title: Scaffold-free cartilage subjected to frictional shear stress demonstrates damage by cracking and surface peeling.
abstract: Scaffold-free engineered cartilage is being explored as a treatment for osteoarthritis. In this study, frictional shear stress was applied to determine the friction and damage behaviour of scaffold-free engineered cartilage, and tissue composition was investigated as it related to damage. Scaffold-free engineered cartilage frictional shear stress was found to exhibit a time-varying response similar to that of native cartilage. However, damage occurred that was not seen in native cartilage, manifesting primarily as tearing through the central plane of the constructs. In engineered cartilage, cells occupied a significantly larger portion of the tissue in the central region where damage was most prominent (18 ± 3% of tissue was comprised of cells in the central region vs 5 ± 1% in the peripheral region; p < 0.0001). In native cartilage, cells comprised 1-4% of tissue for all regions. Average bulk cellularity of engineered cartilage was also greater (68 × 103± 4 × 103vs 52 × 103± 22 × 103cells/mg), although this difference was not significant. Bulk tissue comparisons showed significant differences between engineered and native cartilage in hydroxyproline content (8 ± 2 vs 45 ± 3 µg HYP/mg dry weight), solid content (12.5 ± 0.4% vs 17.9 ± 1.2%), shear modulus (0.06 ± 0.02 vs 0.15 ± 0.07 MPa) and aggregate modulus (0.12 ± 0.03 vs 0.32 ± 0.14 MPa), respectively. These data indicate that enhanced collagen content and more uniform extracellular matrix distribution are necessary to reduce damage susceptibility. Copyright © 2014 John Wiley & Sons, Ltd.
authors: Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, USA.|Matrix Biology Program, Benaroya Research Institute, Seattle, WA, USA.
authors: G Adam
authors: GA
authors: Whitney
authors: Department of Mechanical and Aerospace Engineering, Case Western Reserve University, Cleveland, OH, USA.
authors: Karthik
authors: K
authors: Jayaraman
authors: Department of Biomedical Engineering, Case Western Reserve University, Cleveland, OH, USA.|Department of Orthopaedics, Case Western Reserve University, Cleveland, OH, USA.|Matrix Biology Program, Benaroya Research Institute, Seattle, WA, USA.
authors: James E
authors: JE
authors: Dennis
authors: Department of Orthopaedics, Case Western Reserve University, Cleveland, OH, USA.|Department of Mechanical and Aerospace Engineering, Case Western Reserve University, Cleveland, OH, USA.
authors: Joseph M
authors: JM
authors: Mansour
mesh_terms: D000818:Animals; D019149:Bioreactors; D002358:Cartilage, Articular / Q000473:pathology*; D002478:Cells, Cultured; D019902:Chondrocytes / Q000166:cytology; D003094:Collagen / Q000737:chemistry; D005109:Extracellular Matrix / Q000737:chemistry; D017276:Friction; D006909:Hydroxyproline / Q000737:chemistry; D010003:Osteoarthritis / Q000628:therapy*; D011312:Pressure; D011817:Rabbits; D013314:Stress, Mechanical; D013499:Surface Properties; D023822:Tissue Engineering / Q000379:methods*
chemical_list: D003094:Collagen; D006909:Hydroxyproline
keywords: damage; depth-dependent cellularity; frictional shear; mechanical properties; scaffold-free engineered cartilage composition; tribology