Erythrocyte aggregation in sudden flow arrest is linked to hyperthermia, hypoxemia, and band 3 availability

Background: Erythrocyte aggregation is a phenomenon that is commonly found in several pathological disease states: stroke, myocardial infarction, thermal burn injury, and COVID-19. Erythrocyte aggregation is characterized by rouleaux, closely packed stacks of cells, forming three-dimensional structures. Healthy blood flow monodisperses the red blood cells (RBCs) throughout the vasculature; however, in select pathological conditions, involving hyperthermia and hypoxemia, rouleaux formation remains and results in occlusion of microvessels with decreased perfusion. Objectives: Our objective is to address the kinetics of rouleaux formation with sudden cessation of flow in variable temperature and oxygen conditions. Methods: RBCs used in this in vitro system were obtained from healthy human donors. Using a vertical stop-flow system aligned with a microscope, images were acquired and analyzed for increased variation in grayscale to indicate increased aggregation. The onset of aggregation after sudden cessation of flow was determined at proscribed temperatures (37–49°C) and oxygen (0%, 10%), and in the presence and absence of 4, 4′-Diisothiocyano-2,2′-stilbenedisulfonic acid (DIDS). Both autologous and homologous plasma were tested. Results: RBCs in autologous plasma aggregate faster and with a higher magnitude with both hyperthermia and hypoxemia. Preventing deoxyhemoglobin from binding to band 3 with DIDS (dissociates the cytoskeleton from the membrane) fully blocks aggregation. Further, RBC aggregation magnitude is greater in autologous plasma. Conclusions: We show that the C-terminal domain of band 3 plays a pivotal role in RBC aggregation. Further, aggregation is enhanced by hyperthermia and hypoxemia.