Stem cells are special human cells that have the ability to develop into many different cell types, from muscle cells to brain cells. In some cases, they also have the ability to repair damaged tissues. Three sources from where stem cells can be taken:
Bone marrow
Bloodstream
Umbilical cord
Taking stem cells from bone marrow
Also known as a bone marrow transplant. In order to take stem cells from bone marrow, between 0.5 and 1.5 liters of bone marrow is removed from the back of the pelvic bone 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 anesthesia and hospital stay is needed. The blood usually only contains very few stem cells, so four to five days before the procedure is carried out a drug is injected under the skin (subcutaneously) once or twice. This drug is a growth factor known as GCSF (granulocyte colony-stimulating factor). It stimulates the movement of more blood stem cells from the bone marrow into the bloodstream.
After a few days, when there are enough stem cells in the blood, the blood is taken from a vein in one arm and passed along a tube into a special centrifuge called an apheresis machine. Here the stem cells are separated from the blood (a process known as apheresis). The blood is then returned to the body through another tube that goes into a vein in the other arm. Apheresis takes about two to three hours. The procedure of removing blood stem cells is usually carried out in an outpatient setting. In order to obtain enough blood stem cells, though, it often needs to be repeated once or twice in the days following the initial procedure.
The advantage of harvesting the stem cells from the blood instead of from bone marrow is that it doesn’t require the use of a general anesthetic.
But there may still be side effects. The growth factor drug may cause temporary problems such as joint pain, headaches or bone pain.