Bone marrow is the spongy, soft tissue within the bone. All types of blood cells, including young blood cells produced by the bone marrow, are called stem cells.
A bone marrow transplant involves the introduction of healthy hematopoietic cells into the human body to replace damaged or diseased ones. Most often, stem cells are taken not from the bone marrow, but from the blood. Therefore, the procedure is often called blood stem cell transplant.
The operation is used as a potentially curative therapy for some dangerous hematological cancers and non-malignant blood diseases. Bone marrow transplantation is necessary in cases where the blood does not cope with its functions.
This procedure is effective for a variety of conditions including:
• severe forms of aplastic anemia
• tumor diseases of the blood (multiple myeloma, lymphoma, leukemia, lymphogranulomatosis, neuroblastoma, etc.)
• non-neoplastic diseases with damage to platelet and erythrocyte hematopoiesis
• serious damage to the immune system
• genetic and autoimmune diseases
Autologous Bone Marrow Transplant
This implies the transplantation of native stem cells, or in other words, the patient's own stem cells.
This type of transplant is usually preferred for lymphoma, multiple myeloma (mm), germ cell tumors, and acute leukemia — albeit rarely.
Autologous Stem Cell Transplant: Designed to enhance the outcome of chemotherapy in patients with multiple myeloma or certain high-risk lymphomas. Autologous stem cell transplantation is preferred for recurrent lymphomas.
Before autologous stem cell transplantation, an assessment of your cardiac and respiratory function is carried out, as well as a study of contraindications for transplantation.
When collecting a patient's own stem cells, the presence of diseased cells among the stem cells is a risk that should be considered. Accordingly, when cryopreserved stem cells are re-transplanted into a patient, diseased cells, which may be among healthy stem cells, may relapse.
Allogeneic Bone Marrow Transplant
This method involves the transplantation of stem cells that are collected from a fully compatible person to the patient.
Since all of the harvested stem cells are intact, the risks associated with autologous transplantation do not apply. In allogeneic transplantation, transplantation of the immune system of a healthy person is beneficial.
When transplanting stem cells from another person, the immune system may not be fully compatible. Thus, the donor's immune system can react against the organs of the recipient. This can damage the liver, skin, bone marrow, and intestines. This is called graft versus host disease. The condition can be treated, but organ failure may develop as organ damage has already occurred. This risk does not apply to allogeneic transplantation.
Although allogeneic stem cell transplantation is more commonly performed in cancer patients, it may also be preferred in diseases characterized by bone marrow failure.
Primary diseases for which allogeneic stem cell transplantation is a therapeutic option:
• Acute leukemia (acute myeloid leukemia, acute lymphoblastic leukemia).
• Myelodysplastic syndrome (MDS).
• Severe aplastic anemia and other conditions of bone marrow failure (Fanconi anemia, paroxysmal nocturnal hemoglobinuria, pure erythroid aplasia).
• Non-Hodgkin's lymphoma
• Hodgkin's lymphoma.
• Chronic leukemia (chronic myeloid leukemia, chronic lymphocytic leukemia)
Haploidentical Bone Marrow Transplant.
It is a good alternative for patients who do not have a fully HLA compatible donor. A fully compatible donor should be preferred, but if no such donor is available, a partially compatible related donor should be considered. The consequence of this method in patients who do not have the opportunity to spend time searching for an unrelated donor is the same success as other methods of transplantation. The most important disadvantage of haploidentical transplantation is the higher risk of infection (since there is significant antigenic incompatibility). Therefore, it is necessary to very carefully monitor infections and take protective measures in a timely manner.
When searching for a donor for transplantation of allogeneic stem cells, the tissue groups of siblings, if any, are first analyzed. If siblings do not have a fully matched donor, close relatives of the patient can be screened, and the final option is a “bone marrow bank” if the screening result is negative. Finding a matched donor from bone marrow banks can take 2 to 10 months.
The patient is being prescribed high-dose chemotherapy for the first time in allogeneic stem cell transplantation, similar to autologous stem cell transplantation. The patient is then transplanted with stem cells collected from a healthy donor (native or unrelated). These stem cells enable the production of healthy blood cells in the patient's bone marrow.
