ARLINGTON, Va., March 18, 2004 -- Researchers have made progress in artificially growing blood vessels, with a new report that a man-made vasculature is still going strong a year after being implanted in test animals.

"Most artificially grown vessels die quickly," said Rakesh Jain, Ph.D., of the Massachusetts General Hospital and Harvard University, "but these have survived successfully for a year, which is about half a lifetime for mice."

Jain and his colleagues, who reported their results in a recent issue of the journal Nature, used a technique that mimics natural development and avoids genetic manipulation, which carries the risk of complications.

Before man-made tissues and organs can be used to treat disease they will need an accompanying blood supply, making research like that of Jain's closely watched.

Jain's group started with endothelial cells that line the inner walls of blood vessels. These came from the veins of umbilical cords. The researchers combined these with cells that form the supporting outer layers of vessels and put the two in a collagen gel to grow for about 24 hours.

These gels were implanted in mice along with a control group of gels that contained only endothelial cells.

The combined cell culture grew rapidly for about two weeks and then stabilized after forming long, branching tubes that connected with the mice vasculature and began carrying blood. The second set of gels grew up to a point and then withered.

"The combined implants formed beautiful networks that survived and grew," Jain said. "As they matured, they appeared and functioned very much like normal vasculature tissue."

The study represents an encouraging step toward providing man-made organs and tissues with the blood supply they need to survive and be strong. It also lays the groundwork for future studies on blood vessel growth and maturation.

The research group includes Naoto Koike, M.D., Ph.D.; Dai Fukumura, M.D., Ph.D.; Oliver Gralla, M.D.; and Patrick Au; all of Mass General and Harvard, and Jeffrey Schechner, M.D., of Yale University School of Medicine.

Jain received a Whitaker Foundation Special Opportunity Award in 1996 entitled, Bioengineering in Oncology: An Interdisciplinary Postgraduate Education and Research Program.