WASHINGTON (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. 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 US 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 would be implanted into the patient's heart.

Tests in sheep show that the recipient'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 explained that the patient's own cells would 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 that the technology will be used for other body parts, such as knees.

Goldstein said the valves seemed to have grown along with the hearts of young sheep in which they were tested. ``The valves remained competent. They weren't leaking. We suppose 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 genome -- the genetic material -- of the pigs, cannot be eliminated, and can infect human tissue.

Some scientists worry that transplants from pigs will cause infections in people, but Goldstein said the company has 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 valve

(From Yahoo)