Super-Resolved Fluorescence Imaging of Peripheral Nerve
Abstract Traditional histopathologic evaluation of peripheral nerve employs brightfield microscopy with diffraction limited resolution of ~ 250 nm. Though electron microscopy yields nanoscale resolution of the nervous system, it is resource-intensive and incompatible with life. Super-resolution microscopy (SRM) comprises a set of imaging techniques permitting unprecedented resolution of fluorescent objects using visible light. The advent of SRM has transformed biomedical science in establishing non-toxic means for investigation of nanoscale cellular structures. Herein, sciatic nerve sections from GFP-variant expressing mice, and regenerating human nerve from cross-facial autografts labelled with a myelin-specific fluorescent dye were imaged by super-resolution radial fluctuation microscopy, stimulated emission depletion microscopy, and structured illumination microscopy. Super-resolution imaging of axial cryosections of murine sciatic nerves demonstrated robust visualization of myelinated and unmyelinated axons. Super-resolution imaging of axial cryosections of human cross-facial nerve grafts demonstrated enhanced resolution of small-calibre thinly-myelinated regenerating motor axons. The utility of SRM in imaging of mammalian cranial and peripheral nerves is demonstrated. The increase in contrast and structural clarity achievable with super-resolution techniques enables visualization of unmyelinated axons, regenerating axons, cytoskeleton ultrastructure, and neuronal appendages using light microscopes.