Q: My son’s best friend is going to have a stem cell transplant in the next few weeks. What exactly are stem cells and why do some people need a transplant?

They are found in different places in the body such as bone marrow or fat tissue. Stem cells are unspecialized cells but from them, the body can produce a whole range of specialized cells with specific functions, such as blood cells. Stem cells are the only type of cell in the human body that can both regenerate themselves and produce new cells. There is a great deal of ongoing research into applications for the use of stem cells in treating disease, and much of that work in recent years has focused on tissue regeneration.

When we talk about a stem cell transplant, we’re referring to a specific type of treatment within the larger category of stem cell research and treatments. The transplant process involves using bone marrow or blood of a healthy person (a donor) or cord blood collected from a placenta shortly after birth and giving it to a patient who needs to develop new, healthy blood cells. The stem cells contained within the bone marrow, blood, and the umbilical cord blood are called hematopoietic stem cells, and they produce the various blood cells that the body needs to function.

During the transplant, the stem cells are injected into the patient’s body intravenously. In some cases, the stem cells can be taken from the patient themselves at an earlier time, and frozen until the transplant process takes place.

There are a number of different diseases which can be treated with stem cell transplants. These diseases include certain brain and blood cancers, diseases of the immune system, metabolic storage diseases such as Hurler syndrome, as well as disorders of the blood such as thalassemia or sickle cell disease. Transplantation is not necessary or possible for every patient with these disorders; the decision to proceed is guided by the medical literature and the healthcare team’s expertise.