Hematopoietic stem cells & it's importance in stem cell therapy.

Hematopoietic stem cells & it's importance in stem cell therapy.

Question:- What are hematopoietic stem cells? Explain their importance in stem cell therapy.

The stem cells that form blood and immune cells are known as hematopoietic stem cells (HSC). They are ultimately responsible for the constant renewal of blood; the production of billions of new blood cells each day.

All differentiated blood cells from the lymphoid and myeloid lineages arise from HSCs. HSCs can be found in adult bone marrow, peripheral blood, and umbilical cord blood. A hematopoietic stem cell is a cell isolated from the blood or bone marrow that can renew itself, can differentiate to a variety of specialized cells, can mobilize out of the bone marrow into circulating blood, and can undergo programmed cell death, called apoptosis. This is a process by which cells that are detrimental or unneeded are self-destruct.

Sources of HSC: Hematopoietic stem cells can be found in the following-

Bone marrow- In the case of a bone marrow transplant, the HSC are removed from a large bone of the donor, typically the pelvis, through a large needle that reaches the center of the bone. The technique is referred to as a bone marrow harvest.

Peripheral blood stem cells- Peripheral blood stem cells are now the most common source of stem cells for allogeneic HSCT. They are collected from the blood through a process known as apheresis.

Amniotic fluid- It is also possible to extract stem cells from amniotic fluid for both autologous or heterologous use at the time of childbirth.

Umbilical cord blood- Umbilical cord blood is obtained when a mother donates her infant's Umbilical Cord and Placenta after birth. Cord blood has a higher concentration of HSC than is normally found in adult blood.

Clinical uses of HSC: Among the clinical uses of HSC, the first was the treatment of cancer of the blood- leukemia and lymphoma, which is a result of an uncontrolled proliferation of white blood cells. This happens through radiation or chemotherapy where the patient's own cancerous hematopoietic cells are destroyed and then replaced with a bone marrow transplant, or with a transplant of HSC collected from the peripheral circulation of a matched donor, as is done in present days.

Another use of allogeneic bone marrow transplants is in the treatment of hereditary blood disorders, such as different types of inherited anemia and inborn errors of metabolism.

Chemotherapy aimed at rapidly dividing cancer cells inevitably hits another target, rapidly dividing hematopoietic cells. Doctors may give cancer patients an autologous stem cell transplant to replace the cells destroyed by chemotherapy. They do this by mobilizing HSC and collecting them from peripheral blood.

The study of hematopoietic stem cells is rapidly advancing in biomedicine today. Breakthrough discoveries have greatly expanded the use and supply of life-saving stem cells. The techniques, cells, and knowledge that researchers at present possess are inadequate to realize the full utility of HSC-based therapy. Key issues for tapping the potential of hematopoietic stem cells will be finding ways to safely and efficiently expand the numbers of transplantable human HSCs in vitro or in vivo. It will be important to have a better understanding of the fundamentals of how immune cells work, in fighting infections, in causing transplant rejection as well as master the basics of HSC differentiation.
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