Half-Breed Organ

Liver-transplant operations are almost routine these days. Finding suitable donors remains the hard part. Each year thousands of patients suffering from cirrhosis, hepatitis and other severe liver ailments die while on waiting lists. Artificial livers aren't likely to fill the gap, either. The liver is almost as complex as the brain: it handles some 400 physiological functions, from detoxifying the blood to turning food into the nutrients and chemicals our cells need to function and survive.

Recently, researchers have begun to take a new tack. Rather than looking for a replacement liver, they're trying to harness the body's own biological building blocks to grow new, healthy liver tissue. At the Department for Experimental Surgery at Berlin's Charite Hospital, scientists have developed something called a "bioreactor"--a plastic device slightly larger than a fist. Inside is a matrix of hundreds of membranes, within which they've coaxed human adult liver stem cells to grow into complex living tissue remarkably like a healthy liver. When the researchers feed a patient's blood through the reactor, the cultured liver takes over all the normal, healthy functions of the patient's own diseased organ.

Already the reactors are being used at clinics in Berlin and Barcelona to save the lives of transplant patients whose own livers have stopped functioning but whose donor organs haven't arrived. "We've been able to save the lives of 17 people so far," says Jorg Gerlach, who heads the Charite team. Their work shows how even small-team innovations need big help. "Organ transplantation requires people who can remove the organ, people who can tissue-type them, people who can preserve them," says Arthur Caplan, a bioethicist at the University of Pennsylvania and a World Economic Forum fellow. "That's a gigantic team approach there."

Gerlach now hopes to use the liver's tremendous regenerative capacity to make many transplants unnecessary in the future--by hooking patients up to the reactor so their own livers can take time off and recuperate. Gerlach's next project, which he is just getting underway at the University of Pittsburgh, is to use the tissue-growing techniques developed for the bioreactor to get the body to grow new liver tissue on its own. If it works, it could finally make those tragic waiting lists unnecessary.

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