Cavernous Nerve Injury by Radiation Therapy May Potentiate Erectile Dysfunction in Rats

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.

Downregulation of the expression of galanin impairs erectile function in hypoandrogenic rats

Background

The relationship between galanin and erectile function under low androgen levels is still unclear.

Aim

To explore whether a low testosterone level damages the erection of a rat by regulating the expression of galanin and GalR in penile cavernous tissue.

Methods

Thirty-six male Sprague-Dawley rats, 8 weeks of age, were randomly grouped as follows (n = 6): control, castration, castration + testosterone replacement, control + transfection, castration + transfection, and castration + empty transfection. At 4 weeks after castration, rats in the transfection group were injected with lentivirus carrying the targeting galanin gene (2 × 10⁸ TU/mL, 10 μL) in the corpus cavernosum. After 1 week of injection, the intracavernosal pressure (ICP), mean arterial blood pressure (MAP), nitric oxide (NO), serum testosterone concentration, galanin, GalR1-3, ROCK1, ROCK2, and p-eNOS/eNOS in the rat penile tissues were evaluated.

Outcomes

ICPmax/MAP and the expression of galanin in the corpus cavernosum in castrated rats were obviously decreased as compared with those in the control rats.

Results

The castrated rats showed remarkably lower ICPmax/MAP, galanin, GalR1-3, p-eNOS/eNOS, and NO content and markedly higher ROCK1 and ROCK2 in penile tissues than the control group (P < .05). The transfected rats administrated with LV Gal had obviously higher ICPmax/MAP, p-eNOS/eNOS, and NO content and less ROCK1 and ROCK2 protein expression in the corpus cavernosum when compared with the castration group (P < .05).

Clinical Translation

Upregulating the expression of galanin in the penile corpus cavernosum might be a novel method of treating erectile dysfunction caused by a low androgen level.

Strengths and Limitations

The conclusions obtained in the animal experiments need to be confirmed in human data.

Conclusion

The erectile function of hypoandrogen rats might be inhibited by downregulating the level of galanin and GalR1-3, upregulating ROCK1 and ROCK2 levels, and inhibiting the eNOS/NO signaling pathway in penile corpus cavernosum.

Intracavernous injection of platelet-rich plasma reverses erectile dysfunction of chronic cavernous nerve degeneration through reduction of prostate hyperplasia evidence from an aging-induced erectile dysfunction rat model

Age-induced erectile dysfunction (ED) is a convoluted medical condition, and restoring erectile function (EF) under geriatric conditions is highly complicated. Platelet-rich plasma (PRP) treatment is an inexpensive cell-based therapeutic strategy. We have aimed to restore EF in aged-ED rats with PRP as a therapeutic tool. Male rats were grouped into aged and young according to age. The young rats were considered as normal control (NC) and treated with saline. Aged were further divided into 2 groups and treated with intracavernous (IC) PRP and saline. Treatment was scheduled at the 9th and 10th week for NC and 41th and 42th week for aged-ED rats, with EF analysis scheduled on the 12th week for NC and 44th week for aged-ED rats, respectively. Erectile response, immunofluorescence staining, and electron microscopic analyses were performed. IC PRP treatment effectively reduced prostate hyperplasia (PH). EF response indicated a significant increase in crucial EF parameters in PRP-treated aged-ED rats. Histological evidence denoted a rigid and restored development of tunica adventitia of the dorsal artery, decreased vacuolation of the dorsal penile nerve, and structural expansion of the epineurium. Masson's trichrome and immunostaining results affirmed an elevated expression of α-smooth muscle actin (α-SMA) in the corpus cavernosum (CC). Ultrastructure findings revealed that PRP effectively rejuvenated degenerating nerves, preserved endothelium and adherent junctions of corporal smooth muscle, and restored the axonal scaffolds by upregulating neurofilament-H (NF-H) expression. Finally, PRP enhanced neural stability by enhancing the axonal remyelination processes in aged-ED rats. Hence, PRP treatment was proven to restore EF in aged-ED rats, which was considered a safe, novel, cost-effective, and hassle-free strategy for EF restoration in geriatric patients.

Impact of prostatic radiation therapy on bladder contractility and innervation

AIMS

To determine the effect of prostatic radiation therapy (RT) on bladder contractility and morphology, and axon, or neuron profiles within the detrusor and major pelvic ganglia (MPG) in male rats.

