Structural and Mechanical Comparison of Human Ear, Alar, and Septal Cartilage

Background: In the human ear and nose, cartilage plays a key role in establishing its form and function. Interestingly, there is a noticeable paucity on biochemical, structural, and mechanical studies focused on facial cartilage. Such studies are needed to provide elementary knowledge that is fundamental to tissue engineering of cartilage. Therefore, in this study, a comparison is made of the biochemical, structural, and mechanical differences between ear, ala nasi, and septum on the extracellular matrix (ECM) level. Methods: Cartilage samples were harvested from 10 cadaveric donors. Each sample was indented 10 times with a nanoindenter to determine the effective Young's modulus. Structural information of the cartilage was obtained by multiple-photon laser scanning microscopy capable of revealing matrix components at subcellular resolution. Biochemistry was performed to measure glycosaminoglycan (GAG), DNA, elastin, and collagen content. Results: Significant differences were seen in stiffness between ear and septal cartilage (P = 0.011) and between ala nasi and septal cartilage (P = 0.005). Elastin content was significantly higher in ear cartilage. Per cartilage subtype, effective Young's modulus was not significantly correlated with cell density, GAG, or collagen content. However, in septal cartilage, low elastin content was associated with higher stiffness. Laser microscopy showed a distinct difference between ear cartilage and cartilage of nasal origin. Conclusion: Proposed methods to investigate cartilage on the ECM level provided good results. Significant differences were seen not only between ear and nasal cartilage but also between the ala nasi and septal cartilage. Albeit its structural similarity to septal cartilage, the ala nasi has a matrix stiffness comparable to ear cartilage. This is an open-access article distributed under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives License 4.0 (CCBY-NC-ND), where it is permissible to download and share the work provided it is properly cited. The work cannot be changed in any way or used commercially without permission from the journal. Published online 18 January 2018. Received for publication May 21, 2017; accepted October 25, 2017. Disclosure: The research by Mieke Pluemeekers was financially supported by SenterNovem in the framework of EuroNanoMed (EAREG-406340-131009/1). The research of Ernst Jan Bos was supported by the Dutch Burns Foundation. Neither of the other authors has any financial disclosures. The Article Processing Charge was paid for by the authors. Supplemental digital content is available for this article. Clickable URL citations appear in the text. Paul van Zuijlen, MD, PhD, Burn Center Department, Red Cross Hospital, Vondellaan 13, Beverwijk 1942 LE, The Netherlands, E-mail: p.vanzuijlen@vumc.nl Copyright © 2018 The Authors. Published by Wolters Kluwer Health, Inc. on behalf of the American Society of Plastic Surgeons. All rights reserved.

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