Graft versus host (GVHD) stem cell transplantation is a possible risk secondary to tissue incompatibility between donor and patient. GVHD is a serious illness that can cause serious damage to the organs of the recipient. Therefore, it is imperative that the patient and donor are fully compatible as much as possible.
The bone marrow is responsible for the synthesis of cells that are essential for life and to fight against harmful factors and results. Uncontrolled or false synthesis or inability to synthesize these cells can lead to disease.
Following the onset of these diseases, hematopoietic stem cell transplantation may sometimes be required due to recurrence of the disease, even though recovery can be achieved with various medical treatments and / or the inability to achieve recovery or the need for high-dose chemotherapy to achieve recovery.
It should always be remembered that in a bone marrow transplant, patients are vulnerable to infection and sometimes bleeding. As a rule, almost all patients who undergo allogeneic transplant use immunosuppressive drugs, and therefore one should be very careful both in relation to the risks of infection and in relation to drug interactions in other therapies.
Although these risks are very likely with allogeneic transplants, there are short-term risks with autologous transplants because no immunosuppressive drug is used. The correspondence between donor stem cells and patient tissues is ensured by various immunosuppressive treatments.
How is bone marrow obtained for transplantation and how is peripheral stem cells harvested for transplantation?
Stem cells used for transplantation can be harvested from bone marrow, peripheral blood, and cord blood from a mother who has recently given birth. Although stem cells harvested from peripheral blood are generally preferred, stem cells harvested from bone marrow will be preferred in benign diseases such as aplastic anemia, thalassemia, and immunodeficiency syndromes.
Peripheral stem cells are harvested using an apheresis device after using cytokines that help stem cells in the bone marrow migrate into the peripheral blood called granulocyte colony stimulation factor (G-CSF).
For patients in need of autologous transplantation, stem cells can be harvested from peripheral blood using G-CSF after chemotherapy, while the white blood cell count rises.
Stem cells cannot be harvested using these methods from patients whose bone marrow is extremely weak for certain reasons. For these patients, stem cells can be harvested from peripheral blood using potent stem cell stimulating drugs that contain pleifaxor as the active ingredient, concurrently with G-CSF. Stem cells are harvested from the bone marrow, especially from the pelvic bone, using special needles under general anesthesia in the operating room.
What to expect during the transplant recovery process?
Before allogeneic transplants, patients usually receive high-dose chemotherapy drugs and immunosuppressive drugs. Next, the stem cells are transferred to the patient through a central catheter. The risk of infection is high due to chemotherapy drugs and immunosuppressive drugs.
During this high-risk baseline period, such treatments should be administered in bone marrow transplant units equipped with hepafilters and ventilation systems that can purify infectious agents in the environment. Even if these conditions are met, the risk of infection is always high for these patients.
These patients should be closely monitored, and if an infection develops, treatment should be started immediately. After the donor's bone marrow has engrafted, a struggle can be observed between the donor cells and the patient's tissues. Immunosuppressive drugs are used in these patients to avoid this condition. The successful outcome in these patients depends on the type of disease, the stage of the disease, and the degree of donor-patient match.
Even if these conditions are met, the risk of infection is always high for these patients. These patients should be closely monitored, and if an infection develops, treatment should be started immediately.
After the donor's bone marrow has engrafted, a struggle can be observed between the donor cells and the patient's tissues. Immunosuppressive drugs are used in these patients to avoid this condition. The successful outcome in these patients depends on the type of disease, the stage of the disease, and the degree of donor-patient match.
Although bone marrow transplant is a lifesaving option for diseases that occur in the bone marrow and cannot be managed with medical treatment, the most important problem is that a compatible sibling is not always available. In such cases, non-family donors are valuable options, and voluntary donation of one tube of blood to bone marrow banks is a valuable option.
Unlike organ donation, bone marrow donation does not cause a deficiency in any organ or human body, and this short, honorable waste of time can save the life of another person. At the moment, any person between the ages of 18 and 55 can be a bone marrow donor. It is imperative to raise awareness on this issue.
These transplants can take the form of an autologous transplant - the patient's native cells are transplanted back into the patient after high-dose medical therapy - or allogeneic transplantation - another person's stem cells or bone marrow are transplanted into the patient.
Compatible siblings and related or tissue-compatible unrelated individuals are potential donors for allogeneic transplants. Stem cells derived from peripheral blood, bone marrow, or umbilical cord blood can be used.