Congested Heart Failure in Small Breeds Dogs

Abstract

Mitral valve disease, commonly known as MVD, is the most common heart disease in dogs, accounting for nearly 75% of all dogs affected. The characteristic of this predominant disease includes collagen degradation, elastic fiber fragmentation and proteoglycan accumulation, leading to deterioration of the mitral valve and ultimately, congestive heart failure (CHF). Treatment to reverse or even delay the damaging effects of MVD has not yet been discovered due to a lack of awareness of the underlying processes. Furthermore, this disease in dogs has many similarities with the human MVD and may potentially serve as a translational model for studying MVD further. Therefore, it is imperative to identify the causes and underlying mechanisms associated with canine MVD in order to treat these patients more efficiently at the earliest detectable stage. MicroRNAs (miRNAs) are small, 21‐25 nucleotides in length, non‐coding RNAs that can down‐regulate the expression of protein coding genes by binding to the 3’UTR sites in their messenger RNAs (mRNA), causing either degradation or gene silencing. Prior studies have shown that one miRNA may regulate multiple mRNAs, subsequently effecting the downstream levels of gene expression. Furthermore, if miRNAs prove to be a useful biomarker of heart disease, not only may they serve as detectors of early disease onset, but they may also be useful as therapeutic agents. Given this recent data, we propose to test the hypothesis that circulating miRNAs may be useful biomarkers for detection of CHF, secondary to MVD. Liquid biopsies (blood samples) were collected in EDTA tubes from 7 healthy dogs with no prior history of heart disease and 7 dogs being treated for CHF secondary to MVD. Total serum RNA was isolated using miRNeasy Serum/Plasma Kit (Qiagen). Isolated RNA was then reverse transcribed using miScript II RT Kit (Qiagen) and lastly, miRNA was quantified using miScript SYBR Green PCR Kit, along with miScript miRNA PCR Arrays (Qiagen).