Tissue engineering offers new possibilities for patients with congenital deformities. In 2017, Chinese scientists pioneered a novel approach to reconstruct external ears for children born with microtia. This research combined advanced three-dimensional (3D) printing technology with autologous, or patient-derived, cells. This methodology provided a blueprint for growing living, personalized cartilage that could be surgically implanted.
Addressing Microtia and Collecting Chondrocytes
The procedure addresses microtia, a birth defect where the external ear (pinna) is underdeveloped or missing. This deformity impacts a child’s appearance and can affect their psychological well-being. Traditional treatments often involve complex procedures, such as sculpting a replacement ear from the patient’s rib cartilage, which creates a separate injury site.
The first step involved obtaining biological starting material from the patient to prevent immune rejection. Researchers harvested a small sample of cartilage cells, known as chondrocytes, from the patient’s existing microtic ear tissue. These specialized cells produce and maintain cartilage. Isolating the patient’s own cells (autologous transplantation) eliminates the need for immunosuppressive drugs and minimizes the risk of the body attacking the new tissue.
Engineering the Biodegradable Scaffold
Before tissue growth, scientists created a perfectly shaped structural template for the new ear. If the condition affected only one ear, the healthy ear was scanned using computed tomography (CT) to create a precise digital model. This blueprint was symmetrically mirrored so the new ear would match the unaffected side. The resulting digital file guided a 3D printing process to manufacture the structural framework, or scaffold.
The scaffold was engineered to be strong and biodegradable, providing temporary mechanical support while the new tissue formed. The core structure used polycaprolactone (PCL), a synthetic polymer that dissolves slowly over up to four years. This PCL mesh was reinforced and coated with layers of Polyglycolic acid (PGA) fibers and Polylactic acid (PLA). These materials acted as a temporary skeleton, maintaining the ear’s complex contours until the patient’s cells replaced the framework with natural cartilage.
Culturing the Cartilage Tissue
Once harvested, the cells were expanded and multiplied in a laboratory environment. This expansion ensures enough healthy chondrocytes are available to populate the entire scaffold. Next, the concentrated chondrocytes were carefully “seeded” onto the 3D-printed biodegradable scaffold. The cells were placed onto the outer PGA/PLA layer, which encourages cell attachment and growth.
The cell-seeded scaffold was placed into a specialized incubator, known as a bioreactor, and cultured for approximately 12 weeks. Inside the bioreactor, the environment was controlled to mimic the body’s natural conditions, providing necessary nutrients and growth factors. During this in vitro phase, the chondrocytes proliferated and secreted their own extracellular matrix, the material that makes up natural cartilage. This activity allowed the cells to gradually replace the temporary scaffold with living, functional cartilage that assumed the ear’s precise shape.
Surgical Placement and Patient Outcomes
After the twelve-week cultivation period, the bioengineered ear, consisting of a cartilage framework populated with the patient’s own cells, was ready for implantation. The final phase involved surgically placing the structure under the skin where the ear was missing. During the operation, the surrounding skin was draped over the engineered cartilage, using vacuum drainage to ensure the skin adhered closely to the intricate contours of the new ear.
Following surgery, patients were monitored for up to two and a half years to track the implant’s long-term fate. The engineered ears demonstrated excellent cartilage formation and maintained their shape and structure over time. As the PCL and other polymers degraded, the patient’s chondrocytes continued to produce new, natural elastic cartilage, gradually replacing the temporary synthetic framework. While some initial patients required minor cosmetic adjustments, the successful integration and growth of the bioengineered ears represented a step toward making this tissue engineering approach a clinical reality.