It may be small, but is it perfectly formed? A tiny human liver, just 5 millimetres in size, has been grown inside a mouse. It remains to be seen whether the organ can replicate all liver functions – and if it will be possible to scale up the tiny structure to useable dimensions. Hideki Taniguchi and Takanori Takebe at Yokohama City University generated induced pluripotent stem cells from human skin cells, then encouraged them to develop into liver precursor cells. They added another class of stem cells – mesenchymal stem cells – and a third group of cells from the lining of blood vessels. Without the aid of any underlying scaffold, the cells “guided themselves” and generated a microstructure almost identical to normal liver tissue, says Takebe.
