title: Optimizing nutrient channel spacing and revisiting TGF-beta in large engineered cartilage constructs.
abstract: Cartilage tissue engineering is a promising approach to treat osteoarthritis. However, current techniques produce tissues too small for clinical relevance. Increasingly close-packed channels have helped overcome nutrient transport limitations in centimeter-sized chondrocyte-agarose constructs, yet optimal channel spacings to recapitulate native cartilage compositional and mechanical properties in constructs this large have not been identified. Transient active TGF-β treatment consistently reproduces native compressive Young׳s modulus (EY) and glycosaminoglycan (GAG) content in constructs, but standard dosages of 10ng/mL exacerbate matrix heterogeneity. To ultimately produce articular layer-sized constructs, we must first optimize channel spacing and investigate the role of TGF-β in the utility of channels. We cultured ∅10mm constructs with 0, 12, 19, or 27 nutrient channels (∅1mm) for 6-8 weeks with 0, 1, or 10ng/mL TGF-β; subsequently we analyzed them mechanically, biochemically, and histologically. Constructs with 12 or 19 channels grew the most favorably, reaching EY=344±113kPa and GAG and collagen contents of 10.8±1.2% and 2.2±0.2% of construct wet weight, respectively. Constructs with 27 channels had significantly less deposited GAG than other groups. Channeled constructs given 1 or 10ng/mL TGF-β developed similar properties. Without TGF-β, constructs with 0 or 12 channels exhibited properties that were indistinguishable, and lower than TGF-β-supplemented constructs. Taken together, these results emphasize that nutrient channels are effective only in the presence of TGF-β, and indicate that spacings equivalent to 12 channels in ∅10mm constructs can be employed in articular-layer-sized constructs with reduced dosages of TGF-β.
authors.affiliation: Departments of Mechanical Engineering, Biomedical Engineering and Medicine, Columbia University, New York, NY 10027, United States.
authors.forename: Alexander D
authors.initials: AD
authors.lastname: Cigan
authors.affiliation: Departments of Mechanical Engineering, Biomedical Engineering and Medicine, Columbia University, New York, NY 10027, United States.
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Nims
authors.affiliation: Departments of Mechanical Engineering, Biomedical Engineering and Medicine, Columbia University, New York, NY 10027, United States.
authors.forename: Gordana
authors.initials: G
authors.lastname: Vunjak-Novakovic
authors.affiliation: Departments of Mechanical Engineering, Biomedical Engineering and Medicine, Columbia University, New York, NY 10027, United States.
authors.forename: Clark T
authors.initials: CT
authors.lastname: Hung
authors.affiliation: Departments of Mechanical Engineering, Biomedical Engineering and Medicine, Columbia University, New York, NY 10027, United States. Electronic address: ateshian@columbia.edu.
authors.forename: Gerard A
authors.initials: GA
authors.lastname: Ateshian
mesh_terms: D000818:Animals; D002356:Cartilage / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D002417:Cattle; D002478:Cells, Cultured; D019902:Chondrocytes / Q000187:drug effects / Q000502:physiology; D003094:Collagen / Q000378:metabolism; D055119:Elastic Modulus; D006025:Glycosaminoglycans / Q000378:metabolism; D023822:Tissue Engineering / Q000379:methods*; D016212:Transforming Growth Factor beta / Q000494:pharmacology*
chemical_list: D006025:Glycosaminoglycans; D016212:Transforming Growth Factor beta; D003094:Collagen
keywords: Agarose; Cartilage; Chondrocytes; Growth factors; Nutrient transport; Tissue engineering