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

The Effect of Menopause on Vaginal Tissue Mechanics: A Brief Review

Often called "the change of life," menopause affects every part of a woman's body. As the sex hormones decrease, the reproductive organs experience the most remarkable changes, with the vagina becoming thinner, drier, and less elastic. Despite the important implications of these changes in genitourinary conditions, there are only a few experimental studies that focus on quantifying the effect of menopause on the mechanical properties of the vagina. These studies are mostly conducted using uniaxial tests on strips of vaginal tissues isolated from rats, rabbits, and sheep and, in only a few cases, from humans. The purpose of this article is to present a systematic review of experimental protocols, methods, and results that are currently published on how menopause alters the mechanical behavior of the vagina. This review will enable new investigators in the biomechanics field to identify important gaps and frame research questions that inform the design of new treatment options for menopausal symptoms.

Assessment of the Elastographic and Electromyographic of Pelvic Floor Muscles in Postmenopausal Women with Stress Urinary Incontinence Symptoms

Background. Shear wave elastography is an effective method for studying the condition of various musculoskeletal soft tissues. The primary aim of this study was the objective elastographic and electromyographic assessment of the pelvic floor during the rest and contraction of the pelvic floor muscles (PFM) in postmenopausal women. Methods. This was a prospective observational study that was carried out at the University Hospital in Wroclaw, Poland, between January 2017 and December 2019. Patients. The target group of the study included postmenopausal women with stress urinary incontinence. The primary outcomes were the features of the elastographic assessment of the pelvic floor during rest and contraction of the PFM obtained using shear wave elastography. Results. Based on the inclusion and exclusion criteria for the study, 14 patients took part in the measurements. There was a significant difference between the elastographic assessment of the pelvic floor during rest and contraction of the PFM at all locations in front of the urethra. No statistically significant correlation was found between the results of elastography and the bioelectrical activity of PFM. Conclusion. The elasticity of the periurethral structures is higher during active pelvic floor muscle contraction than at rest, it seems that shear wave elastography is an effective test that objectively assesses the strength of PFM contraction.

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 for pelvic organ prolapse: systematic review

INTRODUCTION AND HYPOTHESIS

We aimed to summarize the knowledge on the pathogenesis of pelvic organ prolapse (POP) generated in animal models.

METHODS

We searched MEDLINE, Embase, Cochrane and the Web of Science to establish what animal models are used in the study of suggested risk factors for the development of POP, including pregnancy, labor, delivery, parity, aging and menopause. Lack of methodologic uniformity precluded meta-analysis; hence, results are presented as a narrative review.

RESULTS

A total of 7426 studies were identified, of which 51 were included in the analysis. Pregnancy has a measurable and consistent effect across species. In rats, simulated vaginal delivery induces structural changes in the pelvic floor, without complete recovery of the vaginal muscular layer and its microvasculature, though it does not induce POP. In sheep, first vaginal delivery has a measurable effect on vaginal compliance; measured effects of additional deliveries are inconsistent. Squirrel monkeys can develop POP. Denervation of their levator ani muscle facilitates this process in animals that delivered vaginally. The models used do not develop spontaneous menopause, so it is induced by ovariectomy. Effects of menopause depend on the age at ovariectomy and the interval to measurement. In several species menopause is associated with an increase in collagen content in the longer term. In rodents there were no measurable effects of age apart of elastin changes. We found no usable data for other species.

CONCLUSION

In several species there are measurable effects of pregnancy, delivery and iatrogenic menopause. Squirrel monkeys can develop spontaneous prolapse.

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.

Tissue Composition and Biomechanical Property Changes in the Vaginal Wall of Ovariectomized Young Rats

