Successful Creation of Tissue-Engineered Autologous Auricular Cartilage in an Immunocompetent Large Animal Model

Abstract

Tissue-engineered cartilage has historically been an attractive alternative treatment option for auricular reconstruction. However, the ability to reliably generate autologous auricular neocartilage in an immunocompetent preclinical model should first be established. The objectives of this study were to demonstrate engineered autologous auricular cartilage in the immunologically aggressive subcutaneous environment of an immunocompetent animal model, and to determine the impact of in vitro culture duration of chondrocyte-seeded constructs on the quality of neocartilage maturation in vivo. Auricular cartilage was harvested from eight adult sheep; chondrocytes were isolated, expanded in vitro, and seeded onto fibrous collagen scaffolds. Constructs were cultured in vitro for 2, 6, and 12 weeks, and then implanted autologously in sheep and in control nude mice for 6 and 12 weeks. Explanted tissue was stained with hematoxylin and eosin, safranin O, toluidine blue, collagen type II, and elastin. DNA and glycosaminoglycans (GAGs) were quantified. The quality of cartilage engineered in sheep decreased with prolonged in vitro culture time. Superior cartilage formation was demonstrated after 2 weeks of in vitro culture; the neocartilage quality improved with increased implantation time. In nude mice, neocartilage resembled native sheep auricular cartilage regardless of the in vitro culture length, with the exception of elastin expression. The DNA quantification was similar in all engineered and native cartilage (p>0.1). All cartilage engineered in sheep had significantly less GAG than native cartilage (p<0.02); significantly more GAG was observed with increased implantation time (p<0.02). In mice, the GAG content was similar to that of native cartilage and became significantly higher with increased in vitro or in vivo durations (p<0.02). Autologous auricular cartilage was successfully engineered in the subcutaneous environment of an ovine model using expanded chondrocytes seeded on a fibrous collagen scaffold after a 2-week in vitro culture period.

MR elastography for evaluating regeneration of tissue‐engineered cartilage in an ectopic mouse model

“…This increase in shear stiffness of the constructs can be due to formation of their net-like organized structure of the collagen type I and II fibers and increasing concentration of proteoglycans (45). In agreement with previous reports (9,46,47), the current results demonstrated that the expression of collagen II and Agg were up-regulated within silk, collagen, and gelatin scaffold after 8 wk implantation, compared with in vitro culture (Fig. 5).…”

Chondrogenesis by bone marrow‐derived mesenchymal stem cells grown in chondrocyte‐conditioned medium for auricular reconstruction

“…However, the samples exposed to standard medium contained very little type II collagen. Elastin fibres were present in both CCM groups at 12 weeks, albeit the elastin in the tissue‐engineered cartilage was still less dense than that observed in native auricular cartilage (Bichara et al , ). Considering the importance of elastin in native ear cartilage, the results above are very meaningful for the potential to engineer auricular cartilage.…”

“…A number of studies have demonstrated proof of principle for generating auricular cartilage using primary auricular chondrocytes and various scaffold materials (Xu et al , ; Bichara et al , ; Zhao et al , ). Some studies have extended these strategies by forming the auricular cartilage into the shape of the external ear (Cao et al , ; Zhou et al , ; Zhang et al , ; Otto et al , ).…”

Bone Marrow Mesenchymal Stem Cell-Based Engineered Cartilage Ameliorates Polyglycolic Acid/Polylactic Acid Scaffold-Induced Inflammation Through M2 Polarization of Macrophages in a Pig Model

“…Recent studies have indicated that the inflammatory response is primarily induced by biomaterials and/or their degradation products, regardless of whether they are biologically or artificially synthesized scaffolds [3, 4, 6]. Although collagen‐based cartilage was successfully engineered in the subcutaneous environment of an ovine model [7], it was suggested that the collagen was not adapted to engineering cartilage with specific shape and firmness because of its fast degradation. Polymer scaffolds, exhibiting predictable and reproducible mechanical and physical properties such as elastic modulus and degradation rate [8, 9], have drawn great attention in cartilage engineering.…”