To detect the changes in the expression of plasma exosomal miR-21, miR-210 and miR-4639 in renal transplant recipients, and to analyze the diagnostic value of miR-21, miR-210 and miR-4639, and combined use of them for chronic allograft nephropathy (CAN).

The clinical data of kidney transplant recipients in the Department of Urology, the Third Affiliated Hospital of Soochow University from January 2018 to January 2019 were retrospectively analyzed. Thirty-four kidney transplant recipients were enrolled and divided into CAN group and control group. Plasma exosomes were isolated by gel exclusion chromatography, and the particle size analysis of exosomes was detected by Nanoparticle NS300. Expression of exosome surface markers (CD63 and Alix) were analyzed by western blotting (WB). The chi-square test was used to compare the gender ratio of the CAN group and the control group. Age, serum creatinine, urea nitrogen and estimated glomerular filtration rate (eGFR) (last time before transplantation) of the 2 groups of recipients were compared by group t test. The receiver operating characteristic (ROC) curve was used to evaluate the diagnostic efficacy of plasma exosomal miR-210, miR-21 and miR-4639 for CAN after renal transplantation. P<0.05 was considered statistically significant.

There was no statistically significant differences in gender, age, serum creatinine, urea nitrogen and eGFR before transplantation between the CAN group (n=18) and the control group (n=16) (χ²=0.04, t=0.86, -1.84, -1.83 and 0.85, P all >0.05). Transmission electron microscopy, Nanosight NS300 and WB analysis indicated that the extracted samples were plasma exosomes. The relative expressions of miR-210, miR-21 and miR-4639 between the 2 groups had statistical significance (t=4.13, 3.38 and 2.33, P all<0.05). The area under the ROC curve (AUC) for the prediction of CAN by miR-210 was 0.854(95%CI: 0.730-0.979, P<0.05). When the cut-off value was 1.320, the sensitivity was 66.7%, and the specificity was 93.8%. The AUC for the prediction of CAN by miR-21 was 0.774(95%CI: 0.618-0.931, P<0.05). When the cut-off value was 1.243, the sensitivity was 55.6%, and the specificity was 93.8%. The AUC for the prediction of CAN by miR-4639 was 0.670(95%CI: 0.482-0.859, P<0.05). When the cut-off value was 0.936, the sensitivity was 66.7%, and the specificity was 75.0%. A joint diagnostic model based on 3 indicators was constructed, and the regression equation was z=5.293×[miR-210]+ 5.046×[miR-21]+ 0.433×[miR-4639] -13.373. The joint prediction value p=e^z/(1+ e^z). The AUC of combined miRNAs to predict the complications of CAN after renal transplantation was 0.938 (95%CI: 0.860-1.015, P<0.05). When the cut-off value was 0.587, the sensitivity was 83.3% and specificity was 93.8%. Moreover, 83.3% (15/18) of the individuals in the CAN group were diagnosed as positive by the joint prediction model, while 93.8% (15/16) of the individuals in the control group were diagnosed as negative by the joint prediction model when the cutoff value 0.587 was applied. The results indicate that the joint prediction model has good diagnostic value.

Joint diagnostic model of plasma exosomal miR-210, miR-21 and miR-4639 may become a biomarker for early noninvasive diagnosis of CAN after renal transplantation.