Cell Distributions and Segregation During Blood Flow within Straight and Serpentine Vascular Geometries in Sickle Cell Disease and Iron Deficiency Anemia

The spatial distribution of different cellular components of blood is nontrivial. Red blood cells (RBCs) migrate toward vessel center leaving RBC-depleted cell-free layer (CFL) near walls, while white blood cells and platelets reside in the CFL, a flow-induced segregation called margination. The margination may have significance in some blood diseases, such as sickle cell disease (SCD) and iron deficiency anemia (IDA). A complication of SCD is chronic vasculopathy, in which endothelial cells are pro-inflammatory in the circulation. One might hypothesize that diseased cells marginate, residing in CFL, and generating physical interactions that damage endothelium.

 

We study hematocrit distribution for mixtures of healthy and iron deficiency RBCs (idRBCs) using an immersed boundary method. We find that smaller and stiffer idRBCs strongly marginate, while healthy RBCs enrich around channel center, indicating differences in size and deformability are sufficient to drive segregation. We find idRBCs close to walls causing aberrant shear stresses leads to increased vascular inflammation. Similar observations arise for mixtures of healthy and irreversibly sickled cells. We also study the effects of geometric complexities of vessels, such as curvature, on cell distribution and margination.