Proinflammatory phenotype of endothelial cells after coculture with biomaterial-treated blood cells

An understanding of the endothelial cell/blood/biomaterial interactions is central to advancing the success of cardiovascular devices that continue to fail because of the lack of nonthrombogenic biomaterials. A simplified endothelial cell/blood cell/biomaterial static model was used to assess these interactions. Human whole blood or isolated blood cells (mononuclear cells, neutrophils, platelets) were pretreated with biomaterial beads with different surface chemistries: polystyrene (PS), PS beads grafted with 3-kDa polyethylene glycol (PEG) with either hydroxyl (PS-PEG-OH) or amine (PS-PEG-NH2) terminal groups at bead concentrations of 5.4 or 54 x 10(4) beads/mL. Leukocyte and platelet activation and microparticle formation was assessed using flow cytometry. Biomaterial-activated whole blood or isolated cells or mononuclear cell fractions were applied to human umbilical cord endothelial cells (HUVEC) for static coculture, and the resultant proinflammatory HUVEC phenotype was characterized. ICAM-1 and E-selectin expression on HUVEC was increased after 4-h static coculture with biomaterial-treated human whole blood or mononuclear cells but not neutrophils or platelets. VCAM-1 expression on HUVEC was similarly increased after 24-h static coculture but not after 4 h of coculture. Increased concentrations of cytokines, IL-6, IL-8, and MCP-1, were detected in the supernatant of cocultures of HUVEC with biomaterial-treated whole blood or mononuclear cells but not neutrophils or platelets, compared with the media control. After 24 h, cytokine release was significantly increased for both IL-8 and MCP-1 but not IL-6 above concentrations after 4 h of coculture. Neither the cell adhesion molecule (CAM) expression nor cytokine release induced by coculture with biomaterial-treated whole blood or isolated cells was dependent on either material surface chemistry or material surface area. The changes in HUVEC CAM expression and cytokine release induced by biomaterial-treated mononuclear cells can be attributed predominantly to adherent cells on beads and nonadherent bulk cells with moderate regulation by the soluble supernatant; however, mononuclear cell-derived microparticles induced no significant changes in CAM expression or cytokine release after static coculture with HUVEC.