title: Low-amplitude, broad-frequency vibration effects on cortical bone formation in mice.
abstract: Mechanical loading of the skeleton is necessary to maintain bone structure and strength. Large amplitude strains associated with vigorous activity typically result in the greatest osteogenic response; however, data suggest that low-amplitude, broad-frequency vibration results in new bone formation and may enhance adaptation through a stochastic resonance (SR) phenomenon. That is, random noise may maximally enhance bone formation to a known osteogenic stimulus. The aims of this study were to (1) assess the ability of different vibration signals to enhance cortical bone formation during short- and long-term loading and (2) determine whether vibration could effect SR in bone. Two studies were completed wherein several osteogenic loading waveforms, with or without an additive low-amplitude, broad-frequency (0-50 Hz) vibration signal, were applied to the mouse ulna in axial compression. In study 1, mice were loaded short-term (30 s/day, 2 days) with either a carrier signal alone (1 or 2 N sine waveform), vibration signal alone [0.1 N or 0.3 N root mean square (RMS)] or combined carrier and vibration signal. In study 2, mice were loaded long-term (30 s/day, 3 days/week, 4 weeks) with a carrier signal alone (static or sine waveform), vibration signal alone (0.02 N, 0.04 N, 0.08 N or 0.25 N RMS) or combined carrier and vibration signal. Sequential calcein bone labels were administered at 2 and 4 days and at 4 and 29 days after the first day of loading in study 1 and 2, respectively; bone formation parameters and changes in geometry were measured. Combined application of the carrier and vibration signals in study 1 resulted in significantly greater bone formation than with either signal alone (P < 0.001); however, this increase was independently explained by increased strain levels associated with additive vibration. When load and strain levels were similar across loading groups in study 2, cortical bone formation and changes in geometry were not significantly altered by vibration. Vibration alone did not result in any new bone formation. Our data suggest that low-amplitude, broad-frequency vibration superimposed onto an osteogenic waveform or vibration alone does not enhance cortical bone adaptation at the frequencies, amplitudes and loading periods tested.
authors.affiliation: Department of Biomedical Engineering, Purdue School of Engineering and Technology, Indiana University School of Medicine, 1120 South Drive, Fesler Hall 115, Indianapolis, IN 46202, USA. Electronic address: alecasti@iupui.edu.
authors.forename: Alesha B
authors.initials: AB
authors.lastname: Castillo
authors.affiliation: Department of Biomedical Engineering, Purdue School of Engineering and Technology, Indiana University School of Medicine, 1120 South Drive, Fesler Hall 115, Indianapolis, IN 46202, USA. Electronic address: ialam@iupui.edu.
authors.forename: Imranul
authors.initials: I
authors.lastname: Alam
authors.affiliation: Graduate School of Natural Science and Technology, Kanazawa University, Kanazawa, Ishikawa 920-1192, Japan. Electronic address: shigeo@t.kanazawa-u.ac.jp.
authors.forename: Shigeo M
authors.initials: SM
authors.lastname: Tanaka
authors.affiliation: Department of Biomedical Engineering, Purdue School of Engineering and Technology, Indiana University School of Medicine, 1120 South Drive, Fesler Hall 115, Indianapolis, IN 46202, USA. Electronic address: jplevend@iupui.edu.
authors.forename: Jeffery
authors.initials: J
authors.lastname: Levenda
authors.affiliation: Department of Anatomy and Cell Biology, Indiana University School of Medicine, Indianapolis, IN 46202, USA. Electronic address: jilili@iupui.edu.
authors.forename: Jiliang
authors.initials: J
authors.lastname: Li
authors.affiliation: Department of Physical Therapy, School of Health and Rehabilitation Sciences, Indiana University School of Medicine, 1120 South Drive, Indianapolis, IN 46202, USA. Electronic address: stwarden@iupui.edu.
authors.forename: Stuart J
authors.initials: SJ
authors.lastname: Warden
authors.affiliation: Department of Biomedical Engineering, Purdue School of Engineering and Technology, Indiana University School of Medicine, 1120 South Drive, Fesler Hall 115, Indianapolis, IN 46202, USA. Electronic address: turnerch@iupui.edu.
authors.forename: Charles H
authors.initials: CH
authors.lastname: Turner
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D015519:Bone Density / Q000502:physiology; D001842:Bone and Bones / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D005260:Female; D051379:Mice; D008810:Mice, Inbred C57BL; D010012:Osteogenesis / Q000502:physiology*; D013314:Stress, Mechanical; D014457:Ulna / Q000166:cytology / Q000378:metabolism / Q000502:physiology; D014732:Vibration