The effect of cyclic pressure on human monocyte-derived macrophages in vitro

Aseptic loosening and osteolysis around prosthetic joints are the principal causes of failure and consequent revision. During this process activated m acrophages produce cytokines which are thought to promote osteolysis by ost eoclasts. Changes in pressure within the space around implants have been pr oposed as a cause of loosening and osteolysis, We therefore studied the eff ect of two different regimes of cyclic pressure on the production of interl eukin-1 beta (IL-1 beta), IL-6 and tumour necrosis factor-alpha (TNF-alpha) by cultured human monocyte-derived (M-D) macrophages, There was a wide var iation in the expression of cytokines in non-stimulated M-D macrophages fro m different donors and therefore cells from the same donor were compared un der control and pressurised conditions. Both regimes of cyclic pressure were found to increase expression of IL-6 a nd TNF-alpha. Expression of IL-1 beta was increased by a higher-frequency r egime only. Our findings suggest that M-D macrophages are activated by cycl ic pressure. Further work will be required to understand the relative roles of frequency, amplitude and duration of applied pressure in the cellular e ffects of cyclic pressure in this system.