Cervical softening during pregnancy: regulated changes in collagen cross-linking and composition of matricellular proteins in the mouse

Ultrasonographic assessment of the uterocervical angle in the second trimester of pregnancy as a predictor of spontaneous preterm birth

AIM

To evaluate the uterocervical angle in the second trimester in singleton pregnancies as a predictor of spontaneous preterm labour.

MATERIAL AND METHODS

An observational cohort study was carried out from March 2022 to May 2023, including consecutively selected patients with singleton pregnancies who underwent routine examinations between 18.0 and 23.6 weeks to analyse the risk of prematurity. The uterocervical angle (UCA) measurement was added to the transvaginal ultrasonographic analysis of the cervix. Birth-related outcomes were prospectively collected.

RESULTS

patients were evaluated. The occurrence of spontaneous preterm birth (sPTB) before 37 weeks was 12%, with 50 patients. An association was observed between a more obtuse uterocervical angle and the occurrence of birth before 37 weeks, with the area under the curve of 0.636 (p=0.003; 95% CI: 0.546-0.726). The cutoff point of 77.2 degrees demonstrated a sensitivity of 80% and specificity of 29.4% (p=0.003), a positive predictive value of 13.6%, and a negative predictive value of 91.3%, with a positive likelihood ratio of 1.13 and negative 0.88.

CONCLUSION

The measurement of UCA in the second trimester of pregnancy is associated with the occurrence of sPTB. The result corroborates recent literature conclusions that UCA is a relatively recent predictor of sPTB. New evidence in different populations may contribute to its possible incorporation into prematurity risk assessment.

Collagen turnover during cervical remodeling involves both intracellular and extracellular collagen degradation pathways†

Reproductive success requires accurately timed remodeling of the cervix to orchestrate the maintenance of pregnancy, the process of labor, and birth. Prior work in mice established that a combination of continuous turnover of fibrillar collagen and reduced formation of collagen cross-links allows for the gradual increase in tissue compliance and delivery of the fetus during labor. However, the mechanism for continuous collagen degradation to ensure turnover during cervical remodeling is still unknown. This study demonstrates the functional role of extracellular and intracellular collagen degradative pathways in two different settings of cervical remodeling: physiological term remodeling and inflammation-mediated premature remodeling. Extracellular collagen degradation is achieved by the activity of fibroblast-derived matrix metalloproteases MMP14, MMP2, and fibroblast activation protein (FAP). In parallel, we demonstrate the function of an intracellular collagen degradative pathway in fibroblast cells mediated by the collagen endocytic mannose receptor type-2 (MRC2). These pathways appear to be functionally redundant as loss of MRC2 does not obstruct collagen turnover or cervical function in pregnancy. While both extracellular and intracellular pathways are also utilized in inflammation-mediated premature cervical remodeling, the extracellular collagen degradation pathway uniquely employs fibroblast and immune-cell-derived proteases. In sum, these findings identify the dual utilization of two distinct degradative pathways as a failsafe mechanism to achieve continuous collagen turnover in the cervix, thereby allowing dynamic shifts in cervical tissue mechanics and function.

An integrated experimental-computational investigation of the mechanical behavior of random nanofiber networks

An integrated experimental-computational methodology was developed to study the mechanical behavior of random polymer nanofiber networks with controlled network structural parameters. Random nanofiber networks, comprised of continuous polyethylene oxide (PEO) nanofibers with ∼250 nm diameter and controlled mean fiber segment length, were designed with a computer algorithm and printed via near-field electrospinning. The structure of the same networks served as input to a computational model to obtain predictions of the macroscopic mechanical response. This methodology provides consistency in fabricating, testing and simulating nominally identical random fiber networks. Specimens with 500 to 5000 nanofibers were subjected to uniaxial tension and compared to modeling predictions for the network mechanical behavior. The predictions by the computational model, with inputs from the experimental network structure, the measured single PEO nanofiber properties, and the fiber crimp parameter, agreed with the experimental results both quantitatively and with respect to the dependence of the measured quantities on the network parameters. The network stiffness and strength followed a power-law scaling with the network density, with exponents 2.78 ± 0.15 and 1.59 ± 0.04, respectively, while the network stretch at failure gradually decreased with increasing network fiber density. Finally, the experimentally determined network toughness demonstrated a rather weak power-law dependence on the network fiber density (exponent of 1.18 ± 0.12).

Safety and effectiveness of different modes of labor induction among pregnant women delivering at referral hospitals in Dar es Salaam, Tanzania: a cohort study

BACKGROUND

Induction of labor is a medical procedure used to stimulate uterine contractions and promote cervical ripening, facilitating spontaneous vaginal delivery (SVD). Various induction methods are used globally, but data on their safety and effectiveness, especially in developing countries, are limited. This study evaluated the safety and effectiveness of different labor induction methods among pregnant women delivering at referral hospitals in Dar es Salaam, Tanzania.

METHODS

This cohort study enrolled pregnant women who underwent labor induction at referral hospitals in Dar es Salaam from April to May 2021. The induction methods assessed were oxytocin, dinoprostone, misoprostol, and balloon catheter. Data were collected on the proportion of women achieving SVD, median time to delivery, and maternal and neonatal outcomes. Data were analyzed using SPSS version 23, presenting findings as frequencies, percentages, and medians. Cox regression modelling assessed factors associated with SVD and delivery outcomes.

