What are the stem cells used for cord blood?

Stem cells are the “mother” cells from which all the elements of the blood are formed: red blood cells, white blood cells, and platelets. At the time of a cord blood donation, only the white blood cells are preserved, because it is among them that there are the stem cells, the only cells able to reconstitute the whole of the immune system.

Stem cells are normally produced by the bone marrow. Some diseases such as leukaemia or a genetic defect or some medical treatments may have the side effect of destroying the bone marrow or impairing its functioning. The production of blood cells is then compromised, which can put the life of the sick person at risk. Physicians must replace the marrow with a stem cell transplant.

It is possible to use bone marrow transplants because it is also rich in stem cells. However, to receive a bone marrow transplant, you need to find a compatible donor, usually a related donor. Unfortunately, there is only a 25% chance of finding a compatible donor in the family of the sick person. In addition, as families are becoming smaller around the world, this further reduces the likelihood of finding a related donor.

There is also an international registry of unrelated stem cell donors. The probability of finding a compatible donor in less than 6 months ranges from only a few percent in certain medical conditions, cord blood is, therefore, an interesting alternative for obtaining compatible stem cells.

The benefits of cord blood

The stem cells contained in the cord blood have a high plasticity and adapt more easily to the recipient than those from the bone marrow. It is therefore not necessary to have such a strict compatibility to perform the transplant. Indeed, to evaluate the compatibility of a bone marrow donor, it is necessary to compare 10 specific genes while the compatibility of the cord blood is compared to only 6 specific genes. It is therefore much more common to find a compatible donor from a cord blood bank.

However, few stem cells can be collected in the cord blood. This treatment option is for people weighing less than 50 kilograms, that is, mostly children. Ongoing research shows, however, that transplants can be done in adults by simultaneously injecting 2 units of cord blood.

Much progress has been made since the first cord blood transplant in 1988. At the first ever hospital that conducted cord blood transplants, this form of therapy is used about 30 times a year, with excellent results. Cord blood is mainly used for cases of leukaemia, certain immune deficiency and some forms of anaemia. In addition, over the years, there are new applications for cord blood in the treatment of diseases.

How is the cord blood collected?

The donation of cord blood is a simple procedure. At birth, when the umbilical cord is cut, and before the placenta is expelled, up to about 150 ml of blood can be collected through the umbilical vein with a needle.

The blood is then analyzed. If the tests do not preserve the blood in the public bank (for example, if a unit of cord blood contains too few cells), it can be used for research in some university hospitals.

The blood is processed and frozen in liquid nitrogen. It can be stored for at least 10 years. All children can then benefit from a cord blood transplant if any, whether they have been donors or not. Studies in recent years indicate that it is beneficial for the baby to wait at least one minute after birth to cut the cord. The infant would then have a higher birth weight, a higher concentration of haemoglobin and better iron stores at 6 months of age.

Eric Traugott Author

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