Fig. 4

Induction of axonal varicosities of cultured cortical neurons by uniaxial stretch in a nanowrinkled stretch device. A A fabricated cell loading device with four rectangular membranes. The inset shows the atomic force microscopic image of the nanowrinkled surface upon membrane deformation. B The top-view schematic of neurons growing on the top of stretchable surface. C The side-view schematic of cell loading under control (unstressed and left) and stressed (right) conditions. D A cultured cortical neuron expressing YFP (green) with its axon growing into stretchable membrane region. Axon uniaxial stretch diagram, right. E Axonal varicosities induced by 50% strain (right), but not by 25% strain (middle). YFP signals are inverted. F Varicosities formed in dendrites after being stretched twice with 50% strain. G Summary of the relationship between target linear strain and time. H Summary of axonal varicosity formation under different target strains. One-way ANOVA followed by Dunnett’s test: **, p < 0.01. Scale bars, 35 μm in D, F and 15 μm in E