Fig. 5

Electrophysiology studies on DRG neurons in microfluidic devices stimulated with osteoclasts secretome vs. osteoclast-derived EV. A Phase-contrast microscopy image mosaic of an organotypic dorsal root ganglia (DRG) culture at 6 days in vitro (DIV). The whole microelectrode array (MEA) (1.5 × 1.5 mm) active area is shown by a combination of 9 mosaic images (10× objective) from different parts of the culture. A PDMS device composed of 16 microchannels (10 μm width; 700 μm length) is aligned to encompass 7 microelectrodes. Details of axonal morphology can be seen in the somal compartment, microchannels and axonal compartment (scale bar 200 μm). A schematized version of a microchannel is shown on the right. B Electrophysiological trace of 30 s of baseline activity from an electrode (within a microchannel) at 6 DIV and corresponding spike raster plot. Inset shows a single spike. C Representative activity maps (microchannel area only, electrode rows 9–15) of baseline and post-treatment (time 30 min) activity for each condition (NB—neurobasal; OC—osteoclasts secretome; EV+—osteoclast-derived EV). Each pixel corresponds to an electrode and the mean firing rate (MFR) is color-coded. Representative raster plots of 60 s of activity are shown below each activity map. Each row corresponds to the spike raster plot from the central electrode of a single microchannel. D Before-after plot of every active microchannel after treatment. ns = not significant, *0.01 < p < 0.05, **0.001 < p < 0.01, ***p < 0.001, ****p < 0.0001. E Scatter dot plots of the active microchannels’ MFR at 30 min post-treatment (OC—osteoclasts secretome; EV+—osteoclast-derived EV). Data from 35 to 61 microchannels from 3 to 5 independent μEFs