3D printer makes tiniest human liver ever
Lab-grown livers have come a step closer to reality thanks to a 3D printer loaded
with cells (see video above). Created by Organovo in San Diego, California, future versions of the system could produce
chunks of liver for transplant.
The mini-livers that Organovo made are just half a millimetre deep and
4 millimetres across but can perform most functions of the real thing. To create them, a printer builds up about 20 layers
of hepatocytes and stellate cells – two major types of liver cell. Crucially, it also adds cells from the lining of
blood vessels. These form a delicate mesh of channels that supply the liver cells with nutrients and oxygen, allowing the
tissue to live for five days or longer. The cells come from spare tissue removed in operations and biopsies.
liver assays, based on single or double layers of cells, only last two days and don't have the same range of functions as
The realistic structure and functioning of the mini-livers make them good predictors
of the toxicity of drugs and other substances. They produce albumin, the liver protein that bulks up blood and ferries hormones,
salts and drugs throughout the body. They also make cholesterol, which carries fat in the bloodstream, and produce major
detoxification enzymes, called cytochrome P450s, that metabolise drugs in the liver.
goal is to create human-sized structures suitable for transplant; the big hurdle is being able to print larger branched
networks of blood vessels to nourish such an organ. The company unveiled the mini-livers at the annual Experimental Biology conference this week in Boston.