One of the great promises of stem cell research is that doctors will find a way to isolate and modify patient’s stem cells so that they be reinjected into patients to treat their disease. Current examples include islet cell transplantation to treat diabetes, stem cells for treating heart failure, or engineered immune cells for treating cancer. However, a key challenge is to monitor the cells after they have been administered. Scientists need to be able to follow the transplanted cells, to see if they survive and engraft, home to areas of disease, and whether they are able to reestablish the activity needed to counteract disease.
We are developing novel tools to follow the fate and function of transplanted stem cells, based on a powerful medical camera called the PET scanner. PET imaging, or positron emission tomography, allows doctors to visualize the biology of cells in living organisms, including patients. Three ways to follow transplanted cells are being developed. In one, distinctive changes of functions inside cells are probed using radioactive small molecules. In a second approach, antibodies are used to detect cells based on distinctive markers on the surface of the transplanted cells. In the third approach, the transplanted cells themselves are “marked” using genes that cause the cells to emit a signal detectable by the PET scanner. Our interdisciplinary team has already demonstrated examples of these approaches and how they can be implemented in the clinic.
Tools for watching transplanted cells will provide highly valuable information that will refine research, accelerate development, and most importantly, allow physicians to directly monitor their activity and effects in patients.