Role of leucocytes in coagulation induced by artificial surfaces: investigation of expression of Mac-1, granulocyte elastase release and leucocyte adhesion on modified polyurethanes

Thrombus formation on artificial surfaces can be viewed as the sequential and concomitant involvement of protein adsorption, platelet reactions, activation of the coagulation system, participation of complement, fibrinolytic and kallikrein-kinin systems, and the interaction of cellular elements. This study examines the activation of leucocytes on a series of well-characterized polyurethanes with different ionic groups [sulphonate groups (negatively charged); quaterinary amine groups (positively charged)], in terms of adhesion, degranulation and cell surface integrin receptor expression. Leucocyte adhesion was monitored with radiolabelled neutrophils and scanning electron microscopy (SEM), degranulation by measurement of human neutrophil elastase using an indirect enzyme-linked immunosorbent assay and cell surface expression of the integrin receptor Mac-1, using fluorescentactivated cell sorting (FACS). Our results indicate a trend towards enhanced adhesion and degranulation with respect to the negatively charged polyurethane. Similar results were observed with respect to the integrin Mac-1 from recovered adherent cells. The findings of enhanced adhesion and spreading, Mac-1 up-regulation and granulocyte elastase release from the negatively charged sulphonated polyurethane indicate the potential of leucocytes to contribute towards thrombus formation on such surfaces.