The audiences at TED talks are used to being wowed as they learn about advances in technology. Even by TED standards, however, the 2011 presentation by Anthony Atala of the Wake Forest Institute for Regenerative Medicine was amazing. Unseen by the audience at first, various vials and nozzles hummed with mysterious activity behind Atala while he was on the stage. About two thirds of the way through the talk, a camera zoomed in on the device's internal armature and showed it weaving back and forth, depositing living cells grown in a laboratory culture layer by layer on a central platform, basing its activity on highly accurate three-dimensional digital renderings. The process, known as 3-D printing, resembles the operation of ink-jet printers but, in this case, instead of ink the printer uses a solution of living cells. In the end, Atala's machine produced, layer by layer, a life-size kidney made of human cells, much as a personal 3-D printer can spit out, say, a plastic replacement part for a coffeemaker.
A straightforward and quick way to make organs would be a welcome development for the more than 105,000 Americans waiting for organ donations. But the printed kidney Atala demonstrated two years ago was not ready to implant. It lacked two crucial elements: working blood vessels and tubules for collecting urine. Without these or other internal channels, large organs such as the kidneys have no way to get crucial nutrients and oxygen to, or remove waste products from, the cells deep within their interiors, and those cells quickly die. Researchers have tried to print these hollow structures layer by cellular layer into the organ by leaving holes in the right spots on each level, but the method produced conduits that can collapse and seams that can rupture under pressure from the blood being pumped by the heart.