Oregon Health & Science University researchers have genetically engineered mice to produce human liver cells which could be used in studies for testing the safety and efficacy of drug lead candidates. It has created a severely immunodeficient mouse strain that develops liver disease only when the animals don't receive a protective drug called NTBC, allowing liver disease to be turned on and off.

"Our mice on this medicine are perfectly healthy, normal mice, and only when we take them off the NTBC do they get liver disease," Grompe said. "It's an easy system that any research lab should be able to set up, which is very different from what's around now."

In fact, the human liver cells from the repopulated mouse livers are indistinguishable from normal human liver cells, according to the study. "The healthy human liver cells take over and replace the sick mouse liver cells," Grompe said. "You end up with a healthy mouse that makes human blood clotting factors, all the proteins the liver makes, human bile, everything."

OHSU has filed a patent application on the technology and, in cooperation with Grompe, has spun it off into a Portland-based start-up company named Yecuris through the university's Springboard Program. Considering that the worldwide market for human liver cells the pharmaceutical industry uses for testing candidate drug compounds is estimated at $2 billion a year, Yecuris business plan seems to be a viable. The study has been published in Nature Biotechnology.