title: Age-related changes in mouse bone permeability.
abstract: The determination of lacunar-canalicular permeability is essential for understanding local fluid flow in bone, which may indicate how bone senses changes in the mechanical environment to regulate mechano-adaptation. The estimates of lacunar-canalicular permeability found in the literature vary by up to eight orders of magnitude, and age-related permeability changes have not been measured in non-osteonal mouse bone. The objective of this study is to use a poroelastic approach based on nanoindentation data to characterize lacunar-canalicular permeability in murine bone as a function of age. Nine wild type C57BL/6 mice of different ages (2, 7 and 12 months) were used. Three tibiae from each age group were embedded in epoxy resin, cut in half and indented in the longitudinal direction in the mid-cortex using two spherical fluid indenter tips (R=238 μm and 500 μm). Results suggest that the lacunar-canalicular intrinsic permeability of mouse bone decreases from 2 to 7 months, with no significant changes from 7 to 12 months. The large indenter tip imposed larger contact sizes and sampled larger ranges of permeabilities, particularly for the old bone. This age-related difference in the distribution was not seen for indents with the smaller radius tip. We conclude that the small tip effectively measured lacunar-canalicular permeability, while larger tip indents were influenced by vascular permeability. Exploring the age-related changes in permeability of bone measured by nanoindentation will lead to a better understanding of the role of fluid flow in mechano-transduction. This understanding may help indicate alterations in bone adaptation and remodeling.
authors.affiliation: Department of Bioengineering, Imperial College London, London SW7 2AZ, UK. Electronic address: nr211@imperial.ac.uk.
authors.forename: Naiara
authors.initials: N
authors.lastname: Rodriguez-Florez
authors.affiliation: Department of Engineering, Cambridge University, Cambridge CB2 1PZ, UK.
authors.forename: Michelle L
authors.initials: ML
authors.lastname: Oyen
authors.affiliation: Department of Mechanical and Industrial Engineering, Northeastern University, Boston, MA 02115, USA.
authors.forename: Sandra J
authors.initials: SJ
authors.lastname: Shefelbine
mesh_terms: D000222:Adaptation, Physiological; D000375:Aging / Q000378:metabolism*; D000818:Animals; D001842:Bone and Bones / Q000378:metabolism*; D004548:Elasticity; D005260:Female; D051379:Mice; D008810:Mice, Inbred C57BL; D010539:Permeability; D013977:Tibia
keywords: Age; Murine bone; Nanoindentation; Permeability; Poroelasticity