With human liver tissue in critically short supply, the Mayo Clinic in Rochester, MN, is working to create a liver dialysis machine that uses pig liver cells. It's a step up from using whole pig livers for temporary treatment, because isolated cells present a lower risk of contamination and can stay alive longer.

Principal investigator Scott L. Nyberg tested his machine in late 2005 in a preclinical study on dogs with drug-induced liver failure. The dogs on the machine lived longer than control subjects and did not develop signs of brain swelling. "We want to extend the life span of the cells and duration of the treatment" compared to existing methods, Nyberg says. Some 40,000 Americans die of liver failure annually; Nyberg recalled a teenager who died 14 hours before a donor became available. "A device like this could have kept her alive just that one more day."