Development and nation-wide validation of kidney graft injury markers using urinary exosomes and microvesicles (complete English translation of the Japanese version)

Abstract

Abstract Background Non-invasive, prompt and proper detection tools for kidney graft injuries (KGIs) are awaited to ensure the graft longevity. We screened diagnostic biomarkers for KGIs following kidney transplantation using extracellular vesicles (EVs; exosomes and microvesicles) from patients’ urine samples. Methods One hundred and twenty-seven kidney recipients at 11 Japanese institutes were enrolled in this study; urine samples were obtained prior to protocol/episode biopsies. EVs were isolated from urine samples, and EV RNA markers were assayed using quantitative RT-PCR. Diagnostic performance of EV RNA markers and diagnostic formulas comprising those were evaluated by comparison with the corresponding pathological diagnoses. Results EV CXCL9, CXCL10, and UMOD were elevated in T-cell-mediated rejection samples compared with other KGI samples, while SPNS2 was elevated in chronic antibody-mediated rejection (cABMR) samples. A diagnostic formula developed through Sparse Logistic Regression analysis using EV RNA markers allowed us to accurately (area under the receiver operator characteristic curve (AUC) 0.875) distinguish cABMR from other KGI samples. EV B4GALT1 and SPNS2 were also elevated in cABMR, and a diagnostic formula using these markers was able to distinguish between cABMR and chronic calcineurin toxicity accurately (AUC 0.886). In interstitial fibrosis and tubular atrophy (IFTA) urine samples and those with high Banff chronicity score sums (BChS), POTEM levels may reflect disease severity, and diagnostic formulas using POTEM detected IFTA (AUC 0.830) and high BChS (AUC 0.850). Conclusions KGIs could be diagnosed with urinary EV mRNA analysis with relatively high accuracy.