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Turning Microtia On Its Ear: Bioengineering Full-scale Auricles Using 3D-printed External Scaffolds And Decellularized Cartilage Xenograft
Nicholas A. Vernice, A.B.1, Sabrina Shih, B.A.1, Carly Askinas, B.S.1, Xue Dong, M.D, Ph.D.1, George S. Corpuz, B.A., B.S.,1 James Shin, M.D.,2 Jason A. Spector, M.D.1,3
1Division of Plastic and Reconstructive Surgery, Weill Cornell Medicine, New York, NY USA2Department of Radiology, Weill Cornell Medicine, New York, NY USA3Department of Biomedical Engineering, Weill Cornell Medicine, New York, NY USA

Background: Reconstruction of the human auricle is a notorious challenge for the plastic surgeon. Autologous costal cartilage grafts are accompanied by donor site morbidity, and aesthetic outcomes are frequently suboptimal. In response, we have bioengineered neo-ears utilizing decellularized ovine costal cartilage as a biocompatible xenograft placed within a full-scale, 3D-printed human ear scaffold to foster tissue growth that predictably mimics the size, shape, and biomechanical properties of the native human auricle.
Methods and Materials: Polylactic acid (PLA) ear scaffolds were fabricated to match the anatomy of an adult ear using 3D photo capture and subsequent modeling. All scaffolds were printed on a 3D printer (Prusa i3 MK3S) and sterilized. Ovine costal cartilage was isolated and processed either through mincing (1 mm3) or zesting (<2 mm3) and decellularized in-house through our usual protocol. Decellularized cartilage was packed into the ear scaffolds and implanted subcutaneously on the dorsa of immunocompetent rats. After 3 and 6 months in vivo, the constructs were explanted for gross, histologic, biochemical, and biomechanical analyses.
Results: Upon de-molding, both the minced and zested neo-ears maintained the size and contour complexities of the native human ear through 6 months in vivo. Massing of minced and zested ears, respectively, revealed a 1.45 +/- 0.09 fold increase (p=0.05) and 1.11 +/- 0.07 fold increase in construct mass with respect to preimplantation mass after 3 months in vivo. After 6 months in vivo, minced and zested ears experienced a 1.21 +/- 0.18 and 1.35 +/- 0.01 (p<0.01) fold increase in construct mass, respectively. Micro-CT scanning of de-caged auricles confirmed maintenance of explant volume through 6 months in vivo for both minced and zested auricles. H&E staining confirmed a mild inflammatory infiltrate at 3 months that abated by 6 months, replaced by homogenous fibrovascular tissue ingrowth enveloping individual cartilage graft segments. Safranin-O staining revealed an expected depletion of glycosaminoglycans (GAG) secondary to decellularization. All constructs were pliable and resumed their native conformation when twisted or bent and detailed biomechanical studies are ongoing.
Conclusions: Utilization of decellularized ovine xenograft has proven highly efficacious at generating neo-ears that maintain their size and shape after 6 months in vivo. Multiple ears fabricated using the same in vivo bioreactor approach will be explanted over the ensuing several months to provide further insight into construct longevity.


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