METHODS

Male Sprague-Dawley rats (8 weeks) received a single dose of prostatic RT (0 or 22 Gy). Bladders and MPG were collected 2- and 10-weeks post-RT. Detrusor contractile responses to carbachol and electrical field stimulation (EFS) were measured. Bladders were stained with Masson's trichrome, and antibodies for nonspecific neuronal marker, cholinergic nerve marker choline acetyltransferase (ChAT), and alpha-smooth muscle actin. MPG gene expression was assessed by quantitative polymerase chain reaction for ubiquitin carboxy-terminal hydrolase L1 (Uchl1) and Chat.

RESULTS

At 2 weeks post-RT, bladder smooth muscle, detrusor cholinergic axon profiles, and MPG Chat gene expression were increased (p < .05), while carbachol and EFS-mediated contractions were decreased (p < .05). In contrast, at 10 weeks post-RT, nerve-mediated contractions were increased compared with control (p < .05), while bladder smooth muscle, detrusor cholinergic axon profiles, MPG Chat expression, and carbachol contractions had normalized. At both 2- and 10-weeks post-RT, there was no change in detrusor nonspecific axon profiles and MPG Uchl1 expression.

CONCLUSION

In a rat model, RT of the prostate and MPG was associated with early changes in MPG Chat gene expression, and bladder cholinergic axon profiles and smooth muscle content which resolved over time. After RT recovery, bladder contractility decreased early and increased by 10 weeks. Long-term changes to the MPG and increased bladder cholinergic axons may contribute to RT-induced bladder dysfunction in prostate cancer survivors.

Swallowing dysfunction following radiation to the rat mylohyoid muscle is associated with sensory neuron injury

Radiation-based treatments for oropharyngeal and hypopharyngeal cancers result in impairments in swallowing mobility, but the mechanisms behind the dysfunction are not clear. The purpose of this study was to determine if we could establish an animal model of radiation-induced dysphagia in which mechanisms could be examined. We hypothesized that 1) radiation focused at the depth of the mylohyoid muscle would alter normal bolus transport and bolus size and 2) radiation to the mylohyoid muscle will induce an injury/stress-like response in trigeminal sensory neurons whose input might modulate swallow. Rats were exposed to 48 or 64 Gy of radiation to the mylohyoid given 8 Gy in 6 or 8 fractions. Swallowing function was evaluated by videofluoroscopy 2 and 4 wk following treatment. Neuronal injury/stress was analyzed in trigeminal ganglion by assessing activating transcription factor (ATF)3 and GAP-43 mRNAs at 2, 4, and 8 wk post treatment. Irradiated rats exhibited decreases in bolus movement through the pharynx and alterations in bolus clearance. In addition, ATF3 and GAP-43 mRNAs were upregulated in trigeminal ganglion in irradiated rats, suggesting that radiation to mylohyoid muscle induced an injury/stress response in neurons with cell bodies that are remote from the irradiated tissue. These results suggest that radiation-induced dysphagia can be assessed in the rat and radiation induces injury/stress-like responses in sensory neurons.NEW & NOTEWORTHY Radiation-based treatments for head and neck cancer can cause significant impairments in swallowing mobility. This study provides new evidence supporting the possibility of a neural contribution to the mechanisms of swallowing dysfunction in postradiation dysphagia. Our data demonstrated that radiation to the mylohyoid muscle, which induces functional deficits in swallowing, also provokes an injury/stress-like response in the ganglion, innervating the irradiated muscle.

Biology of iatrogenic sexual dysfunction in men and women survivors of cancer

Sexual dysfunction (SD) is widely reported by cancer survivors. However, this is an issue underestimated by doctors and the contribution of anticancer therapies for the development of SD in cancer survivors is understudied and poorly understood. Sexual function involves the activation of a neurovascular system that leads to penile erection in males and clitoral engorgement in females. Anticancer therapies can cause damage to the neurovascular circuit responsible for normal sexual function and thus, individual or combined therapies could play a role in the development of SD in all types of cancer survivors and not only those affected by genital cancers. In this review, the pathophysiology of SD and possible mechanisms underlying SD induced by anticancer therapies will be discussed. The effects of chemotherapy, radiotherapy and surgical interventions on the vasculature and nerves as well as their effects on sex hormones and inflammatory processes could link the biological effects of these interventions with SD. In conclusion, this review reports evidence that, despite psychological aspects and the disease itself, anticancer therapies are able to induce direct and indirect effects in males and females that could lead to SD in cancer survivors even after the end of the treatment.

