Candice Chu

Background Most proteinuric dogs with naturally occurring chronic kidney disease have amyloidosis (AMYL), glomerulosclerosis (GS), or immune complex‐mediated glomerulonephritis (ICGN), each with different treatment and prognosis. A noninvasive and disease‐specific biomarker is lacking. Hypothesis We hypothesized that the expression pattern of biofluid microRNA (miRNAs and miRs) would correlate with disease progression and categorization. Animals Archived serum and urine samples from 18 dogs with glomerular disease and 6 clinically healthy dogs; archived urine samples from 49 dogs with glomerular disease and 13 clinically healthy dogs. Methods Retrospective study. Archived biofluid samples from adult dogs with biopsy‐confirmed glomerular disease submitted to the International Veterinary Renal Pathology Service between 2008 and 2016 were selected. Serum and urinary miRNAs were isolated and profiled using RNA sequencing. Urinary miR‐126, miR‐21, miR‐182, and miR‐486 were quantified using quantitative reverse transcription PCR. Results When comparing more advanced disease with earlier disease, no serum miRNAs were differentially expressed, but urinary miR‐21 and miR‐182 were 1.63 (95% CI: .86‐3.1) and 1.45 (95% CI: .82‐2.6) times higher in azotemic dogs, respectively (adjusted P < .05) and weakly correlated with tubulointerstitial fibrosis (miR‐21: r = .32, P = .03; miR‐182: r = .28, P = .05). Expression of urinary miR‐126 was 10.5 (95% CI: 4.1‐26.7), 28.9 (95% CI: 10.5‐79.8), and 126.2 (95% CI: 44.7‐356.3) times higher in dogs with ICGN compared with dogs with GS, AMYL, and healthy controls, respectively ( P < .001). Conclusions and Clinical Importance The miR‐126 could help identify dogs that might benefit from immunosuppressive therapy in the absence of a biopsy. MiR‐21 and miR‐182 are potential markers of disease severity and fibrosis.