Scientists have narrowed in on a subset of blood stem cells that appear to be exclusively responsible for repopulating the entire blood and immune system after a transplant, a discovery that could someday lead to improvements in blood stem cell transplantation and targeting of cell and gene therapies. The findings were reported yesterday in Science Translational Medicine.
While the use of CD34-positive hematopoietic cells for stem cell transplantation is currently common practice, not all CD34-positive cells contribute to engraftment. The current study, performed by scientists at the Fred Hutchinson Cancer Research Center, identified two additional markers to precisely identify the type of stem cells that contribute to rapid healing after transplantation.
The scientists worked with non-human primates, tracking hundreds of cells in the blood following transfusion and identifying a CD34+CD45RA−CD90+ stem cell phenotype to be involved in short-term and ongoing blood and immune cell healing. This type of cell represents approximately 5% of all blood stem cells.
The findings of a single type of cell that rebuilds the blood and immune system came as a surprise as the scientists previously thought it likely that multiple types of stem cells were involved in these processes.
The current study was done in nonhuman primates, but corresponding subtypes of human blood cells were also identified and tested in vivo to reveal similar functions to the animal cells.
The researchers hope to someday use these findings to create treatments that isolate a subset of stem cells from human blood samples, engineer them for therapeutic purposes and reintroduce them into the patient where they would divide and differentiate into healthy cells. This type of treatment could be helpful in treating hemoglobin disorders, AIDS, blood cancers and graft-versus-host disease. The team’s next steps will be to set up clinical trials to test these treatments in humans.