Effects of riboflavin and ultraviolet light treatment on platelet thrombus formation and thrombus stability on collagen

BACKGROUND Pathogen reduction technologies (PRTs) are considered for the implementation of safer platelet (PLT) transfusion. PRT treatment involves the addition of a photosensitizer to a blood component followed by ultraviolet (UV) light irradiation. However, the effects of PRT treatment on PLT thrombus formation and thrombus stability have not been satisfactorily clarified. STUDY DESIGN AND METHODS Leukoreduced PLT concentrates (PCs) were treated with riboflavin and UV light (Mirasol PRT). PLT thrombus formation on collagen was evaluated by the microchannel method, by which the total amount of PLTs deposited was measured as indices of thrombus formation and thrombus stability. Using a cone‐plate shear‐induced PLT aggregometer, PLT reactivity in blood flow was examined in a wide range of shear stresses of 6 to 108 dyn/cm2. RESULTS There was no significant difference in surface coverage between PRT‐treated PLTs and control PLTs on collagen. On the other hand, the total amount of PRT‐treated PLTs deposited was higher than that of control PLTs. The promotive effect of PRT treatment on PLT deposition completely disappeared in the presence of tirofiban, a potent integrin αIIbβ3 inhibitor. The percentage of the dissociation of PRT‐treated PLTs on collagen was lower than that of control PLTs after flushing with phosphate‐buffered saline. PRT treatment significantly inhibited PLT aggregation under high‐shear‐stress conditions. CONCLUSION Riboflavin‐based PRT treatment of PCs leads to the enhancement of PLT thrombus formation and thrombus stability on collagen. However, it does not enhance the reactivity of PLTs not in contact with collagen under high‐shear‐stress conditions.