Unlike axolotls with their terrific regenerative capacities, once humans lose an organ or a limb, it’s gone. And they need to get a new one.

To an extent, the human liver is a notable exception, given its capacity to regenerate fully from as little as 25% of its original size. However, chronic liver diseases often do irreparable damage and the resulting scar tissue loses its regenerative abilities. The only way to treat such permanent organ failure is transplantation, and for that you need someone else to give up their liver. Of course, there is always shortage of donor organs.

But what if we could actually grow a new organ to replace the damaged one? A team of scientists from Japan has been chipping away at this exact problem, using liver as its proof-of-concept tissue. Last year Takanori Takebe, a stem-cell biologist at Yokohama City University, announced successfully growing rudimentary liver tissue in a petri dish. Since then, his lab has definitely not been idle.

The researchers used induced pluripotent stem cells (iPSCs), which themselves are a remarkable feat of science.  These stem cells, which do not involve using embryos, are reprogrammed from the patient’s own cells, usually from the skin. Being pluripotent, they can generate nearly every cell type in the body if you give them the right information.

Takebe’s team mixed human liver cells created from iPSCs with cells that make blood vessels and cells that create connective tissue. These blobs of cells performed the usual cell interactions that happen at the stage when an organ is just forming, and grew into tiny “liver buds,” complete with primitive blood vessels.

The researchers transplanted the miniature, 5mm large cell formations from petri dishes into mice and connected them up with local blood vessels. Amazingly, that worked. The buds grew into fully functional livers capable of the usual tasks you would want a liver to do — they soon had them metabolising drugs and creating blood proteins.

In the paper published in Nature yesterday, the authors note this to be “the first report demonstrating the generation of a functional human organ from pluripotent stem cells. Although efforts must ensue to translate these techniques to treatments for patients, this proof-of-concept demonstration of organ-bud transplantation provides a promising new approach to study regenerative medicine.”

Of course, this remarkable feat is not bringing us lab-grown human livers just yet. For one, iPSCs have a propensity to grow tumours, so their safety in creating organs from scratch will need to be studied. As Ernst Wolvetang of Australian Institute for Bioengineering and Nanotechnology, who wasn’t involved in the study, pointed out: “It remains to be established whether the artificially regrown livers from iPSC will prove to be safe in the long-term.”

Here’s hoping they will.