LONDON (Reuters) - Scientists have for the first time created a functional human liver from stem cells derived from skin and blood and say their success points to a future where much-needed livers and other transplant organs could be made in a laboratory.
While it may take another 10 years before lab-grown livers could be used to treat patients, the Japanese scientists say they now have important proof of concept that paves the way for more ambitious organ-growing experiments.
"The promise of an off-the-shelf liver seems much closer than one could hope even a year ago," said Dusko Illic, a stem cell expert at King's College London who was not directly involved in the research but praised its success.
He said however that while the technique looks "very promising" and represents a huge step forward, "there is much unknown and it will take years before it could be applied in regenerative medicine."
Researchers around the world have been studying stem cells from various sources for more than a decade, hoping to capitalize on their ability to transform into a wide variety of other kinds of cell to treat a range of health conditions.
There are two main forms of stem cells - embryonic stem cells, which are harvested from embryos, and reprogrammed "induced pluripotent stem cells" (iPS cells), often taken from skin or blood.
The Japanese team, based at the Yokohama City University Graduate School of Medicine in Japan, used iPS cells to make three different cell types that would normally combine in the natural formation of a human liver in a developing embryo - hepatic endoderm cells, mesenchymal stem cells and endothelial cells - and mixed them together to see if they would grow.
They found the cells did grow and began to form three-dimensional structures called "liver buds" - a collection of liver cells with the potential to develop into a full organ.
When they transplanted them into mice, the researchers found the human liver buds matured, the human blood vessels connected to the mouse host's blood vessels and they began to perform many of the functions of mature human liver cells.
The study's results offered "the distinct possibility of being able to create mini livers from the skin cells of a patient dying of liver failure" and transplant them to boost the failing organ.