Genetically induced brain inflammation by deletion transiently benefits from microglia depletion.

Reduced expression of 2'-3'-cyclic nucleotide 3'-phosphodiesterase () in humans and mice causes white matter inflammation and catatonic signs. These consequences are experimentally alleviated by microglia ablation colony-stimulating factor 1 receptor (CSF1R) inhibition using PLX5622. Here we address for the first time preclinical topics crucial for translation, most importantly ) the comparison of 2 long-term PLX5622 applications (prevention and treatment) 1 treatment alone, ) the correlation of catatonic signs and executive dysfunction, ) the phenotype of leftover microglia evading depletion, and ) the role of intercellular interactions for efficient CSF1R inhibition. Based on our mouse model and time-lapse imaging, we report the unexpected discovery that microglia surviving under PLX5622 display a highly inflammatory phenotype including aggressive premortal phagocytosis of oligodendrocyte precursor cells. Interestingly, ablating microglia requires mixed glial cultures, whereas cultured pure microglia withstand PLX5622 application. Importantly, 2 extended rounds of CSF1R inhibition are not superior to 1 treatment regarding any readout investigated (magnetic resonance imaging and magnetic resonance spectroscopy, behavior, immunohistochemistry). Catatonia-related executive dysfunction and brain atrophy of mice fail to improve under PLX5622. To conclude, even though microglia depletion is temporarily beneficial and worth pursuing, complementary treatment strategies are needed for full and lasting recovery.-Fernandez Garcia-Agudo, L., Janova, H., Sendler, L. E., Arinrad, S., Steixner, A. A., Hassouna, I., Balmuth, E., Ronnenberg, A., Schopf, N., van der Flier, F. J., Begemann, M., Martens, H., Weber, M. S., Boretius, S., Nave, K.-A., Ehrenreich, H. Genetically induced brain inflammation by deletion transiently benefits from microglia depletion.