Macrophages Mediate the Clearance of Hyperosmotic Fragile Erythrocytes in High Altitude Polycythemia

To investigate the changes in erythrocyte osmotic fragility leading to hemolysis and the enhanced phagocytosis of erythrocytes by macrophages in high-altitude polycythemia. Patients with high-altitude polycythemia and healthy volunteers were prospectively enrolled in the Affiliated Hospital of Qinghai University from 2020 to 2022. The number of red blood cells, hemoglobin concentration, bilirubin, unsaturated iron binding capacity, and free hemoglobin were detected to confirm the existence of hemolysis in high-altitude polycythemia. A rodent model of high-altitude polycythemia was constructed, and osmotic fragility tests were performed to detect the osmotic fragility of red blood cells. Flow cytometry, immunohistochemistry, and hematoxylin-eosin staining (HE staining) were used to identify the phagocytic ability of macrophages in the liver and spleen of the animal model to further clarify the mechanism of hemolysis. Patients and animal models of high-altitude polycythemia show increased osmotic fragility of erythrocytes in peripheral blood, leading to hemolysis, and increased compensatory macrophages in the liver and spleen.