The ability to engineer tissues in the lab for clinical purposes would provide important relief for the high demands and scarce supply of tissues and organs that are needed for life-saving transplantations. Additionally, engineered tissue from patient derived stem cells would potentially decrease the need to develop and use of animal models for xenotransplantation.

Credit: mailfor/iStock/Thinkstock

Three-dimensional (3D) printing technology using cell-laden hydrogels is a promising avenue of tissue engineering for human transplantations; however, certain technological constraints have limited the complexity and integrity of tissues built using 3D printing. Because soft and delicate materials are used to print tissues, it can be difficult to achieve enough structural support to create complex and thick shapes necessary to reproduce tissues and organs that are suitable for transplantation. A team at Wake Forest Institute for Regenerative Medicine (Winston-Salem, NC), led by Anthony Atala, has introduced a novel method that significantly improves the process of 3D bioprinting, enabling the creation of sturdy, complex, human-scale tissues that are suitable for in vivo implantation (Nat. Biotechnol. 34, 312–319; 2016).

To overcome the limitations of structural integrity that are presently associated with 3D bioprinting, the research team developed a unique system that prints a sacrificial scaffold of synthetic biodegradable polymers alongside cell-laden hydrogels. To increase survival of the printed tissues, layers of polymers and hydrogels are printed with a lattice of microchannel pores that allow for vascularization and the easy flow of nutrients and oxygen into the cells. The researchers used computer tomography and magnetic resonance imaging to create digital images of real tissues, which served as shape-templates for the 3D bioprinter.

To test their newly designed bioprinting method, the researchers printed human ear-shaped cartilage, rat calvarial bone and mouse skeletal muscle. In all three experiments, the tissues maintained good structural integrity and the cells constituting the printed tissues were healthy and viable. Importantly, the printed tissues remained healthy after in vivo implantation into rats or mice and showed signs of vascularization and incorporation with the surrounding tissues.

This novel method of 3D bioprinting creates new opportunities for producing human-scale tissues and organs for clinical use. Because the cells used for bioprinting can originate from the stem cells of patients themselves, this method could also side-step many of the problems that lead to transplant rejections.