Fig. 7

Secreted αSYN aggregates are transferred from astrocytes to microglia. Conditioned media experiments were performed to investigate if transfer of αSYN occurred from one cell type to another via secretion (a, b). Microglia that received conditioned medium from αSYN-exposed astrocytes contained high levels of αSYN, while astrocytes that received microglia medium had very little intracellular αSYN (c, d). To further study secretory spreading of αSYN aggregates between the two cell types, we performed experiments using a customized close-culture chamber, in which the astrocytes and microglia were cultured face-to-face, separated by a <1-mm space. In the chamber, either untreated microglia were co-cultured with αSYN-exposed astrocytes (e) or untreated astrocytes were co-cultured with αSYN-exposed microglia (f). Consistently with the conditioned media data, astrocytes were found to transfer a large proportion of their internalized αSYN to microglia (g), while microglia hardly transferred any αSYN to the astrocytes (h). Scale bars = 20μm