Histological and functional aspects of different regions of the rabbit vagina

Characterization of giant neuroendocrine cells in the pregnant New Zealand white rabbit vagina demonstrated by histological, histochemical, and immunohistochemical methods

The vagina is part of the genitalia and constitutes part of the birth canal. Sperm is deposited into vagina, and it acts in transport of sperm. Pregnancy is a complex process involving different physiological changes in the body associated with hormonal and metabolic alterations that control maternal and fetal demands. During pregnancy, neuroendocrine cells in rabbit vagina are considered part of the diffuse neuroendocrine system observed throughout the body. Giant neuroendocrine cells in rabbit vagina during pregnancy have not been observed previously. This study detected the presence of giant neuroendocrine cells in the vagina of the pregnant rabbit. The presence of these cells was demonstrated with the use of different histological techniques, including hematoxylin and eosin, PAS, combined Alcian blue-PAS, Crossmon's trichrome, and the Grimelius silver method. Giant neuroendocrine cells were observed in late-pregnancy intraepithelial sites and on the lamina propria. These cells were characterized by vacuolated basophilic cytoplasm with PAS- and PAS-AB-positive granules. Moreover, neuroendocrine cells exhibited an argyrophilic character. Immunohistochemically, neuroendocrine cells in rabbit vagina during pregnancy demonstrated positive immunoreactivity to neuron-specific enolase (NSE) with different intensities, mild immunoreactivity to the vascular endothelial growth factor (VEGF), and negative immunoreactivity to CD68.

Establishment of Rat Model of Female Genital Sexual Arousal Disorder

Introduction

Female Genital Sexual Arousal Disorder (FGSAD) seriously affects women's quality of life and Sexual life, but it still lacks ideal FGSAD animal models for further study.

Aim

To establish a specific model of female genital sexual arousal disorder and explore the mechanisms resulting in FGSAD.

Methods

After delivery, female rats were guided by expansions of the vagina and ovariectomy (VD+OVX, n = 10); in VD group female rats were just extended by the vagina (VD, n = 10), in OVX group female rats were treated with ovariectomy (OVX, n = 10);the remaining had 1 longitudinal incision as sham group(n = 10).

Outcomes

Vaginal dilatation combined with ovariectomy in rats may reflect female genital sexual arousal disorder with high reproducibility and stability.

Results

Vaginal tissue of female rats in OVX group and VD+OVX group showed an increase in blood flow, decrease in muscle content compared to the sham group. The proportion of collagen fiber I/III decreased and the elastic fiber showed significant rupture and fragmentation; Structural reticular integrity was also significantly separated and broken from the muscle fibers. However, there was no significant difference in vaginal blood flow, fibers and vascular between VD group and Sham group. The damage of vaginal tissue in VD+OVX group was more significant than that in OVX and VD groups.

Clinical Translation

We have constructed a specific animal model that can provide clinical insights into the mechanism of FGSAD and serves as a good avenue for further research of its treatment.

Strengths and Limitations

Vaginal dilatation combined with ovariectomy in rats is a specific animal model with high reproducibility and stability, but we do acknowledge the shortcomings and limitation present in our study. Since genital arousal disorder has many different etiologies that impact the vagina, the clitoris and surrounding tissues, there is no “gold standard” model that different models attempt to investigate different etiologies.

Conclusion

The female genital sexual arousal disorder model established by vaginal dilatation combined with ovariectomy is a novel rat model with simple induction conditions, which pathogenic mechanism of female genital sexual arousal disorders maybe connected with the change of VEGF and MMP-9 in vaginal fibromuscular system and microvascular.

Li G, Yu P, Hu Y, et al. Establishment of Rat Model of Female Genital Sexual Arousal Disorder. Sex Med 2022;10:100530.

