Pregnancy-induced adaptations in intramuscular extracellular matrix of rat pelvic floor muscles

Pelvic Floor Ultrasound Findings and Symptoms of Pelvic Floor Dysfunction During Pregnancy

INTRODUCTION AND HYPOTHESIS

Pregnancy and childbirth predispose to pelvic floor dysfunction (PFD), coinciding with functional and anatomical changes in the pelvic floor. To some extent, these can be assessed by transperineal ultrasound (TPUS), yet the correlation between ultrasound findings and symptoms has not been well elucidated. We hypothesised that pregnant women with PFD would show different findings at TPUS.

METHODS

This is a planned secondary analysis of a prospective cohort study. Pregnant women were asked to fill out standardised questionnaires on PFD and undergo TPUS at 12-14 weeks and 28-32 weeks of gestation. We compared bladder neck descent, urethral rotation, retrovesical angle, pelvic organ descent, genital hiatus dimensions and the presence of anal sphincter defects between women with and those without PFD using t test and Fisher's exact test. Linear mixed-effects models were used to assess the correlation between TPUS findings and PFD severity. As this is a secondary subgroup analysis of participants who underwent TPUS, no sample size was determined upfront.

RESULTS

At Valsalva, women with urinary incontinence had more pronounced bladder neck descent (p = 0.02) and urethral rotation (p < 0.01), as well as wider retrovesical angles (p = 0.04) and larger genital hiatus areas (p < 0.01). After controlling for age, BMI and parity, the retrovesical angle was the only persistent predictor of urinary incontinence. No correlation was observed between any TPUS marker and symptoms of either prolapse or anorectal dysfunction.

CONCLUSIONS

In pregnant women, symptoms of urinary incontinence, but not of prolapse and anorectal dysfunction, are associated with differences in pelvic floor anatomy at TPUS.

Effect of pregnancy and childbirth on perineal musculature in women with obesity. A longitudinal cohort study

OBJECTIVE

Evaluating the changes of the perineal muscles in primigravid women with obesity (BMI ≥ 30) and to compare the progress with primigravid women in normal BMI range.

METHODS

A prospective longitudinal cohort study was carried out. The pregnant women were studied at three moments: at 12 weeks' gestation, at 34 weeks' gestation and at 12 weeks after delivery. During the ckeck-up, perinometric measurements were taken to determine basal tone (BT), maximum contractile force (FMax) and applied forced (AF). In addition, the Oxford test (MOS) was used. General statistical mixed models were used for the statistical study.

RESULTS

Fifty nulliparous pregnant women (25 with BMI ≥ 30 and 25 with BMI < 25) were recruited at the beginning of the study and 39 completed the entire study. Basal tone (BT) was 4.62 ± 0.24 Nw at the beginning of pregnancy and decreased to 4.18 ± 0.26 Nw after delivery. Contractile capacity was 5.56 ± 0.79 Nw at week 12 and increased to 6.34 ± 1.24 Nw after delivery. When comparing the FCMax at week 12 in obese VS normal weight pregnant women, values of 5.51 ± 87 Nw vs. 5.61 ± 0.71 Nw were observed (p = 0.941). Postpartum values were 6.72 ± 1.17 Nw vs 5.95 ± 1.21 Nw (p = 0.024), higher in the obese population.

CONCLUSIONS

There is an increase in contractile strength (Fmax) at 12 weeks postpartum in order to counteract the significant decrease in basal tone (BT). The body has compensatory mechanisms that allow recovery after 3 months postpartum, with greater muscle strength in obese patients.

In vivo assessment of the elastic properties of the external anal sphincter in term pregnant women using shear wave elastography

INTRODUCTION AND HYPOTHESIS

The objective was to assess the intraobserver intersession and interobserver intrasession reliability of shear wave elastography applied to the external anal sphincter in term pregnant women.

METHODS

This prospective study involved nulliparous pregnant women at 37 weeks or more with two visits (V1: one observer; V2 two observers) planned within a 12-h to 7-day interval. Measurements were performed using an Aixplorer V12® device with an SL 18-5 linear probe using a transperineal approach, allowing a measurement of the shear modulus (SM) in kPa. Measures were performed at rest, Valsalva maneuver, and maximal contraction. Reliability was assessed using the intraclass correlation coefficient (ICC). The study was approved by an ethics committee (ID RCB: 2020-A00764-65).

RESULTS

A total of 37 women were included. Intraobserver reliability was excellent at rest (ICC = 0.91 [0.84-0.95) and good during the Valsalva maneuver (ICC = 0.83 [0.72-0.90]) and contraction (ICC = 0.85 [0.75-0.91]). Interobserver reliability was good at rest (ICC = 0.79 [0.66-0.87]) and during Valsalva (ICC = 0.84 [0.73-0.90]), but moderate during contraction (ICC = 0.70 [0.53-0.82]).

CONCLUSIONS

Shear wave elastography is a reliable tool for assessing the elastic properties of the external anal sphincter in term pregnant women.

Morphological Variation in the Pelvic Floor Muscle Complex of Nulliparous, Pregnant, and Parous Women

Specific levator ani muscle imaging measures change with pregnancy and vaginal parity, though entire pelvic floor muscle complex (PFMC) shape variation related to pregnancy-induced and postpartum remodeling has never been quantified. We used statistical shape modeling to compute the 3D variation in PFMC morphology of reproductive-aged nulliparous, late pregnant, and parous women. Pelvic magnetic resonance images were collected retrospectively and PFMCs were segmented. Modes of variation and principal component scores, generated via statistical shape modeling, defined significant morphological variation. Nulliparous (have never given birth), late pregnant (3rd trimester), and parous (have given birth and not currently pregnant) PFMCs were compared via MANCOVA. The overall PFMC shape, mode 2, and mode 3 significantly differed across patient groups (p < 0.001, = 0.002, = 0.001, respectively). This statistical shape analysis described greater perineal and external anal sphincter descent, increased iliococcygeus concavity, and a proportionally wider mid-posterior levator hiatus in late pregnant compared to nulliparous and parous women. The late pregnant group was the most divergent, highlighting differences that likely reduce the mechanical burden of vaginal childbirth. This robust quantification of PFMC shape provides insight to pregnancy and postpartum remodeling and allows for generation of representative non-patient-specific PFMCs that can be used in biomechanical simulations.

