Relationships between mechanical properties and extracellular matrix constituents of the cervical stroma during pregnancy

First trimester cervical angles for the prediction of spontaneous preterm birth

OBJECTIVE

First trimester cervical angles for the prediction of spontaneous preterm birth (sPTB) remains unclear. The objective is to explore the potential value of first trimester cervical angles for the prediction of sPTB.

STUDY DESIGN

This was a secondary analysis of data derived from a prospective cohort study for sPTB screening in singleton pregnancies at 11 + 0-13 + 6 weeks in women attending routine Down's syndrome screening at Prince of Wales Hospital, Hong Kong SAR, between June 2018 and July 2020.

METHODS

Using archived images of the sagittal view of the cervix, eight types of cervical angles were measured: Angle-A (two lines crossing the greatest curvature of cervix); Angle-B (isthmus and endocervical canal); Angle-C1 (anterior wall and cervix including isthmus); Angle-C2 (anterior wall and endocervical canal); Angle-D1 (posterior wall and cervix including isthmus); Angle-D2 (posterior wall and endocervical canal); Angle-E (anterior wall and isthmus); Angle-F (posterior wall and isthmus). Likelihood ratios for cervical angle multiples of the median (MoMs) were computed and combined together with maternal variables to estimate the patient-specific risk of sPTB for each case. The screening performance of sPTB at <34 and <37 weeks was assessed by receiver-operating characteristic (ROC) curve analysis. Detection rates (DRs) for sPTB at <34 and <37 weeks were determined at a 10 % fixed false positive rate (FPR). The areas under the ROC curves (AUCs) were compared using DeLong test.

RESULTS

Among a total of 3658 included pregnancies, sPTB at <37 weeks occurred in 19 cases (0.52 %) and 154 cases (4.21 %) respectively. In the term birth group, cervical angles were affected by log10 cervical length and maternal factors (age, height, weight, method of conception, previous preterm birth, previous cervical surgery, use of progesterone). When compared to term birth group, median Angle-E was significantly increased in sPTB at <34 weeks (P = 0.017); while median Angle-D1 and D2 were significantly decreased in sPTB at <34 weeks (P = 0.049 and 0.025, respectively). The a priori risk for sPTB at <34 weeks was provided by body mass index, previous miscarriage, and previous PTB. Similarly, the a priori risk for sPTB at <37 weeks was provided by maternal height, and previous PTB. For the prediction of sPTB at <34 weeks, the best AUC was achieved by a combination of maternal factors and Angle-E MoM (AUC: 0.786, DR, 30.0 % at a FPR of 10 %). However, the difference between the AUCs of maternal factors only, Angle-E, and the combined model did not reach statistical significance. For the prediction of sPTB at <37 weeks, the best AUC was achieved by a combination of maternal factors and Angle-D2 MoM (AUC: 0.599, 95 % CI: 0.539-0.658, DR, 18.7 % at a FPR of 10 %). The difference between the AUCs of maternal factors only, Angle-D1, Angle-D2 and the combined models did not reach statistical significance.

CONCLUSIONS

Whilst there are associations between cervical angles and sPTB, these indices have limited value for prediction of sPTB in the first trimester. Further prospective studies are needed to identify other effective markers for the prediction of sPTB in the first trimester. Further prospective studies are needed to identify other effective markers for the prediction of sPTB in the first trimester.

Increasing cervical penetrability in sheep by long-acting treatments with oxytocin (Carbetocin) and/or prostaglandin E2 (Dinoprostone)

The aim was to study the effect of long-acting treatments with oxytocin (Carbetocin, Cb) and/or prostaglandin E2 (Dinoprostone, Dp) on cervical penetrability and collagenolysis in synchronized ewes (12 days MAP-eCG). At 42 h post eCG, ewes were treated with Cb (Group Cb, n = 6, 40 μg, i.m., Decomotón, Laboratorios Callier, Uruguay); Dp (Group Dp, n = 10, 10 mg, slow-release intravaginal device, Propess®, Ferring Pharmaceuticals Ltd., West Drayton, UK); combined Cb and Dp treatment (Group Cb+Dp, n = 8) and saline solution i.m. and a placebo intravaginal device (Group C, n = 10). Cervical penetrability increased from 0 h to 42 h post eCG (P < 0.003) in all groups, then decrease in Group C (P < 0.03) from 42 to 68 h post eCG, whereas remained unchanged in Groups Cb and Cb+Dp or increase at 54 h post eCG in Group Dp (P < 0.05). Thus, there was higher cervical penetrability in treated groups than Group C at the expected time of artificial insemination (54 h post eCG). At 54 h post eCG, collagen concentration was lower in Group Cb than in the others groups (P < 0.05), whereas the ratio between the activity of the activated and latent forms of MMP-2 was greater in Groups Cb and Cb+Dp than in Group C (P < 0.05). The increasing cervical penetrability induced by Cb, but not by Dp, could be explained by an increase in MMP-2-dependent collagen degradation. Furthermore, combined treatment with Cb and Dp did not enhance the effects induced by each hormone administered separately.

In vitro study of carbetocin, an oxytocin receptor agonist, and 4-phenylfuroxan-3-carbonitrile, a NO-releasing agent, as cervical dilatators in sheep

The aim was to study the effect of 4-phenylfuroxan-3-carbonitrile (Fx), a NO-releasing agent, and carbetocin, an oxytocin receptor agonist, on matrix metalloproteinases-2 (MMP-2) activity and PGE2 production in cervix from cycling sheep. Cervical explants were incubated during 12 h with MEM supplemented with increasing concentrations of Fx in DMSO (2 %) (0 to 300 μg/mL) with Cb (100 ng/mL) (Experiment 1, n = 15) and DMSO (2 %), DMSO + Cb (100 ng/mL) or DMSO + Fx (30 μg/mL) (Experiment 2, n = 10), and their respective controls. In the supernatants, activated (A) and latent (L) MMP-2 activities were determined by a SDS-PAGE zymography, PGE2 concentration by immunoassay and NO production indirectly as nitrites by spectrophotometry. Data were analyzed by ANOVA. The Cb treatment increase the A MMP-2 activity in DMSO (Experiment 1 at follicular phase and Experiment 2) or alone (Experiment 2) and increase the L MMP-2 activity (Experiments 1 and 2) (P < 0.02). The DMSO treatment also increase the L MMP2 activity (Experiment 2) (P < 0.0001). Treatment with Fx + DMSO increased the concentration of accumulated nitrites in the supernatant (P < 0.0001) (Experiment 1), but did not affect or decrease the activity of A and L MMP-2 (P < 0.04) (Experiments 1 and 2). The PGE2 concentration trend to increase with Cb treatment (P = 0.0614) and decrease with Fx+DMSO treatment (P < 0.0001) (Experiment 2). In conclusion, Cb and/or DMSO treatment of cervical explants increase the MMP-2 activity through PGE2-independent mechanisms, but Fx in DMSO fail in this, suggesting that the pre-treatment with Cb and/or DMSO could be used to increase cervical dilation in ewes.

Quantitative Assessment of Collagen Remodeling during a Murine Pregnancy

Uterine cervical remodeling is a fundamental feature of pregnancy, facilitating the delivery of the fetus through the cervical canal. Yet, we still know very little about this process due to the lack of methodologies that can quantitatively and unequivocally pinpoint the changes the cervix undergoes during pregnancy. We utilize polarization-resolved second harmonic generation to visualize the alterations the cervix extracellular matrix, specifically collagen, undergoes during pregnancy with exquisite resolution. This technique provides images of the collagen orientation at the pixel level (0.4 μm) over the entire murine cervical section. They show tight and ordered packing of collagen fibers around the os at the early stage of pregnancy and their disruption at the later stages. Furthermore, we utilize a straightforward statistical analysis to demonstrate the loss of order in the tissue, consistent with the loss of mechanical properties associated with this process. This work provides a deeper understanding of the parturition process and could support research into the cause of pathological or premature birth.

Whole cervix imaging of collagen, muscle, and cellularity in term and preterm pregnancy

Cervical softening and dilation are critical for the successful term delivery of a fetus, with premature changes associated with preterm birth. Traditional clinical measures like transvaginal ultrasound and Bishop scores fall short in predicting preterm births and elucidating the cervix's complex microstructural changes. Here, we introduce a magnetic resonance diffusion basis spectrum imaging (DBSI) technique for non-invasive, comprehensive imaging of cervical cellularity, collagen, and muscle fibers. This method is validated through ex vivo DBSI and histological analyses of specimens from total hysterectomies. Subsequently, retrospective in vivo DBSI analysis at 32 weeks of gestation in ten term deliveries and seven preterm deliveries with inflammation-related conditions shows distinct microstructural differences between the groups, alongside significant correlations with delivery timing. These results highlight DBSI's potential to improve understanding of premature cervical remodeling and aid in the evaluation of therapeutic interventions for at-risk pregnancies. Future studies will further assess DBSI's clinical applicability.

