Aim: Acute kidney injury (AKI), a global public health issue, not only causes millions of deaths every year, but is also a susceptible factor for chronic kidney disease (CKD). Nephrotoxic drugs are an important cause of AKI. There is still a lack of effective and satisfactory prevention method in clinical practice. This study investigated the protective effect of the exosomes derived from urine of premature infants on cisplatin-induced acute kidney injury. Methods: Isolation of exosomes from fresh urine of premature infants: The characteristics of exosomes were determined by flow cytometry, transmission electron microscopy and Western blotting. A C57BL/6 mice model of cisplatin-induced acute kidney injury was established. The mice in the experimental group were given 100ug exosomes dissolved in 200ul solution. The mice in the control group were given normal saline (200ul). These treatments were performed 24 hours after AKI was induced by intraperitoneal injection of cisplatin. To evaluate renal function, blood was drawn 24 hours after AKI model was established and serum creatinine (sCr) was measured. The mice were euthanized 72 hours after exosome treatment. The kidneys were collected for pathological examination, RNA and protein extraction, and the evaluation of renal tubular damage and apoptosis. In the in-vitro experiment, human renal cortex/proximal tubular cells (HK2) was induced by cisplatin to assess the protective ability of the exosomes derived from urine of premature infants. Quantitative reverse transcription polymerase chain reaction (qRT-PCR) and Western Blotting were used to evaluate the effect of exosomes treatment on the apoptosis of HK2 cells induced by cisplatin. Exosome microRNA sequencing technology and bioinformatics analysis method were applied to investigate the miRNAs enriched in exosomes and their target genes. The dual luciferase gene reporter system was used to detect the interaction of target genes. Results: Treatment of exosomes derived from urine of premature infants could decrease the level of serum creatinine and the apoptosis of renal tubular cell, inhibit the infiltration of inflammatory cell, protect mice from acute kidney injury induced by cisplatin and reduce mortality. In addition, miR-30a-5p was the most abundant miRNA in the exosomes derived from urine of premature infants. It protected HK2 cells from cisplatin-induced apoptosis by targeting and down-regulating the 3'UTR of mitogen-activated protein kinases (MAPK8) mRNA. Conclusions: According to our results, the exosomes derived from urine of premature infants alleviated cisplatin-induced acute kidney injury in mice and inhibited the apoptosis of human proximal tubular cells (HK2) induced by cisplatin in vitro. MiR-30a-5p in exosomes inhibited cisplatin-induced MAPK activation, ameliorated apoptosis, and protected renal function. The exosomes derived from urine of premature infants provided a promising acellular therapy for AKI.

The exosomes derived from urine of premature infants target MAPK8 via miR-30a-5p to protect cisplatin-induced acute kidney injury in mice