Smooth Muscle Organization and Nerves in the Rat Vagina: A First Look Using Tissue Clearing and Immunolabeling

Smooth muscle fibers within the vagina, as well as the nerve fibers that contribute to their control mechanisms, are important for the maintenance and alteration of vaginal length and tone. Vaginal smooth muscle (VaSM) is typically described as being arranged into two distinct concentric layers: an inner circular muscular layer and an outer longitudinal muscular layer. However, the distribution of VaSM oriented in the longitudinal direction (LD) and circumferential direction (CD) has never been quantified. In this study, tissue clearing and immunohistochemistry were performed so that the VaSM, and surrounding nerves, within whole rat vaginas ([Formula: see text]) could be imaged without tissue sectioning, preserving the three-dimensional architecture of the organs. Using these methods, the vagina was viewed through the full thickness of the muscularis layer, from the distal to the proximal regions. The VaSM orientation in the proximal and distal regions and the VaSM content along the LD and CD were quantified. Additionally, a qualitative assessment of vaginal nerves was performed. When compared using a permuted version of the Watson [Formula: see text] test, the orientation of VaSM in the proximal and distal regions were found to be significantly different in 4 of the 6 imaged rat vaginas ([Formula: see text]). While the distal vagina contained a similar amount of VaSM oriented within [Formula: see text] of the LD and within [Formula: see text] of the CD, the proximal vagina contained significantly more VaSM oriented towards the LD than towards the CD. Nerve fibers were found to be wavy, running both parallel and perpendicular to vascular and non-vascular smooth muscle within the vagina. Micro-structural analyses, like the one conducted here, are necessary to understand the physiological function and pathological changes of the vagina.

Strains induced in the vagina by smooth muscle contractions

The ability of the vagina to contract gives rise to a set of active mechanical properties that contribute to the complex function of this organ in-vivo. Regional differences in the morphology of the vagina have been long recognized, but the large heterogeneous deformations that the vagina experiences during contractions have never been quantified. Furthermore, there is no consensus regarding differences in contractility along the two primary anatomical directions of the vagina: the longitudinal direction (LD) and the circumferential direction (CD). In this study, square vaginal specimens from healthy virgin rats (n=15) were subjected to isometric planar biaxial tests at four equi-biaxial stretches of 1.0, 1.1, 1.2, and 1.3. Contractions were induced at each stretch by a high concentration potassium solution. The digital image correlation method was used to perform full-field strain measurements during contractions. The vagina was found to undergo significantly higher compressive strains, tensile strains, and contractile forces along the LD than along the CD during contractions. Specifically, when computed over all the applied equi-biaxial stretches, mean (± std. dev.) absolute maximum compressive strains were -(13.43 ± 1.56)% along the LD and -(3.19 ± 0.25)% along the CD, mean absolute maximum tensile strains were (10.92 ± 1.73)% along the LD and (3.62 ± 0.57)% along the CD, and mean maximum contractile forces were 6.24 ± 0.55 mN along the LD and 3.35 ± 0.56 mN along the CD. Moreover, the vaginal tissue appeared to undergo compression in the proximal region and tension in the distal region while kept at constant equi-biaxial stretches. The active mechanical properties of the healthy vagina need to be fully investigated so that detrimental alterations in vaginal contractility, such as those caused by pelvic floor disorders and current treatment strategies, can be prevented. STATEMENT OF SIGNIFICANCE: Contractile forces of the vagina have been measured by several investigators using uniaxial tensile testing methods. Unlike previous studies, in this study planar-biaxial tests of vaginal specimens were performed while the full-field strains of the vagina, as induced by smooth muscle contraction, were measured. The vagina was found to generate significantly larger contractile strains and forces in the longitudinal direction than in the circumferential direction. Knowledge of the contractile mechanics of the healthy vagina is essential to understand the detrimental effects that pelvic organ prolapse and the use of surgical meshes have on the functionality of smooth muscle in the vagina.

Animal Models and Alternatives in Vaginal Research: a Comparative Review

While developments in gynecologic health research continue advancing, relatively few groups specifically focus on vaginal tissue research for areas like wound healing, device development, and/or drug toxicity. Currently, there is no standardized animal or tissue model that mimics the full complexity of the human vagina. Certain practical factors such as appropriate size and anatomy, costs, and tissue environment vary across species and moreover fail to emulate all aspects of the human vagina. Thus, investigators are tasked with compromising specific properties of the vaginal environment as it relates to human physiology to suit their particular scientific question. Our review aims to facilitate the appropriate selection of a model aptly addressing a particular study by discussing pertinent vaginal characteristics of conventional animal and tissue models. In this review, we first cover common laboratory animals studied in vaginal research-mouse, rat, rabbit, minipig, and sheep-as well as human, with respect to the estrus cycle and related hormones, basic reproductive anatomy, the composition of vaginal layers, developmental epithelial origin, and microflora. In light of these relevant comparative metrics, we discuss potential selection criteria for choosing an appropriate animal vaginal model. Finally, we allude to the exciting prospects of increasing biomimicry for in vitro applications to provide a framework for investigators to model, interpret, and predict human vaginal health.

