3D printers may hold the key to successfully producing the first transplantable kidneys for humans. Before 3D bioprinting was widely available, researchers were using pig kidneys as scaffolds to hold human kidney cells.  They would take a pig kidney and wash away the internal cells, leaving the basic structure behind. Then, they would use human or animal cells to fill the scaffold back up. This process has never resulted in a kidney that could be successfully transplanted into a human.

Now, thanks to advances in bioprinting, researchers have found a way to forgo the pig parts entirely. Instead, they use a 3D printer to build the scaffold. In the future they may even be able to print with the patient's own cells, creating a truly customized replacement organ. If it works, it will mean less likelihood of organ rejection and give hope to more than 96,000 people who are waiting for kidney transplants.

There are several laboratories spearheading kidney replacement research. The one most noted for using 3D printing methods is the Wake Forest Institute for Regenerative Medicine.

Dr Anthony Atala is the lead researcher at Wake Forest. They are using a 3D bioprinter to create miniature prototype kidneys for study.  The bioprinter lays down kidney cells along with the scaffold that holds those cells together. Layer by layer, a new kidney emerges.

The obstacles to printing a fully-functional human organ are many and varied. Scientists already know they will face an uphill battle because there is no guarantee that a patient's body will accept the printed kidney even if they manage to make it. Until they can create an organ made entirely from the patient's own cells, there is a big risk of rejection. Also, the kidneys that are currently being created do not function as well as real kidneys; not by a long shot. It may take another ten to twenty years before hospitals will be able to print new organs on demand.

Dr. Atala gave a TED talk on his process a couple of years ago. You can view one of the printed kidneys at 11:22.