Morphology and nanomechanics of mice sensory neurons following peripheral nerve injury

Dorsal root ganglia (DRG) contain a variety of sensory neurons that transduce somatic stimuli. Following peripheral nerve injury, sensory neurons have to adapt to a new environment in order to successfully promote their axonal elongation (regenerative growth mode). Unsuccessful regeneration leads to post-traumatic neuropathies, such ataxia and pain-related behavior, which are often chronic and mostly resistant to current treatments. Therefore understanding the cellular and molecular mechanisms leading to improved neurite re-growth is a major step to propose new therapies for nerve repair. In this work, we use differential interference contrast microscopy (DIC), fluorescence microscopy and atomic force microscopy (AFM) to study the morphological and nanomechanical properties of mice DRG sensory neurons in regenerative growth mode. DIC results show that conditioned axotomy, induced by sciatic nerve injury, did not increase somatic size of adult lumbar sensory neurons but promoted the appearance of longer and larger neurites and growth cones. Our AFM data indicate that conditioned neurons are characterized by softer growth cones and cell bodies, compared to control neurons. As cell elasticity is related mainly to the intrinsic properties of the cell membrane and cytoskeleton structures such as microtubules and actin fibers, the increase of the cell membrane elasticity suggests a modification in the ratio and the inner framework of the main structural proteins. Furthermore, in order to evidence structural differences between conditioned and control somas and growth cones, we use immunocytochemistry to localize actin (anti-actin antibody) and neuronal microtubules (anti-βIII-tubulin).