RESULTS

Of the 322 women included, 198 (61.5%) were at term, and 210 (65.2%) had comorbidities. Overall, 80% of women achieved SVD following induction. Among women induced with oxytocin, 95% achieved SVD, compared to 69% for dinoprostone, 72% for misoprostol, and 77% for balloon catheter. The median time to SVD was 5.42 h (IQR: 4.50-6.00) for oxytocin, 13 h (IQR: 12.00-14.00) for dinoprostone, 8.5 h (IQR: 7.00-9.00) for misoprostol, and 9.0 h (IQR: 8.00-10.00) for the balloon catheter. Maternal blood loss was significantly lower for oxytocin-induced women (p < 0.001), compared to misoprostol, dinoprostone, and balloon catheter. Neonatal outcomes were better for oxytocin-induced women (p < 0.01) and poorer for those induced with misoprostol (p < 0.01). Factors associated with achieving SVD included multigravidity (AoR = 1.57, p = 0.004), comorbidities (AoR = 1.47, p = 0.007), and use of oxytocin (AoR = 3.13, p < 0.001) or dinoprostone (AoR = 0.58, p = 0.003).

CONCLUSION

Oxytocin was the most effective and safest method for labor induction within 24 h, resulting in favorable maternal and neonatal outcomes. Healthcare workers should prioritize oxytocin for timely deliveries, while considering alternatives like dinoprostone, misoprostol, and balloon catheter based on individual patient needs and clinical circumstances.

Cervical Collagen Network Porosity Assessed by SHG Endomicroscopy Distinguishes Preterm and Normal Pregnancy-A Pilot Study

OBJECTIVE

Preterm birth (PTB) remains a pressing global health concern associated with premature cervical ripening and weakened cervical mechanical strength. Second harmonic generation (SHG) microscopy has proved instrumental in tracking progressive changes in cervical collagen morphology during pregnancy. To translate this imaging modality into clinical practice, we have developed a flexible SHG endomicroscope for label-free visualization of cervical collagen architecture. This study aims to assess the feasibility of our SHG endomicroscope for non-invasive differentiation of normal and PTB mouse models, with the ultimate goal of enabling early diagnosis and risk assessment of PTB in vivo.

METHODS

in this pilot investigation, we conducted endomicroscopic SHG imaging on frozen cervical tissue sections and intact cervices resected from both normal pregnant mice and mifepristone-induced PTB mouse models, and then analyzed the acquired images to identify collagen morphology characteristics associated with abnormal cervical collagen remodeling.

RESULTS

quantitative image analysis revealed significantly altered collage spatial distribution, larger collagen fiber diameter and pore size, along with reduced pore numbers in SHG endomicroscopy images from PTB mouse models compared to normal pregnant mice. Similar trends were consistent across SHG endomicroscopy images of subepithelial collagen fibers acquired directly from intact cervices.

CONCLUSION/SIGNIFICANCE

overall, the experiment results underscore the potential of SHG endomicroscopy, coupled with quantitative image analysis, for clinically evaluating cervical collagen remodeling and PTB risk.

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.

Uterine Collagen Cross-Linking: Biology, Role in Disorders, and Therapeutic Implications

Collagen is an essential constituent of the uterine extracellular matrix that provides biomechanical strength, resilience, structural integrity, and the tensile properties necessary for the normal functioning of the uterus. Cross-linking is a fundamental step in collagen biosynthesis and is critical for its normal biophysical properties. This step occurs enzymatically via lysyl oxidase (LOX) or non-enzymatically with the production of advanced glycation end-products (AGEs). Cross-links found in uterine tissue include the reducible dehydro-dihydroxylysinonorleucine (deH-DHLNL), dehydro-hydroxylysinonorleucine (deH-HLNL), and histidinohydroxymerodesmosine (HHMD); and the non-reducible pyridinoline (PYD), deoxy-pyridinoline (DPD); and a trace of pentosidine (PEN). Collagen cross-links are instrumental for uterine tissue integrity and the continuation of a healthy pregnancy. Decreased cervical cross-link density is observed in preterm birth, whereas increased tissue stiffness caused by increased cross-link density is a pathogenic feature of uterine fibroids. AGEs disrupt embryo development, decidualization, implantation, and trophoblast invasion. Uterine collagen cross-linking regulators include steroid hormones, such as progesterone and estrogen, prostaglandins, proteoglycans, metalloproteinases, lysyl oxidases, nitric oxide, nicotine, and vitamin D. Thus, uterine collagen cross-linking presents an opportunity to design therapeutic targets and warrants further investigation in common uterine disorders, such as uterine fibroids, cervical insufficiency, preterm birth, dystocia, endometriosis, and adenomyosis.

Review paper: The importance of consideration of collagen cross-links in computational models of collagen-based tissues

Collagen as the main protein in Extra Cellular Matrix (ECM) is the main load-bearing component of fibrous tissues. Nanostructure and architecture of collagen fibrils play an important role in mechanical behavior of these tissues. Extensive experimental and theoretical studies have so far been performed to capture these properties, but none of the current models realistically represent the complexity of network mechanics because still less is known about the collagen's inner structure and its effect on the mechanical properties of tissues. The goal of this review article is to emphasize the significance of cross-links in computational modeling of different collagen-based tissues, and to reveal the need for continuum models to consider cross-links properties to better reflect the mechanical behavior observed in experiments. In addition, this study outlines the limitations of current investigations and provides potential suggestions for the future work.

