A New Workflow for Proteomic Analysis of Urinary Exosomes and Assessment in Cystinuria Patients

Cystinuria is a purely renal, rare
genetic disease caused by mutations
in cystine transporter genes and characterized by defective cystine
reabsorption leading to kidney stones. In 14% of cases, patients undergo
nephrectomy, but given the difficulty to predict the evolution of
the disease, the identification of markers of kidney damage would
improve the follow-up of patients with a higher risk. The aim of the
present study is to develop a robust, reproducible, and noninvasive
methodology for proteomic analysis of urinary exosomes using high
resolution mass spectrometry. A clinical pilot study conducted on
eight cystinuria patients versus 10 controls highlighted 165 proteins,
of which 38 were up-regulated, that separate cystinuria patients from
controls and further discriminate between severe and moderate forms
of the disease. These proteins include markers of kidney injury, circulating
proteins, and a neutrophil signature. Analysis of selected proteins
by immunobloting, performed on six additional cystinuria patients,
validated the mass spectrometry data. To our knowledge, this is the
first successful proteomic study in cystinuria unmasking the potential
role of inflammation in this disease. The workflow we have developed
is applicable to investigate urinary exosomes in different renal diseases
and to search for diagnostic/prognostic markers. Data are available
via ProteomeXchange with identifier PXD001430.