Tissue factor expression by rat osteosarcoma cells adherent to tissue culture polystyrene and selected orthopedic biomaterials.

Tissue factor (TF), a transmembrane glycoprotein expressed by numerous cell types, plays a critical role in the initiation of blood coagulation at sites of vascular injury. Activated products of the coagulation cascade may then enhance the inflammatory responses associated with wound healing. In the present investigation the ability of rat osteosarcoma (ROS) cells to express TF activity was examined following their growth on tissue-culture polystyrene (TCPS) and selected orthopedic biomaterials (titanium and zirconium alloys, and stainless steel). ROS cells exhibited significant TF activity as evidenced by the conversion of Factor X to Factor Xa in the presence of TF, Factor VIIa, and Ca2+. Factor Xa concentrations ranged from 1.0 fM per cell at 10 min to 6.0 fM per cell after 60 min. Additionally, ROS cells stimulated with calcium ionophore (A23187) exhibited approximately twice the activity of non-stimulated cells when grown on TCPS but not on the metallic substrates. ROS cells (stimulated or unstimulated) adherent to the zirconium alloy generated lower amounts of Factor Xa compared to those bound to the other alloys and unstimulated cells grown on TCPS. These results indicate that ROS cells cultured on these synthetic surfaces differentially express procoagulant activity and that cells grown on TCPS, but not the metallic alloys, exhibit increased TF activity in response to stimulation by calcium ionophore. This procoagulant activity may potentiate subsequent inflammatory responses associated with the use of orthopedic biomaterials and thereby influence the tissue compatibility of the implant.