title: Bone mineral crystal size and organization vary across mature rat bone cortex.
abstract: The macro- and micro-features of bone can be assessed by using imaging methods. However, nano- and molecular features require more detailed characterization, such as use of e.g., vibrational spectroscopy and X-ray scattering. Nano- and molecular features also affect the mechanical competence of bone tissue. The aim of the present study was to reveal the effects of mineralization and its alterations on the mineral crystal scale, by investigating the spatial variation of molecular composition and mineral crystal structure across the cross-section of femur diaphyses in young rats, and healthy and osteoporotic mature rats (N=5). Fourier transform infrared spectroscopy and scanning small- and wide-angle X-ray scattering (SAXS/WAXS) techniques with high spatial resolution were used at identical locations over the whole cross-section. This allowed quantification of point-by-point information about the spatial distribution of mineral crystal volume. All measured parameters (crystal dimensions, degree of orientation and predominant orientation) varied across the cortex. Specifically, the crystal dimensions were lower in the central cortex than in the endosteal and periosteal regions. Mineral crystal orientation followed the cortical circumference in the periosteal and endosteal regions, but was less well-oriented in the central regions. Central cortex is formed rapidly during development through endochondral ossification. Since rats possess no osteonal remodeling, this bone remains (until old age). Significant linear correlations were observed between the dimensional and organizational parameters, e.g., between crystal length and degree of orientation (R(2)=0.83, p<0.001). Application of SAXS/WAXS provides valuable information on bone nanostructure and its constituents, effects of diseases and, prospectively, mechanical competence.
authors.affiliation: Department of Biomedical Engineering, Lund University, Lund, Sweden; Department of Applied Physics, University of Eastern Finland, Kuopio, Finland. Electronic address: mikael.turunen@uef.fi.
authors.forename: Mikael J
authors.initials: MJ
authors.lastname: Turunen
authors.affiliation: Department of Biomedical Engineering, Lund University, Lund, Sweden. Electronic address: dovling@gmail.com.
authors.forename: Jørn D
authors.initials: JD
authors.lastname: Kaspersen
authors.affiliation: Division of Physical Chemistry, Lund University, Lund, Sweden. Electronic address: ulf.olsson@fkem1.lu.se.
authors.forename: Ulf
authors.initials: U
authors.lastname: Olsson
authors.affiliation: Paul Scherrer Institut, Villigen PSI, Villigen, Switzerland. Electronic address: manuel.guizar-sicairos@psi.ch.
authors.forename: Manuel
authors.initials: M
authors.lastname: Guizar-Sicairos
authors.affiliation: Department for Medical Radiation Physics, Lund University, Lund, Sweden. Electronic address: martin.bech@med.lu.se.
authors.forename: Martin
authors.initials: M
authors.lastname: Bech
authors.affiliation: Physik-Department und Institut für Medizintechnik, Technische Universität München, Garching, Germany. Electronic address: florian.schaff@tum.de.
authors.forename: Florian
authors.initials: F
authors.lastname: Schaff
authors.affiliation: Department of Orthopaedics, Clinical Sciences, Lund University, Lund, Sweden. Electronic address: magnus.tagil@med.lu.se.
authors.forename: Magnus
authors.initials: M
authors.lastname: Tägil
authors.affiliation: Department of Applied Physics, University of Eastern Finland, Kuopio, Finland; Diagnostic Imaging Centre, Kuopio University Hospital, Kuopio, Finland. Electronic address: jukka.jurvelin@uef.fi.
authors.forename: Jukka S
authors.initials: JS
authors.lastname: Jurvelin
authors.affiliation: Department of Biomedical Engineering, Lund University, Lund, Sweden; Department of Orthopaedics, Clinical Sciences, Lund University, Lund, Sweden. Electronic address: hanna.isaksson@bme.lth.se.
authors.forename: Hanna
authors.initials: H
authors.lastname: Isaksson
mesh_terms: D000818:Animals; D015519:Bone Density; D005260:Female; D005269:Femur / Q000648:ultrastructure*; D017207:Rats, Sprague-Dawley; D053838:Scattering, Small Angle; D017550:Spectroscopy, Fourier Transform Infrared; D014961:X-Ray Diffraction
keywords: Bone mineralization; Fourier transform infrared spectroscopy; Osteoporosis; Rat; Small/wide angle X-ray scattering