Scientists at the Massachusetts Institute of Technology have produced for the first time artificial blood vessels from cells grown in the laboratory.

The living blood vessels hold great promise for replacing small blood vessels that have been damaged by diabetes, blood vessel diseases or physical injury, the scientists said.

As many as 300,000 Americans each year could benefit from small blood vessel replacements. But the procedure probably won't be available for at least five years, after tests in animals and humans.

The development of a living replacement vessel could provide an important new tool for surgeons treating limb damage. Dacron tubes are currently used to replace large blood vessels that have been damaged, but Dacron does not work for vessels that are smaller than about a quarter of an inch in diameter, such as those found in the limbs.

MIT's Crispin Weinberg and Eugene Bell report in today's issue of Science magazine that they developed the living blood vessels by using techniques similar to those they had previously used to prepare artificial skin.

The key to both developments was their discovery that certain cells can cause a gel of collagen -- a fibrous tissue found in bone, cartilage and connective tissue -- to contract by a factor of 10 to 20, forming a tough, tissue-like lattice.

In their earlier work, that lattice served as a base on which were scattered a small number of skin cells. The cells then were allowed to proliferate in an incubator until they covered the entire surface. Skin prepared in that manner can be used to cover wounds.

The manufacture of the artificial blood vessels proceeds in a similar manner, Weinberg said.

The scientists used muscle cells from the blood vessels of cows to contract the collagen gel. The cells and the collagen are cast around a thin cylinder called a mandrel.

After the collagen has contracted, a sleeve of Dacron polyester mesh is slipped over the lattice and an outer layer of collagen and a different type of cells called fibroblasts are cast over it.

The tube of cells then is removed from the mandrel, and endothelial cells from the interior of cow blood vessels are scattered over the interior. They are allowed to proliferate.