Laboratory Forum: Cavernous Nerve Injury Using Rodent Animal Models

Riluzole, a neuroprotective agent, preserves erectile function following bilateral cavernous nerve injury in male rats

Neurogenic erectile dysfunction is a highly prevalent complication in men undergoing radical prostatectomy. The underlying mechanisms remain incompletely defined and the effective therapy has been limited. This study aimed to evaluate the protective effect of riluzole and the role of PKC β and excitatory amino acid transporters (EAATs) mediating this effect in a rat model of bilateral cavernous injury (BCNI). A total of 48 male Sprague-Dawley rats were divided into sham, BCNI (at 7, 15 days post-injury) and BCNI treated with riluzole (8 mg/kg/day) groups. Erectile function was measured as maximum intracavernosal pressure (mICP)/mean arterial pressure (MAP) and total ICP/MAP. Changes in protein expressions of phospho (p)-PKC β IIser660 and EAATs were analysed in penis and major pelvic ganglion with western blotting. BCNI decreased erectile function at 7 and 15 days post-injury (mICP/MAP at 4 V: 0.45 ± 0.06 vs 0.84 ± 0.07; 0.34 ± 0.04 vs 0.77 ± 0.04 respectively; p < 0.001) whereas riluzole treatment (for 15 days) preserved erectile function (mICP/MAP at 4 V: 0.62 ± 0.03 vs 0.34 ± 0.04; p < 0.01). The decline in the expression of p-PKC β IIser660 was observed in penis at 7 and 15 days post-injury (p = 0.0003, p = 0.0033), which was prevented by riluzole treatment for 15 days (p = 0.0464). While expressions of EAAT-1 and EAAT-2 decreased in major pelvic ganglion following BCNI (p = 0.0428, p = 0.002), riluzole treatment for 15 days prevented the decrease only in EAAT-2 expression (p = 0.0456). Riluzole improved erectile function via possibly interacting with PKC β II and glutamatergic pathways, as a potential therapeutic candidate for erectile dysfunction.

Functional recovery of injured cavernous nerves achieved through endogenous nerve growth factor-containing bioactive fibrous membrane

Radical prostatectomy is a highly successful treatment for prostate cancer, among the most prevalent manifestations of the illness. Damage of the cavernous nerve (CN) during prostatectomy is the main cause of postoperative erectile dysfunction (ED). In this study, the capability of a personalized bioactive fibrous membrane to regenerate injured CN was investigated. The fibrous membrane bioactivity is conferred by the selectively bound nerve growth factor (NGF) present in the rat urine. In a rat model of bilateral CN crush, the implanted bioactive fibrous membrane induces CN regeneration and restoration of erectile function, showing a significantly increased number of smooth muscle cells and content of endothelial and neuronal nitric oxide synthases (eNOS; nNOS). In addition, the bioactive fibrous membrane promotes nerve regeneration by increasing the number of myelinated axons and nNOS-positive cells, therefore reversing the CN fibrosis found in untreated rats or rats treated with a bare fibrous membrane. Therefore, this personalized regenerative strategy could overcome the recognized drawbacks of currently available treatments for CN injuries. It may constitute an effective treatment for prostate cancer patients suffering from ED after being subject to radical prostatectomy. STATEMENT OF SIGNIFICANCE: The present work introduces a unique strategy to address post-surgical ED resulting from CN injury during pelvic surgery (e.g., radical prostatectomy, radical cystoprostatectomy, abdominoperineal resection). It comprises a bioactive and cell-free fibrous implant, customized to enhance CN recovery. Pre-clinical results in a rat model of bilateral CN crush demonstrated that the bioactive fibrous implant can effectively heal injured CN, and restore penile structure and function. This implant selectively binds NGF from patient fluids (i.e. urine) due to its functionalized surface and high surface area. Moreover, its local implantation reduces adverse side effects. This tailored regenerative approach has the potential to revolutionize the treatment of ED in prostate cancer patients following radical prostatectomy, overcoming current treatment limitations.

An animal model induced by bilateral cavernous nerve crushing mimics post-radical prostatectomy erectile dysfunction in old rats

AIM

Over the years, the cavernous nerve (CN) crushing injury rat model has been frequently used for studying post-radical prostatectomy erectile dysfunction (pRP-ED). However, models based on young and healthy rats reportedly exhibit spontaneous recovery of erectile function. Our investigation purpose was to evaluate bilateral CN crushing (BCNC) effects on erectile function besides penile corpus cavernosum pathology in young and old rats and verify whether the BCNC modeling in old rats is more suitable to mimic pRP-ED.

MATERIALS AND METHODS

Thirty young and old male Sprague-Dawley (SD) rats had been divided into three groups in a random manner: sham-operated group (Sham), CN-injured 2-week group (BCNC-2W), and CN-injured 8-week group (BCNC-8W). At 2 and 8 weeks postoperatively, mean arterial pressure (MAP) along with intracavernosal pressure (ICP) had been determined, respectively. Then, the penis was harvested for histopathological studies.

KEY FINDING

We found that young rats exhibited erectile function spontaneous recovery 8 weeks following BCNC, while old ones failed to recover erectile function. After BCNC, the abundance of nNOS-positive nerve and smooth muscle were reduced, whereas apoptotic levels and collagen I content increased. These pathological modifications gradually resumed over time in young rats, unlike in old rats.

SIGNIFICANCE

Our findings demonstrate that 18-month-old rats do not spontaneously regain erectile function at 8 weeks after BCNC. Therefore, CN-injury ED modeling in 18-month-old rats may be more suitable for studying pRP-ED.

Relaxin-2 Prevents Erectile Dysfunction by Cavernous Nerve, Endothelial and Histopathological Protection Effects in Rats with Bilateral Cavernous Nerve Injury

PURPOSE

Cavernous nerve injury induced erectile dysfunction (ED) is a refractory complication with high incidence in person under radical prostatectomy. Studies have shown that relaxin-2 (RLX-2) plays a vital role of endothelial protection, vasodilation, anti-fibrosis and neuroprotection in a variety of diseases. However, whether penile cavernous erection can benefit from RLX-2 remains unknown. The purpose of the experiment was to explore the effects of RLX-2 on ED in the rat suffering with bilateral cavernous nerve injury (BCNI).

MATERIALS AND METHODS

The rats were divided into three groups: Sham group was underwent sham operation, BCNI+RLX group or BCNI group was underwent bilateral cavernous nerve crush and then randomly treated with RLX-2 (0.4 mg/kg/d) or saline by continuous administration using a subcutaneously implanted micro pump for 4 weeks respectively. Then, erectile function was evaluated by electrical stimulation of cavernous nerves. Cavernous nerves and penile tissues and were collected for histological evaluation.

RESULTS

Erectile function of rats with BCNI was partially improved after RLX-2 treatment. The BCNI group had lower expression of relaxin family peptide receptor (RXFP) 1, p-AKT/AKT, p-eNOS/eNOS ratios than sham operation rats, but RLX-2 could partially reversed these changes. Histologically, the BCNI+RLX group had a significant effect on preservation of neurofilament, neuronal glial antigen 2 of penile tissue and nNOS of cavernous nerves when compared with BCNI group. RLX-2 could inhibited the lever of BCNI induced corporal fibrosis and apoptosis via regulating TGFβ1-Smad2/3-CTGF pathway and the expression of Bax/Bcl-2 ratio, caspase3.

CONCLUSIONS

RLX-2 could improve erectile function of BCNI rats by protecting cavernous nerve and endothelial function and suppressing corporal fibrosis and apoptosis via RXFP1 and AKT/eNOS pathway. Our findings may provide a promising treatment for refractory BCNI induced ED.

Rats, Neuregulins and Radical Prostatectomy: A Conceptual Overview

In the contemporary era of early detection, with mostly curative initial treatment for prostate cancer (PC), mortality rates have significantly diminished. In addition, mean age at initial PC diagnosis has decreased. Despite technical advancements, the probability of erectile function (EF) recovery post radical prostatectomy (RP) has not significantly changed throughout the last decade. Due to virtually unavoidable intraoperative cavernous nerve (CN) lesions and operations with younger patients, post-RP erectile dysfunction (ED) has now begun affecting these younger patients. To address this pervasive limitation, a plethora of CN lesion animal model investigations have analyzed the use of systemic/local treatments for EF recovery post-RP. Most promisingly, neuregulins (NRGs) have demonstrated neurotrophic effects in both neurodegenerative disease and peripheral nerve injury models. Recently, glial growth factor 2 (GGF2) has demonstrated far superior, dose-dependent, neuroprotective/restorative effects in the CN injury rat model, as compared to previous therapeutic counterparts. Although potentially impactful, these initial findings remain limited and under-investigated. In an effort to aid clinicians, our paper reviews post-RP ED pathogenesis and currently available therapeutic tools. To stimulate further experimentation, a standardized preparation protocol and in-depth analysis of applications for the CN injury rat model is provided. Lastly, we report on NRGs, such as GGF2, and their potentially revolutionary clinical applications, in hopes of identifying relevant future research directions.

