Lab-Grown Ears: Swiss Researchers Advance Biofabrication of Elastic Cartilage
For over three decades, scientists have strived to engineer a functional human ear in the laboratory using a patient’s own cells. Now, researchers at ETH Zurich, in collaboration with the Friedrich Miescher Institute in Basel and the Cantonal Hospital of Lucerne, have achieved a significant milestone: the creation of elastic cartilage with mechanical properties closely resembling natural ear tissue. Whereas challenges remain in stabilizing elastin for long-term durability, this advancement brings functional ear reconstruction closer to reality.
The Quest for a Lab-Grown Ear
The pursuit of lab-grown ears is driven by the need for improved reconstructive options for individuals who have lost ear tissue due to burns, trauma, or congenital conditions like microtia – a malformation affecting approximately four in every 10,000 children 1. Current reconstruction methods often rely on harvesting cartilage from the patient’s rib, a procedure that can be painful, cause scarring, and result in a reconstructed ear that lacks the natural flexibility of real ear tissue.
Breakthrough in Elastic Cartilage Engineering
Building on previous work – including a 3D-printed ear demonstrated by Professor Marcy Zenobi-Wong at ETH Zurich in 2016 1 – the team has successfully produced elastic cartilage in vitro using human ear cartilage cells. This engineered cartilage exhibits stability comparable to that of a natural ear and, in animal models (rats), maintained its shape and elasticity for six weeks 1, 3.
The Role of Elastin and Future Challenges
A key challenge in recreating natural ear tissue lies in replicating the properties of elastin, the protein responsible for the ear’s flexibility and recoil. Researchers are working to not only induce cells to synthesize elastin but also to ensure its proper assembly into a stable, long-lasting network 3. Without a robust elastin network, the long-term structural integrity of the engineered ear is compromised.
The Fabrication Process
The researchers began with cartilage remnants from corrective ear surgery, isolating approximately 100,000 cells from a 3-millimeter fragment. These cells were then expanded in a nutrient solution and embedded in a bioink – a gel-like material suitable for 3D bioprinting. The bioink was shaped into ear-like structures and incubated for several weeks to allow maturation, promoting the deposition of type II collagen, elastin, and glycosaminoglycans 3.
Optimizing Cell Growth and Material Properties
According to Dr. Philipp Fisch, a senior researcher in the Tissue Engineering and Biofabrication Group at ETH Zurich and lead author of the study, success depended on optimizing several factors: cell proliferation, material properties, cell density, and the maturation environment 3. The team focused on preventing cartilage cells from behaving like fibroblasts, which produce scar-like tissue, and instead encouraging the development of cartilage rich in type II collagen and elastin.
Looking Ahead
While significant progress has been made, stabilizing elastin remains a critical hurdle. Researchers aim to fully understand the biological “blueprint” for elastin network formation within the next five years 3. Future steps include structured clinical studies and regulatory approval before this technology can be widely implemented in surgical practice. “Our current study provides a good guide to the current state of research. It shows how close we already are to recreate the human ear – and what’s still missing,” said Dr. Fisch 3.