Additional file 3: Figure S3. of The release and trans-synaptic transmission of Tau via exosomes

Projections of neurons cultured in microfluidic devices with short microgrooves (150 μm). The 1st order hippocampal neurons were seeded on the somal side (left) of the microfluidic chamber. Fourteen days later, the 2nd order hippocampal neurons were seeded on the neuritic side (right) and cultured for additional 10–11 days. Neurons were treated on the neuritic side (A) or somal side (C) with DiI for 2 to 3 h. The living cells were then imaged using fluorescence microscopy. Scale bar = 10 μm. When the 2nd order neurons on the neuritic side were treated with DiI (A, top right panel), cell bodies of the 1st order neurons whose neurites projected through microgrooves to the neuritic side were positive for DiI staining (arrowhead in A, top left panel), by contrast, cell bodies of neurons that do not project to the neuritic side were not positive for DiI staining (arrows in A, bottom left panel). When the 1st order neurons on the somal side were treated with DiI (C, top left panel), their processes that projected through microgrooves to the neuritic side were stained by DiI (C, top right panel). However, no cell bodies of the 2nd order neurons (arrows in C, bottom right) were positive for DiI staining, indicating that the 2nd order neurons do not project through microgrooves to the somal side. The result of A and C is illustrated by B and D resp.. The flow of the conditioned medium (indicated by arrow) prevents the diffusion of added Dil from treated side to the opposite side. (PNG 175 kb)