Nerve injury-related erectile dysfunction following nerve-sparing radical prostatectomy: A novel experimental dissection model

Intravenously engrafted human multilineage-differentiating stress-enduring (Muse) cells rescue erectile function after rat cavernous nerve injury

OBJECTIVE

To evaluate the effect of intravenous administration of human multilineage-differentiating stress-enduring (Muse) cells on rat postoperative erectile dysfunction (ED) with cavernous nerve (CN) injury without an immunosuppressant.

MATERIALS AND METHODS

Male Sprague-Dawley rats were randomised into three groups after CN crush injury. Either human-Muse cells, non-Muse mesenchymal stem cells (MSCs) (both 1.0 × 105 cells), or vehicle was infused intravenously at 3 h after CN injury without immunosuppressant. Erectile function was assessed by measuring intracavernous pressure (ICP) and arterial pressure (AP) during pelvic nerve electrostimulation 28 days after surgery. At 48 h and 28 days after intravenous infusion of Muse cells, the homing of Muse cells and non-Muse MSCs was evaluated in the major pelvic ganglion (MPG) after CN injury. In addition, expressions of C-X-C motif chemokine ligand (Cxcl12) and glial cell line-derived neurotrophic factor (Gdnf) in the MPG were examined by real-time polymerase chain reaction. Statistical analyses and comparisons among groups were performed using one-way analysis of variance followed by the Tukey test for parametric data and Kruskal-Wallis test followed by the Dunn-Bonferroni test for non-parametric data.

RESULTS

The mean (SEM) ICP/AP values at 28 days were 0.51 (0.02) in the Muse cell group, 0.37 (0.03) in the non-Muse MSC group, and 0.36 (0.04) in the vehicle group, showing a significant positive response in the Muse cell group compared with the non-Muse and vehicle groups (P = 0.013 and P = 0.010, respectively). In the MPG, Muse cells were observed to be engrafted at 48 h and expressed Schwann cell markers S100 (~46%) and glial fibrillary acidic protein (~24%) at 28 days, while non-Muse MSCs were basically not engrafted at 48 h. Higher gene expression of Cxcl12 (P = 0.048) and Gdnf (P = 0.040) was found in the MPG of the Muse group than in the vehicle group 48 h after infusion.

CONCLUSION

Intravenously engrafted human Muse cells recovered rat erectile function after CN injury in a rat model possibly by upregulating Cxcl12 and Gdnf.

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.

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.

Nerve-targeted probes for fluorescence-guided intraoperative imaging

A fundamental goal of many surgeries is nerve preservation, as inadvertent injury can lead to patient morbidity including numbness, pain, localized paralysis and incontinence. Nerve identification during surgery relies on multiple parameters including anatomy, texture, color and relationship to surrounding structures using white light illumination. We propose that fluorescent labeling of nerves can enhance the contrast between nerves and adjacent tissue during surgery which may lead to improved outcomes.

Methods: Nerve binding peptide sequences including HNP401 were identified by phage display using selective binding to dissected nerve tissue. Peptide dye conjugates including FAM-HNP401 and structural variants were synthesized and screened for nerve binding after topical application on fresh rodent and human tissue and in-vivo after systemic IV administration into both mice and rats. Nerve to muscle contrast was quantified by measuring fluorescent intensity after topical or systemic administration of peptide dye conjugate.

Results: Peptide dye conjugate FAM-HNP401 showed selective binding to human sural nerve with 10.9x fluorescence signal intensity (1374.44 ± 425.96) compared to a previously identified peptide FAM-NP41 (126.17 ± 61.03). FAM-HNP401 showed nerve-to-muscle contrast of 3.03 ± 0.57. FAM-HNP401 binds and highlight multiple human peripheral nerves including lower leg sural, upper arm medial antebrachial as well as autonomic nerves isolated from human prostate.

Conclusion: Phage display has identified a novel peptide that selectively binds to ex-vivo human nerves and in-vivo using rodent models. FAM-HNP401 or an optimized variant could be translated for use in a clinical setting for intraoperative identification of human nerves to improve visualization and potentially decrease the incidence of intra-surgical nerve injury.

