Fig. 4
oMG expressed microglia-characteristic cell surface markers and showed similar functional immune and phagocytic properties as adult MG. a Flow cytometric analyses of the expression pattern of microglial extracellular markers on CD11b+-gated oMG (oMG 1, 3, and 5) compared to adult MG derived from three separate brain regions from adult MG1.1. (eight organoids were pooled per donor (oMG 1, 3, and 5) after 52 days in culture). b Morphology of magnetic automated cell sorted CD11b+ oMG 1 and adult MG in bright field microscope after 1 week in culture. Scale bar 40 μm. c mRNA expression, determined by qRT-PCR, of pro-inflammatory cytokines IL6 and IL1B after 6 h stimulation with LPS was significantly higher in oMG compared to adult MG (Mann–Whitney test IL6 and IL1B: U = 0, n = 4, p = 0.03). LPS-stimulated response relative to control condition without LPS. (n = 4 experiments, eight organoids pooled per experiment; adult MG1.1) (*p < 0.05). d Anti-inflammatory response of oMG and adult MG was compared by qRT-PCR for expression of anti-inflammatory genes CD163 and MRC1 upon 72 h stimulation with dexamethasone. Dexamethasone-stimulated response relative to control condition without dexamethasone. (oMG, n = 3 separate experiments in which oMG were isolated from > 4 pooled cerebral organoids from iPSC 1 per experiment; adult MG, n = 4). e Phagocytosis capacity was tested oMG 1 and adult MG by performing a phagocytosis assay with iC3b-coated green-yellow fluorescent beads. Phagocytosis was analyzed by confocal microscopy. Maximum intensity projection and orthogonal views are depicted. One experiment per donor. Scale bars 40 μm. f Quantification of iC3b beads engulfment by oMG and adult MG after 0.5 and 1 h exposure to the beads. Three randomly selected view fields per condition were manually quantified (oMG 1, for 0.5 and 1 h; adult MG1.7, 1.8, and 1.9, for 0.5 and 1 h). IBA-1+ cells were categorized based on the number of inoculated beads as follows: 0 (type 1), 1–5 (type 2), 6–15 (type 3), or > 15 (type 4)
