biologyerythropoiesis

Biology of erythropoiesis refers to the biological processes by which red blood cells (erythrocytes) are produced, matured, and maintained in the vertebrate hematopoietic system. In adults, erythropoiesis occurs primarily in the red bone marrow, where hematopoietic stem cells differentiate along the erythroid lineage under tight regulation. The process begins with multipotent stem cells that commit to the erythroid pathway, forming erythroid progenitors such as burst-forming unit-erythroid (BFU-E) and colony-forming unit-erythroid (CFU-E). These progenitors progress through stages including proerythroblast, basophilic erythroblast, polychromatic erythroblast, and orthochromatic erythroblast, during which hemoglobin synthesis increases and ribosomes are progressively lost.

A key feature is enucleation: in mammals, late-stage erythroblasts expel their nucleus to form reticulocytes, which enter the bloodstream and complete maturation to mature erythrocytes within about one to two days. Erythropoiesis is iron- and vitamin-dependent; iron supports heme synthesis, while B12 and folate are required for rapid DNA replication in dividing cells. Erythropoietin (EPO), produced mainly by renal peritubular cells in response to hypoxia, is the primary hormonal regulator, acting on erythroid progenitors via the erythropoietin receptor. Hypoxia-inducible factors (HIFs) modulate EPO expression in low oxygen conditions.

During fetal life the liver and spleen contribute significantly before the bone marrow takes over as the principal site after birth. Reticulocytes mature into erythrocytes in circulation, which have an average lifespan of about 120 days and are removed by macrophages in the spleen and liver. Disorders of erythropoiesis can lead to anemia, polycythemia, or dyserythropoiesis.