| WASHINGTON, Aug 1 (Reuters) - Corporate
researchers said on Tuesday they had
developed an artificial heart valve that they think will grow and change with the patient -- even a child. The team at Atlanta-based Cryolife Inc. (CRY.N) said their valve is made of pig collagen, but becomes virtually the patient's own as their cells grow in and around it. The company has applied for approval from the U.S. Food and Drug Administration (FDA) to test the valve in people. An estimated 78,000 people get replacement heart valves in the United States each year, according to the American Heart Association. Valves, which control the flow of blood through the heart, are sometimes damaged by infections. The SynerGraft valve starts out as a normal pig heart valve. Chemicals are used to strip all the cells away -- cells that could cause rejection, or that could carry disease -- and the collagen structure that remains is implanted into the patient's heart. Tests in sheep show that the patient's cells then grow in and on the collagen structure, and start building new collagen. ``It becomes the patient's own valve,'' Roy Vogeltanz, vice president for corporate communications for Cryolife, said in a telephone interview. Cryolife's Dr. Steven Goldstein said the patient's cells allow the valve to withstand the wear and tear of daily use. ``It's remodeling itself,'' he said. Goldstein said pig valves are now routinely used in human patients, but they wear out, become calcified or are rejected by the immune system. They then must be replaced, which requires a major operation. The company hopes its product will do none of these things, and they hope to use the technology for other body parts, such as knees. Goldstein said the valves seemed to have grown along with the hearts of young sheep that they were tested in. ``The valves remained competent. They weren't leaking. Wesuppose the valves actually increased in size,'' he said. And Goldstein said the valves were working well in six human patients in Australia. Pigs are known to carry viruses known as porcine endogenous retroviruses. These viruses are incorporated into the genomes -- the genetic material -- of the pigs, cannot be removed, and can infect human tissue. Some scientists worry that transplants from pigs will cause infections in people, but Goldstein said the company had found no evidence that pig collagen, which is not made up of cells and which does not carry genes, carried the viruses. ``We actually get rid of the nucleic acid,'' he said, referring to the basic material of genes. He said the company was also testing its process with human heart valves, but said human tissue is always limited because so few people arrange to donate their organs after death. ``That prompted us to look at the porcine xenograft because we know that is in unlimited supply,'' Goldstein said. Many other companies make heart valves. Also on Tuesday, Medtronic (MDT.N) said it had won FDA approval for its Mosaic heart valve, another pig valve product.
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