Uterine Cesarean Scar Tissue-An Immunohistochemical Study

Background and Objectives: Wound healing encompasses a multitude of factors and entails the establishment of interactions among components of the basement membrane. The quantification of particle concentrations can serve as valuable biomarkers for assessing biomechanical muscle properties. The objective of this study was to examine the immunoexpression and immunoconcentration of myometrial collagen type VI, elastin, alpha-smooth muscle actin, and smooth muscle myosin heavy chain, as well as the expression of platelets and clusters of differentiation 31 in the uterine scar following a cesarean section (CS). Materials and Methods: A total of 177 biopsies were procured from a cohort of pregnant women who were healthy, specifically during the surgical procedure of CS. The participants were categorized into seven distinct groups. Group 1 consisted of primiparas, with a total of 52 individuals. The subsequent groups were organized based on the duration of time that had elapsed since their previous CS. The analysis focused on the immunoexpression and immunoconcentration of the particles listed. Results: No significant variations were observed in the myometrial immunoconcentration of collagen type VI, elastin, smooth muscle myosin, and endothelial cell cluster of differentiation 31 among the analyzed groups. The concentration of alpha-smooth muscle actin in the myometrium was found to be significantly higher in patients who underwent CS within a period of less than 2 years since their previous CS, compared to those with a longer interval between procedures. Conclusions: Our findings indicate that the immunoconcentration of uterine myometrial scar collagen type VI, elastin, smooth muscle myosin heavy chain, alpha-smooth muscle actin, and endothelial cell marker cluster of differentiation 31 remains consistent regardless of the duration elapsed since the previous CS. The findings indicate that there are no significant alterations in the biomechanical properties of the uterine muscle beyond a period of 13 months following a CS.

Sex-Specific Transcriptomic Changes in the Villous Tissue of Placentas of Pregnant Women Using a Selective Serotonin Reuptake Inhibitor

About 5% of pregnant women are treated with selective serotonin reuptake inhibitor (SSRI) antidepressants to treat their depression. SSRIs influence serotonin levels, a key factor in neural embryonic development, and their use during pregnancy has been associated with adverse effects on the developing embryo. However, the role of the placenta in transmitting these negative effects is not well understood. In this study, we aim to elucidate how disturbances in the maternal serotonergic system affect the villous tissue of the placenta by assessing whole transcriptomes in the placentas of women with healthy pregnancies and women with depression and treated with the SSRI fluoxetine during pregnancy. Twelve placentas of the Biology, Affect, Stress, Imaging and Cognition in Pregnancy and the Puerperium (BASIC) project were selected for RNA sequencing to examine differentially expressed genes: six male infants and six female infants, equally distributed over women treated with SSRI and without SSRI treatment. Our results show that more genes in the placenta of male infants show changed expression associated with fluoxetine treatment than in placentas of female infants, stressing the importance of sex-specific analyses. In addition, we identified genes related to extracellular matrix organization to be significantly enriched in placentas of male infants born to women treated with fluoxetine. It remains to be established whether the differentially expressed genes that we found to be associated with SSRI treatment are the result of the SSRI treatment itself, the underlying depression, or a combination of the two.

Effects of polydimethylsiloxane membrane surface treatments on human uterine smooth muscle cell strain response

In the United States, 1 in 10 infants are born preterm. The majority of neonatal deaths and nearly a third of infant deaths are linked to preterm birth. Preterm birth is initiated when the quiescent state of the uterus ends prematurely, leading to contractions and parturition beginning as early as 32 weeks, though the origins are not well understood. To enable research and discovery of therapeutics with potential to better address preterm birth, the capability to study isolated cell processes of pregnant uterine tissue in vitro is needed. Our development of an in vitro model of the myometrium utilizing human uterine smooth muscle cells (uSMCs) responsible for contractions provides a methodology to examine cellular mechanisms of late-stage pregnancy potentially involved in preterm birth. We discuss culture of uSMCs on a flexible polydimethylsiloxane (PDMS) substrate functionalized with cationic poly-l-lysine (PLL), followed by extracellular matrix (ECM) protein coating. Previous work exploring uSMC behavior on PDMS substrates have utilized collagen-I coatings, however, we demonstrated the first exploration of human uSMC response to strain on fibronectin-coated flexible membranes, importantly reflecting the significant increase of fibronectin content found in the myometrial ECM during late-stage pregnancy. Using the model we developed, we conducted proof-of-concept studies to investigate the impact of substrate strain on uSMC cell morphology and gene expression. It was found that PLL and varied ECM protein coatings (collagen I, collagen III, and fibronectin) altered cell nuclei morphology and density on PDMS substrates. Additionally, varied strain rates applied to uSMC substrates significantly impacted uSMC gene expression of IL-6, a cytokine associated with instances of preterm labor. These results suggest that both surface and mechanical properties of in vitro systems impact primary human uSMC phenotype and offer uSMC culture methodologies that can be utilized to further the understanding of cellular pathways involved in the uterus under mechanical load.

Extracellular matrix-related and serine protease proteins in the amniotic fluid of women with early preterm labor: Association with spontaneous preterm birth, intra-amniotic inflammation, and microbial invasion of the amniotic cavity

PROBLEM

We aimed to determine whether altered levels of various extracellular matrix (ECM)-related and serine protease proteins in the amniotic fluid (AF) are associated with imminent spontaneous preterm birth (SPTB; ≤7 days) and intra-amniotic inflammation and/or microbial invasion of the amniotic cavity (IAI/MIAC) in women with early preterm labor (PTL).

METHOD OF STUDY

This retrospective cohort study included 252 women with singleton pregnancies undergoing transabdominal amniocentesis who demonstrated PTL (24-31 weeks). The AF was cultured for microorganism detection to characterize MIAC. IL-6 concentrations were determined in the AF samples to identify IAI (≥2.6 ng/mL). The following mediators were measured in the AF samples using ELISA: kallistatin, lumican, MMP-2, SPARC, TGFBI, and uPA.

RESULTS

Kallistatin, MMP-2, TGFBI, and uPA levels were significantly higher and SPARC and lumican levels were significantly lower in the AF of women who spontaneously delivered within 7 days than in the AF of those who delivered after 7 days; the levels of the first five mediators were independent of baseline clinical variables. In the multivariate analysis, elevated levels of kallistatin, MMP-2, TGFBI, and uPA and low levels of lumican and SPARC in the AF were significantly associated with IAI/MIAC and MIAC, even after adjusting for the gestational age at sampling. The areas under the curves of the aforementioned biomarkers ranged from 0.58 to 0.87 for the diagnoses of each of the corresponding endpoints.

CONCLUSION

ECM-related (SPARC, TGFBI, lumican, and MMP-2) and serine protease (kallistatin and uPA) proteins in the AF are involved in preterm parturition and regulation of intra-amniotic inflammatory/infectious responses in PTL.

A finite porous-viscoelastic model capturing mechanical behavior of human cervix under multi-step spherical indentation

The cervix is a soft tissue exhibiting time-dependent behavior under mechanical loads. The cervix is a vital mechanical barrier to protect the growing fetus. The remodeling of the cervical tissue, characterized by an increase in time-dependent material properties, is necessary for a safe parturition. The failure of its mechanical function and accelerated tissue remodeling is hypothesized to lead to preterm birth, which is birth before 37 weeks of gestation. To understand the mechanism of the time-dependent behavior of the cervix under compressive states, we employ a porous-viscoelastic material model to describe a set of spherical indentation tests performed on nonpregnant and term pregnant tissue. A genetic algorithm-based inverse finite element analysis is used to fit the force-relaxation data by optimizing the material parameters, and the statistical analysis of the optimized material parameters is conducted on different sample groups. The force response is captured well using the porous-viscoelastic model. The indentation force-relaxation of the cervix is explained by the porous effects and the intrinsic viscoelastic properties of the extracellular matrix (ECM) microstructure. The hydraulic permeability obtained from the inverse finite element analysis agrees with the trend of the value directly measured previously by our group. The nonpregnant samples are found significantly more permeable than the pregnant samples. Within nonpregnant samples, the posterior internal os is found significantly less permeable than the anterior and posterior external os. The proposed model exhibits the superior capability to capture the force-relaxation response of the cervix under indentation, as compared to the conventional quasi-linear viscoelastic framework (range of r2 of the porous-viscoelastic model 0.88-0.98 vs. quasi-linear model: 0.67-0.89). As a constitutive model with a relatively simple form, the porous-viscoelastic framework has the potential to be used to understand disease mechanisms of premature cervical remodeling, model contact of the cervix with biomedical devices, and interpret force readings from novel in-vivo measurement tools such as an aspiration device.

