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uni'wissen 02-2015_ENG

Prof. Dr. Marco Prinz studied medicine and earned his doctorate in Berlin and completed his habilitation qualification in neuropatho- logy in Göttingen. He was a postdoctoral research fellow at the Institute of Neuropa- thology of the University of Zurich, Switzerland, and has served since 2008 as medical director of the Institute for Neuropathology at the Freiburg University Medical Center. Prinz is also an associate member of the Cluster of Excellence BIOSS Centre for Biological Signal- ling Studies of the University of Freiburg. He has received a number of awards for his research, including the H. G. Creutzfeld Prize, the Young Investigator Award from the International Cytokine Society, and, most recently, the 100,000-euro Sobek Research Prize. Photo: private Further Reading Erny, D. / Hrabe de Angelis, A. L. / Jaitin, D. / Wieghofer, P. / Staszewski, D. E. / Keren-Shaul, H. / Mahlakoiv, T. / Jakobshagen, K. / Buch, T. / Schwierzeck, V. / Utermöhlen, O. / Chun, E. / Garrett, W. S. / McCoy, K. D. / Diefenbach, A. / Staeheli, P. / Stecher, B. / Amit, I. / Prinz, M. (2015): Host microbiota constantly control maturation and function of microglia in the central nervous system. In: Nature Neuroscience 18, pp. 965–977. Prinz, M. / Priller, J. (2014): Microglia and brain macrophages in the molecular age: from origin to neuropsychiatric disease. In: Nature Review Neuroscience 15/5, pp. 300–312. Hanisch, U.K. / Kettenmann, H. (2009): Mikroglia: Hausmeister mit Lizenz zum Töten. In: Gehirn & Geist 5/2009, pp. 54–59. central nervous system and protecting it from germs and toxins. The idea that messages from the intestines could be important for processes in the brain therefore sounds absurd at first – and yet, precisely this seems to be the case. Prinz’s team studied mice whose intestines were either populated with bacteria as normal or completely bacteria-free. “The microglia in the bacteria-free mice were much larger than those with an intestinal flora, and they were also more numerous.” In addition, the external arms of the microglia in the bacteria-free mice suddenly touched each other. The researchers had previ- ously only known microglia networks in which the cells respect each other and do not get in each other’s way. This led the scientists to con- clude that the maturation of the microglia must be dependent on the intestinal bacteria. And on top of that, there seems to be constant communi- cation of sorts between the intestines and the microglia. Signals from the Intestines “We removed the bacteria from mice that initially had a normal intestinal flora and then later added just a few strains of bacteria,” explains Prinz. “We were able to see the effect this had: the microglia show a real reaction to what happens in the intestines.” Carbohydrates and fibers in particular seem to have a positive effect on the function of the microglia – they are converted into short-chain fatty acids in the intestine. But how can the brain receive constant signals from the intestines? Prinz and his team suspected certain kinds of receptors to be the cause, but this turned out not to be the case: “So now we are back to square one.” The scientists are also interested in the potential link between the breakdown of nerve cells in the brains of multiple sclerosis patients and the intestinal bacteria. If they succeed in substantiating their findings, it would mean that anyone can influence the function of their microglia through a change in diet. How do the microglia communicate with each other and with the intestines? What happens with the gardeners responsible for keeping house in the brain when they themselves die? Do they die at all, or do they just go into a state of rest? Where do the microglia come from if they are already there before we are born but multiply throughout our lives, as scientists have observed? Is there a kind of mother line? “There remains much to be discovered,” says Marco Prinz, “and we’re happy to be at the forefront of the developments.” Lentils for the brain: Carbohydrates and fibers seem to have a positive effect on the function of the microglia. Photo: Printemps/Fotolia 15uni wissen 02 2015 15uni wissen 022015