In vivo Morphological Dynamics of Single Laser-Axotomized Corneal Nerve Fibers in Sarm1-Null Adult Mice

Axonal regeneration represents a pivotal aspect of the adult peripheral nervous system (PNS). When an injury occurs, peripheral axons are able to regenerate and reestablish connections with their original targets. Although several precision techniques for severing axons in various non-mammalian model organisms have allowed to study the dynamics of regeneration after injury, similar axonal injury models have yet to be fully developed in mammals. In this study, we introduced a novel experimental method for laser-induced axotomy of single corneal sensory subbasal nerve fibers. This method enables the in vivo monitoring and quantification of axonal degeneration and regeneration morphological dynamics in adult mice. Results revealed that the degeneration of the distal stump of the subbasal fiber was delayed in mice lacking the protein SARM1, which promotes degenerative process after injury. Meanwhile, the proximal stump maintained the regenerative dynamics of the subbasal fiber, but regeneration of its nerve terminals was impaired. The present study introduces a valuable model for the in vivo study of the morphological plasticity dynamics of peripheral axons after injury in genetically tractable adult mammals.