Scientists in Japan have for the first time created a functioning human liver using artificially generated stem cells.

The research, details of which were published online by the journal Nature is being hailed as a significant step-forward in attempts to grow new or regenerate damaged human organs.

The liver was made in the laboratory when scientists at the Yokohama City University Graduate School of Medicine combined the stem cells with two other cell types required for the development of the human liver.

The resulting tiny early liver tissue structure, known as a bud, was then transplanted into a mouse, where it matured into tissue resembling the adult liver.

The liver continued to keep the mouse alive, even after scientists induced the failure of the mouse's own liver.

Human liver tissue has previously been created in the lab, but the process has been beset with problems and challenges.

What is different in this research is the method used.

In it the liver bud was created by focusing on the earliest stage of organ generation using Induced Pluripotent Stem cells (IPS).

These are artificially generated stem cells, created when basic human cells, like for example skin cells, are genetically reprogrammed into an embryonic stem cell-like state.

IPS's can then be induced or forced to develop into a particular organ or tissue. In this study the IPSs were allowed to self organise and combine with two other cell types required for liver creation, to recreate the cellular interactions that normally take place during bud development.

Following transplantation into the mouse, the organ then developed a vascular system and performed liver-specific functions within a period of between 10 days and one month.

Although it has yet to be proven whether such a technique will work in human patients, the study has raised hopes and provided proof that organ bud transplantation could become a promising new approach towards regenerating failed or severely damaged organs, including the liver, kidney, lung and pancreas.

The report’s authors estimate that up to 30% of liver function in a damaged liver could be restored using the technique.

They say it could be particularly effective in treating new born babies and children with critical liver damage.

However, experts have cautioned that such treatments remain a long way off, and that it could be a decade before they are tested in humans.

Although he said it was an important step along the road to creating artificial organs, Professor Martin Clynes, Director of the National Institute for Cellular Biotechnology at DCU warned a large number of hurdles will have to be overcome before the treatment could become a reality.

He said the safety of the IPS cells following transplantation would have to be assessed. And work would have to be done to assess how long the regenerated liver would remain functional, he added.