By Alice Klein
SEBASTIAN KAULITZKI/SCIENCE PHOTO LIBRARY/GETTY IMAGES
Human-like ears have been grown on the backs of mice using 3D printing. The technique could potentially be used to construct new ears or other body parts in people without the need for surgery.
3D printing is increasingly being used to custom-build new body parts, like jaws, ribs and spinal vertebrae. But these parts must be printed outside the body and then surgically implanted, which carries an infection risk.
Now, Maling Gou at Sichuan University, China and his colleagues have shown that body parts can be 3D printed inside the body, at least in mice, so that surgery is not required.
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First, the researchers injected a “bio-ink” made of hydrogel particles and cartilage cells into the backs of mice. Next, they shone ear-shaped patterns of near-infrared light onto the ink. The light caused the hydrogel particles to stick together and develop layer-by-layer into ear-shaped structures.
Over the next month, the cartilage cells grew around the hydrogel structures, eventually resembling the cartilage structures of real human ears. The mice had no significant inflammation or other side-effects.
The famous Vacanti mouse of the 1990s also had a human-like ear grown on its back, but it was made by implanting a pre-made plastic scaffold seeded with cartilage cells underneath the skin, rather than 3D printing the scaffold directly at the site.
The researchers hope the new technique could be used to construct new ears for people born with a condition called microtia that prevents the ears from developing properly. “We are making efforts to improve this technique for future treatment of human ear defects,” says Gou.
The nonsurgical 3D printing technique could also potentially be used to repair damaged cartilage in noses, fingers, toes or elbows, says Derek Rosenzweig at McGill University in Canada. In contrast, hip and deep knee cartilage defects may be harder to fix, because near-infrared light usually only penetrates about 2 centimetres into the body, he says.
Gou’s team hopes to eventually adapt the technique to fix other damaged organs like the heart or lungs. However, this will be more challenging because the heart and lungs contain multiple cell types, are deeper in the body, and are constantly contracting and relaxing, says Rosenzweig.
Journal reference: Science Advances, DOI: 10.1126/sciadv.aba7406
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