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How are blood stem cells obtained for transplantation?

Blood stem cells used to be taken mainly from bone marrow, where they develop. Nowadays it is also possible to filter stem cells directly out of the bloodstream. The first method is called a bone marrow transplant, and the second method is called a peripheral blood stem cell transplant. The donor’s body replaces the donated bone marrow or blood stem cells on its own within a few days. Some people feel tired during this time. It is very rare for donors to experience serious complications after donating stem cells, but temporary adverse effects are possible.

Taking stem cells from bone marrow

In order to take stem cells from bone marrow, up to one liter of bone marrow is removed from the back of the pelvic bone (the iliac crest) using a special needle. To do this, the needle usually has to be inserted at different points on the bone. The stem cells are then removed from the bone marrow in a laboratory and prepared for transplantation.

Removing bone marrow is a complex procedure. The donor is given a general anesthetic, and usually spends one to two days in the hospital. In the first few weeks following the procedure, there may be bruising and pain where the needle was inserted. Some people mainly have temporary back pain. Having an anesthetic is always associated with certain risks too. And there is a risk of infection from the surgical procedure. For these reasons, stem cells are generally taken from blood nowadays.

Removing stem cells from blood

Using peripheral stem cells has the advantage that no anesthetic is needed and you do not have to stay in hospital. In this approach, people are first given injections of a drug that moves some of the stem cells out of the bone marrow and into the bloodstream. This drug is a growth factor known as GCSF (granulocyte colony-stimulating factor).

After a few days, when there are enough stem cells in the blood, they are filtered out of the blood using a process called apheresis. This involves removing blood from one arm and passing it into a machine through a tube. The stem cells are then separated from the blood in the machine. The rest of the blood is returned to the body through another tube that goes into the other arm. It can take a few hours to remove stem cells from blood in this way, but this procedure is usually carried out in an outpatient setting. The growth factor drug may temporarily cause flu-like symptoms such as joint ache or headaches. But there is not enough research on rare adverse effects, particularly long-term adverse effects.

Umbilical cord blood

Another possible source of stem cells is blood in the umbilical cords of newborn babies. There are a lot of stem cells in umbilical cord blood, and the blood can be collected and frozen immediately after birth. This approach is sometimes used in the treatment of children and teenagers. But it is currently not clear whether there are enough stem cells in umbilical cord blood to treat adults.

You can read more about stem cell transplantation and other treatments for cancer here.

Author: German Institute for Quality and Efficiency in Health Care (IQWiG)