Laboratory Forum: Rat as an Animal Model for Male Erectile Function Evaluation in Sexual Medicine Research

Comprehensive analysis of biological landscape of oxidative stress-related genes in diabetic erectile dysfunction

Oxidative stress plays a pivotal role in the pathogenesis of diabetic erectile dysfunction, while specific mechanisms have not been illuminated. The study aims to reveal the genetic expression patterns of oxidative stress in diabetic erectile dysfunction. Transcriptome data of diabetic erectile dysfunction and oxidative stress-related genes (OSRGs) in the Gene Expression Omnibus database were downloaded and analyzed based on differential expression. Functional enrichment analyses were conducted to clarify the biological functions. A protein interaction framework was established, and significant gene profiles were validated in the cavernous endothelial cells, clinical patients, and rat models. A miRNA-OSRGs network was predicted and validated. The results were analyzed using Student's t-test. The analysis screened 203 differentially expressed OSRGs (p < 0.05), which had a close association with oxidoreductase activities, glutathione metabolism, and autophagy. A four-gene signature comprised of EPS8L2 (p = 0.044), GSTA3 (p = 0.015), LOX (p < 0.001) and MGST1 (p = 0.002) was well validated and regarded as the hub OSRGs. Compared with the control group, notable increases and decreases were observed in the expressions of GSTA3 (3.683 ± 0.636 vs. 0.416 ± 0.507) and LOX (2.104 ± 1.895 vs. 18.804 ± 2.751) in the validated diabetic erectile dysfunction group. The hub OSRGs-related miRNAs participated in smooth muscle cell proliferation. Besides, miR-125a-3p (p = 0.034) and miR-138-2-3p (p = 0.012) were validated as promising oxidative stress-related miRNA biomarkers. Our findings revealed the genetic alternations of oxidative stress in diabetic erectile dysfunction. These results will be instructive to explore the molecular landscape and the potential treatment for diabetic erectile dysfunction.

A review of experimental techniques for erectile function researches and development of medical technology using animal erectile dysfunction models in sexual and reproductive medicine

Background

Erectile dysfunction (ED) is one of the causes of male infertility and is a disease that requires treatment. The first‐line drugs for ED are phosphodiesterase 5 (PDE‐5) inhibitors, and further treatment options are currently limited. Medical technologies, such as genetic control and regenerative medicine, are developing rapidly. Research on erectile function is progressing rapidly, coupled with technological innovations in other areas.

Methods

A PubMed search using the keywords “animal (rat, mouse, rabbit, dog, and monkey)” and “erectile” was conducted, and all relevant peer‐reviewed English results were evaluated.

Main findings

The methods for evaluating erectile function include intracavernous pressure (ICP) measurements, isometric tension studies, and dynamic infusion cavernosometry. Papers also reported various disease model animals for the study of diabetes mellitus, cavernous nerve injury, and drug‐induced ED.

Conclusion

Basic research on ED treatment has progressed rapidly over the past 20 years. In particular, research on the mechanism of ED has been accelerated by the publication of a study on the evaluation of erectile function using ICP measurements in rats. In addition, molecular biological experimental methods such as polymerase chain reaction (PCR) and western blotting have become relatively easy to perform due to technological progress, thus advancing research development.

Effects of tadalafil on sexual behavior of male rats induced by chronic unpredictable mild stress

Background

Few studies have investigated psychogenic sexual dysfunction including psychogenic erectile dysfunction (pED); the effect of tadalafil on sexual behavior of male rats induced by chronic unpredictable mild stress (CUMS) remains unclear.

Aim

The aim was to explore the influence of CUMS on sexual behavior of male rats and the effects of tadalafil on that.

Methods

Adult male rats were divided into 3 groups, including the normal group without CUMS, the model group with 6 weeks' CUMS, and the tadalafil group with treatment of tadalafil during CUMS. CUMS consists of water deprivation, food deprivation, stroboscopic lightning, white noise, cage tilting, weeding packing, and housing 2 unfamiliar rats. The apomorphine test and vaginal smear test were conducted with the aim to screen out male rats with good erectile function and make preparation for the sexual behavior test, respectively.

