The first demonstration that a single adult stem cell can self-renew in a mammal was reported at the American Society for Cell Biology (ASCB) 48th Annual Meeting, Dec. 13-17, 2008 in San Francisco.
The transplanted adult stem cell and its differentiated descendants restored lost function to mice with hind limb muscle tissue damage.
The adult stem cells used in the study, conducted at Stanford University, were isolated from a mixed population of satellite cells in the skeletal muscle of mice.
The skeletal adult muscle stem cells (MusSC), which live just under the membrane that surrounds muscle fibers, normally respond to tissue damage by giving rise to progenitor cells that become myoblasts, fusing into myofibers to repair the tissue damage.
The scientists transplanted the MusSC into special immune-suppressed "nude" mice whose muscle satellite cells had been wiped out in a hind limb by irradiation.
The mice would only be able to repair injury if the transplanted MuSC "took." The scientists, Alessandra Sacco and Helen Blau, had genetically engineered the transplanted MusSC to express Pax7 and luciferase proteins. As a result, every transplanted cell glowed under ultraviolet light and was easy to trace.
"To be able to detect the presence of the cells by bioluminescence was really a breakthrough," says Blau. "It taught us so much more. We could see how the cells were responding, and really monitor their dynamics."
Through luminescent imaging as well as quantitative and kinetic analyses, Sacco and Blau tracked each transplanted stem cell as it rapidly proliferated and engrafted its progeny into the irradiated muscle tissue.
The scientists then injured the regenerated tissue, setting off massive waves of muscle cell growth and repair, and subsequently showed that the MuSC and descendents rescued the second animal's lost muscle healing function.
After isolating the luciferase-g
|Contact: Cathy Yarbrough|
American Society for Cell Biology