Contractile Properties of Vaginal Tissue

The vagina is an important organ of the female reproductive system that has been largely understudied in the field of biomechanics. In recent years, some research has been conducted to evaluate the mechanical properties of the vagina, but much has focused on characterizing the passive mechanical properties. Because vaginal contractions play a central role in sexual function, childbirth, and development and treatment of pelvic floor disorders, the active mechanical properties of the vagina must be also quantified. This review surveys and summarizes published experimental studies on the active properties of the vagina including the differences in such properties determined by anatomic regions and orientations, neural pathways, life events such as pregnancy and menopause, pelvic floor disorders such as prolapse, and surgical mesh treatment. Conflicting experimental findings are presented, illustrating the need for further research on the active properties of the vagina. However, consensus currently exists regarding the negative impact of surgical mesh on vaginal contractility. This review also identifies knowledge gaps and future research opportunities, thus proving a firm foundation for novice and experienced researchers in this emerging area of biomechanics and encouraging more activity on women's sexual and reproductive health research.

Histomorphological and Histochemical Investigation of The Vagina of Adult Guinea Pigs (Cavia porcellus)

This study was carried out to identify the morphological, histological and histochemical features of the vagina of the adult guinea pig (Cavia porcellus). To perform such project, 14 adult guinea pigs at their diestrous period were bought from the local breeders directly. Animals were euthanized, dissected and subsequently specimens from the cranial, middle and caudal portions of the vagina were collected and fixed. Fixation was implemented by using 10% neutral buffered formalin and Bouin’s solution. Post routine processing such as dehydration, clearing, embedding and blocks preparation, tissue sections of 6 μm were prepared and stained by using hematoxylin-eosin, Masson’s Trichrome, Alcian blue and Periodic acid shiff stains. Gross findings revealed that the vagina in the adult guinea pigs was characteristically very long tube-like structure with wide diameter. The vagina entirely was running ventral to the colon and then under the rectum in the pelvic cavity. It was terminated caudally by the vaginal orifice independent to the urethral orifice of the urinary system. Microscopic findings revealed mucous columnar lining epithelium which was folded at the vaginal fornix decreased caudally toward the external vaginal orifice where the epithelium changed into stratified squamous epithelium not keratinized. Thin dense lamina propria was continuous with loose connective tissue of the submucosa. Thickness of tunica muscularis was decreased which was surrounded with thick adventitia. Histochemically, the non-ciliated mucous columnar cells present in the lining epithelium of the cranial and middle regions of the vagina were positively stained with AB (pH 2.5) and PAS stains. The reaction with AB (pH 2.5) was more intense compared to the staining with PAS so that it indicated that mucin was more acidic than neutral in nature. Characteristic conclusions include that the vagina opening was U-shaped not circular and closed by transparent closure during the diestrous period. Histologically, the vagina also lined with mucoid lining and only the orifice and adjacent area lined with stratified squamous epithelium. Moreover, current study recorded differences in both macroscopic and microscopic aspects of the vagina in the guinea pigs compared to other animal considered laboratory species.

Anisotropy of the Passive and Active Rat Vagina Under Biaxial Loading

Pelvic organ prolapse, the descent of the pelvic organs from their normal anatomical position, is a common condition among women that is associated with mechanical alterations of the vaginal wall. In order to characterize the complex mechanical behavior of the vagina, we performed planar biaxial tests of vaginal specimens in both the passive (relaxed) and active (contracted) states. Specimens were isolated from virgin, female Long-Evans rats (n = 16) and simultaneously stretched along the longitudinal direction (LD) and circumferential direction (CD) of the vagina. Tissue contraction was induced by electric field stimulation (EFS) at incrementally increasing values of stretch and, subsequently, by KCl. On average, the vagina was stiffer in the CD than in the LD (p < 0.001). The mean maximum EFS-induced active stress was significantly higher in the CD than in the LD (p < 0.01). On the contrary, the mean KCl-induced active stress was lower in the CD than in the LD (p < 0.01). When comparing the mean maximum EFS-induced active stress to the mean KCl-induced active stress, no differences were found in the CD (p = 0.366) but, in the LD, the mean active stress was much higher in response to the KCl stimulation (p < 0.001). Collectively, these results suggest that the anisotropic behavior of the vaginal tissue is determined not only by collagen and smooth muscle fiber organization but also by the innervation.

