Hypoplastic left heart syndrome (HLHS), in which the heart’s main pumping chamber—the left ventricle—does not completely develop prior to birth, is one of the most devastating congenital cardiac conditions, with an average five-year survival of only 50 to 60 percent. The standard of care is a three-stage surgery that enables the remaining right ventricle to pump blood to the entire body and eventual heart transplantation. To delay that need for a new heart and improve survival, pediatric cardiac surgeons at Johns Hopkins Children’s Center are employing a novel stem cell treatment to strengthen the right ventricle in patients with HLHS.

“With existing treatments we can close a hole and fix a valve, change the blood flow and the anatomy, but not the heart muscle,” pediatric cardiac surgeon Luca Vricella says. “We can fix the plumbing but not the sink.”

In this new approach, first performed at Johns Hopkins in September 2017, a team led by pediatric cardiac surgeon Narutoshi Hibino injected allogeneic mesenchymal stem cells (MSC) directly into the heart of a 4 1/2-month-old girl. A follow-up MRI every six months will help determine the patient’s cardiac function and response to the therapy. In adult patients, MSCs in the heart have been shown to reduce scar tissue and inflammation and to trigger the growth of new small vessels and muscle cells in the heart.

“We don’t understand the exact mechanism, but stem cells contain proteins that stimulate the heart to recover and regenerate,” Hibino says.

The stem cell heart procedure at Johns Hopkins Children’s Center was part of a phase I safety and efficacy trial of 10 patients, and a collaboration with the University of Maryland Medical Center, the University of Miami and Emory University.