Ideal animal models are needed to reflect the changes in the biochemical and biomechanical properties of the vagina that occur in pelvic organ prolapse (POP). In this study, we aimed to demonstrate the short and long-term effect of menopause on the biochemical and biomechanical properties of rat anterior vaginas. Here, Sprague-Dawley rats were bilaterally ovariectomized to induce menopause. Rats without ovariectomy served as the normal control group (n=12). The histology changes and the expression of collagen I, III, and a-SMA were assessed to indicate the biochemical changes in the vagina 2 weeks, 4 weeks, and 16 weeks after ovariectomy (n=6 for 2 and 4 weeks, n=12 for 16 weeks). Uniaxial biomechanical testing was conducted in the control group and ovariectomized rats 16 weeks after ovariectomy. Compared with the control group, the ovariectomy group showed a significant increase in the expression of collagen I 2 weeks after ovariectomy, while collagen III showed a declining trend. Two weeks after ovariectomy, the smooth muscle bundles began to become disorganized, and the fraction of smooth muscle in the nonvascular muscularis of the proximal vagina was significantly decreased (P<0.001). However, there was no difference in the expression of a-SMA in the distal vagina. Compared with the control group, the ovariectomy group had stiffer vaginas with a declining trend in the ultimate load 16 weeks after ovariectomy. In conclusion, surgically induced menopause had a significant short- and long-term impact on tissue composition and biomechanical properties of the rat vagina, which may lead to increased susceptibility to POP development.

Effects of Ficus umbellata (Moraceae) Aqueous Extract and 7-Methoxycoumarin on Scopolamine-Induced Spatial Memory Impairment in Ovariectomized Wistar Rats

The present work was undertaken to evaluate the ability of F. umbellata aqueous extract and its major component 7-methoxycoumarin (MC) to improve scopolamine-induced spatial memory impairment in ovariectomized Wistar rats. For this to be done, 10 sham-operated and 30 postmenopausal-like rats were randomly distributed in eight groups (n = 5) and treated with distilled water (2 mL/250 g), estradiol valerate (1 mg/kg BW), piracetam (1.5 mg/kg BW), F. umbellata aqueous extract (50 and 200 mg/kg BW), or MC (1 mg/kg BW) for 21 consecutive days. Before and after the memory impairment with scopolamine (2 mg/kg BW), animals underwent behavioral evaluations on Y- and radial mazes. As results, age and ovariectomy did not induce significant changes in the reference memory errors. While age decreased working memory errors, ovariectomy increased it. The MC as well as F. umbellata extract significantly increased (p < 0.01) the percentage of spontaneous alternation and decreased (p < 0.001) working and spatial reference memory errors and anxiety parameters (rearing and grooming) in ovariectomized rats. MC significantly reduced (p < 0.05) the MDA level, but resulted in an increase in GSH level in brain homogenates. These results suggest that MC is endowed with neuroprotective effects and could account for the neuroprotective effects of F. umbellata in rats.

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.

Millettia macrophylla (Fabaceae) phenolic fraction prevents differentiation of 3T3-L1 adipocytes and the increased risks of cardiovascular diseases in ovariectomized rats

ETHNOPHARMACOLOGICAL RELEVANCE

A prolonged estrogen deficiency alters lipid metabolism and increases risks of cardiovascular diseases. Phytoestrogens, naturally occurring compounds with estrogenic properties are reported to have cardiovascular protective effects. Millettia macrophylla used in the Cameroonian traditional system to treat physiological disorders related to menopause, was previously reported to have estrogenic effects.

AIM

We, therefore, proposed evaluating the in vitro and in vivo effects of M. macrophylla phenolic fraction on some risk factors for cardiovascular diseases.

MATERIAL AND METHODS

In vitro, the ability of the M. macrophylla phenolic fraction (PF) as well as the 9 isolates to prevent the 3T3-L1 preadipocytes differentiation was assessed. Further, the preventive effects of PF on abdominal fat accumulation, body weight gain, lipid profile, nitric oxide level, superoxide dismutase (SOD) and catalase activities, reduced glutathione (GSH) and malondialdehyde (MDA) levels were assessed in a postmenopausal rat model.

RESULTS

In vitro, PF and its isolate secundiferol I inhibited lipid accumulation in 3T3-L1 cells. Moreover, all the isolates except daidzein dimethylether prevented the interleukin IL-6 production in 3T3-L1 cells. In vivo, PF prevented ovariectomy-induced abdominal fat accumulation, body weight gain, dyslipidemia, glucose intolerance and decreased atherogenic index. In addition, it induced a vasorelaxant effect by preventing the low level of nitric oxide in the aorta. PF also exhibited antioxidant effects as it increased aorta GSH level, SOD, and catalase activities and decreased MDA level.

CONCLUSIONS

Taken together, our data suggest that PF prevents the increased risks of cardiovascular diseases in ovariectomized rats.