Expression and significance of TIMP-3, PACAP and VIP in vaginal wall tissues of patients with stress urinary incontinence

The objective of the present study was to investigate whether tissue inhibitor of metalloproteinase-3 (TIMP-3), pituitary adenylate cyclase-activating polypeptide (PACAP), and vasoactive intestinal peptide (VIP) participate in the occurrence of female stress urinary incontinence (SUI) by measuring the expression levels of TIMP-3, PACAP, and VIP in the vaginal wall and analyzing their correlation to understand the pathogenesis of female SUI. Forty female patients who were admitted to our hospital for tension-free obturator tape surgery for treatment of SUI from April, 2012 to December, 2015 were selected as the study group. Forty patients who underwent vaginal or total abdominal hysterectomy for treatment of non-estrogen-related diseases during the same period were selected as the control group. Tissue samples from the anterior vaginal wall, located at twelve o'clock, were taken from both groups. The expression levels of TIMP-3, PACAP and VIP were detected by immunohistochemistry, and the correlation of integral optical density (IOD) among expressions of TIMP-3, PACAP, and VIP was investigated. The expression of TIMP-3 in vaginal wall tissues of the study group was lower than that of the control group (P<0.05). The expression of PACAP and VIP in vaginal tissues of the study group were lower than those of the control group (P<0.05). In the study group, the IOD of PACAP expression was significantly and positively correlated with that of VIP (r=0.873, P<0.05), the IOD of PACAP expression was significantly and positively correlated with that of TIMP-3 (r=0.802, P<0.05), and the IOD of VIP expression was significantly and positively correlated with that of TIMP-3 (r=0.716, P<0.05). In conclusion, TIMP-3, PACAP and VIP jointly participate in the occurrence of female SUI. Increasing the expression of TIMP-3, PACAP, and VIP, repairing neurons, and enhancing the elasticity of vaginal wall tissues may become a new way to treat female SUI.

Phasic contractions of the mouse vagina and cervix at different phases of the estrus cycle and during late pregnancy

BACKGROUND/AIMS

The pacemaker mechanisms activating phasic contractions of vaginal and cervical smooth muscle remain poorly understood. Here, we investigate properties of pacemaking in vaginal and cervical tissues by determining whether: 1) functional pacemaking is dependent on the phase of the estrus cycle or pregnancy; 2) pacemaking involves Ca2+ release from sarcoplasmic/endoplasmic reticulum Ca2+-ATPase (SERCA) -dependent intracellular Ca2+ stores; and 3) c-Kit and/or vimentin immunoreactive ICs have a role in pacemaking.

METHODOLOGY/PRINCIPAL FINDINGS

Vaginal and cervical contractions were measured in vitro, as was the distribution of c-Kit and vimentin positive interstitial cells (ICs). Cervical smooth muscle was spontaneously active in estrus and metestrus but quiescent during proestrus and diestrus. Vaginal smooth muscle was normally quiescent but exhibited phasic contractions in the presence of oxytocin or the K+ channel blocker tetraethylammonium (TEA) chloride. Spontaneous contractions in the cervix and TEA-induced phasic contractions in the vagina persisted in the presence of cyclopiazonic acid (CPA), a blocker of the SERCA that refills intracellular SR Ca2+ stores, but were inhibited in low Ca2+ solution or in the presence of nifedipine, an inhibitor of L-type Ca2+channels. ICs were found in small numbers in the mouse cervix but not in the vagina.

CONCLUSIONS/SIGNIFICANCE

Cervical smooth muscle strips taken from mice in estrus, metestrus or late pregnancy were generally spontaneously active. Vaginal smooth muscle strips were normally quiescent but could be induced to exhibit phasic contractions independent on phase of the estrus cycle or late pregnancy. Spontaneous cervical or TEA-induced vaginal phasic contractions were not mediated by ICs or intracellular Ca2+ stores. Given that vaginal smooth muscle is normally quiescent then it is likely that increases in hormones such as oxytocin, as might occur through sexual stimulation, enhance the effectiveness of such pacemaking until phasic contractile activity emerges.

