The impact of low-magnitude high-frequency vibration on fracture healing is profoundly influenced by the oestrogen status in mice.
Fracture healing is impaired in aged and osteoporotic individuals. Because adequate mechanical stimuli are able to increase bone formation, one therapeutical approach to treat poorly healing fractures could be the application of whole-body vibration, including low-magnitude high-frequency vibration (LMHFV). We investigated the effects of LMHFV on fracture healing in aged osteoporotic mice. Female C57BL/6NCrl mice (n=96) were either ovariectomised (OVX) or sham operated (non-OVX) at age 41 weeks. When aged to 49 weeks, all mice received a femur osteotomy that was stabilised using an external fixator. The mice received whole-body vibrations (20 minutes/day) with 0.3 G: peak-to-peak acceleration and a frequency of 45 Hz. After 10 and 21 days, the osteotomised femurs and intact bones (contra-lateral femurs, lumbar spine) were evaluated using bending-testing, micro-computed tomography (μCT), histology and gene expression analyses. LMHFV disturbed fracture healing in aged non-OVX mice, with significantly reduced flexural rigidity (-81%) and bone formation (-80%) in the callus. Gene expression analyses demonstrated increased oestrogen receptor β (ERβ, encoded by Esr2) and Sost expression in the callus of the vibrated animals, but decreased β-catenin, suggesting that ERβ might mediate these negative effects through inhibition of osteoanabolic Wnt/β-catenin signalling. In contrast, in OVX mice, LMHFV significantly improved callus properties, with increased flexural rigidity (+1398%) and bone formation (+637%), which could be abolished by subcutaneous oestrogen application (0.025 mg oestrogen administered in a 90-day-release pellet). On a molecular level, we found an upregulation of ERα in the callus of the vibrated OVX mice, whereas ERβ was unaffected, indicating that ERα might mediate the osteoanabolic response. Our results indicate a major role for oestrogen in the mechanostimulation of fracture healing and imply that LMHFV might only be safe and effective in confined target populations.
Institute of Orthopedic Research and Biomechanics, Center of Musculoskeletal Research, University of Ulm, 89081 Ulm, Germany.
Esther
E
Wehrle
Institute of Orthopedic Research and Biomechanics, Center of Musculoskeletal Research, University of Ulm, 89081 Ulm, Germany.
Astrid
A
Liedert
Institute of Orthopedic Research and Biomechanics, Center of Musculoskeletal Research, University of Ulm, 89081 Ulm, Germany.
Aline
A
Heilmann
Institute of Orthopedic Research and Biomechanics, Center of Musculoskeletal Research, University of Ulm, 89081 Ulm, Germany.
Tim
T
Wehner
Institute of Orthopedic Research and Biomechanics, Center of Musculoskeletal Research, University of Ulm, 89081 Ulm, Germany.
Ronny
R
Bindl
Institute of Orthopedic Research and Biomechanics, Center of Musculoskeletal Research, University of Ulm, 89081 Ulm, Germany.
Lena
L
Fischer
Institute of Orthopedic Research and Biomechanics, Center of Musculoskeletal Research, University of Ulm, 89081 Ulm, Germany.
Melanie
M
Haffner-Luntzer
Orthopedic Center for Musculoskeletal Research, Orthopedic Department, University of Würzburg, 97074 Würzburg, Germany.
Franz
F
Jakob
Institute of Osteology and Biomechanics, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany.
Thorsten
T
Schinke
Institute of Osteology and Biomechanics, University Medical Center Hamburg-Eppendorf, 20246 Hamburg, Germany.
Michael
M
Amling
Institute of Orthopedic Research and Biomechanics, Center of Musculoskeletal Research, University of Ulm, 89081 Ulm, Germany. anita.ignatius@uni-ulm.de.
Anita
A
Ignatius
D000818:Animals; D004967:Estrogens / Q000502:physiology*; D005260:Female; D005269:Femur / Q000473:pathology; D017102:Fracture Healing; D007150:Immunohistochemistry; D051379:Mice; D008810:Mice, Inbred C57BL; D014176:Protein Biosynthesis; D011960:Receptors, Estrogen / Q000097:blood*; D015398:Signal Transduction; D014732:Vibration; D051176:beta Catenin / Q000378:metabolism
C495267:CTNNB1 protein, mouse; D004967:Estrogens; D011960:Receptors, Estrogen; D051176:beta Catenin
Fracture healing; LMHFV; Oestrogen receptor signalling; Whole-body vibration; Wnt signalling