Effects of the Oxytocin Hormone on Pelvic Floor Muscles in Pregnant Rats

Background and Objectives: Oxytocin induction is a known risk factor for pelvic floor disorders (PFDs). The aim of the study was to investigate the effects of oxytocin induction on pelvic floor muscles in pregnant rats. Methods: Thirty-two female Wistar rats were included and divided into four groups (n = 8). The groups were as follows: virgin group (group I)-from which muscles were dissected at the beginning of the experiment; spontaneous vaginal delivery (group II) which has delivery spontaneously; saline control group (group III) and oxytocin group (group IV). In groups III and IV, pregnancy was induced on d 21 of pregnancy, with 2.5 mU saline solution or iv oxytocin, respectively, delivered by the intravenous (iv) route in pulses at 10-min intervals for 8 h. Then, the rats were euthanized, the m. coccygeus, m. iliocaudalis and m. pubocaudalis muscles were excised and tissue samples were taken. After histological processing, the vertical and horizontal dimensions of the muscles were analyzed under a light microscope. Results: In group IV; the measurement of the horizontal dimension of the m. pubocaudalis muscles was 50.1 ± 5.4 µm and it was significantly higher than other groups (p < 0.001). In group III; the mean value of the horizontal dimension of m. coccygeus muscle was found to be 49.5 ± 10.9 µm and it was significantly higher than other groups (p < 0.009). Between-group comparisons revealed no difference in mean m. iliocaudalis muscle dimension (p > 0.05). Conclusions: As a result of our study it can say that whether oxytocin induced or not, vaginal birth is a process that affects the pelvic muscles.

Biaxial Murine Vaginal Remodeling With Reproductive Aging

Higher reproductive age is associated with an increased risk of gestational diabetes, pre-eclampsia, and severe vaginal tearing during delivery. Further, menopause is associated with vaginal stiffening. However, the mechanical properties of the vagina during reproductive aging before the onset of menopause are unknown. Therefore, the first objective of this study was to quantify the biaxial mechanical properties of the nulliparous murine vagina with reproductive aging. Menopause is further associated with a decrease in elastic fiber content, which may contribute to vaginal stiffening. Hence, our second objective was to determine the effect of elastic fiber disruption on the biaxial vaginal mechanical properties. To accomplish this, vaginal samples from CD-1 mice aged 2-14 months underwent extension-inflation testing protocols (n = 64 total; n = 16/age group). Then, half of the samples were randomly allocated to undergo elastic fiber fragmentation via elastase digestion (n = 32 total; 8/age group) to evaluate the role of elastic fibers. The material stiffness increased with reproductive age in both the circumferential and axial directions within the control and elastase-treated vaginas. The vagina demonstrated anisotropic mechanical behavior, and anisotropy increased with age. In summary, vaginal remodeling with reproductive age included increased direction-dependent material stiffness, which further increased following elastic fiber disruption. Further work is needed to quantify vaginal remodeling during pregnancy and postpartum with reproductive aging to better understand how age-related vaginal remodeling may contribute to an increased risk of vaginal tearing.

Reversal of diabetic-induced myopathy by swimming exercise in pregnant rats: a translational intervention study

Gestational diabetes mellitus (GDM) plus rectus abdominis muscle (RAM) myopathy predicts long-term urinary incontinence (UI). Atrophic and stiff RAM are characteristics of diabetes-induced myopathy (DiM) in pregnant rats. This study aimed to determine whether swimming exercise (SE) has a therapeutic effect in mild hyperglycemic pregnant rats model. We hypothesized that SE training might help to reverse RAM DiM. Mild hyperglycemic pregnant rats model was obtained by a unique subcutaneous injection of 100 mg/kg streptozotocin (diabetic group) or citrate buffer (non-diabetic group) on the first day of life in Wistar female newborns. At 90 days of life, the rats are mated and randomly allocated to remain sedentary or subjected to a SE protocol. The SE protocol started at gestational day 0 and consisted of 60 min/day for 6 days/week in a period of 20 days in a swim tunnel. On day 21, rats were sacrificed, and RAM was collected and studied by picrosirius red, immunohistochemistry, and transmission electron microscopy. The SE protocol increased the fiber area and diameter, and the slow-twitch and fast-twitch fiber area and diameter in the diabetic exercised group, a finding was also seen in control sedentary animals. There was a decreased type I collagen but not type III collagen area and showed a similar type I/type III ratio compared with the control sedentary group. In conclusion, SE during pregnancy reversed the RAM DiM in pregnant rats. These findings may be a potential protocol to consider in patients with RAM damage caused by GDM.

Mechanisms governing protective pregnancy-induced adaptations of the pelvic floor muscles in the rat preclinical model

BACKGROUND

The intrinsic properties of pelvic soft tissues in women who do and do not sustain birth injuries are likely divergent. However, little is known about this. Rat pelvic floor muscles undergo protective pregnancy-induced structural adaptations-sarcomerogenesis and increase in intramuscular collagen content-that protect against birth injury.

OBJECTIVE

We aimed to test the following hypotheses: (1) the increased mechanical load of a gravid uterus drives antepartum adaptations; (2) load-induced changes are sufficient to protect pelvic muscles from birth injury.

STUDY DESIGN

The independent effects of load uncoupled from the hormonal milieu of pregnancy were tested in 3- to 4-month-old Sprague-Dawley rats randomly divided into the following 4 groups, with N of 5 to 14 per group: (1) load-/pregnancy hormones- (controls), (2) load+/pregnancy hormones-, (3) reduced load/pregnancy hormones+, and (4) load+/pregnancy hormones+. Mechanical load of a gravid uterus was simulated by weighing uterine horns with beads similar to fetal rat size and weight. A reduced load was achieved by unilateral pregnancy after unilateral uterine horn ligation. To assess the acute and chronic phases required for sarcomerogenesis, the rats were sacrificed at 4 hours or 21 days after bead loading. The coccygeus, iliocaudalis, pubocaudalis, and nonpelvic tibialis anterior musles were harvested for myofiber and sarcomere length measurements. The intramuscular collagen content was assessed using a hydroxyproline assay. An additional 20 load+/pregnancy hormones- rats underwent vaginal distention to determine whether the load-induced changes are sufficient to protect from mechanical muscle injury in response to parturition-associated strains of various magnitude. The data, compared using 2-way repeated measures analysis of variance followed by pairwise comparisons, are presented as mean±standard error of mean.

RESULTS

An acute increase in load resulted in significant pelvic floor muscle stretch, accompanied by an acute increase in sarcomere length compared with nonloaded control muscles (coccygeus: 2.69±0.03 vs 2.30±0.06 μm, respectively, P<.001; pubocaudalis: 2.71±0.04 vs 2.25±0.03 μm, respectively, P<.0001; and iliocaudalis: 2.80±0.06 vs 2.35±0.04 μm, respectively, P<.0001). After 21 days of sustained load, the sarcomeres returned to operational length in all pelvic muscles (P>.05). However, the myofibers remained significantly longer in the load+/pregnancy hormones- than the load-/pregnancy hormones- in coccygeus (13.33±0.94 vs 9.97±0.26 mm, respectively, P<.0001) and pubocaudalis (21.20±0.52 vs 19.52±0.34 mm, respectively, P<.04) and not different from load+/pregnancy hormones+ (12.82±0.30 and 22.53±0.32 mm, respectively, P>.1), indicating that sustained load-induced sarcomerogenesis in these muscles. The intramuscular collagen content in the load+/pregnancy hormones- group was significantly greater relative to the controls in coccygeus (6.55±0.85 vs 3.11±0.47 μg/mg, respectively, P<.001) and pubocaudalis (5.93±0.79 vs 3.46±0.52 μg/mg, respectively, P<.05) and not different from load+/pregnancy hormones+ (7.45±0.65 and 6.05±0.62 μg/mg, respectively, P>.5). The iliocaudalis required both mechanical and endocrine cues for sarcomerogenesis. The tibialis anterior was not affected by mechanical or endocrine alterations. Despite an equivalent extent of adaptations, load-induced changes were only partially protective against sarcomere hyperelongation.