Outcomes

At the end of the study period, the level of anhedonia and sexual function were evaluated by the sucrose preference test, sexual behavior test, and measurement of serum testosterone, dopamine, and 5-HT.

Results

Sucrose preference showed significant decrease in rats after CUMS. The intromission ratio and total intromission frequency decreased significantly, while the mount latency and ejaculation latency prolonged significantly in CUMS-induced rats when compared with normal rats. Meanwhile, the treatment of tadalafil reversed the level of anhedonia and sexual function in CUMS-induced rats. However, there were no statistical differences in the levels of serum testosterone, dopamine, and 5-HT among groups.

Clinical Implications

The study constructed an animal model that can provide clinical insights into the mechanism of psychogenic sexual dysfunction and supports the application of tadalafil in pED therapy.

Strengths and Limitations

We found that CUMS-induced rats exhibited anhedonia and poor sexual function that could be prevented by tadalafil administration. Future research needs to construct the standard of pED model and explore the mechanism of tadalafil on central nervous system.

Conclusion

Tadalafil could prevent the changes of depression and poor sexual function in rats induced by CUMS, and the method of CUMS and the sexual behavior test should be used in the future for pED modeling.

Effects of platelet-rich plasma glue placement at the prostatectomy site on erectile function restoration and cavernous nerve preservation in a nerve-sparing prostatectomy rat model

BACKGROUND

Despite the widespread use of nerve-sparing prostatectomy techniques, the incidence of post-operative erectile dysfunction (ED) remains high. Early intracavernous (IC) injection of platelet-rich plasma (PRP) after nerve crushing improves erectile function (EF) in rats by promoting cavernous nerve (CN) regeneration and preventing structural changes in the corpus cavernosum. However, the neuroprotective effects of the in situ application of PRP glue in rats after CN-sparing prostatectomy (CNSP) remain unclear.

AIM

This study aimed to investigate the effects of PRP glue treatment on EF and CN preservation in rats after CNSP.

METHODS

After prostatectomy, male Sprague-Dawley rats were treated with PRP glue, IC PRP injection, or their combination. The intracavernous pressure (ICP), mean arterial pressure (MAP), and CN preservation status in the rats were evaluated after 4 weeks. Results were corroborated using histology, immunofluorescence, and transmission electron microscopy.

RESULTS

The PRP glue-treated rats showed 100% CN preservation and significantly higher ICP responses (the ratio of maximum ICP to MAP (0.79 ± 0.09)) than the CNSP rats (the ratio of maximum ICP to MAP (0.33 ± 0.04)). PRP glue also significantly increased neurofilament-1 expression, indicating its positive effect on the CNs. Furthermore, this treatment significantly increased the expression of α-smooth muscle actin. Electron micrographs revealed that PRP glue preserved the myelinated axons and prevented atrophy of the corporal smooth muscle by maintaining the adherens junctions.

CONCLUSIONS

These results indicate that PRP glue is a potential solution for EF preservation by neuroprotection in patients with prostate cancer who are likely to undergo nerve-sparing radical prostatectomy.

Emerging structural and pathological analyses on the erectile organ, corpus cavernous containing sinusoids

Background

The corpus cavernosum (CC) containing sinusoids plays fundamental roles for erection. Analysis of pathological changes in the erectile system is studied by recent experimental systems. Various in vitro models utilizing genital mesenchymal-derived cells and explant culture systems are summarized.

Methods

3D reconstruction of section images of murine CC was created. Ectopic chondrogenesis in aged mouse CC was shown by a gene expression study revealing the prominent expression of Sox9. Various experimental strategies utilizing mesenchyme-derived primary cells and tissue explants are introduced.

Main Findings

Possible roles of Sox9 in chondrogenesis and its regulation by several signals are suggested. The unique character of genital mesenchyme is shown by various analyses of external genitalia (ExG) derived cells and explant cultures. Such strategies are also applied to the analysis of erectile contraction/relaxation responses to many signals and aging process.

Conclusion

Erectile dysfunction (ED) is one of the essential topics for the modern aged society. More comprehensive studies are necessary to reveal the nature of the erectile system by combining multiple cell culture strategies.