An update on the current status and future prospects of erectile dysfunction following radical prostatectomy

BACKGROUND

Radical prostatectomy (RP) and radiation treatment are standard options for localized prostate cancer. Even though nerve-sparing techniques have been increasingly utilized in RP, erectile dysfunction (ED) due to neuropraxia remains a frequent complication. Erectile function recovery rates after RP remain unsatisfactory, and many men still suffer despite the availability of various therapies.

OBJECTIVE

This systematic review aims to summarize the current treatments for post-RP-ED, assess the underlying pathological mechanisms, and emphasize promising therapeutic strategies based on the evidence from basic research.

METHOD

Evaluation and review of articles on the relevant topic published between 2010 and 2021, which are indexed and listed in the PubMed database.

RESULTS

Phosphodiesterase type 5 inhibitors, intracavernosal and intraurethral injections, vacuum erection devices, pelvic muscle training, and surgical procedures are utilized for penile rehabilitation. Clinical trials evaluating the efficacy of erectogenic drugs in this setting are conflicting and far from being conclusive. The use of androgen deprivation therapy in certain scenarios after RP further exacerbates the already problematic situation and emphasizes the need for effective treatment strategies.

CONCLUSION

This article is a detailed overview focusing on the pathophysiology and mechanism of the nerve injury developed during RP and a compilation of various strategies to induce cavernous nerve regeneration to improve erectile function (EF). These strategies include stem cell therapy, gene therapy, growth factors, low-intensity extracorporeal shockwave therapy, immunophilins, and various pharmacological approaches that have induced improvements in EF in experimental models of cavernous nerve injury. Many of the mentioned strategies can improve EF following RP if transformed into clinically applicable safe, and effective techniques with reproducible outcomes.

Low-Intensity Electrostimulation Enhances Neuroregeneration and Improves Erectile Function in a Rat Model of Cavernous Nerve Injury

BACKGROUND

Neurogenic erectile dysfunction (ED) following radical prostatectomy (RP) is a frequent complication often leading to erectile tissue remodeling and permanent ED. Low-intensity electrostimulation (LIES) has been shown to enhance peripheral nerve regeneration, however, its application on cavernous nerves (CN) has never been investigated.

AIMS

To investigate whether LIES enhances CN regeneration, improves erectile function (EF) recovery, and prevents corpora cavernosal remodeling after CN injury, which is a principal factor for ED following RP.

METHODS

Adult male Sprague-Dawley rats were divided into Sham, Bilateral Cavernous Nerve Injury (BCNI), and BCNI + LIES (1V, 0.1ms, 12Hz, 1h/day). After 7days, EF was assessed (ICP measurement). Penes and CN were collected for molecular analyses of TGF-β1, Il-6, CRP, eNOS, ERK and AKT protein levels in corpus cavernosum (CC), and immunohistological analysis of DHE, total collagen and α-SMA in CC and S-100, Tub-III, DAPI, TUNEL, and nNOS in CN.

OUTCOMES

Effects of LIES on EF, erectile tissue remodeling and CN structure.

RESULTS

EF was decreased (P < .05) 7 days after BCNI and increased (P < .05) by LIES. Intracavernosal reactive oxygen species (DHE) was increased (P < .05) after BCNI and normalized by LIES. Protein expressions of TGF-β1, IL-6, and CRP were increased in the penis (P < .05) after BCNI and normalized by LIES. The α-SMA and/or total collagen ratio was decreased (P < .05) after BCNI in the penis and normalized by LIES. Protein expression ratio of p-ERK/ERK and p-AKT/AKT did not change after BCNI but increased (P < .05) in LIES group. Myelination and number of nNOS positive cells in the CN were decreased (P < .05) after BCNI and normalized by LIES. The number of apoptotic nerve cells within the dorsal penile nerve was increased (P < .05) after BCNI and decreased (P < .05) by LIES compared to the BCNI group. There were no differences in eNOS expression in the penis between study groups.

CLINICAL TRANSLATION

LIES may offer a potential new tool for penile rehabilitation and ED management following RP, potentially enhancing EF recovery and minimizing the side effects of this surgery.

STRENGTHS & LIMITATIONS

This study provides evidence of the protective effect of LIES on EF and tissue remodeling following CN injury; nevertheless, this study has been conducted on animals and the translation to humans remains to be demonstrated. Further research to identify the underlying mechanisms of action is required.

CONCLUSION

This study demonstrates that LIES of the CN after CN injury protects CN structure, enhances EF recovery, and prevents corpora cavernosal remodeling. Sturny M, Karakus S, Fraga-Silva R, et al. Low-Intensity Electrostimulation Enhances Neuroregeneration and Improves Erectile Function in a Rat Model of Cavernous Nerve Injury. J Sex Med 2022;19:686-696.

Acetyl-L-carnitine improves erectile function in bilateral cavernous nerve injury rats via promoting cavernous nerve regeneration

BACKGROUND

Neurogenic erectile dysfunction (NED) caused by cavernous nerve (CN) injury is a typical complication after pelvic surgery, which lacks efficient treatments. Acetyl-L-carnitine (ALCAR) has been proven to promote nerve repair.

OBJECTIVES

To investigate the effect and potential mechanism of ALCAR in the treatment of NED.

MATERIALS AND METHODS

Thirty-two rats were randomly divided into bilateral cavernous nerve injury (BCNI) group, BCNI + lower-dose ALCAR (50 mg/kg/day) group, BCNI + higher-dose (100 mg/kg/day) group and sham-operated group. Erectile function was assessed 14 days after daily intraperitoneal injection of ALCAR or placebo. The penile tissues were gathered for subsequent histological and molecular biological analysis. Rat Schwann cell (SC) line S16 was used to verify the mechanism of ALCAR in vitro.

RESULTS

We found that the erectile function of the rats in BCNI group was severely impaired, which was improved considerably in both BCNI+ALCAR-LD and BCNI+ALCAR-HD groups. Also, we observed decreased smooth muscle and increased collagen content in corpus cavernosum in BCNI group. The expressions of fibrosis markers TGF-β, CTGF, and Smad 2/3 were significantly up-regulated in the BCNI group. The above changes were alleviated after the administration of lower and higher-dose ALCAR. Meanwhile, the NO/cGMP pathway was promoted and the RhoA/ROCK pathway was inhibited in the corpus cavernosum of BCNI rats after ALCAR treatment, accompanied by increased nNOS and down-regulated Tyrosine Hydroxylase. In vitro, ALCAR promoted the migration and proliferation of SC, and increased the expression of Pmp22 and NGF. Further, rats treated with ALCAR had high expression of ATF3 and S100 in the distal nerve tissues of the CN extrusion site.

DISCUSSION AND CONCLUSION

ALCAR could promote nerve repair and regeneration, inhibit penile fibrosis and improve penile erection by promoting the proliferation and migration of SC and the secretion of NGF. Our study confirms that ALCAR may be a potential treatment strategy for NED. This article is protected by copyright. All rights reserved.

Erectile dysfunction resulting from pelvic surgery is associated with changes in cavernosal gene expression indicative of cavernous nerve injury

Pelvic surgery, even without direct cavernous nerve injury, carries a high risk of post-operative erectile dysfunction. The present studies were aimed at identifying molecular mechanisms by which pelvic surgery results in erectile dysfunction. As a model of pelvic surgery, male Sprague-Dawley rats underwent pelvic laparotomy, avoiding direct cavernous nerve injury. A second group of animals, serving as a model of direct cavernous nerve injury, underwent bilateral transection of the cavernous nerve. Cavernosometry demonstrated, that even in the absence of direct nerve injury, the pelvic surgery model exhibited significant erectile dysfunction 3 days post-operatively. Gene expression profiling also demonstrated that even in this animal model of nerve-sparing pelvic surgery, the profile of differentially expressed genes in cavernosal tissue was indicative of cavernous nerve injury. In addition, although 6 hr after surgery there were significant changes in circulating cytokine/chemokine levels, an inflammatory response in the major pelvic ganglion, cavernous nerve and cavernosal tissue was only observed 3 days post-surgery. Our results validate a rat model of pelvic surgery exhibiting erectile dysfunction and suggest systemic release of cytokines/chemokines following surgical trauma might mediate a pathological inflammatory response in tissues distal to the site of surgical trauma, indirectly resulting in cavernous nerve injury and erectile dysfunction.

