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 is the spongy, fatty tissue inside your bones. It creates the following parts of the blood:

• red blood cells, which carry oxygen and nutrients throughout the body
• white blood cells, which fight infection
• platelets, which are responsible for the formation of clots

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.

A bone marrow transplant replaces your damaged stem cells with healthy cells. This helps your body make enough white blood cells, platelets, or red blood cells to avoid infections, bleeding disorders, or anemia.

Healthy stem cells can come from a donor, or they can come from your own body. In such cases, stem cells can be harvested, or grown, before you start chemotherapy or radiation treatment. Those healthy cells are then stored and used in transplantation.