The proliferation and activation of microglial cells is a hallmark of several
neurodegenerative conditions. This mechanism is regulated by the activation of the Colony-Stimulating Factor 1 Receptor (CSF1R), thus providing a target that may prevent the progression of conditions such as Alzheimer’s disease (AD). However, the study of microglial proliferation in AD and validation of the efficacy of CSF1R-inhibiting strategies has not yet been reported. In this study we found increased proliferation of microglial cells in human AD, in line with an increased upregulation of the CSF1Rdependent pro-mitogenic cascade, correlating with disease progression. Using a transgenic model of Alzheimer’s-like pathology (APPswe, PSEN1dE9; APP/PS1) we define a CSF1R-dependent progressive increase in microglial proliferation, in the proximity of Amyloid β (Aβ) plaques. Prolonged inhibition of CSF1R in APP/PS1 mice by an orally available tyrosine kinase inhibitor (GW2580) resulted in the blockade of microglial proliferation and a shift in the microglial inflammatory profile to an antiinflammatory phenotype. Pharmacological targeting of CSF1R in APP/PS1 mice resulted in an improved performance in memory and behavioural tasks and a prevention of synaptic degeneration, although these changes were not correlated with a change in the number of Aβ plaques. Our results provide proof of the efficacy of CSF1R inhibition in a model of AD, and validate the application of a therapeutic strategy aimed at modifying CSF1R activation as a promising approach to tackle microglial activation and the progression of Alzheimer’s disease.