title: Osmotic loading of articular cartilage modulates cell deformations along primary collagen fibril directions.
abstract: Osmotic loading is known to modulate chondrocyte (cell) height, width and volume in articular cartilage. It is not known how cartilage architecture, especially the collagen fibril orientation, affects cell shape changes as a result of an osmotic challenge. Intact patellae of New Zealand white rabbits (n=6) were prepared for fluorescence imaging. Patellae were exposed to a hypotonic osmotic shock and cells were imaged before loading and 5-60 min after the osmotic challenge. Cell volumes and aspect ratios (height/width) were analyzed. A fibril-reinforced poroelastic swelling model with realistic primary collagen fibril orientations, i.e. horizontal, random and vertical orientation in the superficial, middle and deep zones, respectively and cells in different zones was used to estimate cell aspect ratios theoretically. As the medium osmolarity was reduced, cell aspect ratios decreased and volumes increased in the superficial zone of cartilage both experimentally (p<0.05) and theoretically. Theoretically determined aspect ratios of middle zone cells remained virtually constant, while they increased for deep zone cells as osmolarity was reduced. Findings of this study suggest that osmotic loading modulates chondrocyte shapes in accordance with the primary collagen fibril directions in articular cartilage.
authors.affiliation: Department of Physics, University of Kuopio, POB 1627, FI-70211 Kuopio, Finland. rami.korhonen@uku.fi
authors.forename: Rami K
authors.initials: RK
authors.lastname: Korhonen
authors.forename: Sang-Kuy
authors.initials: SK
authors.lastname: Han
authors.forename: Walter
authors.initials: W
authors.lastname: Herzog
mesh_terms: D000818:Animals; D016880:Anisotropy; D002358:Cartilage, Articular / Q000166:cytology* / Q000502:physiology*; D048429:Cell Size; D002478:Cells, Cultured; D019902:Chondrocytes / Q000502:physiology*; D003198:Computer Simulation; D055119:Elastic Modulus / Q000502:physiology; D024022:Fibrillar Collagens / Q000502:physiology* / Q000648:ultrastructure; D040542:Mechanotransduction, Cellular / Q000502:physiology*; D008954:Models, Biological; D009997:Osmotic Pressure; D011817:Rabbits
chemical_list: D024022:Fibrillar Collagens