Two teams of researchers funded in part by the National MS Society report success in stimulating the repair of nerve-insulating myelin in mouse models of MS. Myelin is a major target of immune attacks in MS, and although these are early results and further work is needed, these findings show some promise for strategies to repair damage and restore function for people with multiple sclerosis.
Background: In MS, myelin, the material that surrounds and protects nerve fibers, is damaged in the brain and spinal cord, and so are the cells that make myelin, called oligodendrocytes. Though the replacement cells that could repair myelin, called oligodendrocyte precursor cells (OPCs), exist in the brain, in MS they cannot adequately repair the damaged myelin.
Stem Cell Study: Lu Chen, PhD, Thomas Lane, PhD (University of California, Irvine) and colleagues report that administering neural precursor cells (nerve stem cells) to mice with MS-like disease reduced inflammation, decreased myelin damage, and increased myelin repair.
The team injected the stem cells into the spinal cord of mice with an MS-like disease induced by a virus. Although the stem cells were rejected by the body, and were not detectable within eight days after transplant, they were effective nevertheless in reducing the disease. Improvements in motor abilities of the treated mice were still apparent after six months.
The team noted that improvements went along with an increase in a type of immune cell called “regulatory T cells,” or “Tregs.” To test whether the Tregs contributed to the improvements, they blocked Tregs activity, which reduced the stem cells treatments’ impact.
The team speculates that the stem cells may be stimulating the immune environment in a way that activates mouse OPCs, even though the stem cells themselves do not turn into myelin-making OPCs. They are now investigating this idea further to discover the factors released by the stem cells. Ultimately, this information could contribute to the development of stem cell therapies and even cell-free therapies that stimulate recovery in people with MS.
Stimulating Resident Cells: Jessica Williams, PhD, Robyn S. Klein, MD, PhD, and colleagues (Washington University School of Medicine) report that targeting a signaling receptor (docking site) called “CXCR7” on immature oligodendrocytes in mice enhances myelin repair.
Dr. Klein’s team focused on a messenger protein (chemokine) that interacts with the immature OPCs. They studied mice that were given a toxin called cuprizone, which mimics myelin damage that occurs in the brain during MS. Once cuprizone is withdrawn, myelin repair occurs. The team found that CXCR7 activity increased during myelin damage, and then reduced with myelin repair. When the team administered an experimental compound that inhibits CXCR7, the numbers of OPCs, as well as mature oligodendrocytes, increased within myelin-damaged areas. Myelin repair was enhanced.
These data suggest that CXCR7 might serve as an important therapeutic target to promote myelin repair. Since these studies were conducted in mice, further research is necessary to ultimately determine whether this approach might be an effective approach for stimulating myelin repair in people with MS.
Conclusion: Achieving success in the Society’s priority area of nervous system repair would provide life-changing advances for people with MS.