LAUSR

A major complication primary focal segmental glomerulosclerosis (FSGS) is its recurrence after kidney transplantation that happens in 30 to 40% of the patients. The diagnosis of this relapses is not always easy as the histological lesions are not highly specific and appear after the proteinuria increase. Currently, there are no accurate biomarkers to detect FSGS recurrence. Our group identified a modified form of Apolipoprotein A-I (ApoA-I), named ApoA-Ib, specifically present in urine of recurrent FSGS patients after kidney transplantation. Aberrant forms of ApoA-I have also been described in urine of native primary FSGS patients and have associated this feature to a prominent staining of ApoA-I at the apical membrane of the tubular cells. In this study we aim to analyze the ApoA-I distribution in kidney allograft biopsies of recurrent FSGS patients. We detected ApoA-I by immunohistochemistry in kidney allograft biopsies of patients with FSGS relapse after kidney transplantation (urinary ApoA-Ib positive) and in kidney allograft biopsies of patients with a disease different from FSGS in the native kidney (No-FSGS, urinary ApoA-Ib negative). In ApoA-Ib positive recurrent FSGS patients, ApoA-I was prominently localized at the brush border of the tubular cells while in the No-FSGS patients ApoA-I was found along the cytoplasm of the tubular cells (Figure 1). The localization of ApoA-I at the brush border of the tubular cells is a specific feature of primary FSGS in relapse. This suggests that ApoA-I staining in kidney biopsies, coupled with ApoA-Ib measurement in urine, could be used as a diagnostic tool of primary FSGS relapse after kidney transplantation due to its highly specific tubular distribution.