Inherently slow and weak forward forces of neuronal growth cones measured by a drift-stabilized atomic force microscope.

Previous results have shown that glial cells provide a soft environment for the neurons of the mammalian central nervous system (CNS). This raises the question whether neurons are confined to the CNS and cannot wander off into more rigid tissues, such as brain capillary walls. We investigated the mechanical properties and force generation of extending mouse retinal ganglion cells and NG108-15 growth cones (GCs) using different atomic force microscope (AFM)-based methods. For the first time, to our knowledge, we were able to measure the forward pushing forces at the leading edge of outgrowing neuronal GCs with our drift-stabilized AFM. Our results demonstrate that these GCs have neither the required stability nor the ability to produce forces necessary to penetrate tissues that are at least an order of magnitude stiffer.