A Measure of Platelet Activation and Aggregation Across Two Flow Regimes to Minimize Thromboembolic Events in Blood Pumps

Open Access
- Author:
- Sturgis, Hannah
- Area of Honors:
- Biology
- Degree:
- Bachelor of Science
- Document Type:
- Thesis
- Thesis Supervisors:
- Keefe B Manning, Thesis Supervisor
Benoit A Dayrat, Thesis Honors Advisor - Keywords:
- thrombosis
flow cytometry
platelet activation
gel-filtered platelets
aggregation - Abstract:
- Cardiovascular disease (CVD) is the leading cause of death for men and women in the United States. The significant number of individuals suffering from CVD has created a clinical need for mechanical blood pumps that provide numerous benefits and life-saving solutions to patients. Despite these advantages, however, their function is burdened by thromboembolic complications due to the non-physiologic blood flow patterns induced by device geometries. The present study modeled platelet activation resulting from dynamic stress conditions in blood pumping devices. Human blood samples were centrifuged to obtain platelet-rich plasma and filtered on a gel column to purify the platelets from plasma proteins. The resulting gel-filtered platelets (GFP) were then subjected to constant low and high shear stress conditions at 60 rpm with a Reynolds number of 900, and 4000 rpm with a Reynolds number of 5000, respectively, induced by a cylindrical rheometer consisting of a 2.4 cm diameter titanium cylinder submerged in a cylindrical vessel. Experiments were run for 30 minutes, and a GFP sample was collected from the vessel every five minutes during rotation to measure platelet activation. Samples of the whole blood, PRP, and GFP were collected and stained with CD62P and CD61 to be analyzed for platelet activation using a BD LSR-Fortessa Flow Cytometer. The average GFP activation at 4000 rpm at zero minutes (t=0) was 3.59%. After five minutes of rotation (t=5), platelet activation significantly increased to 12.10%. There was no significant increase in activation from t=5 through t=30. Data at 60 rpm showed no significant increase in activation throughout the 30 minutes of stress exposure. Platelet aggregation for the GFP exposed to high shear stress conditions was also measured using CD61 and APC stains for flow cytometry analysis. No significant increase in platelet aggregation were found in the GFP samples exposed to high shear stress conditions. The findings from this study provide insight into platelet activation upon exposure to shear stress, independent of plasma protein activation agonists, and can be incorporated into a computational model to optimize the geometry and flow patterns induced by blood recirculating devices.