Molecular pathogenesis and treatment of cavernous nerve injury-induced erectile dysfunction: A narrative review

Ex-vivo antioxidant, enzyme inhibitory properties and computational analysis unveil the molecular mechanism of cardiac and penile phosphodiesterase-5 inhibition by bacterial strain HOKA1 extract as an aphrodisiac's agent

The study uses in-vitro antioxidant, ex-vivo enzyme kinetics and in-silico approach using standard protocols to understand their inhibitory mechanism better. The study revealed that bacterial strain HOKA1 isolated from Oniru beach, grown in nutrient agar supplemented with sodium chloride (30%NaCl). Moreso, the bacterial strain HOKA1 extract showed better antioxidant capability and greatly reduced the penile and cardiac cGMP with the highest penile and cardiac concentration between 0.013 and 0.183 μM/Min as compared to the sildenafil citrate (0.00-0.203 μM/Min). Moreover, the kinetic parameters (Vmax and Km) effects revealed that bacterial strain HOKA1 extract inhibited PDE-5 activities better than sildenafil citrate. The GC-MS analysis revealed twenty-nine bioactive compounds in the extract, and these compounds could provide comprehensible supporting evidence for the antioxidant and inhibitory potential of the strain HOKA1 extract on PDE-5 activity. Molecular docking study revealed majority of the GC-MS-identified bioactive constituents from the HOKA1 extract showed high binding energy or lower bonding affinities (-6.8 to -3.3 kcal/mol) compared to reference drug sildenafil citrate (-9.6 kcal/mol), except campesterol (-10.0 kcal/mol); also, ergostane (-9.9 kcal/mol). The results of 100 ns simulation (RMSF, RMSD, Rg and H-bond) show extraordinary stability of PDE-5 with campesterol and ergostane, so also complimentary binding energy of MM-PBSA (campesterol -65.92±4.09 kcal/mol; ergostane -57.23±4.70 kcal/mol) indicating their probability of acting promising PDE-5 inhibitors. Therefore, the study revealed that bacterial strain HOKA1 extract showed a better aphrodisiac property, and its bioactive compounds (campesterol and ergostane) should be considered in upcoming rational development and design of more active selective PDE-5 inhibitors, making a treatment for erectile dysfunction.

Prenatal exposure to dibutyl phthalate contributes to erectile dysfunction in offspring male rats by activating the RhoA/ROCK signalling pathway

Prenatal exposure to dibutyl phthalate (DBP) has been reported to cause erectile dysfunction (ED) in adult offspring rats. However, its underlying mechanisms are not fully understood. Previously, we found that DBP activates the RhoA/ROCK pathway in the male reproductive system. This study investigated how prenatal exposure to DBP activates the RhoA/ROCK signalling pathway, leading to ED in male rat offspring. Pregnant rats were stratified into DBP-exposed and NC groups, with the exposed group receiving 750 milligrams per kilogram per day (mg/kg/day) of DBP through gavage from days 14-18 of gestation. DBP exposure activated the RhoA/ROCK pathway in the penile corpus cavernosum (CC) of descendants, causing smooth muscle cell contraction, fibrosis, and apoptosis, all of which contribute to ED. In vitro experiments confirmed that DBP induces apoptosis and RhoA/ROCK pathway activation in CC smooth muscle cells. Treatment of DBP-exposed offspring with the ROCK inhibitor Y-27632 for 8 weeks significantly improved smooth muscle cell condition, erectile function, and reduced fibrosis. Thus, prenatal DBP exposure induces ED in offspring through RhoA/ROCK pathway activation, and the ROCK inhibitor Y-27632 shows potential as an effective treatment for DBP-induced ED.

The correlation between premature ejaculation and a high incidence of erectile dysfunction and its research progress: a narrative review

Background and Objective

Premature ejaculation (PE) and erectile dysfunction (ED) are two common sexual symptoms of male sexual dysfunction that can strongly affect men's mental health and quality of life, and they often coexist. This aim of this study was to explore the causes and relationships between PE and ED, with a focus on the progression of PE accompanied by high-frequency ED. A deeper understanding of the causes and treatments for PE combined with ED will help improve clinical diagnosis and treatment.

Methods

We conducted a literature review of the most relevant articles related to the outlined topic in the PubMed, Google Scholar, and Web of Science databases. We did not limit language, covering both English and non-English publications, and include Chinese and English papers published between January 1996 and March 2024.