Cervical strain elastography: pattern analysis and cervical sliding sign in preterm and control pregnancies

OBJECTIVES

The aim of this study was to assess the value of cervical strain elastography and Cervical Sliding Sign (CSS) for predicting spontaneous preterm birth (sPTB).

METHODS

In our case-control study we performed an elastographic assessment of the cervix in 82 cases of preterm birth (preterm group) and 451 control pregnancies (control group) between the 20th and 37th week of gestation. We divided the anterior cervical lip first into two ("Intern2", "Extern2") and into three sectors ("Intern3", "Middle3", "Extern3"). The tissue deformation pattern after local compression with an ultrasound probe was recorded. We distinguished between an irregularly distributed ("Spotting") and homogeneous pattern presentation. Additionally, the presence of a sliding of the anterior against the posterior cervical lip (positive CSS) during compression was evaluated. A logistic regression analysis and the Akaike Information Criterion (AIC) were used to estimate the probability of sPTB and to select a prediction model.

RESULTS

Spotting and positive CSS occurred more frequently in the preterm group compared to control group (97.8 vs. 2.2%, p<0.001; 26.8 vs. 4.2%, p<0.001; respectively). The model with the parameters week of gestation at ultrasound examination, Intern3, Middle3 and CSS was calculated as the highest quality model for predicting sPTB. The AUC (Area Under the Curve) was higher for this parameter combination compared to cervical length (CL) (0.926 vs. 0.729).

CONCLUSIONS

Cervical strain elastography pattern analysis may be useful for the prediction of sPTB, as the combination of Spotting analysis and CSS is superior to CL measurement alone.

Extracellular matrix (ECM)-inspired high-strength gelatin-alginate based hydrogels for bone repair

It has always been a huge challenge to construct high-strength hydrogels that are composed entirely of natural polymers. In this study, inspired by the structural characteristics of the extracellular matrix (ECM), gelatin and hydrazide alginate were employed to mimic the composition of collagen and glycosaminoglycans (GAGs) in the ECM, respectively, to develop natural polymer (NP) high-strength hydrogels crosslinked by physical and covalent interactions (Gelatin-HAlg-DN). First, HAlg and gelatin can form physically crosslinked hydrogels (Gelatin-HAlg) due to electrostatic and hydrogen bond interactions. Then, the Gelatin-HAlg hydrogels can be further covalently crosslinked in the presence of 1-(3-dimethylaminopropyl)-3-ethyl carbodiimide hydrochloride (EDC) and N-hydroxysuccinimide (NHS) to obtain Gelatin-HAlg-DN hydrogels. The obtained Gelatin-HAlg-DN hydrogels exhibit considerably enhanced mechanical properties (tensile strength: 0.9 MPa; elongation at break: 177%) with a maximum 16- and 3.2-fold increase in tensile strength and elongation at break, respectively, compared with gelatin methacrylate (GelMA) hydrogels. Importantly, the Gelatin-HAlg-DN hydrogels exhibit excellent biodegradability and swelling stability under physiological conditions, and the capability to support cell adhesion and proliferation. In a rat critical size bone defect model, Gelatin-HAlg-DN hydrogels loaded with psoralen could effectively promote bone regeneration, showing appealing potential as tissue engineering scaffolds.

The latent phase of labor

The latent phase of labor extends from the initiation of labor to the onset of the active phase. Because neither margin is always precisely identifiable, the duration of the latent phase often can only be estimated. During this phase, the cervix undergoes a process of rapid remodeling, which may have begun gradually weeks before. As a consequence of extensive changes in its collagen and ground substance, the cervix softens, becomes thinner and dramatically more compliant, and may dilate modestly. All of these changes prepare the cervix for the more rapid dilatation that will occur during the active phase to follow. For the clinician, it is important to recognize that the latent phase may normally extend for many hours. The normal limit for the duration of the latent phase should be considered to be approximately 20 hours in a nullipara and 14 hours in a multipara. Factors that have been associated with a prolonged latent phase include deficient prelabor or intrapartum cervical remodeling, excessive maternal analgesia or anesthesia, maternal obesity, and chorioamnionitis. Approximately 10% of women with a prolonged latent phase are actually in false labor, and their contractions eventually abate spontaneously. The management of a prolonged latent phase involves either augmenting uterine activity with oxytocin or providing a sedative-induced period of maternal rest. Both are equally effective in advancing the labor to active phase dilatation. A very long latent phase may be a harbinger of other labor dysfunctions.

Measurement of cervical softness before cerclage placement with an aspiration-based device

BACKGROUND

An abnormally soft cervix could contribute to the pathophysiology of cervical shortening and cervical insufficiency. Multiple techniques to measure cervical softness have been developed but none are used routinely in clinical practice. A clinically acceptable technique to measure cervical softness could improve identification of patients at risk for cervix-related preterm birth.

OBJECTIVE

This study aimed to measure cervical softness in patients with cervical insufficiency and in normal controls using a novel, aspiration-based device. We hypothesized that the cervix is softer in patients with cervical insufficiency.

STUDY DESIGN

This was a cross-sectional study of patients presenting for cerclage at a single academic medical center. Cervical softness was measured using a noninvasive, aspiration-based device placed on the anterior lip of the cervix during a speculum examination. The device measured the aspiration pressure required to displace cervical tissue to a predefined deformation level. Stiff tissue required increased aspiration pressure, whereas soft tissue required lower pressure values. Cerclage patients were subdivided into 3 groups, namely history-indicated, ultrasound-indicated, and examination-indicated cerclage. Controls were healthy volunteers between 12+0 weeks and 23+6 weeks of gestation without a history of cervical insufficiency and were matched by gestational age to the patients in the cerclage groups. Women with a cerclage in place, multiple gestations, active genital infection, or previous cervical excision procedures were excluded. Delivery information was subsequently recorded as well.

RESULTS

Data from 133 women were analyzed; of those, 54 patients were in the cerclage group (23 history-indicated, 12 ultrasound-indicated, and 19 examination-indicated participants) and 79 were controls (40 in the first trimester and 39 in the second trimester groups). Patients who presented for ultrasound-indicated cerclage had significantly softer cervices (median; interquartile range) than second trimester controls (62 mbar; 50.5-114 vs 81 mbar; 75-101; P=.042). The difference in cervical softness was not significantly different between the history-indicated and examination-indicated cerclage groups and their respective control groups.

CONCLUSION

Patients presenting for ultrasound-indicated cerclage had significantly softer cervices than normal controls as measured by an aspiration-based device. Quantitative measurement of cervical softness with the aspiration-based device is a promising technique for objective measurement of cervical softness during pregnancy.

Vaginal microbiome: considerations for reproductive health

The microbial communities are an indispensable part of the human defense system and coexist with humans as symbionts, contributing to the metabolic functions and immune defense against pathogens. An ecologically stable vaginal microbiota is dominated by Lactobacillus species, which plays an important role in the prevention of genital infections by controlling the vaginal pH, reducing glycogen to lactic acid, and stimulating bacteriocins and hydrogen peroxide. In contrast, an abnormal vaginal microbial composition is associated with an increased risk of bacterial vaginosis, trichomoniasis, sexually transmitted diseases, preterm labor and other birth defects. This microbial diversity is affected by race, ethnicity, pregnancy, hormonal changes, sexual activities, hygiene practices and other conditions. In the present review, we discuss the changes in the microbial community of the vaginal region at different stages of a female's life cycle and its influence on her reproductive health and pathological conditions.

