Murine iPSC-derived microglia and macrophage cell culture models recapitulate distinct phenotypical and functional properties of classical and alternative neuro-immune polarisation

Abstract

The establishment and validation of reliable induced pluripotent stem cell (iPSC)-derived in vitro models to study microglia and monocyte/macrophage immune function holds great potential for fundamental and translational neuro-immunology research. In this study, we first demonstrate that ramified CX(3)CR1(+) iPSC-microglia (cultured within a neural environment) and round-shaped CX(3)CR1(-) iPSC-macrophages can easily be differentiated from newly established murine CX(3)CR1(eGFP/+)CCR2(RFP/+) iPSC lines. Furthermore, we show that obtained murine iPSC-microglia and iPSC-macrophages are distinct cell populations, even though iPSC-macrophages may upregulate CX(3)CR1 expression when cultured within a neural environment. Next, we characterized the phenotypical and functional properties of murine iPSC-microglia and iPSC-macrophages following classical and alternative immune polarisation. While iPSC-macrophages could easily be triggered to adopt a classically-activated or alternatively-activated phenotype following, respectively, lipopolysaccharide + interferon gamma or interleukin 13 (IL13) stimulation, iPSC-microglia and iPSC-macrophages cultured within a neural environment displayed a more moderate activation profile as characterised by the absence of MHCII expression upon classical immune polarisation and the absence of Ym1 expression upon alternative immune polarisation. Finally, extending our preceding in vivo studies, this striking phenotypical divergence was also observed for resident microglia and infiltrating monocytes within highly inflammatory cortical lesions in CX(3)CR1(eGFP/+)CCR2(RFP/+) mice subjected to middle cerebral arterial occlusion (MCAO) stroke and following IL13-mediated therapeutic intervention thereon. In conclusion, our study demonstrates that the applied murine iPSC-microglia and iPSC-macrophage culture models are able to recapitulate in vivo microglia and monocyte/macrophage ontogeny and corresponding phenotypical/functional properties upon classical and alternative immune polarisation, and therefore represent a valuable in vitro platform to further study and modulate microglia and (infiltrating) monocyte immune responses under neuro-inflammatory conditions within a neural environment. ; This work was supported by research grant G091518N (granted to PP) of the Fund for Scientific Research-Flanders (FWO-Vlaanderen, Belgium), by a Methusalem research grant from the Flemish government (granted to HG and ZB), by funding received from the Belgian Charcot Foundation (granted to PP and DLB) and by the ASCID (Antwerp Study Centre for Infectious Diseases). AQ and EL are holders of a PhD studentship from the FWO-Vlaanderen. EVB is holder of a PhD studentship from the University of Antwerp. DLB is holder of a postdoctoral fellowship from the FWO-Vlaanderen. FM is supported by the Penis 2016 from the Health Department of Generalitat de Catalunya. Research in the Pasque lab is supported by the Research Foundation - Flanders (FWO) (Odysseus Return Grant G0F7716N, to V.P.), the KU Leuven Research Fund (BOFZAP starting grant StG/15/021BF to V.P. Cl grant C14/16/077 to V.P. and Project financing).