title: Immobilization and long-term recovery results in large changes in bone structure and strength but no corresponding alterations of osteocyte lacunar properties.
abstract: The ability of osteocytes to demineralize the perilacunar matrix, osteocytic osteolysis, and thereby participate directly in bone metabolism, is an aspect of osteocyte biology that has received increasing attention during the last couple of years. The aim of the present work was to investigate whether osteocyte lacunar properties change during immobilization and subsequent recovery. A rat cortical bone model with negligible Haversian remodeling effects was used, with temporary immobilization of one hindlimb induced by botulinum toxin. Several complementary techniques covering multiple length scales enabled correlation of osteocyte lacunar properties to changes observed on the organ and tissue level of femoral bone. Bone structural parameters measured by μCT and mechanical properties were compared to sub-micrometer resolution SR μCT data mapping an unprecedented number (1.85 million) of osteocyte lacunae. Immobilization induced a significant reduction in aBMD, bone volume, tissue volume, and load to fracture, as well as the muscle mass of rectus femoris. During the subsequent recovery period, the bone structural and mechanical properties were only partly regained in spite of a long-term (28weeks) study period. No significant changes in osteocyte lacunar volume, density, oblateness, stretch, or orientation were detected upon immobilization or subsequent recovery. In conclusion, the bone architecture and not osteocyte lacunar properties or bone material characteristics dominate the immobilization response as well as the subsequent recovery.
authors.affiliation: Department of Chemistry and iNANO, Aarhus University, 140 Langelandsgade, DK -8000 Aarhus, Denmark.
authors.forename: Fiona Linnea
authors.initials: FL
authors.lastname: Bach-Gansmo
authors.affiliation: Department of Chemistry and iNANO, Aarhus University, 140 Langelandsgade, DK -8000 Aarhus, Denmark.
authors.forename: Nina Kølln
authors.initials: NK
authors.lastname: Wittig
authors.affiliation: Department of Biomedicine, Aarhus University, Aarhus, Denmark.
authors.forename: Annemarie
authors.initials: A
authors.lastname: Brüel
authors.affiliation: Department of Biomedicine, Aarhus University, Aarhus, Denmark.
authors.forename: Jesper Skovhus
authors.initials: JS
authors.lastname: Thomsen
authors.affiliation: Department of Chemistry and iNANO, Aarhus University, 140 Langelandsgade, DK -8000 Aarhus, Denmark. Electronic address: hbirkedal@chem.au.dk.
authors.forename: Henrik
authors.initials: H
authors.lastname: Birkedal
mesh_terms: D015502:Absorptiometry, Photon; D000818:Animals; D001696:Biomechanical Phenomena; D015519:Bone Density; D001842:Bone and Bones / Q000000981:diagnostic imaging / Q000473:pathology* / Q000503:physiopathology*; D019274:Botulinum Toxins, Type A / Q000008:administration & dosage; D005260:Female; D005269:Femur / Q000000981:diagnostic imaging; D005684:Gait; D007091:Image Processing, Computer-Assisted; D007103:Immobilization; D007267:Injections; D010011:Osteocytes / Q000473:pathology*; D017208:Rats, Wistar
chemical_list: D019274:Botulinum Toxins, Type A
keywords: Immobilization; Osteocyte lacunae; Osteocytes; Osteocytic osteolysis; Synchrotron μCT; μCT