Upregulated TIMP1 facilitates and coordinates myometrial contraction by decreasing collagens and cell adhesive capacity during human labor

Myometrial contraction is one of the key events involved in parturition. Increasing evidence suggests the importance of the extracellular matrix (ECM) in this process, in addition to the functional role of myometrial smooth muscle cells, and our previous study identified an upregulated tissue inhibitor of metalloproteinase 1 (TIMP1) in human laboring myometrium compared to nonlabor samples. This study aimed to further explore the potential role of TIMP1 in myometrial contraction. First, we confirmed increased myometrial TIMP1 levels in labor and during labor with cervical dilation using transcriptomic and proteomic analyses, followed by real-time PCR, western blotting, and immunohistochemistry. Then, a cell contraction assay was performed to verify the decreased contractility after TIMP1 knockdown in vitro. To further understand the underlying mechanism, we used RNA-sequencing analysis to reveal the upregulated genes after TIMP1 knockdown; these genes were enriched in collagen fibril organization, cell adhesion, and ECM organization. Subsequently, a human matrix metalloproteinase (MMP) array and collagen staining were performed to determine the TIMPs, MMPs and collagens in laboring and nonlabor myometrium. A real-time cell adhesion assay was used to detect cell adhesive capacity. The results showed upregulated MMP8 and MMP9, downregulated collagens, and attenuated cell adhesive capacity in laboring myometrium, while lower MMP levels and higher collagen levels and cell adhesive capacity were observed in nonlabor. Moreover, TIMP1 knockdown led to restoration of cell adhesive capacity. Together, these results indicate that upregulated TIMP1 during labor facilitates and coordinates myometrial contraction by decreasing collagen and cell adhesive capacity, which may provide effective strategies for the regulation of myometrial contraction.

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.

Expression of Stemness Markers in the Cervical Smear of Patients with Cervical Insufficiency

The presence of stem cells has been previously described in human precancerous and malignant cervical cultures. Previous studies have shown a direct interplay of the stem cell niche, which is present in practically every tissue with the extracellular matrix. In the present study, we sought to determine the expression of stemness markers in cytological specimens collected from the ectocervix among women with cervical insufficiency during the second trimester of pregnancy and women with normal cervical length. A prospective cohort of 59 women was enrolled of whom 41 were diagnosed with cervical insufficiency. The expression of OCT-4 and NANOG was higher in the cervical insufficiency group compared to the control group (-5.03 (-6.27, -3.72) vs. -5.81 (-7.67, -5.02) p = 0.040 for OCT4) and (-7.47 (-8.78, -6.27) vs. -8.5 (-10.75, -7.14), p = 0.035 for NANOG. Differences in the DAZL gene were not significantly different (5.94 (4.82, 7.14) vs. 6.98 (5.87, 7.43) p = 0.097). Pearson correlation analysis indicated the existence of a moderate correlation of OCT-4 and Nanog with cervical length. Considering this information, the enhanced activity of stemness biomarkers among pregnant women diagnosed with cervical insufficiency may be predisposed to cervical insufficiency, and its predictive accuracy remains to be noted in larger population sizes.

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.

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.

Epithelial to mesenchymal transition (EMT) of feto-maternal reproductive tissues generates inflammation: a detrimental factor for preterm birth

Human pregnancy is a delicate and complex process where multiorgan interactions between two independent systems, the mother, and her fetus, maintain pregnancy. Intercellular interactions that can define homeostasis at the various cellular level between the two systems allow uninterrupted fetal growth and development until delivery. Interactions are needed for tissue remodeling during pregnancy at both fetal and maternal tissue layers. One of the mechanisms that help tissue remodeling is via cellular transitions where epithelial cells undergo a cyclic transition from epithelial to mesenchymal (EMT) and back from mesenchymal to epithelial (MET). Two major pregnancy-associated tissue systems that use EMT, and MET are the fetal membrane (amniochorion) amnion epithelial layer and cervical epithelial cells and will be reviewed here. EMT is often associated with localized inflammation, and it is a well-balanced process to facilitate tissue remodeling. Cyclic transition processes are important because a terminal state or the static state of EMT can cause accumulation of proinflammatory mesenchymal cells in the matrix regions of these tissues and increase localized inflammation that can cause tissue damage. Interactions that determine homeostasis are often controlled by both endocrine and paracrine mediators. Pregnancy maintenance hormone progesterone and its receptors are critical for maintaining the balance between EMT and MET. Increased intrauterine oxidative stress at term can force a static (terminal) EMT and increase inflammation that are physiologic processes that destabilize homeostasis that maintain pregnancy to promote labor and delivery of the fetus. However, conditions that can produce an untimely increase in EMT and inflammation can be pathologic. These tissue damages are often associated with adverse pregnancy complications such as preterm prelabor rupture of the membranes (pPROM) and spontaneous preterm birth (PTB). Therefore, an understanding of the biomolecular processes that maintain cyclic EMT-MET is critical to reducing the risk of pPROM and PTB. Extracellular vesicles (exosomes of 40-160 nm) that can carry various cargo are involved in cellular transitions as paracrine mediators. Exosomes can carry a variety of biomolecules as cargo. Studies specifically using exosomes from cells undergone EMT can carry a pro-inflammatory cargo and in a paracrine fashion can modify the neighboring tissue environment to cause enhancement of uterine inflammation.

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.

