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Have you read? Best of the Best. Basic Science.

Nuno Louro
Urology Department of Centro Hospitalar e Universitário do Porto (CHUP), University of Porto (ICBAS-UP)
Porto, Portugal

Female Sexual Dysfunction

Harroche J, Urban-Maldonado M, Thi MM, Suadicani SO. Mechanosensitive Vaginal Epithelial Adenosine Triphosphate Release and Pannexin 1 Channels in Healthy, in Type 1 Diabetic, and in Surgically Castrated Female Mice. J Sex Med 2020. 17: 870-880.

Although the mechanosensitivity of the female genital organs and its importance for proper perception and response to penetrative sexual stimulation have been well recognized, the exact mechanisms and molecular mediators involved in this response are still poorly understood. It has been proposed that adenosine triphosphate (ATP) and its purinoceptors are involved in the mechanisms of mechanosensory transduction in the vagina, such as has already been reported for the bladder and ureters. This study aimed to investigate if intravaginal mechanical stimulation would trigger vaginal ATP release and if this response would involve Pannexin 1 (Panx1) channels and be altered in animal models of type 1 diabetes (T1D) and menopause. The authors used diabetic Akita female mice as a T1D model and surgical castration (OVX) as a menopause model. Panx1-null mice were used to evaluate Panx1 participation in mechanosensitive vaginal ATP release. Vaginal washes were collected from anesthetized mice at baseline and 5 minutes after intravaginal stimulation. ATP levels in vaginal washes were measured using the luciferin-luciferase assay. Panx1 mRNA levels in vaginal epithelium were quantified by quantitative polymerase chain reaction. The authors found that ATP released after intravaginal mechanical stimulation was 84% lower in Panx1-null and 76% lower in diabetic mice compared with controls and was reduced in a progressive and significant manner in OVX mice when compared with Sham. They also found that Panx1 mRNA expression in vaginal epithelium was 44% lower in diabetics than in controls and 40% lower in OVX than in Sham group. These findings led the authors to conclude that Panx1 downregulation and consequent attenuation of mechanosensitive vaginal responses may be implicated in mechanisms of female genital arousal disorder, thereby providing potential targets for novel therapies to manage this condition.

Erectile Dysfunction

Sevilleja-Ortiz A, El Assar M, García-Rojo E, et al. Enhanced Contribution of Orai Channels to Contractility of Human Penile Smooth Muscle in Erectile Dysfunction. J Sex Med; 2020. 17: 881-891

Despite the efficacy of type 5 phosphodiesterase inhibitors (iPDE5) in the treatment of ED, a significant proportion of patients is resistant to this treatment and this continues to lead the search for alternative pharmacologic strategies. It is well known that intracellular calcium levels regulate a large number of processes in the cell and that there are several different mechanisms to control the ability of the cell to increase or reduce its calcium levels. Store-operated calcium entry (SOCE) and its key players, stromal interaction molecule (STIM) and Orai calcium channels have been proposed as emergent therapeutic targets in cardiovascular pathophysiology. Taken this in account, the authors aimed to evaluate the contribution of STIM/Orai to human penile tissue contraction and to analyze the influence of ED on STIM/Orai signalling at functional and expression levels in human penile vascular tissues. They dissected human penile resistance arteries (HPRA) and human corpus cavernosum (HCC) from cavernosal specimens from 30 organ donors without history of ED (No ED) and from 48 patients with ED undergoing penile prosthesis insertion and functionally evaluated them in wire myographs and organ chambers, respectively. Expression of STIM-1, Orai1, and Orai3 in HCC was localized and quantified by immunofluorescence. They found that inhibition of Orai channels significantly reduced norepinephrine induced contractions in both HCC and HPRA from either No ED or ED subjects, but the effects were more marked in ED. Thromboxane-induced contractions were reduced and neurogenic contractile and relaxant responses modulated by Orai inhibition in penile tissues from patients with ED. In fact, addition of YM-58483 (Orai channels inhibitor) concentration dependently relaxed precontracted HPRA and HCC. These relaxations were significantly more pronounced in tissues from patients with ED. All HCC specimens displayed expression of STIM-1, Orai1, and Orai3. Significantly increased expression of Orai1 and Orai3 but not STIM-1 was observed in patients with ED. The authors concluded that the STIM/Orai signaling system is functionally enhanced in the HCC and penile arteries from men with ED contributing to hypercontractility that could hamper the adequate process of erection.  Although a causal relationship could not be assured, functional hyperactivity of the STIM/Orai system could be related to increased expression of Orai 1 and Orai 3 channels in penile tissue from men with ED, allowing the authors to suggest  STIM/Orai signaling inhibition as a potential therapeutic target in the future management of ED.

