Lab-created heart valves that grow with the recipient could spare kids born with heart defects from the repeated valve-replacement surgeries they now endure.
University of Minnesota researchers found that lab-created valves implanted in young lambs for a year were capable of growing within the recipient.
"This is a huge step forward in pediatric heart research," said senior researcher Robert Tranquillo, a professor of biomedical and chemical engineering and materials science. "This is the first demonstration that a valve implanted into a large animal model, in our case a lamb, can grow with the animal into adulthood."
Right now, the only accepted options for kids with heart defects are valves made from chemically treated animal tissues. But these don't grow with the child and often become dysfunctional because of calcium buildup, requiring repeated replacement.
The cultured valves tested in this study had less calcium buildup and they grew with the recipient.
Researchers will need to confirm that this science translates to humans. Results of animal studies aren't always the same in people.
But, if these are, the science could prevent repeated valve replacement surgeries in thousands of babies born each year with heart defects. They currently endure five or more surgeries before they can receive a mechanical valve in adulthood.
Researchers said the tested valves can also be stored for six months, providing surgeons with easier access to transplant tissue.
For the project, researchers used a specialized tissue-engineering technique they previously developed to generate vessel-like tubes in the lab from sheep skin cells.
To develop the valves, they first combined the cells with a gelatin-like material and then provided nutrients necessary for cell growth.
When tissue-like tubes were formed, special detergents washed away the sheep cells so they wouldn't cause an immune reaction when implanted.
Researchers precisely sewed three tubes together into a closed ring, then trimmed them slightly to create leaflets that replicate a structure similar to a natural heart valve. The structure worked like a valve and also grew.
This second generation of tri-tube valves were implanted into the pulmonary artery of three lambs. After 52 weeks, the valves had regenerated and the diameter increased to a normal valve size. On ultrasound images, researchers also saw a 17% to 34% increase in length of the leaflets.
The next step will be implanting the valve directly into the right ventricle of the heart to mimic the most common surgical repair. Then, researchers will seek U.S. Food and Drug Administration approval to launch human clinical trials.
"If we can get these valves approved someday for children, it would have such a big impact on the children who suffer from heart defects and their families who have to deal with the immense stress of multiple surgeries," Tranquillo said. "We could potentially reduce the number of surgeries these children would have to endure from five to one. That's the dream."
The study was published March 17 in the journal Science Translational Medicine.
The valve-making procedure has been patented and licensed to the University of Minnesota startup company Vascudyne Inc. The research was funded by the National Institutes of Health.
The U.S. Centers for Disease Control and Prevention has more information on congenital heart defects.
SOURCE: University of Minnesota Twin Cities, news release, March 17, 2021