Twin Study Uncovers Gut Bacteria Linked to Multiple Sclerosis Development

A recent twin study has shed new light on the role of gut bacteria in the development of multiple sclerosis (MS), a chronic inflammatory disease of the central nervous system affecting over 280,000 people in Germany alone. Researchers discovered specific bacteria in the small intestine that may influence disease progression and demonstrated their pathogenic potential through innovative experiments.

Multiple sclerosis occurs when the body's immune cells mistakenly attack the protective myelin sheath surrounding nerve fibers, leading to symptoms such as vision problems, sensory disturbances, and paralysis. While these symptoms are diverse, the root causes of immune dysfunction in MS remain partially understood. It is known that genetic factors, environmental influences such as smoking, vitamin D deficiency, infections, and notably, microorganisms in the gut microbiome contribute to disease risk.

Previous research identified differences in gut bacterial composition between MS patients and healthy individuals, but interpreting these differences was challenging due to confounding factors like genetics and diet. To address this, scientists from multiple institutions conducted a study involving about 100 pairs of identical twins, where only one twin has MS. Since identical twins share nearly identical genes and often similar environmental backgrounds, this setup minimizes many variables.

The study analyzed stool samples from 81 twin pairs and found significant differences in 51 bacterial groups between twins with and without MS. Additionally, four twin pairs underwent sampling from their small intestines via enteroscopy—a novel approach, as most studies analyze stool samples alone, which provide limited insight into small intestine microbiota.

To test if these bacteria could cause MS-like symptoms, researchers introduced these samples into germ-free transgenic mice, which typically remain healthy but can develop MS-like disease when colonized with certain bacteria. Mice given intestinal bacteria from MS-affected twins mostly developed symptoms resembling MS, indicating the presence of disease-causing microorganisms.

Further analysis identified two bacteria, Lachnoclostridium sp. and Eisenbergiella tayi, belonging to the Lachnospiraceae family, which appeared to be directly involved in triggering MS-like disease in mice. These bacteria, previously associated with MS in larger studies, were functionally characterized for the first time, strengthening the evidence of their pathogenic role.

The findings suggest that a small number of specific gut bacteria might be pivotal in MS development, opening up potential for new treatments targeting these microorganisms. The study also highlights how lifestyle factors and the gut microbiome interact in MS risk, providing a foundation for future personalized therapies. Continued research is necessary to confirm these microorganisms' roles in humans and explore therapeutic interventions.

This groundbreaking research, published in "Proceedings of the National Academy of Sciences," emphasizes the significance of gut microbiota in MS and offers promising avenues for novel diagnostic and therapeutic strategies.