12th October 2018

Complex 3D printing of human cells

Researchers have developed a method to 3D print cells to create human tissue such as ligaments and tendons, which could greatly improve a patient's recovery. In the future, their technique could lead to 3D printing of whole organs.



Credit: Dan Hixson/University of Utah College of Engineering

With today's technology, we can 3D-print sculptures, mechanical parts, prosthetics, and even guns and food. But a team of University of Utah biomedical engineers have developed a method to 3D-print cells to produce human tissue such as ligaments and tendons, a process that will greatly improve a patient's recovery. A person with a badly damaged ligament, tendon, or ruptured disk, for example, could simply have new replacement tissue printed and ultimately implanted in the damaged area.

"It will allow patients to receive replacement tissues without additional surgeries and without having to harvest tissue from other sites, which has its own source of problems," says assistant professor Robby Bowles, who worked with former biomedical engineering master's student, David Ede.

The 3D-printing method, which took two years to research, involves taking stem cells from the patient's own body fat and printing them on a layer of hydrogel to form a tendon or ligament, which would later grow in vitro in a culture before implantation. The process is extremely complicated, because that kind of connective tissue is made up of different cells in complex patterns. For example, cells that make up the tendon or ligament must then gradually shift to bone cells so the tissue can attach to the bone.

"This is a technique in a very controlled manner to create a pattern and organisations of cells that you couldn't create with previous technologies," Bowles says of the new process. "It allows us to very specifically put cells where we want them."



This image of cells that were made fluorescent shows how they are printed in complex structures. Credit: Robby Bowles/University of Utah

To do that, Bowles and his team worked with Salt Lake City-based company, Carterra, Inc., which develops microfluidic devices for medicine. Researchers used a 3D printer from Carterra typically used to print antibodies for cancer screening applications. But Bowles' team developed a special printhead for the printer that can lay down human cells in the controlled manner they require. To prove the concept, the team printed out genetically-modified cells that glow a fluorescent colour so they can visualise the final product, as shown in the image above.

Currently, replacement tissue for patients can be harvested from another part of the patient's body or sometimes from a cadaver, but they may be of poor quality. Spinal disks are complicated structures with bony interfaces that must be recreated to be successfully transplanted. This 3D-printing technique can solve those problems.

Bowles, a specialist in musculoskeletal research, said the technology is currently designed for creating ligaments, tendons and spinal discs, but "it literally could be used for any type of tissue engineering application," he says. It could even be applied to the 3D printing of whole organs, an idea researchers have been studying for years and that may be possible by 2025. Bowles also says the technology in the printhead could be adapted for any kind of 3D printer. His team's work is published in the Journal of Tissue Engineering, Part C: Methods.



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