Influence of anticancer agents on sexual function: an in Vivo study based on the US FDA Adverse Event Reporting System

Background

Patients with cancer are treated with chemotherapeutics that cause adverse effects, including erectile dysfunction (ED).

Objectives

We investigated erectile function in rats after the administration of anticancer agents based on data retrieved through mining of the US Food and Drug Administration (FDA) Adverse Event Reporting System (AERS) database.

Materials and methods

The statistical signal strength for the association between anticancer drugs and ED was calculated using the reporting odds ratio (ROR). A drug–event combination was detected when the lower limit of the 95% confidence interval (CI) of the ROR exceeded 1.00. Rats were administered anticancer agents detected in the FDA AERS analysis. Erectile function was assessed using intracavernous pressure (ICP) and mean arterial pressure (MAP) analysis after electrical stimulation of the cavernous nerve. Statistical significance was determined using Welch's t‐test or two‐way ANOVA.

Results

Melphalan (L‐PAM; ROR = 4.72, 95% CI = 2.78–8.00), vincristine (VCR; ROR = 2.47, 95% CI = 1.54–3.97), docetaxel (DTX; ROR = 2.25, 95% CI = 1.28–3.95), methotrexate (MTX; ROR = 1.96, 95% CI = 1.39–2.75), and doxorubicin (DOX; ROR = 1.82, 95% CI = 1.07–3.19) enhanced ED risk. L‐PAM and MTX decreased the ICP/MAP ratio 1 week after administration. VCR and DOX decreased erectile function 4 weeks after administration. DTX decreased erectile function at all assessed time points.

Discussion and conclusion

Certain anticancer agents should be considered risk factors for ED.

Our results provide possible treatment strategies for maintaining erectile function in cancer survivors, including careful erectile function monitoring after treatment.

Prolonged isoflurane anesthesia-induced acidosis decreases penile intracavernous pressure in rats

BACKGROUND

Intracavernous pressure measurement following cavernous nerve electrostimulation has been extensively adopted for the evaluation of erectile function in animals. However, the effect of measurement time and acidosis during anesthesia is still lacking.

OBJECTIVE

To explore the effect of measurement time and acidosis during anesthesia.

MATERIALS AND METHODS

Fifty-six male Sprague-Dawley rats were used and anesthetized by a spontaneous inhalation of isoflurane. In the first step, rats were randomly divided into four groups: a control group and three time-delayed measurement groups (intracavernous pressure measurement beginning at 15, 30, and 45 min after cavernous nerve exposure). In the second step, rats were randomly divided into three groups: a control group and two time-delayed measurement groups. Two intravenous fluid support strategies were used in time-delayed measurement groups: a normal saline solution and an isotonic Na₂ CO₃ solution.

RESULTS

Isoflurane-anesthetized rats developed systemic acidosis that worsens with time during intracavernous pressure measurement, which results in a significant decrease in the maximum intracavernous pressure value, intracavernous pressure/mean arterial pressure ratio, and total intracavernous pressure measured. The Na₂ CO₃ infusion could effectively correct acidosis. The decrease in intracavernous pressure was related to the reduced nitric oxide synthase activity, decreased cyclic guanosine monophosphate concentration, and reactive oxygen species activation in rat penis under acidosis conditions.

DISCUSSION AND CONCLUSION

Prolonged isoflurane anesthesia-induced acidosis markedly depresses the erectile response to cavernous nerve electrostimulation in rats. In this situation, it is recommended to supplement with a Na₂ CO₃ infusion to maintain a normal acid-base balance.

Evaluation of effectiveness of antiandrogen treatments on cavernosal tissues in rats

In this study, we aimed to compare changes in cavernosal tissues in rats with antiandrogen treatment and orchiectomy. A total of 42 Wistar albino rats were divided into four groups. Group I, control group, Group II, LH-RH was given for 1 month, Group III-LH-RH + Bicalutamide was given for 1 month, and Group IV was defined as orchiectomy and followed up for 1 month. Measurements of intracavernosal pressure with different electrical stimuli and pathological findings of smooth muscle collagen in cavernosal tissues were examined. While the cavernosal pressure response in all the different electrical stimuli given in the control group and in all other groups was significantly lower than that in the other groups, it was statistically significant at 7.5 and 10 V (p = .005, p < 0001). According to the pathologic evaluation, the density of tissue collagen increased significantly in the other groups according to the control group. In groups 3 and 4, the density of 4+ collagen was found to be increased according to Groups 1 and 2. In the LH-RH alone group, it appears that there are no 4+ colloid density and less damage. According to these findings, the negative effect of LH-RH treatment on cavernosal tissues appears to be less.