The Non-pregnant and Pregnant Human Cervix: a Systematic Proteomic Analysis

Appropriate timing of cervical remodeling (CR) is key to normal term parturition. To date, mechanisms behind normal and abnormal (premature or delayed) CR remain unclear. Recent studies show regional differences exist in human cervical tissue structure. While the entire cervix contains extracellular matrix (ECM), the internal os is highly cellular containing 50-60% cervical smooth muscle (CSM). The external os contains 10-20% CSM. Previously, we reported ECM rigidity and different ECM proteins influence CSM cell function, highlighting the importance of understanding not only how cervical cells orchestrate cervical ECM remodeling in pregnancy, but also how changes in specific ECM proteins can influence resident cellular function. To understand this dynamic process, we utilized a systematic proteomic approach to understand which soluble ECM and cellular proteins exist in the different regions of the human cervix and how the proteomic profiles change from the non-pregnant (NP) to the pregnant (PG) state. We found the human cervix proteome contains at least 4548 proteins and establish the types and relative abundance of cellular and soluble matrisome proteins found in the NP and PG human cervix. Further, we report the relative abundance of proteins involved with elastic fiber formation and ECM organization/degradation were significantly increased while proteins involved in RNA polymerase I/promoter opening, DNA methylation, senescence, immune system, and compliment activation were decreased in the PG compared to NP cervix. These findings establish an initial platform from which we can further comprehend how changes in the human cervix proteome results in normal and abnormal CR.

Antibody microarray analysis of amniotic fluid proteomes in women with cervical insufficiency and short cervix, and their association with pregnancy latency length

Introduction

This study aimed to investigate amniotic fluid (AF) proteins that were differentially expressed between patients with cervical insufficiency (CI) and asymptomatic short cervix (SCX, ≤ 25 mm), and whether these proteins could be predictive of spontaneous preterm birth (SPTB) in these patients.

Method

This was a retrospective cohort study of 129 singleton pregnant women with CI (n = 80) or SCX (n = 49) at 17 to 26 weeks who underwent amniocentesis. An antibody microarray was used to perform comparative proteomic profiling of AF from matched CI (n = 20) and SCX (n = 20) pregnancies. In the total cohort, an ELISA validation study was performed for 15 candidate proteins of interest. Subgroup analyses of patients with CI and SCX were conducted to evaluate the association between the 15 proteins and SPTB at < 32 weeks of gestation.

Results

Eighty-six proteins showed intergroup differences. ELISA validation confirmed significantly higher levels of AF EN-RAGE, IL-8, lipocalin-2, MMP-9, S100A8/A9, thrombospondin-2, and TNFR2 in patients with CI than in those with SCX. Multivariable analysis showed that increased AF levels of EN-RAGE, S100A8/A9, and uPA were independently associated with SPTB at < 32 weeks in patients with CI; whereas in patients with SCX, high AF levels of APRIL, EN-RAGE, LBP, and TNFR2 were independently associated with SPTB at < 32 weeks.

Conclusions

Multiple AF proteins show altered expression in patients with CI compared with SCX controls. Moreover, several novel mediators involved in inflammation were identified as potential biomarkers for predicting SPTB after the diagnosis of CI and SCX. These results provide new insights into target-specific molecules for targeted therapies to prevent SPTB in patients with CI/SCX.

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.

Different expressions of aquaporin water channels and macrophages infiltration in human cervix remodeling during pregnancy

Despite aquaporin water channels (AQPs) play a critical role in maintaining water homeostasis in female reproductive tract and prompt a gradual increase in water content in cervical edema as pregnancy progressed, their relationship with macrophage infiltration and collagen content in human cervical remodeling need to be further investigated. This is the first study to examine the expression and localization of AQP3, AQP4, AQP5, AQP8 and macrophages simultaneously in human cervical ripening. The immunoreactivity of these AQPs was 2.6 to 6-fold higher on gestational weeks 26 (GD26W) than that on GD6W and GD15W, but AQP4 expression on GD39W dropped a similar extent on GD15W, other AQPs continued to rise on GD39W. The AQP3, AQP4 and AQP5 intensity seemed more abundant in cervical stroma than in the perivascular area on GD26W; the distribution of AQP3, AQP5 and AQP8 in cervical stroma was equivalent to that in the perivascular area on GD39W. Macrophage numbers were 1.7-fold higher in subepithelium region and 3.0-fold higher in center area on GD26W than that on GD15W; such numbers remained elevated on GD39W. The electron micrographs showed that cervical extensibility increased significantly on GD26W and GD39W accompanied with increased macrophage infiltration, cervical water content and much more space among collagen fibers. These findings suggest that the upregulation of AQPs expression in human cervix is closely related to enhanced macrophage infiltration during pregnancy; there may be a positive feedback mechanism between them to lead the increase of water content and the degradation of collagen.

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.

Transcriptome and proteome dynamics of cervical remodeling in the mouse during pregnancy

During gestation, the female reproductive tract must maintain pregnancy while concurrently preparing for parturition. Here, we explore the transitions in gene expression and protein turnover (fractional synthesis rates [FSR]) by which the cervix implements a transition from rigid to compliant. Shifts in gene transcription to achieve immune tolerance and alter epithelial cell programs begin in early pregnancy. Subsequently, in mid-to-late pregnancy transcriptional programs emerge that promote structural reorganization of the extracellular matrix (ECM). Stable isotope labeling revealed a striking slowdown of overall FSRs across the proteome on gestation day 6 that reverses in mid-to-late pregnancy. An exception was soluble fibrillar collagens and proteins of collagen assembly, which exhibit high turnover in non-pregnant cervix compared to other tissues and FSRs that continue throughout pregnancy. This finding provides a mechanism to explain how cross-linked collagen is replaced by newly synthesized, less-cross-linked collagens, which allows increased tissue compliance during parturition. The rapid transition requires a reservoir of newly synthesized, less cross-linked collagens, which is assured by the high FSR of soluble collagens in the cervix. These findings suggest a previously unrecognized form of "metabolic flexibility" for ECM in the cervix that underlies rapid transformation in compliance to allow parturition.

