The term CFU-E (Colony Forming Unit-Erythroid [1] ) denotes a hematopoietic stem cell in the bone marrow which eventually matures into a red blood cell (also called an erythroid cell). It arises from CFU-GEMM (via BFU-E, [2] which stands for "erythroid burst-forming units" [3] ) and gives rise to proerythroblasts.
CFU-E is a stage of erythroid development between the BFU-E stage and the pro-erythroblast stage. CFU-E colony assay is designed to detect how many colony-forming-units of erythroid lineage there are in a hematopoietic tissue (bone marrow, spleen, or fetal liver), which may be reflective of the organism’s demand for oxygen delivery to the tissues or a hematopoietic disorder.
Early erythroid progenitors are found at a quite low frequency relative to later stages of erythroid differentiation, such as the pro-erythroblast and the basophilic erythroblast stages which can be detected by flowcytometry directly ex-vivo. [4] Furthermore, unlike for the pro-erythroblast and later stages of erythroid development, no truly reliable and unique positive flow-cytometric markers exist, though it is possible to use negative exclusion markers to deplete a cell population of other precursors and differentiated cells by cell sorting, thus greatly enriching it for the CFU-E activity. [5] CFU-E cells express Epo receptor, c-Kit (Stem cell factor receptor), transferrin receptor (CD71+), and are Ter119(glycophorin-A associated antigen)-negative. For the above reasons, the CFU-E assay, as inefficient and variable as it can often be, is still in use today.
Cells at the CFU-E stage express some erythropoietin receptor (EpoR), and thus can be induced to terminally differentiate in vitro in 2–3 days in the presence of only erythropoietin (Epo) (together with the basic contents of culture media: FBS, BSA in IMDM). Methylcellulose is a semisolid media additive that allows an investigator to stain (with diaminobenzidine reagent for hemoglobin) and then count individual colonies, each arising from a single plated progenitor that is at the CFU-E stage. By day 2 from the time of plating, each CFU-E colony will contain between 8 (minimum) and 64 hemoglobinized cells most of which are in their end-stage of erythroid differentiation. It is possible to see a small spectrum of hemoglobinization level and possibly cell size, indicating that some cells in the colony have achieved the end-stage faster than others.
Cell number in a colony is important because pro-erythroblast stage is also Epo-responsive (expresses Epo receptor), but the proliferative capacity of these cells is not as high, thus yielding a colony with fewer than 8 cells. Likewise, an earlier stage of erythroid differentiation may also yield colonies in Epo-only medium, but these colonies would likely be smaller and/or not hemoglobinized, since the stages before the CFU-E stage (MEP and BFU-E) require other factors (IL-3 etc) and more time for growth that will also delay the terminal differentiation and hemoglobinization.
Haematopoiesis is the formation of blood cellular components. All cellular blood components are derived from haematopoietic stem cells. In a healthy adult human, roughly ten billion to a hundred billion new blood cells are produced per day, in order to maintain steady state levels in the peripheral circulation.
Erythropoietin, also known as erythropoetin, haematopoietin, or haemopoietin, is a glycoprotein cytokine secreted mainly by the kidneys in response to cellular hypoxia; it stimulates red blood cell production (erythropoiesis) in the bone marrow. Low levels of EPO are constantly secreted in sufficient quantities to compensate for normal red blood cell turnover. Common causes of cellular hypoxia resulting in elevated levels of EPO include any anemia, and hypoxemia due to chronic lung disease and mouth disease.
A megakaryocyte is a large bone marrow cell with a lobated nucleus that produces blood platelets (thrombocytes), which are necessary for normal clotting. In humans, megakaryocytes usually account for 1 out of 10,000 bone marrow cells, but can increase in number nearly 10-fold during the course of certain diseases. Owing to variations in combining forms and spelling, synonyms include megalokaryocyte and megacaryocyte.
Thrombopoietin (THPO) also known as megakaryocyte growth and development factor (MGDF) is a protein that in humans is encoded by the THPO gene.
Erythropoiesis is the process which produces red blood cells (erythrocytes), which is the development from erythropoietic stem cell to mature red blood cell.
Hematopoietic stem cells (HSCs) are the stem cells that give rise to other blood cells. This process is called haematopoiesis. In vertebrates, the first definitive HSCs arise from the ventral endothelial wall of the embryonic aorta within the (midgestational) aorta-gonad-mesonephros region, through a process known as endothelial-to-hematopoietic transition. In adults, haematopoiesis occurs in the red bone marrow, in the core of most bones. The red bone marrow is derived from the layer of the embryo called the mesoderm.
Interleukin 3 (IL-3) is a protein that in humans is encoded by the IL3 gene localized on chromosome 5q31.1. Sometimes also called colony-stimulating factor, multi-CSF, mast cell growth factor, MULTI-CSF, MCGF; MGC79398, MGC79399: after removal of the signal peptide sequence, the mature protein contains 133 amino acids in its polypeptide chain. IL-3 is produced as a monomer by activated T cells, monocytes/macrophages and stroma cells. The major function of IL-3 cytokine is to regulate the concentrations of various blood-cell types. It induces proliferation and differentiation in both early pluripotent stem cells and committed progenitors. It also has many more specific effects like the regeneration of platelets and potentially aids in early antibody isotype switching.
