Influence of leukocyte adhesion on partitioning of healthy and diabetic red blood cells at vascular bifurcations.

Hemorheological changes associated with diabetes include alteration in red blood cell (RBC) deformability, shape, and volume, and an increased number of adhered leukocytes (white blood cells [WBCs]). How such changes affect RBC distribution in capillary vessel networks is not fully known. Here, we undertake a 3D high-fidelity computational study of diabetic and healthy RBC partitioning in vascular bifurcations without and with an adherent WBC. We predict that without a WBC, the difference between healthy and diabetic RBC partitioning is small but subtle. While both exhibit disproportionate but regular partitioning, the sigmoid curves depicting diabetic RBCs could become concave-up. An adherent WBC is shown to cause significant asymmetry with RBCs, exhibiting reverse partitioning when it is located closer to the flow-dominant branch and highly disproportionate regular partitioning when it is located closer to the non-dominant branch. The effect of a WBC is more pronounced on diabetic RBCs. Using numerical data and a reduced-order theoretical model, it is found that such asymmetry in RBC partitioning strikingly differs from WBC-induced asymmetry in the flow-rate partitioning-the adhesion of a WBC is shown to increase the flow fraction in the flow-dominant daughter vessel. Interesting differences are also predicted for time-dependent partitioning: Without the WBC, partitioning data of healthy cells show more temporal scatter than for diabetic cells. This trend is then reversed and increased by severalfold with the WBC present. Physical mechanisms underlying these differences are elucidated using diabetic and healthy RBC flow patterns and their interaction with the WBC. Additionally, we predict that the presence of a WBC can cause flow reversal in the non-dominant branch for certain pressure conditions, a phenomenon not observed without the WBC.