Intracavernosal Pressure Recording to Evaluate Erectile Function in Rodents

Erectile dysfunction (ED) is defined as the inability to attain or keep an erection of the penis, and this has become a prevalent male sexual disorder. Rodents are employed by many studies to research the physiology/pathology of erectile function. Erectile function in rodents can be evaluated by measuring the intracavernosal pressure (ICP). In practice, ICP can be monitored following electrical stimulation of the cavernous nerves (CNs). The arterial pressure of the carotid artery (the mean arterial pressure) is used as the reference for ICP. Using ICP recording protocols, many key parameters of erectile function can be measured from the ICP response curve. The ICP measurement provides more information than the apomorphine-induced penile erection test, and is cheaper than telemetric monitoring of the corpus spongiosum penis, making this method the most popular one to evaluate erectile function. However, compared to the easily-performed APO-induced erectile function test, successful ICP recordings require attention to detail, practice, and adherence to the operation method. In this work, an introduction to ICP recording in rats is provided to complement the procedure efficiently.

Cavernous Nerve Stimulation and Recording of Intracavernous Pressure in a Rat

The stimulation of the cavernous nerve (CN) and measurement of intracavernous pressure (ICP) have been used extensively to test and evaluate therapies for erectile dysfunction. However, the methods used vary between laboratories, and pitfalls still exist. The goal of this study was to describe a surgical technique that would provide a reliable and reproducible model. By exposing the ischiocavernosus muscle at its point of insertion on the ischial tuberosity, the penile crus could be cannulated with minimal dissection and injury to the structures involved in erectile function. Repeated stimulation of the CN, without the need for lifting and drying, was achieved by using a 125 µm bipolar silver electrode and biocompatible silicon glue to isolate the electrode-nerve complex. This method prevents neuropraxia by reducing stretching and drying the nerve and provides complete isolation of the nerve, negating electrical leakage and preventing stimulation of alternative pathways.

Comparison of two cannulation methods for assessment of intracavernosal pressure in a rat model

Intracavernous pressure (ICP) measurement is a well-established technique for assessing the erectile function, which was performed by cannulating either crus or shaft of the penis. However, there are no studies concerning the experimental performance of the two cannulation sites yet. The aim of this study was to compare the measuring outcomes using two different cannulation sites. To validate the capacity of our study, both normal and the castration-induced erectile dysfunction rat models were conducted. Fifty adult male Sprague-Dawley rats were randomized equally into two groups: an intact group and a castration group. Five rats from each group firstly underwent different stimulation parameters to detect the optimal erectile responses. The residual rats in each group were further assigned into two subgroups (n = 10 per subgroup) according to two different cannulation sites (crus or shaft of the corpus cavernosum). The ICP values were compared between groups after different interventions. The optimal parameters for mean maximum ICP were recorded at 2.5V and a frequency of 15 Hz. The rats under the two different cannulation sites tended to show similar ICP values in both the intact and the castration groups. However, the success rate in monitoring ICP was significantly higher in the groups cannulating into the shaft of the penis compared to the crus (100% vs. 70%; P = 0.02). Our data suggested that the method of cannulation into the penile shaft could serve as a better alternative for the ICP measurement in rats.

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.

Testosterone replacement alters the cell size in visceral fat but not in subcutaneous fat in hypogonadal aged male rats as a late-onset hypogonadism animal model

Background

Patients with late-onset hypogonadism (LOH) benefit from testosterone replacement by improvement in the parameters of the metabolic syndrome, but fat cell morphology in these patients is still unclear. This study aims to determine the effect of testosterone replacement on the morphology of fat cells in subcutaneous and visceral adipose tissue and on erectile function in hypogonadal aged male rats as a model of LOH.

