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-ß1, 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-ß1, 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.

TSPO ligand FGIN-1-27 controls priapism in sickle cell mice via endogenous testosterone production.

Priapism, a prolonged penile erection in the absence of sexual arousal, is common among patients with sickle cell disease (SCD). Hypogonadism is also common in patients with SCD. While the administration of exogenous testosterone reverses hypogonadism, it is contraceptive. We hypothesized that the stimulation of endogenous testosterone production decreases priapism by normalizing molecular signaling involved in penile erection without decreasing intratesticular testosterone production, which would affect fertility. Treatment of SCD mice with FGIN-1-27, a ligand for translocator protein (TSPO) that mobilizes cholesterol to the inner mitochondrial membrane, resulted in eugonadal levels of serum testosterone without decreasing intratesticular testosterone production. Normalized testosterone levels, in turn, decreased priapism. At the molecular level, TSPO restored phosphodiesterase 5 activity and decreased NADPH oxidase-mediated oxidative stress in the penis, which are major molecular signaling molecules involved in penile erection and are dysregulated in SCD. These results indicate that pharmacologic activation of TSPO could be a novel, targetable pathway for treating hypogonadal men, particularly patients with SCD, without adverse effects on fertility.

Apelin-13 Protects Corpus Cavernosum Against Fibrosis Induced by High-Fat Diet in an MMP-Dependent Mechanism.

BACKGROUND: An increased fibrosis of the corpora cavernosa is a prevalent process that underlies most cases of erectile dysfunction. Apelin, an endogenous circulating peptide, has been documented as an important effector on cardiovascular homeostasis, controlling vascular function and reducing fibrosis in multiple pathological conditions. Recently, initial studies have shown that Apelin, acting through the APJ receptor, also modulates penile erection, however, the role of this system on penile structure and intracorporal collagen remodeling has not been investigated yet. AIMS: Here we sought to investigate the effect of chronic Apelin treatment on the corpus cavernosum structure of hyperchOlesterolemic mice. METHODS: Apolipoprotein gene-deleted (ApoE-/-) mice were fed with a Western diet for 11 weeks and received Apelin-13 (2 mg/kg/day) or vehicle during the last 3 weeks. Penile samples were obtained for histological and biochemical analyses to assess the intracorporal collagen content and key proteins expression. Furthermore, the effect of Apelin-13 was evaluated in cultured NIH3T3 mouse fibroblasts stimulated with TGF-ß. OUTCOME: Local expression of Apelin-13 in mouse corpus cavernosum and its protective effect against fibrosis. RESULTS: Apelin and APJ receptor were expressed (gene and protein) within the corpus cavernosum of ApoE-/- mice, indicating a local modulation of the Apelin system. Interestingly, 3 weeks of Apelin-13 treatment strongly reduced intracavernosal collagen content. In addition, Apelin-13 enhanced total matrix metalloproteinase (MMP) activity in the mice penis, which was associated with an increased protein expression of MMP-1, MMP-3, MMP-8, and MMP-9, while tissue inhibitor of metalloproteinase were unaltered. These beneficial actions were not associated with changes in nNOS or eNOS protein expression, intracavernosal reactive oxygen species content, or atherosclerotic plaque deposition. Additionally, in cultured fibroblast, Apelin-13 inhibited TGF-ß-induced fibroblast to myofibroblast differentiation and collagen production, possibly through the activation of ERK1/2 kinase. CLINICAL TRANSLATION: These results point out Apelin/APJ system as a potential target to treat intracavernosal fibrosis-related disorders. STRENGTH & LIMITATIONS: These results provide the first evidence of the Apelin system's positive role on erectile tissue structure/remodeling. Nevertheless, additional functional study addressing erectile response would bring extended validation regarding the relevance of such effect. CONCLUSION: These results suggest a local modulation of the Apelin system within the corpus cavernosum. Remarkably, Apelin-13 reduced intracavernosal fibrosis in hypercholesterolemic mice by: (i) enhancing MMPs expression and activity; and (ii) inhibiting fibroblast differentiation into myofibroblast. Altogether, these results suggest an essential protective role of Apelin, indicating Apelin/APJ system as a promising candidate for the development of fibrosis-associated erectile dysfunction treatments. Sturny M, Anguenot L Costa-Fraga FP, et al. Apelin-13 Protects Corpus Cavernosum Against Fibrosis Induced by High-Fat Diet in an MMP-Dependent Mechanism. J Sex Med 2021;18:875-888.