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.

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.

The effect of cavernous nerve traction on erectile function in rats

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

Gene expression profile comparison in the penile tissue of diabetes and cavernous nerve injury-induced erectile dysfunction rat model

PURPOSE

To investigate the effects of cavernous nerve injury (CNI) on gene expression profiles in the cavernosal tissue of a CNI-induced erectile dysfunction (ED) model and to provide a basis for future investigations to discover potential target genes for ED treatment.

MATERIALS AND METHODS

Young adult rats were divided randomly into 2 groups: sham operation and bilateral CN resection. At 12 weeks after CNI we measured erectile responses and performed microarray experiments and gene set enrichment analysis to reveal gene signatures that were enriched in the CNI-induced ED model. Alterations in gene signatures were compared with those in the diabetes-induced ED model. The diabetic-induced ED data is taken from GSE2457.

RESULTS

The mean ratio of intracavernosal pressure/blood pressure for the CNI group (0.54±0.4 cmH2O) was significantly lower than that in the sham operation group (0.73±0.8 cmH2O, p<0.05). Supervised and unsupervised clustering analysis showed that the diabetes- and CNI-induced ED cavernous tissues had different gene expression profiles from normal cavernous tissues. We identified 46 genes that were upregulated and 77 genes that were downregulated in both the CNI- and diabetes-induced ED models.

CONCLUSIONS

Our genome-wide and computational studies provide the groundwork for understanding complex mechanisms and molecular signature changes in ED.

Intravenous Preload of Mesenchymal Stem Cells Rescues Erectile Function in a Rat Model of Cavernous Nerve Injury

INTRODUCTION

We evaluated the potential preventive effects and mechanisms of intravenously preloaded mesenchymal stem cells (MSCs) for erectile dysfunction (ED) in a cavernous nerve (CN) injury model.

METHODS

Male Sprague-Dawley (SD) rats were used for this study. Rats were randomized into two groups. One group was intravenously preloaded with MSCs (1.0 × 10(6) cells in 1 mL total fluid volume) and the other was infused with medium alone (1 mL Dulbecco's modified Eagle's medium [DMEM]) for sham control, respectively. Crushed CN injury was induced immediately after infusion. The surgeon was blind to the experimental conditions (MSC or medium).

MAIN OUTCOME MEASURES

To assess erectile function, we measured the intracavernous pressure (ICP) and arterial pressure (AP) at 1 hour and 2 weeks after CN injury. After measuring the initial ICP/AP of pre-injury (normal) male SD rats, they were randomized into the two groups and infused with MSCs or medium. PKH26-labelled MSCs were used for tracking. To investigate the mRNA expression levels of neurotrophins in the major pelvic ganglia (MPG), we performed real-time quantitative real-time polymerase chain reaction.

RESULTS

The reduction of ICP/AP and area under the curve of ICP (ICP-AUC) in the MSC group was significantly lower than in the DMEM group (P < 0.05; P < 0.05) at 1 hour. The ICP/AP and ICP-AUC at 2 weeks post-injury in the MSC group was significantly higher than in the DMEM group (P < 0.01; P < 0.05). The preloaded PKH26-labelled MSCs were detected in the MPG and CN using confocal microscopy indicating homing of the cells to the injured nerve and ganglia. Glia cell-derived neurotrophic factor (GDNF) and neurturin, which are important neurotrophic factors for erection, had expression levels in MPG significantly higher in the MSC group than in the DMEM group (P < 0.01, 0.05).

CONCLUSION

Intravenous preload of MSCs before a CN injury may prevent or reduce experimental ED.

