• The activation of platelet by the combined effects of erythrocyte fragments and shear stress is not simply additive. Although, these two factors together have a larger accumulative effect on platelets that causes greater platelet activation.

• Platelet activation increases linearly once a minimum threshold of shear is met.

• Further characterization is necessary to lower the standard variation between samples and increase the number of shear stresses applied to create a clearer picture of activation.

• Whole blood was acquired according to IRB approved protocol and gel-filtered to isolate platelets.

• Erythrocyte membrane fragments were formed by washing erythrocytes a hypotonic solution of PBS, bursting the cells to form fragments. The solution was centrifuged to remove the hemoglobin.

• Platelets with erythrocyte fragments were sheared using a platelet hammer designed to generate a

hypershear stress.• Platelet activation of the sheared platelets was compared to that of platelet activation in a static conditions. The platelets were incubated during the shear process. • Platelet activation was determined by running a Platelet Activation Status (PAS) assay.

Erythrocyte Fragment-Induced Platelet Activation Under Shear Conditions Samuel Dunn1, Jennifer Barton1,Phat L. Tran1,2, M.G. Pietropaolo3,Marvin J. Slepian1,2

1Department of Biomedical Engineering, 2Department of Medicine,3Politecnico di Milano, Milano, Italy

The University of Arizona, NIH Summer Clinical Immersion

Acknowledgements

• The total artificial heart (TAH) and ventricular assist devices (VAD) are mechanical devices used as bridge-to-transplant or destination therapies when patients’ have advanced heart failure.

• Flow conditions generate shear stress that can causes hemolysis of erythrocytes. When erythrocytes are hemolyzed, membrane fragments are generated and these membrane fragments cause platelet activation.1

• When a sustained shear stress is acts on platelets, there is an accumulative effect that activates platelets once a minimum threshold is reached2.

• RBC fragments, ghosts and released contents will activate platelet and may potentiate device thrombosis.

Introduction

Methods

References

Results

Conclusion and Future Direction

Partial support was provided by the National Institutes of Health/National Institute for Biomedical Imaging and Bioengineering, 1R25EB012973.

1. Deutsch, Steven, John M. Tarbell, Keefe B. Manning, Gerson Rosenberg, and Arnold A. Fontaine. "Experimental Fluid Mechanics Of Pulsatile Artificial Blood Pumps." Annual Review of Fluid Mechanics 38.1 (2006): 65-86. Print.

2. Sheriff, Jawaad, Danny Bluestein, Gaurav Girdhar, and Jolyon Jesty. "High-Shear Stress Sensitizes Platelets to Subsequent Low-Shear Conditions." Annals of Biomedical Engineering 38.4 (2010): 1442-1450. Print.

SEM Images

DC

B

• Lower shear stresses show that the activation from the control is on par with the activation of the platelets under shear.

• At 800 dynes/cm^2, the activation of platelets from the platelet hammer begin to increase as the shear force is approaching levels of significant platelet activation.

• At stresses of 1000 and 1200 dynes/cm ^2, the platelet activation of the sheared platelets have a significant activation difference compared to the control.

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RBC Fragment-Induced Enhancement of Platelet Activation Under VAD Shear