title: Effects of broad frequency vibration on cultured osteoblasts.
abstract: Bone is subjected in vivo to both high amplitude, low frequency strain, incurred by locomotion, and to low amplitude, broad frequency strain. The biological effects of low amplitude, broad frequency strain are poorly understood. To evaluate the effects of low amplitude strains ranging in frequency from 0 to 50 Hz on osteoblastic function, we seeded MC3T3-E1 cells into collagen gels and applied the following loading protocols for 3 min per day for either 3 or 7 days: (1) sinusoidal strain at 3 Hz, with 0-3000 microstrain peak-to-peak followed by 0.33 s resting time, (2) "broad frequency vibration" of low amplitude strain (standard deviation of 300 microstrain) including frequency components from 0 to 50 Hz, and (3) sinusoidal strain combined with broad frequency vibration (S + V). The cells were harvested on day 4 or 8. We found that the S + V stimulation significantly repressed cell proliferation by day 8. Osteocalcin mRNA was up-regulated 2.6-fold after 7 days of S + V stimulation, and MMP-9 mRNA was elevated 1.3-fold after 3 days of vibration alone. Sinusoidal stimulation alone did not affect the cell responses. No differences due to loading were observed in alkaline phosphatase activity and in mRNA levels of type I collagen, osteopontin, connexin 43, MMPs-1A, -3, -13. These results suggest that osteoblasts are more sensitive to low amplitude, broad frequency strain, and this kind of strain could sensitize osteoblasts to high amplitude, low frequency strain. This suggestion implies a potential contribution of stochastic resonance to the mechanical sensitivity of osteoblasts.
authors.affiliation: Department of Orthopedic Surgery, Biomaterials & Biomechanics Research Center, Indiana University School of Medicine, 541 Clinical Drive, Room 600, Indianapolis, IN 46202-5111, USA.
authors.forename: Shigeo M
authors.initials: SM
authors.lastname: Tanaka
authors.forename: Jiliang
authors.initials: J
authors.lastname: Li
authors.forename: Randall L
authors.initials: RL
authors.lastname: Duncan
authors.forename: Hiroki
authors.initials: H
authors.lastname: Yokota
authors.forename: David B
authors.initials: DB
authors.lastname: Burr
authors.forename: Charles H
authors.initials: CH
authors.lastname: Turner
mesh_terms: D016475:3T3 Cells / Q000166:cytology / Q000502:physiology; D000469:Alkaline Phosphatase / Q000096:biosynthesis*; D000818:Animals; D002455:Cell Division / Q000502:physiology; D004789:Enzyme Activation / Q000502:physiology; D005786:Gene Expression Regulation / Q000502:physiology*; D020780:Matrix Metalloproteinase 9 / Q000235:genetics; D040542:Mechanotransduction, Cellular / Q000502:physiology*; D051379:Mice; D010006:Osteoblasts / Q000166:cytology / Q000502:physiology*; D015675:Osteocalcin / Q000235:genetics; D010812:Physical Stimulation; D011312:Pressure; D012333:RNA, Messenger / Q000378:metabolism; D012016:Reference Values; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013314:Stress, Mechanical; D015854:Up-Regulation / Q000502:physiology; D014732:Vibration; D016474:Weight-Bearing / Q000502:physiology
chemical_list: D012333:RNA, Messenger; D015675:Osteocalcin; D000469:Alkaline Phosphatase; D020780:Matrix Metalloproteinase 9