Stem cells are immature cells which have not yet become specialized cells of a part of the body. They are, literally, a blank canvas and have the remarkable ability to turn into almost any other cell within the body. Stem cells can differentiate, to become a specialized cell that can heal or repair damaged organs. They can also reproduce to create more healthy stem cells.
Bone marrow is a sponge-like substance found inside bones. It contains millions of stem cells.
There are two types of bone marrow; red bone marrow, which contains mainly hematopoietic tissue, and yellow marrow, which consists mainly of fat cells. At birth most of our bone marrow is red but as we age, more of it becomes yellow.
The stem cells in the hematopoietic tissue of the bone marrow turn into blood cells: white blood cells (leukocytes) to fight infections, red blood cells (erythrocytes) to carry oxygen around the body and platelets (thrombocytes) that help blood to clot. Hematopoietic tissue produces 500 million blood cells a day, which are carried out of the bone marrow via blood vessels. These blood vessels also act as a barrier, preventing immature blood cells from entering the blood.
Bone Marrow Disorders
There are a wide range of bone marrow diseases, which are either inherited or acquired. If a person has a bone marrow disease, it means that they have a problem with their bone marrow or the cells produced by the bone marrow. For example, leukaemia is a cancer where the white blood cells produced by the bone marrow are abnormal, and aplastic anaemia is an inherited condition where the bone marrow fails to make red blood cells.
Another cause of failing bone marrow is chemotherapy and cancer treatment for solid cancers, such as breast and lung cancer. The treatment used to kill cancerous cells also kills or damages the cells within the bone marrow, meaning that production of the essential blood cells is inhibited.
Bone Marrow Transplant
By introducing healthy bone marrow cells to someone with failing bone marrow, the new cells stimulate healthy blood cell production and the creation of properly functioning bone marrow.
If someone has a genetic or acquired bone marrow disease, or has bone marrow that has been damaged by chemotherapy and radiation treatment, it is possible to take hematopoietic stem cells from one person and give them to another person (known as an allogeneic transplant), or infuse them back into the same person at a later date (known as autologous treatment).
In cases where the transplant is used to treat a bone marrow disease, the existing bone marrow in the patient is first killed using chemotherapy or radiation therapy, enabling the new healthy cells to enter the bone marrow and reproduce without any chance of the old, unhealthy cells continuing to reproduce.