Shear-Induced Platelet Activation and Platelet Microparticle Formation at Blood Flow Conditions as in Arteries With a Severe Stenosis

Abstract

In the present study, we investigated whether high arterial shear stresses at various exposure times or a sudden increase in shear stress introduced by a stenosis affect platelet activation and platelet microparticle formation in native human blood. We used a parallel-plate perfusion chamber device through which nonanticoagulated human blood was drawn (10 mL/min) by a pump directly from an antecubital vein through the flow channel of a perfusion chamber at wall shear rates of 420, 2600, and 10500 s-1. In another set of experiments, an eccentric stenosis was introduced into the flow channel. Wall shear rates of 2600 or 10500 s-1 at the stenosis apex were maintained at the same flow rate. The wall shear rate upstream and downstream of these stenoses was 420 s-1. A shear rate of 420 s-1 is within the range of those encountered in healthy small coronary arteries, whereas those of 2600 and 10500 s-1 are representative for vessels with various degrees of stenotic lesions. The blood was exposed to these shear rates for periods varying from 0.075 to 3.045 seconds. Platelet activation was assessed as activated glycoprotein (GP) IIb/IIIa by FITC-labeled monoclonal antibody (MAb) PAC-1 and aminophospholipid translocation by FITC-labeled annexin V. Microparticle formation was quantified by FITC-labeled MAb Y2/51 directed against GP IIIa. Significant platelet activation and formation of microparticles were observed at 10500 s-1 only (P < .008). This shear-induced platelet activation and microparticle formation were enhanced by introduction of a thrombus-promoting surface consisting of type III human collagen fibrils. Introduction of the most severe stenosis at 10500 s-1 further increased platelet activation (P < .017). The collagen-induced thrombus formation increased the platelet thrombus volume at 10500 s-1 from 16.5 to 33.8 microns3/microns2 (P < .003) on the stenosis apex when the most severe stenosis was used. A correlation (P < .0001) between platelet thrombus volume and platelet microparticle formation was observed in the presence of the eccentric stenoses. Apparently, high shear stress (315 dynes/cm2 at 10500 s-1), as encountered in severe atherosclerotic arteries, activated platelets and triggered platelet microparticle formation. In contrast, no significant platelet activation or formation of platelet microparticles was observed at physiological shear (420 s-1) or at the shear condition simulating shear in arteries with a less severe stenosis (2600 s-1). The data imply that platelets are activated and form microparticles in native blood at very high shear stresses. These events are potentiated by prolonged exposure to the high shear or by a sudden change of increasing shear due to the stenosis. The latter situation apparently enhances platelet thrombus formation at the stenosis.

Shear‐induced platelet aggregation increases in patients with proximal and severe coronary artery stenosis

“…Although it has been reported that shear stress causes activation of the platelet glycoprotein GPIIb-IIIa, 7 the effect of shear stress on GPIIb-IIIa could not be evaluated in the present study, since we did not measure GPIIb-IIIa activity. Instead, we measured ␤-thromboglobulin and platelet factor 4, which are constituents of the ␣-granule, as markers of platelet secretion.…”

“…[1][2][3][4][5][6] Shear stress has been considered an important promoter of adhesion and cohesion of platelets to endothelial cells activated by atherosclerosis. 7 The shear stress generated when blood flows through a vessel increases as blood flows rapidly through a stenosed artery, 8 which accelerates thrombus formation by activating platelets and inducing platelet adhesion and aggregation. [8][9][10] Most studies of platelet function, coagulation, and fibrinolysis in patients with ischemic heart disease have focused on acute coronary syndromes.…”

Platelet Microvesicles (Microparticles) in Cardiac Surgery

“…Due to the sub-micron size of PMV, they may be able to withstand extreme shear stress, remaining in position to encourage further thrombus formation on extra-corporeal surfaces. 68 …”

Platelet Activation in Cats with Hypertrophic Cardiomyopathy

“…When considering the association of heart disease and platelet activation, an enlarged left atrium, endothelial damage, and the presence of mitral regurgitation all have the potential to generate high shear, resulting in platelet up‐regulation, release of alpha granule components, and increased sensitivity to agonists 15, 16. In vitro studies by Holme et al17 demonstrated shear‐induced platelet activation and development of platelet microparticles under flow conditions that may be similar to those associated with diastolic dysfunction in cats with HCM as suggested by Bedard et al 18…”