Oxaliplatin, an Anticancer Agent, Causes Erectile Dysfunction in Rats due to Endothelial Dysfunction

BACKGROUND

Chemotherapeutics, one of the standard treatment options for cancer worldwide, have various adverse effects, including erectile dysfunction (ED).

AIM

To investigate erectile function in an animal model after administration of the anticancer agent oxaliplatin (L-OHP).

METHODS

Male Wistar/ST rats were divided into 2 groups: L-OHP rats (n = 21), which were intravenously administered L-OHP (4 mg/kg; twice a week for 4 weeks), and Control rats (n = 21), which were injected with the same volume of 5% glucose solution, using the same dosing schedule. At the end of the study period, erectile function was evaluated by measuring intracavernous pressure (ICP) and mean arterial pressure (MAP) after cavernous nerve stimulation (n = 9-10). Endothelial function was evaluated with an isometric tension study using corpus cavernosum strips (n = 11). Western blot analysis was used to assess neuronal nitric oxide (nNOS) and endothelial NO synthase (eNOS) protein levels (n = 7). Real-time quantitative polymerase chain reaction (qRT-PCR) was used to assess the expression of inflammation- and oxidative stress-related markers (nicotinamide adenine dinucleotide phosphate oxidase-1, p22^phox, interleukin [IL]-6, and nuclear factor-kappa B) (n = 6). Statistical significance was determined using the Student's t-test.

OUTCOMES

The L-OHP group had a significantly lower ICP:MAP ratio than the control group (P < .05). Compared to the Control group, the L-OHP group exhibited significantly lower responses to ACh and eNOS protein levels and significantly higher inflammatory biomarker levels.

CLINICAL TRANSLATION

The results based on this animal model indicate that use of the anticancer agent L-OHP should be considered as a risk factor for ED occurring via reduction of NO bioavailability in humans; our results provide possible treatment strategies for maintaining the erectile function of cancer survivors.

STRENGTHS AND LIMITATIONS

Our study showed that the anticancer agent L-OHP has the propensity to cause ED in rats. A major limitation of this study is the lack of an established cure for ED associated with L-OHP and the lack of clinical evidence.

CONCLUSIONS

L-OHP causes ED in rats via reduction of NO bioavailability caused by endothelial dysfunction. Kataoka T, Mori T, Suzuki J, et al. Oxaliplatin, an Anticancer Agent, Causes Erectile Dysfunction in Rats due to Endothelial Dysfunction. J Sex Med 2021;18:1337-1345.

European Society for Sexual Medicine Consensus Statement on the Use of the Cavernous Nerve Injury Rodent Model to Study Postradical Prostatectomy Erectile Dysfunction

INTRODUCTION

Rodent animal models are currently the most used in vivo model in translational studies looking into the pathophysiology of erectile dysfunction after nerve-sparing radical prostatectomy.

AIM

This European Society for Sexual Medicine (ESSM) statement aims to guide scientists toward utilization of the rodent model in an appropriate, timely, and proficient fashion.

METHODS

MEDLINE and EMBASE databases were searched for basic science studies, using a rodent animal model, looking into the consequence of pelvic nerve injury on erectile function.

MAIN OUTCOME MEASURES

The authors present a consensus on how to best perform experiments with this rodent model, the details of the technique, and highlight possible pitfalls.

RESULTS

Owing to the specific issue-basic science-Oxford 2011 Levels of Evidence criteria cannot be applied. However, ESSM statements on this topic will be provided in which we summarize the ESSM position on various aspects of the model such as the use of the Animal Research Reporting In Vivo Experiments guideline and the of common range parameter for nerve stimulation. We also highlighted the translational limits of the model.

CONCLUSION

The following statements were formulated as a suggestive guidance for scientists using the cavernous nerve injury model. With this, we hope to standardize and further improve the quality of research in this field. It must be noted that this model has its limitations. Weyne E, Ilg MM, Cakir OO, et al. European Society for Sexual Medicine Consensus Statement on the Use of the Cavernous Nerve Injury Rodent Model to Study Postradical Prostatectomy Erectile Dysfunction. Sex Med 2020;8:327-337.

Tissue clearing-based method for unobstructed three-dimensional imaging of mouse penis with subcellular resolution

Although mice are widely used to elucidate factors contributing to penile disorders and develop treatment options, quantification of tissue changes upon intervention is either limited to minuscule tissue volume (histology) or acquired with limited spatial resolution (MRI/CT). Thus, imaging method suitable for expeditious acquisition of the entire mouse penis with subcellular resolution is described that relies on both aqueous- (clear, unobstructed brain imaging cocktails and computational analysis) and solvent-based (fluorescence-preserving capability imaging of solvent-cleared organs) tissue optical clearing (TOC). The combined TOC approach allows to image mouse penis innervation and vasculature with unprecedented detail and, for the first time, reveals the three-dimensional structure of murine penis fibrocartilage.

Real-time, functional intra-operative localization of rat cavernous nerve network using near-infrared cyanine voltage-sensitive dye imaging

Despite current progress achieved in the surgical technique of radical prostatectomy, post-operative complications such as erectile dysfunction and urinary incontinence persist at high incidence rates. In this paper, we present a methodology for functional intra-operative localization of the cavernous nerve (CN) network for nerve-sparing radical prostatectomy using near-infrared cyanine voltage-sensitive dye (VSD) imaging, which visualizes membrane potential variations in the CN and its branches (CNB) in real time. As a proof-of-concept experiment, we demonstrate a functioning complex nerve network in response to electrical stimulation of the CN, which was clearly differentiated from surrounding tissues in an in vivo rat prostate model. Stimulation of an erection was confirmed by correlative intracavernosal pressure (ICP) monitoring. Within 10 minutes, we performed trans-fascial staining of the CN by direct VSD administration. Our findings suggest the applicability of VSD imaging for real-time, functional imaging guidance during nerve-sparing radical prostatectomy.

Exercise training causes a partial improvement through increasing testosterone and eNOS for erectile function in middle-aged rats

PURPOSE

Aging changes the balance of sex hormones and causes endothelial dysfunction in the penis, both of which are important determinants of erectile dysfunction (ED). The purpose of this study was to evaluate whether exercise training could protect against erectile dysfunction by increasing serum testosterone and penile eNOS levels in aging rats.

METHODS

A total of 14 young (2-month-old) and 14 middle-aged (18-month-old) Sprague Dawley rats were randomly assigned to either untrained control (young control, [YC], middle-aged control, [MC]) or endurance exercise-trained (young exercise, [YE], middle-aged exercise, [ME]) groups with seven rats per group. The exercise groups trained with treadmill running for 6 weeks. Body composition parameters (body weight, heart mass, liver mass, and testicular mass), serum sex hormone levels (testosterone, luteinizing hormone, follicle-stimulating hormone, and prolactin), endothelial function-related parameters in the penis (endothelial nitric oxide synthase [eNOS], CD31, alpha smooth muscle actin [α-SMA]), and maximal intracavernous pressure measure (ICP) and total ICP were analyzed in middle-aged rats.

RESULTS

The middle-aged groups showed increased body weight, as compared with the young groups, but exercise training attenuated the aging-induced increase in body weight. The middle-aged groups had lower testicular mass compared with the young groups, but exercise training attenuated aging-induced decreases in testicular mass. Exercise training increased serum testosterone levels in both the young and middle-aged groups. However, there were no changes in the levels of luteinizing hormone, follicle-stimulating hormone, and prolactin among the groups. MC group showed decreased protein levels of p-eNOS, as compared with the YC group. However, exercise training protected against aging-induced decrease in eNOS and p-eNOS protein levels in the penis. Interestingly, exercise training also increased protein levels of α-SMA and maximal ICP in the middle-aged group.

CONCLUSIONS

Exercise training has beneficial effects on erectile function in aged rats through increased testosterone production from the testis and strengthening of the cavernous endothelium with activation of eNOS. Therefore, exercise training may be a therapeutic modality for improving erectile dysfunction associated with aging.

Dipyridamole reduces penile apoptosis in a rat model of post-prostatectomy erectile dysfunction

Purpose:

Despite the nerve-sparing technique, many patients suffer from erectile dysfunction after radical prostatectomy (RP) due to cavernous nerve injury. The aim of this study was to evaluate dipyridamole as a potential treatment agent of post-radical prostatectomy erectile dysfunction.

