2015 Research Highlights: Stem Cells Improve Nerve Injury Pain in Mice

A single injection of stem cells into the spinal canal provides rapid and long-lasting pain relief. Image of a stem cell. Credit: Robert M. Hunt, Wikimedia Commons.

A single injection of stem cells into the spinal canal provides rapid and long-lasting pain relief. Image of a stem cell. Credit: Robert M. Hunt, Wikimedia Commons.

An increasing number of animal studies have demonstrated that a specific kind of stem cell, known as bone marrow stromal cells (BMSCs), are a promising treatment for pain stemming from nerve injury and inflammation. A study published July 13 in the Journal of Clinical Investigation reported that a single injection of these cells into the spinal canal of mice can quickly relieve two different kinds of pain. The treatment effect lasts for several weeks and seems to occur without side effects. The study also explores the details of how BMSCs exert their pain-relieving effect.

“It’s very nice to see that BMSCs can reduce pain without side effects,” said Ke Ren, University of Maryland, Baltimore, US, who was not involved in the work. “These cells can really produce very long-lasting relief,” he added.

In the study, researchers led by Ru-Rong Ji and Gang Chen from Duke University in Durham, North Carolina, US, injured the sciatic nerve of mice, causing the animals to have a painful increase in sensitivity to both mechanical pressure and heat. However, just one day after the injection of BMSCs, the animals’ sensitivity levels were reduced, an effect that lasted more than five weeks. In addition, not only did the BMSCs lower pain levels, they also prevented some types of damage seen in nerve cells following nerve injury.

The researchers then showed that these effects were the result of the release of a growth factor called transforming growth factor beta 1 (TGF-β1) from BMSCs. “These stem cells act like little drug factories, producing TGF-β1,” explained Ji.

In subsequent experiments, the researchers also identified the “homing signal” released by injured neurons that attracts the BMSCs, and observed that the injected cells stick around at the site of injury for two months. By 2.5 months, the number of BMSCs was dramatically reduced, leading the researchers to conclude that the risk of tumor formation – a common concern with the use of stem cells in medicine – was unlikely.

Overall, the results demonstrate a major advantage of the BMSCs: they act very precisely, not only at the right place (the site of injury) and the right time (once the homing signal has been produced), but also for the right duration (a few months), said Ji.

It seems that BMSCs could also be used to treat pain in humans. A clinical trial that looked at the impact of the cells also showed a positive effect: patients with disc-related back pain had reduced pain and disability for two years following a single injection of BMSCs. “The treatment of pain with BMSCs [in humans] is very feasible,” said Ren. —Allison Marin 

To read about the research in more detail, see the related Pain Research Forum news story here.

Allison Marin, PhD, is a neuroscientist-turned-science writer who resides in Pittsburgh, Pennsylvania, US.