Expression Profile of Circulating MicroRNAs in Dogs With Cardiac Hypertrophy: A Pilot Study

Abstract

This study aimed to identify the expression profile of circulating microRNAs in dogs with eccentric or concentric cardiac hypertrophy. A total of 291 microRNAs in serum samples of five dogs with myxomatous mitral valve degeneration (MMVD) and five dogs with pulmonic stenosis (PS) were compared with those of five healthy dogs using microarray analysis. Results of microarray analysis revealed up-regulation of cfa-miR-130b [fold change (FC) = 2.13, p = 0.014), down-regulation of cfa-miR-375 (FC = 1.51, p = 0.014), cfa-miR-425 (FC = 2.56, p = 0.045), cfa-miR-30d (FC = 3.02, p = 0.047), cfa-miR-151 (FC = 1.89, p = 0.023), cfa-miR-19b (FC = 3.01, p = 0.008), and cfa-let-7g (FC = 2.53, p = 0.015) in MMVD group which showed eccentric cardiac hypertrophy, up-regulation of cfa-miR-346 (FC = 2.74, p = 0.032), down-regulation of cfa-miR-505 (FC = 1.56, p = 0.016) in PS group which showed concentric cardiac hypertrophy, and down-regulation of cfa-miR-30c (FC = 3.45, p = 0.013 in MMVD group; FC = 3.31, p = 0.014 in PS group) and cfa-let-7b (FC = 11.42, p = 0.049 in MMVD group; FC = 5.88, p = 0.01 in PS group) in both MMVD and PS groups. In addition, the unsupervised hierarchical clustering of differentially expressed microRNAs in each group resulted in complete separation of healthy dogs from dogs with heart diseases. Therefore, eleven microRNAs among 291 microRNAs were identified as differentially expressed circulating microRNAs related to MMVD or PS in dogs. This pilot study demonstrates that the microRNAs identified in this study could be possible candidates for novel biomarker or therapeutic target related to cardiac hypertrophy in dogs.

Keywords: cardiac hypertrophy; dog; microRNA; myxomatous mitral valve degeneration; novel biomarker; pulmonic stenosis; serum; therapeutic target.

Figure 1

Representative echocardiographic images of dogs included in (A) healthy, (B) MMVD, and (C) PS groups. Upper images are right parasternal 4-chamber view, and lower images are right parasternal short-axis view. All images were taken during the diastole. (B) Note the enlargement of chambers (LV and LA), eccentric hypertrophy of ventricular walls (white asterisk), and thickened mitral valve (arrowhead) in a dog with MMVD. (C) Also, note the concentric hypertrophy of ventricular walls (yellow asterisk) in a dog with PS. LA, left atrium; LV, left ventricle; MMVD, myxomatous mitral valve degeneration; PS, pulmonic stenosis; RA, right atrium; RV, right ventricle.

Figure 2

Volcano plots of circulating miRNA in dogs with (A) MMVD or (B) PS, compared with healthy dogs. The volcano plot shows the fold change and p-value between the dogs with heart diseases and healthy dogs for 291 miRNAs. The vertical lines correspond to a 1.5-fold differences, and the horizontal line displayed a p-value of 0.05. Therefore, the blue and red points in the plot represent the miRNAs with statistically significant differential expression in dogs with MMVD or PS (A or B, respectively) compared with healthy dogs. miRNA, microRNA; MMVD, myxomatous mitral valve degeneration; PS, pulmonic stenosis.

Figure 3

Heat map of significantly altered miRNA microarray expression data from serum samples of dogs with (A) MMVD and (B) PS compared with healthy dogs. Sample species are shown at the top and the miRNA species are shown on the right. Unsupervised hierarchical clustering of expression levels of nine and four (A and B, respectively) differentially expressed microRNAs using the Euclidian distance measure. The hierarchical clustering completely separated healthy dogs from dogs with heart diseases, showing distinct microRNA patterns among sample types. Red and green colors indicate relatively high and low expressions of microRNA, respectively. miRNA, microRNA; MMVD, myxomatous mitral valve degeneration; PS, pulmonic stenosis.