title: Bone strain magnitude is correlated with bone strain rate in tetrapods: implications for models of mechanotransduction.
abstract: Hypotheses suggest that structural integrity of vertebrate bones is maintained by controlling bone strain magnitude via adaptive modelling in response to mechanical stimuli. Increased tissue-level strain magnitude and rate have both been identified as potent stimuli leading to increased bone formation. Mechanotransduction models hypothesize that osteocytes sense bone deformation by detecting fluid flow-induced drag in the bone's lacunar-canalicular porosity. This model suggests that the osteocyte's intracellular response depends on fluid-flow rate, a product of bone strain rate and gradient, but does not provide a mechanism for detection of strain magnitude. Such a mechanism is necessary for bone modelling to adapt to loads, because strain magnitude is an important determinant of skeletal fracture. Using strain gauge data from the limb bones of amphibians, reptiles, birds and mammals, we identified strong correlations between strain rate and magnitude across clades employing diverse locomotor styles and degrees of rhythmicity. The breadth of our sample suggests that this pattern is likely to be a common feature of tetrapod bone loading. Moreover, finding that bone strain magnitude is encoded in strain rate at the tissue level is consistent with the hypothesis that it might be encoded in fluid-flow rate at the cellular level, facilitating bone adaptation via mechanotransduction.
authors.affiliation: Department of Organismal Biology and Anatomy, University of Chicago, Chicago, IL 60637, USA braiello@uchicago.edu.
authors.forename: B R
authors.initials: BR
authors.lastname: Aiello
authors.affiliation: Department of Oral Biology, University of Illinois at Chicago, Chicago, IL 60612, USA.
authors.forename: J
authors.initials: J
authors.lastname: Iriarte-Diaz
authors.affiliation: Department of Biological Sciences, Clemson University, Clemson, SC 29634, USA.
authors.forename: R W
authors.initials: RW
authors.lastname: Blob
authors.affiliation: Department of Biological Sciences, Youngstown State University, Youngstown, OH 44555, USA.
authors.forename: M T
authors.initials: MT
authors.lastname: Butcher
authors.affiliation: Department of Paleobiology, Smithsonian Institution, Washington, DC 20013, USA.
authors.forename: M T
authors.initials: MT
authors.lastname: Carrano
authors.affiliation: Department of Biological Sciences, Clemson University, Clemson, SC 29634, USA.
authors.forename: N R
authors.initials: NR
authors.lastname: Espinoza
authors.affiliation: Department of Basic Medical Sciences, College of Veterinary Medicine and Weldon School of Biomedical Engineering, Purdue University, West Lafayette, IN 47907, USA.
authors.forename: R P
authors.initials: RP
authors.lastname: Main
authors.affiliation: Department of Organismal Biology and Anatomy, University of Chicago, Chicago, IL 60637, USA rossc@uchicago.edu.
authors.forename: C F
authors.initials: CF
authors.lastname: Ross
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D005269:Femur / Q000502:physiology*; D011884:Radius / Q000502:physiology*; D013314:Stress, Mechanical; D014714:Vertebrates / Q000502:physiology*
keywords: bone fluid flow; bone mechanotransduction; bone strain; strain rate