Thrombi Produced in Stagnation Point Flows Have a Core–Shell Structure
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In regions of flow separation/reattachment within diseased arteries, the local hemodynamics can result in stagnation point flow that provides an atypical environment in atherosclerosis. Impinging flows occur with recirculation eddies distal of coronary stenosis or diseased carotid bifurcations.
By perfusing whole blood directly perpendicular to a fibrillar collagen thrombotic surface, a microfluidic device produced a stagnation point flow. Side view visualization of thrombosis in this assay allowed for observation of clot structure and composition at various flow rates and blood biochemistry conditions.
For clotting over collagen/tissue factor surfaces, platelet thrombi formed in this device displayed a core–shell architecture with a fibrin-rich, platelet P-selectin-positive core and an outer platelet P-selectin-negative shell. VWF was detected in clots at low and high shear, but when N-acetylcysteine was added to the whole blood, both platelet and VWF deposition were markedly decreased at either low or high flow. To further examine the source of clot stability, 1 mM GPRP was added to prevent fibrin formation while allowing the PAR1/4-cleaving activity of thrombin to progress. The inhibition of fibrin polymerization did not change the overall structure of the clots, demonstrating the stability of these clots without fibrin.
Impinging flow microfluidics generate thrombi with a core–shell structure.
KeywordsPlatelet Shear stress von Willebrand factor
B.A. Herbig designed and performed the experiments, analyzed data, and contributed to the manuscript. S.L. Diamond designed the research, analyzed data, and contributed to the manuscript. This work was supported by NIH predoctoral training Grant 5T32HL007954-15 (B.A.H.) and NIH R01 HL103419 (S.L.D.).
Conflicts of interest
The authors declare that they have no conflicts of interest.
All human subjects research was carried out in accordance with University of Pennsylvania guidelines and approved by the university’s Internal Review Board. All procedures followed were in accordance with the ethical standards of the responsible committee on human experimentation (institutional and national) and with the Helsinki Declaration of 1975, as revised in 2000 (5). Informed consent was obtained from all donors included in the study. No animal studies were carried out by the authors for this article.
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