EmTech: 3-D Printing Complex Kidney Components

Earlier this year a group at Harvard solved one of the most difficult challenges involved in growing artificial human organs. The team used a 3-D printer to make human tissue that includes rudimentary blood vessels. Emboldened by that success, the researchers have started an ambitious project to make fully functioning printed kidneys.

Speaking at MIT Technology Review’s EmTech conference, Jennifer Lewis, professor of biologically inspired engineering at Harvard, said the ultimate goal—creating functioning human organs—is a “really long moon shot.” But she added that her group has made significant progress by fabricating rudimentary versions of structures in kidneys called nephrons. These artificial nephrons will allow drug companies to quickly screen potential medications, and they should help scientists understand kidneys at a more detailed level.

To produce tissues with blood vessels, Lewis’s group has invented novel 3-D printing inks and nozzles that allow it to precisely print multiple materials. For example, it can print various types of cells and materials that help connect cells. One of these inks allowed the group to make tunnels inside the tissues, which the researchers lined with blood vessel cells (see “Artificial Organs May Finally Get a Blood Supply”). Lewis said her group is using the same approach to making the tubes inside kidneys that help filter blood.

Lewis said the group chose to focus on kidneys because they account for 80 percent of the need for organ transplants, and because a large numbers of patients die before ever receiving a replacement kidney.

Other research groups have been printing thin sheet of cells—which grow to form functional tissues—for several years now (see “Printing Muscle”). But these efforts have been limited to making thin sheets; anything thicker than about half a millimeter means nutrients can’t get to the innermost cells, while waste can’t be evacuated. To make them thicker, and to eventually produce complete organs, researchers need to engineer a network of blood vessels.

Plenty of work remains, Lewis said—including integrating different cell types to make functional nephrons. Making complete organs will also require making more complex shapes and structures. For example, in kidneys you need to make blood vessels that branch into smaller ones—including capillaries so thin they’ll probably be beyond any existing printing technique.