CONCLUSION

Load induces plasticity of the intrinsic pelvic floor muscle components, which renders protection against mechanical birth injury. The protective effect, which varies between the individual muscles and strain magnitudes, is further augmented by the presence of pregnancy hormones. Maximizing the impact of mechanical load on the pelvic floor muscles during pregnancy, such as with specialized pelvic floor muscle stretching regimens, is a potentially actionable target for augmenting pregnancy-induced adaptations to decrease birth injury in women who may otherwise have incomplete antepartum muscle adaptations.

Aging of Pelvic Floor in Animal Models: A Sistematic Review of Literature on the Role of the Extracellular Matrix in the Development of Pelvic Floor Prolapse

Pelvic organ prolapse (POP) affects many women and contributes significantly to a decrease in their quality of life causing urinary and/or fecal incontinence, sexual dysfunction and dyspareunia. To better understand POP pathophysiology, prevention and treatment, many researchers resorted to evaluating animal models. Regarding this example and because POP affects principally older women, our aim was to provide an overview of literature on the possible biomechanical changes that occur in the vaginas of animal models and their supportive structures as a consequence of aging. Papers published online from 2000 until May 2021 were considered and particular attention was given to articles reporting the effects of aging on the microscopic structure of the vagina and pelvic ligaments in animal models. Most research has been conducted on rodents because their vagina structure is well characterized and similar to those of humans; furthermore, they are cost effective. The main findings concern protein structures of the connective tissue, known as elastin and collagen. We have noticed a significant discordance regarding the quantitative changes in elastin and collagen related to aging, especially because it is difficult to detect them in animal specimens. However, it seems to be clear that aging affects the qualitative properties of elastin and collagen leading to aberrant forms which may affect the elasticity and the resilience of tissues leading to pelvic floor disease. The analysis of histological changes of pelvic floor tissues related to aging underlines how these topics appear to be not fully understood so far and that more research is necessary.

Pelvic floor muscle dysfunction at 3D transperineal ultrasound in maternal exposure to gestational diabetes mellitus: A prospective cohort study during pregnancy

AIM

This study aimed to assess, for the first time, the dynamic morphometry of pelvic floor muscles (PFM) using three-dimensional transperineal ultrasound (3D-TPUS) and its progression at two-time points of gestation between women with and without gestational diabetes mellitus (GDM), and whether the PFM dysfunction is connected to GDM.

METHODS

The study comprised 83 consecutive pregnant women with (n = 38) and without (n = 45) GDM screened at 24-30 and 38-40 weeks of gestation. 3D-TPUS and a mobility test were used to quantify PFM dynamic morphometry during maximum contraction and the Valsalva maneuver.

RESULTS

When compared to the control group, GDM women had no significant variations in all levator hiatal dimensions at 24-30 weeks of gestation. Meanwhile, women with GDM experienced an increase in levator hiatal area (LHa) (p < 0.000) during PFM contraction and enlargement in LHa (p < 0.001) during Valsalva maneuver (p = 0.010) at 38-40 weeks of gestation. As a result, the mobility index among GDM women had a lower value (p = 0.000). The dynamic morphometry development of PFM in GDM women at two stages during pregnancy revealed a substantial decrease (p = 0.000) in all LHa dimensions of contraction, distension, and mobility.

CONCLUSIONS

Using 3D-TPUS, we found that GDM women had a specific pattern of PFM functional changes in the third trimester of pregnancy. These initial findings revealed alterations in PFM functionality, such as decreased contractility, distensibility, or mobility. This dysfunctional PFM could contribute to the long-term development of pelvic floor dysfunction years after a GDM pregnancy.

International Urogynecological Consultation (IUC): pathophysiology of pelvic organ prolapse (POP)

INTRODUCTION AND HYPOTHESIS

This manuscript is the International Urogynecology Consultation (IUC) on pelvic organ prolapse (POP) chapter one, committee three, on the Pathophysiology of Pelvic Organ Prolapse assessing genetics, pregnancy, labor and delivery, age and menopause and animal models.

MATERIALS AND METHODS

An international group of urogynecologists and basic scientists performed comprehensive literature searches using pre-specified terms in selected biomedical databases to summarize the current knowledge on the pathophysiology of the development of POP, exploring specifically factors including (1) genetics, (2) pregnancy, labor and delivery, (3) age and menopause and (4) non-genetic animal models. This manuscript represents the summary of three systematic reviews with meta-analyses and one narrative review, to which a basic scientific comment on the current understanding of pathophysiologic mechanisms was added.

RESULTS

The original searches revealed over 15,000 manuscripts and abstracts which were screened, resulting in 202 manuscripts that were ultimately used. In the area of genetics the DNA polymorphisms rs2228480 at the ESR1 gene, rs12589592 at the FBLN5 gene, rs1036819 at the PGR gene and rs1800215 at the COL1A1 gene are significantly associated to POP. In the area of pregnancy, labor and delivery, the analysis confirmed a strong etiologic link between vaginal birth and symptoms of POP, with the first vaginal delivery (OR: 2.65; 95% CI: 1.81-3.88) and forceps delivery (OR: 2.51; 95% CI: 1.24-3.83) being the main determinants. Regarding age and menopause, only age was identified as a risk factor (OR : 1.102; 95% CI: 1.02-1.19) but current data do not identify postmenopausal status as being statistically associated with POP. In several animal models, there are measurable effects of pregnancy, delivery and iatrogenic menopause on the structure/function of vaginal support components, though not on the development of POP.

CONCLUSIONS

Genetics, vaginal birth and age all have a strong etiologic link to the development of POP, to which other factors may add or protect against the risk.

Pelvic floor shape variations during pregnancy and after vaginal delivery

BACKGROUND AND OBJECTIVE

Strong evidence suggests that pelvic soft tissues soften during pregnancy to facilitate vaginal delivery while protecting against maternal birth injury. We hypothesized that these adaptations likely result in changes to the shape of the pelvic floor. Thus, this study aimed to compare midsagittal pelvic floor shapes from MRIs of nulliparous, gravid, and vaginally parous women using statistical shape modeling.