Relationship between lower limb position and pelvic floor muscle surface electromyography activity in menopausal women: a prospective observational study

Objectives

In physiotherapeutic practice, special attention is being given to the reciprocal anatomical, physiological, and biomechanical relationship of the pelvis and the structures connected to it. However, the scientific literature shows mainly the theoretical information about their mutual connections. The lack of information about these relations from a practical aspect coupled with the paucity of scientific papers on the impact of posture changes on the pelvic floor led the authors to conduct this study. The primary aim of this study was to compare the resting and functional bioelectrical activities of pelvic floor muscles (PFMs) depending on three different positions of the lower limbs (positions A, B, and C) in the supine position.

Materials and methods

This was a prospective observational study evaluating resting and functional activities of the PFM depending on the position of the lower limbs. The study was carried out at the Department and Clinic of Urology, University Hospital in Wroclaw, Poland and the target group were women in the menopausal period. Bioelectrical activity of PFM was recorded using a surface electromyographic instrument in the supine position. Results of the values obtained in A, B, and C positions were compared using a one-way analysis of variance.

Results

In position A, the average resting surface electromyography (sEMG) activity of PFM was 6.9±2.6 µV; in position B, the result was 6.9±2.5 µV and in position C, the resting sEMG activity was 5.7±1.8 µV (P=0.0102). The results of the functional bioelectrical activity of PFM were as follows: position A – 20.3±11.8 µV, position B – 19.9±10.6 µV, and position C – 25.3±10.9 µV (P=0.0104).

Conclusion

The results showed that in the supine position, the PFM achieved the lowest resting activity and the highest functional activity. Therefore, the supine position can be recommended for the diagnosis and therapy of weakened PFM.

Estrogenic effects of Ficus umbellata Vahl. (Moraceae) extracts and their ability to alleviate some menopausal symptoms induced by ovariectomy in Wistar rats

ETHNOPHARMACOLOGICAL RELEVANCE

Ficus umbellata Vahl. (Moraceae) is a medicinal plant used in Cameroon to treat amenorrhea as well as other physiological disorders related to menopause.

AIM OF STUDY

In order to justify scientifically its traditional use, the estrogen-like properties of the aqueous (AE) and methanol (MeOH) extracts of F. umbellata were investigated.

MATERIAL AND METHODS

In vitro, the ability of different extracts of F. umbellata to activate estrogen receptors α (ERα) and β (ERβ) in cell-based reporter gene assays using human embryonic kidney (HEK293T) cells transfected with ERs was tested. In vivo, a 3-day uterotrophic assay and the capacity of the extracts to alleviate hot flushes in ovariectomized adult rats were tested. Using a bioassay-guided fractionation the major compound of F. umbellata was isolated and tested in vitro on HEK293T-ERα and ERβ cells.

RESULTS

AE and MeOH extracts significantly altered ERα as well as ERβ activities. In vivo, both extracts significantly increase the uterine and vaginal epithelium thickness, and uterine total protein levels in a dose dependent manner. Interestingly, both extracts of F. umbellata at the dose of 100 mg/kg BW significantly decreased the total number, average duration as well as frequency of hot flushes in experimental rats compared to age-matched OVX controls. Finally, 7-methylumbelliferone, a coumarin was characterized as the major compound of F. umbellata; however this compound did not transactivate ERα as well ERβ in vitro.

CONCLUSION

These aforementioned results suggest that F. umbellata extracts as used by the traditional practitioner have estrogen-like effects and may alleviate some menopausal problems such as vaginal dryness and hot flushes.

Glutamic acid ameliorates estrogen deficiency-induced menopausal-like symptoms in ovariectomized mice

