May 23, 2012 12:00pm

Replacing dead or dysfunctional nerve cells with new, healthy ones derived from stem cells eases chronic pain in mice, a new study found.

Researchers from the University of California, San Francisco coaxed mouse embryonic stem cells into becoming mature nerve cells that could bridge gaps in the circuitry that triggers neuropathic pain.

One of the major causes of neuropathic pain is the loss of inhibitory control at the level of the spinal cord because of nerve loss or dysfunction, said study author Allan Basbaum, chairman of UCSFs department of anatomy. The idea was to replace or repopulate the spinal cord cells that provide that inhibition.

The same stem cells, destined to become inhibitory neurons that dampen the signals that cause pain, were previously shown to improve symptoms in a mouse model of epilepsy, Basbaum said. The question was whether we could take the exact same cells and put them in the spinal cord.

Before injecting the cells into the spinal cords of mice with neuropathic pain, the researchers labeled them with a fluorescent tracer to track the connections they made.

We were able to show how these cells integrate beautifully, Basbaum said, describingthe waythe transplanted cells looked and behaved like the mouses own.

Not only did the cells set up shop in the spinal cord, sending and receiving signals through a complex network of neurons, they also eased the neuropathic pain.

In four weeks, the animals condition completely disappeared, Basbaum said, adding that transplanted control cells that lacked the inhibitory properties of the stem-cell-derived neurons failed to ease the pain.

The clinical significance is that we think were actually modifying the disease, not just treating the symptoms, Basbaum said, adding that drugs currently used to ease neuropathic pain fail to treat the underlying problem. Instead of taking a drug to suppress the pain, were trying to normalize the circuit that was damaged by the disease or the injury. The cells repopulate, they integrate, and basically they treat the disease.

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Stem Cells Curb Chronic Pain in Mice