Umbilical cord blood is a valuable source of stem cells − the cells that can renew themselves and develop into other types of cells. With minimal effort, umbilical cord blood may provide a life-saving opportunity for patients with various life-threatening diseases such as cancer or immune system disorders.
The functions of the umbilical cord
The umbilical cord is a bond between the unborn baby and the placenta. It supplies the baby with blood rich in oxygen and nutrients. The umbilical cord is no longer needed when the baby is born; the usual practice is to clamp and cut the umbilical cord immediately after birth. After this procedure, approximately 50-100 mL of blood remains in the umbilical cord and placenta.
Collecting umbilical cord blood cells
Umbilical cord blood collection is a safe, painless, and quick procedure that can be done both after natural delivery and Cesarean section. It does not interfere with regular labor management. Umbilical cord blood collection cannot be done only in cases of serious complications in the mother (e.g., massive bleeding, extremely elevated blood pressure resulting in seizures) or baby (e.g., breathing problems).
After the umbilical cord is clamped and cut, a sterile needle is inserted into the umbilical cord vein, and the blood is drained by gravity to the plastic blood collection system, similar to that used for blood donations. Within 48 hours of collection, the cord blood is processed to be suitable for cryopreservation (long-term freezing). During the processing, the fraction of white blood cells that contains the stem cells are kept while the rest of the white blood cells and the red blood cells are discarded. A small amount of the product is taken for testing, and the rest proceeds to the freezing stage, which is done at a controlled rate until -150 to -200°C. At this temperature, which is maintained by liquid or vapor nitrogen, the cells can be stored for a long time. The research shows that umbilical cord blood units stored for up to 15 years are as effective as those stored for shorter periods, but little data are available beyond this limit.
In addition to storing umbilical cord blood, it is possible to store the umbilical tissue, which contains more diverse stem cells (e.g., epithelial and mesenchymal cells). After collecting umbilical cord blood, the segment of the cord is cut, placed in a sterile container, and sent for processing and cryopreservation.
Umbilical cord blood banking
Two options for umbilical cord blood banking are public and private. Public umbilical cord blood banks obtain the umbilical cord blood donated by parents. The samples are available for general public use. Private banks store umbilical cord blood for individual use by the families only and are taking a fee for this service. Hybrid umbilical cord blood banks operating as public banks but offering cord blood storage for families are starting to emerge.
Potential applications of umbilical cord stem cells
The first transplantation of umbilical cord blood was performed in a 5-year-old boy with Fanconi anemia, an inherited disorder that affects the bone marrow and results in insufficient production of blood cells. The umbilical cord blood of his sister, who was not a carrier of a defective gene and was suitable as a donor, was collected and transplanted to the patient. The patient is alive up to this day.
In 1992, the Placental Blood Program was established at the New York Blood Center, and in 1993, the first umbilical cord blood units from this program were transplanted to unrelated children from Duke University Medical Center suffering from serious, mostly malignant, diseases. About half of those transplantations were successful.
In 2013, a 9-year-old boy with severe aplastic anemia (failure of bone marrow to produce red blood cells) received a life-saving transplant of his own umbilical cord blood unit that was donated and years later found in a public cord blood register.
Currently, cord blood transplantation is considered a treatment option for blood cancers and serious non-malignant blood disorders (e.g., thalassemia, sickle cell disease), bone marrow failure, inherited metabolic disorders, and immunological disorders (e.g., severe combined immunodeficiency syndrome), and certain solid tumors. The potential use of umbilical cord blood cells is being investigated in such diseases as cerebral palsy, diabetes, spinal cord injury, brain injury, hearing loss, etc.
Of note, in most cases, an allogeneic umbilical cord blood transplantation, i.e., cord blood from another person, is recommended.
Problems with umbilical cord blood transplantation
Umbilical cord blood saved in private cord blood banks is often regarded as insurance for the baby. However, the diseases that can be treated with umbilical cord blood transplantation are rare, and other options are often available. Besides, in certain instances, using one‘s umbilical cord blood will not be curative. In cases when the child has a defect of a genetic origin (e.g., metabolic disorders or some cancers), the umbilical cord blood cells also have these defects. Thus, the probability that a child would be able to use their cord blood is extremely small: the chances are estimated to range from 1:400 to 1:200,000 over the child’s lifetime.
On the other hand, when transplanted to another person, immune cells in the umbilical cord blood may attack the recipient's cells and induce so-called graft versus host disease. However, it is somewhat less frequent and milder than after stem cell transplantation from other sources, e.g., bone marrow.
Another hurdle for umbilical cord blood cell use is the limited number of stem cells that can be collected, which may not be sufficient for successful engraftment in an older child or adult. This is managed by administering two units of umbilical cord blood and developing methods to expand the cells before transplanting artificially.
Many professional organizations, including the American College of Obstetricians and Gynecologists, the American Academy of Pediatrics, and the American Society for Blood and Marrow Transplantation, support cord blood banking in the public sector. The storage in hybrid banks may be prudent for families with children with a disease that may be treated with a cord blood transplant. The storage of umbilical cord blood in private banks remains at the parents‘ discretion.