The Journal of Bone and Joint Surgery, Vol 73, Issue 3 320-331, Copyright © 1991 by Journal of Bone and Joint Surgery, Inc
The proliferative and synthetic response of isolated calvarial bone cells of rats to cyclic biaxial mechanical strain
CT Brighton, B Strafford, SB Gross, DF Leatherwood, JL Williams and SR Pollack
Department of Orthopedic Surgery, University of Pennsylvania School of Medicine, Philadelphia 19104-6081.
Isolated bone cells from the calvaria of newborn rats were grown in
monolayer on polyurethane membranes in specially constructed culture
chambers. These were subjected to cyclic biaxial mechanical strains of 0.02
per cent (200 microstrain), 0.04 per cent (400 microstrain), and 0.1 per
cent (1000 microstrain) at a frequency of one hertz for periods ranging
from fifteen minutes to seventy-two hours. DNA content, an index of
proliferation, was significantly increased at a strain of 0.04 per cent
applied for fifteen minutes and for twenty-four and forty-eight hours. DNA
content was not increased at the other amplitudes of strain that were
evaluated, nor was it increased after prolonged mechanical stimulation for
forty-eight hours or longer. Synthesis of collagen, non-collagenous
protein, and proteoglycan, as well as activity of alkaline phosphatase, all
indicators of macromolecular synthesis, were significantly decreased at a
strain of 0.04 per cent applied for fifteen minutes and for twenty-four,
forty-eight, and seventy-two hours. Macromolecular synthesis was not
affected by the other amplitudes of strain that were evaluated in this
study. At a strain of 0.04 per cent, prostaglandin E2 content was
significantly increased after five, fifteen, and thirty minutes of
mechanical stimulation, whereas net cAMP content did not change
significantly. This suggests that the described cellular events (increased
proliferation and decreased macromolecular synthesis) that occur secondary
to mechanical strain are mediated, at least in part, by prostaglandin E2.
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