Tissue engineering and 3D printer replicate adult human ear

The study, carried out by researchers from Weill Cornell Medicine and Cornell Engineering and published online in Acta Biomaterialia , offers the promise of grafts with well-defined anatomy and the correct biomechanical properties for those who are born with a congenital malformation or who lose an ear later in life.

“Ear reconstruction requires multiple surgeries and an incredible amount of artistry and finesse,” said, Dr. Jason Spector, chief of the Division of Plastic and Reconstructive Surgery at  NewYork-Presbyterian/Weill Cornell Medical Center and a professor of surgery (plastic surgery) at Weill Cornell Medicine. “This new technology may eventually provide an option that feels real for thousands needing surgery to correct outer ear deformities.”

Surgeons can build a replacement ear using cartilage removed from a child’s ribs, but the resulting graft generally does not have the same flexibility.

Chondrocytes, the cells that build cartilage, can help produce a more natural replacement ear. In earlier studies, Dr. Spector and his colleagues used animal-derived chondrocytes to seed a scaffold made of collagen, a key component of cartilage.

These grafts developed successfully at first, but over time the well-defined topography of the ear was lost.

“Because the cells tug on the woven matrix of proteins as they labour, the ear contracted and shrank by half,” Dr. Spector said in a statement.

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To address this problem, Dr. Spector and his team used sterilised animal-derived cartilage treated to remove anything that could trigger immune rejection. This was loaded into intricate, ear-shaped plastic scaffolds that were created on a 3D printer based on data from a person’s ear. The small pieces of cartilage act as internal reinforcements to induce new tissue formation within the scaffold.

Over the next three to six months, the structure developed into cartilage containing tissue that closely replicated the ear’s anatomical features, including the helical rim, the ‘anti-helix’ rim-inside-the-rim and the central, conchal bowl. “That’s something that we had not achieved before,” said Dr. Spector.

To test the feel of the ear, biomechanical studies were performed in conjunction with Dr. Spector's colleague Dr. Larry Bonassar, the Daljit S. and Elaine Sarkaria Professor in Biomedical Engineering at the Meinig School of Biomedical Engineering on Cornell’s Ithaca campus in New York. This confirmed that the replicas had flexibility and elasticity similar to human ear cartilage. However, the engineered material was not as strong as natural cartilage and could tear.

To remedy this issue, Dr. Spector plans to add chondrocytes to the mix, ideally ones derived from a small piece of cartilage removed from the recipient’s other ear. Those cells would lay down the elastic proteins that make ear cartilage so robust, producing a graft that would be biomechanically much more like the native ear, he said.