The microtubule (MT) cytoskeleton plays a critical role in axon growth and guidance. Here, we identify the MT severing enzyme fidgetin-like 2 (FL2) as a negative regulator of axonal regeneration and a potential therapeutic target for promoting neural regeneration after injury. Genetic knockout of FL2 in cultured adult dorsal root ganglion (DRG) neurons resulted in longer axons and attenuated growth cone retraction in response to inhibitory molecules. Given the axonal growth-promoting effects of FL2 depletion in vitro, we tested whether the enzyme could be targeted to promote regeneration in a rodent model of peripheral nerve injury. In the model used in our experiments, the cavernous nerves (CN) are either crushed or transected, mimicking nerve injury caused by radical prostatectomy (RP). As with patients, CN injury results in erectile dysfunction, for which there are presently poor treatment options. At the time of injury, FL2-siRNA or control-siRNA was applied to the site using nanoparticles or chondroitin sulfate microgels as delivery agents. Treatment significantly enhanced functional nerve recovery, as determined by cavernosometry (measurements of corporal blood pressure in response to electrostimulation of the nerve). Remarkably, following complete bilateral nerve transection, visible and functional nerve regeneration was observed in 7 out of 8 animals treated with FL2-siRNA. In contrast, no control-siRNA treated animals showed regeneration. These observations suggest a novel therapeutic approach to treat peripheral nerve injury, particularly injuries resulting from surgical procedures such as RP, where treatments depleting FL2 could be applied locally at the time of injury.

Fidgetin-like 2 is a novel negative regulator of axonal growth and can be targeted to promote functional nerve regeneration after injury.