There is a widespread belief that we are on the verge of 3D printing functional organs, but the reality in the lab is far more complex. Although that goal remains distant, a team of researchers at ETH Zurich has reached a milestone that brings it closer. They successfully created elastic, stable ear cartilage from human cells grown in the lab. Led by researcher Philipp Fisch and Professor Marcy Zenobi-Wong, the team developed a 3D-printed artificial ear that retained its shape and mechanical properties after implantation in animal models, bringing personalized solutions for patients with severe malformations or injuries one step closer.
The main objective of this research is to overcome the limitations of current reconstruction methods. Today, the standard treatment for ear malformations or ear loss caused by accidents involves harvesting cartilage from the patient’s own ribs to sculpt a new ear. In addition to being painful, this method often results in an ear that is stiffer than a natural one. For this reason, scientists are working to create a tissue that offers the necessary stability and flexibility before being implanted in the human body.
Schematic overview of the ear cartilage manufacturing process (credits: P. Fisch, S. Kessler, S. Ponta, et al.).
To obtain the necessary biological material, the researchers extracted cells from small cartilage fragments left over from previous surgeries performed on other patients. From a tiny sample measuring just three millimeters, they initially isolated about 100,000 cells, which they then grew in a special nutrient solution until reaching the hundreds of millions needed to create a complete ear. During this cultivation process, the team optimized the environment to ensure that the cells produced type II collagen and elastin, both characteristic of ear cartilage, rather than turning into fibroblasts, which would produce much softer scar tissue.
The expanded cells are then mixed with a “bio-ink,” a gelatinous material that serves as a support matrix, and fed into a 3D printer that shapes the ear structure. Once printed, the ear is not implanted immediately. The resulting tissue is initially very soft and requires a maturation period of several weeks in an incubator. During this time, the structure receives a constant supply of oxygen and nutrients to encourage the development of a strong network of proteins and sugars that gives it its final strength.
The research results have been promising. After nine weeks of maturation in the lab and an additional six weeks implanted under the skin of rats, the artificial ears retained their shape and exhibited mechanical properties very similar to those of natural human cartilage. Philipp Fisch emphasized that the combination of high cell density and a controlled maturation environment was key to this success. However, he also cautioned that these processes are highly complex: “We’ve been working on this problem in our group for more than ten years. When it comes to tissue biofabrication, or tissue engineering as it is also known, rapid progress is rare.”
Looking ahead, the next steps in the research will focus on refining the elastin network, the protein responsible for the ear’s flexibility, which still poses a biological challenge in terms of long-term stabilization. Fisch estimates that it could take another five years to decode the ideal biological blueprint before moving on to clinical trials. You can read the official press release here.
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*Cover Photo Credit: Philipp Fisch / ETH Zurich