Combined effect of titanium particles and TNF-alpha on the production of IL-6 by osteoblast-like cells

To clarify the role of tumor necrosis factor (TNF)-alpha on osteoblast func tions in the presence of metal particles, two human osteoblast-like cell li nes (MG-63 and SaOS-2) were cultured with TNF-alpha in the presence or abse nce of titanium particles in vitro. A combination of TNF-alpha and titanium particles showed additive effects on inhibition of cell proliferation and alkaline phosphatase production. On the other hand, production of interleuk in-6, which is well known to induce osteoclastogenesis and to directly stim ulate bone resorption, was additively stimulated by the combination of TNF- alpha and titanium particles. These results suggest that the association of TNF-alpha and titanium particles may play an important role in the pathoge nesis of periprosthetic osteolysis through two different pathways: a reduce d periprosthetic bone formation due to inhibition of osteoblast proliferati on and alkaline phosphatase production, and osteoblast-mediated activation of osteoclastic bone resorption as suggested by the enhancement of interleu kin-6 production. (C) 2000 John Wiley & Sons, Inc.