Effect of estrogen on molecular and functional characteristics of the rodent vaginal muscularis

INTRODUCTION

Vaginal atrophy is a consequence of menopause; however, little is known concerning the effect of a decrease in systemic estrogen on vaginal smooth muscle structure and function. As the incidence of pelvic floor disorders increases with age, it is important to determine if estrogen regulates the molecular composition and contractility of the vaginal muscularis.

AIM

The goal of this study was to determine the effect of estrogen on molecular and functional characteristics of the vaginal muscularis utilizing a rodent model of surgical menopause.

METHODS

Three- to 4-month old Sprague-Dawley rats underwent sham laparotomy (Sham, N = 18) or ovariectomy (Ovx, N = 39). Two weeks following surgery, animals received a subcutaneous osmotic pump containing vehicle (Sham, Ovx) or 17β-estradiol (Ovx). Animals were euthanized 1 week later, and the proximal vagina was collected for analysis of contractile protein expression and in vitro studies of contractility. Measurements were analyzed using a one-way analysis of variance followed by Tukey's post hoc analysis (α = 0.05).

MAIN OUTCOME MEASURES

Protein and mRNA transcript expression levels of contractile proteins, in vitro measurements of vaginal contractility.

RESULTS

Ovariectomy decreased the expression of carboxyl-terminal myosin heavy chain isoform (SM1) and h-caldesmon and reduced the amplitude of contraction of the vaginal muscularis in response to KCl. Estradiol replacement reversed these changes. No differences were detected in the % vaginal muscularis, mRNA transcript expression of amino-terminal MHC isoforms, l-caldesmon expression, and maximal velocity of shortening.

CONCLUSION

Systemic estrogen replacement restores functional and molecular characteristics of the vaginal muscularis of ovariectomized rats. Our results indicate that menopause is associated with changes in the vaginal muscularis, which may contribute to the increased incidence of pelvic floor disorders with age.

Regional differences in rat vaginal smooth muscle contractility and morphology

The objective of this study was to define the regional differences in rat vaginal smooth muscle contractility and morphology. We evaluated circumferential segments from the proximal, middle, and distal rat vagina (n = 21) in vitro. Contractile responses to carbachol, phenylephrine, potassium chloride, and electrical field stimulation (EFS) were measured. Immunohistochemical analyses were also performed. The dose-response curves for carbachol- and phenylephrine-dependent contractions were different in the distal (P = .05, P = .04) compared to the proximal/middle regions. Adjusted for region-dependent changes in contractility, the distal vagina generated lower force in response to carbachol and higher force in response to phenylephrine. There was less force with increasing EFS frequency in the distal (P = .03), compared to the proximal/middle regions. Cholinergic versus adrenergic nerves were more frequent in the proximal region (P = .03). In summary, the results indicate that functional and morphological differences in smooth muscle and nerve fibers of the distal versus proximal/middle regions of the vagina exist.

Adaptive plasticity of vaginal innervation in term pregnant rats

Changes in reproductive status place varied functional demands on the vagina. These include receptivity to male intromission and sperm transport in estrus, barrier functions during early pregnancy, and providing a conduit for fetal passage at parturition. Peripheral innervation regulates vaginal function, which in turn may be influenced by circulating reproductive hormones. We assessed vaginal innervation in diestrus and estrus (before and after the estrous cycle surge in estrogen), and in the early (low estrogen) and late (high estrogen) stages in pregnancy. In vaginal sections from cycling rats, axons immunoreactive for the pan-neuronal marker protein gene product 9.5 (PGP 9.5) showed a small reduction at estrus relative to diestrus, but this difference did not persist after correcting for changes in target size. No changes were detected in axons immunoreactive for tyrosine hydroxylase (sympathetic), vesicular acetylcholine transporter (parasympathetic), or calcitonin gene-related peptide and transient receptor potential vanilloid type 1 (TRPV-1; sensory nociceptors). In rats at 10 days of pregnancy, innervation was similar to that observed in cycling rats. However, at 21 days of pregnancy, axons immunoreactive for PGP 9.5 and each of the subpopulation-selective markers were significantly reduced both when expressed as percentage of sectional area or after correcting for changes in target size. Because peripheral nerves regulate vaginal smooth muscle tone, blood flow, and pain sensitivity, reductions in innervation may represent important adaptive mechanisms facilitating parturition.

