For decades, bone marrow transplants have been a crucial treatment for blood cancers like leukemia and lymphoma — but scientists are still figuring out exactly how the transplants work.
Scientists from the Fred Hutchinson Cancer Research Center have now taken a huge step down that path by isolating a specific kind of stem cell that regrows a patient’s entire blood and immune system after a bone marrow transplant. The study was published Wednesday in the journal Science Translational Medicine.
Its findings shed new light on how the procedure works and could open the door to better treatments, including gene therapies, genome editing and more efficient stem cell transplants.
“These findings came as a surprise; we had thought that there were multiple types of blood stem cells that take on different roles in rebuilding a blood and immune system,” said Dr. Hans-Peter Kiem, a senior author of the study, in a press release. “This population does it all.”
The group of stem cells was differentiated by three proteins found on the surface of the cell type: CD34+ CD45RA– CD90+. They make up just five percent of all stem cells.
A bone marrow transplant — or stem cell transplant, to use a more generic term — generally happens after a patient’s bone marrow — which produces stem cells — is severely damaged or destroyed with radiation therapy or chemotherapy.
Then a new set of stem cells, either stored in advance or received from a donor, is transplanted into the patient’s body. Ideally, those cells rebuild the patient’s immune system and fight off any remnants of disease.
In the study, scientists examined how stem cells act during transplants in non-human primates. They followed the animals from the moment of the transplant and then watched as their donated stem cells grew and rebuilt their blood and immune systems over more than seven years. The subset of cells with those three proteins was responsible for the entire rebuilding process.
That knowledge could help make stem cell transplants or other, similar procedures more effective by letting doctors select just those kinds of stem cells to transplant. It could also be useful to developing new or more efficient stem-cell-based therapies.
Although this study was done in nonhuman primates, the scientist also discovered that humans have a similar kind of stem cell. There is evidence the human version acts in the same way as those seen in the study subjects.