Functional Human Liver Grown from Stem Cells

Researchers in Japan said Wednesday that functional human liver tissue they grew from an assortment of human stem cells could pave the way toward alleviating a critical shortage of donor organs.

In laboratory tests, the 0.2 inch-long, man-made "liver buds" - precursor clusters to a developed liver - were transplanted onto a mouse brain, where they matured into a "functional human liver," the researchers wrote, according to Medical Express.

"To our knowledge, this is the first report demonstrating the generation of a functional human organ from pluripotent stem cells," the researchers wrote in the abstract to their report. Pluripotent stem cells are those that can turn into any type of cell in the body.

While the technique has yet to be tested in humans, the work serves as "an important proof of concept," the researchers wrote.

"We proved that liver bud transplantation could offer therapeutic potential against liver failure," Professor Takanori Takebe, a stem cell biologist who led the research at Yokohama City University in Japan, told The Daily Telegraph.

"This is a proof of principle approach. We're now planning to transplant the liver buds into the liver. To do that we have to reduce the size of the liver buds to a very small scale. That way they can be injected into the blood stream."

Takebe suggests that by injecting thousands of the liver buds in to the bloodstream of patients, the buds will become incorporated into their damaged liver and restore its function.

"I am optimistic that with a large infusion of several hundreds of thousands of liver buds, around 30 percent of the patient's original liver function, could be restored and that should be enough to restore a viable liver system for that patient."

Professor Malcolm Alison, a stem cell biologist at Queen Mary University of London, told the Telegraph that the study was "a major step forward in improving the effectiveness of liver cell transplantation for treating acute liver failure."

"This science opens up the distinct possibility of being able to create mini-livers from the skin cells of a patient dying of liver failure, and when transplanted would not be subjected to immune rejection as happens with conventional liver transplants today," Alison said.

But it will still be at least 10 years before anyone may receive the first stem cell-grown liver transplant, and some scientists are skeptical about the viability of the technique.

Stuart Forbes, of the Centre for Regenerative Medicine at University of Edinburgh, said: "Although exciting, there is still a lot more research needed before this approach could be applied to patients with liver disease.

"The liver buds were small and scaling up to a 'human relevant size' may be a challenge, as will creating a true liver structure."

Takebe and his colleagues' research is published in the journal Nature.