Material and methods:

A total of 18 male Sprague-Dawley rats were randomized into three experimental Groups (SHAM+DMSO, BCNI+DMSO and BCNI+DIP). An animal model of bilateral cavernous nerve crush injury (BCNI) was established to mimic the partial nerve damage during nerve-sparing RP. After creating of BCNI, dimethyl sulphoxide (DMSO) was administered transperitoneally as a vehicle to SHAM+DMSO and BCNI+DMSO Groups. BCNI+DIP Group received dipyiridamole (10mg/kg/day) as a solution in DMSO for 15 days. Afterwards, rats were evaluated for in vivo erectile response to cavernous nerve stimulation. Penile tissues were also analyzed biochemically for transforming growth factor-β1 (TGF-β1) level. Penile corporal apoptosis was determined by TUNEL method.

Results:

Erectile response was decreased in rats with BCNI and there was no significant improvement with dipyridamole treatment. TGF-β1 levels were increased in rats with BCNI and decreased with dipyridamole treatment. Dipyridamole led to reduced penile apoptosis in rats with BCNI and there was no significant difference when compared to sham operated rats.

Conclusions:

Although fifteen-day dipyridamole treatment has failed to improve erectile function in rats with BCNI, the decline in both TGF-β1 levels and apoptotic indices with treatment may be helpful in protecting penile morphology after cavernous nerve injury.

The effect of cavernous nerve traction on erectile function in rats

We performed this study to evaluate the effect of cavernous nerve (CN) traction on erectile function in rats. Thirty-two 8- week-old Sprague–Dawley rats were divided into four groups: control, 1-minute CN traction, 2-minute CN traction, and 2-minute CN crush. CN traction was performed using a glass hook with a tensile force of 0.2 Newton. One month later, the mean arterial pressure (MAP) and intracavernosal pressure (ICP) in response to CN stimulation were measured to assess erectile function. The penis and major pelvic ganglion (MPG) were harvested to explore the expression of neuronal nitric oxide synthase (nNOS) and neurofilament, fibrosis and apoptosis. The ICP/MAP ratio was reduced in the 2-minute CN traction group compared with the control group (P < 0.05). The ICP/MAP ratio in the CN crush group was lower than in the other three groups (P < 0.05, for each). Expression of nNOS in both MPG and dorsal penile nerve was lower in the CN traction group than in the control group, but was higher than in the CN crush group (P < 0.05). Nerve fiber number in the dorsal penile nerve was reduced by 2-minute CN traction (P < 0.05). The ratios of collagen to smooth muscle content and the apoptosis were both increased the in 2-minute CN traction group compared with the control group (P < 0.05). The findings indicate that CN traction is an effective CN injury model and the injury it caused is relatively mild compared with the CN crush model.

Anti-inflammatory and anti-fibrotic effects of annexin1 on erectile function after cavernous nerve injury in rats

The aim of this study was to investigate the effect of the anti-inflammatory and anti-fibrotic actions of ANX1 on erectile function (EF). Forty-eight male Wistar rats were randomly distributed into four equal groups: one group (sham operation-control) and three groups (bilateral cavernous nerve (CN) crush injury). Crush injury groups were treated prior to injury with an intravascular injection of either ANX1 (50 or 100 μg kg^-1) or vehicle. EF was assessed by CN electrical stimulation at 2 and 7 days after CN injury with histomorphometric and immunohistochemical analysis. ANX1 demonstrated functional preservation as the increase in intracavernous pressure (ICP). A dose-response relationship regarding the effect on penile tissue was confirmed, and preservation of the penile dorsal nerves and anti-apoptotic effects in the corpus cavernosum (real P-value vs injured control). ANX1 treatment prevented collagen deposition and smooth muscle loss in the penis. ANX1 normalized the expression of vascular endothelial growth factor and decreased tumor necrosis factor-α in the lumen of the blood vessels of the organ. ANX1 proved effective in preserving EF in a rat model of neurogenic erectile dysfunction. ANX1 treatment before CN injury in rats improved erectile recovery, enhanced vascular regeneration and preserved the micro-architecture of the corpus cavernosum. The clinical availability of this compound merits application in penile rehabilitation studies following radical prostatectomy.

Animal models of erectile dysfunction

Erectile dysfunction (ED) is a prevalent male sexual dysfunction with profound adverse effects on the physical and the psychosocial health of men and, subsequently, on their partners. The expanded use of various types of rodent models has produced some advances in the study of ED, and neurophysiological studies using various animal models have provided important insights into human sexual dysfunction. At present, animal models play a key role in exploring and screening novel drugs designed to treat ED.

Pelvic nerve injury negatively impacts female genital blood flow and induces vaginal fibrosis-implications for human nerve-sparing radical hysterectomy

OBJECTIVE

This study sought to develop a novel animal model to study the impact of nerve-sparing radical hysterectomy (NSRH) on female genital blood flow.

DESIGN

In vivo animal study.

POPULATION

Thirty Sprague-Dawley female rats.

MATERIALS AND METHODS

Female rats underwent either unilateral pelvic nerve (PN) crush (PNC; n = 9), or crush of both the PNs and all efferent nerves in the pelvic plexus ('clock-nerve crush', CNC; n = 9). Under anaesthesia, we electrically stimulated the crushed PN at 3 and 10 days after crush while monitoring blood pressure and recording clitoral and vaginal blood flows by laser Doppler. Uninjured PNs were stimulated as an internal control. Twelve additional rats were assigned either to bilateral PNC or sham surgery, and genital tissues were processed 10 days after injury for in vitro analysis.

MAIN OUTCOME MEASURES

Genital blood flow, nNOS, eNOS, collagen I-III.

RESULTS

Stimulation of the crushed PN in both groups subjected to PNC and CNC induced significantly lower peak genital blood flow at 3 and 10 days (P < 0.05) compared to stimulation of the non-crushed control PN. The immunofluorescence and Western blot analyses revealed that all injured rats exhibited more vaginal collagen III and collagen I than rats did that ad undergone sham surgeries (P < 0.05). PCN reduced nNOS expression in both clitoral and vaginal tissue.

CONCLUSIONS

Based on our study it may be hypothesised that NSRH might cause reductions of genital blood flow and vaginal fibrosis due to neurapraxia of the pelvic nerve and reductions of nNOS nerve fibres in clitoral and distal vaginal tissue.

TWEETABLE ABSTRACT

Pelvic nerve neurapraxia during nerve-sparing radical hysterectomy could lead to sexual arousal dysfunction.

Involvement of Rho-Kinase/LIM Kinase/Cofilin Signaling Pathway in Corporal Fibrosis after Cavernous Nerve Injury in Male Rats

INTRODUCTION

The molecular mechanism of corporal fibrosis leading to erectile dysfunction (ED) following cavernous nerve (CN) injury is poorly understood.

AIM

To determine whether the LIMK2/cofilin pathway, the downstream effectors of ROCK1, was involved in ED and corporal fibrosis following bilateral CN injury in male rats.

METHODS

Forty-eight 10-week-old male Sprague-Dawley rats were equally divided into three groups: sham surgery (S); bilateral CN crush injury (I); and bilateral CN resection (R). Within each groups, two subgroups were analyzed at 1 and 4 weeks postoperatively.

MAIN OUTCOME MEASURES

Electrostimulation was performed to assess erectile function by the ratio of maximal intracavernous pressure to mean arterial pressure (ICP/MAP) and areas under the ICP curve to MAP (AUC/MAP). Penile tissue was processed for Masson's trichrome staining, Western blot (ROCK1, total LIMK2, phospho-LIMK2, total cofilin, phospho-cofilin), immunohistochemistry (alpha-SM actin [α-SMA]), and double immunofluorescent staining (ROCK1, phospho-LIMK2, vimentin).

RESULTS

At each time point, both I and R groups showed a significantly lower percent of ICP/MAP and AUC, and decreased SM cell/collagen ratio and expression of α-SMA than S group. Densitometry revealed a significantly higher expression of ROCK1 in I and R groups compared with S group at all time points. The LIMK2 phosphorylation in I and R groups significantly increased at 1 week, but not at 4 weeks. The cofilin phosphorylation in R group significantly increased to that in S group starting at 1 week, while that in I group was increased significantly at 4 weeks. The double immunofluorescent staining noted that coexpression of vimentin with ROCK1 or phospho-LIMK2 in I and R groups was significantly increased mainly in the subtunical area at 1 week but not at 4 weeks.

