title: Integrating qPLM and biomechanical test data with an anisotropic fiber distribution model and predictions of TGF-β1 and IGF-1 regulation of articular cartilage fiber modulus.
abstract: A continuum mixture model with distinct collagen (COL) and glycosaminoglycan elastic constituents was developed for the solid matrix of immature bovine articular cartilage. A continuous COL fiber volume fraction distribution function and a true COL fiber elastic modulus ([Formula: see text] were used. Quantitative polarized light microscopy (qPLM) methods were developed to account for the relatively high cell density of immature articular cartilage and used with a novel algorithm that constructs a 3D distribution function from 2D qPLM data. For specimens untreated and cultured in vitro, most model parameters were specified from qPLM analysis and biochemical assay results; consequently, [Formula: see text] was predicted using an optimization to measured mechanical properties in uniaxial tension and unconfined compression. Analysis of qPLM data revealed a highly anisotropic fiber distribution, with principal fiber orientation parallel to the surface layer. For untreated samples, predicted [Formula: see text] values were 175 and 422 MPa for superficial (S) and middle (M) zone layers, respectively. TGF-[Formula: see text]1 treatment was predicted to increase and decrease [Formula: see text] values for the S and M layers to 281 and 309 MPa, respectively. IGF-1 treatment was predicted to decrease [Formula: see text] values for the S and M layers to 22 and 26 MPa, respectively. A novel finding was that distinct native depth-dependent fiber modulus properties were modulated to nearly homogeneous values by TGF-[Formula: see text]1 and IGF-1 treatments, with modulated values strongly dependent on treatment.
authors.affiliation: Mechanical Engineering Department, California Polytechnic State University, San Luis Obispo, CA, USA.
authors.forename: Michael E
authors.initials: ME
authors.lastname: Stender
authors.forename: Christopher B
authors.initials: CB
authors.lastname: Raub
authors.forename: Kevin A
authors.initials: KA
authors.lastname: Yamauchi
authors.forename: Reza
authors.initials: R
authors.lastname: Shirazi
authors.forename: Pasquale
authors.initials: P
authors.lastname: Vena
authors.forename: Robert L
authors.initials: RL
authors.lastname: Sah
authors.forename: Scott J
authors.initials: SJ
authors.lastname: Hazelwood
authors.forename: Stephen M
authors.initials: SM
authors.lastname: Klisch
mesh_terms: D000818:Animals; D016880:Anisotropy; D001696:Biomechanical Phenomena / Q000187:drug effects; D002358:Cartilage, Articular / Q000187:drug effects / Q000502:physiology*; D002417:Cattle; D055119:Elastic Modulus / Q000187:drug effects*; D024022:Fibrillar Collagens / Q000378:metabolism*; D006025:Glycosaminoglycans / Q000378:metabolism; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D008859:Microscopy, Polarization / Q000379:methods*; D008954:Models, Biological; D053773:Transforming Growth Factor beta1 / Q000494:pharmacology*
chemical_list: D024022:Fibrillar Collagens; D006025:Glycosaminoglycans; D053773:Transforming Growth Factor beta1; D007334:Insulin-Like Growth Factor I