RhoA/ROCK pathway inhibitor ameliorates erectile dysfunction induced by radiation therapy in rats

OBJECTIVES

Prostate cancer (PCa) treatment with radiation therapy (RT) has an excellent cure rate. However, Radiation-induced Erectile Dysfunction (RiED) is a common and irreversible toxicity impacting quality of life, and there is no FDA approved specific drug for RiED. We previously showed that prostate RT increased RhoA/ROCK signaling in the cavernous nerve (CN) and penile tissues, which may lead to RiED in rats. In this study, we investigated whether RhoA/ROCK pathway inhibition by a specific inhibitor called Hydroxyfasudil (HF) can improve RiED in our well-established rat model.

MATERIALS/METHODS

Male Sprague-Dawley rats were randomized to the following groups: sham-RT, HF-only, RT-only, and RT + HF. Rats were either exposed to a single dose of 25 Gy prostate-confined RT or a sham procedure. 10 mg/kg HF or normal saline was injected intraperitoneally. Erectile function was evaluated by intracavernosal pressure (ICP) and mean arterial pressure (MAP) measurements at week 14 post-RT. Cavernous nerve (CN) injury was evaluated by transmission electron microscopy (TEM), and penile tissue fibrosis by Masson trichrome staining (MT).

RESULTS

We have found that the HF treatment prior to RT showed significant (p < 0.001) improvement in ICP/MAP ratio, area under the curve, and maximum ICP value, compared to RT-alone rats. Furthermore, RT + HF treated rats exhibited increased CN myelination and decreased axonal atrophy, comparted to RT-only. HF treatment showed significantly decreased penile tissue fibrosis (p < 0.05) compared to RT-alone treated rats.

CONCLUSION

Our results provide the first preclinical evidence that targeting RhoA/ROCK pathway by HF may provide a novel therapeutic option for the treatment of RiED.

Prostatic irradiation-induced sexual dysfunction: A review and multidisciplinary guide to management in the radical radiotherapy era (Part II on Urological Management)

Prostate cancer is the most common malignancy in men and the second leading cause of cancer-related death in men. Radiotherapy is a curative option that is administered via external beam radiation, brachytherapy, or in combination. Sexual dysfunction is a common toxicity following radiotherapy, similar to men undergoing radical prostatectomy, but the etiology is different. The pathophysiology of radiation-induced sexual dysfunction is multi-factorial, and the toxicity is a major cause of impaired quality of life among long-term prostate cancer survivors. Management of a patient's sexual function during and after radiotherapy requires multidisciplinary coordination of care between radiation oncology, urology, psychiatry, pharmacy, and dermatology. This review provides a framework for clinicians to better understand prostatic radiotherapy-induced sexual dysfunction diagnosis, evaluation, and a patient-centered approach to toxicity preventive strategies and management.

Prostatic irradiation-induced sexual dysfunction: a review and multidisciplinary guide to management in the radical radiotherapy era (Part I defining the organ at risk for sexual toxicities)

Prostate cancer is the most common malignancy and the second leading cause of cancer-related death in men. Radiotherapy is a curative option that is administered via external beam radiation, brachytherapy, or in combination. Erectile, ejaculatory and orgasm dysfunction(s) is/are known potential and common toxicities associated with prostate radiotherapy. Our multidisciplinary team of physicians and/or scientists have written a three (3) part comprehensive review of the pathogenesis and management radiation-induced sexual dysfunction. Part I reviews pertinent anatomy associated with normal sexual function and then considers the pathogenesis of prostate radiation-induced sexual toxicities. Next, our team considers the associated radiobiological (including the effects of time, dose and fractionation) and physical (treatment planning and defining a novel Organ at Risk (OAR)) components that should be minded in the context of safe radiation treatment planning. The authors identify an OAR (i.e., the prostatic plexus) and provide suggestions on how to minimize injury to said OAR during the radiation treatment planning process.

Chronic administration of LIMK2 inhibitors alleviates cavernosal veno-occlusive dysfunction through suppression of cavernosal fibrosis in a rat model of erectile dysfunction after cavernosal nerve injury

We evaluated whether chronic administration of LIMK2-inhibitors could improve erectile function by alleviating CVOD through suppressing cavernosal fibrosis in a rat model of cavernosal nerve crush-injury (CNCI). Forty-two 12-week-old rats were equally categorized into the three groups: sham-surgery (S), CNCI (I), and CNCI treated with LIMK2-inhibitors (L). The L-group was treated with daily intraperitoneal injection of LIMK2-inhibitors (10.0 mg/kg) for 30-days after surgery. Erectile function was assessed using dynamic-infusion-cavernosometry (DIC). Penile tissue was processed for Masson’s-trichrome staining, Western-blotting, and double immunofluorescence. The I-group showed significantly higher maintenance and drop rates as well as lower papaverine response, compared to the S-group. Chronic inhibition of LIMK2 in the L-group significantly improved the DIC parameters compared to those in the I-group, although the parameters were not completely restored to normal control values. Also, the I-group showed a reduced smooth muscle (SM)-to-collagen ratio, decreased immunohistochemical staining for α-SM-actin, increased number of fibroblasts positive for phosphorylated Cofilin, increased LIMK2/Cofilin phosphorylation and increased protein expression of Collagen-1 or Fibronectin, compared to the S-group. The L-group showed significant improvements in SM/collagen ratio and the deposition of Collagen-1 or Fibronectin compared to the I-group, although not completely normalized. According to the densitometry and confocal microscopy results, the L-group showed restoration of LIMK2/Cofilin phosphorylation and amount of fibroblasts positive for phosphorylated Cofilin to the normal control value. In conclusion, chronic inhibition of LIMK2 can improve CVOD and ED by alleviating cavernosal fibrosis via normalizing the LIMK2/Cofilin pathway.

