human hrm  (Jena Bioscience)

Journal: Nature medicine

Article Title: Macrophages support pathological erythropoiesis in Polycythemia Vera and Beta-Thalassemia

doi: 10.1038/nm.3126

Figure Lengend Snippet: ( a ) During steady state erythropoiesis macrophages mildly support erythroid development but play a crucial function in maintenance of serum iron availability by controlling hepcidin expression and iron recycling from senescent red cells. Upon macrophage depletion (right panel), erythropoiesis is only slightly reduced, not significantly decreasing RBC production. However, iron metabolism is impaired, leading to low iron availability, reduced hemoglobin synthesis and low MCH. Anemia arises as a consequence of low MCH. ( b ) Model that describes the (iron-independent) Stress Erythropoiesis Macrophage-supporting Activity (SEMA) under conditions of elevated erythropoiesis associated with anemia, Epo administration or Polycythemia vera due to the Jak2 V617F mutation. Under these conditions, SEMA supports erythropoiesis, functioning as a complement to EpoR/Jak2/Stat activation. This allows for a high reticulocytosis and RBC production (left panel). If SEMA is abrogated, erythroid expansion is markedly impaired leading to low reticulocytosis (right panel). Moreover iron availability is also decreased further contributing for impaired erythroid response. While the function of macrophages might be crucial during recovery from anemia, it seems to play a decisive role for the pathophysiology of Polycythemia vera, contributing for high erythrocytosis. ( c ) Contribution of macrophages to the pathophysiology of β-thalassemia. In β-thalassemia, erythropoiesis is characterized by increased erythroid proliferation and decreased differentiation, which is SEMA dependent (left panel). Absence of macrophages leads to improvement of erythropoiesis by decreasing the proliferation and improving the differentiation of erythroid progenitors (right panel). As macrophage depletion is protracted overtime by repeated administration of clodronate, erythroid iron availability decreases, further contributing for the phenotypic improvement of β-thalassemic RBCs. ( d ) Model representing how macrophages support stress erythropoiesis in the erythroblastic island. EBs adhere to macrophages via different adhesion molecules and these adhesive interactions, along with additional macrophage-secreted factors, activate downstream signaling promoting EB survival, proliferation and controlling differentiation (SEMA activity). In addition, complete support of stress erythropoiesis and hemoglobin synthesis requires Epo and iron, the last one provided by the macrophages by recycling iron from senescent RBCs. Peripheral blood (PB), bone marrow (BM), Spleen (Spl), Liver (Liv), serum iron (SI) Hepcidin (Hpc), erythroid factor (EF) and iron recycling (Fe Rec) are shown as abbreviations in the panels a–c. In a–c erythroid maturation is shown by the connecting lines between each erythopoietic stage, up to RBC in the peripheral blood. Dashed lines represent failure in erythroid differentiation. Arrow stroke represents intensity of each effect (dashed arrows being the lowest).

Article Snippet: CD34 negative PBMCs were resuspended in RPMI complete (RPMI, 10% FBS, 100 μg mL of streptomycin, 100 U ml −1 penicillin) supplemented with 10 ng ml −1 of human recombinant macrophage colony stimulation factor (hrM-CSF, Peprotech, Rocky Hill, NJ) at 3×10 6 cells ml −1 .

Techniques: Expressing, Activity Assay, Mutagenesis, Activation Assay, Adhesive