In vivo small animal bioluminescence imaging (BLI), pioneered by one of our colleagues from Stanford (Chris Contag) for monitoring tumor cell invasion and progression in mice, was adopted by our lab for stem cell studies of regeneration (measured as engraftment). BLI relies on optical imaging of cells expressing light generated by enzymes such as firefly luciferase.
BLI allows stem cell function to be monitored non-invasively with a CCD camera repeatedly over time (months) in the same mice.
BLI enables regeneration to evaluated as a function of the contribution of transplanted muscle stem cells to muscle through their expansion, myofiber formation, and stem-cell repopulation in live mice. Our approach combines our ability to purify muscle stem cells by FACS from Luciferase transgenic mice, which express the luciferase enzyme reporter in muscle stem cells and their progeny.
Luminescence signal is detected in mice that received muscle stem cell transplants following injection of D-Luciferin, which is degraded by luciferase resulting in light emission that is detected within an IVIS Bioluminescence imaging instrument. This BLI assay approach is highly sensitive as it can detect as few as 10 to 100 cells in recipient mice. Due to its sensitive and quantitation reliability (it correlates well with stem cell engagement assayed histologically or by FACS), BLI can be used to screen for and discover novel treatments to enhance muscle stem cell function.
* Sacco et al. Nature, 2008 (PDF)
* Lutolf et al., Nature, 2009
* Gilbert et al., Science, 2010 (PDF)