ESOT 2015: Printing the human body. Mr Gabriel Oniscu, Royal Infirmary of Edinburgh, and Dr Menna Clatworthy, Pembroke College, Cambridge, discuss this fascinating session

by Maria Dalby: In a not too distant future, scientists may be able to print tissues and organs for transplantation using technology that is not a million miles away from inkjet printers used with computers, only with slightly different types of ink. It may sound like science fiction, but a team at Wake Forest School of Medicine in North Caroline, USA has developed methods for printing cells into 3D tissue matrixes to form structures such as skin, muscle fibres and a human ear. Professor John D Jackson  (Wake Forest School of Medicine, North Carolina, USA) gave the audience at ESOT a glimpse of this revolutionising new technology.

In 3D bioprinting, cells and other biological material – the bio ink – is deposited very precisely in a tissue construct made of hydrogel or synthetic polymers, or as in the Wake Forest centre, a combination of both for increased stability known as the Integrated Organ Printing System. The actual printing method is extrusion-based rather than jet-based – this means the resolution is relatively low at around 100μm, but the nozzle can deposit higher cell concentrations and high viscosity materials which allows for a wider range of materials to be delivered. The shear stress associated with the extrusion process may affect cell viability which means the printing process must be kept quite slow.

Images from MRI and CT scans can be used to create patterns for printing. One example is a fragment of jaw bone that was printed from an MRI image, using reverse engineering to generate a CAD/CAM drawing. Other structures that have been printed at Wake Forest include a human ear, a muscle construct, and a complex muscle-tendon construct which involved two different types of tissue constructs and cells. An important achievement was the printing of cardiac organoids and cardiac bundles which were able to mature in their tissue constructs and start beating.

The most advanced method at Wake Forest which is expected to begin clinical trials within the next few years, is the technique of printing skin directly onto wounds. Such a method could be used for repairing burn injuries at the patient’s bedside. Animal data indicates that bioprinted cells promote wound re-epithelisation and healing compared with untreated injuries.

As yet, 3D bioprinting can only be used to create small, flat structures like skin, or tubes like urethras or vessels. To contemplate printing larger and more complex structures, scientists first need to solve the conundrum of vascularisation of the printed constructs – until this can be achieved there can be no prospect of printing solid organs. In addition there is a need for more sophisticated bio ink and tissue construct materials and better nozzles to allow faster printing without jeopardising cell viability. However, despite these limitations, Professor John D Jackson is confident that 3D bioprinting will transform the landscape of transplantation and tissue engineering in the future.