Procoagulant phenotype of endothelial cells after coculture with biomaterial‐treated blood cells

Understanding endothelial cell (EC)/blood/biomaterial interactions is crucial for the advancement of cardiovascular devices that often fail because of the lack of nonthrombogenic biomaterials. To begin to assess these interactions, a static EC/blood cell/biomaterial model was used. Isolated blood cells were pretreated with model biomaterial beads with different surface chemistries: polystyrene (PS), and PS beads grafted with 3‐kDa polyethylene glycol (PEG) with either a hydroxyl (PS‐PEG‐OH) or amine (PS‐PEG‐NH 2 ) terminal group at 5.4 or 54 × 10 4 beads/mL. Biomaterial‐treated monocytes, neutrophils, or platelets were applied to human umbilical vein ECs (HUVECs) for 5 or 24 h of static coculture, and the resultant procoagulant HUVEC phenotype was characterized using several methods. Flow cytometry was used to assess surface expression of tissue factor (TF), adenosine triphosphate diphosphohydrolase, phosphatidylserine, and thrombomodulin, a functional TF assay was used to assess TF activity, and a plasma recalcification assay examined clotting times on HUVECs. Static coculture of HUVEC with biomaterial‐treated neutrophils induced a procoagulant phenotype as exemplified by upregulation of TF expression and total functional activity, and downregulation of adenosine triphosphate diphosphohydrolase and thrombomodulin expression. The plasma recalcification assay demonstrated that HUVECs cocultured with biomaterial‐treated monocytes significantly shortened clotting times, with some effect of similarly treated neutrophils. © 2005 Wiley Periodicals, Inc. J Biomed Mater Res 72A: 269–278, 2005