CONCLUSIONS

The ROCK1/LIMK2/cofilin pathway may be involved in ED related to corporal fibrosis, and it appears to be functional particularly in the early period after CN injury.

Landmarks in erectile function recovery after radical prostatectomy

The description of the nerve-sparing technique of radical prostatectomy by Walsh was one of the major breakthroughs in the surgical treatment of prostate cancer in the 20(th) century. However, despite this advance and consequent technological refinements to nerve-sparing surgery, a large proportion of men still suffer from erectile dysfunction (ED) as a complication of prostatectomy. A plethora of therapeutic approaches have been proposed to optimize erectile function recovery in these patients. Several preclinical and translational studies have shown benefits of therapies including PDE5 inhibitor (PDE5I) treatment, immunomodulation, neurotrophic factor administration, and regenerative techniques, such as stem cell therapy, in animal models. However, most of these approaches have either failed to translate to clinical use or have yet to be studied in human subjects. Penile rehabilitation with PDE5Is is currently the most commonly used clinical strategy, in spite of the absence of solid clinical evidence to support its use.

GGF2 is neuroprotective in a rat model of cavernous nerve injury-induced erectile dysfunction

INTRODUCTION

Erectile dysfunction is a major complication of radical prostatectomy, commonly associated with penile neuropathy. In animal models of peripheral nerve injury, glial growth factor-2 (GGF2), a member of the neuregulin family of growth factors, has neuroprotective and neurorestorative properties, but this potential has not been established after cavernous nerve (CN) injury.

AIMS

The effectiveness of GGF2 in preserving axonal integrity and recovering erectile function in a rat model of radical prostatectomy-associated CN injury.

METHODS

Adult male Sprague-Dawley rats underwent bilateral CN crush injury (BCNI) or sham surgery. Rats were administered GGF2 (0.5, 5, or 15 mg/kg) or vehicle subcutaneously 24 hour pre and 24-hour post-BCNI, and once weekly for 5 weeks. Erectile function was assessed in response to electrical stimulation of the CN. CN survival was assessed by fluorogold retrograde axonal tracing in major pelvic ganglia (MPG). Unmyelinated axons in the CNs were quantitated by electron microscopy.

MAIN OUTCOME MEASURES

Erectile function recovery, CN survival, and unmyelinated CN axon preservation in response to GGF2 treatment following BCNI.

RESULTS

Erectile function was decreased (P < 0.05) after BCNI, and it was improved (P < 0.05) by all doses of GGF2. The number of fluorogold-labeled cells in the MPG was reduced (P < 0.05) by BCNI and was increased (P < 0.05) by GGF2 (0.5 and 5 mg/kg). The percentage of denervated Schwann cells in the BCNI group was higher (P < 0.05) than that in the sham-treated group and was decreased (P < 0.05) in the GGF2-treated (5 mg/kg) BCNI group. In the BCNI + GGF2 (5 mg/kg) group, the unmyelinated fiber histogram demonstrated a rightward shift, indicating an increased number of unmyelinated axons per Schwann cell compared with the BCNI group.

CONCLUSIONS

GGF2 promotes erectile function recovery following CN injury in conjunction with preserving unmyelinated CN fibers. Our findings suggest the clinical opportunity to develop GGF2 as a neuroprotective therapy for radical prostatectomy.

Animal models of erectile dysfunction

Animal models have contributed to a great extent to understanding and advancement in the field of sexual medicine. Many current medical and surgical therapies in sexual medicine have been tried based on these animal models. Extensive literature search revealed that the compiled information is limited. In this review, we describe various experimental models of erectile dysfunction (ED) encompassing their procedures, variables of assessment, advantages and disadvantages. The search strategy consisted of review of PubMed based articles. We included original research work and certain review articles available in PubMed database. The search terms used were “ED and experimental models,” “ED and nervous stimulation,” “ED and cavernous nerve stimulation,” “ED and central stimulation,” “ED and diabetes mellitus,” “ED and ageing,” “ED and hypercholesteremia,” “ED and Peyronie's disease,” “radiation induced ED,” “telemetric recording,” “ED and mating test” and “ED and non-contact erection test.”

Novel therapeutic approach for neurogenic erectile dysfunction: effect of neurotrophic tyrosine kinase receptor type 1 monoclonal antibody

BACKGROUND

Erectile dysfunction (ED) is a major health issue in aged populations, and neurogenic ED is particularly difficult to treat. Novel therapeutic approaches are needed for treatment of neurogenic ED of peripheral origin.

OBJECTIVE

To investigate the therapeutic effects of a neurotrophic tyrosine kinase receptor type 1 monoclonal antibody (TrkA-mAb) on erectile function and sexual behavior in a rat model of cavernous nerve injury (CNI).

DESIGN, SETTING, AND PARTICIPANTS

In one experiment, 84 male rats were randomly assigned to seven groups. The groups underwent either CNI or sham surgery, subsequent injection into the major pelvic ganglion (IMPG) of phosphate-buffered saline (PBS), an immunoglobulin G (IgG) control, or TrkA-mAb, and then intracavernosal (IC) injection of either PBS or varying TrkA-mAb concentrations immediately after surgery and then 1 wk later. Erectile function was assessed and histologic/molecular analyses were performed at 6 wk after surgery. In a second experiment, 36 male rats were randomly divided into three groups. The groups underwent CNI or sham surgery and then IC injection of PBS, IgG, or TrkA-mAb immediately after surgery and for 5 wk thereafter. At 6 wk after surgery, the performance of the rats in sexual behavior tests was videotaped.

INTERVENTION

CNI or sham surgery; IMPG of PBS, IgG, or TrkA-mAb; IC injection of PBS or TrkA-mAb.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

The intracavernous pressure response to cavernous nerve electrostimulation was measured and midpenile cross-sections were histologically examined. Western blotting (WB) of cavernous tissue protein was performed. Rats were assessed for chasing, mounting, intromission, and ejaculation behaviors during sexual behavior tests. The data were analyzed using one-way analysis of variance followed by the Tukey-Kramer t test.

RESULTS AND LIMITATIONS

Recovery of erectile function of varying degrees was observed in the TrkA-mAb groups. TrkA-mAb treatment significantly suppressed tyrosine hydroxylase-positive nerve fibers in the corpus cavernosum and enhanced neuronal nitric oxide synthase-positive fibers in the dorsal nerve. The ratio of smooth muscle to collagen in the corpus cavernosum was significantly improved in TrkA-mAb treatment groups compared to PBS vehicle and IgG control groups. WB confirmed these biological changes. There was a nonsignificant increase in the average number of intromissions and ejaculations in the TrkA-mAb group. The study limitations include small sample size, variability in sexual behavior, lack of data on the neuromuscular mechanism involved, and lack of information of the role of neurotrophins or cytokines in regeneration.

CONCLUSIONS

TrkA-mAb successfully inhibits sympathetic nerve regeneration, leads to parasympathetic nerve regeneration, and has therapeutic effects on ED and sexual behavior disorder in a rat model of CNI.

PATIENT SUMMARY

This report provides strong evidence that a neurotrophic tyrosine kinase receptor type 1 monoclonal antibody (TrkA-mAb) inhibits sympathetic nerve regeneration, leads to parasympathetic nerve regeneration, and has therapeutic effects on erectile dysfunction and sexual behavior disorder in a rat model of cavernous nerve injury. The results raise the possibility that human patients with neurogenic erectile dysfunction may respond to TrkA-mAb in a manner that parallels the response seen in our rodent study.

Topically applied NO-releasing nanoparticles can increase intracorporal pressure and elicit spontaneous erections in a rat model of radical prostatectomy

INTRODUCTION

Patients undergoing radical prostatectomy (RP) suffer from erectile dysfunction (ED) refractory to phosphodiesterase 5 inhibitors, which act downstream of cavernous nerve (CN)-mediated release of nitric oxide (NO). Direct delivery of NO to the penis could potentially circumvent this limitation.

AIM

This study aimed to determine if topically applied NO-releasing nanoparticles (NO-NPs) could elicit erections in a rat model of RP through increased blood flow.

METHODS

Twenty-six Sprague Dawley rats underwent bilateral transection of the CN. One week later, NO-NPs were applied topically to the penile shaft in dimethylsulfoxide (DMSO) gel (10 animals) or coconut oil (6 animals). Control animals were treated with empty NPs. Erectile function was determined through the intracorporal pressure/blood pressure ratio (ICP/BP). The effect of the NO-NPs on blood flow was determined using a hamster dorsal window chamber.

