Spontaneous recovery of cavernous nerve crush injury

The Cavernous Nerve Injury Rat Model: A Pictorial Essay on Post-Radical Prostatectomy Erectile Dysfunction Research

Understanding and addressing post-radical prostatectomy (RP) erectile dysfunction (ED) is of paramount importance for clinicians. Cavernous nerve (CN) injury rat model studies have provided consistently promising experimental data regarding regaining erectile function (EF) after nerve damage-induced ED. However, these findings have failed to translate efficiently into clinical practice, with post-RP ED therapeutic management remaining cumbersome and enigmatic. This disparity highlights the need for further standardization and optimization of the elaborate surgical preparation protocols and multifaceted reporting parameters involved in reliable CN injury rat model experimentation. Even so, despite its technical complexity, this animal model remains instrumental in exploring the functional implications of RP, i.e., surgical lesions of the neurovascular bundles (NVBs). Herein, besides cavernous nerve (CN) dissection, injury, and electrostimulation, multiple pressure measurements, i.e., mean arterial pressure (MAP) and intra-cavernosal pressure (ICP), must also be achieved. A transverse cervical incision allows for carotid artery cannulation and MAP measurements. Conversely, ICP measurements entail circumcising the penis, exposing the ischiocavernous muscle, and inserting a needle into the corporal body. Finally, using an abdominal incision, the prostate is revealed, and the major pelvic ganglia (MPG) and CNs are dissected bilaterally. Specific surgical techniques are used to induce CN injuries. Herein, we provide a narrative and illustrative overview regarding these complex experimental procedures and their particular requirements, reflecting on current evidence and future research perspectives.

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.

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.

Long-term consequences of bilateral cavernous crush injury in normal and diabetic rats: a functional study

A recent statement from the European-Society-for-Sexual-Medicine has highlighted the limitations of using the rat model for nerve-sparing prostatectomy. The use of young rats with no comorbidities and the early evaluation of the erectile function (EF) are deemed a source of bias. Our aim was to evaluate the long-term consequences in EF of bilateral nerve cavernous crush- injury (BNCI) in type 1 diabetic (DM) rats 30-male/12-week-old rats were divided into four groups: Sham, BNCI, DM, and BNCI + DM. Sham group underwent an intraperitoneal injection (IP) of saline solution and after 1 month underwent a sham laparotomy. BNCI underwent an IP of saline solution and after 1 month to BNCI. DM underwent an IP of 60 mg/kg-1-streptozotocin (STZ) and after 1 month to a sham laparotomy. BNCI + DM underwent an IP of 60 mg/kg-1-STZ and after 1 month to BNCI. After 5 months from the induction of diabetes, all rats underwent measurement of intracorporeal pressure (ICP) and mean arterial pressure (MAP) during CN-electrostimulation. Multiple groups were compared using Kruskal-Wallis one-way analysis of variance followed by Mann-Whitney U test for post hoc comparisons. Blood glucose-level was higher (p < 0.05) in the groups with DM and BNCI + DM. After 5-months, DM and BNCI + DM also showed a lower weight compared to other groups (p < 0.05). No differences were noted in ICP/MAP between the sham and BNCI. BNCI + DM showed lower ICP/MAP compared to all the groups (p < 0.05). DM Showed lower ICP/MAP compared to Sham and BNCI (p < 0.05). BNCI in rats without comorbidities did not induce long-term erectile dysfunction (ED) suggesting a spontaneous EF recovery. BNCI in DM induced long-term ED. The results of previous short-term studies can only provide evidence on the time to recovery of spontaneous EF as to the actual EF recovery rate.

Uncovering the mechanisms of leech and centipede granules in the treatment of diabetes mellitus-induced erectile dysfunction utilising network pharmacology

ETHNOPHARMACOLOGICAL RELEVANCE

Diabetes mellitus-induced erectile dysfunction (DMED) is one of the most common complications of diabetes mellitus. Leech and centipede granules (LCG) have traditionally been used as blood-activating agents in various ethnomedicinal systems of East Asia, especially in China. It is often used to regulate bodily functions and considered as adjuvant therapy for promoting blood circulation, alleviating blood coagulation, activating meridians, and relieving stasis.

AIM OF THE STUDY

This study aimed to identify potential genes and mechanisms of LCG on DMED from the network pharmacological perspective.