METHODS

A retrospective study of 22 nulliparous, 29 gravid (vaginally nulliparous), and 18 vaginally parous women who underwent pelvic MRI was performed. The pelvic floor was segmented from pubic symphysis to coccyx as a 2D polyline in the midsagittal plane. Once corresponding landmarks were computed and the variances between them determined by principal component analysis, the principal component scores were calculated for modes that explained variance greater than noise. These became the dependent variables in a MANOVA with univariate ANOVAs, linear regressions, and Benjamini-Hochberg corrections post hoc. Two initial statistical shape analyses were conducted to analyze differences based on gestational age (1^st/2^nd vs 3^rd trimester) and vaginal parity (VP1 vs VP2-4). There were significant differences based on gestational age, but not vaginal parity. Thus, the final statistical shape analysis evaluated pelvic floor shapes of nulliparous, 3rd trimester gravid, and all vaginally parous subjects.

RESULTS

In the final analysis, six modes described variance-a measure of shape variability-greater than noise. Groups differed significantly for modes 1, 2, and 4 (p < 0.001, p = 0.021, and p = 0.015, respectively) and only differed between the nulliparous and gravid groups (p < 0.001, p = 0.018, and p = 0.012, respectively). Anatomically, these modes described levator plate relaxation and level III support protrusion in gravid compared to nulliparous subjects while the parous group straddled the other two.

CONCLUSIONS

The shape of the pelvic floor changes significantly during pregnancy and some of those changes are present after vaginal delivery. The fact that the nulliparous and gravid groups differ while the parous is similar to both suggests that some parous women regain their nulliparous shape after pregnancy and delivery while others do not. This indicates that remodeling during pregnancy and/or injury during vaginal delivery can have lasting effects on the pelvic floor.

In vivo assessment of the elastic properties of women's pelvic floor during pregnancy using shear wave elastography: design and protocol of the ELASTOPELV study

Background

Animal studies have reported an increase in pelvic floor muscle stiffness during pregnancy, which might be a protective process against perineal trauma at delivery. Our main objective is to describe the changes in the elastic properties of the pelvic floor muscles (levator ani, external anal sphincter) during human pregnancy using shear wave elastography (SWE) technology. Secondary objectives are as follows: i) to look for specific changes of the pelvic floor muscles compared to peripheral muscles; ii) to determine whether an association between the elastic properties of the levator ani and perineal clinical and B-mode ultrasound measures exists; and iii) to provide explorative data about an association between pelvic floor muscle characteristics and the risk of perineal tears.

Methods

Our prospective monocentric study will involve three visits (14–18, 24–28, and 34–38 weeks of pregnancy) and include nulliparous women older than 18 years, with a normal pregnancy and a body mass index (BMI) lower than 35 kg.m^− 2. Each visit will consist of a clinical pelvic floor assessment (using the Pelvic Organ Prolapse Quantification system), an ultrasound perineal measure of the anteroposterior hiatal diameter and SWE assessment of the levator ani and the external anal sphincter muscles (at rest, during the Valsalva maneuver and during pelvic floor contraction), and SWE assessment of both the biceps brachii and the gastrocnemius medialis (at rest, extension and contraction). We will collect data about the mode of delivery and the occurrence of perineal tears. We will investigate changes in continuous variables collected using the Friedman test. We will look for an association between the elastic properties of the levator ani muscle and clinical / ultrasound measures using a Spearman test at each trimester. We will investigate the association between the elastic properties of the pelvic floor muscles and perineal tear occurrence using a multivariate analysis with logistic regression.

Discussion

This study will provide original in vivo human data about the biomechanical changes of pregnant women’s pelvic floor. The results may lead to an individualized risk assessment of perineal trauma at childbirth.

Trial registration

This study was registered on https://clinicaltrials.gov on July 26, 2018 (NCT03602196).

The importance of developing relevant animal models to assess existing and new materials

PURPOSE OF REVIEW

We summarize the recent literature on the use of different animal models for testing existing and new materials for treatment of pelvic organ prolapse.

RECENT FINDINGS

A wide spectrum of animal models is being used in urogynecology, both for the study of physiologic and pathophysiologic processes, training in surgical procedures, yet mainly to study the host response to implant materials. The quality of studies is variable, and procedures, read-outs, and reporting are not standardized. This makes comparison very difficult. The research community is experimenting with different knitting patterns, novel polymers, bioactivation, as well as resorbable rather than durable implants. Outcomes of the experiments are dependent on the location of implantation. Lighter polypropylene constructs seem to induce a less vigorous host response than elder heavier products. Modification of the surface yields contradictory findings. Resorbable acellular collagen matrices may be reintroduced as prophylactically inserted support structures.

SUMMARY

Although animal experimentation with novel candidate implants is advocated, there is a lack of standardization in reporting. The concept of resorbable construct is being revived, as durable materials have caused clinical graft-related complications. Large animal experiments seem to provide interesting and more comprehensive information, yet their use may be contested.

Exosomes Could Offer New Options to Combat the Long-Term Complications Inflicted by Gestational Diabetes Mellitus

Gestational diabetes Mellitus (GDM) is a complex clinical condition that promotes pelvic floor myopathy, thus predisposing sufferers to urinary incontinence (UI). GDM usually regresses after birth. Nonetheless, a GDM history is associated with higher risk of subsequently developing type 2 diabetes, cardiovascular diseases (CVD) and UI. Some aspects of the pathophysiology of GDM remain unclear and the associated pathologies (outcomes) are poorly addressed, simultaneously raising public health costs and diminishing women's quality of life. Exosomes are small extracellular vesicles produced and actively secreted by cells as part of their intercellular communication system. Exosomes are heterogenous in their cargo and depending on the cell sources and environment, they can mediate both pathogenetic and therapeutic functions. With the advancement in knowledge of exosomes, new perspectives have emerged to support the mechanistic understanding, prediction/diagnosis and ultimately, treatment of the post-GMD outcomes. Here, we will review recent advances in knowledge of the role of exosomes in GDM and related areas and discuss the possibilities for translating exosomes as therapeutic agents in the GDM clinical setting.

Study protocol to investigate biomolecular muscle profile as predictors of long-term urinary incontinence in women with gestational diabetes mellitus

BACKGROUND

Pelvic floor muscles (PFM) and rectus abdominis muscles (RAM) of pregnant diabetic rats exhibit atrophy, co-localization of fast and slow fibers and an increased collagen type I/III ratio. However, the role of similar PFM or RAM hyperglycemic-related myopathy in women with gestational diabetes mellitus (GDM) remains poorly investigated. This study aims to assess the frequency of pelvic floor muscle disorders and pregnancy-specific urinary incontinence (PS-UI) 12 months after the Cesarean (C) section in women with GDM. Specifically, differences in PFM/RAM hyperglycemic myopathy will be evaluated.

