Stem Cells May Offer Stroke-Damaged Brain Protection Against Itself
By Aalok Mehta
October 13, 2008
Stem cells can drastically reduce the amount of damage following a stroke by limiting the body’s natural “overreaction” to the trauma, a new animal study has found.
Scientists have long known that stem cells seem to offer some protection against stroke damage, but how they did it was not clear. Perhaps the stem cells replace the dying neurons and replicate their functions, many experts suggested.
But stem cells instead appear to alter the expression of dozens of genes to dramatically tamp down the body’s immune and inflammatory responses, according to research by Darwin Prockop, director of the Texas A&M University Health Science Center's Institute for Regenerative Medicine, and colleagues.
While these reflexive responses help the body recover from injury, they also coax immune cells to damage or destroy nearby healthy tissue, a particular problem for sensitive brain cells.
“These responses are excessive—off the scale,” Prockop says. “If you can tone down some of these, you can avoid many of the terrible effects of stroke.”
Prockop and his team blocked blood flow through the carotid artery in mice to cause a stroke. A day later, the researchers implanted stem cells derived from human bone marrow. The treatment reduced the overall neuron damage by 60 percent compared with that seen in untreated animals.
The stem cells altered the expression of more than 10 percent of the approximately 600 genes activated during stroke recovery, many of them directly related to immune and inflammatory responses, the team found.
“This is a new paradigm for how stem-like cells work. They’re not replacing cells, though they can do that in a limited amount.” Prockop says. “It’s really about repairing cells rather than replacing them. That we can stop injured tissue from destroying itself—that was a big surprise.”
The results appeared in a paper published online by the Proceedings of the National Academy of Sciences on Sept. 15; the research was conducted while Prockop was a biochemistry professor at Tulane University.