Preferential degradation of osteoclasts by titanium tetrachloride

Although titanium alloys are known to be biocompatible with bone tissue aft er implantation in human beings, the effect of titanium on osteoclasts rema ins to be studied. We examined the effect of titanium salt on the formation and survival of osteoclasts in cell culture. The addition of 10 muM titani um tetrachloride caused a decrease in the cell number of osteoclast-like ce lls induced in bone marrow cell cultures taken from mice. The addition of 1 0 muM titanium tetrachloride caused degradation of the disaggregated osteoc lasts taken from neonatal rats and a decrease in bone resorption. Along wit h the increase in the degradation of osteoclasts, the number of apoptotic c ells increased. Titanium tetrachloride dose-dependently decreased the cell number and alkaline phosphatase activity of osteoblastic cell cultures take n from rat calvaria. However, these concentrations were 30-40 times higher than those in the case of osteoclast-like cell formation. These results sho wed that tirtanium ions caused a preferential degradation of osteoclasts ra ther than osteoblasts, most likely by apoptosis. (C) 2001 John Wiley & Sons , Inc.