Bone marrow is the soft, fatty tissue inside your bones. The bone marrow produces blood cells. Stem cells are immature cells in the bone marrow that give rise to all of your different blood cells.
A bone marrow transplant is a medical procedure performed to replace bone marrow that has been damaged or destroyed by disease, infection, or chemotherapy. This procedure involves transplanting blood stem cells, which travel to the bone marrow where they produce new blood cells and promote growth of new marrow.
Bone marrow also contains immature blood-forming stem cells known as hematopoietic stem cells, or HSCs. Most cells are already differentiated and can only make copies of themselves. However, these stem cells are unspecialized, meaning they have the potential to multiply through cell division and either remain stem cells or differentiate and mature into many different kinds of blood cells. The HSC found in the bone marrow will make new blood cells throughout your lifespan.
Bone marrow transplants are performed when a person’s marrow isn’t healthy enough to function properly. This could be due to chronic infections, disease, or cancer treatments. Some reasons for a bone marrow transplant include:
There are two major types of bone marrow transplants. The type used will depend on the reason you need a transplant.
Autologous transplants involve the use of a person’s own stem cells. They typically involve harvesting your cells before beginning a damaging therapy to cells like chemotherapy or radiation. After the treatment is done, your own cells are returned to your body.
This type of transplant isn’t always available. It can only be used if you have a healthy bone marrow. However, it reduces the risk of some serious complications, including GVHD.
Allogeneic transplants involve the use of cells from a donor. The donor must be a close genetic match. Often, a compatible relative is the best choice, but genetic matches can also be found from a donor registry.
Allogeneic transplants are necessary if you have a condition that has damaged your bone marrow cells. However, they have a higher risk of certain complications, such as GVHD. You’ll also probably need to be put on medications to suppress your immune system so that your body doesn’t attack the new cells. This can leave you susceptible to illness.
When your doctor thinks you’re ready, you’ll have the transplant. The procedure is similar to a blood transfusion.
If you’re having an allogeneic transplant, bone marrow cells will be harvested from your donor a day or two before your procedure. If your own cells are being used, they’ll be retrieved from the stem cell bank.
Cells are collected in two ways.
During a bone marrow harvest, cells are collected from both hipbones through a needle. You’re under anesthesia for this procedure, meaning you’ll be asleep and free of any pain.
During leukapheresis, a donor is given five shots to help the stem cells move from the bone marrow and into the bloodstream. Blood is then drawn through an intravenous (IV) line, and a machine separates out the white blood cells that contain stem cells.
A needle called a central venous catheter, or a port, will be installed on the upper right portion of your chest. This allows the fluid containing the new stem cells to flow directly into your heart. The stem cells then disperse throughout your body. They flow through your blood and into the bone marrow. They’ll become established there and begin to grow.
The port is left in place because the bone marrow transplant is done over several sessions for a few days. Multiple sessions give the new stem cells the best chance to integrate themselves into your body. That process is known as engraftment.
Through this port, you’ll also receive blood transfusions, liquids, and possibly nutrients. You may need medications to fight off infections and help the new marrow grow. This depends on how well you handle the treatments.
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