SUN-045 URINARY EXTRACELLULAR VESICLES AS BIOMARKER OF RENAL TUBULAR INJURY

Abstract

Extracellular vesicles (EV) are microstructures that participate in cellular communication. They are released by all biological fluids and are carriers of proteins, lipids, DNA, RNA mainly miRNA, that reflect their cell of origin. Among their populations, we can mention microvesicles and exosomes. Exosomes are structures that are 40-150 nm and have preserved proteins, such tetraspanins CD9, CD63 and CD81. They are released after injury, including in acute renal injury. Urinary exosomes (uEV) are potential marker of renal tubular injury. However, few studies have confirmed the origin of exosomes excreted in the urine. This study aims to compare the clearance of fluorescent beads similar to exosomes with the clearance of inulin and creatinine, substances excreted in the urine only by glomerular filtration. This strategy aims to determine whether uEV come from the kidney itself or from systemic origin through glomerular filtration and/or tubular secretion. Wistar rats were anesthetized, submitted to an intrajugular injection of inulin (10%) or fluorescent beads (0.1%). Serum and urine samples were collected before and 2h after the beginning of the experiment. The clearance of inulin, creatinine and fluorescent beads were determined by respective quantifications in serum and urine samples. Creatinine and inulin concentrations were determined by spectrophotometry and beads concentrations were determined by fluorescence quantification by Nanoparticle Tracking Analysis (NTA). The location of beads in renal tissue was determined by immunofluorescence microscopy. According to the NTA method, the beads commercially obtained had a diameter of 97 nm, consistent with the exosomes. There was no significant difference between creatinine clearances in the group inulin (1.13 ± 0.31 mL/min) or beads (1.13 ± 0.17 mL/min) at the end of the experiment, suggesting that administration of the particles did not alter renal function. On the contrary, at the end of the experiment, the clearance of beads was significantly lower (0.26 ± 0.26 mL/min) than inulin clearance (2.02 ± 0.29 mL/min), suggesting that particles of similar diameter to exosomes are poorly filtered by the glomerulus. Additionally, we identified the beads in the glomerulus and peritubular space, demonstrating their presence in the kidney. However, we observed an increase in the clearance of non-fluorescent particles compared to fluorescent ones, suggesting that most of the uEVs come from the urinary system itself. This work suggests that uEVs released in the urine come from the urinary system itself, reinforcing its potential as a biomarker for kidney diseases, like acute kidney injury and renal tubular injury.