Scaffold-free 3D bioprinted tracheas successfully transplanted into rats

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Researchers from Saga University and Nagasaki University in Japan have used a Cyfuse Biomedical Regenova 3D bioprinter for scaffold-free trachea regeneration. Tracheal transplantation was successfully performed in nine rats.

When attempting to biologically engineer a new trachea—or any airway organ, for that matter—stability is key. Think about it this way: if a transplanted, biologically 3D printed ear collapses, it’s a problem for the transplant recipient, but not a life-threatening one. But if a 3D printed trachea collapses, the patient is in big, big trouble, since they lose the ability to breathe.

Scientists differ in their opinions on how to ensure a stable trachea: some bioengineers think scaffolds are the best way to create artificial airway organs, but this approach can pose problems and limitations. That’s why a team of researchers led by Saga University’s Koichi Nakayama—who has previously carried out studies on the 3D bioprinting of liver tissue in rats as part of Nakayama Labs—has used a 3D bioprinter to create scaffold-free artificial tracheas. The researchers say their 3D printed tracheas are strong enough to prevent collapse, and have tested the structures on rats to prove it.

Working with a number of researchers from Nagasaki University, Nakayama wanted to carry out a study in order to develop a new scaffold-free approach for creating an artificial trachea, using some of the most advanced 3D bioprinting technology available. In the study, the team made scaffold-free trachea-like grafts generated from isolated cells in an inbred animal model.

Although Nakayama has admitted that the budget for the study was low, the researchers nonetheless had an impressive piece of bioprinting machinery at their disposal: a Regenova bioprinter from Cyfuse Biomedical. The Regenova is unique in its use of the “Kenzan method,” which involves, somewhat bizarrely, skewering spheroids of cell clusters onto sharp spikes to keep them in position. It’s probably the most advanced kind of kebab in the world!

Illustration of the bioprinting and implantation process

With the Regenova to hand, the Japanese researchers went about collecting chondrocytes and mesenchymal stem cells from F344 lab rats, purchasing rat lung microvessel endothelial cells separately. Then, using the Regenova 3D bioprinter, the researchers were able to 3D print tiny artificial tracheas using the aforementioned skewering process, letting the structures mature in a bioreactor to ensure cell growth.

During this incredible bioprinting process, the Cyfuse Biomedical printer placed spheroids in a 9 × 9 needle array measuring 3.2 mm in length per side. The outer diameter of each stainless steel needle was 0.17 mm, and the distance between each needle was 0.4 mm. The cell spheroids were aspirated by a robotically controlled 25-gauge nozzle from a 96-well plate. In total, 384 spheroids were used to generate a tubular 3D printed trachea.

Once fully matured, the 3D printed, scaffold-free tracheas were transplanted into F344 rats as a tracheal graft, with each animal under general anesthetic. Then, once implanted, the mechanical strength of the artificial tracheas was measured and histological and immunohistochemical examinations performed.

In total, nine rats were used in the experiment, each of which was closely examined for 23 days following the transplantation of the bioprinted tracheas. Over the course of that examination stage, the researchers found that the 3D printed tracheas were strong enough for transplantation when assisted with silicone stents, used to prevent collapse of the artificial trachea and to support the graft until there was sufficient blood supply. Chondrogenesis and vasculogenesis were observed histologically.

Although two of the lab rats experienced “wheezing” due to retention of tracheal secretions, the reearchers say their bioprinted tracheas were an overwhelming success. The consequence of this? 3D bioprinting appears to be an effective means of creating artificial trachea replacements for rats. Could it do the same for humans? Time will tell.

The study, “Scaffold-free trachea regeneration by tissue engineering with bio-3D printing,” can be read here.