Cord Blood Transplants
When performing stem cell transplants, there are four major sources from which blood-forming stem cells can be retrieved: embryonic stem cells, bone marrow, peripheral or circulating blood, and cord blood.
Cord blood is collected from the umbilical cord and placenta after a child is born. Cord blood has unique features that distinguish it from other stem cell sources and make it a better option for stem cell transplants under certain circumstances. In the past, cord blood has mainly been recommended for use in children, and adults weighing 110 pounds or less. Current stem cell research, however, has been looking to extend the use of cord blood and provide its many benefits safely in adults.
The Benefits of Cord Blood
Each stem cell source has its own benefits and drawbacks that differ from those of another source. Accordingly, cord blood has many known unique benefits that differ from bone marrow and peripheral blood stem cells.
Some of the advantages of cord blood include the following:
- Less Specific Matching. Clinical studies have found that while the closest match possible is preferred when it comes to stem cell transplants, cord blood matches are more tolerant of inexact matches than peripheral blood and bone marrow transplants. For this reason, cord blood may be suited for individuals who have uncommon tissue types, making it difficult for a perfect match to be found.
- More Readily Available. Because cord blood units are already stored in cord blood banks, a unit may be selected and delivered to a transplant center in less than two weeks. When it comes to bone marrow and peripheral blood stem cells, it can take several months to find an unrelated donor.
- Decreased Risk of GVHD. Graft-versus-host disease is a complication that can develop after an allogeneic transplant. Studies have shown that individuals undergoing a cord blood transplant are at a decreased risk of developing GVHD than those who receive other types of stem cell transplants. Those individuals who did develop GVHD following a cord blood transplant tended to have milder cases.
Current Limitations of Cord Blood
Cord blood represents a rich source of blood-forming cells. However, the amount of stem cells found in a cord blood unit (a stored unit held for future transplants) is limited. One of the central criteria when it comes to matching donated stem cells and patients is the ratio between the amount of blood-forming cells and the size of the patient. For this reason, cord blood units have most commonly been used to treat children and small adults.
The following are some reasons why a cord blood stem cell transplant may not be recommended:
- Cell/Size Ratio. The amount of blood-forming cells in the cord blood unit is too small relative to the size of the patient
- Risk of Infection. Because it takes longer for cord blood cells to grow and create new blood cells (engraft), a new immune system will develop slower than in other cases of stem cell transplants, increasing the risk of infection in the mean time.
- Backup Cells. Patients are unable receive cells from the same cord blood unit once a transplant has taken place. This option is available to patients receiving bone marrow or peripheral blood transplants and is useful in cases relapse or if stem cells fail to engraft. However, it may be possible to use a different cord blood unit or another means of stem cell donation in such cases.
- New Treatment. Cord blood for stem cells transplant is a relatively new form of treatment and doctors do not have as much information regarding the long-term results of cord blood transplants as they do when it comes to bone marrow.
Cord Blood and Treatable Diseases
Umbilical cord blood transplants have been used to treat a variety of blood, bone, genetic, and immune system diseases. Previous stem cell transplants performed on children using cord blood have helped treat the following:
- Cancers such as Lymphoma and Leukemia
- Blood Disorders such as Sickle Cell Anemia
A more comprehensive list of treatable diseases by cord blood transplants can be found here.