Gu X, Thakker PU, Matz EL, et al. Dynamic Changes in Erectile Function and Histological Architecture After Intracorporal Injection of Human Placental Stem Cells in a Pelvic Neurovascular Injury Rat Model. J Sex Med. 2020; 17; 400-411

Although use of nerve-sparing techniques is often described, rates of post-Radical Prostatectomy (RP) erectile dysfunction (ED) are reportedly as high as 90%, likely due, in part, to periprostatic and cavernous nerve (CN) damage. Clinical interventions have traditionally been limited to managing the chronic form of ED with phosphodiesterase-5 inhibitors, intracavernosal injections, vacuum devices, and penile prostheses. The human placenta provides a bountiful and noncontroversial source of stem cells which have the potential for regeneration of injured tissue. In this study the authors aimed to determine the effect of human placenta derived stem cells on erectile function recovery and histological changes at various time points in a cavernous nerve injury rat model and to study the fate of injected stem cells throughout the regenerative process. Human placental stem cells (PSCs) were dual labeled with monomeric Katushka far red fluorescent protein (mKATE)-renLUC using a lentivirus vector. A pelvic neurovascular injury induced erectile dysfunction model was established in male, athymic rats by crushing the cavernous nerves and ligating the internal pudendal neurovascular bundles, bilaterally. At the time of defect creation, nonlabeled PSCs were injected into the corpus cavernosum. The phosphate-buffered saline treated group served as the negative control group, and age-matched rats (age-matched controls) were used as the control group. Erectile function, histomorphological analyses, and Western blot were assessed at 1, 6, and 12 weeks after model creation. The distribution of implanted, dual-labeled PSCs was monitored using an in vivo imaging system (IVIS) and implanted cells were further tracked by detection of mKATE fluorescence in histological sections. They found that the ratio of intracavernous pressure to mean arterial pressure significantly increased in PSC-injected rats compared with phosphate-buffered saline controls (P < 0.05) at the 6- and 12-week time points, reaching 72% and 68%of the age-matched control group, respectively. Immunofluorescence staining and Western blot analysis showed significant increases in markers of neurons (84.3%), endothelial cells (70.2%), and smooth muscle cells (70.3%) by 6 weeks in treatment groups compared with negative controls. These results were maintained through 12 weeks. IVIS analysis showed luminescence of implanted PSCs in the injected corpora immediately after injection and migration of cells to the sites of injury, including the incision site and periprostatic vasculature by day 1. mKATE fluorescence data revealed the presence of PSCs in the penile corpora and major pelvic ganglion at 1 and 3 days postoperatively. At 7 days, immunofluorescence of penile PSCs had disappeared and was diminished in the major pelvic ganglion. The authors concluded that placenta-derived stem cells may represent a future treatment to mitigate against development of erectile dysfunction after radical prostatectomy or other forms of pelvic injury.

Premature Ejaculation

Zhang QJ, Yang BB, Yang J, et al. Inhibitory Role of Gamma-Aminobutyric Receptors in Paraventricular Nucleus on Ejaculatory Responses in Rats. J Sex Med. 2020; 17: 614-622

