Association of circulating microRNA‐122 and microRNA‐29a with stage of fibrosis and progression of chronic hepatitis in Labrador Retrievers

BACKGROUND: Chronic hepatitis (CH) in dogs is common and has the tendency to progress to liver cirrhosis (LC). Circulating microRNAs might have the potential as markers for disease progression. OBJECTIVES: To investigate whether concentration of specific microRNAs in serum correlate with the stage and grade of CH in Labrador Retrievers. ANIMALS: Twenty‐two Labrador Retrievers with histological CH (n = 8), LC (n = 7), and normal liver (NL, n = 7). METHODS: In this retrospective study, serum concentrations of miR‐122, miR‐29a, miR‐133a, miR‐181b, and miR‐17‐5p were measured by quantitative real‐time PCR and evaluated using univariate linear regression in dogs. A multivariate model was fit including the grade of hepatitis and the stage of fibrosis. RESULTS: Of the 5 microRNAs, only circulating miR‐122 and miR‐29a were significantly associated with the grade of hepatitis and the stage of fibrosis. A positive correlation was identified between the grade of hepatitis with miR‐122 (r(s) = 0.79, P < .001) and miR‐29a (r(s) = 0.78, P < .001). Both miR‐122 (r(s) = 0.81, P < .001) and miR‐29a (r(s) = 0.67, P < .001) showed a significant positive correlation with the stage of fibrosis. MiR‐122 concentrations were significantly higher in the CH (P < .01) and LC groups (P < .001) compared to the NL group. MiR‐29a concentrations were significantly higher in the CH (P < .001) and LC (P < .001) groups compared to the NL group. CONCLUSIONS AND CLINICAL IMPORTANCE: Circulating miR‐122 and miR‐29a concentrations might be useful for monitoring the response to treatment and progression of canine CH.