MATERIALS AND METHODS

The active components of LCG were identified by UHPLC-Q-TOF-MS, TCMID, and the BATMAN-TCM databases, and the disease targets of DMED were obtained from the DisGeNET, CooLGeN, GeneCards databases. After identifying DMED targets of LCG, a protein-protein interaction (PPI) network was constructed. Hub genes and significant modules were identified via the MCODE plug-in of Cytoscape software. Then, significant signaling pathways of the modules were identified using the Metascape database. The probable interaction mode of compounds-hub genes is examined using Molecular Operating Environment (MOE) docking software. Besides, we investigated the effects and mechanisms of LCG on improving erectile function in the streptozotocin (STZ)-induced diabetic rats model.

RESULTS

Combined UHPLC-Q-TOF-MS analysis with network pharmacology study, 18 active compounds were selected for target prediction. There are 97 common target genes between LCG and DMED. Enrichment of the KEGG pathway mainly involves in the calcium signaling pathway, NF-kappa B signaling pathway, cGMP-PKG signaling pathway, HIF-1 signaling pathway, PI3K-Akt signaling pathway, and mTOR signaling pathway. Nine hub genes were regulated by LCG in DMED, including CXCL8, NOS3, CRH, TH, BDNF, DRD4, ACE, CNR1, and HTR1A. The results of molecular docking analysis showed that the tyrosin, ursolic acid, and L-Histidine has a relatively stable interaction with corresponding hub genes via generating hydrogen bonds, H-π, and π-π interactions. Significantly, the results in docking predicted a higher affinity of vardenafil to the hub genes compared to the tyrosin, ursolic acid, and L-Histidine. Furthermore, LCG increased the testosterone, erection frequency, the ratio of ICP and MAP, SOD, cGMP, cAMP as well as decreased the MDA, and AGEs expression levels. And, LCG ameliorated the histological change of penile tissues in DMED rats. Hence, LCG attenuates oxidative stress, increases NO production; For the mechanism exploration, LCG could significantly upregulate the mRNA and protein expression of CNR1, NOS3, CRH, TH, BDNF, and DRD4, whereas CXCL8, ACE, and HTR1A levels were significantly higher than those in the DMED group. Moreover, LCG activates the NO/cGMP/PKG pathway, PI3K/Akt/nNOS pathway, cAMP/PKA pathway, and inhibits the HIF-1α/mTOR pathway to improve erectile function.

CONCLUSIONS

Our results suggest that LCG maybe offer a new therapeutic basis for the treatment of DMED via altering the gene expression of involved metabolic pathways.

Hedging against Neuropathic Pain: Role of Hedgehog Signaling in Pathological Nerve Healing

The peripheral nervous system has important regenerative capacities that regulate and restore peripheral nerve homeostasis. Following peripheral nerve injury, the nerve undergoes a highly regulated degeneration and regeneration process called Wallerian degeneration, where numerous cell populations interact to allow proper nerve healing. Recent studies have evidenced the prominent role of morphogenetic Hedgehog signaling pathway and its main effectors, Sonic Hedgehog (SHH) and Desert Hedgehog (DHH) in the regenerative drive following nerve injury. Furthermore, dysfunctional regeneration and/or dysfunctional Hedgehog signaling participate in the development of chronic neuropathic pain that sometimes accompanies nerve healing in the clinical context. Understanding the implications of this key signaling pathway could provide exciting new perspectives for future research on peripheral nerve healing.

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.

nNOS-positive minor-branches of the dorsal penile nerves is associated with erectile function in the bilateral cavernous injury model of rats

The changes in neuronal nitric oxide synthases (nNOS) in the dorsal penile nerves (DPNs) are consistent with cavernous nerve (CN) injury in rat models. However, the anatomical relationship and morphological changes between the minor branches of the DPNs and the CNs after injury have never been clearly explored. There were forty 12 week old male Sprague-Dawley rats receiving bilateral cavernous nerve injury (BCNI). Erectile function of intracavernous pressure and mean arterial pressure were measured. The histology and ultrastructure with H&E stain, Masson's trichrome stain and immunohistochemical stains were applied on the examination of CNs and DPNs. We demonstrated communicating nerve branches between the DPNs and the CNs in rats. The greatest damage and lowest erectile function were seen in the 14^th day and partially recovered in the 28^th day after BCNI. The nNOS positive DPN minor branches' number was significantly correlated with erectile function. The sub-analysis of the number of nNOS positive DPN minor branches also matched with the time course of the erectile function after BCNI. We suggest the regeneration of the DPNs minor branches would ameliorate the erectile function in BCNI rats.