Progesterone and its receptor signaling in cervical remodeling: Mechanisms of physiological actions and therapeutic implications

The remodeling of the cervix from a closed rigid structure to one that can open sufficiently for passage of a term infant is achieved by a complex series of molecular events that in large part are regulated by the steroid hormones progesterone and estrogen. Among hormonal influences, progesterone exerts a dominant role for most of pregnancy to initiate a loss of tissue strength yet maintain competence in a phase termed softening. Equally important are the molecular events that abrogate progesterone function in late pregnancy to allow a loss of tissue competence and strength during cervical ripening and dilation. In this review, we focus on current understanding by which progesterone receptor signaling for the majority of pregnancy followed by a loss/shift in progesterone receptor action at the end of pregnancy, collectively ensure cervical remodeling as necessary for successful parturition.

Three-dimensional anisotropic hyperelastic constitutive model describing the mechanical response of human and mouse cervix

The mechanical function of the uterine cervix is critical for a healthy pregnancy. During pregnancy, the cervix undergoes significant softening to allow for a successful delivery. Abnormal cervical remodeling is suspected to contribute to preterm birth. Material constitutive models describing known biological shifts in pregnancy are essential to predict the mechanical integrity of the cervix. In this work, the material response of human cervical tissue under spherical indentation and uniaxial tensile tests loaded along different anatomical directions is experimentally measured. A deep-learning segmentation tool is applied to capture the tissue deformation during the uniaxial tensile tests. A 3-dimensional, equilibrium anisotropic continuous fiber constitutive model is formulated, considering collagen fiber directionality, fiber bundle dispersion, and the entropic nature of wavy cross-linked collagen molecules. Additionally, the universality of the material model is demonstrated by characterizing previously published mouse cervix mechanical data. Overall, the proposed material model captures the tension-compression asymmetric material responses and the remodeling characteristics of both human and mouse cervical tissue. The pregnant (PG) human cervix (mean locking stretch ζ=2.4, mean initial stiffness ξ=12 kPa, mean bulk modulus κ=0.26 kPa, mean dispersion b=1.0) is more compliant compared with the nonpregnant (NP) cervix (mean ζ=1.3, mean ξ=32 kPa, mean κ=1.4 kPa, mean b=1.4). Creating a validated material model, which describes the role of collagen fiber directionality, dispersion, and crosslinking, enables tissue-level biomechanical simulations to determine which material and anatomical factors drive the cervix to open prematurely. STATEMENT OF SIGNIFICANCE: In this study, we report a 3D anisotropic hyperelastic constitutive model based on Langevin statistical mechanics and successfully describe the material behavior of both human and mouse cervical tissue using this model. This model bridges the connection between the extracellular matrix (ECM) microstructure remodeling and the macro mechanical properties change of the cervix during pregnancy via microstructure-associated material parameters. This is the first model, to our knowledge, to connect the the entropic nature of wavy cross-linked collagen molecules with the mechanical behavior of the cervix. Inspired by microstructure, this model provides a foundation to understand further the relationship between abnormal cervical ECM remodeling and preterm birth. Furthermore, with a relatively simple form, the proposed model can be applied to other fibrous tissues in the future.

Depolarization imaging for fast and non-invasive monitoring of cervical microstructure remodeling in vivo during pregnancy

The cervix plays a crucial role in conception, maintenance of pregnancy, and childbirth. The mechanical properties of a pregnant woman's cervix change dramatically during gestation due to a remodeling of its microstructure, necessary for delivery. However, external factors can accelerate this process and lead to prematurity, the primary cause of perinatal mortality worldwide, due to the inefficiency of existing diagnostic methods. This study shows that polarized light is a powerful tool to probe the cervical microstructure during pregnancy. A wide-field multispectral polarimetric imaging system was fabricated to explore in vivo the cervix of full-term pregnant women. The polarimetric properties of the cervix change significantly with pregnancy progression. In particular, a set of several depolarization parameters (intrinsic and extrinsic) showed a strong linear correlation with gestational age in the red part of the visible spectral range. This trend can be attributed, among other things, to a decrease in collagen density and an increase in hydration of cervical connective tissue. Wide field depolarization imaging is a very promising tool for rapid and non-invasive analysis of cervical tissue in vivo to monitor the steady progression of pregnancy, providing the practitioner with useful information to improve the detection of preterm birth.

Matrix metalloproteinase-induced cervical extracellular matrix remodelling in pregnancy and cervical cancer

Abstract

The phenomenal extracellular matrix (ECM) remodelling of the cervix that precedes the myometrial contraction of labour at term or preterm appears to share some common mechanisms with the occurrence, growth, invasion and metastasis of cervical carcinoma. Matrix metalloproteinases (MMPs) are zinc-dependent endopeptidases that are pivotal to the complex extracellular tissue modulation that includes degradation, remodelling and exchange of ECM components, which contribute to homeostasis under normal physiological conditions such as cervical remodelling during pregnancy and puerperium. However, in cancer such as that of the uterine cervix, this extensive network of extracellular tissue modulation is altered leading to disrupted cell-cell and cell-basement membrane adhesion, abnormal tissue growth, neovascularization and metastasis that disrupt homeostasis. Cervical ECM remodelling during pregnancy and puerperium could be a physiological albeit benign neoplasm. In this review, we examined the pathophysiologic differences and similarities in the role of MMPs in cervical remodelling and cervical carcinoma.

Lay summary

During pregnancy and childbirth, the cervix, which is the barrel-shaped lower portion of the womb that connects to the vagina, gradually softens, shortens and opens to allow birth of the baby. This process requires structural and biochemical changes in the cervix that are stimulated by enzymes known as matrix metalloproteinases. Interestingly, these enzymes also affect the structural and biochemical framework of the cervix during cervical cancer, although cervical cancers usually occur after infection by human papillomavirus. This review is intended to identify and explain the similarities and differences between the structural and chemical changes in the cervix during pregnancy and childbirth and the changes seen in cervical cancer.

Mechanical Response of Mouse Cervices Lacking Decorin and Biglycan During Pregnancy

Cervical remodeling is critical for a healthy pregnancy. The proper regulation of extracellular matrix (ECM) turnover leads to remodeling throughout gestation, transforming the tissue from a stiff material to a compliant, extensible, viscoelastic tissue prepared for delivery. Small leucine-rich proteoglycans (SLRPs) regulate structural fiber assembly in the cervical ECM and overall tissue material properties. To quantify the SLRPs' mechanical role in the cervix, whole cervix specimens from nonpregnant and late pregnant knockout mice of SLRPs, decorin and biglycan, were subjected to cyclic load-unload, ramp-hold, and load-to-failure mechanical tests. Further, a fiber composite material model, accounting for collagen fiber bundle waviness, was developed to describe the cervix's three-dimensional large deformation equilibrium behavior. In nonpregnant tissue, SLRP knockout cervices have the same equilibrium material properties as wild-type tissue. In contrast, the load-to-failure and ramp-hold tests reveal SLRPs impact rupture and time-dependent relaxation behavior. Loss of decorin in nonpregnant (NP) cervices results in inferior rupture properties. After extensive remodeling, cervical strength is similar between all genotypes, but the SLRP-deficient tissue has a diminished ability to dissipate stress during a ramp-hold. In mice with a combined loss of decorin and biglycan, the pregnant cervix loses its extensibility, compliance, and viscoelasticity. These results suggest that decorin and biglycan are necessary for crucial extensibility and viscoelastic material properties of a healthy, remodeled pregnant cervix.

Conditional knockout of leptin receptor in the female reproductive tract reduces fertility due to parturition defects in mice

Leptin is required for fertility, including initiation of estrous cycles. It is therefore challenging to assess the role of leptin signaling during pregnancy. While neuron-specific transgene approaches suggest that leptin signaling in the central nervous system is most important, experiments with pharmacologic inhibition of leptin in the uterus or global replacement of leptin during pregnancy suggest leptin signaling in the reproductive tract may be required. Here, conditional leptin receptor knockout (Lepr cKO) with a progesterone receptor-driven Cre recombinase was used to examine the importance of leptin signaling in pregnancy. Lepr cKO mice have almost no leptin receptor in uterus or cervix, and slightly reduced leptin receptor levels in corpus luteum. Estrous cycles and progesterone concentrations were not affected by Lepr cKO. Numbers of viable embryos did not differ between primiparous control and Lepr cKO dams on days 6.5 and 17.5 of pregnancy, despite a slight reduction in the ratio of embryos to corpora lutea, showing that uterine leptin receptor signaling is not required for embryo implantation. Placentas of Lepr cKO dams had normal weight and structure. However, over four parities, Lepr cKO mice produced 22% fewer live pups than controls, and took more time from pairing to delivery by their fourth parity. Abnormal birth outcomes of either dystocia or dead pups occurred in 33% of Lepr cKO deliveries but zero control deliveries, and the average time to deliver each pup after crouching was significantly increased. Thus, leptin receptor signaling in the reproductive tract is required for normal labor and delivery. Summary sentence. Mice lacking leptin receptor in the reproductive tract produce fewer live pups and have more adverse labor outcomes than controls, but normal numbers of embryos near term, showing that leptin receptor signaling is required for normal parturition.

