Platelet Shape Changes and Adhesion Under High Shear Flow

Abstract

Recent studies have revealed that the platelet adhesive process under flow is tightly regulated by multiple ligand-receptor interactions. However, platelet morphological changes during this process, particularly its physiological relevance, remain unknown under blood flow conditions. Using epifluorescence and scanning electron microscopy, we evaluated the real-time changes in platelet morphology during a platelet adhesive process on a von Willebrand factor-coated surface under physiological high shear flow in a perfusion chamber. Here, we show that dynamic platelet shape changes occurring during distinct phases of the adhesive process are precisely regulated by "inside-out" and "outside-in" integrin signals and are also a key regulatory element in successful platelet thrombogenesis opposing rapid blood flow in vivo.

Identification of a 2-stage platelet aggregation process mediating shear-dependent thrombus formation

“…[14][15][16] To examine which of these morphologies is most relevant to thrombus growth in vivo, we established a high-magnification DIC imaging technique that has sufficient optical resolution to identify the morphology of individual platelets in the rat microcirculation (refer to Videos S1-S6 [available on the Blood website; see the Supplemental Materials link at the top of the online article], videos examining platelet thrombus formation in vivo, for full appreciation of the dynamics of platelet aggregation). Vascular injury of mesenteric arterioles was induced by photoactivation of systemically administered rose bengal, a technique that induces vascular injury leading to the development of small nonocclusive thrombi.…”

Mural thrombus generation in type 2A and 2B von Willebrand disease under flow conditions

“…[17][18][19] Whole blood containing mepacrine-labeled platelets was aspirated through the chamber by a syringe pump (model CFV-3200, Nihon Kohden, Tokyo, Japan) at a constant flow in a 37°C thermostatic air bath (model UI-50, Iuchi, Osaka, Japan). [19][20][21][22] Unless otherwise indicated, the entire thrombus generation process, from initial platelet-surface interaction to platelet aggregate accumulation on the surface, was observed in real time at positions of the flow chamber corresponding to 50 s Ϫ1 and 1500 s Ϫ1 and recorded with a videocassette recorder (Hi8 VIEWCAM, Sharp, Osaka, Japan). [19][20][21][22] The wall shear rate of 50 s Ϫ1 or 1500 s Ϫ1 is considered to be a typical low or high shear flow, respectively.…”

“…[19][20][21][22] Unless otherwise indicated, the entire thrombus generation process, from initial platelet-surface interaction to platelet aggregate accumulation on the surface, was observed in real time at positions of the flow chamber corresponding to 50 s Ϫ1 and 1500 s Ϫ1 and recorded with a videocassette recorder (Hi8 VIEWCAM, Sharp, Osaka, Japan). [19][20][21][22] The wall shear rate of 50 s Ϫ1 or 1500 s Ϫ1 is considered to be a typical low or high shear flow, respectively. 17,19,21 In some experiments, perfusion with higher wall shear rates was also performed by changing flow rate.…”

Distinct and concerted functions of von Willebrand factor and fibrinogen in mural thrombus growth under high shear flow

“…25,26 The chamber was assembled and mounted on a microscope (BX60; Olympus, Tokyo, Japan) equipped with epifluorescent illumination (BX-FLA; Olympus) and a charge-coupled device (CCD) camera system (U-VPT-N; Olympus) as described. 11,12,24,25 Whole blood containing mepacrine-labeled platelets was aspirated through the chamber by a syringe pump (Model CFV-3200, Nihon Kohden, Tokyo, Japan) at a constant flow rate of 0.285 mL per minute, producing a wall shear rate of 1500 s Ϫ1 at 37°C in a thermostatic air bath (Model UI-50, Iuchi, Osaka, Japan).…”