Changes of pelvic organ prolapse and pelvic floor dysfunction throughout pregnancy in singleton primigravidas: A prospective cohort study

OBJECTIVE

To document the deterioration in pelvic organ support occurring throughout all trimesters during the first pregnancy of women with no known risk factors. Secondarily to make a comprehensive review in order to verify the current findings and methodologies of similar studies in the literature.

STUDY DESIGN

In this prospective study, forty-one primigravid women with a singleton pregnancy were recruited during their first trimester. During follow-up pelvic organ support changes were documented by using Pelvic Organ Prolapse Quantification (POP-Q) system. Additionally, pelvic floor muscle strength examination, by modified Oxford scoring (MOS), and symptom assessment by Pelvic Floor Distress Inventory-Short Form (PFDI-20) were performed at three time points: first (T1), second (T2), and third trimester (T3) (n = 33). The Wilcoxon test was performed to test the significance of pairwise differences. Spearman correlation coefficient was estimated to determine the linear association of the findings.

RESULTS

Both distal and proximal anterior and posterior vaginal walls (Points Aa, Ba, Ap and Bp) with cervix (C) descended towards the hymen, throughout first pregnancy with a significant caudal shift on progressing from T2 to T3 (p ≤ 0.017). Posterior fornix (Point D) made a non-significant cranial shift (p = 0.527). The genital hiatus, perineal body and total vaginal length increased significantly (p ≤ 0.001). No significant difference in MOS was observed throughout pregnancy. The scores of PFDI-20 with all its domains worsened significantly during pregnancy, especially in T3 (p ≤ 0.011). Moderate correlations were observed between posterior vaginal descent and anorectal symptoms (rho 0.427, p < 0.05), and between the changes in genital hiatus and prolapse symptoms (rho 0.406, p < 0.05).

CONCLUSION

A significant descent both in all compartments of vaginal wall and perineum with an increase in total vaginal length, was observed together with an associated pelvic floor dysfunction throughout the first pregnancy of women.

Review of Evidence-Based Methods for Successful Labor Induction

Induction of labor is increasingly a common component of the intrapartum care. Knowledge of the current evidence on methods of labor induction is an essential component of shared decision-making to determine which induction method meets an individual's health needs and personal preferences. This article provides a review of the current research evidence on labor induction methods, including cervical ripening techniques, and contraction stimulation techniques. Current evidence about expected duration of labor following induction, use of the Bishop score to guide induction, and guidance on the use of combination methods for labor induction are reviewed.

The usefulness of ultrasound before induction of labor

The indications for induction of labor have been consistently on the rise. These indications are mainly medical (maternal or fetal) or social or related to convenience or maternal preferences. With the increase in the prevalence of these indications, the incidence rates of induction of labor are expected to rise continuously. This poses a substantial workload and financial burden on maternity healthcare systems. Failure rates of induction of labor are relatively high, especially when considering the maternal, fetal, and neonatal risks associated with emergency cesarean deliveries in cases of failure. Therefore, it is essential for obstetricians to carefully select women who are eligible for induction of labor, particularly those with no clinical contraindication and who have a reasonable chance of ending up with a successful noncomplicated vaginal delivery. Ultrasound has an established role in the various areas of obstetrical care. It is available, accessible, easy to perform, and acceptable to the patient. In addition, the learning curve for skillful obstetrical ultrasound scanning is rather easy to fulfill. Ultrasound has always had an important role in the assessment of maternal and fetal well-being. Indeed, it has been extensively explored as a reliable, reproducible, and objective tool in the management of labor. In this review, we aimed to provide a comprehensive update on the different applications and uses of ultrasound before induction of labor for the prediction of its success and the potential improvement of its health-related maternal and fetal outcomes.

A case report of pregnancy in untreated alkaptonuria - Focus on urinary tissue remodelling markers

A 34-year old woman with alkaptonuria had an elective pregnancy, during which she collected urine samples over the duration of her pregnancy until parturition. She had been attending the National Alkaptonuria Centre from the age of 31 years and continued to attend after delivery for a further three annual visits. Data from her NAC visits as well as urine samples collected during pregnancy were analysed. Urine CTX-1/urine creatinine, urine αCTX-I/ urine creatinine, urine CTX-II/ urine creatinine, and urine C3M/urine creatinine all showed a rapid increase early in pregnancy, returning to baseline before increasing in late pregnancy, indicating significant remodelling of bone, subchondral bone, cartilage and other organs and connective tissue rich in collagens I, II and III. The pattern of tissue remodelling in AKU pregnancy has been described for the very first time. Further research is needed to understand pregnancy in AKU.

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%.

Spectroscopic photoacoustic imaging of cervical tissue composition in excised human samples

Objective

Cervical remodeling is an important component in determining the pathway of parturition; therefore, assessing changes in cervical tissue composition may provide information about the cervix’s status beyond the measurement of cervical length. Photoacoustic imaging is a non-invasive ultrasound-based technology that captures acoustic signals emitted by tissue components in response to laser pulses. This optical information allows for the determination of the collagen-to-water ratio (CWR). The purpose of this study was to compare the CWR evaluated by using spectroscopic photoacoustic (sPA) imaging in cervical samples obtained from pregnant and non-pregnant women.