METHODS

The Diamater is an ongoing cohort study of four groups of 59 pregnant women each from the Perinatal Diabetes Research Centre (PDRC), Botucatu Medical School (FMB)-UNESP (São Paulo State University), Brazil. Diagnosis of GDM and PS-UI will be made at 24-26 weeks, with a follow-up at 34-38 weeks of gestation. Inclusion in the study will occur at the time of C-section, and patients will be followed at 24-48 h, 6 weeks and 6 and 12 months postpartum. Study groups will be classified as (1) GDM plus PS-UI; (2) GDM without PS-UI; (3) Non-GDM plus PS-UI; and (4) Non-GDM without PS-UI. We will analyze relationships between GDM, PS-UI and hyperglycemic myopathy at 12 months after C-section. The mediator variables to be evaluated include digital palpation, vaginal squeeze pressure, 3D pelvic floor ultrasound, and 3D RAM ultrasound. RAM samples obtained during C-section will be analyzed for ex-vivo contractility, morphological, molecular and OMICS profiles to further characterize the hyperglycemic myopathy. Additional variables to be evaluated include maternal age, socioeconomic status, educational level, ethnicity, body mass index, weight gain during pregnancy, quality of glycemic control and insulin therapy.

DISCUSSION

To our knowledge, this will be the first study to provide data on the prevalence of PS-UI and RAM and PFM physical and biomolecular muscle profiles after C-section in mothers with GDM. The longitudinal design allows for the assessment of cause-effect relationships between GDM, PS-UI, and PFMs and RAMs myopathy. The findings may reveal previously undetermined consequences of GDM.

Bladder and urethral dysfunction in multiparous and mature rabbits correlates with abnormal activity of pubococcygeus and bulbospongiosus muscles

AIMS

To evaluate the combined effect of age and multiparity on the micturition reflex, including pelvic floor muscle activation.

METHODS

Young and mature nulliparous rabbits were compared to young and mature multiparas (n = 6 per group). Cystometrograms and urethral pressure (UP) were performed while simultaneously recording the electromyogram (EMG) activity of the pubococcygeus and bulbospongiosus muscles to establish their functional correlation to urological function.

RESULTS

Multiparity and age significantly influence the bladder and UP affecting the voiding efficiency and intercontraction interval. Such interaction also reduced the UP threshold, timing, and duration. Other bladder and urethral variables were predominantly affected only by age. Urodynamic alterations correlated with abnormal patterns or absent EMG activity of the pubococcygeus and bulbospongiosus muscles.

CONCLUSIONS

The present findings strongly suggest that multiparity and age affects specific pelvic floor muscle reflex activation during micturition, and may contribute to alterations in bladder and urethral function. This data broadens our understanding of the critical role of the appropriate activity of the individual pelvic floor muscles in micturition.

Age-associated changes in the mechanical properties of human cadaveric pelvic floor muscles

Proper function of the female pelvic floor requires intact pelvic floor muscles (PFMs). The prevalence of pelvic floor disorders (PFDs) increases substantially with age, in part due to clinically identified deterioration of PFM function with age. However, the etiology of this decline remains largely unknown. We previously demonstrated that PFMs undergo age-related fibrotic changes. This study sought to determine whether aging also impacts PFMs' passive mechanical properties that are largely determined by the intramuscular extracellular matrix. Biopsies from younger (≤52y) and older (>52y) female cadaveric donors were procured from PFMs, specifically coccygeus (C) and two portions of the levator ani - iliococcygeus (IC) and pubovisceralis (PV), and the appendicular muscles - obturator internus (OI) and vastus lateralis (VL). Muscle bundles were subjected to a passive loading protocol, and stress-sarcomere length (L_s) relationships calculated. Muscle stiffness was compared between groups using 2-way ANOVA and Sidak pairwise comparisons, α < 0.05. The mean age was 43.4 ± 11.6y and 74.9 ± 11.9y in younger (N = 5) and older (N = 10) donors, respectively. In all PFMs, the quadratic coefficient of parabolic regression of the stress-L_s curve, a measure of stiffness, was lower in the younger versus older group: C: 33.7 ± 13.9 vs 87.2 ± 10.7, P = 0.02; IC: 38.3 ± 12.7 vs 84.5 ± 13.9, P = 0.04; PV: 24.7 ± 8.8 vs 74.6 ± 9.6, P = 0.04. In contrast, non-PFM stiffness was not affected by aging: OI: 14.5 ± 4.7 vs 32.9 ± 6.2, P = 0.8 and VL: 13.6 ± 5.7 vs 30.1 ± 5.3, P = 0.9. Age-associated increase in PFM stiffness is predicted to negatively impact PFM function by diminishing muscle load-bearing, excursional, contractile, and regenerative capacity, thus predisposing older women to PFDs.

Uncovering changes in proteomic signature of rat pelvic floor muscles in pregnancy

BACKGROUND

Structural and functional changes of the rat pelvic floor muscles during pregnancy, specifically, sarcomerogenesis, increase in extracellular matrix content, and higher passive tension at larger strains protect the integral muscle components against birth injury. The mechanisms underlying these antepartum alterations are unknown. Quantitative proteomics is an unbiased method of identifying protein expression changes in differentially conditioned samples. Therefore, proteomics analysis provides an opportunity to identify molecular mechanisms underlying antepartum muscle plasticity.

OBJECTIVE

To elucidate putative mechanisms accountable for pregnancy-induced adaptations of the pelvic floor muscles, and to identify other novel antepartum alterations of the pelvic floor muscles.

MATERIALS AND METHODS

Pelvic floor muscles, comprised of coccygeus, iliocaudalis, and pubocaudalis, and nonpelvic limb muscle, tibialis anterior, were harvested from 3-month-old nonpregnant and late-pregnant Sprague-Dawley rats. After tissue homogenization, trypsin-digested peptides were analyzed by ultra-high-performance liquid chromatography coupled with tandem mass spectroscopy using nano-spray ionization. Peptide identification and label free relative quantification analysis were carried out using Peaks Studio 8.5 software (Bioinformatics Solutions Inc., Waterloo, ON, Canada). Proteomics data were visualized using the Qlucore Omics Explorer (New York, NY). Differentially expressed peptides were identified using the multi-group differential expression function, with q-value cutoff set at <0.05. Proteomic signatures of the pelvic floor muscles were compared to nonpelvic limb muscle and between nonpregnant and pregnant states.

RESULTS

Unsupervised clustering of the data showed clear separation between samples from nonpregnant and pregnant animals along principal component 1 and between pelvic and nonpelvic muscles along principal component 2. Four major gene clusters were identified segregating proteomic signatures of muscles examined in nonpregnant vs pregnant states: (1) proteins increased in the pelvic floor muscles only; (2) proteins increased in the pelvic floor muscles and tibialis anterior; (3) proteins decreased in the pelvic floor muscles and tibialis anterior; and (4) proteins decreased in the pelvic floor muscles alone. Cluster 1 included proteins involved in cell cycle progression and differentiation. Cluster 2 contained proteins that participate in mitochondrial metabolism. Cluster 3 included proteins involved in transcription, signal transduction, and phosphorylation. Cluster 4 comprised proteins involved in calcium-mediated regulation of muscle contraction via the troponin tropomyosin complex.

