Also known as hematopoietic stem transplantation, bone marrow transplantation has emerged as a boon for mankind. Bone marrow is one of the prime necessities in every human, as it is the site for blood corpuscle production. Apart from that, bone marrow is also the primary production site for inborn immunity. Bone marrow lymphocytes, comprised (8-20%) of the mononuclear cells maintain a strict immune cell ratio of 5/1 for T cell/ B cell. The need for transplantation mostly arises due to bone marrow cancer, or severe terminal metabolic disorder which is unrecoverable even after exposure to persistent conventional treatments. Apart from that, bone marrow transplantation may also be required due to the following reasons:
- Destruction of the bone marrow due to consecutive chemotherapy or other radioactive radiation therapy to combat cancerous cells in and near the marrow.
- Cancer like myelodysplasia, leukemia as well as lymphoma reduces the normal functioning capability of the existing bone marrow
- Blood-related disorders like thalassemia, anemia (aplastic or sickle cell), neutropenia (congenital) can adversely affect the production of hematopoietic components
The procedure is highly prevalent across the world with approximately 50,000 transplants being performed every year across the world. However, finding a matching donor for bone marrow transplant happens to be the primary hurdle in the case of BMT.
1. What is bone marrow transplantation?
The long bones (thigh bone or femur) inside the human body contain soft, sponge-like connective tissue which is primarily associated with the production of blood corpuscle, immune cells, and fat. An important element of the lymphatic system, the BM is extremely vascular and is divided into two parts:
- Redbone marrow: Associated mostly with stem cell (lymphoid and myeloid) production, and is highly vascular.
- Yellow bone marrow: Associated with fat production mostly, and is non-vascular.
Severe illness or cancer of the bone marrow may require immediate transplantation. The transplantation procedure involves removing the affected or damaged hematopoietic cells with healthy or functioning ones. The need for replacing the affected cells arises in order to ensure healthy blood circulation and prolonged lifespan.
2. Diagnosis and Tests related to BMT
Thorough screening is extremely important before performing any bone marrow transplantation procedure. This is to determine the primary health condition of the individual as well as to source compatibility, mostly in the case of allogeneic transplantation.
- Laboratory blood tests are performed to determine:
- Tissue typing
- Other underlying health issues (if any)
- Screening for non-infectious or infectious diseases
- Screening of functioning capability of vital organs of the body
- X-rays: X-rays are suggested to confirm primal lung or chest health conditions.
- PFT: Pulmonary Function Test Is performed to determine functioning capability of lungs, as well as the oxygen-carrying capability of the blood
- CT scan: Advanced screening to determine any underlying condition in the body
- PET scan: Positron Emission Tomography is usually done to check the vital organ functioning
Besides, other tests to determine heart rate, blood pressure, bone marrow biopsy, etc., shall also be performed, depending on the type and extent of disease an individual is suffering from.
3. Types of Donors for BMT
There are two types of BMT donors that hugely determine the type of transplantation procedure that needs to be executed. The types of procedure performed also determines the risk of Graft Vs Host Diseases, abbreviated as GVHD, which is considered as the primary threat for such transplants. Hence, the two major types of transplantation are:
- Autologous transplant: In this procedure, the damaged hematopoietic cells are replaced by the candidate’s own bone marrow cells. In this case, before executing any therapeutic procedure (like chemotherapy) which poses a serious threat to the BM cells, the professionals remove the existing healthy bone marrow cells and preserve it in suitable conditions. After completion of the procedure, the cells prior removed are re-placed in its existing position. Since the graft and the host are from the same individual, the GVHD threats are fairly low or negligible.
- Allogeneic transplant: Matching donor for bone marrow transplant of this type, is extremely important. The procedure involves the usage of someone else’s bone marrow who shows genetic compatibility. This can either be fetched from the person’s own family or can also be availed from registry centers. Although the procedure is the only choice left in case of complete bone marrow damage due to certain diseases, yet the GVHD threats are extremely high. To have an enhanced lifespan, the candidate undergoing transplantation is subjected to immunosuppressive drugs for the rest of his/her life.