Eventually, the work also could help guide transplantation procedures using other types of stem cells. Cao said an upcoming experiment will use the same technique to monitor transplanted neuronal stem cells. "We can monitor the fate of those stem cells and help evaluate transplantation protocols," he said. This type of approach could speed the development of stem cell transplantation therapies for disorders such as Parkinson's disease.
Cao and Christopher Contag, PhD, assistant professor of pediatrics, radiology, microbiology and immunology, and lead author of the paper, were able to follow the transplanted cells' travels because they all made a firefly protein called luciferase. This protein produces a dim light when it comes in contact with another molecule called luciferin. Unlike fireflies, mice don't normally make luciferin, but the recipient mice received doses of the molecule throughout the experiment. Once injected into the recipient mice - whose bone marrow had been destroyed by radiation - the luciferase-producing transplanted cells produced a faint glow. Like a campfire at a new settlement, this dim light pinpointed the cells' location.
Although the light from luciferase isn't bright enough to see by eye, an ultrasensitive video camera originally developed by Contag can detect the faint light and show researchers where the glowing cells have settled. The experiment highlighted a handful of stem cell resting places, including the spleen and the bone marrow in the vertebrae, thighbone, shinbone, skull, ribs and sternum, where stem cells were already known to produce new blood cells.
Of all the locations, the spleen and the vertebrae were the two most likely sites for the new cells to settle. These are also the two roomiest compartments, according to Contag. "Where the cells go initially seems to relate to the size of the compartment and its openness," he said. If th
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Contact: Mitzi Baker
650-725-2106
Stanford University Medical Center
15-Dec-2003