MAIN OUTCOME MEASURES

Animals were investigated for spontaneous erections, onset and duration of erectile response, and basal ICP/BP ratio. Microcirculatory blood flow was determined through measurements of arteriolar and venular diameter and red blood cell velocity.

RESULTS

Eight of 10 animals treated with NO-NPs suspended in DMSO gel had significant increases in basal ICP/BP, and 6 out of these 10 animals demonstrated spontaneous erections of approximately 1 minute in duration. Time to onset of spontaneous erections ranged from 5 to 37 minutes, and they occurred for at least 45 minutes. Similar results were observed with NO-NPs applied in coconut oil. No erectile response was observed in control animal models treated with empty NPs. The hamster dorsal window chamber experiment demonstrated that NO-NPs applied as a suspension in coconut oil caused a significant increase in the microcirculatory blood flow, sustained over 90 minutes.

CONCLUSIONS

Topically applied NO-NPs induced spontaneous erections and increased basal ICP in an animal model of RP. These effects are most likely due to increased microcirculatory blood flow. These characteristics suggest that NO-NPs would be useful in penile rehabilitation of patients following RP.

Valproic acid prevents penile fibrosis and erectile dysfunction in cavernous nerve-injured rats

INTRODUCTION

Bilateral cavernous nerve injury (BCNI) causes profound penile changes such as apoptosis and fibrosis leading to erectile dysfunction (ED). Histone deacetylase (HDAC) has been implicated in chronic fibrotic diseases.

AIMS

This study will characterize the molecular changes in penile HDAC after BCNI and determine if HDAC inhibition can prevent BCNI-induced ED and penile fibrosis.

METHODS

Five groups of rats (8-10 weeks, n = 10/group) were utilized: (i) sham; (ii and iii) BCNI 14 and 30 days following injury; and (iv and v) BCNI treated with HDAC inhibitor valproic acid (VPA 250 mg/kg; 14 and 30 days). All groups underwent cavernous nerve stimulation (CNS) to determine intracavernosal pressure (ICP). Penile HDAC3, HDAC4, fibronectin, and transforming growth factor-β1 (TGF-β1) protein expression (Western blot) were assessed. Trichrome staining and the fractional area of fibrosis were determined in penes from each group. Cavernous smooth muscle content was assessed by immunofluorescence to alpha smooth muscle actin (α-SMA) antibodies.

MAIN OUTCOME MEASURES

We measured ICP; HDAC3, HDAC4, fibronectin, and TGF-β1 protein expression; penile fibrosis; penile α-SMA content.

RESULTS

There was a voltage-dependent decline (P < 0.05) in ICP to CNS 14 and 30 days after BCNI. Penile HDAC3, HDAC4, and fibronectin were significantly increased (P < 0.05) 14 days after BCNI. There was a slight increase in TGF-β1 protein expression after BCNI. Histological analysis showed increased (P < 0.05) corporal fibrosis after BCNI at both time points. VPA treatment decreased (P < 0.05) penile HDAC3, HDAC4, and fibronectin protein expression as well as corporal fibrosis. There was no change in penile α-SMA between all groups. Furthermore, VPA-treated BCNI rats had improved erectile responses to CNS (P < 0.05).

CONCLUSION

HDAC-induced pathological signaling in response to BCNI contributes to penile vascular dysfunction. Pharmacological inhibition of HDAC prevents penile fibrosis, normalizes fibronectin expression, and preserves erectile function. The HDAC pathway may represent a suitable target in preventing the progression of ED occurring post-radical prostatectomy.

Functional and molecular changes of the bladder in rats with crushing injury of nerve bundles from major pelvic ganglion to the bladder: role of RhoA/Rho kinase pathway

Voiding dysfunction is a common complication after radical pelvic surgery. To reduce this complication, nerve-sparing radical pelvic surgery was introduced. However, several patients experienced voiding difficulty despite nerve-sparing radical pelvic surgery. Thus, we investigated the functional and molecular changes of the bladder in rats, which demonstrated voiding dysfunction induced by nerve damage during nerve-sparing radical pelvic surgery. Male rats were used and assigned to normal, sham-operated, and bilateral crushing nerve bundles from major pelvic ganglion (MPG) to bladder group. After one, two, and four-week crushing injury, significantly decreased contractile response and increased connective tissue of the detrusor were observed and these results were reliable findings with voiding difficulty following nerve-sparing radical pelvic surgery. After crushing injury, significantly increased M2 muscarinic receptor expression was observed and this might be regarded as the compensatory response. However, M3 muscarinic receptor expression was not significantly changed. The expression of RhoA, ROCK-α, and ROCK-β was significantly increased after one, two, and four-week crushing injury. From these results, the down-regulation of RhoA/Rho kinase pathway might lead to the decreased bladder contractility after crushing injury of nerve bundles from MPG to the bladder despite of the compensated up-regulation of M2 muscarinic receptor.

Effect of mesenchymal stem cells associated to matrixen on the erectile function in the rat model with bilateral cavernous nerve crushing injury

OBJECTIVES

To evaluate the effect of mesenchymal stem cells (MSCs) and MSCs mixed with Matrixen as a cell carrier on the erectile dysfunction caused by bilateral cavernous nerve crushing injury.

MATERIALS AND METHODS

White male Sprague-Dawley rats were divided into 4 groups: sham-operated control group (n = 5), bilateral cavernous nerve crushing group (BCNC group, n = 10), BCNC administered with MSCs group (n = 10,1x106 in 20 µL), BCNC administered with Matrixen group (n = 10.1x106 in 20 µL), BCNC administered with MSCs/Matrixen group (n = 10.1x106 in 20 µL). After functional assessment at 4 weeks, major pelvic ganglion (MPG) and penile tissue were collected. Immunofluorescent staining of MPG was performed with PKH26 and Tuj1. Western blot analysis of endothelial nitric oxide synthase (eNOS) and neuronal nitric oxide synthase (nNOS) were done in corpus cavernosum.

RESULTS

ICP/MAP ratios of BCNC with MSCs and MSCs/Matrixen groups were significantly increased compared with BCNC and BCNC with Matrixen group. Moreover, ICP/MAP ratios of MSCs/Matrixen group were significantly increased compared with BCNC with MSCs group. In MPG, the more implantation of MSCs and increased expression of nerve cells were observed in MSCs/Matrixen group compared with BCNC with MSCs group. Significant increase expression of eNOS and nNOS was also noted in BCNC with MSCs/Matrixen group.

CONCLUSION

The erectile function was more preserved in MSCs/Matrixen group compared with the administration of MSCs alone in the rats with bilateral cavernous nerve crushing injury. Therefore, we consider that the use of transplant cell carrier such as Matrixen may help the implantation of MSCs and improve the therapeutic effect of MSCs.

Bladder outlet obstruction triggers neural plasticity in sensory pathways and contributes to impaired sensitivity in erectile dysfunction

Lower urinary tract symptoms (LUTS) and erectile dysfunction (ED) are common problems in aging males worldwide. The objective of this work was to evaluate the effects of bladder neck nerve damage induced by partial bladder outlet obstruction (PBOO) on sensory innervation of the corpus cavernosum (CC) and CC smooth muscle (CCSM) using a rat model of PBOO induced by a partial ligation of the bladder neck. Retrograde labeling technique was used to label dorsal root ganglion (DRG) neurons that innervate the urinary bladder and CC. Contractility and relaxation of the CCSM was studied in vitro, and expression of nitric oxide synthase (NOS) was evaluated by Western blotting. Concentration of the sensory neuropeptides substance P (SP) and calcitonin gene-related peptide was measured by ELISA. Partial obstruction of the bladder neck caused a significant hypertrophy of the urinary bladders (2.5-fold increase at 2 wk). Analysis of L6-S2 DRG sections determined that sensory ganglia received input from both the urinary bladder and CC with 5-7% of all neurons double labeled from both organs. The contractile responses of CC muscle strips to KCl and phenylephrine were decreased after PBOO, followed by a reduced relaxation response to nitroprusside. A significant decrease in neuronal NOS expression, but not in endothelial NOS or protein kinase G (PKG-1), was detected in the CCSM of the obstructed animals. Additionally, PBOO caused some impairment to sensory nerves as evidenced by a fivefold downregulation of SP in the CC (P ≤ 0.001). Our results provide evidence that PBOO leads to the impairment of bladder neck afferent innervation followed by a decrease in CCSM relaxation, downregulation of nNOS expression, and reduced content of sensory neuropeptides in the CC smooth muscle. These results suggest that nerve damage in PBOO may contribute to LUTS-ED comorbidity and trigger secondary changes in the contraction/relaxation mechanisms of CCSM.