Methods

This cross-sectional study comprised cervical biopsies obtained at the time of hysterectomy (n = 8) and at the scheduled cesarean delivery in pregnant women at term who were not in labor (n = 8). The cervical CWR was analyzed using a fiber-optic light-delivery system integrated to an ultrasound probe. The photoacoustic signals were acquired within the range of wavelengths that cover the peak absorption of collagen and water. Differences in the CWR between cervical samples from pregnant and non-pregnant women were analyzed. Hematoxylin and eosin and Sirius Red stains were used to compare the collagen content of cervical samples in these two groups.

Results

Eight cervix samples were obtained after hysterectomy, four from women ≤41 years of age and four from women ≥43 years of age; all cervical samples (n = 8) from pregnant women were obtained after 37 weeks of gestation at the time of cesarean section. The average CWR in cervical tissue samples from pregnant women was 18.7% (SD 7.5%), while in samples from non-pregnant women, it was 55.0% (SD 20.3%). There was a significantly higher CWR in the non-pregnant group compared to the pregnant group with a p-value <0.001. A subgroup analysis that compared the CWR in cervical samples from pregnant women and non-pregnant women ≤41 years of age (mean 46.3%, SD 23.1%) also showed a significantly higher CWR (p <0.01). Lower collagen content in the pregnancy group was confirmed by histological analysis, which revealed the loss of tissue composition, increased water content, and collagen degradation.

Conclusion

The proposed bimodal ultrasound and sPA imaging system can provide information on the biochemical composition of cervical tissue in pregnant and non-pregnant women. Photoacoustic imaging showed a higher collagen content in cervical samples from non-pregnant women as compared to those from pregnant women, which matched with the histological analysis. This novel imaging method envisions a new potential for a sensitive diagnostic tool in the evaluation of cervical tissue composition.

Human Chorionic Gonadotropin Modulates the Transcriptome of the Myometrium and Cervix in Late Gestation

Human chorionic gonadotropin (hCG) is a critical hormone for the establishment and maintenance of pregnancy. hCG administration prevents the onset of preterm labor in mice; yet, the transcriptomic changes associated with this tocolytic effect that take place in the myometrium and cervix have not been elucidated. Herein, we implemented both discovery and targeted approaches to investigate the transcriptome of the myometrium and cervix after hCG administration. Pregnant mice were intraperitoneally injected with 10 IU of hCG on 13.0, 15.0, and 17.0 days post coitum, and the myometrium and cervix were collected. RNA sequencing was performed to determine differentially expressed genes, enriched biological processes, and impacted KEGG pathways. Multiplex qRT-PCR was performed to investigate the expression of targeted contractility- and inflammation-associated transcripts. hCG administration caused the differential expression of 720 genes in the myometrium. Among the downregulated genes, enriched biological processes were primarily associated with regulation of transcription. hCG administration downregulated key contractility genes, Gja1 and Oxtr, but upregulated the prostaglandin-related genes Ptgfr and Ptgs2 and altered the expression of inflammation-related genes in the myometrium. In the cervix, hCG administration caused differential expression of 3348 genes that were related to inflammation and host defense, among others. The downregulation of key contractility genes and upregulation of prostaglandin-related genes were also observed in the cervix. Thus, hCG exerts tocolytic and immunomodulatory effects in late gestation by altering biological processes in the myometrium and cervix, which should be taken into account when considering hCG as a potential treatment to prevent the premature onset of labor.

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.

Challenges of conducting quantitative ultrasound with a multimodal optical imaging system

High-frequency quantitative ultrasound is a potential non-invasive source of imaging cell-tissue scale biomarkers for major diseases such as heart disease, cancer, and preterm birth. However, one of the barriers to developing such biomarkers is that it is labor-intensive to compare quantitative ultrasound images to optical images of the tissue structure. We have previously developed a multiscale imaging system that can obtain registered qualitative ultrasound and optical images, but there are further technical challenges to obtaining quantitative data: System-specific details of obtaining and processing data with Verasonics high-frequency transducers; the need for high-frequency reference phantoms; and off-axis clutter from imaging above a glass coverslip. This paper provides a characterization of the Verasonics ultrasound system with the 18.5 MHz L22-14v and 28.5 MHz L38-22v transducers, describes the construction of high-frequency reference phantoms, and details methods for reducing off-axis clutter. The paper features a demonstration multiscale image of a wild type mouse mammary gland that incorporates quantitative ultrasound with both transducers and second harmonic generation microscopy. These advances demonstrate a way to obtain, on a single system with a cohesive and integrated pipeline, quantitative ultrasound data that is correlated with optical imaging without the need for extensive sample preparation.

Strength of stochastic fibrous materials under multiaxial loading

Many biological and engineering materials are made from fibers organized in the form of a stochastic crosslinked network, and the mechanics of the network controls the behavior of the material. In this work we investigate the strength of stochastic networks without pre-existing damage which fail due to crosslink rupture. Athermal networks ranging from approximately affine to strongly non-affine are subjected to multiaxial loading and the strength is evaluated using numerical models. It is observed that once the stress is normalized by the strength measured in uniaxial tension, the failure surface becomes approximately independent of network parameters. This extends the relation between strength and network parameters previously established in (S. Deogekar, M. R. Islam, R. C. Picu, Parameters controlling the strength of stochastic fibrous materials, Int. J. Solids Struct., 2019, 168, 194-202) to the multiaxial case. The failure surface depends on both first two invariants of the stress. Strongly non-affine networks behave somewhat different from the affine networks under loadings close to the hydrostatic and pure shear loading modes, while the difference disappears in the first quadrant of the principal stress space. The results are compared with experimental data from the literature.

