FP264
URINARY MICROVESICLES AS A SOURCE OF KIDNEY DYSFUNCTION BIOMARKERS IN DRUG- INDUCED ACUTE KIDNEY INJURY Free

INTRODUCTION: Extracellular vesicles are membrane-enclosed structures that can be released by many cell types into different biological fluids, including plasma and urine. These structures are a heterogeneous group of particles defined by their size, density, composition and site of origin, including exosomes, microvesicles (also termed ectosomes) and apoptotic bodies. It was thought that vesicles simply served as "garbage bags" for cells to eliminate unwanted components. But thanks to recent findings, we know that they play a relevant role in a wide variety of functions. Their composition, which consists of molecular constituents from their original cells, including proteins, lipids, mRNA and microRNA (miRNA), make them promising biomarkers of certain pathologies, and thus they are a potential diagnostic tool. Acute kidney injury (AKI) is defined as an abrupt decrease in kidney function. An increasing number of epidemiological studies show that AKI is a risk factor for chronic kidney disease, cardiovascular mortality and new episodes of AKI. Diagnosis of renal function is mainly based on serum creatinine measurement, but this is not a good marker of kidney injury because, at least, 60% of renal mass must be lost to induce an increase. Several AKI urinary biomarkers have been identified but they are not sensitive and specific early markers of renal injury. For this reason, we study these microvesicles as a possible source of biomarkers in an experimental model of drug (cisplatin, gentamicin)-induced AKI.

METHODS: Male Wistar rats were treated with a single dose of cisplatin (5 mg/kg) or six doses of gentamicin (150 mg/kg) (both AKI groups) or saline (control group). Urine and blood samples were collected in days 2, 3 and 4 in the cisplatin group and days 3, 4, 5 and 6 in the gentamicin group (AKI development, serum creatinine (sCr)>2). Urinary microvesicles were isolated using a commercial kit for their precipitation and purification, and subsequently lysed. Protein concentration was measured with a protein assay kit. Protein extracts were analyzed by Western blot and ELISA.

RESULTS: Rats receiving cisplatin and gentamicin developed AKI (with increased sCr). Western blot analysis of UVB-1 and UVB-2 molecules expression in the urinary vesicular fraction showed the presence both molecules on days 2, 3 and 4 after cisplatin treatment. In addition, we found these molecules on days 4, 5 and 6 of gentamicin treatment. UVB-1 and UVB-2 do not appear in the urine of control rats.

CONCLUSIONS: UVB-1 and UVB-2 have enough sensitivity and specificity to predict an episode of AKI, as they appear in urine before AKI development (day 4 after cisplatin treatment, day 6 of gentamicin treatment). Therefore, these molecules are good candidates to generate a new diagnostic system to improve the monitoring of AKI caused by cisplatin and gentamicin nephrotoxicity.