After a baby is born and the umbilical cord is cut, some blood remains in the blood vessels of the placenta and the portion of the umbilical cord that remains attached to it. After birth, the baby no longer needs this extra blood. This blood is called umbilical cord blood: ‘‘cord blood’’ for short.
Cord blood contains all the normal elements of blood – red blood cells, white blood cells, platelets and plasma. But it is also rich in haematopoietic stem cells, similar to those found in bone marrow.
Stem cells have the remarkable potential to develop into many different cell types in the body during early life and growth. They serve as a sort of internal repair system, dividing more or less without limit to replenish other cells as long as the erson is still alive. This is why they can be used to treat many diseases.
Haematopoietic stem cells are the blood cells that give rise to all the other blood cells. Blood cells are vital to the human Red blood cells, which transport oxygen throughout the body;
- Red blood cells, which transportoxygen throughout the body;
- White blood cells, which are part of the immune system involved in defending the body against both infectious diseases and foreign materials (invading microorganisms, foreign particles or tumours);
- Platelets, which are involved in the physiological process that stop bleeding.
Every year, thousands of patients are diagnosed with diseases treatable by haematopoietic stem cell transplantation. When transplanted, haematopoietic stem cells repopulate the patient’s bone marrow, proliferate and differentiate into mature and functional blood cells.
How is cord blood obtained?
Once the baby is delivered, the umbilical cord is clamped. The blood from the umbilical cord and the placenta are then no longer needed by the baby or the mother. At this point, the cord blood can be collected, either before or after the placenta is delivered, depending on the procedure at the hospital.
If the cord blood is not collected for storage purposes, it will be thrown away and incinerated like other biological products in accordance withnational and international regulations.
Cord blood is collected in a sterile bag, which is referred to as a cord blood unit.
It is important to collect at least 70 cm3 of cord blood. The bag is then sent to a cord
blood bank, where tests and controls are performed (cell count, absence of ransmissible diseases, HLA typing). A big percentage of donated cord blood units
end up not being stored for transplantation, usually because they do not contain enough blood or cells to be transplanted into a patient.
When the cord blood unit is considered to be suitable for transplantation, it is given
an identification number and frozen for long-term storage in the bank. Normally,
cord blood units are stored in liquid nitrogen or in the vapour phase of liquid
nitrogen to keep them at -150 °C. Once stored, the cord blood unit is recorded in a registry and made available for use.
What is cord blood used for?
Transplantation of haematopoietic stem cells is currently the only available
treatment for patients with blood and immune system disorders, such as myelomas, leukemias, lymphomas and myeloproliferative neoplasms. In these conditions, the patients receive large doses of chemotherapy or radiation therapy to kill all the sick cells in their own blood. Doctors will then use haematopoietic stem cells to repopulate their bone marrow with healthy cells. Haematopoietic stem cells used for transplantation may be obtained from different sources:
- Bone marrow, collected from the hip. This has been the main source
of haematopoietic stem cells for the last few decades. The first bone marrow transplantation was reported in 1957 by Dr E. Donnall Thomas, who later received a Nobel Prize for his pioneering research.
- Peripheral blood. To collect haematopoietic stem cells from the blood, the donor has to receive a pharmacological treatment to make the haematopoietic stem cells
leave the bone marrow and go into the blood stream, where they can be easily collected by a procedure called aphaeresis.
- Cord blood,The first transplantation using haematopoietic stem cells from cord blood was performed in 1988y a team led by Dr E. Gluckmanto treat a five-year-old boy suffering from Fanconi’s anaemia.
Haematopoietic stem cell transplantation can be carried out using another person’s cells (either a family member or an unrelated donor). This is known as an “allogeneic transplantation”. Alternatively, the transplantation can be carried out using the patient’s own haematopoietic stem cells. This is called “autologous transplantation”.one marrow and peripheral blood stem cells are obtained from living donors, who can either be family members or unrelated volunteer donors. Donors are generous people who altruistically register in national bone marrow donor registries in case a compatible patient may need their cells. National registries are linked to international registries to increase the chance for doctors to find the most suitable donors for their patients.
Cord blood is an alternative source of haematopoietic stem cells that has been
widely used for patients lacking a compatible donor. Contrary to bone marrow and peripheral blood stem cells, which are only collected from the donor when a patient needs them, cord blood units are stored and readily available if a patient is in need of
an urgent transplant.
In this case, the donor’s immune system was less mature (he/she was a baby),
which allows for less stringent donor and recipient HLA matching than if the donor
had been an adult. When transplanting haematopoietic stem cells from cord blood, the risk for the patient developing graft versus host disease (GVHD) effect, a condition in which the haematopoietic stem cells from the donor attack the tissues and organs of the patient, often with a fatal result, is much lower than when using stem cells from peripheral blood or bone marrow.