1 em biópsias de enxerto renal

Abstract

The diagnosis of antibody-mediated rejection (AMR) in kidney allograft biopsies still represents a challenge for clinicians and pathologists. There are scarce reports evaluating endothelial-associated transcripts in kidney allograft biopsies by immunohistochemistry (IHC). This study aimed to evaluate the IHC expression Caveolin-1 (Cav), Von Willebrand Factor (Vwf) and T-Cadherin (Cad) in biopsies with antibody-mediated changes (AMC) and Interstitial Fibrosis and Tubular Atrophy of Unknown Etiology (IF-TA), and its association with laboratorial and morphological parameters of Antibody-mediated rejection (AMR). To analyze the association of IHC expression and the risk of graft loss in samples with IF-TA. This is an observational study with 2 lines of investigation: cross-sectional (Research 1, including samples with AMC and IF-TA) and retrospective cohort (Research 2, including IF-TA cases). All cases were classified and grouped according to the following information: DSA, microvascular inflammation (MVI), C4d and AMR diagnosis. The patients of Research 2 were followed for 3 years after the biopsy. We used the AUC-ROC test to identify the cut-off values with highest accuracy to predict graft failure. The analysis of risk factors for graft loss was tested by Cox regression test (univariate and multivariate) (p < 0,05). 114 samples with AMC and 72 diagnosed as IF-TA were selected. Vwf showed higher median expression in samples with MVI > 1 (61,7%, IQR 43,0%) (p < 0,001), diffuse C4d positivity (62,9%, IQR 49,0%) (p < 0,001), DSA (59,0%, IQR 35,3% vs. 38,4%, IQR 16,9%) (p = 0,016) and AMR (54,0%, IQR 44,7% vs. 21,5%, IQR 8,4%) (p < 0,001). Cad had higher median expression in cases with MVI > 1 (48,7, IQR 20,0%) (p = 0,013), focal C4d positivity (55,1%, IQR 29,9%) (p = 0,006) and AMR (16,5%, IQR 36,8% vs. 0,0%, IQR 18,4%) (p < 0,001). The positivity was higher in chronic AMR (30,0%, IQR 44,2%) (p = 0,001). We observed higher Cav median positivity in biopsies with MVI > 1 (0,0%, IQR 6,6%) (p = 0,024) and confirmed as AMR (0,0%, IQR 5,0% vs. 0,0%, IQR 0,0%) (p = 0,001). Vwf had the highest accuracy to predict graft loss (AUC = 0,637, CI 95% 0,486-0,788) (p = 0,101). The samples with Vwf staining in more than 10% percent of peritubular capillaries and vasa recta presented lower graft survival in 3 years when compared with Vwf < 10% cases (p = 0,006). The multivariate analysis showed that Vwf wan as independent risk factor for graft failure (HR = 2,88, CI 95% 1,03-8,02, p = 0,043). The other two markers were not associated with graft loss. The IHC expression of Vwf, Cad and Cav showed association with microvascular injury parameters. The Vwf > 10% staining in IF-TA biopsies was a predictor of graft loss.