TY - CHAP M1 - Book, Section TI - Erythropoiesis A1 - Prchal, Josef T. A1 - Thiagarajan, Perumal A2 - Kaushansky, Kenneth A2 - Lichtman, Marshall A. A2 - Prchal, Josef T. A2 - Levi, Marcel M. A2 - Press, Oliver W. A2 - Burns, Linda J. A2 - Caligiuri, Michael Y1 - 2015 N1 - T2 - Williams Hematology, 9e AB - SUMMARYProduction of red cells or erythropoiesis, is a tightly regulated process by which hematopoietic stem cells differentiate into erythroid progenitors and then mature into red cells. Erythropoiesis generates approximately 2 × 1011 new erythrocytes to replace the 2 × 1011 red cells (approximately 1 percent of the total red cell mass) removed from the circulation each day. Red cell production increases several fold after blood loss or hemolysis. When one of the progeny of the multipotential hematopoietic stem becomes committed to the erythroid lineage, this early erythroid progenitor undergoes a series of divisions and concurrent maturation that eventually result in morphologically recognizable erythroblasts. After expulsion of the nucleus, a macrocyte (polychromatophilic when stained by Wright stain, or a reticulocyte if stained with new methylene blue) leaves the marrow. During the first 24 hours in the circulation, reticulocytes lose their residual organelles (mitochondria and ribosomes) through an autophagic process and undergoes reconditioning of the membrane to become mature red blood cells with a morphology of a biconcave disc. Erythropoiesis is controlled by transcription factors and cytokines, the principal ones being GATA 1 and erythropoietin (EPO), which influence the rate of lineage commitment, proliferation, apoptosis, differentiation, and number of divisions from the earliest progenitor to late erythroblasts. The number of red cells produced varies in response to tissue oxygenation that determines the level of the transcription factors, hypoxia-inducible factors (HIF), HIF-1 and HIF-2, the principal regulators of the response to hypoxia. HIFs modulate erythropoiesis by regulation of EPO production, by direct EPO-independent mechanism(s) and facilitating iron availability. SN - PB - McGraw-Hill Education CY - New York, NY Y2 - 2024/03/28 UR - accessmedicine.mhmedical.com/content.aspx?aid=1121091421 ER -