Hematopoietic Stem Cells

Stem cells that form blood (red blood cells) and immune cells (white blood cells) are called hematopoietic stem cells. These cells work towards renewing blood cells and producing billions of new blood cells every day through a process called Hematopoiesis. These cells are multi-potent cells that are present in the blood and bone marrow. Multi-potency is the ability to differentiate into all functional blood cells.

The two main characteristics of hematopoietic stem cells are that they can renew themselves and they can produce cells that in turn give rise to different types of blood cells. There lies a small challenge in identifying these cells as they look similar to ordinary white blood cells.

Hematopoietic stem cells are used to treat malignant and non-malignant diseases to replace and rebuild a patient's Hematopoietic system. These cells are used to treat diseases of blood. There are two types of hematopoietic stem cells, long term and short term. Once these cells are removed from the bone marrow, it is very difficult to differentiate them. However long term hematopoietic stem cells can differentiate themselves by renewing indefinitely whereas short term hematopoietic stem cells cannot renew themselves beyond about 6 months.

Understanding Hematopoietic stem cells

Hematopoietic stem cells are cells that are isolated from the bone marrow or blood. They can renew themselves and differentiate themselves into a variety of specialized cells. These cells can arise out of the bone marrow into circulating blood. They also have the special property of programmed cell death also known as apoptosis wherein the cells that are not required or detrimental get into a programmed self destruction mode.

Hematopoietic stem cells sources:

The major sources of hematopoietic stem cells from where they can be derived are:

Bone marrow: Bone marrow is identified as a potential source of hematopoietic stem cells.

Peripheral blood: Though bone marrow is a potential source, physicians these days prefer to source hematopoietic stem cells from peripheral blood. They harvest hematopoietic stem cells from circulating peripheral blood. The donor is injected with cytokine - which increases the migration of the hematopoietic stem cells from the bone marrow into the peripheral blood. The blood from the donor is drawn using intravenous method, the blood drawn is passed through a filtering system that extracts the white blood cells and returns the red blood cells back to the donor. Of these cells collected, 5 – 20% of the cells are hematopoietic stem cells.

Umbilical cord blood: The umbilical cord and the placenta is a rich source of hematopoietic stem cells. Researchers have also identified the embryonic stem cells and the fetal hematopoietic system as a rich source of hematopoietic stem cells. Cells extracted from fetal hematopoietic system are not being used clinically while the cells extracted from the embryonic stem cells are under extensive study.

Do hematopoietic stem cells from different sources vary ?

Considerable research is being conducted to understand hematopoietic stem cells. Hematopoietic stem cells extracted from tissues at early developmental stage have a greater ability to self replicate. They are well accepted by the immune system thus making it more useful for therapeutic transplantation.