McGowan Institute faculty member, Michael Sacks, PhD, William Kepler Whiteford Professor, University of Pittsburgh Department of Bioengineering, is working with researchers at Children's Hospital of Boston to grow tissue-engineered heart valves in the lab. The team is using blood cells from sheep to grow the heart valves around polymer scaffolding and then implant them, where they have worked successfully for up to 20 weeks.
“The ultimate goal is to create heart valves for children using their own tissue, a technique that is designed to allow the valves to grow along with the children's bodies,” said Dr. Sacks.
That would overcome a major problem children with heart valve problems now face. Many of them get valves from human donors, but those transplanted valves don't grow with the children, who then have to undergo anywhere from two to five valve replacement surgeries before they are adults. The other advantage of lab-grown valves would be to cut down on the calcium buildup that causes current prosthetic tissue valves to wear out. Calcium accumulation is a bigger problem in children than adults, because their bodies are still actively metabolizing it for their growing bones. In addition, the implanted tissue valves children now get, whether from humans or animals, are cleansed in a substance called glutaraldehyde to prevent them from causing an immune reaction. But glutaraldehyde also becomes a magnet for calcium molecules, researchers say.
Right now, Dr. Sacks and his team are using the sheep's blood to grow a cellular matrix along polymer scaffolding. After the engineered valve is put into the sheep, their own tissues start to replace the polymer. “Tests so far have shown that this polymer replacement process is occurring in sheep after five months, when they are almost adults,” he said, “but has not yet proven whether the valves are growing at the same pace as the sheep's hearts.”
Although the results are promising and the future for tissue-engineered heart valves is optimistic, scientists caution that people must be patient. “It may take another 10 to 30 years before these valves are widely available because of the need for further research and then clearing steep regulatory hurdles,” Dr. Sacks said.
Illustration: McGowan Institute for Regenerative Medicine.
Pittsburgh Post-Gazette (03/12/08)