What Are Hematopoietic Stem Cells

Stem cells are undifferentiated cell found in our body which has the ability to differentiate itself into any type of cell with their specialized function. The hematopoietic stem cells are found in the bone marrow of humans. It is also obtained from the cord blood found in the cord which connects the fetus with the mother. This cord after the birth of the baby is detached and thrown away. This cord and cord blood can be collected and processed to harvest the stem cells from it.

The hematopoietic stem cells are pluripotent in nature and can only give rise to cells of the blood both of myeloid lineage and lymphoid lineage. The hematopoietic stem cells are responsible for constant renewable of the blood cells. These cells have mobility and can come out of the bone marrow and enter the circulating blood stream. The blood cells have a life of just 120 days and after that they undergo programmed cell death called the apoptosis and they need to be replaced by new blood cells. These hematopoietic stem cells are now regularly used for therapy of blood related disorders such as leukemia.

The hematopoietic stem cells first appear in the human embryo in the yolk sac and then migrate to the liver as the fetus develops. In fetus, the blood cells are created in the liver, but soon after birth they are created exclusively in the bone marrow. These stem cells can be isolated, stored, and also cultivated rarely. They are the main ingredient of bone marrow transplants. If the bone marrow is transplanted to the same individual from whom it was isolated it is called as autotransplantation and if donated to someone else it is called allogenic transplantation. Like other stem cells, hematopoietic stem cells have the ability to strike a balance between self renewal and a commitment to differentiation. This ability needs genetic program in these cells. This involves a large number of gene products, some of which differ in fetal and adult hematopoietic cells.

The HSC’s produce in an hour, 3-10 billion platelets, red cells, neutrophils, lymphocytes and even macrophages of the immune system. The cells are used for transplantation in patients, whose immune and blood forming system have been devastated by leukemia, cancer, chemotherapy or other unknown causes. Bone marrow donors are classified by a method called HLA typing, which is used for matching the recipient. However, for autologous transplantation, a patient’s own stem cells are collected, frozen and stored outside the body, while chemotherapy or radiation therapy is given to remove the malignant cells. The bone marrow thus stored is returned directly into a vein.

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