Scientist are studying mitral valve disease - the dog version. It’s not too different from the human version, and any discoveries made could improve treatment options for humans and canines alike.
Myxomatous mitral valve disease (MMVD) is the most commonly acquired heart disease for dogs. It leads to congestive heart failure, and a dog’s risk of developing it only increases as the dog grows older. After the disease reaches congestive heart failure, the dog usually doesn’t live too much longer.
From the Cummings School of Veterinary Medicine at Tufts University, researchers conducted a study of 47 healthy and diseased dogs. They looked for changes in gene expression from microRNA (miRNA) found in small cavities, called extracellular vesicles or exosomes, that are secreted by cells and float along in the blood stream alongside blood cells and plasma. Exosomes and the miRNA found inside of them is a new field of study.
They began by comparing dogs with heart disease to healthy dogs, including a study of the impact of age. The dogs were given a physical examination, echocardiography was conducted, and blood samples were taken. Researchers looked at changes in miRNA expression in exosomes, comparing it to miRNA expression in plasma. Depending on whether the dogs were healthy, had asymptomatic MMVD, or had MMVD and congestive heart failure, different types of miRNAs were associated with different disease states.
"These results suggest that [exosome] miRNA expression changes may be more specific to disease states than total plasma miRNA," explained corresponding author Andy Hoffman, D.V.M., Ph.D. "These plasma Ex-miRNAs show great promise as biomarkers for MMVD disease monitoring and may also help us understand the pathophysiology of the disease, and subsequently devise more specific molecular therapies that can halt disease progression."
This discovery is the first of its kind in veterinary medicine.
What does this discovery mean? Expression of miRNA in circulating exosomes is a genomic biomarker that researchers can apply to diagnostic standards, disease maintenance, and potentially even treatments for canine MMVD and a similar disease in humans called mitral valve prolapse (MVP).
MVP, the “human version” of a dog’s MMVD, is characterized by destruction of collagen and elastin fibers in the heart’s valves. The condition leads to mitral regurgitation and, eventually, congestive heart failure. Surgery to repair mitral regurgitation is possible, but it’s only effective before the condition has progressed to congestive heart failure.
"There are currently no medical treatments available to delay the progression of these valvular diseases," explained first author Vicky Yang, D.V.M., Ph.D. "While these new molecular signatures in exosomes require further study, the findings could open doors to novel molecular targets to slow or halt the progression of mitral valve disease to heart failure."
This study was published in the Journal of Extracellular Vesicles.
Source: Tufts University