Figure 3.
idRBC Subpopulations of increased stiffness and smaller size demonstrate increased margination and local wall shear stress fluctuations in computational simulations
(A) Angled (left) with side and cross-sectional (right) views of snapshots taken from a computational simulation of a binary suspension of RBCs with a majority population of large and deformable healthy RBCs (red) with a minority population of smaller and less deformable idRBCs (blue). This suspension is designed to mimic the heterogeneity observed in IDA and was then compared to a uniform suspension containing only healthy RBCs. In reality, an idRBC population exhibits a range in cell stiffness (normal to increased) and size (normal to microcytic), but for the purposes of these simulations, “idRBCs” comprise only the microcytic and stiff subpopulation to allow for tracking the margination of that RBC subpopulation and the subsequent shear stresses those cells induce at the vessel wall.
(B) Steady-state radial hematocrit profiles (Ht) for healthy RBCs (blue) and idRBCs (red). The x axis depicts distance from the center of the channel scaled with the radius of a healthy RBC, with 0 being the center of the channel and 3.1 representing the channel walls. idRBCs significantly marginate and travel in higher percentages close to channel walls, whereas RBCs of normal size and stiffness concentrate around the center of the channel.
(C) Snapshot of the spatial distribution of additional wall shear stress induced by healthy RBC (left) and idRBC (right) suspensions, respectively. Red regions indicate large fluctuations and are more numerous in the presence of idRBCs.
(D) Probability density (left) of excess wall shear stress induced by healthy RBCs only (blue), the binary suspensions with the number fraction of idRBCs being 0.1 (light blue) and 0.2 (yellow), and idRBCs only (red). The idRBC suspension created excess large fluctuations in wall shear stress in comparison to the healthy RBCs. The ratio between probability densities (right) show that large positive fluctuations in wall shear stress are an order of magnitude more likely in the presence of idRBCs than without them, meaning that even a small number of idRBCs can create a high relative probability of large stress fluctuations.