CONCLUSION

Pelvic floor muscles gain a distinct proteomic signature in pregnancy, which provides a mechanistic foundation for the antepartum physiological alterations acquired by these muscles. Variability in genes encoding these proteins may alter plasticity of the pelvic floor muscles and therefore the extent of the protective pregnancy-induced adaptations. Furthermore, pelvic floor muscles' proteome is divergent from that of the nonpelvic skeletal muscles.

Echogenicity of puborectalis muscle, cervix and vastus lateralis muscle in pregnancy in relation to mode of delivery

OBJECTIVES

To confirm our previous observation that levator hiatal dimensions and mean echogenicity of the puborectalis muscle (MEP) are significantly different at 12 weeks' gestation in women who delivered by Cesarean section due to failure to progress compared with those who delivered vaginally. The secondary objective was to assess the association between the echogenicity of the cervix and vastus lateralis muscle and mode of delivery.

METHODS

In this prospective multicenter study, 306 nulliparous women with a singleton pregnancy underwent ultrasound assessments of the pelvic floor at rest, on maximum pelvic floor muscle contraction and on maximum Valsalva maneuver, of the cervix and of the vastus lateralis muscle at 12 weeks' gestation. Dimensions of the levator hiatus, MEP and mean echogenicity of the cervix and vastus lateralis muscle were measured and compared according to mode of delivery.

RESULTS

Two hundred and forty-nine women were included in the analyses. We were unable to confirm our previous finding that MEP and levator hiatal transverse diameter and area at 12 weeks' gestation are associated significantly with mode of delivery. In addition, we could not demonstrate a significant association between echogenicity of the cervix or vastus lateralis muscle and mode of delivery. Overall, MEP was a mean of 20 points lower in women in the new database as compared with the previous study, despite the use of the same ultrasound equipment.

CONCLUSION

In a second, independent multicenter dataset, we were unable to confirm our previous finding that levator hiatal dimensions and MEP on pelvic floor muscle contraction are associated significantly with mode of delivery. We also found no association between echogenicity of the cervix or vastus lateralis and mode of delivery. Copyright © 2018 ISUOG. Published by John Wiley & Sons Ltd.

Multimodal imaging assessment and histologic correlation of the female rat pelvic floor muscles' anatomy

Pelvic floor disorders negatively impact millions of women worldwide. Although there is a strong epidemiological association with childbirth, the mechanisms leading to the dysfunction of the integral constituents of the female pelvic floor, including pelvic floor skeletal muscles, are not well understood. This is in part due to the constraints associated with directly probing these muscles, which are located deep in the pelvis. Thus, experimental models and non-invasive techniques are essential for advancing knowledge of various phenotypes of pelvic floor muscle injury and pathogenesis of muscle dysfunction, as well as developing minimally invasive approaches for the delivery of novel therapeutics. The most widely used animal model for pelvic floor disorders is the rat. However, the radiological anatomy of rat pelvic floor muscles has not been described. To remedy this gap, the current study provides the first detailed description of the female rat pelvic floor muscles' radiological appearance on MR and ultrasound images, validated by correlation with gross anatomy and histology. We also demonstrate that ultrasound guidance can be used to target rat pelvic floor muscles for possible interventional therapies.

The Role of Placental Hormones in Mediating Maternal Adaptations to Support Pregnancy and Lactation

During pregnancy, the mother must adapt her body systems to support nutrient and oxygen supply for growth of the baby in utero and during the subsequent lactation. These include changes in the cardiovascular, pulmonary, immune and metabolic systems of the mother. Failure to appropriately adjust maternal physiology to the pregnant state may result in pregnancy complications, including gestational diabetes and abnormal birth weight, which can further lead to a range of medically significant complications for the mother and baby. The placenta, which forms the functional interface separating the maternal and fetal circulations, is important for mediating adaptations in maternal physiology. It secretes a plethora of hormones into the maternal circulation which modulate her physiology and transfers the oxygen and nutrients available to the fetus for growth. Among these placental hormones, the prolactin-growth hormone family, steroids and neuropeptides play critical roles in driving maternal physiological adaptations during pregnancy. This review examines the changes that occur in maternal physiology in response to pregnancy and the significance of placental hormone production in mediating such changes.

Effect of Pregnancy and Delivery on Cytokine Expression in a Mouse Model of Pelvic Organ Prolapse

OBJECTIVES

The aim of this study was to determine the effect of pregnancy and delivery mode on cytokine expression in the pelvic organs and serum of lysyl oxidase like-1 knockout (LOXL1 KO) mice, which develop pelvic organ prolapse after delivery.

METHODS

Bladder, urethra, vagina, rectum, and blood were harvested from female LOXL1 KO mice during pregnancy, after vaginal or cesarean delivery, and from sham cesarean and unmanipulated controls. Pelvic organs and blood were also harvested from pregnant and vaginally delivered wild-type (WT) mice and from unmanipulated female virgin WT controls. Specimens were assessed using quantitative real-time reverse transcription polymerase chain reaction and/or enzyme-linked immunosorbent assay.

RESULTS

Both CXCL12 and CCL7 mRNA were significantly up-regulated in the vagina, urethra, bladder, and rectum of pregnant LOXL1 KO mice compared with pregnant WT mice, suggesting systemic dysregulation of both of these cytokines in LOXL1 KO mice as a response to pregnancy.The differences in cytokine expression between LOXL1 KO and WT mice in pregnancy persisted after vaginal delivery. CCL7 gene expression increases faster and to a greater extent in LOXL1 KO mice, translating to longer lasting increases in CCL7 in serum of LOXL1 KO mice after vaginal delivery, compared with pregnant mice.

CONCLUSIONS

Lysyl oxidase like-1 KO mice have an increased cytokine response to pregnancy perhaps because they are less able to reform and re-cross-link stretched elastin to accommodate pups, and this resultant tissue stretches during pregnancy. The up-regulation of CCL7 after delivery could provide an indicator of level of childbirth injury, to which the urethra and vagina seem to be particularly vulnerable.

Pelvic muscles' mechanical response to strains in the absence and presence of pregnancy-induced adaptations in a rat model

BACKGROUND

Maternal birth trauma to the pelvic floor muscles is thought to be consequent to mechanical demands placed on these muscles during fetal delivery that exceed muscle physiological limits. The above is consistent with studies of striated limb muscles that identify hyperelongation of sarcomeres, the functional muscle units, as the primary cause of mechanical muscle injury and resultant muscle dysfunction. However, pelvic floor muscles' mechanical response to strains have not been examined at a tissue level. Furthermore, we have previously demonstrated that during pregnancy, rat pelvic floor muscles acquire structural and functional adaptations in preparation for delivery, which likely protect against mechanical muscle injury by attenuating the strain effect.

OBJECTIVE

We sought to determine the mechanical impact of parturition-related strains on pelvic floor muscles' microstructure, and test the hypothesis that pregnancy-induced adaptations modulate muscle response to strains associated with vaginal delivery.

