Hematopoietic stem cells are precursor cells of blood cells. As a result of their maturation and differentiation, they produce all types of blood cells of myeloid (monocytes, macrophages, neutrophils, basophils, eosinophils, erythrocytes, megakaryocytes and platelets, dendritic cells) and lymphoid series (T-lymphocytes, B-lymphocytes, and natural killer cells) that determine immunity, fight infections, carry oxygen, and participate in blood coagulation processes. This is just one of several types of stem cells that can be found in our bodies. Read more about their functions here.
When hematopoietic stem cells (HSCs) are infused into a patient whose blood formation has been destroyed (as a result of high-dose chemotherapy, for example), they are able to populate the recipient’s bone marrow with their descendants and increase the number of blood cells, thereby restoring blood formation. Hematopoietic stem cell transplantation is based on this ability. Moving through the bloodstream, HSCs gradually populate the bone marrow and begin producing blood cells. These HSC cells are able to speed up the production of billions of new blood cells each day and completely restore the hematopoietic system and immune system, even when transplanted in small quantities.
Stem cell studies prove that there are two populations of progenitor (cells that differentiate into a specific cell type) hematopoietic stem cells: long-term and short-term. Long-term HSC cells are capable of self-renewing; short-term HSCs are not. However, short-term HSCs can differentiate into all types of blood cells.
Hematopoietic stem cells can be obtained from three sources:
Let’s take a closer look at these three sources.
Over a long period of time, bone marrow was the main source of HSC cells (and still widely used in transplantology). HSCs are located in adult bone marrow, including the femur, ribs, sternum mobilization, and other bones. But after the first successful transplantation of cord blood by Professor E. Gluckman (a boy with Fanconi anemia), cord blood took its rightful place in modern transplantology.
The concentration of pluripotent hematopoietic stem cells in cord blood is ten times higher than in bone marrow (read more about stem cell potency here). In addition, this source has several advantages for stem cell therapies:
Compared to bone marrow transplants, a peripheral blood transplant has many advantages:
• Peripheral blood contains more HSCs.
• Myeloid cells and platelets have a faster recovery.
• Cellular immunity is restored faster.
• Mortality rate due to transplantation is much lower.
Already, hematopoietic stem cells show great potential in the treatment of many serious diseases. For example, HSC cells are:
• used to treat patients with lymphoproliferative diseases (multiple myeloma, non-Hodgkin’s lymphoma, and Hodgkin’s disease);
• included in the treatment protocols for Parkinson’s disease, Alzheimer’s, Type 1 diabetes, myocardial infarction, and aplastic anemia;
• used in developing experimental approaches to the treatment of kidney and breast cancer, osteoporosis, systemic lupus erythematosus, joint lesions, and bone fractures.