Characterization of the Renin-Angiotensin System in Aged Cavernosal Tissue and its Role in Penile Fibrosis.

BACKGROUND: The renin-angiotensin system (RAS) plays an important role in erectile function. The RAS contains 2 major axes: one deleterious, composed of ACE-Ang II-AT1 receptor, and another protective, composed of ACE2-Ang-(1-7)-Mas receptor. While aging is a well-known cause for development of male sexual disorders, little is known about local regulation of the RAS in age-related erectile dysfunction (ED). AIM: The present study aimed to assess regulation of the RAS in aging-associated ED rat model and evaluate possible options for disease management through pharmacological modulation of the RAS. METHODS: Penile tissues were harvested from 3-, 12-, and 24-month-old Wistar rats. Local expression of major RAS components and ED markers was measured by RT-PCR. Protein expression of RAS components was assessed by western blot. Collagen deposition was measured by Sirius Red and immunohistochemical staining. Evaluation of collagen content was also performed in penile sections of Mas-knockout mice by Sirius Red and Masson's trichrome stainings. Finally, the effect of Ang-(1-7) pretreatment on TGF-ß-induced myofibroblast activation was studied in primary cavernosal and immortalized fibroblasts. OUTCOMES: Experimental results highlighted the essential role of the RAS in modulation of cavernosal fibrosis. RESULTS: The present study demonstrates local expression of angiotensinogen mRNA alongside with major RAS components, which suggests local autonomous functioning of the RAS within penile tissue. Gene expression analysis revealed strong positive correlation between ACE-Ang II-AT1 axis with markers for inflammation and fibrosis. While corpus cavernosum from 24-month-old rats was characterized by increased collagen deposition, protein expression of ACE, AT1, and Mas was shown to be upregulated in the penile tissue of this group. At the same time, penile sections from Mas-knockout mice (FVB/N background) were also shown to have increased collagen deposition. Finally, it was demonstrated that Ang-(1-7) treatment of primary cavernosal and immortalized fibroblasts was able to alleviate TGF-ß-induced fibroblast-to-myofibroblast transition. CLINICAL TRANSLATION: The present study suggests Ang-(1-7) treatment as a possible strategy for pharmacological management of fibrosis-associated ED in aging. STRENGTHS & LIMITATIONS: The link between the RAS and penile fibrosis, indicated by a holistic screening of different ED markers, was confirmed by in vivo and in vitro data. However, results, presented in the manuscript, need to be further reinforced by human data. Important to note, the main goal of the study was to characterize RAS regulation in aging condition rather than state any causal relationships. CONCLUSION: Present study characterizes RAS regulation in aging-associated ED and indicates its important role in cavernosal fibrosis. Bragina ME, Costa-Fraga F, Sturny M, et al. Characterization of the Renin-Angiotensin System in Aged Cavernosal Tissue and its Role in Penile Fibrosis. J Sex Med 2020;17:2129-2140.

Novel Concept Enabling an Old Idea: A Flexible Electrode Array to Treat Neurogenic Erectile Dysfunction.