STUDY DESIGN

Three-month-old Sprague-Dawley late-pregnant (N = 20) and nonpregnant (N = 22) rats underwent vaginal distention, replicating fetal crowning, with variable distention volumes. Age-matched uninjured pregnant and nonpregnant rats served as respective controls. After sacrifice, pelvic floor muscles, which include coccygeus, iliocaudalis, and pubocaudalis, were fixed in situ and harvested for fiber and sarcomere length measurements. To ascertain the extent of physiological strains during spontaneous vaginal delivery, analogous measurements were obtained in intrapartum rats (N = 4) sacrificed during fetal delivery. Data were compared with repeated measures and 2-way analysis of variance, followed by pairwise comparisons, with significance set at P < .05.

RESULTS

Gross anatomic changes were observed in the pelvic floor muscles following vaginal distention, particularly in the entheseal region of pubocaudalis, which appeared translucent. The above appearance resulted from dramatic stretch of the myofibers, as indicated by significantly longer fiber length compared to controls. Stretch ratios, calculated as fiber length after vaginal distention divided by baseline fiber length, increased gradually with increasing distention volume. Paralleling these macroscopic changes, vaginal distention resulted in acute and progressive increase in sarcomere length with rising distention volume. The magnitude of strain effect varied by muscle, with the greatest sarcomere elongation observed in coccygeus, followed by pubocaudalis, and a smaller increase in iliocaudalis, observed only at higher distention volumes. The average fetal rat volume approximated 3 mL. Pelvic floor muscle sarcomere lengths in pregnant animals undergoing vaginal distention with 3 mL were similar to intrapartum sarcomere lengths in all muscles (P > .4), supporting the validity of our experimental approach. Vaginal distention resulted in dramatically longer sarcomere lengths in nonpregnant compared to pregnant animals, especially in coccygeus and pubocaudalis (P < .0001), indicating significant attenuation of sarcomere elongation in the presence of pregnancy-induced adaptations in pelvic floor muscles.

CONCLUSION

Delivery-related strains lead to acute sarcomere elongation, a well-established cause of mechanical injury in skeletal muscles. Sarcomere hyperelongation resultant from mechanical strains is attenuated by pregnancy-induced adaptations acquired by the pelvic floor muscles prior to parturition.

Structure-function relationship of the human external anal sphincter

INTRODUCTION AND HYPOTHESIS

Obstetrical external anal sphincter (EAS) injury and subsequent dysfunction are leading risk factors for female fecal incontinence (FI). Limited knowledge of the EAS structure-function relationship hinders treatment optimization. We directly measured functionally relevant intrinsic parameters of human EAS and tested whether vaginal delivery alters the EAS structure-function relationship.

METHODS

Major predictors of in vivo EAS function were compared between specimens procured from vaginally nulliparous (VN, n = 5) and vaginally parous (VP, n = 7) cadaveric donors: operational sarcomere length (Ls), which dictates force-length relationship; physiological cross-sectional area (PCSA), which determines isometric force-generating capacity; fiber length (Lfn), responsible for muscle excursion and contractile velocity; and muscle stiffness. Data were analyzed using unpaired and paired t tests, α < 0.05. Results are presented as mean ± SEM.

RESULTS

The VN and VP (median parity 3) groups were similar in age and BMI. No gross anatomical defects were identified. EAS Ls (2.36 ± 0.05 μm) was shorter than the optimal Lso (2.7 μm), at which contractile force is maximal, P = 0.0001. Stiffness was lower at Ls than Lso (5.4 ± 14 kPa/μm vs 35.3 ± 12 kPa/μm, P < 0.0001). This structural design allows active and passive tension to increase with EAS stretching. EAS relatively long Lfn (106 ± 24.8 mm) permits rapid contraction without decreased force, whereas intermediate PCSA (1.3 ± 0.3 cm2) is conducive to maintaining resting tone. All parameters were similar between groups.

CONCLUSIONS

This first direct examination of human EAS underscores how EAS intrinsic design matches its intended function. Knowledge of the EAS structure-function relationship is important for understanding the pathogenesis of FI and the optimization of treatments for EAS dysfunction.

Is increased peripheral ligamentous laxity in term pregnant women associated with obstetric anal sphincter injury?

INTRODUCTION AND HYPOTHESIS

Increased ligamentous laxity is associated with pelvic floor distension in pregnant women. This considered, it may also be related to the risk of obstetric anal sphincter injury (OASI). Our objective was to assess the association among increased ligamentous laxity, perineal tear severity, and OASI occurrence.

METHODS

This is a prospective study. We assessed ligamentous laxity between the 36th week of pregnancy and the onset of labor, by measuring the passive extension of the nondominant index finger for a 0.26 N.m torque applied to the second metacarpophalangeal joint (MCP laxity). We collected perineal tear occurrence and classification (Royal College of Obstetricians and Gynecologists). We investigated the MCP laxity distribution according to the stage of perineal tears, and then we looked for a predictive level of MCP laxity for OASI.

RESULTS

A total of 272 of the 300 pregnant women included had a vaginal delivery and were considered for the analysis. Mean age was 29 years, mean body mass index was 24.5 kg/m² and 39.2% of women were nulliparous. We reported 12 cases of OASI. MCP laxity significantly increased with the stage of perineal tears from 58° in stage 0 to 69° and 66° for stages 3a and 3b respectively. An MCP laxity higher than 64° was associated with OASI with sensitivity of 75%, specificity of 56%, and an area under the curve of 0.65.

CONCLUSION

Increased ligamentous laxity seems associated with OASI occurrence, which is the opposite of the initial hypothesis. This suggests that the stiffest tissues might be at a lower risk of injury.

Morphological changes in rat rectus abdominis muscle induced by diabetes and pregnancy

The urethral muscle of diabetic pregnant rats is affected by long-term mild diabetes and short-term severe diabetes, which plays a crucial role in the pathogenesis of pelvic floor disorders. We hypothesized that muscles outside the pelvis are subject to similar changes. The current study aimed at analyzing the effects of long-term mild and short-term severe diabetes on the structure and ultrastructure of fiber muscles and collagen in rats' rectus abdominis (RA) muscle. Therefore, the RA muscle of virgin, pregnant, long-term mild diabetic, short-term severe diabetic, long-term mild diabetic pregnant and short-term severe diabetic pregnant 3-month-old Wistar rats were collected. The structure was analyzed by picrosirius red staining, immunohistochemistry for fast and slow muscle fibers and transmission electron microscopy. We investigated two levels of STZ- induced diabetes: long-term mild diabetes (blood glucose level: 120–200 mg/dL) and short-term severe diabetes (blood glucose level >300 mg/dL). Long-term mild diabetic pregnant and short-term severe diabetic pregnant rats had decreased fast fibers and increased slow fibers, disrupted areas of sarcomere, intermyofibrillar mitochondria and myelin figures in the RA muscle. Both groups enabled us to analyze the specific influence of pregnancy, separately from diabetes. The current study demonstrated that diabetes and pregnancy induced intramuscular transformation and reorganization of RA muscle with a switch of fiber type adjusting their architecture according to intensity and duration of hyperglycemic insult within pregnancy.

