Human Genome Sciences Inc. of Rockville said a gene it discovered has entered human testing as a potential way to make new blood vessels grow in ailing hearts.

Early tests of the treatment, known as vascular endothelial growth factor-2, have begun at several medical centers around the country, the company said yesterday in a statement. The tests are being sponsored by Vascular Genetics Inc., a spinoff in which Human Genome Sciences owns a 30 percent stake.

Doctors have no idea how well the treatment will work in people, and it could pose unknown risks. But in animal tests, VEGF-2 has shown a striking ability to heal ailing tissue by spurring the formation of new blood vessels. Tests are already underway in people with oxygen-starved limbs, though no definitive results have been reported.

The new research expands scientists' goal of finding treatments for heart disease, the leading cause of death in the industrial world. Hearts grow sick and fail when their blood vessels become clogged, starving tissue of oxygen and nutrients. The idea behind the research is to get around this problem by spurring the heart to grow brand-new blood vessels, something it won't ordinarily do.

HGS stock closed yesterday at $45, up 75 cents.

The VEGF-2 gene, believed to be particularly active in fetuses and in wound healing, was discovered in Rockville as part of Human Genome Sciences' broad program to discover genes of potential medical importance. The company says it has already discovered the large majority of human genes, though it is still figuring out what function most of them serve.

Genentech Inc. of South San Francisco, Calif., the world's second-largest biotechnology company, recently failed with a heart-disease strategy similar to the one pursued by Vascular Genetics. It used a similar vascular growth factor. But the treatment and the methods are different enough in the new research that many scientists continue to hold out hope it will work.

In the tests, doctors are injecting the VEGF-2 gene into heart tissue by one of two methods. In the first, a catheter inserted into a groin incision is threaded through the body to the heart, and a small needle at the tip injects the treatment. In the second method, doctors inject the treatment directly into the heart after making an incision in the chest.