WASHINGTON: Single adult stem cells can self-renew, repair damaged tissues in a live mammal, according to the latest research.
The transplanted adult stem cell and its differentiated descendants were found to restore functioning of hind limb muscle tissue damage in mice.
Adult stem cells used in the study, conducted by Stanford University, were isolated from a mixed population of satellite cells in the skeletal muscle of mice.
Skeletal adult muscle stem cells (MusSC), which live just under the membrane that surrounds muscle fibres, normally respond to tissue damage by giving rise to progenitor cells that become myoblasts, fusing into myofibers to repair tissue damage.
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". 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," said Blau. "It taught us so much more. We could see how the cells were responding, and really monitor their dynamics."
Sacco and Blau tracked each transplanted stem cell as it rapidly proliferated and engrafted its progeny into the irradiated muscle tissue, said a Stanford release.
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.
"We are thrilled with the results," said Sacco. "It's been known that these satellite cells are crucial for the regeneration of muscle tissue, but this is the first demonstration of self-renewal of a single cell."
The ability to isolate and then transplant skeletal adult muscle stems cells could have a wide impact in treating not only a variety of muscle wasting diseases such as muscular dystrophy but also severe muscle injuries or loss of function from aging and disuse.
The first demonstration that a single adult stem cell can self-renew in a mammal was presented this week at the American Society for Cell Biology in San Francisco.
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