Appearance of the engineered ear with embedded wire framework implanted in a rat for 12 weeks (a) Before explant. (b) After explant. (c) Image of explanted engineered ear without an embedded wire framework. (d) The explanted engineered ear with wire framework maintained its shape and could be elastically deformed. (Ç Royal Society Publishing)
Lead author, Dr Thomas Cervantes explains, ‘This is the first demonstration of a full-size human ear that maintains shape and flexibility after 3 months.’
The new model, which incorporates an embedded titanium wire to maintain shape, has previously been demonstrated on a smaller scale, implanted on the back of a mouse, but this study demonstrates minimal distortion of a full-size adult ear, when embedded on a rat.
The team at Massachusetts General Hospital combined collagen from cows with ear cartilage cells from sheep, which they moulded into ear structures using 3D printed scaffolds. After 3 months implanted on the backs of male nude rats, ears which contained a thin wire framework showed much less distortion of the initial ear shape, compared with ears without wire support.
Cervantes adds, ‘Shape and flexibility are key; tissue engineered constructs tend to distort in shape during growth, which is obviously a problem for the ear, because we are aiming to recreate a very specific shape.’
All implants were well tolerated and no exposure or extrusions occurred during 12 weeks in vivo. However, when extracted, the implants containing wire resembled a human ear, whereas implants without wire were flattened and distorted. The implants containing the titanium framework also exhibited similar flexibility to a human ear.