Bone marrow transplant is the most widely used stem-cell therapy, but some therapies derived from umbilical cord blood are also in use. Research is underway to develop various sources for stem cells and to apply stem-cell treatments for neurodegenerative diseases and conditions, diabetes, heart disease, and other conditions.
Bone marrow has been used to treat cancer patients with conditions such as leukemia and lymphoma; this is the only form of stem-cell therapy that is widely practiced. During chemotherapy, most growing cells are killed by the cytotoxic agents. These agents, however, cannot discriminate between leukemia or neoplastic cells, and the hematopoietic stem cells within the bone marrow. It is this side effect of conventional chemotherapy strategies that the stem-cell transplant attempts to reverse; a donor’s healthy bone marrow reintroduces functional stem cells to replace the cells lost in the host’s body during treatment. The transplanted cells also generate an immune response that helps to kill off the cancer cells; this process can go too far, however, leading to graft vs. host disease, the most serious side effect of this treatment.
Another stem-cell therapy called Prochymal, for the management of acute graft-vs-host disease in children who are unresponsive to steroids. It is an allogeneic stem therapy based on mesenchymal stem cells (MSCs) derived from the bone marrow of adult donors. MSCs are purified from the marrow, cultured and packaged, with up to 10,000 doses derived from a single donor. The doses are stored frozen until needed.
What are stem cells?
Stem cells are primitive blood-forming cells that normally live in the bone marrow. They divide and mature into all the different types of blood cells (red cells, white cells, and platelets), including the cells of our immune system. They are the source of all of our blood cells and are therefore vital for our survival. Stem cells can be collected (harvested) directly from the bone marrow (bone marrow transplant), or they can be mobilized out of the bone marrow and collected from the bloodstream (peripheral blood stem cell transplant). Stem cells can also be collected from umbilical cord blood of newborn babies (cord blood transplant).
What is a stem cell transplant?
A stem cell transplant is a process that involves replacing blood-forming cells called stem cells that have been damaged as a result of high doses of chemotherapy or radiotherapy. High dose therapies are sometimes used because they give some people a better chance of cure or long-term control of their disease. Sometimes stem cells need to be replaced because they are diseased (for example in leukemia) or poor (for example in aplastic anemia).
Types of transplants
There are two main types of transplants – autologous and allogeneic.
An autologous transplant uses the patient’s stem cells, collected in advance and returned to them after they receive high doses of chemotherapy. In an allogeneic transplant, the stem cells are donated from another person, a genetically matched stem cell donor. While all transplants are serious procedures, allogeneic transplants are more complicated and therefore carry more short and long-term risks than autologous transplants.
The type of transplant you are given depends on some factors. These include the type of disease you have, your age, general health, the condition of your marrow and whether you would benefit by receiving donated stem cells, or whether your stem cells can be used.
A stem cell transplant is not necessarily the best option for everyone. The transplant process is demanding both physically and emotionally, and some people may not be fit enough to tolerate it. Also, many people don’t need a transplant and can be successfully treated using a less intensive approach. For others, a transplant is the only option which offers a prospect of a cure, or long-term survival.