Researchers from Massachusetts Institute of Technology and Harvard Medical School designed an artificial functioning vascular system built of tiny vessels. They did it with the aid of computers. So the first step has been made towards artificial creation of a real living organ.
Research laboratories have already learnt to grow such organs as skin or cartilaginous tissue. But the impossibility to create a vascular system that would ensure the functioning of an organ hindered the work on the creation of a self-sufficient artificial organ, such as liver or kidneys. So the above achievement of the scientists is very impressive.
The network consists of arterial and venous capillaries with the diameter from 3 mm to 10 microns.
To manufacture the capillary structure, they used a kind of segmentation – each vessel was composed of two semicylinders. First, grooves that imitate the paths of capillaries and vessels were etched on a silicon plate. Then the grooves were filled with biodegradable polymer. After that a second plate of the same kind was manufactured with the mirror arrangement of grooves. The plates with a microporous membranous layers sandwiched between them were put together. As a result, an artificial vascular system was produced. After implantation, the body cells penetrate the microporous layer, destroy the polymer inside the vessels and coat the capillary walls. As a result, normal blood vessels with walls composed of body cells were produced.
This method allows the liver or kidney tissue to be provided with a sufficient amount of oxygen or nutrients. Experiments on animals – implantation of a single-layer vascular structure – produced impressive results. It is estimated that a sandwich of 30 to 50 layers of cells must be produced for creating a self-sufficient organ.

Source: materials of New Scientist.