EARLY EFFECTS OF EXTRACELLULAR VESICLES SECRETED BY ADIPOSE TISSUE MESENCHYMAL CELLS IN RENAL ISCHEMIA FOLLOWED BY REPERFUSION: MECHANISMS RELY IN THE RESTORATION OF THE REDOX TISSULAR ENVIRONMENT

Abstract

<h3>Background</h3> The acute kidney injury (AKI) caused by ischemia followed by reperfusion (I/R) is one of the more frequent and severe processes, which, with very high mortality, affects renal structures and function. The first hours of lesion are critical for organ recovery, but the mechanisms of lesions to support early beneficial therapeutic actions are not well understood. AKI is characterized by intense production of anion superoxide (O2•-) and oxidative damage. In this study we investigated whether extracellular vesicles secreted by adipose tissue mesenchymal cells (EVs) administrated at the moment of reperfusion, suppresses the exacerbated mitochondrial O2•- formation in the first 24 h after I/R. <h3>Methods</h3> Rats were submitted to bilateral renal arterial clamping (30 min) followed by 24 h of reperfusion. The animals received subcapsularly EVs (I/R+EVs group) or saline (I/R group). The 3rd group was of the false-operated rats (SHAM). Mitochondria were isolated from proximal tubule cells and immediately used. EVs were characterized by cytometry (CD9, TSG101, CD63, CD81) and transmission electron microscopy. The probe Amplex Red™ was used to measure mitochondrial O2•- formation and MitoTracker® Orange to evaluate the mitochondrial electrical potential (Δψ). In vitro studies were carried out by using human renal cells (HK-2) co-cultured or not with EVs under hypoxia conditions. <h3>Results</h3> Administration of EVs to I/R rats restored O2•- formation to SHAM levels in all mitochondrial functional conditions: non-phosphorylating, phosphorylating, with ATP synthesis blocked and uncoupled. Proton leak was not modified. During this period, AKI remained active, as demonstrated by qRT-PCR analysis of the lesion biomarkers Kidney Injury Molecule-1 and Neutrophil Gelatinase-Associated Lipocaline. Tubular catalase and superoxide dismutase mRNA remained low. Heme oxygenase-1 (HO-1) was intensely upregulated. The co-cultures of HK-2 cells with EVs revealed decrease of apoptosis. <h3>Conclusions</h3> These findings provide evidence that the mechanisms in which rely the early recovery by EVs of the renal structure and function after I/R are those related with the normalization of the mitochondrial redox environment and open new vistas for the acellular treatment of AKI.