Abstract
In a focal injury model, platelets adhere and activate under flow on a collagen-coated surface, creating a field of individual platelet aggregates. These aggregates exhibit distinct structural characteristics that are linked to the local flow conditions. By combining image analysis techniques and epifluorescence microscopy, we developed a robust strategy for quantifying the characteristic instantaneous width and length of a growing platelet deposit. We have confirmed the technique using model images consisting of ellipsoid objects and quantified the shear rate-dependent nature of aggregate morphology. Venous wall shear rate conditions (100s(-1)) generated small, circular platelet deposits, whereas elevated arterial shear rates (500 and 1000s(-1)) generated platelet masses elongated twofold in the direction of flow. At 2000s(-1), an important regime for von Willebrand Factor (vWF)-mediated recruitment, we observed sporadic platelet capture events on collagen that led to rapidly growing deposits. Furthermore, inter-donor differences were investigated with respect to aggregate growth rate. After perfusion at elevated shear rates (1000s(-1)) for 5min, we identified a twofold increase in aggregate size (81.5±24.6μm; p<0.1) and a threefold increase in growth rate parallel to the flow (0.40±0.09μm/s; p<0.01) for an individual donor. Suspecting a role for vWF, we found that this donor had a twofold increase in soluble vWF relative to the other donors and pooled plasma. Microfluidic devices in combination with automated morphology analysis offer new tools for characterizing clot development under flow.
Published Version
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