Ejaculation is regulated by complex neurophysiological mechanisms. More and more attention has been paid to the role of Sympathetic Nervous System (SNS) activity in the pathogenesis of ejaculation disorders. The paraventricular hypothalamic nucleus (PVN) is not only involved in controlling ejaculation reflexes but also an important region for the generation and integration of SNS activity. It is known that γ-aminobutyric acid (GABA) in the PVN inhibits sympathetic outflow and both GABA-A receptors and GABA-B receptors are involved in this action. Several studies have indicated that GABAergic neurotransmission is related to inhibitory processes involved in male sexual behaviour but no previous studies have explored the correlation between GABA receptors in the PVN and ejaculatory behaviour. The authors aimed to investigate whether differences in ejaculatory behaviour of rats were associated with the state of SNS activity and GABA receptor expressions in the PVN of the hypothalamus and the effects of GABA receptors in the PVN on ejaculatory behaviour. They used Sprague-Dawley rats divided, based on ejaculatory performance, into “sluggish,” “normal,” and “rapid” ejaculators. PVN microinjection was performed to evaluate the role of GABA receptors on sexual behaviour. Compared with “normal” rats, the “rapid” group ejaculated more times with shorter latency and had lower expression and distribution of both GABA-A and GABA-B receptors, while the opposed results appeared in the “sluggish” group. The norepinephrine level was successively increased among “sluggish”, “normal” and “rapid” rats and correlated with ejaculation frequency and ejaculation latency. In addition, bilateral microinjection of the GABA-A and GABA-B receptor agonist (isoguvacine and baclofen) into the PVN both significantly prolonged the intromission latency and inhibited ejaculation, which could be blocked by antagonist gabazine and CGP-35348, respectively. Vigabatrin, the GABA transaminase inhibitor, caused a significantly reduced ejaculation frequency and extended ejaculation latency in rats, which could be offset by simultaneous injections of gabazine and CGP-35348. The authors concluded that ejaculation behaviours in male rats are associated with SNS activity and could be regulated by GABA receptors in the PVN, which may be of assistance in the treatment of ejaculation disorders in the future.

Peyronie’s Disease

Antoniassi T, Fácio Jr FN, Spessoto LCF, et al. Anti-fibrotic Effect of Mycophenolate Mofetil on Peyronie0s Disease Experimentally Induced with TGF-β. Int J Impot Res. 2020. 32: 201-206

Peyronie’s disease (PD) is defined as acquired fibrosis of the tunica albuginea, which can result in a curved penis with pain and/or erectile dysfunction. Besides the proliferation of fibroblasts and changes in the structure of elastin, a fibrous plaque occurs with PD that contains excessive amounts of collagen. Mycophenolate mofetil (MMF) is an immunosuppressant drug used to prevent the rejection of transplanted organs and has demonstrated some effectiveness in the prevention of fibrosis in autoimmune diseases. MMF diminishes collagen synthesis and fibroblast activity. As transforming growth factor-β (TGF-β) plays an important role in the production of collagen by fibroblasts, the reduction in fibroblasts by MMF could assist in the interruption of the fibrotic process in PD. The aim this study was to evaluate the histological, histochemical, and stereological changes caused by MMF on the tunica albuginea of rat penises submitted to an injection of TGF-β for the induction of PD. The authors used twenty adult male Wistar rats and divided them into four groups: Control group; TGF-β group (TGF-β injection); MMF-7d group (treated with MMF 7 days after induction with TGF-β); and MMF-30d group (treated with MMF 30 days after induction with TGF-β). The steorological evaluation included the relative volume of different types of connective fibres of the tunica albuginea. The histochemical analysis revealed the fragmentation and degradation of elastin in the tunica albuginea. This process was partially reversed in the MMF-7d group and a situation very close to normality was observed in the MMF-30d group. In the collagen III/collagen I ratio it was observed increase in this ratio in the TGF-β (59.4 ± 5.53) and MMF-7d (49 ± 18.2) groups and a decrease in the MMF-30d group (28.7 ± 4), approaching normality. The authors concluded that the injection of TGF-β promoted fibrotic alterations in the penile tunica albuginea in Wistar rats corresponding to PD and that MMF acted as a regenerating anti-fibrotic agent.