Shear wave elastography: the relationship of the cervical stiffness with gestational age and cervical length- a feasibility study

OBJECTIVES

To standardize the measurement of shear wave elastography for assessment of cervical stiffness and its relationship with gestational age and cervical length.

METHODS

A prospective cross-sectional study was conducted from September 2017 to March 2019. Data from 125 unselected women (at 11-13 + 6, 18-22 and 24-28 weeks' gestation) and 55 high-risk women were analyzed for the study. Six regions of interest were evaluated for cervical elastography in the mid-sagittal position by transvaginal ultrasound. Statistical analyses were performed using R statistical language in R-studio. Delivery outcomes were recorded for each patient.

RESULTS

The shear wave elastography was feasible with good intraoperator and interoperator reproducibility. The endocervical canal and anterior lip internal position had the highest reproducibility (ICC-0.82, 0.75). Shear wave speed was significantly higher in all internal os regions than the external os. There was a statistically significant negative linear relationship of shear wave speed with the gestational age. There was a weak positive relationship between shear wave speed and cervical length. There was no difference between pregnancies with and without spontaneous preterm delivery in shear wave speed measurements and cervical length, although numbers were small for statistical analysis. The internal os of the large loop excision of the transformation zone group was stiffer than the normal population.

CONCLUSION

Cervical elastography is feasible and effectively evaluates the tensile properties of the cervix during pregnancy. The most reproducible measurements were obtained at the anterior lip of the internal cervical os. Combining evaluation of cervical elasticity and length might further improve the identification of women at risk of preterm delivery. Currently, technical issues hinder the practical application of shear wave elastography in the clinical setting and require further research and development of the imaging modality.

Study protocol to quantify the genetic architecture of sonographic cervical length and its relationship to spontaneous preterm birth

INTRODUCTION

A short cervix (cervical length <25 mm) in the midtrimester (18-24 weeks) of pregnancy is a powerful predictor of spontaneous preterm delivery. Although the biological mechanisms of cervical change during pregnancy have been the subject of extensive investigation, little is known about whether genes influence the length of the cervix, or the extent to which genetic factors contribute to premature cervical shortening. Defining the genetic architecture of cervical length is foundational to understanding the aetiology of a short cervix and its contribution to an increased risk of spontaneous preterm delivery.

METHODS/ANALYSIS

The proposed study is designed to characterise the genetic architecture of cervical length and its genetic relationship to gestational age at delivery in a large cohort of Black/African American women, who are at an increased risk of developing a short cervix and delivering preterm. Repeated measurements of cervical length will be modelled as a longitudinal growth curve, with parameters estimating the initial length of the cervix at the beginning of pregnancy, and its rate of change over time. Genome-wide complex trait analysis methods will be used to estimate the heritability of cervical length growth parameters and their bivariate genetic correlation with gestational age at delivery. Polygenic risk profiling will assess maternal genetic risk for developing a short cervix and subsequently delivering preterm and evaluate the role of cervical length in mediating the relationship between maternal genetic variation and gestational age at delivery.

ETHICS/DISSEMINATION

The proposed analyses will be conducted using deidentified data from participants in an IRB-approved study of longitudinal cervical length who provided blood samples and written informed consent for their use in future genetic research. These analyses are preregistered with the Center for Open Science using the AsPredicted format and the results and genomic summary statistics will be published in a peer-reviewed journal.

In vivo Raman spectroscopy monitors cervical change during labor

BACKGROUND

Biochemical cervical change during labor is not well understood, in part, because of a dearth of technologies capable of safely probing the pregnant cervix in vivo. The need for such a technology is 2-fold: (1) to gain a mechanistic understanding of the cervical ripening and dilation process and (2) to provide an objective method for evaluating the cervical state to guide clinical decision-making. Raman spectroscopy demonstrates the potential to meet this need, as it is a noninvasive optical technique that can sensitively detect alterations in tissue components, such as extracellular matrix proteins, lipids, nucleic acids, and blood, which have been previously established to change during the cervical remodeling process.

OBJECTIVE

We sought to demonstrate that Raman spectroscopy can longitudinally monitor biochemical changes in the laboring cervix to identify spectral markers of impending parturition.

STUDY DESIGN

Overall, 30 pregnant participants undergoing either spontaneous or induced labor were recruited. The Raman spectra were acquired in vivo at 4-hour intervals throughout labor until rupture of membranes using a Raman system with a fiber-optic probe. Linear mixed-effects models were used to determine significant (P<.05) changes in peak intensities or peak ratios as a function of time to delivery in the study population. A nonnegative least-squares biochemical model was used to extract the changing contributions of specific molecule classes over time.

RESULTS

We detected multiple biochemical changes during labor, including (1) significant decreases in Raman spectral features associated with collagen and other extracellular matrix proteins (P=.0054) attributed to collagen dispersion, (2) an increase in spectral features associated with blood (P=.0372), and (3) an increase in features indicative of lipid-based molecules (P=.0273). The nonnegative least-squares model revealed a decrease in collagen contribution with time to delivery, an increase in blood contribution, and a change in lipid contribution.

CONCLUSION

Our findings have demonstrated that in vivo Raman spectroscopy is sensitive to multiple biochemical remodeling changes in the cervix during labor. Furthermore, in vivo Raman spectroscopy may be a valuable noninvasive tool for objectively evaluating the cervix to potentially guide clinical management of labor.

Novel regulatory roles of small leucine-rich proteoglycans in remodeling of the uterine cervix in pregnancy

The cervix undergoes rapid and dramatic shifts in collagen and elastic fiber structure to achieve its disparate physiological roles of competence during pregnancy and compliance during birth. An understanding of the structure-function relationships of collagen and elastic fibers to maintain extracellular matrix (ECM) homeostasis requires an understanding of the mechanisms executed by non-structural ECM molecules. Small-leucine rich proteoglycans (SLRPs) play key functions in biology by affecting collagen fibrillogenesis and regulating enzyme and growth factor bioactivities. In the current study, we evaluated collagen and elastic fiber structure-function relationships in mouse cervices using mice with genetic ablation of decorin and/or biglycan genes as representative of Class I SLRPs, and lumican gene representative of Class II SLRP. We identified structural defects in collagen fibril and elastic fiber organization in nonpregnant mice lacking decorin, or biglycan or lumican with variable resolution of defects noted during pregnancy. The severity of collagen and elastic fiber defects was greater in nonpregnant mice lacking both decorin and biglycan and defects were maintained throughout pregnancy. Loss of biglycan alone reduced tissue extensibility in nonpregnant mice while loss of both decorin and biglycan manifested in decreased rupture stretch in late pregnancy. Collagen cross-link density was similar in the Class I SLRP null mice as compared to wild-type nonpregnant and pregnant controls. A broader range in collagen fibril diameter along with an increase in mean fibril spacing was observed in the mutant mice compared to wild-type controls. Collectively, these findings uncover functional redundancy and hierarchical roles of Class I and Class II SLRPs as key regulators of cervical ECM remodeling in pregnancy. These results expand our understating of the critical role SLRPs play to maintain ECM homeostasis in the cervix.

Obstetrics and gynecology in Ehlers-Danlos syndrome: A brief review and update

The Ehlers-Danlos syndromes (EDSs) are a group of hereditary disorders affecting collagen and connective tissue. Gynecologic and obstetric complications occur with increased frequency and severity due to these abnormalities. Recent studies suggest that some complications, including endometriosis and premature rupture of the membranes may occur less often than previously thought. In addition, having a known diagnosis allows anticipatory planning, resulting in lower morbidity from hemorrhage and tissue injury. With continued progress in understanding the underlying mechanisms of EDS, more effective treatments can be developed.