α1A-Adrenergic Receptor Antagonism Improves Erectile and Cavernosal Responses in Rats With Cavernous Nerve Injury and Enhances Neurogenic Responses in Human Corpus Cavernosum From Patients With Erectile Dysfunction Secondary to Radical Prostatectomy

INTRODUCTION

Cavernous nerve injury (CNI) in rats and radical prostatectomy (RP) in men result in loss of nitrergic function and increased adrenergic-neurogenic contractions of cavernosal tissue.

AIM

To evaluate the modulation of the α-adrenergic system as a strategy to relieve erectile dysfunction (ED) and functional cavernosal alterations induced by CNI.

METHODS

A non-selective α-blocker (phentolamine 1 mg/kg daily), a selective α_1A-blocker (silodosin [SILOD] 0.1 mg/kg daily), or vehicle was orally administered for 4 weeks after bilateral crush CNI (BCNI). Erectile and neurogenic responses of the corpus cavernosum (CC) were evaluated. The acute effects of SILOD also were evaluated in vivo (0.03 mg/kg intravenously) and ex vivo (10 nmol/L). The effects of SILOD and tadalafil (TAD) on nitrergic relaxations were determined in human CC from patients with ED with a vascular etiology or ED secondary to RP.

MAIN OUTCOME MEASURES

Erectile responses in vivo in rats and neurogenic contractions and relaxations of rat and human CC.

RESULTS

Long-term treatment with SILOD significantly improved erectile responses and allowed for the potentiation of erectile responses by acute treatment with TAD (0.3 mg/kg intravenously) in rats with BCNI. SILOD partly recovered nitrergic relaxations and normalized neurogenic contractions in CC from rats with BCNI. Long-term treatment with SILOD partly prevented BCNI-induced decreases in neuronal nitric oxide synthase expression. Acute administration of SILOD (0.03 mg/kg intravenously) improved erectile responses in vivo and potentiated nitrergic relaxation and decreased neurogenic contractions ex vivo in CC from rats with BCNI. In human CC from patients with ED with a vascular etiology, TAD (30 nmol/L), SILOD (10 nmol/L), or their combination increased nitrergic relaxations. Potentiation by TAD was lost in human CC from patients with ED after RP but was recovered after co-treatment with SILOD.

CONCLUSION

α-Adrenergic modulation, especially selective α_1A-blockade, improves erectile and cavernosal functions after BCNI. Modulation of the adrenergic system, mainly in combination strategies, could have a role in the management of ED after RP.

Stem cell therapy for erectile dysfunction of cavernous nerve injury rats: a systematic review and meta-analysis

INTRODUCTION

Stem cell treatment is a novel therapeutic strategy for erectile dysfunction (ED) patients with bilateral cavernous nerve injury (CNI). The relative animal studies provide important clues to design pre-clinical studies and clinical studies further in the future.

PURPOSE

This study aims to evaluate the effects and influential factors of stem cell transplantation on ED rats with CNI.

MATERIALS AND METHODS

We searched PubMed and EBSCO databases published before April 30, 2014 for pre-clinical studies to evaluate the efficacy of stem cell transplantation in the treatment of ED rats with CNI. A systematic review and a planned subgroup analysis were performed to identify whether or not some certain influential factors could bring significant effects on stem cell treatment.

RESULTS

12 studies with 319 rats were enrolled in this meta-analysis. Pooled analysis results confirmed the efficacy of stem cell transplantation. Subgroup analysis results showed that treatment effects were not related to CNI models, follow-up time, stem cell species, stem cell sources, markers and delivery approaches in the transplantation. Uncultured stem cells were poorly effective compared with cultured stem cells. Periprostatic implantation (PPI) with acellular scaffolds could promote cavernous nerve regeneration, but was less effective for smooth muscle cell recovery. Stem cells modified by NGF or BDNF combined with udenafil/bFGF seemed to be more effective than those modified by BDNF alone.

CONCLUSION

This meta-analysis shows that stem cell therapy can be performed to recover erectile function. Future studies should focus on nerve restoration and vascular cell recovery. The synergistic actions of multiple growth factors following stem cell transplantation should also be considered as beneficial strategies to obtain preferable effects.

Penile rehabilitation with phosphodiesterase type 5 inhibitors after nerve-sparing radical prostatectomy: are we targeting the right patients?

The results reported in all trials comparing chronic versus on-demand phosphodiesterase type 5 inhibitor use after bilateral nerve-sparing radical prostatectomy may be affected by improper patient selection. Targeting the right patients is the key to optimizing the efficacy of these drugs.