Hakim L, Fiorenzo S, Hedlund P, et al. Intratunical Injection of Autologous Adipose Stromal Vascular Fraction Reduces Collagen III Expression in a Rat Model of Chronic Penile Fibrosis. Int J Impot Res. 2020; 32: 281-288

Fibrosis is defined by an excessive accumulation of extracellular connective tissue proteins (extracellular matrix (ECM)) such as collagen, elastin and fibronectin. Typically, ECM aggregation is an indispensable and reversible phase of the wound healing process. It can, however, progress into long-lasting fibrotic response if the wound healing process itself becomes deregulated. Fibrosis represents the final, usual pathological result of many chronic inflammatory conditions. Peyronie’s Disease (PD) is an acquired fibrotic disorder involving the tunica albuginea (TA) of the penis. Previous studies have shown that the injection of adipose stem cells and stromal vascular fraction (SVF) into the TA during the inflammatory phase in a rat model of PD prevented the development of TA fibrosis. The aim of this study was to investigate whether local injection of SVF could reduce established fibrosis in a rat model of chronic phase of PD. Eighteen-male 12-wk-old Sprague-Dawley rats were divided in three equal groups: sham, PD without treatment (PD) and PD treated with SVF(PD-SVF). Sham rats underwent 2 injections of vehicle into the TA one month apart. PD rats underwent TGF-β1 injection and injection of vehicle one month later. PD-SVF rats underwent TGF-β1 injection followed by SVF (1-million cells) one month later. One month after the last treatment, the animals, n = 6 rats per group, underwent measurement of intracorporal and mean arterial pressure during electrostimulation of the cavernous nerve. Following euthanasia, penises were harvested for in-vitro study. They found that erectile function was not statistically significantly different between groups. They also found that PD animals developed subtunical areas of fibrosis and elastosis with upregulation of collagen III protein. These fibrotic changes were reversed after injection of SVF so the authors concluded that local injection of SVF reverses TA fibrosis in a rat model of chronic phase of PD.

Priapism

Cinar O, Bolat MS, Erdem S, et al. The Effect of an Antifibrotic Agent, Pirfenidone, on Penile Erectile Function in an Exerimental Rat Model of Ischemic Priapism. Int J Impot Res. 2020. 32: 232-238

Erectile dysfunction (ED) is a well known complication of ischemic priapism (IP) and, to date, no effective medical approach for this condition has been described. The aim of the authors in this study was to evaluate the anti inflammatory, antifibrotic, and antioxidant effects of pirfenidone (PFD) on cavernosal tissue in a rat model of IP. Forty-eight male albino rats were randomized into four groups (n=12 in each group): no IP (group 1); IP for 1 h, followed by intracavernosal pressure (ICP) measurements using electrical cavernous nerve stimulation (CNS) (group 2); IP for 1 h, followed by ICP measurements using electrical CNS 6 weeks later (group 3); and IP for 1 h, oral PFD (30mg/kg once daily) treatment by oral gavage, followed by ICP measurements using electrical CNS 6 weeks later (group 4). Malondialdehyde (MDA) and reduced glutathione levels were measured spectrophotometrically and in a histological evaluation, cavernosal collagen/smooth muscle ratios were calculated. They found that the intracavernosal pressure values of group 1 were higher than those of groups 2 and 3 but similar to those of group 4. The mean MDA level was significantly higher in group 3, as compared with that in group 4. The mean collagen/smooth muscle ratio in groups 1–4 was 24%, 42%, 65%, and 48%, respectively. They concluded that PFD reduced cavernosal fibrotic activity and improved erectile function in this rat model of IP and suggested that PFD may represent a new treatment option in IP approach.

Anatomy & Physiology

Allen K, Wise N, Frangos E and Komisurak B. Male Urogenital System Mapped Onto the Sensory Cortex: Functional Magnetic Resonance Imaging Evidence. J Sex Med. 2020. 17: 603-613

Since the projection of the human male urogenital system onto the paracentral lobule has not previously been mapped comprehensively, the authors aimed to map specific urogenital structures onto the primary somatosensory cortex toward a better understanding of sexual response in men. They used functional magnetic resonance imaging to map primary somatosensory cortical responses to self-stimulation of the penis shaft, glans, testicles, scrotum, rectum, urethra, prostate, perineum, and nipple. They further compared neural response with erotic and prosaic touch of the penile shaft.

The authors identified the primary mapping site of urogenital structures on the paracentral lobule and identified networks involved in perceiving touch as erotic. They concluded that this study offers a comprehensive mapping of male genital components to the paracentral lobule and that they have provided evidence of differential projection of light touch vs pressure applied to the penile shaft, suggesting differential innervation of its superficial, vs deep structure.

