Using small pieces of human liver that were grown from stem cells, a team led by researchers at Japan's Yokohama City University was able to significantly restore liver function in mice through only a simple transplant — and they hope to eventually use the same method to save human lives. The team took tiny, lab-grown "liver buds" and inserted them into mice, where within two days the cells hooked into surrounding blood vessels and began performing natural functions of the liver. Though the team has yet to track the long-term health of the mice following the procedure, Nature reports that the animals remained alive and well despite prior liver issues.

Having only been demonstrated on mice, the method is still being considered a proof of concept. But the hope is that its immediately promising results can soon be applied to regenerative medicine. The short supply of liver donors has made growing replacements a high priority for interested researchers, but the Yokohama team's work — which was published today in Nature — remains a preliminary step toward that goal: one of the team's leaders told Nature that testing the process in humans is still years away. Among the biggest hurdles is simply the difficulty of growing enough cells to actually test them in human patients.