A bioprinter – a three dimensional printer that uses living cells in suspension as its ink, and injection nozzles that can follow a CT scan blueprint – brings the dream of transplant surgery a step nearer: a bespoke body part grown in a laboratory and installed by a robot surgeon.
Scientists and clinicians began exploring tissue culture for transplant surgery more than 20 years ago. But researchers in the US report in Nature Biotechnology that they have harnessed a sophisticated, custom-designed 3D printer to print living muscle, cartilage and bone to repair battlefield injury.
The printed body parts so far have been tested only in laboratory animals. But tested organs have the size, structure and function for human use: once transplanted, they could be colonized by blood vessels and begin to grow and renew themselves normally. The study was backed by the US Armed Forces Institute for Regenerative Medicine.
Anthony Atala, who directs the Wake Forest Institute for Regenerative Medicine at Winston-Salem in North Carolina, described the bioprinter as an important advance. “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.”
Humans begin as one fertilised cell but develop into perambulating structures of a hundred trillion cells of around 300 different varieties. In 1998, US scientists announced that they had found a way to isolate and grow human stem cells – the tiny living agencies that differentiate into blood, brains, skin, bone, sinew and internal organs. By then, other research teams had begun to experiment with the idea that human tissue – they started with skin for burn patients – could be grown like yoghurt, in a culture, and then shaped into a structure such as an ear.
The Wake Forest team spent a decade developing their new bioprinter, called ITOP: Integrated Tissue and Organ Printing System. It uses biodegradable materials to form the shape of the tissue and water-based gels that contain the living cells.
The next challenge was to fabricate potential transplant tissue that would survive for long enough to be used in an operating theatre. So the “ink” that holds the cells carries nutrients and the printed tissue is latticed with tiny channels so that nutrients, water and oxygen can get to the living cells within the printed organ.
The institute had already made a baby’s ear and observed signs of blood vessel growth after an implant. The bioprinter results offer new hope and more confidence of success.
“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,” Atala said.
The researchers have printed human-sized ears and attached them under the skin of mice, to observe blood supply and the formation of cartilage tissue within two months. They planted muscle tissue within rats and observed nerve formation within two weeks. And in a five month test, bioprinted fragments of skull implanted in rats had formed bone tissue with its own blood supply.
