Name: how red blood cells are replenished
Uploaded: 2023-04-30T10:37:28.000Z
Duration: 1 min 14 s
Channel: JoVE

Erythropoiesis is the process by which red blood cells or erythrocytes are generated in the bone marrow.
Erythrocytes contain hemoglobin that binds oxygen and delivers it to the tissues.
An injury followed by blood loss reduces the number of erythrocytes in the body, decreasing the oxygen reaching the tissues.&#160;
Low oxygen levels prevent the degradation of the transcription factor HIF-1&#593;. Accumulating HIF-1&#593; transcribes the erythropoietin or Epo gene, releasing more Epo into the blood.
Increased Epo levels stimulate erythroid progenitor cells in the bone marrow to proliferate and differentiate into colony-forming unit-erythroid or CFU-E.
As CFU-Es continue to divide and mature, they accumulate hemoglobin, lose their nucleus, and develop into immature reticulocytes.
Reticulocytes leave the bone marrow and move into the bloodstream, where they lose their ribosomes, mitochondria, and other organelles and undergo extensive membrane remodeling to form mature erythrocytes.

erythropoiesis

Erythropoiesis

Red blood cells &#160;(RBCs) transport oxygen to all body tissues. These cells survive only for 120 days and then need to be replenished. Erythropoiesis is the process of RBC production. In healthy individuals, erythropoiesis ensures all tissues are amply supplied with oxygen. In addition, blood loss due to injury leads to a drop in the physiological oxygen level that will cause erythropoiesis. Any defect in erythropoiesis leads to several physiological disorders, including thalassemia, anemia, and polycythemia.
Erythropoietin is a protein that (Epo) initiates erythropoiesis. The fetal liver initially produces Epo; however, post-birth, Epo is secreted by interstitial cells of the kidney. These cells sense a drop in physiological oxygen levels and induce Epo production.
As the level of Epo increases, Epo binds the erythropoietin receptor (EpoR) on erythroid progenitors. These progenitors reside in distinct niches called the &#8220;erythroblastic islands&#8221; of the bone marrow. Erythroid progenitors continue to proliferate and survive by interacting with a central macrophage or &#8216;nurse cells.&#8217; Upon stimulation, these progenitors undergo a series of differentiation and maturation stages. The early erythroid called burst-forming unit-erythroid (BFU-E) differentiates into colony-forming unit-erythroid or CFU-E. The CFU-E&#160; then develops into a pro-erythroblast that eventually loses the nucleolus and forms the basophilic erythroblast. The basophilic erythroblast starts accumulating hemoglobin and matures into a polychromatic erythroblast. Polychromatic erythroblasts have a higher amount of hemoglobin and many ribosomes. Polychromatic erythroblasts develop into orthochromatic erythroblasts, characterized by a small dense nucleus and hemoglobin filing most of the volume of the cell. Once orthochromatic erythroblasts expel the nucleus and lose the organelles, they form immature reticulocytes that stay in bone marrow for 2-3 days before entering the bloodstream, where they ultimately transform into the concave-shaped red blood cells.

Red blood cells &#160;(RBCs) transport oxygen to all body tissues. These cells survive only for 120 days and then need to be replenished. Erythropoiesis ...

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JoVE Core

Cell Biology

Unit 1

A Hierarchical Stem-Cell System: Blood Cell Formation

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KEY TERMS AND CONCEPTS

how red blood cells are replenished

Red blood cells, or RBCs, carry oxygen to body tissues and must be replaced after about 120 days. The body keeps this supply steady through erythropoiesis, the process of making new red blood cells. When oxygen levels drop after blood loss or injury, this process increases to restore oxygen delivery. Problems in erythropoiesis can lead to anemia, thalassemia, or polycythemia.

Erythropoietin, also called Epo, starts this process. Before birth, the fetal liver makes Epo. After birth, interstitial cells in the kidney make Epo instead. These kidney cells sense low oxygen levels and trigger more Epo production.

As Epo rises, it binds to the erythropoietin receptor, or EpoR, on erythroid progenitor cells. These early red blood cell precursors live in special bone marrow sites called erythroblastic islands. A central macrophage, sometimes called a nurse cell, helps them survive and continue to divide. The cells then move through several stages of growth and maturation.

The earliest erythroid cell, the burst-forming unit-erythroid or BFU-E, becomes a colony-forming unit-erythroid, or CFU-E. The CFU-E then develops into a pro-erythroblast. It loses the nucleolus and becomes a basophilic erythroblast. This stage begins hemoglobin accumulation and later forms a polychromatic erythroblast, which contains more hemoglobin and many ribosomes.

The polychromatic erythroblast matures into an orthochromatic erythroblast. This cell has a small, dense nucleus and a volume filled mostly with hemoglobin. It then expels its nucleus and loses its organelles to become an immature reticulocyte. Reticulocytes remain in the bone marrow for 2 to 3 days before entering the bloodstream, where they finally become the concave-shaped red blood cells seen in circulation.

How Red Blood Cells Are Replenished

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Red blood cells, or RBCs, carry oxygen to body tissues and must be replaced after about 120 days. The body keeps this supply steady through erythropoiesis, the process of making new red blood cells. When oxygen levels drop after blood loss or injury, this process increases to restore oxygen delivery. Problems in erythropoiesis can lead to anemia, thalassemia, or polycythemia. Erythropoietin, also called Epo, starts this process. Before birth, the fetal liver makes Epo. After birth,...

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key terms and concepts

Learn how the body replaces red blood cells through erythropoiesis, from kidney-made Epo to bone marrow stages that produce reticulocytes and RBCs.

How Red Blood Cells Are Replenished | JoVE K12

cell biology

JoVE Core Cell Biology illustrates complex cellular processes in easy-to-understand yet comprehensive animated video lessons. This collection focuses on the essential components and functions of cells, including organelles and membranes, cellular transport, and cell energetics. It is complemented by scientist-in-action videos that demonstrate the application of cell biology in real-world research experiments.

How Red Blood Cells Are Replenished

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