Lab-grown organs and tissues have still not achieved the critical breakthrough, though, as they have to be painstakingly built in the laboratory by hand. Clearly this method is not ideal for large groups of patients, nor does is present a real alternative to organ donation.  Lab-grown organs would have to be industrially manufactured if production is to be scaled up enough to meet need. So Dr. Atala’s team came up with a new idea: Printing organs using 3D printing. 

3D printing, also called additive manufacturing, is the process of creating a physical object from a digital design. The rectangular printer deposits successive layers of material, which results in a 3D object.   “3D printing offers the advantages of precision and scalability,” Dr. Atala says about his choice to use 3D printing for organ and tissue engineering. 

14 years ago, long before the 3D-printing hype and the maker movement took off, the lab at Wake Forest Institute for Regenerative Medicine used a desktop inkjet printer that was modified to print three dimensionally. Over the course of a decade, the lab designed and built a large, 800-pound printer with the capability to print cells and materials to form the support structure for these cells in a layer-by-layer fashion.

Whereas a desktop printer usually uses printer’s ink, 3D printing uses plastic, rubber, etc.  The 3D printer at the Wake Forest lab uses a special bioink. Finding a good, usable bioink has been a long learning process. “The challenges we have worked to overcome include keeping the cells alive during the printing process and printing at a resolution high enough to reproduce the complex structure of organs,” Dr. Atala recalls. 

The bioink used in the lab today consists of bio-degradable, plastic-like materials to form the tissue “shape” and water-based gels that contain the cells. The team is currently printing using several types of stems cells. This includes amnion-derived cells, which Dr. Atala and a team of Harvard University researchers managed to harvest from the amniotic fluid of pregnant women in 2007. This smart bio-material can be manipulated to differentiate into various types of mature cells that make up nerve, muscle, bone, and other tissues

To date, Dr. Atala’s team has implanted bio-printed skin, cartilage, bone and muscle into pre-clinical models. 3D organ printing is still in the experimental stage and not ready for use in patients. The current objective is to develop a method for printing solid organs with more complex structures.

Skin is a simple organ due to its flat structure and because it is made up mostly of one cell type. Hollow organs like the bladder and stomach, and solid organs like the kidney and liver, are more complex, since they require multiple cells types, and require more oxygen because of their cell density. 

Furthermore, the printed organs must have the same functionality as native organs. “Organs and tissues do not come off the printer fully functional,” Dr. Atala says.  “It is only after implantation in the body – nature’s incubator – that full function occurs.” To be implanted into a human body, a printed organ needs blood vessels. Vessels are another complex and tricky object to print.  “This is another major challenge. Our current solution is to print a lattice of micro-channels throughout the structures,” Dr. Atala explains.  These channels allow nutrients and oxygen from the body to diffuse into the structures and keep them alive while they develop a system of blood vessels.

According to Dr. Atala, it is hard to say when first 3D printed organ will be ready to be implanted into a human body: “When we started this work, we really had no idea what innovations and breakthroughs would occur over the next 14 years, so it is difficult to predict how far we can take the technology.” With 3D printing boosting tissue and organ engineering, it seems that the work on organ transplantation Joseph Murray started in 1954 may soon achieve a whole new level.