The effect of strain on bone cell prostaglandin E2 release: A new experimental method

Summary A new method of investigating the mechanisms of strain-induced bone remodeling has been developed. Bone cells were subjected to cyclical strainsin vitro by computer-controlled stretching of the plastic substrate on which they were cultured, enabling both physiological and pathological strains to be investigated. Physiological strains have not previously been investigatedin vitro. The prostaglandin E₂ (PGE₂) released by the cells was found to depend on the strain magnitude. It was independent of cycle time, and 5 hours after straining had ceased, it had returned to control levels. These results are similar to thein vivo findings that bone remodeling is dependent on strain magnitude and not strain frequency, indicating that PGE₂ may play an important role in strain-induced bone remodeling. The relationship between PGE₂ release and strain magnitude was biphasic, with particularly high levels being released at strains that would be associated with either abnormally strenuous activity or microstructural bone damage. It is therefore possible that PGE₂ stimulates the osteogenesis caused by increased functional demands, and initiates the remodeling caused by bone damage. This new method of investigating strain-induce remodeling is useful, as any cell type, any mediator, and any strain pattern or parameter can be individually studied.