Rapid in vitro biocompatibility assay of endovascular stents by flow cytometry using platelet activation and platelet-leukocyte aggregation

Clinical studies suggest that stent design and surface texture are responsi ble for differences in biocompatibility of metallic endovascular stents, A simple in vitro experimental setup was established to test stent-induced de gree of platelet and leukocyte activation and platelet-leukocyte aggregatio n by flow cytometry, Heparin-coated tantalum stents and gold-coated and unc oated stainless steel stents were tested. Stents were implanted into silico ne tubes and exposed to blood from healthy volunteers. Platelet and leukocy te activation and percentage of leukocyte-platelet aggregates were determin ed in a whole-blood assay by subsequent staining for activation-associated antigens (CD41a, CD42b, CD62p, and fibrinogen binding) and leukocyte antige ns (CD14 and CD45) and flow cytometric analysis, Blood taken directly after venous puncture or exposed to the silicone tube alone was used as negative controls. Positive control was in vitro stimulation with thrombin receptor activating peptide (TRAP-6). Low degree of platelet activation and signifi cant increase in monocyte- and neutrophil-platelet aggregation were observe d in blood exposed to stents (P < 0.05). In addition, leukocyte activation was induced as measured by increased CD45 and CD14 expression, Heparin coat ed stents continuously induced less platelet activation and leukocyte-plate let aggregation than uncoated stainless steel stents of the same length and shorter stents of the same structure. Stent surface coating and texture pl ays a role in platelet and leukocyte activation and leukocyte-platelet aggr egation. Using this simple in vitro assay and whole blood and flow cytometr y, it seems possible to differentiate stents by their potency to activate p latelets and/or leukocytes. This assay could be applied for improving the b iocompatibility of coronary stents. Cytometry (Comm, Clin. Cytometry) 38:30 -39, 1999, (C) 1999 Wiley-Liss, Inc.