Hematopoietic stem cells are populations of slowly proliferating stem cells in the bone marrow, found in the center of bones, that give rise to blood cells. The cells are found in compartments called niches, and the interaction between the stem cells and the niche governs the behavior of the stem cells. A number of diseases involve disruption of hematopoietic stem cell behavior, and these diseases may be treated with stem cell transplants.
Leukemia
Leukemias are a group of cancers that affect the white blood cells. Although different types of leukemia differ in their aggressiveness and the specific cell subtypes affected by the disease, leukemias share the characteristic that the cancer develops within the bone marrow. Under normal conditions, bone marrow cells give rise to a balance of cell types to respond to the needs of the body. According to the University of Virginia, in some forms of leukemia, the stem cells within the bone marrow have become mutated and give rise to too many white blood cells, generating huge populations of defective white blood cells. Bone marrow transplant to remove the mutant cells and replace them with healthy marrow cells treats the cancer by preventing the growth of more abnormal white blood cells.
Lymphoma
Lymphoma is another form of cancer that affects the white blood cells. Unlike leukemia, which develops within the bone marrow, lymphomas typically start within the lymphatic system, such as in the lymph nodes. As the cancer progresses and becomes more advanced, the lymphoma can spread to the bone marrow.
The chemotherapy treatments used to treat severe lymphoma also affect the bone marrow, so severe courses of chemotherapy for lymphoma may require bone marrow transplants to allow for proper bone marrow function after treatment. LymphomaInfo.net reports that patients about to receive a high dose of chemotherapy will often have their bone marrow removed beforehand, then transplanted again after chemotherapy. Patients may also receive bone marrow transplants from tissue donors after treatment.
Aplastic Anemia
Aplastic anemia is a condition in which the bone marrow is unable to produce enough of all three major cell types. The patient may suffer from anemia due to low red blood cell counts, immunodeficiency and neutropenia due to low white blood cell counts, and bleeding disorders due to low platelet counts. This could be due to a decrease in the number of proliferating stem cells, leading to decreased blood cells, or due to dysfunction of bone marrow cells to prevent blood cell maturation.
The University of Maryland Medical Center reports that bone marrow transplant can be used to successfully treat aplastic anemia. The transplant replaces the dysfunctional bone marrow with healthy marrow from a tissue donor to restore normal blood development and treat the disease.
