A growth factor is a naturally occurring substance capable of stimulating cell proliferation, wound healing, and occasionally cellular differentiation. Usually it is a secreted protein or a steroid hormone. Growth factors are important for regulating a variety of cellular processes.
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.
A blood cell, also called a hematopoietic cell, hemocyte, or hematocyte, is a cell produced through hematopoiesis and found mainly in the blood. Major types of blood cells include red blood cells (erythrocytes), white blood cells (leukocytes), and platelets (thrombocytes). Together, these three kinds of blood cells add up to a total 45% of the blood tissue by volume, with the remaining 55% of the volume composed of plasma, the liquid component of blood.
Aplastic anemia is a severe hematologic condition in which the body fails to make blood cells in sufficient numbers. Aplastic anemia is associated with cancer and various cancer syndromes. Blood cells are produced in the bone marrow by stem cells that reside there. Aplastic anemia causes a deficiency of all blood cell types: red blood cells, white blood cells, and platelets.
Bone marrow is a semi-solid tissue found within the spongy portions of bones. In birds and mammals, bone marrow is the primary site of new blood cell production. It is composed of hematopoietic cells, marrow adipose tissue, and supportive stromal cells. In adult humans, bone marrow is primarily located in the ribs, vertebrae, sternum, and bones of the pelvis. Bone marrow comprises approximately 5% of total body mass in healthy adult humans, such that a man weighing 73 kg (161 lbs) will have around 3.7 kg (8 lbs) of bone marrow.
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.
Hematopoietic stem cells (HSCs) are the stem cells that give rise to other blood cells. This process is called haematopoiesis. In vertebrates, the very 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.
CD34 is a transmembrane phosphoglycoprotein protein encoded by the CD34 gene in humans, mice, rats and other species.
A stem cell line is a group of stem cells that is cultured in vitro and can be propagated indefinitely. Stem cell lines are derived from either animal or human tissues and come from one of three sources: embryonic stem cells, adult stem cells, or induced stem cells. They are commonly used in research and regenerative medicine.
Myeloid tissue, in the bone marrow sense of the word myeloid, is tissue of bone marrow, of bone marrow cell lineage, or resembling bone marrow, and myelogenous tissue is any tissue of, or arising from, bone marrow; in these senses the terms are usually used synonymously, as for example with chronic myeloid/myelogenous leukemia.
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.
Hemangioblasts are the multipotent precursor cells that can differentiate into both hematopoietic and endothelial cells. In the mouse embryo, the emergence of blood islands in the yolk sac at embryonic day 7 marks the onset of hematopoiesis. From these blood islands, the hematopoietic cells and vasculature are formed shortly after. Hemangioblasts are the progenitors that form the blood islands. To date, the hemangioblast has been identified in human, mouse and zebrafish embryos.
The National Marrow Donor Program (NMDP) is a nonprofit organization founded in 1986 and based in Minneapolis, Minnesota, that operates the Be The Match Registry of volunteer hematopoietic cell donors and umbilical cord blood units in the United States.
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.
Homeobox protein Hox-B6 is a protein that in humans is encoded by the HOXB6 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.
KSL cells in cell biology are an early form of mouse/murine hematopoietic stem cells. Characteristics are Kit (+), Sca-1 (+) and Lin (-). HSCs [Hematopoietic stem cells] in murine cultures show phenotypic markers as being CD34-, CD150+, and Flt3- for LTR [long-term reconstitution]. These phenotypic markers are used when purifying hematopoietic stem cells from the many other differentiated cells in the bone marrow.
The haematopoietic system is the system in the body involved in the creation of the cells of blood.
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 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.
A nucleated red blood cell (NRBC), also known by several other names, is a red blood cell that contains a cell nucleus. Almost all vertebrate organisms have hemoglobin-containing cells in their blood, and with the exception of mammals, all of these red blood cells are nucleated. In mammals, NRBCs occur in normal development as precursors to mature red blood cells in erythropoiesis, the process by which the body produces red blood cells.