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.

Viscoelastic model characterization of human cervical tissue by torsional waves

The understanding of changes in the viscoelastic properties of cervical tissue during the gestation process is a challenging problem. In this work, we explore the importance of considering the multilayer nature (epithelial and connective layers) of human cervical tissue for characterizing the viscoelastic parameters from torsional waves. For this purpose, torsional wave propagations are simulated in three multilayer cervical tissue models (pure elastic, Kelvin-Voigt (KV) and Maxwell) using the finite difference time domain method. High-speed camera measurements have been carried out in tissue-mimicking phantoms in order to obtain the boundary conditions of the numerical simulations. Finally, a parametric modeling study through a probabilistic inverse procedure was performed to rank the most plausible rheological model and to reconstruct the viscoelastic parameters. The procedure consist in comparing the experimental signals obtained in human cervical tissues using the Torsional Wave Elastography (TWE) technique with the synthetic signals from the numerical models. It is shown that the rheological model that best describes the nature of cervical tissue is the Kelvin-Voigt model. Once the most plausible model has been selected, the stiffness and viscosity parameters have been reconstructed of the epithelial and connective layers for the measurements of the 18 pregnant women, along with the thickness of the epithelial layer.

Changes in alpha-7 nicotinic acetylcholine receptor and macrophage polarization state participate in the regulation of cervical remodeling in pregnant rats†

To test the hypothesis that changes in alpha-7 nicotinic acetylcholine receptor (α7nAChR) expression on macrophages and macrophage polarization participate in cervical remodeling during normal pregnancy, pregnant rats from gestational days (GDs) 14, 16, 18, 20, and 22 were used in the present study. The expression of α7nAChR on macrophages and the numbers of M1 and M2 macrophages were detected by double immunofluorescence staining. The levels of α7nAChR and collagens were detected by western blotting. M1 markers (inducible nitric oxide synthase and inflammatory cytokines) and M2 markers (arginase 1, anti-inflammatory cytokines) were detected to evaluate the macrophage polarization state by immunohistochemistry staining, western blotting, and the enzyme-linked immunosorbent assay. Matrix metalloproteinase 9 (MMP-9) expression was determined by immunohistochemistry staining and western blotting. We found that the α7nAChR expression on macrophages significantly decreased on GD22 compared to GDs 14, 16, 18, and 20. There was an increased number of M1 macrophages and decreased number of M2 macrophages in late pregnancy. The expression of M1 macrophage biomarkers was much higher on GDs 20 and 22 than on GDs 14, 16, and 18, but expression of M2 biomarkers decreased on GDs 20 and 22 compared to GDs 14, 16, and 18. MMP-9 expression was higher on GD22 than on GDs 14, 16, 18, and 20, and collagen expression significantly decreased on GDs 18, 20, and 22 compared to GD14. Our results indicated that the decreased expression of α7nAChR and increased number of M1 macrophages are associated with cervical remodeling.

Pregnancy-specific transcriptional changes upon endotoxin exposure in mice

Objectives Pregnant women are more susceptible to certain infections; however, this increased susceptibility is not fully understood. Herein, systems biology approaches were utilized to elucidate how pregnancy modulates tissue-specific host responses to a bacterial product, endotoxin. Methods Pregnant and non-pregnant mice were injected with endotoxin or saline on 16.5 days post coitum (n=8-11 per group). The uterus, cervix, liver, adrenal gland, kidney, lung, and brain were collected 12 h after injection and transcriptomes were measured using microarrays. Heatmaps and principal component analysis were used for visualization. Differentially expressed genes between groups were assessed using linear models that included interaction terms to determine whether the effect of infection differed with pregnancy status. Pathway analysis was conducted to interpret gene expression changes. Results We report herein a multi-organ atlas of the transcript perturbations in pregnant and non-pregnant mice in response to endotoxin. Pregnancy strongly modified the host responses to endotoxin in the uterus, cervix, and liver. In contrast, pregnancy had a milder effect on the host response to endotoxin in the adrenal gland, lung, and kidney. However, pregnancy did not drastically affect the host response to endotoxin in the brain. Conclusions Pregnancy imprints organ-specific host immune responses upon endotoxin exposure. These findings provide insight into the host-response against microbes during pregnancy.

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.

Assessment of the cervix in pregnant women with a history of cervical insufficiency during the first trimester using elastography

INTRODUCTION

To investigate changes in first trimester cervical elastography, cervical length and endocervical canal width in pregnant women with a history of cervical insufficiency, and further discuss the possibility of using these markers as predictors of cervical insufficiency in early pregnancy.

MATERIAL AND METHODS

This was an observational ultrasound study of first trimester cervical changes in singleton pregnancies between January 2016 and June 2018. Cervical elastography, cervical length and endocervical canal width were measured during the first trimester. Strain elastography was used to estimate the softness of anterior and posterior cervical lips and was expressed as percentages (strain rate).

