Stroke, the leading cause of serious, long-term disability in the United States, “is a disease where we do not have good treatments,” says neurosurgeon Gary Steinberg. Americans spend $30 billion a year on stroke recovery and rehabilitation, but doctors have no way to repair the damaged brain tissue.
That may soon change. Researchers in Steinberg’s lab have demonstrated that human fetal stem cells, when transplanted into the brains of laboratory rats with induced strokes, can migrate toward the damaged location and turn into neurons and support cells. On average, one-third of the stem cells survived, migrating up to 1.2 millimeters—“a very long distance,” Steinberg says. The researchers hypothesize the cells migrated in response to a chemical signal released by the animals’ brains to indicate damage.
“This is the first time human neuronal stem cells have been shown to survive, migrate and differentiate in an animal stroke model,” Steinberg says. The results were published last year in the Proceedings of the National Academies of Sciences with Tonya Bliss, a research associate, and Steven Kelly, now at the University of Bristol, as co-first authors.
The cells they used were isolated five years ago by StemCells Inc., a Palo Alto company founded by study co-author and pathology professor Irving Weissman. They are of a sufficient grade and quality to be used for future clinical trials in humans.
But first, Steinberg and his team have to show that the cells can restore motor or sensory functions in animals. “With advances in stem cell research, our [increased] understanding of how brains develop and repair themselves, and molecular biology and gene therapy techniques, we now are able to think about repairing tissue,” he says. Scientists, he points out, are pursuing many potential brain-tissue transplants as treatments for stroke; stem cell transplants may or may not be the most therapeutic.
The recent experiment “is very exciting work,” he adds. “But we still have quite a bit of preclinical work to do before we’re ready to start treating stroke patients using these cells.” He plans to investigate what enables the stem cells to survive in large numbers, migrate and differentiate, to see whether those processes can be enhanced.
Steinberg is already getting calls about the findings from people who’ve had strokes, as well as those who suffer from degenerative diseases or traumatic brain injuries. Clinical trials for stroke are a few years off, so he tells callers, “We’re not ready yet, but we’ll take your name.”
