How do bone marrow transplants work, and what conditions do they treat?

A bone marrow transplant is actually a misnomer, as these procedures transplant stem cells, not the actual bones. Specifically, these procedures use hematopoietic stem cells (HSC), also known as blood-forming stem cells, to potentially cure an ever-expanding number of diseases.

There are three main cell types found inside a persons blood based on their function:

red blood cells: these cells carry oxygen throughout the body

platelets: these cells help form clots to stop bleeding

white blood cells: these cells lead the charge in fighting infections (also known as the immune system)

Each of these cell types, despite their different functions, shapes, sizes and lifespan, arise from the same source the hematopoietic stem cell, which constantly replenish each cell type. HSCs reside almost exclusively deep inside our bones in the center of the hard, protective shelter of calcium and other minerals. So, the marrow (soft, middle portion of our bones) can be thought of as the factory that supply each person with the blood cells needed to overcome infections, trauma, and to live a healthy, long life.

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When we perform a transplant, we are actually either using a patients own stem cells (autologous transplant) or stem cells from another human (allogeneic transplant), leading to the more appropriate name of hematopoietic stem cell transplant (HSCT). These transplants are most commonly used to treat and cure cancer.

Autologous transplants are used in the treatment of many types of solid tumors (such as brain tumors, germ cell tumors, neuroblastoma), where the tumor can only be effectively destroyed by giving very high doses of chemotherapy that also damage the patients own HSCs. Before giving a patient those high doses of chemotherapy, we collect his or her own HSCs with a process very similar to dialysis (we remove stem cells from their blood), and then freeze and store them in a specialized lab.

After the patient receives that high dose of chemotherapy, the treatment team then thaws the stem cells and infuses them back into the patient via a specialized catheter placed in his or her veins. The stem cells quickly return home and find the bone marrow space, and within 10 to 21 days, they will start making new white blood cells and platelets, followed by red blood cells.

Allogeneic transplants are performed for many types of leukemias or bone marrow failure syndromes (such as aplastic anemia or Fanconi anemia) where the patients own stem cells are broken and need to be replaced by a healthy humans stem cells. However, many other non-malignant conditions (not cancer) can be effectively cured with this procedure, as conditions that result from defects of different blood cell types (red blood cells, white blood cells or platelets) are corrected when the factory is replaced with a healthy donors stem cells.

This is an exciting time in the field of transplant, as we are now able to offer cures for many childhood diseases that historically are chronic and/or life-threatening. HSCT is now being offered to patients with sickle cell disease/thalassemia (red blood cells are defective), along with many conditions that are now called inborn errors of immunity (white blood cells are defective).

Among the more than 500 different genetic conditions that damage white blood cells include severe combined immunodeficiency (SCID), hemophagocytic lymphohistiocytosis (HLH), chronic granulomatous disease (CGD), and severe congenital neutropenia (SCN). Not only are the numbers of conditions potentially cured with HSCT rapidly growing, but the success rates and ability to prevent and treat complications of this procedure are improving exponentially as well. We are looking forward to offering these procedures to more children here at UVa Childrens.

To learn more about Dr. Roehrs and the care he provides, visit uvahealth.com/findadoctor/profile/philip-a-roehrs.

Dr. Philip Roehrs is the clinical director for pediatric stem cell transplant and cellular therapy at UVa Childrens and UVa Health.

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Ask the Expert: How do bone marrow transplants work, and what conditions do they treat? - The Daily Progress