INTRODUCTION: Many studies have shown that electrostimulation of the cavernosal nerve can induce and maintain penile erection. Based on these discoveries, neurostimulation to activate the erectile response has been considered a potential solution to treat erectile dysfunction (ED). However, despite recognized potential, this technology has not been further developed. The barrier is the complex anatomy of the human cavernous nerve, which challenges the intraoperative identification of the cavernosal nerves for electrode placement. AIM: To overcome this major barrier, we proposed a practical solution: a 2-dimensional flexible electrode array that can cover the entire plexus area, ensuring that at least 1 of the electrodes will be in optimal contact with the cavernosal nerve, without the need of intraoperative identification. The present study aims to evaluate this concept intraoperatively. METHODS: 24 patients enrolled for open radical prostatectomy were recruited. During the surgical procedures, the electrode array was positioned on the pelvic plexus (on the prostatic apex or pelvic wall) and electrical stimulation was applied to induce penile erection. Penile erectile response was assessed by (i) visual change of penile tumescence and (ii) by a penile plethysmograph system. MAIN OUTCOME MEASURE: Ability and success rate of evoking penile response were measured by applying electrical stimulation using the developed electrode array. RESULTS: Electrical stimulation produced immediate penile response in all cases when tested before (on prostatic apex) or after prostate removal (on pelvic wall). Clear visual penile engorgement was observed in 75% of the cases, whereas 25% showed minimal to moderate penile tumescence. As expected, patients with lower International Index of Erectile Function-5 score presented a reduced response, whereas stimulation before prostate removal showed greater response than following removal. Interestingly, erectile response was potentiated by bilateral stimulation (circumference increase [mm]: 2.7 ± 1.02 vs. 8.2 ± 1.9, P = .01). CLINICAL IMPLICATIONS: These data bring sufficient proof of concept of a conceivable novel medical implant for the treatment of ED caused by mechanical nerve injury, such as prostatectomy and spinal cord injury. STRENGTH & LIMITATIONS: This is the first approach that can ensure the optimal site stimulation of the erectogenic neuronal path within the lower pelvic area and overcome the major barrier of individual anatomic variability. However, because this study was performed intraoperatively in an acute scenario, further studies are needed to evaluate its chronic efficacy for clinical practice. CONCLUSION: The flexible electrode array concept can ensure the electrostimulation of erectogenic neuronal path when positioned on the prostate apex or pelvic floor. Skoufias S, Sturny M, Fraga-Silva R, et al. Novel concept enabling an old idea: A flexible electrode array to treat neurogenic erectile dysfunction. J Sex Med 2018;15:1558-1569.

Diminazene protects corpus cavernosum against hypercholesterolemia-induced injury.

INTRODUCTION: Angiotensin-converting enzyme 2 (ACE2) is a key enzyme of the renin angiotensin system, which breaks down angiotensin II and forms angiotensin-(1-7). In erectile tissues, it has been documented that angiotensin II contributes to the development of erectile dysfunction (ED), while treatment with angiotensin-(1-7) improves penile erection. However, the expression and function of ACE2 in erectile tissues have never been investigated. AIM: Here, we examined the expression of ACE2 in erectile tissues and its actions against hypercholesterolemia-induced corpus cavernosum (CC) injury. METHODS: Hypercholesterolemic apolipoprotein E knockout (ApoE(-/-) ) mice, a well-known model of ED, were treated with diminazene aceturate (DIZE), an ACE2 activator compound, or vehicle for 3 weeks. Reactive oxygen species (ROS), collagen content, and protein expression of ACE2, neuronal nitric oxide synthase (nNOS), endothelial nitric oxide synthase (eNOS), nicotinamide adenine dinucleotide phosphate-oxidase (NADPH) subunits were evaluated in the penis of DIZE-treated and untreated ApoE(-/-) mice. Functional studies were performed in CC strips. MAIN OUTCOME MEASURES: ACE2 expression and its role in modulating nitric oxide (NO)/ROS production and fibrosis within the CC of hypercholesterolemic mice were the main outcome measures. RESULTS: ACE2 was expressed in smooth muscle and endothelial cells of mouse CC. Interestingly, ACE2 was downregulated in penis of hypercholesterolemic mice with ED, suggesting a protective role of ACE2 on the CC homeostasis. In accordance with that, pharmacological ACE2 activation by DIZE treatment reduced ROS production and NADPH oxidase expression, and elevated nNOS and eNOS expression and NO bioavailability in the penis of ApoE(-/-) mice. Additionally, DIZE decreased collagen content within the CC. These beneficial actions of DIZE on the CC were not accompanied by improvements in atherosclerotic plaque size or serum lipid profile. CONCLUSION: ACE2 is expressed in erectile tissue and its reduction is associated with hypercholesterolemia-induced ED. Additionally, treatment with DIZE improved hypercholesterolemia-induced CC injury, suggesting ACE2 as a potential target for treating ED. .

