Pore architecture effects on chondrogenic potential of patient-specific 3-dimensionally printed porous tissue bioscaffolds for auricular tissue engineering

Objective This study aims to determine the effect of auricular scaffold microarchitecture on chondrogenic potential in an in vivo animal model. Methods DICOM computed tomography (CT) images of a human auricle were segmented to create an external anatomic envelope. Image-based design was used to generate 1) orthogonally interconnected spherical pores and 2) randomly interspersed pores, and each were repeated in three dimensions to fill the external auricular envelope. These auricular scaffolds were then 3D printed by laser sintering poly- l -caprolactone, seeded with primary porcine auricular chondrocytes in a hyaluronic acid/collagen hydrogel and cultured in a pro-chondrogenic medium. The auricular scaffolds were then implanted subcutaneously in rats and explanted after 4 weeks for analysis with Safranin O and Hematoxylin and Eosin staining. Results Auricular constructs with two micropore architectures were rapidly manufactured with high fidelity anatomic appearance. Subcutaneous implantation of the scaffolds resulted in excellent external appearance of both anterior and posterior auricular surfaces. Analysis on explantation showed that the defined, spherical micropore architecture yielded histologic evidence of more robust chondrogenic tissue formation as demonstrated by Safranin O and Hematoxylin and Eosin staining. Conclusions Image-based computer-aided design and 3D printing offers an exciting new avenue for the tissue-engineered auricle. In early pilot work, creation of spherical micropores within the scaffold architecture appears to impart greater chondrogenicity of the bioscaffold. This advantage could be related to differences in permeability allowing greater cell migration and nutrient flow, differences in surface area allowing different cell aggregation, or a combination of both factors. The ability to design an anatomically correct scaffold that maintains its structural integrity while also promoting auricular cartilage growth represents an important step towards clinical applicability of this new technology.