Key Content and Findings

The incidence of PE and ED increases with age. Approximately one-third of patients who complain of ED suffer from PE. Similarly, in a large-scale survey in the Asia-Pacific region, more than 30% of patients with PE reported concurrent ED. Various research findings indicate a strong correlation between PE and ED. Some scholars speculate that there is a vicious cycle between PE and ED. Men who attempt to control ejaculation can reduce the level of arousal, leading to ED, whereas men who try to achieve an erection will attempt to increase the level of arousal, which can lead to PE. This cycle of mutual influence may lead to reciprocal aggravation and persistence of sexual dysfunction in both parties. Although some studies have explored the relationship between PE and ED, the specific determinants and underlying factors have not yet been clarified.

Conclusions

There is a close interrelationship between PE and ED, and a vicious cycle may exist between the two. This cycle of mutual influence may lead to the mutual aggravation and persistence of both sexual dysfunctions. However, the specific determining factors and potential factors underlying the correlation between the two have not been clearly identified and require further exploration.

An update on the use of stem cell therapy for erectile dysfunction

Objective

This systematic review aimed to analyze animal and human trial data to better understand the efficacy of stem cell therapy (SCT) for erectile dysfunction (ED) and the obstacles that may hinder its application in this field.

Methods

We searched electronic databases, including PubMed and Scopus, for published studies with the Medical Subject Heading terms of "erectile dysfunction" (AND) "stem cell therapy" (OR) "erectile dysfunction" (AND) "clinical trial of stem cell therapy" (OR) "stem cell therapy" (AND) "sexual dysfunction". The search was limited to English-language journals and full papers only. The initial search resulted in 450 articles, of which 90 relevant to our aims were included in the analysis.

Results

ED is a multifactorial disease. Current treatment options rely on pharmacotherapy as well as surgical options. Patients may have side effects or unsatisfactory results following the use of these treatment options. SCT may restore pathophysiological changes leading to ED rather than treating the symptoms. It has been evaluated in animal models and shown promising results in humans. Results confirm that SCT does improve erectile function in animals with different types of SC use. In humans, evidence showed promising results, but the trials were heterogeneous and limited mainly by a lack of randomization and the small sample size. Many challenges could limit future research in this field, including ethical dilemmas, regulation, patient recruitment, the cost of therapy, and the lack of a standardized SCT regimen. Repairing and possibly replacing diseased cells, tissue, or organs and eventually retrieving normal function should always be the goals of any therapy, and this can only be guaranteed by SCT.

Conclusion

SCT is a potential and successful treatment for ED, particularly in patients who are resistant to the classic therapy. SCT may promote nerve regeneration and vascular cell regeneration, not only symptomatic treatment.

Repeated Injections of Mesenchymal Stem Cell-Derived Exosomes Ameliorate Erectile Dysfunction in a Cavernous Nerve Injury Rat Model

PURPOSE

To evaluate the therapeutic effect of repeated injections of mesenchymal stem cell (MSC)-derived exosomes on the erectile dysfunction (ED) of bilateral cavernous nerve injury (BCNI) rat model and to identify potential target genes of these injections.

MATERIALS AND METHODS

MSC-derived exosomes were isolated using an aqueous two-phase system. Rats were randomly assigned into four groups: Normal, BCNI, exosome once, and exosome-repeat groups. After four weeks, we measured the intracavernosal pressure (ICP)/mean arterial pressure (MAP) ratio to evaluate erectile function and examined cavernous nerve tissues for histological and molecular analyses. RNA sequencing in penile tissues was used to determine differentially expressed genes and was verified by quantitative polymerase chain reaction. Human umbilical vein endothelial cells (HUVECs) were used for in vitro studies to analyze biological roles.

RESULTS

The ICP/MAP ratios in the exosome-once and exosome-repeat groups were significantly increased compared to those in the BCNI group. Interestingly, the ICP/MAP ratio showed a greater increase in the exosome-repeat group, which also showed significantly increased smooth muscle/collagen ratio, α-smooth muscle actin and neuronal nitric oxide synthase expression, and cyclic guanosine monophosphate level compared to the BCNI and exosome-once groups. Three genes were significantly differentially expressed in the exosome group, among which Ras homolog family member B promoted cell proliferation and angiogenesis of HUVECs.

CONCLUSIONS

Repeated injections of MSC-derived exosomes can be effective in the treatment of rat models with ED induced by cavernous nerve injury.

