Irving Weissman, MD, director of Stanford’s Institute for Stem Cell Biology and Regenerative Medicine, along with graduate student Agnieszka Czechowicz, recently published a fascinating review article in the May issue of the journal Immunology and Allergy Clinics of North America. The piece lays out how a one-time treatment with blood (hematopoietic) stem cells could provide a lifelong cure for autoimmune disease like lupus, rheumatoid arthritis and type 1 diabetes, could possibly cure AIDS, and could eliminate the ongoing need for anti-rejection drugs by organ transplant recipients.
How? If the immune cells that cause the problems can be eliminated and replaced with new blood and immune stem cells, those cells will spawn immune cells that don’t attack the body’s own tissues. Scientists have also shown that, at least in one case, stem cell transplantation from someone naturally resistant to AIDS could cure the disease in someone already infected. And if doctors giving someone an organ transplant also give them blood stem cells that are from the organ donor, the recipient’s body won’t try to reject the new organ.
But most of these therapies remain in the future. The problem? The blood stem cells that are already in the body don’t like to give up their territory to newcomers. In order to get transplanted stem cells to take up residence in the bone marrow, doctors have to wipe out some or all of the existing blood stem cells. For years, physicians have done exactly that to treat leukemias, by administering radiation or toxic chemicals that kill both cancerous cells and blood stem cells, and then adding back bone marrow from an immunologically compatible donor. But to do this, the patient has to be brought to the edge of death. Between 10 and 20 percent of those who get bone marrow transplantation will die, and even if the patient survives, the therapy also damages other tissues. As long as other treatments exist for many of these diseases, using a therapy so dangerous and damaging is hard to justify.
The article notes, however, that as we understand more about how blood stem cells work, we are seeing a possible path to much safer treatments. Researchers now know about molecular signals that can get native stem cells to vacate their niches for transplanted stem cells. In the future, these or other signals may become the basis for safer stem cell transplantation and open the door to new therapies for difficult, chronic immunological diseases.