Clarifying the Relative Impacts of Vascular and Nerve Injury That Culminate in Erectile Dysfunction in a Pilot Study Using a Rat Model of Prostate Irradiation and a Thrombopoietin Mimetic

PURPOSE

Radiation therapy (RT) offers an important and curative approach to treating prostate cancer, but it is associated with a high incidence of erectile dysfunction (ED). It is not clear whether the etiology of radiation-induced ED (RI-ED) is driven by RT-mediated injury to the vasculature, the nerves, or both. This pilot study sought to distinguish the effects of vascular and nerve injury in RI-ED by applying a vascular radioprotectant in a rat model of prostate RT.

METHODS

A single dose of the thrombopoietin mimetic (TPOm; RWJ-800088), previously shown to mitigate radiation-induced vascular injury, was administered 10 minutes after single-fraction conformal prostate RT. Nine weeks after RT, rats were assessed for erectile and arterial function. Nerve markers were quantified with reverse transcriptase polymerase chain reaction. Immunofluorescent microscopy further characterized vascular effects of RT and TPOm.

RESULTS

Sham animals and animals that received RT and TPOm showed significant arterial vasodilation in response to systemic hydralazine (24.1% ± 7.3% increase; P = .03 in paired t test). However, animals that received RT and vehicle were unable to mount a vasodilatory response (-7.4% ± 9.9% increase; P = .44 in paired t test). TPOm prevented RT-induced change in the penile artery cross-sectional area (P = .036), but it did not ameliorate cavernous nerve injury as evaluated by gene expression of neuronal injury markers. Despite significant structural and functional vascular protective effects and some trends for differences in nerve injury/recovery markers, TPOm did not prevent RI-ED at 9 weeks, as assessed by intracavernous pressure monitoring after cavernous nerve stimulation.

CONCLUSIONS

These data suggest that vascular protection alone is not sufficient to prevent RI-ED and that cavernous nerve injury plays a key role in RI-ED. Further research is required to delineate the multifactorial nature of RI-ED and to determine if TPOm with modified dosing regimens can mitigate against nerve injury either through direct or vascular protective effects.

Resveratrol treatment may preserve the erectile function after radiotherapy by restoring antioxidant defence mechanisms, SIRT1 and NOS protein expressions

Radiotherapy (RT) for prostate cancer (PC) can cause erectile dysfunction (ED) by damaging neurovascular structures with oxidative stress. In this study, we evaluated the effects of resveratrol, an antioxidant, on post-RT ED. Fifty rats in five groups were evaluated; control (C), prostate-confined radiotherapy with short- and long-term vehicle or resveratrol treatment. Cavernosal tissues were obtained to analyze glutathione (GSH), nitric oxide (NO), cyclic guanosine monophosphate (cGMP), 8-hydroxy-2'-deoxy-guanosine (8-OHdG) levels and superoxide dismutase (SOD), caspase-3 activities, sirtuin-1, Foxo-3, nNOS, and eNOS protein expressions. Intracavernosal pressures (ICP) were measured for the long-term treatment group. In the RT + long-term vehicle treatment group, tissue GSH, NO, cGMP, and SOD activity were decreased while 8-OHdg levels and caspase-3 activities were increased. Radiotherapy caused a decrease in sirtuin-1, nNOS, and eNOS protein expressions. These parameters were reversed by resveratrol treatment. Foxo-3 protein expressions were unaltered in the RT + short-term vehicle treatment group and started to increase as a defense mechanism in the RT + long-term vehicle group; however, resveratrol treatment caused a significant increase in Foxo-3 expressions. Resveratrol preserved the metabolic pathways involved in erectile function and provided functional protection. Resveratrol can be used as a supplementary agent in patients undergoing radiotherapy to preserve erectile function.