Fig. 4: Microglia activation increases Aβ plaque formation but reduces neuroprotection.

a sAβ42s were added to empty wells (scale bar = 20 μm) or b 12-week-old iPSC neurons at the indicated concentrations. All wells were stained with X04 (blue), Aβ (green), NFL-H (green), and p-Tau S235 (red). Empty wells have Aβ precipitates but no XO4 positive structure. In iPSC neuron wells, there is a dose-dependent increase of X04 staining. A Subset of XO4 is also surrounded by dystrophic neurites (NFL-H and S235 positive axonal swellings). Scale bar = 50 μm. c Microglia treated with sAβ42s ranging from 0 to 5 μM and also treated in combination with IFNγ. The panel below shows a zoomed-in section. Aβ plaques are stained with X04 (blue), microglia are labeled with Actin (green), and IBA1 (red). Scale bar = 50 μm. IFNγ increases plaque formation and plaque interaction. e Quantification of X04 intensity. f Quantification of IBA1 number. d Neuron and astrocytes coculture and triculture of neurons, astrocytes, and microglia were treated with sAβ42s with or without pro-inflammatory cytokine combination (IFNy + IL1b + LPS). Representative images from indicated conditions are shown. The lower panel of zoomed images is shown. Aβ plaque was stained with X04 (blue), dystrophic neurites swellings were stained with NFL-H (green), and microglia were labeled with IBA1 (red). In triple culture, sAβ42s addition led to Aβ plaque formations surrounded by dystrophic neurites and encircled by microglia similar to plaque presentation in vivo. Scale bar = 20 μm. g The area of IBA1 overlap with X04 is quantified. Pro-inflammatory cytokines increased microglia association with plaque. h Microglia increased the X04 plaque area, as measured by the total area of X04 staining. Pro-inflammatory cytokine addition increased the plaque area furthermore. MAP2 areas were also quantified in (i). sAβ42s addition caused a severe reduction to neuron culture. Microglia culture provided 25% MAP2 protection from sAβ42s. This protection is lost when pro-inflammatory cytokine is added. Data are presented as mean values +/− SEM and n = 4 wells. Two-way ANOVA with (e, f, h, i) Tukey’s or (g) Dunnett’s multiple comparisons test.