A potential treatment for erectile dysfunction: Effect of platelet-rich plasma administration on axon and collagen regeneration in cavernous nerve injury

Recent studies highlighted the role of platelet-rich plasma (PRP) in progenitor cell homing, migration, and nerve cell regeneration while also inhibiting fibrosis and apoptosis in cavernous nerve injury (CNI). The aim of this study was to investigate the effect of PRP administration on axon and collagen regeneration in CNI. A true experimental study using a post-test-only control group design was conducted. Twenty-five male Wistar rats (Rattus norvegicus), weighing 200-300 grams, were divided into five groups: two control groups (sham procedure and negative control), and three experimental groups receiving local PRP, intraperitoneal PRP, and a combination of local and intraperitoneal PRP. The cavernous nerve was injured with a hemostasis clamp for one minute before 200 µL of 200 PRP was injected locally, intraperitoneally, or both, depending on the group. After four weeks, the rats were euthanized, tissue segments (2 mm) from each cavernous nerve and mid-penis were collected and analyzed for collagen density, axon diameter, and number of myelinated axons. Our study found that collagen growth was slower in CNI group without PRP (sham procedure) compared to all PRP groups (local, intraperitoneal, and combination). The intraperitoneal PRP group had the highest collagen density at 5.62 µm; however, no significant difference was observed in collagen density among all groups (p=0.056). Similar axon diameter was found across the groups, with no statistically significant difference observed (p=0.856). In the number of myelinated axons, a significant difference was found among all groups with significantly more axons in local PRP and combined local and intraperitoneal PRP groups compared to others (p=0.026). In conclusion, PRP administration improved the number of myelinated axons in CNI, suggesting PRP role in CNI regeneration and the potential for an innovative approach to treating erectile dysfunction associated with CNI.

Argonaute 2 restored erectile function and corpus cavernosum mitochondrial function by reducing apoptosis in a mouse model of cavernous nerve injury

PURPOSE

To determine whether the overexpression of the Argonaute RNA-induced silencing complex catalytic component 2 (Ago2) improves erectile function in mice after cavernous nerve injury (CNI).

MATERIALS AND METHODS

Lentiviruses containing Ago2 open reading frame (ORF) mouse clone (Ago2 O/E) were used to overexpress Ago2, and lentiviruses ORF negative control particles (NC) were used as a negative control. Three days before preparing the CNI model, we injected lentiviruses into the penises of 8-week-old male C57BL/6 mice. Animals were then divided into four groups: the sham operation control group and the CNI+phosphate-buffered saline, CNI+NC, and CNI+Ago2 O/E groups. One week later, erectile function was assessed by electrically stimulating cavernous nerves bilaterally and obtaining intracavernous pressure parameters. Penile tissue was also collected for molecular mechanism studies.

RESULTS

Ago2 overexpression improved erectile function in mice after CNI-induced erectile dysfunction (ED). Immunofluorescence staining and Western blot analysis showed that under Ago2 overexpressing conditions, the contents of endothelial cells, pericytes, and neuronal cells increased in the penile tissues of CNI mice, and this was attributed to reduced apoptosis and ROS production. In addition, we also found that Ago2 overexpression could restore penile mitochondrial function, thereby improving erectile function in CNI-induced ED mice.

CONCLUSIONS

Our findings demonstrate that Ago2 overexpression can reduce penile cell apoptosis, restore penile mitochondrial function, and improve erectile function in CNI-induced ED mice.

Caveolin-1 scaffolding domain-derived peptide enhances erectile function by regulating oxidative stress, mitochondrial dysfunction, and apoptosis of corpus cavernosum smooth muscle cells in rats with cavernous nerve injury

AIM

Increased corpus cavernosum smooth muscle cells (CCSMCs) apoptosis in the penis due to cavernous nerve injury (CNI) is a crucial contributor to erectile dysfunction (ED). Caveolin-1 scaffolding domain (CSD)-derived peptide has been found to exert potential antiapoptotic properties. However, whether CSD peptide can alleviate CCSMCs apoptosis and ED in CNI rats remains unknown. The study aimed to determine whether CSD peptide can improve bilateral CNI-induced ED (BCNI-ED) by enhancing the antiapoptotic processes of CCSMCs.

MAIN METHODS

Fifteen 10-week-old male Sprague-Dawley (SD) rats were randomly classified into three groups: sham surgery (Sham) group and BCNI groups that underwent saline or CSD peptide treatment respectively. At 3 weeks postoperatively, erectile function was assessed and the penis tissue was histologically examined. Furthermore, an in vitro model of CCSMCs apoptosis was established using transforming growth factor-beta 1 (TGF-β1) to investigate the mechanism of CSD peptide in treating BCNI-ED.