Methods

Ten male Sprague-Dawley rats aged 20–22 months were randomly allocated to two groups, ie, aged male controls (control group, n=5) and aged males treated with testosterone replacement therapy (TRT group, n=5). Testosterone enanthate 25 mg was injected subcutaneously every 2 weeks for 6 weeks. At 6 weeks, the intracavernous pressure (ICP) and mean arterial blood pressure (MAP) ratio was assessed. Visceral and subcutaneous adipose tissue specimens were collected and analyzed using Image-J software.

Results

Body weight at 2, 4, and 6 weeks after TRT was 800.0±35.4 g, 767.5±46.3 g, and 780±40.4 g, respectively (not statistically significant). The ICP/MAP ratio was 0.341±0.015 in the TRT group and 0.274±0.049 in the control group (not statistically significant). The median subcutaneous fat cell size was 4.85×10³ (range 0.85–12.53×10³) μm² in the control group and 4.93×10³ (range 6.42–19.7×10³) μm² in the TRT group (not statistically significant). In contrast, median visceral fat cell size was significantly smaller in the TRT group (4.93×10³ μm² [range 0.51–14.88×10³]) than in the control group (6.08×10³ μm² [0.77–19.97×10³]; P<0.001, Mann-Whitney U test).

Conclusion

This is the first study clearly indicating that TRT can decrease visceral fat cell size, which is a key modulator in the metabolic syndrome. However, a short course of TRT could not improve the ICP response in hypogonadal aged male rats. Further investigation is necessary to clarify the exact rationale of TRT on the visceral fat cell.

A study of the early changes of the level of calcitonin gene-related Peptide and histopathology of penises of rats with experimentally induced type I diabetes mellitus by streptozocin

Introduction

Diabetes mellitus (DM) is a multiorgan disease that leads to neurovascular complications that disturb the normal erectile function.

Aim

The aim of the current work was to study the early changes occurring in the level of calcitonin gene-related peptide (CGRP) and histopathological changes in penile tissues of uncontrolled diabetic rats.

Materials and Methods

This study was carried on 50 adult male Sprague-Dawley rats divided into two main groups: group I (control, n = 10) and group II (diabetic, n = 40). Type I DM was induced by a single intraperitoneal injection of streptozotocin (60 mg/kg). The tissue level of CGRP and histopathological examination of rat penises were assessed at 2, 4, 6, and 8 weeks after induction of DM.

Results

CGRP was higher in the diabetic group at 4, 6, and 8 weeks than in the control group. However, endothelial changes and decreased smooth muscles mass started only 2 weeks after induction of DM.

Conclusion

Deterioration of histopathological features of the uncontrolled diabetic rats corporeal tissues is time dependent. Furthermore, vascular changes seem to precede the neurological changes. El-Kamshoushi AAM, Abdallah WI, Helal SF, El Azhary NM, and Hassan EM. A study of the early changes of the level of calcitonin gene-related peptide and histopathology of penises of rats with experimentally induced type I diabetes mellitus by streptozocin. Sex Med 2013;1:21–29.

Metformin treatment improves erectile function in an angiotensin II model of erectile dysfunction

INTRODUCTION

Increased angiotensin II (AngII) levels cause hypertension, which is a major risk factor for erectile dysfunction (ED). Studies have demonstrated that increased AngII levels in penile tissue are associated with ED. A recent study showed that metformin treatment restored nitric oxide synthase (NOS) protein expression in penile tissue in obese rats; however, whether metformin treatment can be beneficial and restore erectile function in a model of ED has not yet been established.

AIM

The goal of this study was to test the hypothesis that AngII induces ED by means of increased corpus cavernosum contraction, and that metformin treatment will reverse ED in AngII-treated rats.

METHODS

Male Sprague-Dawley rats were implanted with mini-osmotic pumps containing saline or AngII (70 ng/minute, 28 days). Animals were then treated with metformin or vehicle during the last week of AngII infusion.

MAIN OUTCOME MEASURES

Intracavernosal pressure; corpus cavernosum contraction and relaxation; nNOS protein expression; extracellular signal-regulated kinase (ERK1/2), AMP-activated protein kinase (AMPK), and eNOS protein expression and phosphorylation.

