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Infants and children receiving artificial heart valve replacements face several repeat operations as they grow, since the clinically approved replacements don't grow along with them. Virna Sales, MD, Bret Mettler, MD, and John Mayer, MD, in Children's Hospital Boston's Department of Cardiac Surgery, have developed a solution: living, growing valves created through tissue engineering.
In a special issue of Circulation
published September 11, they describe making pulmonary valve leaflet
replacements in the laboratory using endothelial progenitor cells (precursors of the cells that line blood vessel walls)
isolated from the blood of laboratory animals. They seeded the cells onto tiny, valve-shaped biodegradable molds
pre-coated with proteins found in the supporting extracellular matrix and were able to make sturdy yet pliable pulmonary valve leaflets, composed of both
endothelial- and smooth-muscle-like cells. Dr. Sales is now refining the lab-grown valves by exposing them to mechanical stress in a bioreactor and developingmaterials and techniques to mimic natural valve formation in the embryo. Her next step will be to implant the living valves into animals.
Doctors Sales and Mettler have already implanted tiny tissue-engineered patches into the pulmonary arteries of sheep, with the ultimate goal of
reconstructing the right ventricular outflow tract in patients with congenital heart disease. The patches grew over time and functioned well for up to six weeks.
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