Perioperative betamethasone treatment reduces signs of bladder dysfunction in a rat model for neurapraxia in female urogenital surgery

BACKGROUND

Information on autonomic neurapraxia in female urogenital surgery is scarce, and a model to study it is not available.

OBJECTIVE

To develop a model to study the impact of autonomic neurapraxia on bladder function in female rats, as well as to assess the effects of corticosteroid therapy on the recovery of bladder function in this model.

DESIGN, SETTING, AND PARTICIPANTS

Female Sprague-Dawley rats were subjected to bilateral pelvic nerve crush (PNC) and perioperatively treated with betamethasone or vehicle. Bladder function and morphology of bladder tissue were evaluated and compared with sham-operated rats.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Western blot, immunohistochemistry, organ bath experiments, and cystometry.

RESULTS AND LIMITATIONS

Sham-operated rats exhibited regular micturitions without nonvoiding contractions (NVCs). Crush of all nerve branches of the pelvic plexus or PNC resulted in overflow incontinence and/or NVCs. Betamethasone treatment improved recovery of regular micturitions (87.5% compared with 27% for vehicle; p<0.05), reduced lowest bladder pressure (8 ± 2 cm H(2)O compared with 21 ± 5 cm H(2)O for vehicle; p<0.05), and reduced the amplitude of NVCs but had no effect on NVC frequency in PNC rats. Compared with vehicle, betamethasone-treated PNC rats had less CD68 (a macrophage marker) in the pelvic plexus and bladder tissue. Isolated bladder from betamethasone-treated PNC rats exhibited better nerve-induced contractions, contained more cholinergic and sensory nerves, and expressed lower amounts of collagen III than bladder tissue from vehicle-treated rats.

CONCLUSIONS

PNC causes autonomic neurapraxia and functional and morphologic changes of isolated bladder tissue that can be recorded as bladder dysfunction during awake cystometry in female rats. Perioperative systemic betamethasone treatment reduced macrophage contents of the pelvic plexus and bladder, partially counteracted changes in the bladder tissue, and had protective effects on micturition function.

Neuronal nitric oxide signaling regulates erection recovery after cavernous nerve injury

PURPOSE

Nitric oxide is the major neuronal mediator of penile erection but its role in erectile function status after cavernous nerve injury is uncertain. We determined the function of neuronal nitric oxide signaling in the pathobiology of erectile function recovery after partial cavernous nerve injury using genetic and pharmacological mouse experimental paradigms.

MATERIALS AND METHODS

Erectile function was evaluated in 5 to 7 wild-type and neuronal nitric oxide synthase-α knockout mice per group 1, 3 and 7 days after unilateral crush or sham injury, at day 7 in wild-type mice treated with the nitric oxide synthase inhibitor L-NAME (l-nitro arginine methyl ester) (Sigma-Aldrich®) at baseline and for 6 days after unilateral crush injury. Apoptosis in the penis was evaluated by Western blot analysis of p-Akt-S473, 3-nitrotyrosine and caspase-3 after bilateral crush injury.

RESULTS

Intracavernous pressure was significantly decreased at 1, 3 and 7 days in wild-type mice but only at day 1 in knockout mice after unilateral crush injury compared with sham treatment values (p <0.05). L-NAME treated wild-type mice had improved erectile function compared with the vehicle treated group at day 7 after unilateral crush injury (p <0.05). In penes p-Akt-S473 was significantly decreased in vehicle treated (p <0.05) but not in L-NAME treated wild-type mice. In penes 3-nitrotyrosine was significantly decreased in L-NAME treated wild-type and vehicle treated knockout mice (p <0.05). Caspase-3 in penes was significantly increased in vehicle treated (p <0.05) but not in L-NAME treated wild-type mice and vehicle treated knockout mice.

CONCLUSIONS

Neuronal nitric oxide signaling regulates erectile function recovery early after partial cavernous nerve injury, exerting an inhibitory role via the induction of apoptotic change in penile tissue. Therapeutic strategies to improve erectile function recovery after radical prostatectomy may consider targeting pathogenic sites of nitric oxide neurobiology.

Multipotent stromal cell therapy for cavernous nerve injury-induced erectile dysfunction

INTRODUCTION

Erectile dysfunction (ED) following radical prostatectomy (RP) is a result of inadvertent damage to the cavernous nerves that run close to the prostate capsula. The mechanisms behind the development of post-RP ED are increasingly recognized and include cavernosal fibrosis and cavernosal smooth muscle apoptosis, resulting from cavernous nerve degeneration due to neuropraxia. In recent years, cell-based therapies have received increasing attention regarding their potential for recovery of erectile function following cavernous nerve injury (CNI). Multipotent stromal cells (MSCs) are an attractive cell source for this application based on their regenerative potential and their clinical applicability.

AIM

To review available evidence on the efficacy and mechanisms of action of MSC application for the treatment of ED, with an emphasis on ED following CNI.

METHODS

A nonsystematic review was conducted on the available English literature between 1966 and 2011 on the search engines SciVerse-sciencedirect, SciVerse-scopus, Google Scholar, and PubMed.

RESULTS

MSCs from both bone marrow and adipose tissue have shown beneficial effects in a variety of animal models for ED. While MSC application in chronic disease models such as diabetes, aging, and hyperlipidemia may result in cell engraftment and possibly MSC differentiation, this observation has not been made in the acute CNI rat model. In the latter setting, MSC effects seem to be established by cell recruitment toward the major pelvic ganglion and local paracrine interaction with the host neural tissue.

CONCLUSIONS

While the type of model may influence the mechanisms of action of this MSC-based therapy, MSCs generally display efficacy in various animal models for ED. Before translation to the clinic is established, various hurdles need to be overcome.

Increased expression of nestin in the major pelvic ganglion following cavernous nerve injury

In an effort to identify neuronal repair mechanisms of the major pelvic ganglion (MPG), we evaluated changes in the expression of nestin, an intermediate filament protein and neural stem cell marker following cavernous nerve crush injury (CNI). We utilized two groups of Sprague Dawley rats: (i) sham and (ii) bilateral CNI. Erectile responses to cavernous nerve stimulation (CNS) were determined at 48 h in a subset of rats. The MPG was isolated and removed at 48 h after CNI, and nestin immunolocalization, protein levels and RNA expression were evaluated. At 48 h, erectile responses to CNS in CNI rats were substantially reduced (P<0.05; ∼70% decrease in intracavernous pressure/mean arterial pressure) compared with sham surgery controls. This coincided with a dramatic 10-fold increase (P<0.05) in nestin messenger RNA expression and protein levels in the MPG of rats with CNI. Immunoflourescence microscopy demonstrated that nestin upregulation after CNI occurred within the ganglion cell bodies and nerve fibers of the MPG. In conclusion, CNI induces nestin in the MPG. These data suggest that nestin may be involved in the regenerative process of the cavernous nerve following crush injury.

FK506 neuroprotection after cavernous nerve injury is mediated by thioredoxin and glutathione redox systems

INTRODUCTION

Immunophilin ligands such as FK506 (FK) preserve erectile function (EF) following cavernous nerve injury (CNI), although the precise mechanisms are unclear. We examined whether the thioredoxin (Trx) and glutathione (GSH) redox systems mediate this effect after CNI.

AIM

To investigate the roles of Trx reductase 2 (TrxR2) and S-Nitrosoglutathione reductase (GSNOR) as antioxidative/nitrosative and antiapoptotic mediators of the neuroprotective effect of FK in the penis after CNI.

METHODS

Adult male rats, wild-type (WT) mice, and GSNOR deficient (GSNOR -/-) mice were divided into four groups: sham surgery (CN [cavernous nerves] exposure only) + vehicle; sham surgery + FK (5 mg/kg/day/rat or 2 mg/kg/day/mouse, for 2 days, subcutaneous); CNI + vehicle; and CNI + FK. At day 4 after injury, electrically stimulated changes in intracavernosal pressure (ICP) were measured. Penises were collected for Western blot analysis of TrxR2, GSNOR, and Bcl-2, and for immunolocalization of TrxR2 and GSNOR.

MAIN OUTCOME MEASURES

EF assessment represented by maximal ICP and total ICP in response to electrical stimulation. Evaluation of protein expression levels and distribution patterns of antioxidative/nitrosative and antiapoptotic factors in penile tissue.

