Scientists prove feasibility of 'printing' replacement tissue
16 February 2016
Using a custom-designed 3D printer, scientists have proved that it is feasible to print living tissue structures to replace injured or diseased tissue.
Reporting in Nature Biotechnology, the scientists, Wake Forest Institute for Regenerative Medicine (WFIRM), said they were able to print ear, bone and muscle structures. When implanted in animals, the structures matured into functional tissue and developed a system of blood vessels. Most importantly, these early results indicate that the structures have the right size, strength and function for use in humans.
"This novel tissue and organ printer is an important advance in our quest to make replacement tissue for patients," says WFIRM director, Dr Anthony Atala who was senior author of the Nature Biotechnology paper. "It can fabricate stable, human-scale tissue of any shape. With further development, this technology could potentially be used to print living tissue and organ structures for surgical implantation."
His work was funded by the Armed Forces Institute of Regenerative Medicine, a US federally funded effort to apply regenerative medicine to battlefield injuries.
Tissue engineering is a science that aims to grow replacement tissues and organs in the laboratory to help solve the shortage of donated tissue available for transplants. The precision of 3D printing makes it a promising method for replicating the body's complex tissues and organs. However, current printers based on jetting, extrusion and laser-induced forward transfer cannot produce structures with sufficient size or strength to implant in the body.
The Integrated Tissue and Organ Printing System (ITOP), developed over a ten-year period by scientists at the Institute for Regenerative Medicine, overcomes these challenges. The system deposits both bio-degradable, plastic-like materials
to form the tissue 'shape' and water-based gels that contain the cells. Moreover, a strong, temporary outer structure is formed, and the printing process does not harm the cells.
A major challenge of tissue engineering is ensuring that implanted structures live long enough to integrate with the body. The WFIRM scientists addressed this in two ways. They optimised the water-based 'ink' that holds the cells so that it promotes cell health and growth and they printed a lattice of micro-channels throughout the structures. These channels allow nutrients and oxygen from the body to diffuse into the structures and keep them live while they develop a system of blood vessels.
It has been previously shown that tissue structures without ready-made blood vessels must be smaller than 200 microns for cells to survive. In these studies, a baby-sized ear structure survived and showed signs of vascularization at one and two months after implantation.
"Our results indicate that the bio-ink combination we used, combined with the micro-channels, provides the right environment to keep the cells alive and to support cell and tissue growth," says Atala.
Another advantage of the ITOP system is its ability to use data from CT and MRI scans to 'tailor-make' tissue for patients. For a patient missing an ear, for example, the system could print a matching structure.