Blood vessels for lab-grown tissues.

• Position: Biomedical Breakthroughs

One of the major roadblocks on the path to growing transplantable tissue in the lab has been broken by researchers from Texas' Rice University, Houston, and Baylor College of Medicine, Waco, who have found a way to grow the blood vessels and capillaries needed to keep tissues alive. "The inability to grow blood-vessel networks--or vasculature--in lab-grown tissues is the leading problem in regenerative medicine today," notes Jennifer Wast, department chair and professor of bioengineering at Rice. "If you don't have blood supply, you cannot make a tissue structure that is thicker than a couple of hundred microns"

As its base material, a team of researchers led by West and molecular physiologist Mary Dickinson of Baylor chose polyethylene glycol (PEG), a nontoxic plastic that is used widely in medical devices and food. Building on 10 years of research in West's lab, the scientists modified PEG to mimic the body's extracellular matrix--the network of proteins and polysaccharides that make up a substantial portion of most tissues.

The researchers combined the modified PEG with two types of...