Pathogenic pathways of renal damage in Fabry nephropathy: interplay between immune cell infiltration, apoptosis and fibrosis

Fabry nephropathy is a consequence of the deposition of globotriaosylceramide, caused by deficient GLA enzyme activity in all types of kidney cells. These deposits are perceived as damage signals leading to activation of inflammation resulting in renal fibrosis. There are few studies related to immunophenotype characterization of the renal infiltrate in kidneys in patients with Fabry disease and its relationship to mechanisms of fibrosis. This work aims to quantify TGF-β1 and active caspase 3 expression and to analyze the profile of cells in inflammatory infiltration in kidney biopsies from Fabry naïve-patients, and to investigate correlations with clinical parameters. Renal biopsies from 15 treatment-naïve Fabry patients were included in this study. Immunostaining was performed to analyze active caspase 3, TGF-β1, TNF-α, CD3, CD20, CD68 and CD163. Clinical data were retrospectively gathered at time of kidney biopsy. Our results suggest the production of TNFα and TGFβ1 by tubular cells, in Fabry patients. Active caspase 3 staining revealed that tubular cells are in apoptosis, and apoptotic levels correlated with clinical signs of chronic kidney disease, proteinuria, and inversely with glomerular filtration rate. The cell infiltrates consisted of macrophages, T and B cells. CD163 macrophages were found in biopsy specimens and their number correlates with TGFβ1 and active caspase 3 tubular expression. These results suggest that CD163+ cells could be relevant mediators of fibrosis in Fabry nephropathy, playing a role in the induction of TGFβ1 and apoptotic cell death by tubular cells. These cells may represent a new player in the pathogenic mechanisms of Fabry nephropathy.