Functional significance of muscarinic receptor expression within the proximal and distal rat vagina

Information regarding the role of cholinergic nerves in mediating vaginal smooth muscle contraction is sparse, and in vitro studies of the effects of muscarinic agonists on vaginal smooth muscle are discrepant. The goal of this study was to determine the expression of muscarinic receptors in the vaginal wall of the rat. In addition, we sought to determine the effect of the muscarinic receptor agonist carbachol on contractility and inositol phosphate production of the proximal and distal rat vaginal muscularis. RT-PCR analysis indicated that both M(2) and M(3) receptor transcripts were expressed within the proximal and distal rat vagina. Carbachol dose-dependently (10(-7)-10(-4) M) contracted the rat vaginal muscularis with a greater maximal contractile response in the proximal vagina (P < 0.01) compared with the distal vagina. The contractile responses of the rat vaginal muscularis to carbachol were dose dependently inhibited by the M(3) antagonist para-fluoro-hexahydrosiladefenidol, and a pK(B) of 7.78 and 7.95 was calculated for the proximal and distal vagina, respectively. Inositol phosphate production was significantly increased in both regions of the vagina following 20-min exposure to 50 muM carbachol with higher levels detected in the proximal vagina compared with the distal (P < 0.05). Preliminary experiments indicated the presence of M(2) and M(3) receptors in the human vaginal muscularis as well as contraction of human vaginal muscularis to carbachol, indicating that our animal studies are relevant to human tissue. Our results provide strong evidence for the functional significance of M(3) receptor expression in the vaginal muscularis.

Endothelial nitric oxide synthase regulation in female genital tract structures

INTRODUCTION

Female sexual arousal disorder (FSAD) is a major component of female sexual dysfunctions, affecting 25-70% of women. The mechanisms of FSAD are poorly understood. Estrogen contributes to the control of genital blood flow during the sexual response. Vascular effects of estrogen are mostly attributed to its regulation of endothelial nitric oxide (NO) production. However, the role of endothelial NO synthase (eNOS) and the mechanisms that regulate eNOS in female genital tract structures are largely unknown.

AIM

To review available evidence of the mechanisms of eNOS regulation in female genital tract structures.

METHODS

This article reviews the literature that relates to the role of NO and eNOS in female sexual arousal and its modulation by estrogen.

MAIN OUTCOME MEASURES

Association between female sexual arousal, NO, and eNOS.

RESULTS

The NO/cyclic guanosine monophosphate pathway is believed to have a primary role in the regulation of clitoral and vaginal blood flow, and smooth muscle relaxation during sexual arousal. Estrogen is critical for maintaining vaginal and clitoral blood flow and vaginal transudate production. Estrogen regulates eNOS by genomic mechanisms, involving augmented mRNA transcription and protein synthesis, and by non-genomic mechanisms, which occur without alterations in gene expression. However, limited studies have evaluated the physiological role of endothelial NO and the molecular mechanisms of eNOS regulation in the female genital tract.

CONCLUSIONS

The effects of estrogen on increasing genital blood flow and smooth muscle relaxation have been attributed mostly to regulation of eNOS. However, the exact mechanisms of eNOS regulation in female genital tract structures and the molecular basis for the eNOS defect with aging and vascular diseases warrant further investigation.

General tissue characteristics of the lower urethral and vaginal walls in the domestic rabbit

In European rabbits, the distal urethra (DU) opens into the anterior pelvic vagina forming a single canal by which females copulate, give birth, and urinate. We investigated whether the histological characteristics of the DU and the pelvic and perineal vagina are different. The DU and vagina of rabbits (Oryctolagus cuniculus) were cut and stained with hematoxylin-eosin and Masson's trichrome (n = 3). Data were compared by using Friedman's ANOVA for repeated measures. The walls of the DU and vagina are composed of mucosa, submucosa, smooth muscle, and an external layer. Differences in tissue characteristics of the mucosa, orientation of the smooth muscle fibers, components of the external layer (connective tissue, blood vessels, and striated musculature), and thickness of the tissue layers were found among regions. The lack of histological homogeneity along the urethra and vagina possibly reflects differences in the functions of each segment.

