·Twenty stable peritoneal dialysis (PD) patients were divided into two groups, i.e., H group (high/high average) and L group (low/low average) according to the values of peritoneal equilibration test (PET). Overnight PDE 500 mL from each patient was collected, concentrated, and ultracentrifuged to obtain exosomes. Transmission electron microscope (TEM), nanoparticle tracking analysis (NTA) and Western blotting were used to identify and characterize the exosomes. Exosomal miRNAs were extracted and the expression levels of PDE exosomal miR-200a in the two groups were determined by real-time quantitative PCR. The relations between exosomal miR-200a levels and PET values or ultrafiltration volume (UF) were analyzed. The target genes of miR-200a were predicted by Targetscan, miRmap and miRWalk, and DAVID was used to perform gene ontology (GO) enrichment analysis.

·The exosomes extracted from concentrated PDE by ultracentrifugation exhibited a round and bilayer membrane-enveloped vesicle structure under TEM with the diameters ranging from 50-150 nm. The exosomes also expressed the particular molecular marker CD9 and CD63. The relative expression level of PDE exosomal miR-200a in L group was higher than that of H group. The expression levels were negatively correlated with PET values (r=-0.871, P=0.000) and positively correlated with 4 h UF (r=0.448, P=0.048). But there was no relationship between miR-200a and 24 h UF (r=0.355, P=0.125). Bioinformatic results showed that there were 679 target genes of miR-200a that could be predicted by all the three databases. GO analysis suggested that these genes not only participated in positive regulation of mesenchymal cells proliferation, but also focused on ion binding, especially metal cation binding.

·Exosomes indeed exist in PDE. The relative expression level of exosomal miR-200a is higher in the PDE from the patients with low peritoneal dialysis transport characteristics. The relative quantity of miR-200a is negatively correlated with the values of PET and positively correlated with 4 h UF. There are abundant potential target genes of miR-200a, indicating that it may affect the peritoneal transport characteristics by different biological processes.