While training in an intensive-care unit during medical school, Laura Niklason got a graphic view of a persistent problem. "The surgeons spent a lot of time digging around in the patients' legs or arms looking for veins to replace main arteries," she says. "I thought, there's got to be a better way."
According to the most recent National Hospital Discharge Survey, doctors in the U.S. performed 408,000 coronary artery bypass procedures in 2007, all of which required vascular grafts. And more than half of the 320,000 chronic dialysis patients need blood vessels transplanted into their arms. While tissue engineers can grow compatible vessels from a patient's own cells, the wait time can be more than six months. Niklason, along with colleagues Juliana Blum and Shannon Dahl, decided the solution should be at a surgeon's fingertips: Their company, Humacyte, was the first to make blood vessels that can be stored for future use.
To grow these, the researchers seed human smooth-muscle cells onto tubular scaffolds made from a biodegradable polymer. The cells produce collagen and other molecules that form a matrix as the scaffold disintegrates. Using detergent, the researchers scrub away the muscle cells, leaving nonimmunogenic vessels behind—meaning they won't be rejected by an unrelated patient's body.
"Think of [the vessel wall] as a sponge," Dahl says. "It has holes that are filled with cells. Wash them away and you're left with something you can still hold on to."
The vessels retained their strength and elasticity after a year of refrigerated storage in a saline solution, according to a study published in February's Science Translational Medicine. They were then grafted into animals, where, after six months, they showed no signs of fibrosis or thickening of the vessel walls.
"Since vascular disease is really the No. 1 cause of morbidity and mortality in the Western world, a way to replace diseased arteries will have huge impact, I hope, over the long term," Niklason says, "particularly with the problem of obesity."
Humacyte hopes to begin human trials overseas in 2012; meanwhile, the team is already thinking beyond blood vessels. The same technique could be used to grow other simple tissues, such as ligaments and cartilage, that are structurally important. Eventually, they think, labs will grow organs with complex functions—making more transplants off-the-shelf.