Muscle cells have been used successfully to restore life-sustaining rhythms to ailing hearts, a first step toward developing natural pacemakers. Placed in a tiny raft of collagen implanted into the hearts of rats, these cells survived for the entire lifespan of the animals.
“Our experiments provide proof that engineered tissue can function as an electric conduit in the heart and, ultimately, may offer a substitute for artificial (electronic) devices,” says Douglas Cowan. He is an assistant professor of anesthesiology at Harvard Medical School who led a team of biologists, cardiologists, and surgeons at Children’s Hospital Boston to create a biological substitute for the tissue that keeps the heart beating regularly.
When birth defects, heart disease, surgery, or other causes block that vital function, people can suffer heart failure or other life-threatening disruptions of rhythm. Standard treatment is to implant an electronic device to provide a strong, regular beat. Cowan estimates that hundreds of thousands of these pacemakers are installed each year. But, often, this isn’t a lifetime fix. Patients must undergo re-operations every 4-5 years to replace internal batteries and wires. And, recently, the media has carried reports of thousands of pacemakers recalled because they are defective.
The problem is particularly heart breaking for children. “Over the course of their lives, many more battery-replacement operations are required for a 2-year-old than, say, a 55-year-old who gets a pacemaker,” Cowan points out. “Add to this the risk of infection, perforation of the small heart by the wires, and other complications. Thirty years ago, many infants with disrupted heart rhythms did not survive. But new surgical techniques now make it possible to keep them alive.”
To fill what they see as an accelerating need, Cowan and his team decided to build a biological replacement for the node of tissue that helps synchronize the beating of a heart.