At a Stem cell transplant stem cells are obtained from the peripheral blood and transfused to a recipient to regenerate the blood-forming system. For many people with leukemia in particular, a stem cell transplant is the only chance of a cure, but it is also becoming increasingly important in the treatment of severe congenital metabolic and autoimmune diseases.
What is a stem cell transplant?
As Stem Cell Transplant (SCT) is the general term used for the transfer of peripheral hematopoietic blood stem cells from a donor to a recipient, which is used in particular for malignant hematological diseases (malignant diseases of the blood-forming system) such as leukemia, malignant lymphomas or myeloproliferative diseases.
In principle, a distinction is made between the autologous, in which the donor and recipient are identical, and the allogeneic stem cell transplant, in which a recipient with hematological and oncological disease receives stem cell material from a healthy donor, preferably a sibling.
Function, effect & goals
A Stem cell transplant is primarily carried out in the run-up to radiation or chemotherapeutic therapeutic measures (e.g. in the case of existing neuroblastomas), which can affect the stem cells.
In addition, stem cell transplants are performed as an alternative to bone marrow transplants for a number of haematological diseases, especially leukemia (neoplasmic form of the blood-forming system). The indication for a stem cell transplant exists in particular in those affected with acute lymphatic or myeloid leukemia, for whom consolidation therapy is used.
In many cases, as a result of the disease or as a result of a high-dose chemotherapeutic treatment measure, people affected by leukemia have a disturbed blood-forming system that can be regenerated by a stem cell transplant. In addition, the transfused hematopoietic stem cells support the destruction of the malignant cancer cells in the organism of the person concerned, which the immune system cannot recognize or fight against to the extent necessary.
Stem cell transplantation is also becoming increasingly important in the treatment of genetically determined metabolic diseases and therapeutically uncontrollable autoimmune diseases (Still's disease, systemic scleroderma). The majority of the blood cells leave the bone marrow already differentiated as red or white blood cells.However, since there are also pluripotent stem cells of blood formation in the peripheral blood, albeit in a much lower concentration than in the bone marrow, these stem cells can be filtered out and processed from the peripheral blood with the help of stem cell apheresis, which is similar to the dialysis process.
For this purpose, the donor is given the growth hormone G-CSF (granulocyte colony stimulating factor) prior to stem cell apheresis (a few days), which stimulates stem cell synthesis and increases the concentration of pluripotent cells in the peripheral blood accordingly. The donor is connected to an apheresis device via two venous catheters, which ensures that blood is drawn and the individual blood components are separated by centrifugation.
The pluripotent stem cells are then removed from the apheresis (blood product), while the remaining components are mixed again and infused into the donor. This procedure is carried out a total of 4 times. A citrate solution is continuously administered to the donor to prevent clotting. If not enough stem cell material can be obtained, the procedure can be repeated after a few days.
Following the stem cell apheresis, the material obtained is cooled at 4-9 ° C or cryopreserved at -170 ° C. In the recipient (especially in the case of leukemia), on the other hand, prior to the stem cell transplantation, chemotherapy and radiation therapy are used to carry out myeloablative therapy to kill the blood-forming cells. The subsequent infusion of the hematopoietic stem cells (via the vein) aims to colonize the bone marrow by the healthy cells and thus to regenerate the hematopoiesis (blood formation) there.
Risks, side effects & dangers
A Stem cell transplant is a multi-level and complex therapeutic approach that is associated with corresponding risks.
Toxic side effects such as stomatitis (inflammation of the oral mucosa) or other inflammations of the mucous membranes, vomiting and nausea, hemorrhagic cystitis, hair loss or organ-specific side effects caused by cytostatic treatment can occur in the context of myeloablative therapy. Possible long-term effects of myeloablative therapy are also gonadal insufficiency and secondary malignancies.
In addition, with a stem cell transplant, if to a lesser extent than with a bone marrow transplant, there is a risk of a graft-versus-host reaction in which the recipient organism reacts cytotoxically to the transfused stem cells. Infections caused by bacteria or fungi, for example, can very often be observed, especially in the first three weeks after the stem cell transplant, as the recipient's immune system is suppressed peritransplant (before and after the stem cell transplant).
As a result of the ingestion of growth hormone, flu-like symptoms, headaches, joint pain and / or depressive moods can be observed in the donor. While performing the stem cell apheresis required for stem cell transplantation, nausea, dizziness, pain in the arm area as a result of movement restriction, burning sensation in the area of the puncture sites (when reacting to the citrate solution) and circulatory problems up to the rare occurrence of collapse can occur.
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