Stem Cell Transplantation

A stem cell transplant (also known as a bone marrow transplant) involves replacing defective or cancerous bone marrow with freshly harvested, healthy cells. A stem cell transplant may treat leukaemia, lymphoma, blood cancers, and the lymphatic system. As well as treating hereditary blood disorders, such as sickle cell anaemia, and autoimmune diseases, such as multiple sclerosis, transplants may also be used to treat genetic blood disorders. In addition, they can aid patients in recovering from cancer treatment or allow them to tolerate it more effectively.

Precisely what is a stem cell?

Stem cells are specialised cells that can mature into different types of cells depending on your body’s needs. You can find them throughout your body, including in your bone marrow. Hematopoietic stem cells in the bone marrow divide constantly to produce all the different types of blood cells. Hematopoietic stem cells can differentiate into the following types of cells:

• Red blood cells carry oxygen throughout the body 
• Platelets are a component of blood that helps blood clot 
• White blood cells are an immune system component that helps fight infections 

It is critical to understand that any disease or condition that affects the bone marrow's ability to produce new blood cells can have serious health consequences. A bone marrow transplant may be an effective treatment for such conditions.

In what way do stem cell transplants work?

A successful stem cell transplant begins with harvesting healthy bone marrow from the patient or donor. Under general anaesthesia, a large needle is used to remove bone marrow from the pelvis of the patient or donor. Once bone marrow has been harvested, it can be frozen and stored. Like a blood transfusion, it is thawed and injected into the patient when it is ready for use. Healthy stem cells migrate to the bone marrow and produce blood cells.

Stem cell transplantation can be divided into two types:

1. Autologous stem cell transplant

   An autologous stem cell or bone marrow transplant involves healthy harvesting cells from a patient's bone marrow. Once the bone marrow has been harvested, it is frozen and stored until it is ready to be used. As part of the preparation for the transplant, the patient undergoes a 'conditioning regimen'. These patients may receive high-dose chemotherapy or radiation therapy as part of this regimen. During these treatments, cancer cells are destroyed, but bone marrow cells are also eliminated. This is where transplants come into play. Stem cells from the patient's blood are injected into the patient. Upon taking up residence in the body, these cells restore the body's ability to produce blood cells.

   It is used to treat diseases such as lymphoma and multiple myeloma. The patient's cells are used in autologous transplants, so there is little to no risk of rejection or graft-versus-host disease (GVHD). Therefore, it is safer than allogeneic transplants.

2. Allogeneic stem cell transplant

   In allogeneic bone marrow or stem cell transplants, donor stem cells treat blood cancers that affect the bone marrow, such as leukaemia. Transplanting cells come from a donor whose tissue matches the patient most closely. Following chemotherapy, donor cells are injected into the patient. Aside from restoring the body's ability to produce blood, allogeneic stem cell transplantation can directly aid in the fight against cancer.

   By generating a heightened immune response, the donated cells can identify and kill cancer cells, sometimes more effectively than the patient's immune cells. This is referred to as the graft-versus-cancer effect, which can assist in the fight against cancer. There is an increased risk of rejection or GVHD associated with allogeneic stem cells.

Finding stem cell donors

To ensure that allogeneic transplants are successful, the patient must be matched with a donor whose human leukocyte antigen (HLA) proteins closely match their own. Your body uses HLA proteins to distinguish normal cells from foreign cells on the surface of your cells. There is an increased risk of GVHD if the HLA proteins of the donor are not a suitable match for the patient's HLA proteins.

The HLA typing process matches stem cell transplant patients with eligible donors. During HLA typing, blood samples from a patient are compared with samples from family members or a donor registry. The ideal match is usually a first-degree relative (child, sibling, or parent). Approximately 75% of patients do not have suitable family donors and must obtain cells from an unrelated donor. A registry program is used to locate stem cell donors. Finding a suitable donor may take several weeks or longer.

There are other options available if a suitable donor cannot be found, including:

• Transplants use haploidentical bone marrow from a first-degree relative (such as a parent, sibling, or child) that is a half-match for the patient. In recent years, haploidentical transplants have become safer and have the benefit of reducing waiting times
• Transplantation of umbilical cord blood: During pregnancy, the umbilical cord connects the fetus to the placenta. Hematopoietic stem cells are contained in them. The umbilical cord is no longer required once the baby is born. Stem cells from the cord can be harvested and stored in a cord blood bank for use in cancer treatment

Side effects of stem cell transplantation

Because a patient's immune system is destroyed before a stem cell transplant, it takes about six months to a year for the immune system to recover and produce new healthy blood cells. Transplant patients must take precautions during this period since they are at an increased risk of infections. Medications such as antibiotics may be used in this regard.

There are also the following side effects:

• Graft versus host disease (GVHD) occurs when your immune system attacks cells from the donor or when the donor's cells attack yours. GVHD can develop immediately after the transplant or more than a year later 
• A higher risk of bleeding 
• Anemia: It may be necessary to administer a blood transfusion to some patients who have persistently low red blood cell counts 
• Fatigue 
• Mouth sores 
• Infertility 
• Secondary malignancy  

Following a transplant, you will need to regularly follow up with your doctor to determine how your body and immune system respond. If you experience any of the above symptoms or have any concerns, please inform your physician immediately so that any concerns can be identified as early as possible.