title: Effects of increased muscle mass on mouse sagittal suture morphology and mechanics.
abstract: The purpose of this study is to test predicted form-function relationships between cranial suture complexity and masticatory muscle mass and biomechanics in a mouse model. Specifically, to test the hypothesis that increased masticatory muscle mass increases sagittal suture complexity, we measured the fractal dimension (FD), temporalis mass, and temporalis bite force in myostatin-deficient (GDF8(-/-)) mice and wild-type CD-1 mice (all male, 6 months old). Myostatin is a negative regulator of muscle mass, and myostatin-deficient mice show a marked increase in muscle mass compared to normal mice. We predicted that increased sagittal suture complexity would decrease suture stiffness. The data presented here demonstrate that increased suture complexity (measured as FD) was observed in a hypermuscular mouse model (GDF8(-/-)) with significantly increased temporalis muscle mass and bite forces. Hypermuscular mice were also found to possess suture connective tissue that was less stiff (i.e., underwent more displacement before failure occurred) when loaded in tension. By decreasing stiffness, suture complexity apparently helps to dissipate mechanical loads within the cranium that are related to chewing. These results suggest that cranial suture connective tissue locally adapts to functional demands of the biomechanical suture environment. As such, cranial sutures provide a novel model for studies in connective tissue mechanotransduction.
authors.affiliation: Department of Cellular Biology and Anatomy, Medical College of Georgia, Augusta, Georgia 30912-2000, USA. cbyrongs@students.mcg.edu
authors.forename: Craig D
authors.initials: CD
authors.lastname: Byron
authors.forename: James
authors.initials: J
authors.lastname: Borke
authors.forename: Jack
authors.initials: J
authors.lastname: Yu
authors.forename: David
authors.initials: D
authors.lastname: Pashley
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Wingard
authors.forename: Mark
authors.initials: M
authors.lastname: Hamrick
mesh_terms: D000818:Animals; D001732:Bite Force; D003238:Connective Tissue / Q000502:physiology; D003393:Cranial Sutures / Q000033:anatomy & histology* / Q000502:physiology* / Q000648:ultrastructure; D004548:Elasticity; D017709:Fractals; D008297:Male; D008409:Mastication / Q000502:physiology; D051379:Mice; D008815:Mice, Inbred Strains; D018345:Mice, Knockout; D008855:Microscopy, Electron, Scanning; D055435:Myostatin; D009929:Organ Size; D010012:Osteogenesis; D013314:Stress, Mechanical; D013703:Temporal Muscle / Q000033:anatomy & histology* / Q000502:physiology*; D013718:Tensile Strength; D016212:Transforming Growth Factor beta / Q000172:deficiency
chemical_list: C525912:Mstn protein, mouse; D055435:Myostatin; D016212:Transforming Growth Factor beta