title: Achilles tendons from decorin- and biglycan-null mouse models have inferior mechanical and structural properties predicted by an image-based empirical damage model.
abstract: Achilles tendons are a common source of pain and injury, and their pathology may originate from aberrant structure function relationships. Small leucine rich proteoglycans (SLRPs) influence mechanical and structural properties in a tendon-specific manner. However, their roles in the Achilles tendon have not been defined. The objective of this study was to evaluate the mechanical and structural differences observed in mouse Achilles tendons lacking class I SLRPs; either decorin or biglycan. In addition, empirical modeling techniques based on mechanical and image-based measures were employed. Achilles tendons from decorin-null (Dcn(-/-)) and biglycan-null (Bgn(-/-)) C57BL/6 female mice (N=102) were used. Each tendon underwent a dynamic mechanical testing protocol including simultaneous polarized light image capture to evaluate both structural and mechanical properties of each Achilles tendon. An empirical damage model was adapted for application to genetic variation and for use with image based structural properties to predict tendon dynamic mechanical properties. We found that Achilles tendons lacking decorin and biglycan had inferior mechanical and structural properties that were age dependent; and that simple empirical models, based on previously described damage models, were predictive of Achilles tendon dynamic modulus in both decorin- and biglycan-null mice.
authors.affiliation: McKay Orthopaedic Research Laboratory, University of Pennsylvania, Philadelphia, PA, USA.
authors.forename: J A
authors.initials: JA
authors.lastname: Gordon
authors.affiliation: McKay Orthopaedic Research Laboratory, University of Pennsylvania, Philadelphia, PA, USA.
authors.forename: B R
authors.initials: BR
authors.lastname: Freedman
authors.affiliation: McKay Orthopaedic Research Laboratory, University of Pennsylvania, Philadelphia, PA, USA.
authors.forename: A
authors.initials: A
authors.lastname: Zuskov
authors.affiliation: Department of Pathology, Anatomy and Cell Biology, Thomas Jefferson University, Philadelphia, PA, USA.
authors.forename: R V
authors.initials: RV
authors.lastname: Iozzo
authors.affiliation: Department of Molecular Pharmacology and Physiology, University of South Florida, Tampa, FL, USA.
authors.forename: D E
authors.initials: DE
authors.lastname: Birk
authors.affiliation: McKay Orthopaedic Research Laboratory, University of Pennsylvania, Philadelphia, PA, USA. Electronic address: soslowsk@upenn.edu.
authors.forename: L J
authors.initials: LJ
authors.lastname: Soslowsky
mesh_terms: D000125:Achilles Tendon / Q000737:chemistry / Q000502:physiology*; D000818:Animals; D058578:Biglycan / Q000032:analysis / Q000172:deficiency* / Q000235:genetics; D001696:Biomechanical Phenomena / Q000502:physiology; D003094:Collagen / Q000502:physiology / Q000648:ultrastructure; D058575:Decorin / Q000032:analysis / Q000172:deficiency* / Q000235:genetics; D005260:Female; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D023421:Models, Animal; D008954:Models, Biological; D013314:Stress, Mechanical
chemical_list: D058578:Biglycan; C546879:Dcn protein, mouse; D058575:Decorin; D003094:Collagen
keywords: Collagen; Extracellular; Matrix; Polarized light; Proteoglycan; SLRP; Tendon/ligament mechanics