A proerythroblast is a precursor cell to the normoblast, as the earliest of four stages in its development.
Colony-stimulating factors (CSFs) are secreted glycoproteins that bind to receptor proteins on the surfaces of committed progenitors in the bone marrow, thereby activating intracellular signaling pathways that can cause the cells to proliferate and differentiate into a specific kind of blood cell.
The erythropoietin receptor (EpoR) is a protein that in humans is encoded by the EPOR gene. EpoR is a 52 kDa peptide with a single carbohydrate chain resulting in an approximately 56–57 kDa protein found on the surface of EPO responding cells. It is a member of the cytokine receptor family. EpoR pre-exists as dimers. These dimers were originally thought to be formed by extracellular domain interactions, however, it is now assumed that it is formed by interactions of the transmembrane domain and that the original structure of the extracellular interaction site was due to crystallisation conditions and does not depict the native conformation. Binding of a 30 kDa ligand erythropoietin (Epo), changes the receptor's conformational change, resulting in the autophosphorylation of Jak2 kinases that are pre-associated with the receptor. At present, the best-established function of EpoR is to promote proliferation and rescue of erythroid progenitors from apoptosis.
B-cell lymphoma-extra large (Bcl-xL), encoded by the BCL2-like 1 gene, is a transmembrane molecule in the mitochondria. It is a member of the Bcl-2 family of proteins, and acts as an anti-apoptotic protein by preventing the release of mitochondrial contents such as cytochrome c, which leads to caspase activation and ultimately, programmed cell death.
Stem cell factor is a cytokine that binds to the c-KIT receptor (CD117). SCF can exist both as a transmembrane protein and a soluble protein. This cytokine plays an important role in hematopoiesis, spermatogenesis, and melanogenesis.
The granulocyte-macrophage colony-stimulating factor receptor, also known as CD116, is a receptor for granulocyte-macrophage colony-stimulating factor, which stimulates the production of white blood cells. In contrast to M-CSF and G-CSF which are lineage specific, GM-CSF and its receptor play a role in earlier stages of development. The receptor is primarily located on neutrophils, eosinophils and monocytes/macrophages, it is also on CD34+ progenitor cells (myeloblasts) and precursors for erythroid and megakaryocytic lineages, but only in the beginning of their development.
Homeobox protein Hox-A9 is a protein that in humans is encoded by the HOXA9 gene.
CFU-GEMM is a colony forming unit that generates myeloid cells. CFU-GEMM cells are the oligopotential progenitor cells for myeloid cells; they are thus also called common myeloid progenitor cells or myeloid stem cells. "GEMM" stands for granulocyte, erythrocyte, monocyte, megakaryocyte.
CFU-Meg is a colony forming unit. Haematopoiesis in the bone marrow starts off from a haematopoietic stem cell (HSC) and this can differentiate into the myeloid and lymphoid cell lineages. In order to eventually produce a megakaryocyte, the haematopoietic stem cell must generate myeloid cells, so it becomes a common myeloid progenitor, CFU-GEMM. This in turn develops into CFU-Meg, which is the colony forming unit that leads to the production of megakaryocytes.
Megakaryocyte–erythroid progenitor cells (MEPs), among other blood cells, are generated as a result of hematopoiesis, which occurs in the bone marrow. Hematopoietic stem cells (HSC) can differentiate into one of two progenitor cells: the common lymphoid progenitor and the common myeloid progenitor. MEPs derive from the common myeloid progenitor lineage. Megakaryocyte–erythroid progenitor cells must commit to becoming either platelet-producing megakaryocytes via megakaryopoiesis or erythrocyte-producing erythroblasts via erythropoiesis. Most of the blood cells produced in the bone marrow during hematopoiesis come from megakaryocyte–erythroid progenitor cells.
Erythropoietin in neuroprotection is the use of the glycoprotein erythropoietin (Epo) for neuroprotection. Epo controls erythropoiesis, or red blood cell production.
Many human blood cells, such as red blood cells (RBCs), immune cells, and even platelets all originate from the same progenitor cell, the hematopoietic stem cell (HSC). As these cells are short-lived, there needs to be a steady turnover of new blood cells and the maintenance of an HSC pool. This is broadly termed hematopoiesis. This event requires a special environment, termed the hematopoietic stem cell niche, which provides the protection and signals necessary to carry out the differentiation of cells from HSC progenitors. This stem-cell niche relocates from the yolk sac to eventually rest in the bone marrow of mammals. Many pathological states can arise from disturbances in this niche environment, highlighting its importance in maintaining hematopoiesis.
Erythroferrone is a protein hormone encoded in humans by the ERFE gene. Erythroferrone is produced by erythroblasts, inhibits the production of hepcidin in the liver, and so increases the amount of iron available for hemoglobin synthesis. Skeletal muscle secreted ERFE has been shown to maintain systemic metabolic homeostasis.