RESULTS

Of the 339 pregnant women enrolled, 24 had a history of cervical insufficiency. The anterior cervical lip was significantly softer in the cervical insufficiency group (strain rate: 0.19% ± 0.05% vs 0.11% ± 0.04%; P < .001). Cervical length was significantly shorter in the cervical insufficiency group (36.3 ± 4.8 mm vs 38.3 ± 3.8 mm; P = .014). Endocervical canal width was significantly wider in the cervical insufficiency group (5.7 ± 1.1 mm vs 5.2 ± 0.7 mm; P = .001). Receiver operating characteristic curve analyses revealed that the optimal cut-off values of anterior cervical lip, cervical length and endocervical canal width to confirm the diagnosis of cervical insufficiency were 0.15%, 35.5 mm and 5.75 mm, respectively. In multivariate logistic regression analysis, significant differences were still observed in anterior cervical strain rate (adjusted odds ratio [OR] 53.78, 95% [confidence interval [CI] 11-270; P < .001) and endocervical canal width (adjusted OR, 5.41, 95% CI,1.2-24.7; P = .029).

CONCLUSIONS

First trimester cervical elastography is a valuable tool in the assessment of women with a history of cervical insufficiency. The anterior cervical lip was significantly softer in women with a history of cervical insufficiency, and the sensitivity and specificity of anterior cervical lip strain were better than that of cervical length and endocervical canal width.

Collagen at the maternal-fetal interface in human pregnancy

The survival and development of a semi-allogenic fetus during pregnancy require special immune tolerance microenvironment at the maternal fetal interface. During the establishment of a successful pregnancy, the endometrium undergoes a series of changes, and the extracellular matrix (ECM) breaks down and remodels. Collagen is one of the most abundant ECM. Emerging evidence has shown that collagen and its fragment are expressed at the maternal fetal interface. The regulation of expression of collagen is quite complex, and this process involves a multitude of factors. Collagen exerts a critical role during the successful pregnancy. In addition, the abnormal expressions of collagen and its fragments are associated with certain pathological states associated with pregnancy, including recurrent miscarriage, diabetes mellitus with pregnancy, preeclampsia and so on. In this review, the expression and potential roles of collagen under conditions of physiological and pathological pregnancy are systematically discussed.

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.

Ultra-sensitive optical coherence elastography using a high-dynamic-range force loading scheme for cervical rigidity assessment

An ultra-sensitive, wide-range force loading scheme is proposed for compression optical coherence elastography (OCE) that allows for the quantitative analysis of cervical tissue elasticity ex vivo. We designed a force loading apparatus featuring a water sink for minuscule incremental loading through a volume-controlled water droplet, from which the Young's modulus can be calculated by fitting the stress-strain curve. We validated the performance of the proposed OCE system on homogenous agar phantoms, showing the Young's modulus can be accurately estimated using this scheme. We then measured the Young's modulus of rodent cervical tissues acquired at different gestational ages, showing that the cervical rigidity of rodents was significantly dropped when entering the third trimester of pregnancy.

Immunobiology of Cervix Ripening

The cervix is the essential gatekeeper for birth. Incomplete cervix remodeling contributes to problems with delivery at or post-term while preterm birth is a major factor in perinatal morbidity and mortality in newborns. Lack of cervix biopsies from women during the period preceding term or preterm birth have led to use of rodent models to advanced understanding of the mechanism for prepartum cervix remodeling. The critical transition from a soft cervix to a compliant prepartum lower uterine segment has only recently been recognized to occur in various mammalian species when progesterone in circulation is at or near the peak of pregnancy in preparation for birth. In rodents, characterization of ripening resembles an inflammatory process with a temporal coincidence of decreased density of cell nuclei, decline in cross-linked extracellular collagen, and increased presence of macrophages in the cervix. Although a role for inflammation in parturition and cervix remodeling is not a new concept, a comprehensive examination of literature in this review reveals that many conclusions are drawn from comparisons before and after ripening has occurred, not during the process. The present review focuses on essential phenotypes and functions of resident myeloid and possibly other immune cells to bridge the gap with evidence that specific biomarkers may assess the progress of ripening both at term and with preterm birth. Moreover, use of endpoints to determine the effectiveness of various therapeutic approaches to forestall remodeling and reduce risks for preterm birth, or facilitate ripening to promote parturition will improve the postpartum well-being of mothers and newborns.

Mechanics of cervical remodelling: insights from rodent models of pregnancy

The uterine cervix undergoes a complex remodelling process during pregnancy, characterized by dramatic changes in both extracellular matrix (ECM) structure and mechanical properties. Understanding the cervical remodelling process in a term or preterm birth will aid efforts for the prevention of preterm births (PTBs), which currently affect 14.8 million babies annually worldwide. Animal models of pregnancy, particularly rodents, continue to provide valuable insights into the cervical remodelling process, through the study of changes in ECM structure and mechanical properties at defined gestation time points. Currently, there is a lack of a collective, quantitative framework to relate the complex, nonlinear mechanical behaviour of the rodent cervix to changes in ECM structure. This review aims to fill this gap in knowledge by outlining the current understanding of cervical remodelling during pregnancy in rodent models in the context of solid biomechanics. Here we highlight the collective contribution of multiple mechanical studies which give evidence that cervical softening coincides with known ECM changes throughout pregnancy. Taken together, mechanical tests on tissue from pregnant rodents reveal the cervix's remarkable ability to soften dramatically during gestation to allow for a compliant tissue that can withstand damage and can dissipate mechanical loads.

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.