RESULTS

AngII-induced ED was accompanied with an increase in corpus cavernosum contractility, decreased nitrergic relaxation, and increased ERK1/2 phosphorylation. Metformin treatment improved erectile function in the AngII-treated rats by reversing the increased contraction and decreased relaxation. Metformin treatment also resulted in an increase in eNOS phosphorylation at ser1177.

CONCLUSIONS

Metformin treatment increased eNOS phosphorylation and improved erectile function in AngII hypertensive rats by reestablishing normal cavernosal smooth muscle tone.

Erectile dysfunction precedes coronary artery endothelial dysfunction in rats fed a high-fat, high-sucrose, Western pattern diet

Introduction.  It is suggested that erectile dysfunction (ED) may be an early risk factor for cardiovascular disease. Aim.  The goal of this study was to determine whether development of ED precedes the onset of coronary artery endothelial dysfunction in response to a Western diet (WD), thereby establishing whether the WD differentially impacts the endothelium in a time-dependent manner. Additionally, a goal was to determine if diet-induced ED is reversible with intracavernosal sepiapterin treatment. Methods.  Male Sprague-Dawley rats were fed a WD for 4, 8, or 12 weeks, or a control diet for 8 weeks. Erectile function was evaluated by measuring the mean arterial pressure (MAP) and intracavernosal pressure (ICP) in response to electrical field stimulation of the cavernosal nerve near the major pelvic ganglion, in the absence and presence of sepiapterin. Coronary artery endothelial function was evaluated ex vivo with cumulative doses of acetylcholine (ACh) applied to segments of the left anterior descending coronary artery preconstricted with serotonin. Main Outcome Measures.  Erectile function was assessed as the ICP response to electrical field stimulation (EFS), normalized to MAP. Coronary artery endothelial function was assessed as the effective concentration producing 50% of a maximal response (EC50 ) of the ACh response. Results.  The ICP/MAP response to EFS was significantly attenuated following both 8 and 12 weeks of the WD compared with the control diet (P < 0.05). Sepiapterin treatment augmented the ICP/MAP response in all WD groups (P < 0.05). The coronary artery EC50 of the ACh response was not different from control following 4 or 8 weeks but was significantly elevated following 12 weeks of the WD (P < 0.01). Conclusions.  These data suggest that erectile function is reduced prior to coronary artery endothelial function in response to the WD. Improvement of erectile function with sepiapterin in WD rats indicates that nitric oxide synthase uncoupling is a key mechanism in diet-induced ED. La Favor JD, Anderson EJ, Hickner RC, and Wingard CJ. Erectile dysfunction precedes coronary artery endothelial dysfunction in rats fed a high-fat, high-sucrose, Western pattern diet. J Sex Med 2013;10:694-703.

Animal models of erectile dysfunction (ED): potential utility of non-human primates as a model of atherosclerosis-induced vascular ED

Erectile dysfunction (ED) is a prevalent medical condition affecting 18 million men and their sexual partners in the United States alone. In the majority of patients, ED is related to alterations in the flow of blood to or from the penis. Undeniably, significant progress has been made in understanding the multifactorial mechanisms that modulate erectile capacity and predispose one to ED, and this, in turn, has led to the availability of more effective treatment options. Nonetheless, all current therapies have untoward side effects, and moreover, there are still no satisfactory treatments for many patients with ED. Further enhancements in the treatment of ED would logically result from both early intervention and more detailed mechanistic insight into the characteristics of the disease process per se. This fact underscores the importance of improved understanding of the initiation, development and progression of ED. However, to do so requires longitudinal studies on animal models that more closely approximate the corresponding clinical features and time course of human disease. The goal of this report is twofold. First, to provide a brief general overview of the applicability of commonly used animal models for the study of ED. The second and primary goal is to highlight the scientific rationale for using non-human primates to evaluate the impact of atherosclerosis-induced vascular disease on the penile and systemic circulatory systems. This latter goal seems especially relevant in light of the recent literature documenting a link between ED and systemic vascular disease, a finding that has major implications in an aging US male population consuming a high fat diet.

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.

