What is hematopoiesis?

Hematopoiesis is the process of creating new blood cells from stem cells. It happens naturally in the body, starting when a human is still an embryo. The process continues through adulthood to keep the blood supply replenished.

Hematopoiesis is also an important step in the medical treatment of people with bone marrow disease. Stem cell and bone marrow transplant recipients rely on hematopoiesis to make new healthy blood cells to treat conditions like leukemia and other blood cancers, hereditary blood conditions, and certain immune disorders.

Scientists study hematopoiesis to learn more about how blood disorders and cancers can form and be treated in the body.

A focus of current research is how human embryonic stem cells affect blood cell formation. Studies are also underway to discover more about what distinguishes normal, healthy stem cells and the hematopoietic stem cells associated with leukemia. Ways to treat certain inheritable diseases by administering healthy stem cells to a fetus within the mother’s womb are being investigated as well.

Mature red blood cells, white blood cells, and platelets (the cells involved in clotting) all start out as primitive stem cells.

At its earliest stage, a stem cell has the potential to become just about any type of mature cell — such as a blood cell, skin cell, or muscle cell. Through a series of transformations, a stem cell becomes a precursor to whatever kind of mature cell it’s going to become.

In the case of hematopoiesis, the precursor cells will become blood cells.

There are two types of precursor cells in the bone marrow: myeloid and lymphoid cells.

Myeloid cells are involved in trilineage hematopoiesis. This term refers to the normal production by your bone marrow of three blood cell lines: red blood cells, certain white blood cells, and platelets.

Lymphoid cells create a separate white blood cell line leading to T cells and B cells. These white blood cells have a different function within the immune system compared to those that develop from myeloid cells.

Trilineage hematopoiesis is a marker for how well your blood cell production system is working. If it’s reduced or increased, or if an abnormal number of other cells are present in your bone marrow, there may be a problem with your blood cell production system.

In its earliest stages, an embryo is attached to the yolk sac. The yolk sac is a membrane outside the embryo that is responsible for the embryo’s circulation. Early on, blood cells form in the yolk sac.

As the fetus develops in the womb, the spleen, liver, and bone marrow become the main sources of blood cell production.

After birth and as a child grows to adulthood, the bone marrow becomes the main location for hematopoiesis.

If your body isn’t producing adequate numbers of red blood cells, you’ll develop anemia. Anemia causes you to feel tired and weak because your muscles and other tissue aren’t getting their usual supply of oxygen from red blood cells.

Too few white blood cells will make your body less able to fight off an infection. And if your platelet count is down, you face a higher risk of bleeding episodes and excessive bruising.

Normal hematopoiesis can be affected by many conditions, including inherited conditions, infections, toxins, vitamin and mineral deficiencies, and medications. Blood cancers, such as leukemia, lymphoma, and myeloma, can also interfere with healthy blood cell production.

A hematologist is a specialist in blood disorders. If you’re diagnosed with a condition that affects normal hematopoiesis, this specialist will work with your other doctors to map out a treatment plan. Leukemia, for example, is treated with chemotherapy. Certain forms of anemia can be treated with changes in diet or with iron or other nutrient supplements.

With proper treatment, your blood cell production may be stabilized if you have a blood disorder.

If you don’t have any major medical issues, but you want to know about your red blood cells, white blood cells, and platelets, you can find out with a simple blood test. These counts are part of a complete blood count, which is a standard blood test.

As for hematopoiesis and hematopoietic stem cell therapy, there is still much to be learned. But exciting research is investigating how to further unleash the potential of stem cells for life-saving treatment.