Role of vasoactive intestinal peptide and pituitary adenylate cyclase activating polypeptide in the vaginal wall of women with stress urinary incontinence and pelvic organ prolapse

Pelvic floor connective tissue degeneration is closely associated with retrogradation of its dominating nerve fibers. We hypothesized that some neuropeptides from pelvic floor tissue might be involved in the pathological progress of stress urinary incontinence (SUI) and pelvic organ prolapse (POP) in women. Thirty premenopausal and 31 postmenopausal patients participated in the study. The morphological appearance in the vaginal tissue was examined. The vasoactive intestinal peptide (VIP) and pituitary adenylate cyclase activating polypeptide-38 (PACAP) immunoreactivities (ir-VIP, ir-PACAP) were tested by immunohistochemistry and radioimmunoassay. We found that the VIP and PACAP immunostainings were weaker and sparser, and ir-VIP and ir-PACAP levels were significantly decreased in the anterior vaginal wall in the premenopausal and postmenopausal SUI or POP patients. Ir-VIP and ir-PACAP levels were reversely correlated with the age and menopausal status in the SUI or POP patients. Our data suggest that VIP and PACAP may participate in the pathophysiological process of SUI and POP.

Increased vaginal oxidative stress, apoptosis, and inducible nitric oxide synthase in a diabetic rat model: implications for vaginal fibrosis

OBJECTIVE

To determine whether vaginal fibrosis occurs in diabetic animals and is associated with oxidative stress and cell death and with the expression of inducible nitric oxide synthase (iNOS), as a putative antifibrotic mechanism.

DESIGN

Research experimental project.

SETTING

University research laboratory.

ANIMAL(S)

Female Wistar rats.

INTERVENTION(S)

Female rats were injected with streptozotocin or saline and killed at 3 months. The vaginas were excised and processed for paraffin-embedded sections (n = 6 per group) or were frozen for biochemical and molecular biology procedures.

MAIN OUTCOME MEASURE(S)

Immunohistochemistry and quantitative image analysis were applied to tissue sections to measure alpha-smooth muscle actin, transforming growth factor beta1, plasminogen activator inhibitor, NOS isoforms, Cu/Zn superoxide dismutase, apoptotic index, and nitrotyrosine. Xanthine dehydrogenase, reactive oxygen species (ROS), and hydroxyproline were measured in fresh vaginal tissue (n = 5 per group). Reactive oxygen species also were determined in blood.

RESULT(S)

Diabetes was associated with vaginal fibrosis, as evidenced by increased collagen, transforming growth factor beta1, plasminogen activator inhibitor, and apoptosis, and by decreased alpha-smooth muscle actin. The increment of ROS and the reduction of superoxide dismutase indicated oxidative stress in diabetic tissue, accompanied by iNOS induction and increased nitric oxide-ROS reaction.

CONCLUSION(S)

Diabetes in the rat causes oxidative stress and fibrosis in the vagina, which may be compensated partially by iNOS induction to reduce ROS.

The effect of ovariectomy on rat vaginal tissue contractility and histomorphology

INTRODUCTION

Ovarian hormones have an important role in age-related genital arousal disorders; however, our knowledge regarding possible vaginal wall morphology and contractility changes in low-hormonal states is limited.

AIMS

To investigate morphological and functional alterations in the vaginal tissue in a rat ovariectomy model and to show the differences between proximal and distal vagina.

METHODS

Six weeks following ovariectomy, vaginal tissues were examined under light and electron microscopy. Circularly cut distal and proximal tissues were studied in the organ bath under isometric tension and compared with age-matched controls. Contractile responses to electrical field stimulation (EFS), phenylephrine, carbachol, and the effects of alpha-1 and alpha-2 blockade on EFS-induced contractility were investigated. Relaxation responses to EFS and vardenafil were investigated in precontracted strips.

MAIN OUTCOME MEASURES

Differences between control and ovariectomy groups in terms of vaginal tissue contractility and histomorphological properties.

RESULTS

Distal vagina showed different epithelial characteristics and a better-developed muscularis compared with proximal vagina. Ovariectomy caused thinning of the epithelium, severe degeneration in epithelial architecture, and smooth muscle atrophy. Contraction and relaxation responses of distal strips were significantly lower in ovariectomized rats. Contractile responses to neuropharmacological stimulation were insignificant in proximal strips of both groups. EFS-induced contractions in distal strips diminished significantly after alpha-1 and alpha-2 adrenergic blockade. EFS caused frequency-dependent relaxation responses in precontracted distal strips, which were significantly decreased after nitric oxide synthase inhibition.

