Fabrication of the First Full-Scale Human Auricular Chondrocyte Derived Ear Scaffold for Clinical Application
Jaime L. Bernstein, BS1, Kerry A. Morrison, BA1, Benjamin P. Cohen, MS2, Alice Harper, BA1, Omer Kaymakcalan, MD1, Lawrence J. Bonassar, PhD2, Jason A. Spector, MD1.
1Weill Cornell Medical College, New York, NY, USA, 2Cornell University, Ithaca, NY, USA.
Purpose: Current autologous reconstructive options for pediatric microtia, as well as other auricular deformities secondary to trauma and oncologic resection, have significant shortcomings including suboptimal aesthetic outcomes and morbidity at the costal cartilage site. Previously, we fabricated high fidelity human-shaped auricular scaffolds using bovine auricular chondrocytes, which have displayed long term stability following implantation as well as structural, mechanical, and biochemical properties indistinguishable from that of native auricular cartilage. However, clinical translation of our ears mandates the use of approximately 250 million human auricular chondrocyte (hAuCs), and unfortunately autologous tissue donation generates a limited cell yield and subsequent passaging for cellular expansion presents the problem of dedifferentiation. We have overcome this challenge by developing a cell sourcing technique that allows the use of 50% fewer hAuCs through augmentation with human mesenchymal stem cells (hMSCs) and aim to use this technique to create the first full scale human ear scaffold.
Methods: 3D photogrammetry combined with computer-assisted design/computer-aided manufacturing techniques were used to convert an image of a normal pediatric ear to a custom 3D printed mold with patient-specific geometry. HAuCs isolated from discarded otoplasty specimens along with hMSCs extracted from human bone marrow were encapsulated in a 1:1 ratio into type I collagen at a density of 25x106 cells/mL. This cell-collagen solution was then injected into the printed pediatric ear mold to generate full-scale ear constructs, which were subsequently implanted subcutaneously in the dorsa of nude rats and harvested after 3 months.
Results: After 3 months of implantation, the full-scale human ear constructs showed a white cartilage-like appearance and maintained major ear topographic regions such as the helical rim and lobule, although some contraction was noted. Ears also demonstrated a flexibility and elastic mechanical response similar to native cartilage on gross inspection. Histologically, they resembled native auricular cartilage with organized perichondrium composed of collagen, a rich proteoglycan matrix, cellular lacunaue, and a dense elastin fiber network by safranin-O and Verhoeff’s stain.
Conclusion: Using our novel cell sourcing technique, co-implantation of hAuCs and hMSCs in collagen full-scale human ear scaffolds produced cartilage that resembled native human auricular cartilage using half the amount of chondrocytes. This allowed us to use a clinically obtainable amount of donor tissue to create a full-scale human auricular chondrocyte ear scaffold that maintained ear morphology and had histologic and elastic mechanical properties indistinguishable from native auricular cartilage. We have fabricated the world’s first full scale, patient specific, high anatomic fidelity human auricular scaffold that shows extreme promise for translation into the clinic.
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