RESULTS

EF decreased after CNI compared with sham surgery values in both rats (P < 0.01) and WT and GSNOR -/- mice (P < 0.05). FK treatment preserved EF after CNI compared with vehicle treatment in rats (P < 0.01) and WT mice (P < 0.05) but not in GSNOR -/- mice. In rats, GSNOR (P < 0.01) and Bcl-2 (P < 0.05) expressions were significantly decreased after CNI. FK treatment in CN-injured rats restored expression of GSNOR and upregulated TrxR2 (P < 0.001) and Bcl-2 (P < 0.001) expressions compared with vehicle treatment. Localizations of proteins in the penis were observed for TrxR2 (endothelium, smooth muscle) and for GSNOR (nerves, endothelium, smooth muscle).

CONCLUSIONS

The neuroprotective effect of FK in preserving EF after CNI involves antioxidative/nitrosative and antiapoptotic mechanisms mediated, to some extent, by Trx and GSH systems.

Combination of BAY 60-4552 and vardenafil exerts proerectile facilitator effects in rats with cavernous nerve injury: a proof of concept study for the treatment of phosphodiesterase type 5 inhibitor failure

BACKGROUND

Radical prostatectomy (RP) is frequently responsible for erectile dysfunction (ED). Post-RP patients often show a failure to respond to phosphodiesterase type 5 (PDE5) inhibitors.

OBJECTIVE

The acute effect of BAY 60-4552, the soluble guanylate cyclase (sGC) stimulator, and vardenafil were evaluated alone or in combination on erectile responses to electrical stimulation of the cavernous nerve (ES CN) in rats with cavernous nerve (CN) crush injury-induced ED.

DESIGN, SETTING, AND PARTICIPANTS

Male adult Sprague-Dawley rats underwent laparotomy (sham, n=10) or bilateral CN crush injury (n=56). After 3 wk of recovery, erectile function was evaluated under urethane anaesthesia following ES CN at different frequencies.

MEASUREMENTS

The acute effects of intravenous (IV) injection of vehicle, vardenafil 0.03 mg/kg, BAY 60-4552 0.03 mg/kg or 0.3 mg/kg, or a BAY 60-4552 0.03 mg/kg plus vardenafil 0.03 mg/kg combination were evaluated in CN-crushed rats.

RESULTS AND LIMITATIONS

Bilateral CN crush injury followed by a 3-wk recovery period decreased erectile responses to ES CN by about 50%. In CN-crushed rats, IV vardenafil 0.03 mg/kg and BAY 60-4552 (0.03 or 0.3 mg/kg) increased erectile responses to ES CN to the same extent: Δ intracavernosal pressure/mean arterial pressure (ICP/MAP) at 10 Hz ES CN was 21±1% after vehicle, 25±3% (p<0.001) after vardenafil, and 26±5% and 27±5% after BAY 60-4552 0.03 mg/kg (p<0.01) and 0.3 mg/kg (p<0.001), respectively. The combination of vardenafil with BAY 60-4552 in CN-crushed rats totally restored erectile responses to ES CN equivalent to sham rats (ΔICP/MAP at 10 Hz ES CN: 34±4% after BAY 60-4552/vardenafil combination vs 39±4% in sham rats; not significant).

CONCLUSIONS

The present study supports the concept that the combined administration of a sGC stimulator, BAY 60-4552, and vardenafil provides synergistic beneficial effects and might therefore salvage patients who experience treatment failures with PDE5 inhibitors after RP.

Basis for the use of localized hypothermia during radical pelvic surgery

Controlled tissue cooling, or hypothermia, has been used therapeutically for decades to mitigate the negative effects of traumatic, ischemic, and surgical insults. When applied systemically, moderate hypothermia can attenuate or prevent the extent of neurologic sequelae. Localized hypothermia, on the other hand, has the capacity to reduce tissue edema, suppress inflammation, and minimize the severity of peripheral nerve injury. Therapeutic hypothermia has been used in critical care, neurosurgery, ophthalmology, otolaryngology, cardiothoracic surgery and most recently in urology. Nerve injury during radical pelvic surgery can result in urinary incontinence or retention, impotence and bowel dysfunction. Localized hypothermia during radical prostatectomy has demonstrated improved recovery of urinary continence and erectile function, and similar benefits might be observed in other types of radical pelvic surgery.

Advances in the study of the peripheral nervous system for erection in animals and humans

Introduction

Since Walsh first emphasized the importance of preserving the neurovascular bundle n to protect the cavernous nerve during pelvic surgery, patients' sexual life quality has dramatically improved. Today, nerve-sparing radical prostatectomy is the established gold standard for organ-confined prostate cancer patients. Recent technical advances in functional assessment such as intraoperative electrical stimulation have unveiled new anatomical features and physiological roles. Basic research has advanced understanding of cavernous nerve function, while molecular biology has uncovered the crucial role of neuronal nitric oxide in mediating erection, and has led to new treatments such as phosphodiesterase type-5 inhibitors. A recent focus in cavernous nerve research concerns the nerve distribution external to the neurovascular bundle. The cavernous nerves in humans appear to be distributed more widely beneath the lateral pelvic fascia than in other animals, and electrical stimulation studies suggest possible involvement of these nerves in erection. These findings have prompted new surgical techniques such as the "veil of Aphrodite", or "intrafascial nerve-sparing" procedures.

Materials and Methods

These recent anatomical and physiological studies in humans and animals and their impact are reviewed in this article.

Conclusions

Further investigation should stimulate future advances in strategies to preserve erectile function in RP patients.

Future sexual medicine physiological treatment targets

INTRODUCTION

Sexual function in men and women incorporates physiologic processes and regulation of the central and peripheral nervous systems, the vascular system, and the endocrine system. There is need for state-of-the-art information as there is an evolving research understanding of the underlying molecular biological factors and mechanisms governing sexual physiologic functions.

AIM

To develop an evidence-based, state-of-the-art consensus report on the current knowledge of the major cellular and molecular targets of biologic systems responsible for sexual physiologic function.

METHODS

State-of-the-art knowledge representing the opinions of seven experts from four countries was developed in a consensus process over a 2-year period.

MAIN OUTCOME MEASURES

Expert opinion was based on the grading of evidence-based medical literature, widespread internal committee discussion, public presentation, and debate.

RESULTS

Scientific investigation in this field is needed to increase knowledge and foster development of the future line of treatments for all forms of biological-based sexual dysfunction. This article addresses the current knowledge of the major cellular and molecular targets of biological systems responsible for sexual physiologic function. Future treatment targets include growth factor therapy, gene therapy, stem and cell-based therapies, and regenerative medicine.

CONCLUSIONS

Scientific discovery is critically important for developing new and increasingly effective treatments in sexual medicine. Broad physiologic directions should be vigorously explored and considered for future management of sexual disorders.

Feasibility study of an intensity-modulated radiation model for the study of erectile dysfunction

INTRODUCTION

Preclinical studies of radiotherapy (RT) induced erectile dysfunction (ED) have been limited by radiation toxicity when using large fields.

AIM

To develop a protocol of rat prostate irradiation using techniques mimicking the current clinical standard of intensity modulated radiotherapy (IMRT).

MAIN OUTCOME MEASURES

Quality assurance (QA) testing of plan accuracy, animal health 9 weeks after RT, and intracavernosal pressure (ICP) measurement on cavernosal nerve stimulation.

METHODS

Computed tomography-based planning was used to develop a stereotactic radiosurgery (SRS) treatment plan for five young adult male Sprague-Dawley rats. Two treatment planning strategies were utilized to deliver 20 Gy in a single fraction: three-dimensional dynamic conformal arc and intensity-modulated arc (RapidArc). QA testing was performed for each plan type. Treatment was delivered using a NovalisTX (Varian Medical Systems) with high-definition multi-leaf collimators using on-board imaging prior to treatment. Each animal was evaluated for ED 2 months after treatment by nerve stimulation and ICP measurement.

RESULTS

The mean prostate volume and target volume (5 mm expansion of prostate) for the five animals was 0.36 and 0.66 cm3, respectively. Both conformal and RapidArc plans provided at least 95% coverage of the target volume, with rapid dose fall-off. QA plans demonstrated strong agreement between doses of calculated and delivered plans, although the conformal arc plan was more homogenous in treatment delivery. Treatment was well tolerated by the animals with no toxicity out to 9 weeks. Compared with control animals, significant reduction in ICP/mean arterial pressure, maximum ICP, and ICP area under the curve were noted.

CONCLUSION

Tightly conformal dynamic arc prostate irradiation is feasible and results in minimal toxicity and measurable changes in erectile function.