What is stem cell or bone marrow transplantation?

Traditionally the term 'bone marrow transplantation' has been used to describe the process of taking cells from a person's bone marrow and re-infusing them following high doses of chemotherapy or radiation treatment. Stem cells can also be obtained from donors, eg, a brother or sister, or non-related person with compatible tissue type.

What do stem cells do?

Stem cells, dividing in the bone marrow, are responsible for the production of red and white blood cells and platelets. They also circulate in the blood in small numbers.

Chemotherapy effects

High-dose chemotherapy is a common treatment for patients with diseases relating to the blood and bone marrow, and some other types of diseases, but the drawback is that normal cells are usually killed, along with the remaining malignant cells. To overcome this, stem cells are collected prior to treatment and infused into the patient after chemotherapy.

These stem cells home in and grow in the bone marrow cavity, and produce new red blood cells, white blood cells and platelets. Also see: Blood cell types

There are recent developments in transplantation, called mini transplant or non-myeloablative transplantation, where the initial chemotherapy dose is reduced. This minimises the toxicity associated with chemotherapy and means that older patients may be treated safely with this technique.

The stem cells are important wherever they are collected, either in the blood where they travel, or in the bone marrow where they rest and divide. Stem cells can be collected by a variety of ways, from a variety of different donors (see further below).

Where can stem cells be found? 

Bone marrow: Stem cells can be collected from the bone marrow of a donor. This requires the donor to have a general anaesthetic so that cells can be collected by multiple needle punctures from the hip bone or sternum.

Peripheral blood: Stem cells can be found in normal blood in very small numbers. Following chemotherapy or treatment with a bone marrow stimulant called G-CSF (granulocyte-colony stimulating factor), the stem cells leave the bone marrow in increased numbers and enter the peripheral blood. There they can be collected by a special harvesting technique using a cell separator machine.

Umbilical cord blood: The umbilical cord blood is normally discarded when a baby is born. It is a rich source of stem cells. These can be extracted from the discarded cord after the delivery of a baby, stored permanently and be a source of bone marrow. This process does not represent a risk to the baby or mother.

Who can provide stem cells?

Autologous: Using the patient's own stem cells (auto = oneself). These can be collected when the patient is in remission.

Allogeneic: From donor stem cells (with a compatible tissue type):

• Sibling: Stem cells taken from a compatible brother or sister, or more rarely, another family member.
• Unrelated: Stem cells can be collected from volunteers who have signed up with one of the many bone marrow or cord blood registries located worldwide. Compatible donors are found by searching the database of registered donors.

These procedures are not suitable for everyone and represent a major undertaking for doctors, nurses and families and a major risk to the patient. However, when possible, transplantation offers the best known opportunity of a cure for many diseases.

Related topics

Also see Leukaemia and Blood cell types

Main types of leukaemia - Chronic myeloid leukaemia, Chronic lymphocytic leukaemia, Acute myeloid leukaemia, Acute lymphoblastic leukaemia

Original material provided by the Leukaemia and Blood Foundation of New Zealand, 2007. Edited by everybody, August 2010.