Microglia cells are active players in regulating synaptic development and plasticity in the brain. However, how they influence the normal functioning of synapses is largely unknown. In this study, we characterized the effects of pharmacological microglia depletion, achieved by administration of PLX5622, on hippocampal CA3-CA1 synapses of adult wild type mice. Following microglial depletion, we observed a reduction of spontaneous and evoked glutamatergic activity associated with a decrease of dendritic spine density. We also observed the appearance of immature synaptic features and higher levels of plasticity. Microglia depleted mice showed a deficit in the acquisition of the Novel Object Recognition task. These events were accompanied by hippocampal astrogliosis, although in the absence ofneuroinflammatory condition. PLX-induced synaptic changes were absent in Cx3cr1−/− mice, highlighting the role of CX3CL1/CX3CR1 axis in microglia control of synaptic functioning. Remarkably, microglia repopulation after PLX5622 withdrawal was associated with the recovery of hippocampal synapses and learning functions. Altogether, these data demonstrate that microglia contribute to normal synaptic functioning in the adult brain and that their removal induces reversible changes in organization and activity of glutamatergic synapses.
The work was supported by a grant from MIUR (PRIN 2017HPTFFC_003) to Davide Ragozzino and in part by funds to Silvia Di Angelantonio (CrestOptics-IIT JointLab for Advanced Microscopy) and Daniele Caprioli (Istituto Pasteur-Fondazione Cenci Bolognetti). Bernadette Basilico, and Laura Ferrucci were supported by the PhD program in Clinical-Experimental Neuroscience and Psychiatry, Sapienza University, Rome; Caterina Sanchini was supported by the PhD program in Life Science, Sapienza University, Rome and by the Italian Institute of Technology, Rome. The authors thank Alessandro Felici, Claudia Valeri, Arsenio Armagno, and Senthilkumar Deivasigamani for help with animal husbandry and transgenic colonies management. They also wish to thank Piotr Bregestovski and Michal Schwartz for helpful discussions and criticism. PLX5622 was provided under Materials Transfer Agreement by Plexxikon Inc. (Berkeley, CA). Open Access Funding provided by Universita degli Studi di Roma La Sapienza within the CRUI-CARE Agreement.
Basilico B, Ferrucci L, Ratano P, et al. Microglia control glutamatergic synapses in the adult mouse hippocampus. Glia. 2022;70(1):173-195. doi:10.1002/glia.24101
Basilico, B., Ferrucci, L., Ratano, P., Golia, M. T., Grimaldi, A., Rosito, M., … Ragozzino, D. (2022). Microglia control glutamatergic synapses in the adult mouse hippocampus. Glia. Wiley. https://doi.org/10.1002/glia.24101
Basilico, Bernadette, Laura Ferrucci, Patrizia Ratano, Maria T. Golia, Alfonso Grimaldi, Maria Rosito, Valentina Ferretti, et al. “Microglia Control Glutamatergic Synapses in the Adult Mouse Hippocampus.” Glia. Wiley, 2022. https://doi.org/10.1002/glia.24101.
B. Basilico et al., “Microglia control glutamatergic synapses in the adult mouse hippocampus,” Glia, vol. 70, no. 1. Wiley, pp. 173–195, 2022.
Basilico B, Ferrucci L, Ratano P, Golia MT, Grimaldi A, Rosito M, Ferretti V, Reverte I, Sanchini C, Marrone MC, Giubettini M, De Turris V, Salerno D, Garofalo S, St‐Pierre M, Carrier M, Renzi M, Pagani F, Modi B, Raspa M, Scavizzi F, Gross CT, Marinelli S, Tremblay M, Caprioli D, Maggi L, Limatola C, Di Angelantonio S, Ragozzino D. 2022. Microglia control glutamatergic synapses in the adult mouse hippocampus. Glia. 70(1), 173–195.
Basilico, Bernadette, et al. “Microglia Control Glutamatergic Synapses in the Adult Mouse Hippocampus.” Glia, vol. 70, no. 1, Wiley, 2022, pp. 173–95, doi:10.1002/glia.24101.
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