A group of paralyzed mice were able to completely recover and run around again after being injected with human stem cells. Results from this study show promise for developing new therapies to stop the progression of multiple sclerosis in humans, and perhaps even one day reverse its effects.

Stem cells have once again shown how truly fascinating they really are. In a recent study published in Stem Cell Reports, researchers took a group of mice crippled by an autoimmune disease similar to multiple sclerosis (MS) and injected human stem cells into their spinal cords. What happened next surprised everyone. "Tom called me up and said, 'You're not going to believe this. He sent me a video, and it showed the mice running around the cages. I said, 'Are you sure these are the same mice?'" study co-leader Jeanne Loring, a professor of developmental neurobiology at TSRI, explained in a press release.

Groundbreaking Results

This is the first time an experiment on paralyzed mice has yielded such amazing results. "When we implanted the human cells into mice that were paralyzed, they got up and started walking a couple of weeks later, and they completely recovered over the next several months," Loring added.

The mice continued to walk even after their bodies eventually rejected the human cells. The researchers believe this suggests the human stem cells had released a protein, which acted like a catalyst, enabling the prevention of MS even after the actual healthy cells were gone. "Once the human stem cells kick that first domino, the cells can be removed and the process will go on because they've initiated a cascade of events," Ron Coleman, a graduate student who took part in the study, explained in the press release.

What Happened

MS is a chronic and unpredictable disease that affects the central nervous system. It is considered an autoimmune condition because MS causes an individual’s immune system to incorrectly attack healthy tissue in the CNS.

The implanted human stem cells stimulated the mice’s bodies to create white blood cells known as regulatory T cells. These T cells were able to stop demyelination of nerve fibers. In demyelination, the protective nerve sheath, called myelin, is stripped away. Myelin works similarly to plastic insulation on an electrical wire. It both protects the nerve cells and allows them to quickly send signals. The human stem cells not only stopped the progression of the mice’s autoimmune disease, but they were also able to reserve the damage that had already been done. Researchers observed that the human cells prompted the mice’s to remyelinate. In remyelination, the nerve cell’s protective sheaths that have been stripped away are replaced.

A Deviation from the Norm

The particular human cells injected into the mice were actually created by accident. One researcher decided to transfer the stem cells from one petri dish to another while they were still developing into neural precursor cells. It was this one deviation from the norm, called passaging, that made all the difference. Coleman explains in the press release that passaging actually altered the type of proteins that the cells will express. "If we had used common techniques to create the cells, they wouldn't have worked," Loring said.

What This Means for MS Patients

The team is working to understand exactly how the human stem cells were able to help the mice recover from their paralysis. They know the cells released a protein and are working on discovering what particular protein this is. Knowing what protein is able to reverse the effects of MS means that future treatments for the condition will no longer need to use human stem cells. The protein could be used in a drug or directly infused to the spinal cords of MS patients.

Current treatment options for MS work to suppress demyelination, the autoimmune response. Sadly, these treatments are not completely effective and often have serious side effects. The stem cell treatment that was explored in this study holds the possibility of being a permanent cure for the condition.

Knowing that stem cell implantation works is only the first step toward a cure for MS. Although there is still work to be done, researchers working on this study believe they are closer to one day developing new and improved human treatments for the condition. “We’re on the trail now of what these cells do and how they work,” Loring concluded.

Source: Chen L, Coleman R, Leang R, et al. Human Neural Precursor Cells Promote Neurologic Recovery in a Viral Model of Multiple Sclerosis. Stem Cell Reports. 2014.