Oligodendrocytes support axonal transport and maintenance via exosome secretion
Fig 6
PLP- and CNP-null exosomes do not promote axonal transport under starvation stress.
(A) Illustration of experimental schedule. Hippocampal neurons were treated with sEVs and subjected to starvation stress by depletion of B27 supplement (nutrient deprivation) during the last 3 h before live imaging. All treatment conditions were identical regarding the presence of oligodendrocyte-derived soluble factors and differed in presence of sEVs. (B) Representative kymographs and corresponding time-lapse frames illustrating movement of BDNF-mCherry-positive vesicles generated from hippocampal neurons exposed to nutrient deprivation and treated with sEVs derived from wild-type (WT), CNP knockout (CNPko), and PLP knockout (PLPko) oligodendrocytes or primary astrocytes (Astro). Red arrowhead follows 1 distinct particle moving over time. Kymograph: horizontal scale bar = 5 μm, vertical scale bar = 10 s; fluorescent picture frames: scale bar = 5 μm. (C–E) Quantitative analysis of kymographs regarding total movement (C), velocity (D), and pausing time (E) of BDNF-mCherry-positive vesicles. Data from control, ND + 100K SN and ND + WT EVs are reproduced from Fig 2 as reference. Data are presented as median, boxes (25th percentile to 75th percentile), and whiskers (minimum to maximum showing all data points), n = 18 recorded neurons for control, n = 19 for ND + 100K SN (−sEVs); n = 21 for ND + WT sEVs, ND + PLPko sEVs, and ND + CNPko sEVs; and n = 9 for ND + astrocyte sEVs, with up to 50 vesicle trajectories analyzed per neuron, derived from 3 independent experiments. *p < 0.05, **p < 0.01, ***p < 0.001, Shapiro–Wilk normality test following Kruskal–Wallis test with Dunn’s multiple comparison test. Significance only indicated for wild-type versus mutant sEVs for reasons of clarity (see Fig 2 for wild-type significance). Underlying data can be found in S1 Data. 100K, 100,000g-centrifuged; Astro, astrocyte; CNP, 2′,3′-cyclic nucleotide 3′-phosphodiesterase; ND, nutrient deprivation; OL, oligodendroglial; pCN, primary cortical neuron; PLP, proteolipid protein; SN, supernatant; sEV, small extracellular vesicle; WT, wild-type.