CONCLUSIONS

Ovariectomy causes significant alteration in rat vaginal tissue morphology and contractility. Contraction and relaxation responses of distal vagina are significantly greater compared with morphologically distinct proximal vagina. Alpha-1 and alpha-2 receptors are the main mediators of contraction in distal rat vaginal tissue whereas nitric oxide pathway may have at least a partial role in relaxation. Main mediators of the rat vaginal tissue relaxation and the effect of ovariectomy on this regulation are yet to be defined.

Regional differences in myosin heavy chain isoform expression and maximal shortening velocity of the rat vaginal wall smooth muscle

Contractility of the proximal and distal vaginal wall smooth muscle may play distinct roles in the female sexual response and pelvic support. The goal of this study was to determine whether differences in contractile characteristics of smooth muscle from these regions reside in differences in the expression of isoforms of myosin, the molecular motor for muscle contraction. Adult female Sprague-Dawley rats were killed on the day of estrus, and the vagina was dissected into proximal and distal segments. The Vmax at peak force was greater for tissue strips of the proximal vagina compared with that of distal (P < 0.01), although, at steady state, the Vmax for the muscle strips from the two regions was not different. Furthermore, at steady state, muscle stress was higher (P < 0.001) for distal vaginal strips (n = 5). Consistent with the high Vmax for the proximal vaginal strips, RT-PCR results revealed a higher %SM-B (P < 0.001) in the proximal vagina. A greater expression of SM-B protein (P < 0.001) was also detected by Western blotting (n = 4). Interestingly, there was no regional difference noted in SM-1/SM-2 isoforms (n = 6). The proximal vagina had a higher expression of myosin heavy chain protein (P < 0.01) and a greater percentage of smooth muscle bundles (P < 0.001). The results of this study are the first demonstration of a regional heterogeneity in Vmax and myosin isoform distribution in the vagina wall smooth muscle and confirm that the proximal vaginal smooth muscle exhibits phasic contractile characteristics compared with the distal vaginal smooth muscle, which is tonic.

Cyclic adenosine monophosphate and cyclic guanosine monophosphate-phosphodiesterase isoenzymes in human vagina: relation to nitric oxide synthase isoforms and vasoactive intestinal polypeptide-containing nerves

OBJECTIVES

To evaluate the distribution of cyclic guanosine monophosphate (cGMP) and cyclic adenosine monophosphate (cAMP) phosphodiesterases (PDEs) in relation to nitric oxide synthase isoforms and vasoactive intestinal polypeptide (VIP) in specimens of the human vagina. Nitric oxide and VIP, mediating biologic signals through cGMP and cAMP, have been assumed to be involved in the control of vaginal smooth muscle.

METHODS

Immunohistochemical techniques were applied to sectioned specimens of the human vaginal wall to evaluate the presence of the PDE isoenzymes 3, 4, 5, and 10 in relation to neuronal nitric oxide synthase (nNOS), endothelial NOS (eNOS), and VIP.

RESULTS

Immunoreactivity (IR) for cAMP-degrading PDE-4 was observed in the vaginal nonvascular smooth musculature, as well as in the wall of subepithelial arteries. VIP-IR nerves innervated the smooth muscle portion of the vaginal wall and also formed a subepithelial network. Immunoreactivity specific for PDE-5 was also registered in vascular and nonvascular vaginal smooth muscle. Immunosignals for eNOS were detected in the endothelial lining of arteries containing PDE-5-IR smooth muscle cells. These arteries were supplied by nNOS-IR nerve fibers. PDE-10-IR smooth muscle cells were located in muscle bundles of the vaginal wall.

CONCLUSIONS

Our study revealed immunoreactivity specific for PDE-4, PDE-5, and PDE-10 in the vascular and nonvascular smooth muscle of the vagina. Immunosignals for PDE-4 and PDE-5 were also observed in close proximity to nNOS-IR or VIP-IR nerve fibers or to eNOS-IR endothelial cells. The distribution of PDEs may indicate a role of these enzymes in the control of the function of the human vagina.