Polarized macrophage functions are affected differentially after CSF-1R inhibition with PLX5622

PLX5622 is a colony stimulating factor 1 receptor (CSF-1R) inhibitor that is known to deplete microglial cells in vivo. Recently its effects on macrophages (M phi) were also observed in vivo. Therefore, we performed this study to assess its in vitro effects on the differentiation and functions of polarized M phi derived from different tissues. Our findings show that addition of PLX5622 early on after ex vivo isolation hinders M phi differentiation and survival. However, its addition post M phi differentiation did not significantly affect the viability. Furthermore, PLX5622 affects certain functions and degree of polarization of IL-4 (M2a) M phi but not polarization of M1-like M phi. Our study provides novel aspects on the application of PLX5622 to study M phi functions in vitro, where polarization is affected by CSF-1R signalling and provides distinctive evidence to its ability to affect certain populations of M phi during in vitro differentiation and maturation.