Figure 6

Scanning electron micrographs of neuron/astrocyte/microglia co-cultures. These co-cultures were preincubated with compound C16 at 210 nM or DMSO 1 h before treatment with 20 μM Aβ42 or distilled water for 72 h in a serum-free medium. As in figure 1, samples were examined in a JEOL JSM-840 electron microscope. Aβ42 strongly altered the axonal and dendritic network, compared to DMSO or 210 nM C16 conditions. Microglia are activated and display numerous spinous processes along cell bodies and cytoplasmic projections; some cells have undergone transformation into multipolar cells or cells with at least one thin process extending a distance greater than three times the cell body diameter, known as "process-bearing microglia". Some occasional short secondary branches were also observed. Insets showed different states of activated microglia in Aβ42-treated co-cultures. On the contrary, C16 prevented the activated state of microglia, which appear as smooth cells with few spines as in DMSO or C16 without Aβ42 treatment. While some neurons were dead compared to DMSO alone, the network of axons and dendrites is preserved and comparable to the network observed in DMSO or C16 conditions. Bars: 17 μm and 5 μm for DMSO and 15 μm and 6 μm for C16, 35 μm and 10 μm for DMSO + Aβ42, 14 μm and 6 μm for C16 + Aβ42, at low and high magnification, respectively. White arrows indicate microglia cells.