Cord Blood Stem Cell Transplantation
In recent years, cord blood has emerged as a source for stem cell
transplantation. Cord blood contains a significant number of hematopoietic
stem cells. For certain patients there are advantages to using cord blood
stem cells instead of marrow or peripheral blood stem cells for
transplantation. Cord blood and the stem cells it contains can be collected
from umbilical cord and placental blood after a baby is born.
What diseases may be treated with cord blood stem cell transplantation?
The first successful cord blood stem cell transplant was performed in 1988
in Paris, France. The patient, a boy with Fanconi's syndrome (a rare,
genetic and lethal type of anemia), is alive and healthy today. Cord blood
stem cell transplants have now been successfully given to patients (mostly
children) with some 80 disease diagnoses, including acute lymphocytic
leukemia (also called acute lymphoblastic leukemia or ALL), acute
myelogenous leukemia (AML), myelodysplasia, chronic myelogenous leukemia
(CML), juvenile chronic myelogenous leukemia (JCML), chronic lymphocytic
leukemia (CLL), Hodgkin and non-Hodgkin lymphoma, neuroblastoma,
thalassemia, severe combined immune deficiency (SCID), Wiskott-Aldrich
syndrome, metabolic diseases such as adrenoleukodystrophy and Hurler
syndrome and severe aplastic anemia. To date, more than 6,000 cord blood
stem cell transplants from unrelated donors and several hundred from
sibling donors have been performed worldwide.
How is cord blood collected, stored, and used for transplantation?
Collecting cord blood is relatively simple. Immediately after a baby is
delivered, the umbilical cord is clamped. When collected from the delivered
placenta, the placenta and the remaining attached umbilical cord (the
"afterbirth") are then removed to an adjacent laboratory. The placenta is
placed in a supporting frame. The surface of the cord is cleansed with
povidone-iodine (Betadine) and alcohol, and a needle is inserted into the
umbilical vein. The cord blood drains through the needle into a standard
blood collection bag that contains a solution to keep the blood from
clotting (anticoagulant), yielding an average of 60-120 milliliters (ml).
A second method involves collecting the cord blood after delivery of the
baby, while the placenta is still in the mother's womb. This method is
theoretically advantageous for two reasons. First, the collection begins
earlier, before the blood has a chance to clot. Second, it uses the
contractions of the uterus to enhance blood drainage in addition to
gravity. On the other hand, the technique is more intrusive and has the
potential to interfere with after-delivery care for the mother and infant.
This method may be preferred when collecting cord blood for a sibling who
needs a transplant because there is less risk of losing the collection due
to blood clotting or other reasons. The small increase of risk to the
mother and infant may be considered acceptable when a sibling with a
life-threatening disease may benefit.
The cord blood collected from a single placenta is called a cord blood
unit. The cord blood unit is transported to a facility for testing,
freezing and long-term storage. Testing procedures include HLA typing to
determine the level of matching to potential recipients, cell counts and
testing for infectious agents such as the AIDS virus, cytomegalovirus, and
hepatitis viruses. Next, the blood is frozen and held at a very low
temperature, usually in liquid nitrogen, for future use. When needed for a
transplant, the cord blood unit can be shipped immediately to the
transplant center where it is thawed and infused into the patient through a