Artificial surface effect on red blood cells and platelets in laminar shear flow

Area of Science:

• Biomedical Engineering
• Hematology
• Fluid Mechanics

Background:

• Platelet adhesion and aggregation are critical in hemostasis and thrombosis.
• The role of red blood cells (RBCs) in modulating platelet function under shear stress is not fully understood.
• Understanding these interactions is crucial for evaluating blood-contacting biomaterials.

Purpose of the Study:

• To investigate the effects of red blood cells (RBCs) on platelet adhesion and aggregation.
• To quantify the contribution of RBCs to adenosine diphosphate (ADP) and hemoglobin (Hb) release under shear flow.
• To determine the influence of hematocrit on RBC-mediated platelet activation.

Main Methods:

• Experiments were conducted using a cone-and-plate (CP) viscometer to simulate laminar shear flow.
• Measurements included hemoglobin (Hb) and adenosine diphosphate (ADP) release, platelet reduction in bulk, and surface coverage.
• Tests were performed on whole blood, RBC ghosts in platelet-rich plasma (PRP), and RBCs in PRP or platelet-poor plasma across various shear rates and hematocrits.

Main Results:

• Low-stress shearing induced ADP and Hb release from intact RBCs.
• RBC-derived ADP release was approximately double that of platelets and significantly contributed to platelet reduction and adhesion.
• Above a hematocrit of 25%-35%, RBCs in PRP showed a greater contribution to ADP release, platelet adhesion, and aggregation than platelets alone.

Conclusions:

• RBCs play a substantial role in promoting platelet adhesion and aggregation under shear flow, primarily through ADP release.
• The contribution of RBCs to platelet activation increases significantly with hematocrit.
• RBCs are a critical factor in platelet-surface interactions, particularly in whole blood under flow conditions.