Researchers at Technische Universität München (TUM) have now shown that an unfavorable configuration of bacterial networks in the gut really can cause inflammation. As part of the study, they transplanted the intestinal microbiome from sick animals into the intestines of germ-free mice. These mice developed symptoms specific to Crohn's disease in their small intestine.

"Although we used mice that had an increased genetic disposition towards Crohn's-type inflammation, they did not develop symptoms until we implanted the intestinal bacteria of affected animals," explains Prof. Dirk Haller, TUM Chair of Nutrition and Immunology.

Dysbiosis: a cause of chronic inflammation

One key finding in the study was that chronic IBD is not caused by individual types of bacteria. "It has a lot more to do with the bacterial communities present," says Haller. "It would appear that some combinations of bacteria are 'dysbiotic' -- or imbalanced -- and their characteristics can now be explained."

The research team was also able to shed more light on the role of Paneth cells -- a type of cell found in the epithelial lining of the small intestine. These glandular cells play a role in the gut's immune defense. It has been known for a while that these cells die in cases of Crohn's disease -- but it was not clear whether this cell death triggers the disease or microbial imbalance.

The results of the study indicate that the loss of function in Paneth cells is a result of the inflammation, rather than a cause.

Continued development of an unusual treatment

The research team hope that their findings can help increase the range of treatments available for Crohn's disease. The disease is relatively common: in the developed world, around 40 in 100,000 people will develop Crohn's disease. In Germany, 350,000 people are thought to suffer from the condition.

For many patients, medication only provides short-term relief. "In most cases, the inflammation returns after a time," says Haller. "Stool transplants have already proven effective for a number of intestinal diseases. However, this unusual treatment has yet to deliver conclusive results in patients with Crohn's disease and ulcerative colitis. The findings from our study will help provide a scientific basis for improving this approach -- and then it could work."

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Materials provided by Technische Universitaet Muenchen. Note: Content may be edited for style and length.

Journal Reference:

1. M. Schaubeck, T. Clavel, J. Calasan, I. Lagkouvardos, S. B. Haange, N. Jehmlich, M. Basic, A. Dupont, M. Hornef, M. v. Bergen, A. Bleich, D. Haller. Dysbiotic gut microbiota causes transmissible Crohn's disease-like ileitis independent of failure in antimicrobial defence. Gut, 2015; DOI: 10.1136/gutjnl-2015-309333