The new 3-D-printed kidney tissue is the work of the Jennifer Lewis lab at Harvard, which has developed an innovative approach to “bioprinting” tissue. The technique allows researchers to print complex structures found in different types of human tissue, as well as vascular systems necessary to keep such tissue alive. The printing method uses multiple kinds of gel-like “inks.” After printing, the researchers remove one of the inks, leaving hollow tubes. Then they add cells, which mature into tissue.

Lab tests show that the engineered tissue demonstrates real kidney function to a degree that has not been achieved before, say the researchers. In particular, they were able to make the proximal tubule, a component of a nephron, the basic functional unit of the kidney. Nephrons filter the blood, keeping the useful stuff for the body and excreting the rest. If scientists could build a nephron, in theory they could build kidneys, but that will require developing several additional interconnected parts, which will probably take many more years.