Abstract 512: Validating An Ex Vivo System To Study Human Platelet Biomechanical Activation

Background: Arterial blood flow becomes turbulent in areas of stenosis, ectasia, or aneurysm. Platelets are exquisitely sensitive to external mechanical forces. Evaluating biomechanical platelet activation would provide insight into a new class of antiplatelet medications Aims: Manufactured flow cones were utilized to model smooth (S-Flow) and disturbed (D-flow) flow patterns under different conditions. Platelet activation was assessed by alpha granule exocytosis or changes in expression of known platelet surface mechanoreceptors. Methods: Using bespoke cones driven by a magnetic field, we constructed models based on cone dimensions to estimate platelet exposure to fluid mechanical stress by numerically simulating the flow patterns, then calculating Von Mises stress at each point under flow. Expression of platelet surface P-selectin, Glycoprotein VI (GPVI), Glycoprotein 1bα (GP1bα), and activated Glycoprotein IIb/IIIa (GPIIb/IIIa) was assessed by FACS using labeled antibodies as mean fluorescence intensity (MFI) before/after S-flow and D-flow at 400 rpm or 400 rpm for 90 mins. [PF4] in platelet releaseate was evaluated by ELISA. Results: Preliminary results suggest that platelet Von Mises stress computed for D-flow conditions by sculpted cones was within range of estimated stress in an ectatic carotid artery. S-flow exposure ex vivo did not significantly activate platelets, release of PF4, or P-selectin. D-flow, conversely, increased platelet surface p-selectin (MFI 162+/-58 vs. 550+/-144, P=0.018) but decreased GP1bα (MFI 16724+/-1720 vs. 11948+/-1036, P=0.03). PF4 was detected in platelet releasate in concentrations proportional to increasing orders of magnitude D-flow Conclusions: We hereby show a reproducible system to detect biomechanical platelet activation in D-flow environments ex vivo that will allow for platelet-derived biomarker discovery during D-flow stress and assessment of new anti-platelet therapeutics.