Spatial distribution affects the role of CSPGs in nerve regeneration via the actin filament-mediated pathway

CSPGs are components of the extracellular matrix in the nervous system, where they serve as cues for axon guidance during development. After a peripheral nerve injury, CSPGs switch roles and become axon inhibitors and become diffusely distributed at the injury site. To investigate whether the spatial distribution of CSPGs affects their role, we combined in vitro DRG cultures with CSPG stripe or coverage assays to simulate the effect of a patterned substrate or dispersive distribution of CSPGs on growing neurites. We observed neurite steering at linear CSPG interfaces and neurite inhibition when diffused CSPGs covered the distal but not the proximal segment of the neurite. The repellent and inhibitory effects of CSPGs on neurite outgrowth were associated with the disappearance of focal actin filaments on growth cones. The application of an actin polymerization inducer, jasplakinolide, allowed neurites to break through the CSPG boundary and grow on CSPG-coated surfaces. The results of our study collectively reveal a novel mechanism that explains how the spatial distribution of CSPGs determines whether they act as a cue for axon guidance or as an axon-inhibiting factor. Increasing our understanding of this issue may promote the development of novel therapeutic strategies that regulate the spatial distributions of CSPGs to use them as an axon guidance cue.