Photodynamic therapy (
PDT) produces reactive species that alter vascular wall biology and vessel wall
proteins. In this study, we examined platelet adhesion to
PDT-treated (
photosensitizer =
Photofrin; fluence 100 J/cm2; lambda = 630 nm) extracellular matrix (ECM),
fibrinogen,
von Willebrand factor (vWF) and
collagen Types I and III, under flow conditions in a recirculating perfusion chamber. Platelet adhesion was quantified by image analysis. The effect of
PDT on vWF was assessed by measuring the binding of domain-specific
antibodies to treated vWF.
PDT significantly decreased platelet adhesion to the ECM,
fibrinogen and vWF. However,
PDT of
collagen resulted in significantly increased platelet adhesion, with large aggregate formation.
PDT affected mostly the A1 (
glycoprotein [GP]-Ib-binding site), A2 and A3 (
collagen-binding site) domains of vWF but not the D'-D3 (
factor VIII-binding site) and B-C1 (
GP-IIb/IIIa-binding site) domains. In conclusion,
PDT can alter the ECM, resulting in decreased platelet adhesion. However, vessels with high
collagen content, such as veins and small arteries, may become increasingly prone to
thrombosis. The results of this study may thus play a role in understanding the thrombogenic properties and mechanisms of vascular
PDT.