Neuronal differentiation on anisotropic substrates and the influence ofnanotopographical noise on neurite contact guidance.

Cells are exposed to specific directional physical signals determined by the micro/nano-environment that in vivo coexist with some degree of topographical noise. Particularly in the nervous system, cell contact sensing of the extracellular environment plays a primary role in defining neurite initiation and final brain wiring. Here we study neuronal cell response to directional stimuli by exploiting nanogratings with controlled amount of random nanotopographical noise. The impact of noise on neurite guidance and focal adhesions (FAs) development is investigated in NGF-differentiating PC12 cells by confocal and TIRF microscopy. We show that the loss of neurite guidance is not linear with noise, but is a threshold effect, correlating with changes in FA maturation and spatial organization. Finally nocodazole, a drug that increases cell contractility, can improve neurite alignment by promoting aligned FA maturation. We argue that these results show new possibilities for successful implant strategies particularly in the context of nerve-regeneration devices