(607h) The Effect of Rigid Red Blood Cells on Platelet Margination and Adhesion in Flow

Introduction: Thrombocytes, more often referred to as platelets, are a key component of blood whose primary function is to maintain hemostasis by rapidly plugging any interruptions in the vasculature, a process known as clotting. Clotting is key to the physiological response to vascular injury, preventing excessive blood loss, permanent damage, and even death. Clotting begins with damage to the endothelium, causing platelets to activate and bind to the endothelial cells or underlying exposed extracellular matrix proteins. Platelet margination and binding to the vascular wall is promoted through hemodynamic, heterogenous collisions between cellular components, including deformable red blood cells (RBCs) in the RBC core. However, RBCs can undergo membrane rigidity in blood-related diseases, such as malaria and sickle cell disease (SCD). Experimental research has shown that artificially rigidified RBCs lead to an expanded RBC core and significantly impact white blood cell (WBC) adhesion to the endothelium. Despite the increase in vaso-occlusive crises and stroke in SCD patients, little experimental work exists to fully elucidate the effect of rigid RBCs on platelet margination and binding in vessels.

Materials and Methods: We utilize an in vitro flow-based system to examine how the extent of rigidification and rigid RBC concentration effect platelet margination and binding to a damaged endothelium model mimicking acute vascular damage. RBCs are removed from the whole blood and artificially rigidified using a peroxide solution. The RBCs are then reconstituted into blood and perfused over an activated, damaged endothelium using a parallel plate flow chamber (PPFC). Platelet adhesion is quantified and compared to adhesion in a healthy, non-rigid control. The ability of artificially rigidified RBCs to activate resting platelets is quantified using flow cytometry to analyze upregulation of inflammatory markers.

Results and Conclusions: The presence of rigid RBCs in flow drastically increases platelet adhesion under specific rigidities and concentrations. This finding suggests that rigid RBCs may play a major role in disrupting normal hemodynamics and contributing to the pervasive vaso-occlusive crises that occur in many SCD patients. Overall, we will elucidate how rigid RBC-platelet interactions affect platelet binding, a critical step in hemostasis. This study can help determine the mechanism causing vaso-occlusive events in SCD patients and can form the basis of the study of platelet-cell dynamics in the future.