Erythropoiesis

What is erythropoiesis?

Erythropoiesis is how your body makes red blood cells (erythrocytes). This process ensures you have enough red blood cells. These blood cells are important because they:

• Transport oxygen you breathe in through your lungs to tissues throughout your body
• Transport carbon dioxide from tissues throughout your body to your lungs so you can breathe it out

Erythropoiesis is one part of hematopoiesis, which is how your body makes all blood cells.

Where does erythropoiesis take place?

Erythropoiesis begins during fetal development, starting in the yolk sac. Later, the fetal liver and spleen take over red blood cell production. By the fifth month of pregnancy, all erythropoiesis happens in the fetal bone marrow. This is the soft, squishy tissue inside your bones. Healthcare providers may call this fetal erythropoiesis.

What are the stages of erythropoiesis?

All blood cells start as hematopoietic stem cells (HSCs). To form blood cells, hematopoietic stem cells turn into common myeloid progenitor (CMP) cells. These cells may become red blood cells, platelets or a type of white blood cell. CMPs that become red blood cells are megakaryocyte erythroid progenitor (MEP) cells. These cells move through the following stages to become fully mature red blood cells:

• Proerythroblast: Hemoglobin begins to form during this stage. Proerythroblasts multiply to make more cells. These early red blood cells have a nucleus. The nucleus is a structure in your early red blood cell, which contains DNA.
• Erythroblast: Cells continue to divide and produce hemoglobin. They may also be called normoblasts.
• Reticulocyte: In this stage, immature red blood cells lose their nuclei and move into your bloodstream.
• Erythrocyte: In this final stage, mature red blood cells can carry oxygen.

It takes about a week for red blood cells to mature and move from your bone marrow to your bloodstream. Once there, the cells move oxygen from your lungs to your tissues. They carry carbon dioxide from your tissues to your lungs so you exhale carbon dioxide.

What triggers erythropoiesis?

The erythropoietin hormone (EPO) triggers erythropoiesis. You lose about 1% of your red blood cells every day as cells die or new cells replace damaged cells. Healthy kidneys release just enough EPO to replace those cells. They release more EPO if you have low red blood cell levels or conditions like sleep apnea, which affects oxygen levels in your blood. Chronic kidney disease can cause low EPO levels and too few red blood cells.

What happens if I don’t have the right number of red blood cells?

You may develop anemia or erythrocytosis:

• Anemia: This is a low level of red blood cells. In anemia, you don’t have enough red blood cells to carry oxygen to your body’s tissues. You may feel weak, tired or cold. You may feel short of breath while doing everyday activities.
• Erythrocytosis: This is a high red blood cell level. Your symptoms will vary depending on the type you have. They may be mild, like headaches and feeling tired. More serious issues include chest pain and shortness of breath. These may be symptoms of blood clots in your lungs and heart.

What conditions affect erythropoiesis?

Blood cancer, lung diseases and other issues may affect red blood cell production:

• Blood cancers: Diseases including leukemia, lymphoma and myeloma make abnormal cells that crowd out normal red blood cells. Myeloma damages your kidneys so they can’t release EPO. That disrupts red blood cell production. And certain myeloproliferative disorders cause your body to make too many red blood cells.
• Lung conditions: Lung disease can lead to high red blood cell levels. Diseases like asthma or chronic obstructive pulmonary disease (COPD) make it hard to take in oxygen. Low oxygen levels trigger the EPO hormone to make more red blood cells.

Other issues affect erythropoiesis. For example, red blood cell development relies on getting enough iron, B12, folate and several other micronutrients. Another example is erythropoiesis that can happen if you spend time in places located at very high altitudes. There’s less oxygen in the air at high altitudes. Your body reacts to low oxygen by releasing more EPO and boosting your red blood cell levels.

What treatments support erythropoiesis?

Treatment may include erythropoiesis-stimulating agents (ESAs). These are lab-made forms of EPO, the hormone that triggers erythropoiesis. In some cases, treating underlying conditions may help with adequate red blood cell production.