What is stem cell and bone marrow transplantation?
Sometimes patients have disorders in which the bone marrow is replaced by abnormal or cancer cells, such as leukemia, or sometimes a patient’s own bone marrow cells are unable to grow, divide and function normally. When this occurs a stem cell transplant may be helpful and curative. Stem cell transplantation means new bone marrow “stem cells” are given to replace the abnormal and/or cancer cells. Patients are first given treatment such as chemotherapy and/or radiation to destroy the abnormal cells, make “space” for the new stem cells, and prevent their own bodies from rejecting the new cells.
When you hear the term “bone marrow transplant,” the cells that are being transplanted are stem cells. These stem cells are immature blood cells that grow into mature red blood cells, white blood cells and platelets. Stem cells are present in the bone marrow and are collected from a volunteer donor, from umbilical cord blood and/or the placenta after the birth of a baby, or peripheral blood collected from the blood of a volunteer donor. Stem cells are an essential part of a person’s immune system.
The purpose of transplantation is to cure diseases by replacing the patient’s damaged immune system with healthy stem cells that will create a new immune system in the body.
Different types of stem cell transplants include:
- Bone marrow transplant
- Marrow transplant
- Peripheral blood stem cell transplant
- Stem cell transplant
- Hemopoietic cell transplant
- Hemopoietic progenitor cell transplant
- Pluripotent stem cell transplant
In each case, doctors are transplanting stem cells.
Types of Transplants
There are five types of transplants. The difference between the type of transplant has to do with the source of the transplanted cells. The type of transplant your child receives depends on his or her situation.
1. Autologous transplant—Transplanted cells come from the body of the transplant recipient.
2. Allogeneic transplant—Transplanted cells come from a donor who may be related to the recipient (a family member) or unrelated.
3. Syngeneic transplant—Transplanted cells come from an identical twin sibling (this is a type of allogeneic transplant).
4. Cord blood—Transplanted cells come from the umbilical cord and placenta after a baby is born. This blood is rich in blood-forming cells (this is a type of allogeneic transplant).
5. Mixed chimerism transplant—Transplanted cells come from either a related or unrelated donor. The transplant takes place after the recipient has a moderate dose of chemotherapy and radiation to set up a mixed immune system. This type is also called a mini-transplant or nonmyeloablative transplant (this is a type of allogeneic transplant).
Stem Cell Sources
If your child has a bone marrow transplant, he or she will receive bone marrow that has been collected from a donor. The donor may be a family member or an unrelated donor whose tissue type closely matches your child’s tissue.
The doctors collect bone marrow from the hip using large needles. The procedure (called bone marrow harvesting) takes about two hours and is performed on the day of transplant while the donor is sedated under anesthesia. Most donors do not need to stay at the hospital overnight.
Your child will receive the bone marrow cells by infusion in a procedure that is similar to receiving a blood transfusion. This takes several hours and is not painful.
Stem cells are produced in the bone marrow and circulate in the bloodstream. Circulating stem cells are called peripheral blood stem cells (PBSCs). If your child has a stem cell transplant, he or she will receive stem cells that have been collected from the blood of the donor—who may be your child (autologous transplant) or a sibling, another relative, or a closely matched, unrelated donor (allogeneic transplant).
An autologous stem cell transplant donor may be of any age, but an allogeneic stem cell transplant donor must be older than the age of 12.
During PBSC collection, the donor’s blood is withdrawn and circulated through a machine that separates out the stem cells and returns the remaining blood cells to the donor. For an autologous transplant, the collection is painless for the donor, who has blood withdrawn through a central intravenous catheter. For an allogeneic transplant, there may be some pain when needles are inserted into the donor’s arms to collect the cells. The donor can watch TV or read during this time. If the donor is a child, parents are encouraged to bring along favorite videos, games or other quiet activities.
Like bone marrow, umbilical cord blood contains stem cells. It comes from the umbilical cord of newborn infants and is removed from the placenta after birth and then stored. Once a cord blood match has been identified through the cord blood registry, the cord blood is shipped before your child starts receiving his or her transplant conditioning regimen.