Mention the term stem cell, and a heated discussion is likely to erupt. While most people have heard about the controversial research into human embryonic stem cells, many may not know the scope of stem cell science and that the use of some types of stem cells has become routine.
Stem cell is the term used for these master cells of the body that are able to divide and reproduce themselves endlessly or grow into any one of the body’s more than 200 cell types. They are one starting point for the miracle of growth and regeneration and the reason a life form as complex as a human being can develop from a single cell. Stem cells are undifferentiated in their basic form but have the ability to differentiate into more mature, specific cells. The two broad categories of stem cells are embryonic and adult stem cells.
Current adult stem cell therapy
Hematopoietic stem cells are one type of adult stem cell. Produced in the bone marrow, they have been used to treat hematologic malignancies for more than 30 years. They are now used to treat disorders of the blood and immune systems, including inherited immune system disorders, severe aplastic anemia, sickle cell anemia, Hodgkin’s disease, myelodysplastic syndromes, non-Hodgkin’s lymphoma, and acute or chronic leukemias.
In the past, hematopoietic stem cells were collected directly from the bone marrow. Today, stem cells are most commonly collected from the peripheral blood. Stem cells are mobilized out of the bone marrow into the bloodstream by chemotherapy, growth factors, or a combination of both where they can be collected through apheresis, a procedure in which the blood of a donor is passed through an apparatus that separates out hematopoietic stem cells and returns the remainder of the blood to circulation.
Hematopoietic stem cells can also be found and harvested from umbilical cord blood. “The umbilical cord contains about 100 ml of blood that is very rich in [adult]stem cells,” says Susan Ezzone, RN, MS, CNP, AOCNP, a nurse practitioner at the Blood and Marrow Transplant Program at Ohio State University Medical Center’s Arthur G. James Cancer Hospital & Solove Research Institute in Columbus. “The tricky thing with umbilical cord stem cells is that there is not a large volume of cells, so its use in adults may be somewhat limited.”
Possible solutions to controversy
Using human embryonic stem cells for research and potential treatments is charged with controversy because it involves the destruction of embryos. Currently, embryonic stem cells used in research have been created in vitro by fertility clinics and are not taken from women’s bodies. These embryos have been donated with informed consent from the donors.
Researchers are making big strides in stem cell science that could someday reduce or eliminate the need to use embryonic stem cells. Animal studies point to the possibility that some kinds of adult stem cells could also be pluripotent, that is, able to produce embryonic in addition to adult stem cell types.
For example, it is theorized hematopoietic adult stem cells may be able to develop into cells other than blood cells, such as liver, skeletal muscle, cardiac muscle, and neurons, including brain cells.
This ability is called plasticity or potency, and researchers are trying to uncover the secrets of how to induce adult stem cell plasticity within a lab. Some exciting examples of their potential include replacing dopamine-producing nerve cells in the brains of patients with Parkinson’s and insulin-producing beta cells in the pancreases of people with type I diabetes.