Alterations in the adhesion behavior of osteoblasts by titanium particle loading: Inhibition of cell function and gene expression

Total joint replacement prostheses are required to withstand corrosive envi ronments and sustain millions of loading and articulation cycles during the ir term of implantation. Wear debris generation has been implicated as one of the primary causes of periprosthetic osteolysis and subsequent implant l oosening in total joint replacements. Particulate debris consisting of meta ls, polyethylene, ceramics, and bone cement have each been shown to provoke a biological response in joint tissues. The major cell types within the in terfacial granulomatous fibrous tissues consist of fibroblasts, macrophages , lymphocytes, and foreign-body giant cells. Osteoblasts are one of the pri ncipal cell types in the bone tissue adjacent to prostheses, maintaining ph ysiologic bone remodeling through the balanced coordination of bone formati on and resorption in concert with osteoclasts. To date the phenomenon of os teoblast phagocytosis of titanium particles has been suggested, but has not been sufficiently studied or confirmed. This study seeks to clarify the in fluence of titanium particles on osteoblast adhesion, deformability, prolif eration, and gene expression profile. These studies were accomplished by pe rforming biorheological testing, Northern blot analysis and RNase protectio n assay. The uptake of metallic particles by the osteoblast resulted in a p article-filament complex formation, which induced a series of variations in cell function. Understanding these variations is critical to expanding our knowledge of implant loosening and elucidating the nature of prosthetic jo int failure. This study suggests that the impact of titanium particles on o steoblast function and subsequent implant loosening may have been previousl y underestimated.