About stem cells
Stem cells are parent cells from which all other blood cells (red blood cells, white blood cells and platelets) develop.
Bone marrow constitutes the factory that produces stem cells. It is a soft and gelatinous tissue that fills the inside of bones such as the sternum or the pelvis. Bone marrow differs from spinal marrow: spinal marrow is the part of the nervous system that descends inside the vertebral column.
Stem cells are found primarily in bone marrow. They are also found in small quantities in a person’s peripheral bloodstream.
Umbilical cord blood from newborn children is another source of stem cells.
Therapeutic use: transplantation
Certain fatal diseases such as leukemia destroy bone marrow or make it function abnormally. Given that bone marrow produces blood, the life of a person whose bone marrow is not functioning properly is in danger. Treatment can involve destroying the patient’s bone marrow and replacing it through a transplant of stem cells from the bone marrow, peripheral bloodstream or cord blood of a compatible donor.
A stem cell transplant is not the only therapeutic solution possible for diseases such as leukemia and other cancers that result in the abnormal functioning of the bone marrow. Treatments such as chemotherapy, radiotherapy and specialized medications are tried first of all to attempt to stop the disease. However, in some cases, these treatments do not work, and the only way to save these patients involves replacing their stem cells with stem cells from people who are in good health.
Patients whose bone marrow is destroyed and who receive a stem cell transplant must remain isolated in a room until the transplant has been successful and their new bone marrow has produced sufficient white blood cells to protect their system against surrounding bacteria.
If a patient needs a stem cell transplant, who is the best donor?
The characteristics of the stem cells that are transplanted must be as close as possible to those of the patient. Since these characteristics are hereditary, we look first of all for a compatible donor, i.e., a person whose genetic tissue markers are sufficiently similar to those of the patient, in the patient’s family (generally a brother or sister). The chances of finding a compatible donor in the family are approximately 25%, or one in four.
If a donor is not found within the family, we then try to identify a non-related compatible donor with the help of what we call the Stem Cell Donor Registry.
What are these genetic tissue markers that determine the compatibility between donor and recipient for the purposes of a stem cell transplant?
These markers make up the HLA (human leukocyte antigen) system and are different than the blood types (A, B, O or AB). In order to determine the compatibility between a donor and a recipient, we perform HLA typing, which is an analysis of the characteristics of the antigens or proteins present on the surface of the white blood cells. If there are not enough similarities between the HLA characteristics of the donor and the recipient, we cannot transplant the stem cells because this procedure would most certainly be a failure.
The HLA system is so complex that the chances of finding a compatible non-related donor for a patient can vary from 1 in 450 to greater than 1 in 750,000. That is why we need to have a Stem Cell Donor Registry with a sufficiently large and diversified number of registrants who could eventually donate stem cells.
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