KEY FINDINGS

In BCNI rats, CSD peptide significantly prevented ED and decreased oxidative stress, the Bax/Bcl-2 ratio, and the levels of caspase3. TGF-β1-treated CCSMCs exhibited severe oxidative stress, mitochondrial dysfunction, and apoptosis. However, CSD peptide partially reversed these alterations.

SIGNIFICANCE

Exogenous CSD peptide could improve BCNI-ED by inhibiting oxidative stress, the Bax/Bcl-2 ratio, and caspase3 expression in penile tissue. The underlying mechanism might involve the regulatory effects of CSD peptide on oxidative stress, mitochondrial dysfunction, and apoptosis of CCSMCs following CNI. This study highlights CSD peptide as an effective therapy for post-radical prostatectomy ED (pRP-ED).

Investigating neuropathological changes and underlying neurobiological mechanisms in the early stages of primary blast-induced traumatic brain injury: Insights from a rat model

The utilization of explosives and chemicals has resulted in a rise in blast-induced traumatic brain injury (bTBI) in recent times. However, there is a dearth of diagnostic biomarkers and therapeutic targets for bTBI due to a limited understanding of biological mechanisms, particularly in the early stages. The objective of this study was to examine the early neuropathological characteristics and underlying biological mechanisms of primary bTBI. A total of 83 Sprague Dawley rats were employed, with their heads subjected to a blast shockwave of peak overpressure ranging from 172 to 421 kPa in the GI, GII, and GIII groups within a closed shock tube, while the body was shielded. Neuromotor dysfunctions, morphological changes, and neuropathological alterations were detected through modified neurologic severity scores, brain water content analysis, MRI scans, histological, TUNEL, and caspase-3 immunohistochemical staining. In addition, label-free quantitative (LFQ)-proteomics was utilized to investigate the biological mechanisms associated with the observed neuropathology. Notably, no evident damage was discernible in the GII and GI groups, whereas mild brain injury was observed in the GIII group. Neuropathological features of bTBI were characterized by morphologic changes, including neuronal injury and apoptosis, cerebral edema, and cerebrovascular injury in the shockwave's path. Subsequently, 3153 proteins were identified and quantified in the GIII group, with subsequent enriched neurological responses consistent with pathological findings. Further analysis revealed that signaling pathways such as relaxin signaling, hippo signaling, gap junction, chemokine signaling, and sphingolipid signaling, as well as hub proteins including Prkacb, Adcy5, and various G-protein subunits (Gnai2, Gnai3, Gnao1, Gnb1, Gnb2, Gnb4, and Gnb5), were closely associated with the observed neuropathology. The expression of hub proteins was confirmed via Western blotting. Accordingly, this study proposes signaling pathways and key proteins that exhibit sensitivity to brain injury and are correlated with the early pathologies of bTBI. Furthermore, it highlights the significance of G-protein subunits in bTBI pathophysiology, thereby establishing a theoretical foundation for early diagnosis and treatment strategies for primary bTBI.

Nrf2 enhances the therapeutic efficiency of adipose-derived stem cells in the treatment of neurogenic erectile dysfunction in a rat model

BACKGROUND

Erectile dysfunction (ED) caused by intraoperative nerve injury is a major complication of pelvic surgery. Adipose-derived stem cells (ADSCs) have presented therapeutic potential in a rat model of bilateral cavernous nerve injury (BCNI), while inadequate in vivo viability has largely limited their application. Nuclear factor-E2-related Factor (Nrf2) is a key transcription factor that regulates cellular anti-oxidative stress. In this work, we investigated the effect of Nrf2 expression regulation on the viability of ADSCs, and explore its repair potential in a BCNI rat model.

RESULTS

The survival time of tert-Butylhydroquinone (tBHQ)-ADSCs in BCNI model increased obviously. In addition, the tBHQ-ADSCs group presented better restoration of major pelvic ganglion (MPG) nerve contents and fibers, better improvement of erectile function, and less penile fibrosis than the other groups. Moreover, the expression of Nrf2 and superoxide dismutase 1 (SOD1) were higher than those of other groups.

CONCLUSION

Nrf2 could enhance the anti-oxidative stress ability of ADSCs, so as to improve the therapeutic effect of ADSCs on BCNI rat model.

