In a stem cell transplant, stem cells are obtained from peripheral blood and transfused into a recipient to regenerate the hematopoietic system. For many leukemia sufferers in particular, stem cell transplantation represents the only chance for a cure, but it is also becoming increasingly important in the treatment of severe inborn errors of metabolism and autoimmune diseases.
What is stem cell transplantation?
In a stem cell transplant, stem cells are harvested from peripheral blood and transfused into a recipient to regenerate the hematopoietic system. Stem cell transplantation (SCT) generally refers to the transfer of peripheral blood hematopoietic stem cells from a donor to a recipient, and is used particularly for malignant hematologic diseases (malignancies of the hematopoietic system) such as leukemia, malignant lymphoma, or myeloproliferative disorders. In principle, a distinction is made between autologous stem cell transplantation, in which the donor and recipient are identical, and allogeneic stem cell transplantation, in which a recipient with hematologic oncology disease receives stem cell material from a healthy donor, preferably a sibling.
Function, effect, and goals
Stem cell transplantation is primarily performed in advance of radiation or chemotherapeutic therapy(including in the presence of neuroblastoma) that may affect stem cells. In addition, stem cell transplantation is performed as an alternative to bone marrow transplantation for a number of hematological diseases, especially leukemia (neoplasia form of the hematopoietic system). The indication for stem cell transplantation is especially for patients with acute lymphatic or myeloid leukemia, for whom consolidation therapy is used. In many cases, people affected by leukemia have a disturbed hematopoietic system directly as a result of the disease or as a consequence of high-dose chemotherapeutic treatment, which can be regenerated by stem cell transplantation. Moreover, the transfused hematopoietic stem cells support the destruction of malignant cancer cells present in the organism of the affected person, which cannot be recognized or fought by the immune system to the required extent. Stem cell transplantation is also becoming increasingly important in the treatment of genetic metabolic diseases and autoimmune diseases that cannot be controlled therapeutically (Still’s disease, systemic scleroderma). The majority of blood cells leave the bone marrow already differentiated as red or white blood cells. However, since pluripotent hematopoietic stem cells are also found 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 aid of stem cell apheresis, which is similar to the dialysis procedure. For this purpose, the donor is administered the growth hormone G-CSF (granulocyte colony stimulating factor) in the run-up to stem cell apheresis (a few days), which stimulates stem cell synthesis and correspondingly also increases the concentration of pluripotent cells in the peripheral blood. The donor is connected to an apheresis device via two venous catheters, which ensures both blood collection and separation of the individual blood components by centrifugation. The pluripotent stem cells are then removed from the apheresate (resulting blood product), while the remaining components are mixed again and infused into the donor. This procedure is performed a total of 4 times. During this process, a citrate solution is continuously administered to the donor for coagulation prophylaxis. If not enough stem cell material can be obtained, the procedure can be repeated after a few days. Following stem cell apheresis, the harvested material is cooled at 4-9°C or cryopreserved at -170°C. The recipient (especially in the case of patients with a history of cancer) is then given a citrate solution. In the recipient (especially in leukemia), on the other hand, myeloablative therapy is performed prior to stem cell transplantation by chemo- and radiotherapeutic measures to kill the hematopoietic cells. The subsequent infusion of the hematopoietic stem cells (via the vein) aims at the colonization of the bone marrow by the healthy cells and thus a regeneration of the hematopoiesis (blood formation) there.
Risks, side effects and dangers
Stem cell transplantation is a multistep and complex therapeutic approach that carries associated risks. For example, toxic-related side effects such as stomatitis (inflammation of the oral mucosa) or other inflammation of the mucous membranes, vomiting and nausea, hamörrhagic cystitis, hair loss, or organ-specific side effects due to cytostatic treatment may occur in the course of myeloablative therapy. In addition, possible late effects of myeloablative therapy include gonadal insufficiency and secondary malignancies. In addition, stem cell transplantation, although to a lesser extent than bone marrow transplantation, carries the risk of a graft-versus-host reaction, in which the recipient organism reacts cytotoxically to the transfused stem cells. Infections, for example by bacteria or fungi, can be observed very frequently, especially in the first three weeks after stem cell transplantation, since the recipient’s immune system is suppressed peritransplant (in the run-up to and following stem cell transplantation). As a result of taking the growth hormone, flu-like symptoms, headache, joint pain and/or depressive moods may be observed in the donor. Immediately during the performance of stem cell apheresis required for stem cell transplantation, nausea, dizziness, pain in the arms as a result of restriction of movement, burning sensation in the area of the injection sites (if there is a reaction to the citrate solution), and circulatory problems up to and including rare collapse may occur.
