February is American Heart Month, a time for focusing on cardiovascular health. Heart disease remains the No. 1 killer of American men and women. But humans aren’t the only species affected; dogs also develop cardiovascular problems.

With support from a private donation, School of Veterinary Medicine researchers are working to find novel drugs to prevent or reverse the leading cause of canine heart disease: mitral valve disease (MVD). Their work could not only help extend the lives of pets, but may also lead to a new strategy for treating valve disease in humans.

MVD affects as many as 70 percent of dogs over the age of 10, with smaller breeds more likely to be affected, notably Cavalier King Charles spaniels, but also toy poodles, Chihuahuas, and miniature schnauzers. In MVD, the mitral heart valve degenerates, causing a leak in blood flow and preventing the heart from pumping enough oxygenated blood to the body. When the condition is severe, it can cause congestive heart failure.

Humans can develop the same disease, which is the No. 1 reason for heart valve replacement or repair surgery in the United States.

Mark Oyama, a professor in Penn Vet’s Department of Clinical Studies, has spent years studying the underlying mechanisms responsible for the disease. Recent research by Oyama and colleagues has pointed to a role for serotonin in contributing to the development of MVD.

“Serotonin is well-known for being a neurotransmitter that affects mood, but it is also involved in growth and regulation of other parts of the body,” Oyama says. “We have good evidence indicating that components of serotonin pathways are activated in degenerating heart valves.”

Oyama and other researchers have also found that dogs with a high risk of developing MVD have unusually high levels of serotonin in their blood. In addition, people taking serotonin-containing drugs have an increased risk of heart valve problems. All of these lines of evidence suggest that blocking serotonin in the heart valves could be an effective strategy at preventing or reversing MVD.

A recent $450,000 gift from Bruce Wiltsie and William Davenport to create the Barth Memorial Fund—named for their beloved dog who succumbed to MVD—will support Penn Vet scientists’ search for a serotonin-blocking drug.

Together with colleagues from the Children’s Hospital of Philadelphia, Oyama’s team will screen candidate compounds to see which effectively block serotonin in the heart. Promising drugs will eventually be evaluated in dogs—and, if found to be safe and effective, in people.

“If we’re able to develop a drug that works in dogs, it will have clear and important implications for human health,” Oyama says.