Axotomy of tributaries of the pelvic and pudendal nerves induces changes in the neurochemistry of mouse dorsal root ganglion neurons and the spinal cord

Using immunohistochemical techniques, we characterized changes in the expression of several neurochemical markers in lumbar 4-sacral 2 (L4-S2) dorsal root ganglion (DRG) neuron profiles (NPs) and the spinal cord of BALB/c mice after axotomy of the L6 and S1 spinal nerves, major tributaries of the pelvic (targeting pelvic visceral organs) and pudendal (targeting perineum and genitalia) nerves. Sham animals were included. Expression of cyclic AMP-dependent transcription factor 3 (ATF3), calcitonin gene-related peptide (CGRP), transient receptor potential cation channel subfamily V, member 1 (TRPV1), tyrosine hydroxylase (TH) and vesicular glutamate transporters (VGLUT) types 1 and -2 was analysed seven days after injury. L6-S1 axotomy induced dramatic de novo expression of ATF3 in many L6-S1 DRG NPs, and parallel significant downregulations in the percentage of CGRP-, TRPV1-, TH- and VGLUT2-immunoreactive (IR) DRG NPs, as compared to their expression in uninjured DRGs (contralateral L6-S1-AXO; sham mice); VGLUT1 expression remained unaltered. Sham L6-S1 DRGs only showed a small ipsilateral increase in ATF3-IR NPs (other markers were unchanged). L6-S1-AXO induced de novo expression of ATF3 in several lumbosacral spinal cord motoneurons and parasympathetic preganglionic neurons; in sham mice the effect was limited to a few motoneurons. Finally, a moderate decrease in CGRP- and TRPV1-like-immunoreactivities was observed in the ipsilateral superficial dorsal horn neuropil. In conclusion, injury of a mixed visceral/non-visceral nerve leads to considerable neurochemical alterations in DRGs matched, to some extent, in the spinal cord. Changes in these and potentially other nociception-related molecules could contribute to pain due to injury of nerves in the abdominopelvic cavity.

Penile rehabilitation: the evolutionary concept in the management of erectile dysfunction

A compromise in erectile function is commonly experienced after radical prostatectomy and has been attributed to injury to vascular, neurogenic, and smooth muscle. The concept of rehabilitation after organ injury is not a novel concept and is one that has been applied to all aspects of medicine. Penile rehabilitation has been classically defined as the use of a device or pharmacologic agent to aid erectile function recovery after radical prostatectomy. Here we redefine penile rehabilitation as the use of any device, medication, or intervention to promote male sexual function as a primer before and after any insult to the penile erectile physiologic axis. We also review the epidemiology, rational and current literature on penile rehabilitation after prostatectomy.

Comparative analysis of periprostatic implantation and intracavernosal injection of human adipose tissue-derived stem cells for erectile function recovery in a rat model of cavernous nerve injury

BACKGROUND

We compared periprostatic implantation (PPI) and intracavernosal injection (ICI) of human adipose tissue-derived stem cell (ADSC) to facilitate recovery of erectile function in a rat model of cavernous nerve (CN) injury.

METHODS

Bilateral CN dissection (BCND) was induced in Sprague-Dawley rats. After BCND 10 rats each were treated with PPI and/or ICI of ADSCs. After 4 weeks erectile responses to electric pelvic ganglion stimulation were studied. Each penis was evaluated in terms of the expression of neuronal nitric oxide synthase and smooth muscle content.

RESULTS

The ratio of maximal intracavernosal pressure to mean arterial pressure was significantly decreased in the BCND group (24.5%) compared to the sham group (64.2%). PPI and ICI significantly improved erectile function (46.7% and 47.9%, respectively) compared to the BCND group. A combination of PPI and ICI (42.5%) did not afford any incremental effect on erectile function. After stem cell therapy, the expression of neuronal nitric oxide synthase increased slightly in the ICI group without statistical relevance, whereas the PPI and combination groups showed marginally significant increases (P = 0.08). In both the PPI and ICI groups, the smooth muscle content was similar to the sham group. The combination group showed remarkable increase in smooth muscle content to an extent greater than that seen when either treatment was given alone, although statistically not significant.

CONCLUSION

PPI or ICI of ADSCs in a rat model of CN injury were equally effective in recovering penile erection, but may address different types of pathophysiology.