Anticoagulant properties of glycosaminoglycans derived from cultured endothelial cells

Anticoagulant properties of culture medium conditioned by human umbilical vein endothelial cells were investigated. In the presence of conditioned medium, both prothrombin time and activated partial thromboplastin time of normal plasma were prolonged by 4 and 10 seconds respectively compared with those in the presence of nonconditioned medium. The prologation of coagulation time was not affected by the presence or absence of serum in the culture medium, indicating that endothelial cells release the anticoagulant activity into the culture medium. The concentrated serum-free conditioned medium, not only directly inhibited Factor Xa activity but also enhanced the inactivation of Xa activity by antithrombin III. On the other hand, acidic glycosaminoglycans (GAG) isolated from conditioned culture medium showed Xa inhibition only in the presence of antithrombin II. These results suggest that anticoagulant properties of endothelial conditioned medium are, at least in part, attributed to GAG(s) released by these cells.