An increased arginase activity is associated with corpus cavernosum impairment induced by hypercholesterolemia.

INTRODUCTION: Hypercholesterolemia is a prevalent risk factor for the development of erectile dysfunction (ED), mostly due to an increase in oxidative stress and impaired nitric oxide (NO) bioavailability within the penis. Arginase is an enzyme that shares the common substrate L-arginine with NO synthase. Augmented arginase activity reduces NO production and is associated with ED development. However, the contribution of arginase hyperactivity in hypercholesterolemia-induced ED is unknown. AIM: In the present study, we investigated the activity and role of arginase in the corpus cavernosum of hypercholesterolemic mice. METHODS: Apolipoprotein E (ApoE) gene-deleted mice fed with a Western-type diet for 11 weeks were treated with the selective arginase inhibitor, N-ω-Hydroxy-L-norarginine (NOHA), or vehicle (saline 0.9%) during the last 9 weeks. Arginase activity and expression were measured in penis protein extraction. Reactive oxygen species (ROS) content within the corpus cavernosum was measured by dihydroethidium staining. Functional in vitro studies were performed using cavernosal strips mounted in an isometric organ bath to evaluate NO production. MAIN OUTCOME MEASURE: Arginase activity and its role in modulating NO and ROS production within the corpus cavernosum of hypercholesterolemic mice is the main outcome measure. RESULTS: Total arginase activity and arginase type II protein expression were increased in hypercholesterolemic mice compared with wild-type mice. The long-term treatment with NOHA normalized this alteration. Moreover, pharmacological arginase inhibition by NOHA attenuated the augmented ROS production within the corpus cavernosum of ApoE(-/-) mice, which increased the NO-dependent response in cavernosal strips. CONCLUSION: These evidences indicate that arginase hyperactivity is associated with ED induced by hypercholesterolemia, suggesting that this enzyme is a potential target for treating ED.

Performance and safety of treatment options for erectile dysfunction in patients with spinal cord injury: A review of the literature.

BACKGROUND: For a large proportion of patients with spinal cord injury, sexuality and reproduction are important issues. However, sparse data exist regarding available treatment options for this patient population. OBJECTIVES: We sought to review performance and safety rates of all currently available treatment options for erectile dysfunction in spinal cord injury men. MATERIALS AND METHODS: A systematic literature review without time restrictions was performed using PubMed/EMBASE database for English-, Italian-, German-, and Spanish-language articles. Articles' selection was performed according to the PRISMA guidelines. Relevant papers on erectile dysfunction in spinal cord injury patients were included in the final analyses. RESULTS AND DISCUSSION: Overall, 47 studies were eligible for inclusion in this review. Of these, most evidence dealt with phosphodiesterase 5-inhibitors and intracavernous drug injection. Both treatment options are associated with high levels of performance and with patients/partners' satisfaction; side effects are acceptable. Overall, penile prostheses and vacuum erection devices are in general less approved by spinal cord injury patients and are correlated with increased rates of complications in comparison with phosphodiesterase 5-inhibitors and intracavernous drug injection. Sacral neuromodulation, transcutaneous electrical nerve stimulation, and intraurethral suppositories have been poorly studied, but preliminary studies did not show convincing results. CONCLUSION: The best treatment options for erectile dysfunction in spinal cord injury patients emerged to be phosphodiesterase 5-inhibitors and intracavernous drug injection. The choice of erectile dysfunction treatment should be based on several aspects, including residual erectile function, spinal cord injury location, and patients' comorbidities. Future studies assessing the applicability of less well-studied treatments, as well as evaluating innovative options, are needed in this specific population.