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Vol. 37 No. 2, March/April 2000

Osteoporosis and bone functional adaptation: Mechanobiological regulation of bone architecture in growing and adult bone, a review

John R. Mosley, BVM&S, PhD, Senior Clinical Training Scholar

The R(D)SVS Hospital for Small Animals, Department of Veterinary Clinical Studies, The Royal (Dick) School of Veterinary Studies, University of Edinburgh, Easter Bush Veterinary Centre, Easter Bush, ROSLIN, United Kingdom EH25 9RG

Abstract — During life, bone is continually optimized for its load-bearing role by a process of functionally adaptive (re)modelling. This process, which is more active in growing bone, is dominated by high-magnitude, high-rate strains, presented in an unusual distribution. Adaptation occurs at an organ level, involving changes in whole bone architecture and bone mass. The repetitive coordinated bone loading associated with habitual activity may have little role in the preservation of bone mass, and may even reduce the osteogenic potential of an otherwise highly osteogenic stimulus. Cells of the osteocyte/osteoblast network are best placed to appreciate mechanical strain. Among the strain-related responses they show, is a reduced rate of apoptosis. This may serve to regulate and target osteoclast activity. A more complete understanding of the stimuli and pathways involved in both the physiology and pathology of this structural homeostatic mechanism will allow the design of more appropriate exercise regimens and targeted pharmacological interventions to limit morbidity and mortality by reducing bone fragility.

Key words: adaptation, apoptosis, cortical bone, estrogen, mechanical strain, mechanical stress, osteoblast, osteoclast, osteocyte, osteoporosis.

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