Similar to the response in women, they found nipple projection to genital areas of the paracentral lobule. They also provided evidence of differential representation of erotic and nonerotic genital self-stimulation, the former activating sensory networks other than the primary sensory cortex, indicating a role of top-down activity in erotic response. These findings help to identify key neural areas that respond to urogenital self-stimulation in men, and areas responsible for “erotic” arousal which may provide potential target areas for treatment of urogenital and sexual arousal disorders in men.

Covid-19

Pan F, Xiao X, Guo J, et al. Noe Evidence of Severe Acute Respiratory Syndrome – Coronavirus 2 in Semen of Males Recovering from Coronavirus Disease 2019. Fertil Steril. 2020. 113: 1135-1139

Although viral transmission occurs predominantly through respiratory droplets, severe acute respiratory syndrome (SARS)–coronavirus 2 (CoV-2) has been isolated in blood samples and faeces from patients with coronavirus disease 2019  (COVID-19), raising questions about viral shedding in other bodily fluids, including semen, as well as alternative modes of transmission. In this study the authors aimed to describe SARS CoV-2 in seminal fluid of patients recovering from COVID-19 and to describe the expression profile of angiotensin-converting enzyme 2 (ACE2) and Transmembrane Serine Protease 2 (TMPRSS2) within the testicle. They studied 34 adult Chinese males diagnosed with COVID-19 through confirmatory quantitative reverse transcriptase–polymerase chain reaction (qRT-PCR) from pharyngeal swab samples.

The authors found that 6 patients (19%) demonstrated scrotal discomfort suggestive of viral orchitis around the time of COVID-19 confirmation. SARS–CoV-2 was not detected in semen after a median of 31 days from COVID-19 diagnosis. Single-cell transcriptome analysis demonstrated sparse expression of ACE2 and TMPRSS2, with almost no overlapping gene expression. These results are reassuring regarding possible viral transmission through semen although the fact that these men were not in the peak of acute infection and only had mild symptoms could raise the question as if the sames results would have been found at earlier time points or higher viral loads as pointed by Michael Eisenberg in the same issue.

Li D, Jin M, Bao P, et al. Clinical Characteristics and Results of Semen Tests Among Men With Coronavirus Disease 2019. JAMA Netw Open. 2020; 3: e208292.

In this study the authors enrolled a total of 38 patients for semen testing. Of these 38 participants who provided a semen specimen, 23 participants (60.5%) had achieved clinical recovery and 15 participants (39.5%) were at the acute stage of infection. Results of semen testing found that 6 patients (15.8%) had results positive for SARS-CoV-2, including 4 of 15 patients (26.7%) who were at the acute stage of infection and 2 of 23 patients (8.7%) who were recovering, but there was no significant difference between negative and positive test results for patients by age, urogenital disease history, days since onset, days since hospitalization, or days since clinical recovery. The authors conclude that, if it could be proved that SARS-CoV-2 can be transmitted sexually in future, larger studies, sexual transmission might be a critical part of the prevention of transmission, especially considering the fact that SARS-CoV-2 was detected in the semen of recovering patients. Abstinence or condom use might be considered as preventive means for these patients. These findings also alert for the need to conduct studies monitoring fetal development.

Ma L, Xie W, Li D, et al. Effect of SARS-CoV2 Infection Upon Male Gonadal Function: A Single Center Based Study. medRxiv. 2020. 2020. 2003.2021.20037267

ACE2, the receptor for entry into the target cells by SARS-CoV-2, was found to abundantly express in testes, including spermatogonia, Leydig and Sertoli cells. However, there is no clinical evidence about whether SARS-CoV-2 infection can affect male gonadal function so far. In this study, the authors compared the sex-related hormones between 81 reproductive-aged men with SARS-CoV-2 infection and 100 age-matched healthy men, and found that serum luteinizing hormone (LH) was significantly increased, but the ratio of testosterone (T) to LH and the ratio of follicle stimulating hormone (FSH) to LH were dramatically decreased in males with COVID-19. Besides, multivariable regression analysis indicated that c-reactive protein (CRP) level was significantly associated with serum T:LH ratio in COVID-19 patients. They concluded that this study provided the first direct evidence about the influence of medical condition of COVID-19 on male sex hormones, alerting more attention to gonadal function evaluation among patients recovered from SARSCoV-2 infection, especially the reproductive-aged men.

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