Platelet-rich plasma for the treatment of erectile dysfunction: a systematic review of preclinical and clinical studies

INTRODUCTION

There has been tremendous growth in regenerative medicine during the last decade. For erectile dysfunction (ED), after the inclusion of low-intensity shockwave therapy as a treatment modality for ED management by the European Association of Urology sexual health guidelines, intracavernosal injection of platelet-rich plasma (PRP) has gained popularity between urologists and patients as a novel ED therapeutic modality with initial promising results. However, limited clinical data exist regarding efficacy and safety in patients with ED. Furthermore, despite numerous preclinical studies in other tissues and organs, the mechanism of action for restoring erectile function remains undetermined.

OBJECTIVES

This systematic review aims to present the current status of preclinical and clinical evidence regarding the use of PRP as treatment option for ED.

METHODS

A systematic literature search was conducted using PubMed, Cochrane, and ScienceDirect databases, until February 2023 for studies exploring the effect of PRP on ED.

RESULTS

We identified 517 articles, 23 of which were included in this review. These were 7 preclinical (of which 1 was a comparative trial and 6 were placebo-controlled randomized controlled trials) and 16 clinical studies (of which 1 was a comparative trial, 5 were randomized trials, and 2 were placebo-controlled randomized controlled trials). Preclinical data support the regenerative role of PRP in erectile tissue, in accordance with existing evidence in other tissues. Randomized clinical studies, as well as the first 2 available randomized, placebo-controlled clinical trials, showed promising efficacy and a lack of any adverse events.

CONCLUSION

As PRP for ED is widely used worldwide, there is an urgent need for high-quality studies with long-term follow-up. Standardization of research protocols, especially on the quality of PRP preparation, is also needed.

Effects of endoplasmic reticulum stress on erectile function in rats with cavernous nerve injury

Background

Erectile dysfunction (ED) occurs in an increasing number of patients after radical prostatectomy and cystectomy, and the phenotypic modulation of corpus cavernosum smooth muscle cells is closely related to ED.

Aim

To determine whether endoplasmic reticulum stress (ERS) is implicated in the phenotypic modulation of ED induced by bilateral cavernous nerve injury (BCNI).

Methods

In total, 36 Sprague-Dawley rats were randomly divided into 3 groups: sham, in which rats received sham surgery with bilateral cavernous nerve exposure plus phosphate-buffered saline; control, in which rats received BCNI plus phosphate-buffered saline; and experimental, in which rats received BCNI plus 4-phenylbutyric acid. Analysis of variance and a Bonferroni multiple-comparison test were utilized to evaluate differences among groups.

Outcomes

Erectile function, smooth muscle/collagen ratios, and the expression levels of phenotypic modulation and ERS were measured.

Results

Two ratios-maximum intracavernosal pressure/mean arterial pressure and smooth muscle/collagen-were decreased in the control group as compared with the sham group. In penile tissue, there was increased expression of GRP78 (78-kDa glucose-regulated protein), p-PERK/PERK (phosphorylated protein kinase R-like endoplasmic reticulum kinase/protein kinase R-like endoplasmic reticulum kinase), caspase 3, CHOP (C/EBP homologous protein), and OPN (osteopontin) but decreased expression of nNOS (neuronal nitric oxide synthase) and α-SMA (α-smooth muscle actin). As compared with the control group, erectile function was improved and pathologic changes were partially recovered in the experimental group.

Clinical Translation

The present study demonstrated that ERS is involved in ED caused by cavernous nerve injury, thereby providing a new target and theoretical basis for clinical treatment.

Strengths and Limitations

The present study demonstrated for the first time that ERS is related to ED caused by cavernous nerve injury. Inhibition of ERS reverses phenotypic modulation and improves erectile function in rats with BCNI. Additional in vitro studies should be performed to verify these conclusions and explore the specific mechanism of phenotypic modulation.

Conclusion

The present study demonstrated that inhibiting ERS reverses phenotypic modulation and enhances erectile function in rats with BCNI.

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.

Erectile dysfunction and exosome therapy

Erectile dysfunction (ED), as a common male disease, can seriously reduce the life quality of men and their partners. With the improvement of human living standards, ED is considered to be an important health issue that plagues men. However, it is difficult for existing therapeutic approaches to meet the needs of all patients, so it is necessary to develop novel treatment strategies. Exosomes, as a class of vesicles secreted by cells with bilayer membrane structure, are involved in various physiological and pathological processes in human body and considered to have great therapeutic potentials. This review summarizes the recent advances on exosome therapy with animal models of ED, and proposes the prospect of future research in order to provide a basis for clinical trials and clinical translation.