Growth-profile configuration for specific deformations of tubular organs: A study of growth-induced thinning and dilation of the human cervix

Growth is a significant factor that results in deformations of tubular organs, and particular deformations associated with growth enable tubular organs to perform certain physiological functions. Configuring growth profiles that achieve particular deformation patterns is critical for analyzing potential pathological conditions and for developing corresponding clinical treatments for tubular organ dysfunctions. However, deformation-targeted growth is rarely studied. In this article, the human cervix during pregnancy is studied as an example to show how cervical thinning and dilation are generated by growth. An advanced hyperelasticity theory called morphoelasticity is employed to model the deformations, and a growth tensor is used to represent growth in three principle directions. The computational results demonstrate that both negative radial growth and positive circumferential growth facilitate thinning and dilation. Modeling such mixed growth represents an advancement beyond commonly used uniform growth inside tissues to study tubular deformations. The results reveal that complex growth may occur inside tissues to achieve certain tubular deformations. Integration of further biochemical and cellular activities that initiate and mediate such complex growth remains to be explored.

Mueller matrix imaging for collagen scoring in mice model of pregnancy

Preterm birth risk is associated with early softening of the uterine cervix in pregnancy due to the accelerated remodeling of collagen extracellular matrix. Studies of mice model of pregnancy were performed with an imaging Mueller polarimeter at different time points of pregnancy to find polarimetric parameters for collagen scoring. Mueller matrix images of the unstained sections of mice uterine cervices were taken at day 6 and day 18 of 19-days gestation period and at different spatial locations through the cervices. The logarithmic decomposition of the recorded Mueller matrices mapped the depolarization, linear retardance, and azimuth of the optical axis of cervical tissue. These images highlighted both the inner structure of cervix and the arrangement of cervical collagen fibers confirmed by the second harmonic generation microscopy. The statistical analysis and two-Gaussians fit of the distributions of linear retardance and linear depolarization in the entire images of cervical tissue (without manual selection of the specific regions of interest) quantified the randomization of collagen fibers alignment with gestation time. At day 18 the remodeling of cervical extracellular matrix of collagen was measurable at the external cervical os that is available for the direct optical observations in vivo. It supports the assumption that imaging Mueller polarimetry holds promise for the fast and accurate collagen scoring in pregnancy and the assessment of the preterm birth risk.

Auto-detection of cervical collagen and elastin in Mueller matrix polarimetry microscopic images using K-NN and semantic segmentation classification

We propose an approach for discriminating fibrillar collagen fibers from elastic fibers in the mouse cervix in Mueller matrix microscopy using convolutional neural networks (CNN) and K-nearest neighbor (K-NN) for classification. Second harmonic generation (SHG), two-photon excitation fluorescence (TPEF), and Mueller matrix polarimetry images of the mice cervix were collected with a self-validating Mueller matrix micro-mesoscope (SAMMM) system. The components and decompositions of each Mueller matrix were arranged as individual channels of information, forming one 3-D voxel per cervical slice. The classification algorithms analyzed each voxel and determined the amount of collagen and elastin, pixel by pixel, on each slice. SHG and TPEF were used as ground truths. To assess the accuracy of the results, mean-square error (MSE), peak signal-to-noise ratio (PSNR), and structural similarity (SSIM) were used. Although the training and testing is limited to 11 and 5 cervical slices, respectively, MSE accuracy was above 85%, SNR was greater than 40 dB, and SSIM was larger than 90%.

Enrichment of Placental Trophoblast Cells from Clinical Cervical Samples Using Differences in Surface Adhesion on an Inclined Plane

Placental trophoblast cells present in cervical samples have great potential towards non-invasive prenatal testing. However, cervical samples are highly heterogeneous, largely comprised of maternal cervical cells with only a small quantity of trophoblast cells. In order to use these rare cells for diagnostic applications, there is a need to enrich and isolate them from the heterogeneous maternal sample. Our goal was to investigate the use of gravitational flow on an inclined surface and optimize parameters including angle of incline, surface material, incubation time on the surface, solution volume, and device channel width in order to identify a design allowing label-free enrichment of trophoblast cells. In this work we detail the development of a new method and device for controlling cell adhesion to a surface vs. rolling into a collection area. The enrichment device design was developed for ease of use by non-specialized personal and on a slide surface for the ability to be directly integrated onto an automatic cell picker instrument, which can be used for downstream single cell isolation. JEG-3 trophoblast cells were used with clinical cervical samples to present the effect of the different optimization parameters on enrichment. We further provide an assessment of the impact shear stress and thickness of the liquid layer has on cell enrichment. We found that this method provides a maximum JEG-3 enrichment using polystyrene surfaces at a 50° incline with a 5 min incubation period prior to inclined flow. This resulted in a 396 ± 52% increase in purity of the trophoblast cells from the clinical cervical samples as confirmed using human leukocyte antigen G (HLA-G) antibody staining with fluorescence imaging to identify JEG-3 cells. Ultimately, this method is inexpensive, quick, and has the potential for direct integration into fetal cell isolation platforms.

Combination of histochemical analyses and micro-MRI reveals regional changes of the murine cervix in preparation for labor

The cervix is responsible for maintaining pregnancy, and its timely remodeling is essential for the proper delivery of a baby. Cervical insufficiency, or "weakness", may lead to preterm birth, which causes infant morbidities and mortalities worldwide. We used a mouse model of pregnancy and term labor, to examine the cervical structure by histology (Masson Trichome and Picrosirius Red staining), immunohistochemistry (Hyaluronic Acid Binding Protein/HABP), and ex-vivo MRI (T2-weighted and diffusion tensor imaging), focusing on two regions of the cervix (i.e., endocervix and ectocervix). Our results show that mouse endocervix has a higher proportion of smooth muscle cells and collagen fibers per area, with more compact tissue structure, than the ectocervix. With advanced gestation, endocervical changes, indicative of impending delivery, are manifested in fewer smooth muscle cells, expansion of the extracellular space, and lower presence of collagen fibers. MRI detected three distinctive zones in pregnant mouse endocervix: (1) inner collagenous layer, (2) middle circular muscular layer, and (3) outer longitudinal muscular layer. Diffusion MRI images detected changes in tissue organization as gestation progressed suggesting the potential application of this technique to non-invasively monitor cervical changes that precede the onset of labor in women at risk for preterm delivery.

Extracellular Matrix Rigidity Modulates Human Cervical Smooth Muscle Contractility-New Insights into Premature Cervical Failure and Spontaneous Preterm Birth

Spontaneous preterm birth (sPTB), a major cause of infant morbidity and mortality, must involve premature cervical softening/dilation for a preterm vaginal delivery to occur. Yet, the mechanism behind premature cervical softening/dilation in humans remains unclear. We previously reported the non-pregnant human cervix contains considerably more cervical smooth muscle cells (CSMC) than historically appreciated and the CSMC organization resembles a sphincter. We hypothesize that premature cervical dilation leading to sPTB may be due to (1) an inherent CSMC contractility defect resulting in sphincter failure and/or (2) altered cervical extracellular matrix (ECM) rigidity which influences CSMC contractility. To test these hypotheses, we utilized immunohistochemistry to confirm this CSMC phenotype persists in the human pregnant cervix and then assessed in vitro arrays of contractility (F:G actin ratios, PDMS pillar arrays) using primary CSMC from pregnant women with and without premature cervical failure (PCF). We show that CSMC from pregnant women with PCF do not have an inherent CSMC contractility defect but that CSMC exhibit decreased contractility when exposed to soft ECM. Given this finding, we used UPLC-ESI-MS/MS to evaluate collagen cross-link profiles in the cervical tissue from non-pregnant women with and without PCF and found that women with PCF have decreased collagen cross-link maturity ratios, which correlates to softer cervical tissue. These findings suggest having soft cervical ECM may lead to decreased CSMC contractile tone and a predisposition to sphincter laxity that contributes to sPTB. Further studies are needed to explore the interaction between cervical ECM properties and CSMC cellular behavior when investigating the pathophysiology of sPTB.

The association between operative hysteroscopy prior to assisted reproductive technology and cervical insufficiency in second trimester

PURPOSE

To assess the association between operative hysteroscopy prior to assisted reproductive technology (ART) cycle and cervical insufficiency (CI) in the second trimester of pregnancy.

METHODS

A retrospective cohort study was conducted. The charts of all women who got pregnant following an ART cycle between January 2015 and June 2018 were reviewed. The study group consisted of pregnant women who underwent operative hysteroscopy within 6 months before conception. The control group consisted of pregnant women who did not undergo hysteroscopy or any type of cervical surgical procedure before conception. The primary outcome measure was CI during the second trimester (13-27 weeks of gestation).

