Efficient engineering of human auricular cartilage through mesenchymal stem cell chaperoning.

A major challenge to the clinical translation of tissue-engineered ear scaffolds for ear reconstruction is the limited auricular chondrocyte (hAuC) yield available from patients. Starting with a relatively small number of chondrocytes in culture results in dedifferentiation and loss of phenotype with subsequent expansion. To significantly decrease the number of chondrocytes required for human elastic cartilage engineering, we co-cultured human mesenchymal stem cells (hMSCs) with HAuCs to promote healthy elastic cartilage formation. HAuCs along with human bone marrow-derived hMSCs were encapsulated into 1% Type I collagen at 25 million/mL total cell density with different ratios (HAuCs/hMSCs: 10/90, 25/75, 50/50) and then injected into customized 3D-printed polylactic acid (PLA) ridged external scaffolds, which simulate the shape of the auricular helical rim, and implanted subcutaneously in nude rats for 1, 3 and 6 months. The explanted constructs demonstrated near complete volume preservation and topography maintenance of the ridged "helical" feature after 6 months with all ratios. Cartilaginous appearing tissue formed within scaffolds by 3 months, verified by histologic analysis demonstrating mature elastic cartilage within the constructs with chondrocytes seen in lacunae within a Type II collagen and proteoglycan-enriched matrix, and surrounded by a neoperichondrial external layer. Compressive mechanical properties comparable to human elastic cartilage were achieved after 6 months. Co-implantation of hAuCs and hMSCs in collagen within an external scaffold efficiently produced shaped human elastic cartilage without volume loss even when hAuC comprised only 10% of the implanted cell population, marking a crucial step toward the clinical translation of auricular tissue engineering.

Three-Dimensional-Printed External Scaffolds Mitigate Loss of Volume and Topography in Engineered Elastic Cartilage Constructs.

OBJECTIVE: A major obstacle in the clinical translation of engineered auricular scaffolds is the significant contraction and loss of topography that occur during maturation of the soft collagen-chondrocyte matrix into elastic cartilage. We hypothesized that 3-dimensional-printed, biocompatible scaffolds would "protect" maturing hydrogel constructs from contraction and loss of topography. DESIGN: External disc-shaped and "ridged" scaffolds were designed and 3D-printed using polylactic acid (PLA). Acellular type I collagen constructs were cultured in vitro for up to 3 months. Collagen constructs seeded with bovine auricular chondrocytes (BAuCs) were prepared in 3 groups and implanted subcutaneously in vivo for 3 months: preformed discs with ("Scaffolded/S") or without ("Naked/N") an external scaffold and discs that were formed within an external scaffold via injection molding ("Injection Molded/SInj"). RESULTS: The presence of an external scaffold or use of injection molding methodology did not affect the acellular construct volume or base area loss. In vivo, the presence of an external scaffold significantly improved preservation of volume and base area at 3 months compared to the naked group (P < 0.05). Construct contraction was mitigated even further in the injection molded group, and topography of the ridged constructs was maintained with greater fidelity (P < 0.05). Histology verified the development of mature auricular cartilage in the constructs within external scaffolds after 3 months. CONCLUSION: Custom-designed, 3D-printed, biocompatible external scaffolds significantly mitigate BAuC-seeded construct contraction and maintain complex topography. Further refinement and scaling of this approach in conjunction with construct fabrication utilizing injection molding may aid in the development of full-scale auricular scaffolds.

The application of wrapping ureter by a pedicled gastrocolic omentum flap combined with an artificial external scaffold to prevent stoma stenosis in rabbit after ureterocutaneostomy.

OBJECTIVE: To evaluate the feasibility and possibility of wrapping ureter by a pedicled gastrocolic omentum flap combined with an artificial ureter external scaffold to prevent stoma stenosis in rabbit after ureterocutaneostomy. METHODS: Forty male New Zealand rabbits were involved in this study. For application of ureterocutaneostomy, the right ureter was wrapped by a pedicled gastrocolic omentum flap and combined with application of an artificial external scaffold, which served as experimental side. Traditional ureterocutaneostomy was applied in left ureter (control side). All rabbits were killed after 1 month, and the kidney, ureter and abdominal segment ureter were collected to study the morphological and pathological changes by using HE staining, Masson staining, immunohistochemistry staining and microvessel density (MVD) study. RESULTS: HE staining showed that renal medullary tubular dilatation, large number of collagen deposition, renal glomerular and renal tubular atrophy. Glomerular vascular leaves and interstitial fibrosis were detected in the kidney of control side. However, these abnormities in the kidney of experimental side were significantly alleviated compared to control side. The hydronephrosis and ureterectasia in the experimental side were dramatically attenuated compared to control side. Fibrosis in ureter around stoma and stoma stenosis were prevented by wrapping ureter by a pedicled gastrocolic omentum flap combined with an artificial external scaffold. CONCLUSION: In this study, we have demonstrated that wrapping ureter by a pedicled gastrocolic omentum flap combined with an artificial external scaffold is capable of preventing stoma stenosis in rabbit after ureterocutaneostomy, which provided a new method and theoretical basis for clinical application in the future.