Improving Efficiency of Human Elastic Cartilage Tissue Engineering Using Mesenchymal Stem Cell Chaperones
Xue Dong, Jason Harris, Sarah Caughey, Ryan Bender, Jason A. Spector
Laboratory of Bioregenerative Medicine & Surgery, Department of Surgery, Division of Plastic Surgery, Weill Cornell Medical College, New York, NY
Introduction: Current options for autologous reconstruction of pediatric microtia and other auricular deformities have significant shortcomings because of suboptimal aesthetic outcomes and morbidity at the costal cartilage donor site. However, clinical translation of a tissue-engineered full-scale ear mandates the use of at least 250 million human auricular chondrocyte (hAuCs), and unfortunately autologous tissue donation generates a limited auricular cell yield and subsequent cellular expansion is plagued by chondrocyte dedifferentiation. Hence, we hypothesized that co-culture of human mesenchymal stem cells (hMSCs), which hold a chondrogenic potential, with HAuCs, would promote healthy human elastic cartilage formation while maintaining the complex tomography of pre-designed constructs overtime.
Methods: In order to simulate the shape of the auricular helical rim, an external “ridged” scaffold was designed, optimized for 3D-printing with a Makerbot Replicator 5th Generation and printed using polylactic acid (PLA). HAuCs isolated from discarded otoplasty specimens along with human bone marrow-derived hMSCs were encapsulated into 1% type I collagen at 25 million/mL total cell density using different mixture ratios (HAuCs/hMSCs: 10/90, 25/75, 50/50). This cell-loaded collagen matrix was then injected into 3D-printed ridged external scaffolds, cross linked in situ and implanted subcutaneously in vivo. Samples were explanted after 1, 3 and 6 months.
Results: With the presence of an external scaffold, the constructs demonstrated a near complete volume preservation after 6 months at 10/90, 25/75 and 50/50 cell mixture ratios (10/90: 102.43±7.39%, 25/75: 90.14±10.69%, 50/50: 90.15±12.45%, respectively). After 3 and 6 months in vivo, a white cartilage-like appearance of the tissue formed within cages and preservation of topography of the ridged “helical” feature was observed with all the different mixture ratios. Histological analysis verified the development of mature elastic cartilage within the constructs after 6 months with chondrocytes seen in lacunae within a Type II collagen-enriched matrix, rich with proteoglycans, and surrounded by a neoperichondrial external layer.
Conclusion: Co-implantation of hAuCs and hMSCs in collagen within an external scaffold efficiently produced shaped human elastic cartilage even when hAuC comprised less than half of the implanted cell population, marking a crucial step towards the clinical translation of auricular tissue engineering. It is unclear if this efficient cartilage formation is the result of differentiation of MSC towards a chondrogenic lineage, a chaperone effect of the MSC, or some combination of both remains unknown, and is the subject of ongoing investigation.
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