Analysis of morphology of platelet aggregates formed on collagen under laminar blood flow.
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 (100 s(-1)) generated small, circular platelet deposits, whereas elevated arterial shear rates (500 and 1000 s(-1)) generated platelet masses elongated twofold in the direction of flow. At 2000 s(-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 (1000 s(-1)) for 5 min, we identified a twofold increase in aggregate size (81.5 ± 24.6 μm; p < 0.1) and a threefold increase in growth rate parallel to the flow (0.40 ± 0.09 μm/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.
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Department of Chemical and Biomolecular Engineering, Institute for Medicine and Engineering, 1024 Vagelos Research Laboratories, University of Pennsylvania, Philadelphia, PA 19104, USA.
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D001783:Blood Flow Velocity; D001792:Blood Platelets / Q000166:cytology* / Q000502:physiology*; D048429:Cell Size; D002478:Cells, Cultured; D003094:Collagen / Q000378:metabolism*; D006801:Humans; D040542:Mechanotransduction, Cellular / Q000502:physiology*; D010974:Platelet Aggregation / Q000502:physiology*
D003094:Collagen