In a bid to beat the problem, Borenstein teamed up with transplant surgeon Vacanti, who in 1997 famously grew a human ear from cartilage cells on the back of a mouse. The idea the pair hatched involves copying the blood vessel network of a real liver and using 3D computer modelling and machining to mimic its construction.
First, they injected a liquid plastic into the blood vessels of a liver. Once the plastic had solidified, they dissolved the liver tissue, leaving a solid cast of the organ's blood vessels. From this model they were able to take measurements of vessel diameters, branching angles and the distances between vessels. They fed the numbers into software that built a 3D fractal-like computer model of a liver's blood supply. When they simulated blood flowing through the "liver", it had the same blood flow properties as the living system, says Borenstein.
The 3D blood vessel model is then "sliced up" inside the computer, dividing the model into a series of horizontal layers, each of which is used to make a silicon mould. PLGA is then poured into each mould to make the many slices that when sandwiched together, under pressure and heat, create a scaffold for the artificial liver. It's shot through with channels as small as the finest capillaries and as large as the organ's main veins and arteries.
The scaffold then has to be seeded with the cells that make up the solid part of the liver. As well as hepatocytes, which perform key liver functions such as breaking down toxins and metabolising proteins and carbohydrates, there are at least six other types of cells. Borenstein says there are two possible ways of seeding this complex network of different cell types. You could seed each layer separately with different cell types, or inject them from the outside. But the pair won't yet say how this is done.
To get the blood supply working, a solution of endothelial cells, the cells that normally line blood vessels, is pumped into t
Contact: Claire Bowles