Stem cells restore monkeys’ movement after spinal cord injury

By Shelly Fan (Singularity Hub),

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Stem cell therapy is highly attractive in its intuitive simplicity: you clean out injured cells, plop down a gang of healthy replacements, sit back, and wait for the body to heal itself.

For spinal cord injuries the potential of stem cells to restore movement seems especially within reach.

But as it happens, the body isn’t quite the simple find-and-replace system. Stem cells when transplanted alone often don’t take, dying off inside the host’s hostile environment before they have a chance to restore function.

For the last three decades, neuroscientists have been scratching their heads, testing cocktail after cocktail of special molecules that can boost stem cell survival. And while there have been successes in rodent models, scaling the therapy to work in primates—a critical step towards human trials—has floundered.

Until now. Last month, a “landmark” study published in Nature Medicinedetailed a recipe for transplanted human stem cells to survive and integrate inside the injured spines of monkeys.

Nine months after surgery, the cells extended hundreds of thousands of branches that formed synapses with the monkey’s surviving spinal cord neurons. What’s more, the hosts’ spinal neurons also welcomed the human cells as their own, reaching out to form new connections that restored the animal’s ability to grasp objects.

“The growth we observe from these cells is remarkable—and unlike anything I thought possible even ten years ago,” said lead author Dr. Mark Tuszynski at the University of California, San Diego Translational Neuroscience Institute. “We definitely have more confidence to do this type of treatment in humans.”