RESULTS

A total of 363 pregnancies achieved by ART cycles were assessed. After the exclusion of multiple pregnancies (n = 19), previous surgical procedures (n = 4) and first-trimester pregnancy losses (n = 80), there were 29 women in the study group and 231 women in the control group. The mean ages of the study and control groups were 31.2 ± 4.06 and 29.82 ± 4.71 years, respectively (P = 0.13). The indications for operative hysteroscopy were uterine septum (n = 19), T-shaped uterus (n = 4), endometrial polyp (n = 4), and submucosal fibroids (n = 2). The rates of CI in the study and control groups were 13.7% (4/29) and 3.4% (8/231), respectively (P = 0.012). The term delivery rates in the study and control groups were 79.3 and 91.8%, respectively (P = 0.044).

CONCLUSIONS

Operative hysteroscopy prior to ART cycles is significantly associated with CI between 13 and 27 weeks of gestation. Further investigation with larger cohorts is urgently needed to clarify this issue.

Design and implementation of a portable colposcope Mueller matrix polarimeter

SIGNIFICANCE

Mueller matrix polarimetry can provide useful information about the function and structure of the extracellular matrix. A portable and low-cost system could facilitate the clinical assessment of cervical anomalies in low-resource settings.

AIM

We introduce a low-cost snapshot Mueller matrix polarimeter that does not require external power, has no moving parts, and can acquire a full Mueller matrix in ∼1  s, to conduct a feasibility study for cervical imaging in the low-resource setting.

APPROACH

A snapshot system based on two sets of Savart plates, a ring illuminator with polarizing elements (generating four polarization states), and one camera is introduced. Stokes vectors are formulated to recover the polarization properties of the sample. Then, using Mueller matrix decomposition, the depolarization and retardance information is extracted.

RESULTS

We report the results on 16 healthy individuals (out of 22 patients imaged), whose Pap smear showed no malignant findings from mobile clinics in rural region of Mysore, India. The depolarization and retardance information was in agreement with previous reports.

CONCLUSIONS

We introduce an imaging system and conducted a feasibility study on healthy individuals. This work could futurely translate into diagnostic applications to provide a quantitative platform in the clinical environment (e.g., cervical cancer screening).

Ehlers-Danlos Syndrome in Pregnancy: A Review

Ehlers-Danlos syndrome (EDS) is a group of connective tissue disorders that can result in a range of complications during pregnancy. Pregnant EDS patients generally have a favourable outcome, but those with vascular EDS are more likely to suffer from severe maternal complications. Early diagnosis of EDS and subtype characterization can aid in pre-pregnancy counselling, planning of antenatal care, risk assessment of obstetric and neonatal complications, and influence both obstetric and anaesthetic management of these patients. This piece aims to outline the obstetric implications of classical, hypermobile, and vascular EDS, and review the current literature regarding their optimal obstetric management.

Cervical insufficiency: a noteworthy disease with controversies

Cervical insufficiency (CI) is a mainly disease leading to recurrent abortions and preterm birth which may present in about 1% of obstetric populations. Recurrent pregnancy losses caused by CI incur serious economic burdens on society as well as huge psychological burdens to family members. However, many patients even clinicians in some areas of the world still remain confused about this disease. At the same time, the etiology of CI is still uncertain and it is still a controversial disease in diagnosis and treatment. This article summarizes the potential risk factors associated with CI, which could be worthy of attention and helpful for future research. It also reviews the methods for diagnosis and treatment of CI to better understand this noteworthy disease, as well as presents the related consensus and controversies according to the newly updated guidelines, which has practical significance for conducting more in-depth investigations in the future.

Progesterone Receptor Signaling Selectively Modulates Cytokine-Induced Global Gene Expression in Human Cervical Stromal Cells

Preterm birth (PTB) is the leading cause of morbidity and mortality in infants <1 year of age. Intrauterine inflammation is a hallmark of preterm and term parturition; however, this alone cannot fully explain the pathobiology of PTB. For example, the cervix undergoes a prolonged series of biochemical and biomechanical events, including extracellular matrix (ECM) remodeling and mechanochemical changes, culminating in ripening. Vaginal progesterone (P₄) prophylaxis demonstrates great promise in preventing PTB in women with a short cervix (<25 mm). We used a primary culture model of human cervical stromal fibroblasts to investigate gene expression signatures in cells treated with interleukin-1β (IL-1β) in the presence or absence of P₄ following 17β-estradiol (17β-E₂) priming for 7–10 days. Microarrays were used to measure global gene expression in cells treated with cytokine or P₄ alone or in combination, followed by validation of select transcripts by semiquantitative polymerase chain reactions (qRT-PCR). Primary/precursor (MIR) and mature microRNAs (miR) were quantified by microarray and NanoString^® platforms, respectively, and validated by qRT-PCR. Differential gene expression was computed after data normalization followed by pathway analysis using Kyoto Encyclopedia Genes and Genomes (KEGG), Panther, Gene Ontology (GO), and Ingenuity Pathway Analysis (IPA) upstream regulator algorithm tools. Treatment of fibroblasts with IL-1β alone resulted in the differential expression of 1432 transcripts (protein coding and non-coding), while P₄ alone led to the expression of only 43 transcripts compared to untreated controls. Cytokines, chemokines, and their cognate receptors and prostaglandin endoperoxide synthase-2 (PTGS-2) were among the most highly upregulated transcripts following either IL-1β or IL-1β + P₄. Other prominent differentially expressed transcripts were those encoding ECM proteins, ECM-degrading enzymes, and enzymes involved in glycosaminoglycan (GAG) biosynthesis. We also detected differential expression of bradykinin receptor-1 and -2 transcripts, suggesting (prominent in tissue injury/remodeling) a role for the kallikrein–kinin system in cervical responses to cytokine and/or P₄ challenge. Collectively, this global gene expression study provides a rich database to interrogate stromal fibroblasts in the setting of a proinflammatory and endocrine milieu that is relevant to cervical remodeling/ripening during preparation for parturition.

Dynamic Characterization of the Biomechanical Behaviour of Bovine Ovarian Cortical Tissue and Its Short-Term Effect on Ovarian Tissue and Follicles

The ovary is a dynamic mechanoresponsive organ. In vitro, tissue biomechanics was reported to affect follicle activation mainly through the Hippo pathway. Only recently, ovary responsiveness to mechanical signals was exploited for reproductive purposes. Unfortunately, poor characterization of ovarian cortex biomechanics and of the mechanical challenge hampers reproducible and effective treatments, and prevention of tissue damages. In this study the biomechanical response of ovarian cortical tissue from abattoir bovines was characterized for the first time. Ovarian cortical tissue fragments were subjected to uniaxial dynamic testing at frequencies up to 30 Hz, and at increasing average stresses. Tissue structure prior to and after testing was characterized by histology, with established fixation and staining protocols, to assess follicle quality and stage. Tissue properties largely varied with the donor. Bovine ovarian cortical tissue consistently exhibited a nonlinear viscoelastic behavior, with dominant elastic characteristics, in the low range of other reproductive tissues, and significant creep. Strain rate was independent of the applied stress. Histological analysis prior to and after mechanical tests showed that the short-term dynamic mechanical test used for the study did not cause significant tissue tear, nor follicle expulsion or cell damage.

Hyperelastic Ex Vivo Cervical Tissue Mechanical Characterization

This paper presents the results of the comparison between a proposed Fourth Order Elastic Constants (FOECs) nonlinear model defined in the sense of Landau's theory, and the two most contrasted hyperelastic models in the literature, Mooney-Rivlin, and Ogden models. A mechanical testing protocol is developed to investigate the large-strain response of ex vivo cervical tissue samples in uniaxial tension in its two principal anatomical locations, the epithelial and connective layers. The final aim of this work is to compare the reconstructed shear modulus of the epithelial and connective layers of cervical tissue. According to the obtained results, the nonlinear parameter A from the proposed FOEC model could be an important biomarker in cervical tissue diagnosis. In addition, the calculated shear modulus depended on the anatomical location of the cervical tissue (μepithelial = 1.29 ± 0.15 MPa, and μconnective = 3.60 ± 0.63 MPa).

Stress-Swelling Finite Element Modeling of Cervical Response With Homeostatic Collagen Fiber Distributions

During pregnancy, the cervix experiences significant mechanical property change due to tissue swelling, and to ongoing changes in the collagen content. In this paper, we model how these two effects contribute to cervical deformation as the pressure load on top of the cervix increases. The cervix and its surrounding supporting ligaments are taken into consideration in the resulting mechanical analysis. The cervix itself is treated as a multilayered tube-like structure, with layer-specific collagen orientation. The cervical tissue in each layer is treated in terms of a collagen constituent that remodels with time within a ground substance matrix that experiences swelling. The load and swelling are taken to change sufficiently slowly so that the collagen properties at any instant can be regarded as being in a state of homeostasis. Among other things, the simulations show how the luminal cross-sectional area varies along its length as a function of pressure and swelling. In general, an increase in pressure causes an overall shortening of the lumen while an increase in swelling has the opposite effect.

