Fig 2: BZA enhances remyelination after SCI. For a quantitative analysis of the formation of oligodendrocytes responsible for myelination, the spinal cord samples at dpi 20 were sectioned and immunostained. (A) Representative images of oligodendrocyte differentiation marker Olig2, the mature oligodendrocyte markers NG2, O4, CNPase, and the myelin marker MOG in the sham, injury, and BZA groups. (B–F) The percentage (%) of each antibody area to the total area of the immunofluorescence (IF) quantification graph. (B) Olig2, (C) NG2, (D) O4, © CNPase. (F) MOG. (G,H) Representative images of Luxol fast blue (LFB) staining at dpi 1 and dpi 20 in the sham, injury, and BZA groups. (I) Percentage graph of white matter that could be confirmed as myelin compared to the total area of sham, injury, and BZA groups at dpi 20, (J) A graph confirming the number of positive cells representing nerve cells at dpi 20. IF results of the graph confirmed the significance between the sham group and the injury and BZA groups. (LFB results = injury vs. sham, BZA). Data represents mean ± SEM (n = 3–4 (B,C), 3 (D), 5–6 (E), 3–6 (F), 4 (G–J)/group). * p < 0.05, ** p < 0.01, *** p < 0.001 (sham vs. injury, BZA; (A–F), injury vs. sham, BZA; (G–J). # p < 0.05 (injury vs. BZA; (A–F), NS = Not significant, one-way ANOVA followed by the Bonferroni test.

Fig 3: Physiological properties of excitable pre-OLs differ from those of OPCs. a Post-recording immunostaining of an Alexa 568-filled OPC (red) expressing NG2 (green) but not CNPase (blue). Scale bars, 10 µm. The same OPC displayed depolarizing spikes in response to current injections (60–140 pA, 300 ms) in current-clamp recordings. Inset, expanded time scale of the area within the dashed box. b An excitable pre-OL (P11) exhibiting distinct APs in response to current injections (60–140 pA, 300 ms). Inset, expanded time scale of the area within the dashed box. c I–V relationship of Iinward in an OPC (blue) and a pre-OL (black) and comparison of passive properties (capacitance and input resistance). d Relationship between spike amplitude and amount of current injected in OPCs and pre-OLs. Data represent the mean±s.e.m. *P < 0.05, ***P < 0.0001

Fig 4: Knockdown of Nav1.2 channels in pre-OLs impacts the myelination. a Confocal images of immunostaining for MBP in the auditory brainstem following the viral injection of vectors encoding scrambled shRNA (upper) and shRNA2 for Nav1.2 (lower). Scale bar, 20 µm. b Summary of the fluorescence intensity of MBP (red), which was measured in a 50 µm × 50 µm area surrounding CNPase-GFP+ cells within (white box). c Representative western blots probed for MBP and ß-actin levels from three individual brainstem samples in each groups injected with scrambled shRNA (upper) and shRNA2. d Summary of normalized MBP levels. Detected western blot intensities for MBP were normalized to corresponding ß-actin band intensities. All data represent the mean ± s.e.m.; *P < 0.05, **P < 0.01

Fig 5: An in vitro model to study the effects of TBI in the presence of Aß pathology. (A) Schematic outline of the experimental set-up. Differentiated cell cultures (astrocytes (green), neurons (gold) and oligodendrocytes (cyan); represented according to observation) were exposed to 0.1 µM Aß42 protofibrils for 24 h. The cells were then rinsed extensively before being subjected to experimental TBI, a mechanically induced scratch injury performed with a scalpel. Subsequently, the cells were cultured for three additional days. (A') Depiction of the four groups used in this study: untreated (control), scratch injured (TBI), exposed to Aß42 protofibrils (PF) and the combination of both (TBI + PF). (B) Representative image of the co-culture exposed to Aß42 protofibrils and stained for astrocytes (GFAP) and Aß. (B') A higher magnification of the area outlined by the square in (B), showing a close-up of the Aß deposits (some of different sizes are pointed out by the arrow heads). Orthogonal projections were made along the lines depicted in the main image and show the Aß inclusion surrounded by GFAP. (C) Representative images of astrocytes (GFAP), neurons (ßIII tubulin) and oligodendrocytes (CNPase). The scalpel cuts left noticeable injuries, which are outlined by the dashed lines. The three cell types react differently to the injury. Astrocytes extend towards and along the cut and the arrow head draws attention to an astrocyte growing into the area of laceration. Neurons also grow towards and along, but do not breach, the site of injury. Oligodendrocytes avert the area of the cut, unless in its direct vicinity, but were not observed to grow across the injury site. (C') Magnification of the areas outlined in (C). Scale bars 20 µm (B,B',C') and 50 µm (C).