Bone marrow harvest.
In the case of a bone marrow transplant, the HSC are removed from a large bone of the donor, typically the pelvis, through a large needle that reaches the center of the bone. The technique is referred to as a bone marrow harvest and is performed under general anesthesia.
Peripheral blood stem cells
Main article: Peripheral stem cell transplantation
Peripheral blood stem cells
Peripheral blood stem cells are now the most common source of stem cells for HSCT. They are collected from the blood through a process known as apheresis. The donor’s blood is withdrawn through a sterile needle in one arm and passed through a machine that removes white blood cells. The red blood cells are returned to the donor. The peripheral stem cell yield is boosted with daily subcutaneous injections of granulocyte-colony stimulating factor, serving to mobilize stem cells from the donor’s bone marrow into the peripheral circulation.
It is also possible to extract stem cells from amniotic fluid for both autologous or heterologous use at the time of childbirth.
Umbilical cord blood
Umbilical cord blood is obtained when a mother donates her infant’s umbilical cord and placenta after birth. Cord blood has a higher concentration of HSC than is normally found in adult blood. However, the small quantity of blood obtained from an umbilical cord (typically about 50 mL) makes it more suitable for transplantation into small children than into adults. Newer techniques using ex-vivo expansion of cord blood units or the use of two cord blood units from different donors allow cord blood transplants to be used in adults.
Cord blood can be harvested from the umbilical cord of a child being born after preimplantation genetic diagnosis (PGD) for human leukocyte antigen (HLA) matching (see PGD for HLA matching) in order to donate to an ill sibling requiring HSCT.
Storage of HSC
Unlike other organs, bone marrow cells can be frozen (cryopreserved) for prolonged periods without damaging too many cells. This is a necessity with autologous HSC because the cells must be harvested from the recipient months in advance of the transplant treatment. In the case of allogeneic transplants, fresh HSC are preferred in order to avoid cell loss that might occur during the freezing and thawing process. Allogeneic cord blood is stored frozen at a cord blood bank because it is only obtainable at the time of childbirth. To cryopreserve HSC, a preservative, DMSO, must be added, and the cells must be cooled very slowly in a controlled-rate freezer to prevent osmotic cellular injury during ice crystal formation. HSC may be stored for years in a cryofreezer, which typically uses liquid nitrogen.
The chemotherapy or irradiation given immediately prior to a transplant is called the conditioning regimen, the purpose of which is to help eradicate the patient’s disease prior to the infusion of HSC and to suppress immune reactions.