Regulation of Central Nervous System Myelination in Higher Brain Functions

Figure 2

Axonal activity-dependent and activity-independent regulation of myelination. (a) Prolonged social isolation of adult mice induces hypomyelination in the PFC. Electron micrographs of axons in the PFC, nucleus accumbens (NAc), and corpus callosum (CC) from control and isolated mice (modified from Liu et al. [47], with copyright permission for reusing the figure panels). (b) The fiber diameter is sufficient to initiate myelination in a neuron-free culture. To determine the minimum fiber diameter at which oligodendrocytes commence wrapping in our system, Lee et al. analyzed oligodendrocytes cultured on nanofibers ranging from 0.2 to 4.0 μm in diameter and quantified the total number of MBP⁺ segments normalized to the fiber distribution on each coverslip. The minimum fiber diameter threshold for oligodendrocyte myelination is approximately 0.4 μm, which is supported by immunostaining of cultures for MBP and DAPI in the presence of small-diameter (A, 0.2–0.4 μm) and large-diameter (B, 2.0–4.0 μm) fibers. Electron-spun polystyrene or poly-L-lactic acid (PLLA) nanofibers with diameters ranging from 0.2 μm to 4.0 μm were engineered (modified from [62] with copyright permission for reusing the figure panels). (c) OLs have the unique, intrinsic capability to generate compact membrane sheaths and physiological internode lengths on microfibers. Confocal stacks of rat primary cortical OLs or Schwann cells cultured 14 or 21 days, respectively, on 1-2 μm microfibers or neurons (green: MBP, blue: Hoechst, and purple: S-100) (modified from Bechler et al. [64], with copyright permission for reusing the figure panels). Scale bars: 0.5 μm in (a) and 40 μm in (b) and (c).

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