The microtubule cytoskeleton as a novel target for cavernous nerve regeneration after prostatectomy

Abstract Radical prostatectomy (RP) is a commonly used treatment option for localized prostate cancer. Unfortunately, the procedure carries a high risk of erectile dysfunction (ED) which is highly detrimental to the post-surgical well-being of men. The main pathophysiological mechanism behind ED is damage to the cavernous nerves (CN); mechanisms that regenerate or repair CN injury following RP could alleviate or treat ED in these patients. The studies outlined in this proposal will pursue a novel approach to CN repair by harnessing the nerve regenerative powers of Fidgetin-like 2 (FL2), a newly discovered microtubule regulator. In vitro studies indicate that the depletion of FL2 strongly enhances axonal growth in primary cultures of rat peripheral nervous system neurons. Recent work by the investigators involved in this proposal have shown that targeted depletion of FL2 via topical application of FL2-siRNA encapsulated in nanoparticles (FL2-siRNA-np) promotes the closure and regeneration of cutaneous wounds in mouse models and improved erectile function outcomes in a rat model of RP when applied at the time of CN injury. Remarkably, in a CN transection model of RP, at two weeks post treatment with FL2-siRNA there is both improved erectile function outcomes and visible nerve regrowth. These observations lead us to the hypothesis to be tested in this proposal that ?following CN injury, depletion of FL2 activates mechanisms that promote cavernous nerve regeneration, leading to accelerated recovery of erectile function?. This hypothesis will be tested in two specific aims. In the first Specific Aim we will substantiate our preliminary results that depletion of FL2 improves recovery of erectile function following CN injury used as an animal model of RP. We will optimize formulation and treatment regimens for ED. FL2-siRNA will be applied at the site of CN injury both at the time, and one week following injury and recovery of erectile function determined by measuring the intracorporal pressure/blood pressure ratio (ICP/BP) developed after CN stimulation, at various time points after treatment. Following cavernosometry, we will perform pathology studies to provide evidence of CN regeneration and safety of the different formulations. In the second Specific Aim we will conduct experiments to elucidate the mechanism by which the depletion of FL2 promotes functional recovery after CN injury. We will determine the effects of FL2-siRNA on axon growth and regeneration in vitro. Using tissues of controls and FL2-siRNA treated animals we will perform extensive comparative histopathology and gene expression analyses on corporal tissue and from the site of injury of treated versus control rats at various time-points after CN injury. Overall, upon completion of this proposal we will have established the potential of FL2 as a novel target in repairing CN damage following RP, determined treatment regimens, formulation and safety considerations to optimize potential clinical translation and have gained insight into the mechanism of FL2 mediated CN repair.