Some amino acids are considered alternative therapies for improving menopausal symptoms. Glutamic acid (GA), which is abundant in meats, fish, and protein-rich plant foods, is known to be a neurotransmitter or precursor of γ-aminobutyric acid. Although it is unclear if GA functions in menopausal symptoms, we hypothesized that GA would attenuate estrogen deficiency-induced menopausal symptoms. The objective to test our hypothesis was to examine an estrogenic effect of GA in ovariectomized (OVX) mice, estrogen receptor (ER)-positive human osteoblast-like MG-63 cells, and ER-positive human breast cancer MCF-7 cells. The results demonstrated that administration with GA to mice suppressed body weight gain and vaginal atrophy when compared with the OVX mice. A microcomputed tomographic analysis of the trabecular bone showed increases in bone mineral density, trabecular number, and connectivity density as well as a significant decrease in total porosity of the OVX mice treated with GA. In addition, GA increased serum levels of alkaline phosphatase and estrogen compared with the OVX mice. Furthermore, GA induced proliferation and increased ER-β messenger RNA (mRNA) expression, estrogen response element (ERE) activity, extracellular signal-regulated kinase phosphorylation, and alkaline phosphatase activity in MG-63 cells. In MCF-7 cells, GA also increased proliferation, Ki-67 mRNA expression, ER-β mRNA expression, and ERE activity. Estrogen response element activity increased by GA was inhibited by an estrogen antagonist. Taken together, our data demonstrated that GA has estrogenic and osteogenic activities in OVX mice, MG-63 cells, and MCF-7 cells.

The standardized BHH10 extract, a combination of Astragalus membranaceus, Cinnamomum cassia, and Phellodendron amurense, reverses bone mass and metabolism in a rat model of postmenopausal osteoporosis

Jasin-hwan-gagambang (BHH10), a modified prescription of Jasin-hwan, contains Astragalus membranaceus, Cinnamomum cassia, and Phellodendron amurense, and it has been traditionally used to treat osteoporosis and other inflammatory diseases. In this study, we systematically investigated the protective effects of BHH10 in ovariectomy (OVX)-induced rats. Sprague–Dawley rats were randomly divided into sham and OVX subgroups. The rats in the OVX group were treated with vehicle, BHH10, alendronate (ALN), and 17β-estradiol (E2). BHH10 treatment significantly inhibited OVX-induced increases in body weight and uterus atrophy. In addition, it significantly increased the bone mineral density (BMD) and prevented a decrease in trabecular bone volume, connectivity density, trabecular number, thickness, and separation at the total femur and femur neck. The OVX rats showed significant decreases in the serum levels of calcium and phosphorous and significant increases in the serum levels of cholesterol, low-density lipoprotein cholesterol, alkaline phosphatase, osteocalcin, C-telopeptide type 1 collagen, and bone morphogenetic protein-2. These changes were significantly reduced to near sham levels by administration of BHH10 to OVX rats. BHH10-treated rats had a greater bone mass, a better structural architecture of the bone, and higher levels of biochemical markers of the bone than did the ALN-treated or E2-treated rats. These results suggest that BHH10 reverses osteoporosis in OVX rats by stimulating bone formation or regulating bone resorption and is not associated with toxicity. © 2014 The Authors. Phytotherapy Research published by John Wiley & Sons Ltd.

Preventive effects of the methanol soluble fraction of Millettia macrophylla Benth (Fabaceae) on an osteoporosis-like model of ovariectomized Wistar rats

BACKGROUND

Millettia macrophylla Benth is a Cameroonian medicinal plant traditionally used to alleviate menopause-related problems. The methanol soluble fraction of this plant was shown to exhibit estrogenic effects in vitro in Human Embryonic kidney cells, and in vivo on ovariectomized rat following the classical uterotrophic assay. Since estrogens have been involved in bone remodeling process, the present study then aimed at evaluating bone loss preventive effects of the methanol soluble fraction of Millettia macrophylla (MM-met) in ovariectomized rat model.

METHODS

Twenty-five healthy Wistar female rats (3-month-old) were randomly assigned to a sham-operated group and to four treated ovariectomized (OVX) groups. Treatments lasted 8 weeks and animals were sacrificed. The uterus, the femoral and the tibia bones of each animal were collected, weighed and fixed in 10% formalin for histological analysis.

RESULTS

Results showed that ovariectomy decreased uterine wet weight (p<0.01), induced body weight gain (p<0.01), decreased both femoral and tibia bone density and mineral content and increased alkaline phosphatase activity (p<0.05). E2V and MM-met treatments in general prevented bone mass loss and/or bone density loss. At all tested doses, MM-met induced a significant decrease of alkaline phosphatase activity (p<0.05). As observed with E2V, MM-met also induced a significant protective effect on bone, and this was indicated by an abundance of bone marrow in an almost intact trabecular network.

CONCLUSIONS

The overall results show that the methanol soluble fraction of Millettia macrophylla may prevent ovariectomy-induced bone mass loss and deterioration of the trabecular microarchitecture.