Design and application of a new rat-specific vacuum erectile device for penile rehabilitation research

INTRODUCTION

Radical prostatectomy has a potential negative impact on penile health. The vacuum erection device (VED) has been used to promote the recovery of penile function and to maintain penile length. However, there is skepticism in the urological community due to its elusive mechanisms in penile rehabilitation.

AIM

To design a rat-specific VED and assess its application and safety.

METHODS

Based on rat penile measurement and the principle of human VED, the rat-specific VED was designed, and the application for rats was evaluated.

MAIN OUTCOME MEASURES

The vacuum pressure of the rat-specific VED was measured. The VED application on rat penis and its side effects were studied.

RESULTS

The rat-specific VED is a safe and applicable device to study the mechanism of VED in penile rehabilitation.

CONCLUSIONS

The newly designed rat-specific VED is a good simulator of the human VED. The application of this device on bilateral cavernous nerve crush rat model will be used to study the mechanisms of the VED in the penile rehabilitation.

Nerve growth factor modulation of the cavernous nerve response to injury

INTRODUCTION

Surgical therapies for prostate cancer and other pelvic malignancies often result in neuronal damage and debilitating loss of sexual function due to cavernous nerve (CN) trauma. Advances in the neurobiology of growth factors have heightened clinical interest in the development of protective and regenerative neuromodulatory strategies targeting CN recovery following injury.

AIM

The aim of this review was to offer an examination of current and future nerve growth factor (NGF) modulation of the CN response to injury with a focus on brain-derived nerve growth factor (BDNF), growth differentiation factor-5 (GDF-5), and neurturin (NTN).

METHODS

Information for this presentation was derived from a current literature search using the National Library of Medicine PubMed Services producing publications relevant to this topic. Search terms included neuroprotection, nerve regeneration, NGFs, neurotrophic factors, BDNF, GDF-5, NTN, and CNs.

MAIN OUTCOME MEASURES

Basic science studies satisfying the search inclusion criteria were reviewed.

RESULTS

In this session, BDNF, atypical growth factors GDF-5 and NTN, and their potential influence upon CN recovery after injury are reviewed, as are the molecular pathways by which their influence is exerted.

CONCLUSIONS

Compromised CN function is a significant cause of erectile dysfunction development following prostatectomy and serves as the primary target for potential neuroprotective or regenerative strategies utilizing NGFs such as BDNF, GDF-5, and NTN, and/or targeted novel therapeutics modulating signaling pathways.

Experimental models of Peyronie's disease. Implications for new therapies

INTRODUCTION

Despite its high prevalence and impact on the quality of life of patients, and that it is an excellent model for the study of fibrotic processes, Peyronie's disease (PD) is an orphan disease in biomedical research. The development of animal and cell culture models has advanced substantially the understanding of its molecular and cellular pathology and the proposal of new therapies.

AIM

To review the literature pertaining to the use of these models for the study of PD.

METHODS

PubMed search conducted from the first report of an animal model for PD.

RESULTS

This model, based on the finding that transforming growth factor beta1 (TGF beta 1) is overexpressed in the PD plaque, consists on the injection of TGF beta 1 into the tunica albuginea of the rat. This leads to a PD-like plaque retaining many of the histological and biochemical features of human PD. Another rat model, based on the hypothesis that the PD plaque arises from trauma to the penis, causing fibrinogen extravasation that initiates as fibrin a fibrotic response, consists on injection of fibrin into the tunica. The cell culture model is based on the demonstration that myofibroblasts are abundant in the human PD plaque.

CONCLUSIONS

These models have: (i) clarified the role of microtrauma, myofibroblasts, and oxidative stress in plaque development; (ii) demonstrated that this tissue is under sustained turnover by fibrotic and antifibrotic mechanisms; (iii) showed the interplay of collagenolytic and fibrinolytic systems and their inhibitors; (iv) detected an endogenous antifibrotic process consisting of the expression of inducible nitric oxide synthase that counteracts oxidative stress, collagen synthesis, and myofibroblast generation; (v) characterized the antifibrotic effects of chronic treatment with phosphodiesterase type 5 (PDE5) inhibitors; (vi) discovered the cytogenetic instability of PD cells and alterations in their gene expression; and (vii) detected stem cells in the tunica albuginea with a potential role in fibrosis and ossification.