The use of plasma microRNAs (miRs) as diagnostic and prognostic biomarkers of chronic kidney disease (CKD)
MicroRNAs (miRs) have the potential to be employed as diagnostic and prognostic biomarkers of chronic kidney disease (CKD) and are functionally important in disease pathogenesis. To identify novel miR biomarkers we performed small RNA-sequencing (sRNA-Seq) to detect miRs that were quantitatively altered in the circulation of individuals with type 2 diabetes (T2D) with CKD compared to those with normal kidney function. MiR-190a-5p abundance was significantly lower in the circulation of T2D patients with reduced kidney function compared to those with normal kidney function. To validate if the loss of circulating miR-190a-5p was associated with reduced kidney function we measured miR-190a-5p in an unselected cohort of CKD patients and determined if dysregulated miR-190a-5p could predict kidney outcomes. In individuals with no or moderate albuminuria (<300mg/mmol), serum miR-190a-5p levels predicted CKD progression (reaching end-stage kidney disease or >30% reduction from baseline eGFR, independent of age, sex, baseline eGFR, urinary albumin excretion, or blood pressure (adjusted HR 0.80, 95% CI: 0.66-0.96, p=0.015). To identify the kidney source of miR-190a-5p we utilised transcriptomic data from mouse models of kidney injury and single nuclear (sn) RNA-Seq from human kidney, finding that miR-190a-5p is enriched in the proximal tubule (PT) but down-regulated following injury. Bioinformatic analysis highlighted ADAM10as a potential miR-190a-5p target and we validated this in human PT cell line. Our analyses suggest that miR-190a-5p is a biomarker of tubular cell health and low circulating levels may predict CKD progression in patients with low or moderate proteinuria independent of existing risk factors. Overall design: This study applied a miRNA next generation sequencing (NGS) approach to measure DKD-related differential expression of plasma miRNAs. The discovery cohort comprised individuals with type 2 diabetic kidney disease (T2DKD, n = 9), age and gender matched patients with type 2 diabetes mellitus and normal renal function (T2DNRF, n = 13) and non-diabetic with normal renal function (NDNRF, n = 11). Libraries were successfully prepared from the low yields of plasma-derived RNA and sequenced to reveal global miRNA expression.