Evaluation of Cervical Elastography Strain Pattern to Predict Preterm Birth

PURPOSE

 To evaluate cervical elastography strain pattern as a predictive marker for spontaneous preterm delivery (SPTD).

MATERIALS AND METHODS

 In this case-control study cervical length (CL) and elastographic data (strain ratio, elastography index, strain pattern score) were acquired from 335 pregnant women (20th - 34th week of gestation) by transvaginal ultrasound. Data of 50 preterm deliveries were compared with 285 normal controls. Strain ratio and elastography index were calculated by placing two regions of interest (ROIs) in parallel on the anterior cervical lip. The strain ratio was determined by dividing the higher strain value by the lower one. The elastography index was defined as the maximum of the strain ratio curve. Elastographic images were assigned a new established strain pattern (SP) score between 0 and 2 according to the distribution of strain induced by compression.

RESULTS

 Elastography index, SP score and CL differed between preterm and normal pregnancies (1.61 vs. 1.27, p < 0.001; SP score value of "2": n = 31 (62 %) vs. n = 36 (12.6 %), p < 0.001; CL 30.7 vs. 41.0 mm, p < 0.001; respectively). The elastography index and SP score were associated with a higher predictive potential than CL measurement alone (AUC 0.8059 (area under the curve); AUC 0.7716; AUC 0.7631; respectively). A combination of all parameters proved more predictive than any single parameter (AUC 0.8987; respectively).

CONCLUSION

 Higher elastography index and SP scores were correlated with an elevated risk of SPTD and are superior to CL measurement as a predictive marker. A combination of these parameters could be used as a "Cervical Index" for the prediction of SPTD.

Anisotropic Material Characterization of Human Cervix Tissue Based on Indentation and Inverse Finite Element Analysis

The cervix is essential to a healthy pregnancy as it must bear the increasing load caused by the growing fetus. Preterm birth is suspected to be caused by the premature softening and mechanical failure of the cervix. The objective of this paper is to measure the anisotropic mechanical properties of human cervical tissue using indentation and video extensometry. The human cervix is a layered structure, where its thick stromal core contains preferentially aligned collagen fibers embedded in a soft ground substance. The fiber composite nature of the tissue provides resistance to the complex three-dimensional loading environment of pregnancy. In this work, we detail an indentation mechanical test to obtain the force and deformation response during loading which closely matches in vivo conditions. We postulate a constitutive material model to describe the equilibrium material behavior to ramp-hold indentation, and we use an inverse finite element method based on genetic algorithm (GA) optimization to determine best-fit material parameters. We report the material properties of human cervical slices taken at different anatomical locations from women of different obstetric backgrounds. In this cohort of patients, the anterior internal os (the area where the cervix meets the uterus) of the cervix is stiffer than the anterior external os (the area closest to the vagina). The anatomic anterior and posterior quadrants of cervical tissue are more anisotropic than the left and right quadrants. There is no significant difference in material properties between samples of different parities (number of pregnancies reaching viable gestation age).

The role of noninvasive diagnostic imaging in monitoring pregnancy and detecting patients at risk for preterm birth: a review of quantitative approaches

Preterm birth (PTB) is the leading cause of neonatal morbidity and mortality worldwide. The ability to predict patients at risk for preterm birth remains a major health challenge. The currently available clinical diagnostics such as cervical length and fetal fibronectin may detect only up to 30% of patients who eventually experience a spontaneous preterm birth. This paper reviews ongoing efforts to improve the ability to conduct a risk assessment for preterm birth. In particular, this work focuses on quantitative methods of imaging using ultrasound-based techniques, magnetic resonance imaging, and optical imaging modalities. While ultrasound imaging is the major modality for preterm birth risk assessment, a summary of efforts to adopt other imaging modalities is also discussed to identify the technical and diagnostic limits associated with adopting them in clinical settings. We conclude the review by proposing a new approach using combined photoacoustic, ultrasound, and elastography as a potential means to better assess cervical tissue remodeling, and thus improve the detection of patients at-risk of PTB.

Cyclical cervical function in the mare involves remodelling of collagen content, which is correlated with modification of oestrogen receptor 1 abundance

This study was conducted to elucidate mare cervical dilation mechanisms by testing two hypotheses: (i) the proportion of collagen staining in histological samples of mare cervices and (ii) the abundance of hormone receptors in the equine cervix differ with stage of the oestrous cycle and site within the cervix. Tissues and jugular vein blood samples were collected from 15 mares. Collagen content was assessed using Masson's Trichome staining. Receptor abundance was assessed using RT-PCR, qRT-PCR and immunohistochemistry. In sub-epithelial stroma, there was less collagen during the follicular than luteal phase, in the caudal- (P =  0.029), mid- (P =  0.0000) and cranial (P =  0.001) cervical tissue. In the deep stroma, there was less collagen staining during the follicular stage in the mid- (P =  0.004) and cranial- (P =  0.041) cervical regions. There were PTGER2, PTGER3, PGR and ESR1 mRNA transcripts in the cervix. A greater proportion of cells were positive for ESR1 protein during the follicular phase in sub-epithelial (P =  0.019) and deep (P =  0.013) stroma. The abundance of ESR1 in the epithelium was negatively correlated with collagen staining in sub-epithelial (P =  0.007) and deep (P =  0.005) stroma. The results of the study provide new information about the cervical biology of mares by increasing the knowledge about collagen content and the relationship between collagen content and ESR1 protein abundance during the oestrous cycle which indicates the ESR1 receptor is a candidate for involvement in control of cervical dilation.

Photoacoustic imaging of the uterine cervix to assess collagen and water content changes in murine pregnancy

The uterine cervix plays a central role in the maintenance of pregnancy and in the process of parturition. Cervical remodeling involves dramatic changes in extracellular matrix composition and, in particular, of collagen and water content during cervical ripening (a term that describes the anatomical, biochemical, and physiologic changes in preparation for labor). Untimely cervical ripening in early gestation predisposes to preterm labor and delivery, the leading cause of infant death worldwide. Inadequate ripening of the cervix is associated with failure of induction or prolonged labor. The current approach to evaluate the state of the cervix relies on digital examination and sonographic examination. Herein, we present a novel imaging method that combines ultrasound (US) and photoacoustic (PA) techniques to evaluate cervical remodeling by assessing the relative collagen and water content of this organ. The method was tested in vitro in extracted collagen phantoms and ex vivo in murine cervical tissues that were collected in mid-pregnancy and at term. We report, for the first time, that our imaging approach provides information about the molecular changes in the cervix at different gestational ages. There was a strong correlation between the results of PA imaging and the histological assessment of the uterine cervix over the course of gestation. These findings suggest that PA imaging is a powerful method to assess the biochemical composition of the cervix and open avenues to non-invasively investigate the composition of this organ, which is essential for reproductive success.

A Rapid Method for Label-Free Enrichment of Rare Trophoblast Cells from Cervical Samples

Extravillous trophoblasts (EVTs) have the potential to provide the entire fetal genome for prenatal testing. Previous studies have demonstrated the presence of EVTs in the cervical canal and the ability to retrieve a small quantity of these cells by cervical sampling. However, these small quantities of trophoblasts are far outnumbered by the population of cervical cells in the sample, making isolation of the trophoblasts challenging. We have developed a method to enrich trophoblast cells from a cervical sample using differential settling of the cells in polystyrene wells. We tested the addition of small quantities of JEG-3 trophoblast cell line cells into clinical samples from standard Pap tests taken at 5 to 20 weeks of gestation to determine the optimal work flow. We observed that a 4 min incubation in the capture wells led to a maximum in JEG-3 cell settling on the surface (71 ± 10% of the initial amount added) with the removal of 91 ± 3% of the cervical cell population, leading to a 700% enrichment in JEG-3 cells. We hypothesized that settling of mucus in the cervical sample affects the separation. Finally, we performed a proof-of-concept study using our work flow and CyteFinder cell picking to verify enrichment and pick individual JEG-3 and trophoblast cells free of cervical cells. Ultimately, this work provides a rapid, facile, and cost-effective method for enriching native trophoblasts from cervical samples for use in subsequent non-invasive prenatal testing using methods including single cell picking.