[Anal incontinence and obstetrical anal sphincter injuries, epidemiology and prevention]

Our main objectives were to identify risk factors, methods for early diagnosis, and prevention of obstetric anal sphincter injuries (OASIs), using a literature review. The main risk factors for OASIs are nulliparity, instrumental delivery, posterior presentation, median episiotomy, prolonged second phase of labor and fetal macrosomia. Asian origin, short ano-vulvar distance, ligamentous hyperlaxity, lack of expulsion control, non-visualization of the perineum or maneuvers for shoulder dystocia also appear to be risk factors. There is a risk of under-diagnosis of OASIs in the labor ward. Experience of the accoucheur is a protective factor. Secondary prevention is based on the training of birth professionals in recognition and repair of OASIs. Primary prevention of OASIs is based on training in the maneuvers of the second phase of labor; if possible, instrumental extractions should be avoided. Mediolateral episiotomy may have a preventive role in high-risk OASIs deliveries. A robust predictive model is still lacking to allow a selective use of episiotomy.

The influence of hyperglycemia on the remodeling of urethral connective tissue in pregnant rats

OBJECTIVE

To analyze the distribution and quantification of the key structural extracellular matrix components of the urethral tissue in a rat model of hyperglycemia and pregnancy.

STUDY DESIGN

A total of 120 female Wistar rats were distributed into the following four experimental groups: virgin, pregnant, hyperglycemic and hyperglycemic + pregnant groups. The urethra was harvested for histochemical, morphometric, immunohistochemical, Western blot and glycosaminoglycan analyses. All protocols were approved by the Institutional Animal Care and Use Committee of Botucatu Medical School (process number 828-2010).

RESULTS

The hyperglycemic + pregnant group showed significantly increased stiffness in urethral tissue. The total striated muscle was decreased, with increased deposition of collagen fibers around the muscle fibers and a change in the organization of the collagen fibrils. An increase in the relative collagen type I/III ratio and a decrease in total glycosaminoglycans were also observed.

CONCLUSIONS

This study provides the first line of experimental evidence supporting a metabolic relationship between hyperglycemia and urethral remodeling of connective tissue in pregnant rats. The different organization of the collagen fibrils and the profile of glycosaminoglycans found in urethral samples suggest that the pathology of the urethral fibromuscular system could be related to hyperglycemia-induced pelvic floor dysfunction in women, which has direct clinical implications with the possibility to develop new multidisciplinary treatments for improving the health care of these women.

Multiparity modifies contractile properties of pelvic muscles affecting the genesis of vaginal pressure in rabbits

AIMS

To characterize the contractile properties of the bulbospongiosus (Bsm), isquiocavernosus (Ism), and pubococcygeus muscles (Pcm), and their involvement in the genesis of vaginal pressure in nulliparous and multiparous rabbits.

METHODS

Age-matched nulliparous and multiparous rabbits were used to record the isometric contractile responses of each muscle as well as the intravaginal pressure evoked by single square electrical pulses and stimulation trains of ascending frequency. To establish significant differences between groups, two-tail unpaired Student t tests were carried out. The linear correlation between intravaginal pressure and muscle contractile force was analyzed with Pearson correlation tests. For all cases, a P ≤ 0.05 was set as statistically significant.

RESULTS

Multiparity decreased the contractile force of Bsm and Ism generated by high-frequency stimulation trains. The normalized force of the Pcm increased when evoked at 1, 4, and 10 Hz while this decreased at higher frequencies (20, 50, and 100 Hz). The contraction of both Bsm and Ism raised particularly the pressure on the perineal vagina while that of the Pcm increased the pressure in the pelvic vagina. Such a functional segregation is still present in multiparous rabbits albeit it was modified.

CONCLUSIONS

Multiparity induces changes in the contractile responses of Bsm, Ism, and Pcm, which alterates the vaginal pressure.

Female pelvic floor biomechanics: bridging the gap

PURPOSE OF REVIEW

The pelvic floor is a complex assembly of connective tissues and striated muscles that simultaneously counteracts gravitational forces, inertial forces, and intra-abdominal pressures while maintaining the position of the pelvic organs. In 30% of women, injury or failure of the pelvic floor results in pelvic organ prolapse. Surgical treatments have high recurrence rates, due, in part, to a limited understanding of physiologic loading conditions. It is critical to apply biomechanics to help elucidate how altered loading conditions of the pelvis contribute to the development of pelvic organ prolapse and to define surgeries to restore normal support.

RECENT FINDINGS

Evidence suggests the ewe is a potential animal model for studying vaginal properties and that uterosacral and cardinal ligaments experience significant creep, which may be affecting surgical outcomes. A new method of measuring ligament displacements in vivo was developed, and finite element models that simulate urethral support, pelvic floor dynamics, and the impact of episiotomies on the pelvic floor were studied.

SUMMARY

The current review highlights some contributions over the past year, including mechanical testing and the creation of models, which are used to understand pelvic floor changes with loading and the impact of surgical procedures, to illustrate how biomechanics is being utilized.

Is levator hiatus distension associated with peripheral ligamentous laxity during pregnancy?

INTRODUCTION AND HYPOTHESIS

The impact of pregnancy on pelvic floor disorders remains poorly understood. During pregnancy, an increase in ligamentous laxity and pelvic organ mobility is often reported. Our main objective was to investigate a possible association between peripheral ligamentous laxity and levator hiatus (LH) distension during pregnancy.

METHODS

This was a prospective longitudinal study of 26 pregnant women followed up from the first to the third trimester. We collected the following information: occurrence of pelvic organ prolapse (POP) symptoms (score higher than 0 for the POP section of the Pelvic Floor Distress Inventory 20 questions score), 4D perineal ultrasound scan results with LH distension assessment and measurement of metacarpophalangeal joint mobility (MCP laxity). The association between MCP laxity and LH distension was estimated by mixed multilevel linear regression. The associations between MCP laxity and categorical parameters were estimated in a multivariate analysis using a generalized estimating equation model.

RESULTS

MCP laxity and LH distension were correlated with a correlation coefficient of 0.26 (p = 0.02), and 6.8% of the LH distension variance was explained by MCP laxity. In the multivariate analysis, MCP laxity was associated with POP symptoms with an odds ratio at 1.05 (95% CI 1.01-1.11) for an increase of 1° in MCP laxity.

CONCLUSION

LH distension and peripheral ligamentous laxity are significantly associated during pregnancy. However, the relationship is weak, and the results need to be confirmed in larger populations and with more specific techniques such as elastography to directly assess the elastic properties of the pelvic floor muscles.