Biofabrication of a shape-stable auricular structure for the reconstruction of ear deformities I.A. Otto a, b, c , P.E. Capendale a, c , J.P. Garcia a, c , M. de Ruijter a, c , R.F.M. van Doremalen d, e , M. Castilho a, c , T. Lawson f , M.W. Grinstaff f , C.C. Breugem g , M. Kon b , R. Levato a, c , J. Malda a, c, h, * a Department of Orthopaedics, University Medical Center Utrecht, Heidelberglaan 100, Utrecht, 3584 CX, the Netherlands b Department of Plastic, Reconstructive and Hand Surgery, University Medical Center Utrecht, Utrecht, the Netherlands c Regenerative Medicine Center Utrecht, Utrecht, the Netherlands d Robotics and Mechatronics, Faculty of Electrical Engineering, Mathematics & Computer Science, University of Twente, Enschede, the Netherlands e Bureau Science & Innovation, Deventer Hospital, Deventer, the Netherlands f Departments of Chemistry and Biomedical Engineering, Boston University, Boston, USA g Department of Plastic, Reconstructive and Hand Surgery, Amsterdam University Medical Center, Emma Children's Hospital, Amsterdam, the Netherlands h Department of Clinical Sciences, Faculty of Veterinary Science, Utrecht University, the Netherlands ARTICLE INFO Keywords: Bioprinting Auricular cartilage Mechanical reinforcement Shape preservation Cartilage progenitor cells ABSTRACT Bioengineering of the human auricle remains a significant challenge, where the complex and unique shape, the generation of high-quality neocartilage, and shape preservation are key factors. Future regenerative medi- cine–based approaches for auricular cartilage reconstruction will benefit from a smart combination of various strategies. Our approach to fabrication of an ear-shaped construct uses hybrid bioprinting techniques, a recently identified progenitor cell population, previously validated biomaterials, and a smart scaffold design. Specifically, we generated a 3D-printed polycaprolactone (PCL) scaffold via fused deposition modeling, photocrosslinked a human auricular cartilage progenitor cell–laden gelatin methacryloyl (gelMA) hydrogel within the scaffold, and cultured the bioengineered structure in vitro in chondrogenic media for 30 days. Our results show that the fabrication process maintains the viability and chondrogenic phenotype of the cells, that the compressive prop- erties of the combined PCL and gelMA hybrid auricular constructs are similar to native auricular cartilage, and that biofabricated hybrid auricular structures exhibit excellent shape fidelity compared with the 3D digital model along with deposition of cartilage-like matrix in both peripheral and central areas of the auricular structure. Our strategy affords an anatomically enhanced auricular structure with appropriate mechanical properties, ensures adequate preservation of the auricular shape during a dynamic in vitro culture period, and enables chon- drogenically potent progenitor cells to produce abundant cartilage-like matrix throughout the auricular construct. The combination of smart scaffold design with 3D bioprinting and cartilage progenitor cells holds promise for the development of clinically translatable regenerative medicine strategies for auricular reconstruction. 1. Introduction Regenerative medicine (RM) is a promising strategy for future treat- ment of auricular cartilage defects and congenital malformations [1–3]. It typically applies a combination of cells, materials and bioactive factors to engineer a new tissue or stimulate the regeneration of native tissue [4]. As current surgical strategies for auricular reconstruction use autologous costal cartilage for shaping the implant framework [5–9], the generation of neocartilage in the laboratory would obviate the need for a large harvest site and thus reduce associated morbidity [1–3,10,11]. In addi- tion, RM techniques have the potential to further mimic the structural and functional complexity of native tissue [3,12]. Compared to the rigid costal cartilage framework [2,3] or the synthetic alternative porous polyethylene [13], the engineered auricular implant should ideally exhibit biochemical and mechanical properties that are more similar to the native elastic cartilage [3,14]. The first clinical trial with tissue-engineered ear-shaped constructs implanted in five children pre- sents encouraging preliminary outcomes [15]. * Corresponding author. E-mail address: j.malda@umcutrecht.nl (J. Malda). Contents lists available at ScienceDirect Materials Today Bio journal homepage: www.journals.elsevier.com/materials-today-bio https://doi.org/10.1016/j.mtbio.2021.100094 Received 28 June 2020; Received in revised form 4 January 2021; Accepted 8 January 2021 Available online 21 January 2021 2590-0064/© 2021 The Author(s). Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). Materials Today Bio 9 (2021) 100094