Elasticity Maps of Living Neurons Measured by Combined Fluorescence and Atomic Force Microscopy

TL;DR

This study combines atomic force microscopy and fluorescence microscopy to create high-resolution elasticity maps of live neurons, revealing how microtubule formation and cell type influence neuronal stiffness during growth.

Contribution

It introduces a novel method for systematic elasticity mapping of live neurons, linking microtubule dynamics to changes in cell stiffness with high spatial resolution.

Findings

Neuronal elasticity varies with cell type, from 0.1 to 8 kPa.

Microtubule formation causes reversible local stiffening during growth.

Substrate protein coating does not affect neuron elasticity.

Abstract

Detailed knowledge of mechanical parameters such as cell elasticity, stiffness of the growth substrate, or traction stresses generated during axonal extensions is essential for understanding the mechanisms that control neuronal growth. Here we combine Atomic Force Microscopy based force spectroscopy with Fluorescence Microscopy to produce systematic, high-resolution elasticity maps for three different types of live neuronal cells: cortical (embryonic rat), embryonic chick dorsal root ganglion, and P-19 (mouse embryonic carcinoma stem cells) neurons. We measure how the stiffness of neurons changes both during neurite outgrowth and upon disruption of microtubules of the cell. We find reversible local stiffening of the cell during growth, and show that the increase in local elastic modulus is primarily due to the formation of microtubules. We also report that cortical and P-19 neurons have similar elasticity maps, with elastic moduli in the range 0.1-2 kPa, with typical average values of 0.4 kPa (P-19) and 0.2 kPa (cortical). In contrast, DRG neurons are stiffer than P-19 and cortical cells, yielding elastic moduli in the range 0.1-8 kPa, with typical average values of 0.9 kPa. Finally, we report no measurable influence of substrate protein coating on cell body elasticity for the three types of neurons.