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TECHNICAL PAPERS

Substrate Deformation Levels Associated With Routine Physical Activity Are Less Stimulatory to Bone Cells Relative to Loading-Induced Oscillatory Fluid Flow

[+] Author and Article Information
J. You, C. E. Yellowley, H. J. Donahue, Y. Zhang, Q. Chen, C. R. Jacobs

Musculoskeletal Research Laboratory, Department of Orthopaedics and Rehabilitation, The Pennsylvania State University College of Medicine, Hershey, PA 17033

J Biomech Eng 122(4), 387-393 (Mar 22, 2000) (7 pages) doi:10.1115/1.1287161 History: Received July 21, 1999; Revised March 22, 2000
Copyright © 2000 by ASME
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References

Figures

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Schematic of the substrate stretch device consisting of a silicone membrane and a computer motor-driven micrometer. One end of the membrane was fixed to the microscope stage and the other end was connected to the micrometer. Cells were cultured on the precoated membrane and a plastic ring filled with medium was placed on the membrane.
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Membrane stretch pattern. We first induced dynamic strains of 0.1 percent for 0.5 min followed by a 3 min rest period then 1 percent strain, rest, 5 percent, rest, 10 percent, and then rest. The order of strain levels was also reversed. The strain waveform was a triangle wave and the frequency for all strain experiments was 1 Hz.
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An example of the hFOB cell [Ca2+]i response traces obtained for oscillating flow (2 N/m2, 1 Hz). Note that the arrow depicts the onset of flow.
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Fraction of hFOB cells responding with an increase in [Ca2+]i at different substrate strains and the mean response amplitude. 0.48±0.48 percent, 1.31±0.64 percent, 2.34±0.96 percent, 3.36±1.18 percent and 8.15±0.95 percent of hFOB cells responded for no stretch, 0.1, 1, 5, and 10 percent strain, respectively. Mean response amplitudes of hFOB cells were 37.53±6.83,45.60±10.81,41.68±14.00,39.63±6.32, and 50.57±9.91 nM for no stretch, 0.1, 1, 5, and 10 percent strain, respectively. The data were obtained from six individual experiments and a total of 246 cells. (* represents statistically significant difference (p<0.05) from other four groups, no stretch, 0.1, 1, and 5 percent strain).
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Fraction of hFOB cells responding with an increase in [Ca2+]i at the reversing ordering of application of the various substrate strains. 1.16±0.32,9.40±1.46,4.57±0.50,3.40±0.22, and 1.90±0.29 percent of hFOB cells responded for no stretch, 10, 5, 1, and 0.1 percent strain, respectively. The data were obtained from four individual experiments and a total of 229 cells. (* represents statistically significant difference (p<0.05) from other four groups, no stretch, 5, 1, and 0.1 percent strain).
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Fraction of cells responding with an increase in [Ca2+]i at different substrate strains for ROB cells (left) and MLO-Y4 cells (right). 0.45±0.45,0.35±0.35,2.85±0.79,3.30±0.90, and 12.46±1.91 percent were the percentages of ROB cells responding for no stretch, 0.1, 1, 5, and 10 percent strain. Only the response for 10 percent strain was significantly different from those of four other cases. The results for ROB cells were from six individual experiments that contained total 293 cells. The percentages of responding MLO-Y4 cells were 0.39±0.39,0.48±0.48,2.72±1.04,3.55±1.15, and 9.53±2.17 percent for no stretch, 0.1, 1, 5, and 10 percent strain. The response of 10 percent strain was significantly different from those for 0.1, 1, and 5 percent strain. Six individual experiments had total 227 MLO-Y4 cells. (* represents statistically significant difference (p<0.05) from other four groups, no stretch, 0.1, 1, and 5 percent strain).
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Fraction of cells responding with an increase in [Ca2+]i to dynamic substrate strain (0.5 percent, 1 Hz) and oscillatory flow (2 N/m2, 1 Hz) for hFOB cells. The percentage numbers were 2.24±1.28 percent for dynamic strain and 12.30±1.88 percent for oscillating flow. The total cell numbers for strain and flow were 122 and 332, respectively.
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The relative hFOB cell osteopontin mRNA level change in response to physical stimuli: substrate deformation 0.99±0.12(n=3) and oscillating fluid flow 1.95±0.40(n=2). The mRNA level was measured 72 hours after stimulation.

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