Transcriptomic analysis reveals myometrial topologically associated domains linked to the onset of human term labour.

Changes in cell phenotype are thought to occur through the expression of groups of co-regulated genes within topologically associated domains (TADs). In this paper, we allocate genes expressed within the myometrium of the human uterus during the onset of term labour into TADs. Transformation of the myometrial cells of the uterus into a contractile phenotype during term human labour is the result of a complex interaction of different epigenomic and genomic layers. Recent work suggests that the transcription factor (TF) RELA lies at the top of this regulatory network. Using deep RNA sequencing (RNAseq) analysis of myometrial samples (n = 16) obtained at term from women undergoing caesarean section prior to or after the onset of labour, we have identified evidence for how other gene expression regulatory elements interact with TFs in the labour phenotype transition. Gene set enrichment analysis of our RNAseq data identified three modules of enriched genes (M1, M2 and M3), which in gene ontology studies are linked to matrix degradation, smooth muscle and immune gene signatures, respectively. These genes were predominantly located within chromosomal TADs suggesting co-regulation of expression. Our transcriptomic analysis also identified significant differences in the expression of long non-coding RNAs (lncRNA), microRNAs (miRNA) and TFs that were predicted to target genes within the TADs. Additionally, network analysis revealed 15 new lncRNA (MCM3AP-AS1, TUG1, MIR29B2CHG, HCG18, LINC00963, KCNQ1OT1, NEAT1, HELLPAR, SNHG16, NUTM2B-AS1, MALAT1, PSMA3-AS1, GABPB1-AS1, NORAD and NKILA) and 4 miRNA (mir-145, mir-223, mir-let-7a and mir-132) as top gene hubs with three TFs (NFKB1, RELA and ESR1) as master regulators. Together, these factors are likely to be involved in co-regulatory networks driving a myometrial transformation to generate an estrogen-sensitive phenotype. We conclude that lncRNA and miRNA targeting the estrogen receptor 1 and nuclear factor kappa B pathways play a key role in the initiation of human labour. For the first time, we perform an integrative analysis to present a multi-level genomic signature made of mRNA, non-coding RNA and TFs in the myometrium for spontaneous term labour.

Preterm labor is a distinct process from term labor following computational analysis of human myometrium.

BACKGROUND: The onset of the term human parturition involves myometrial gene expression changes to transform the uterus from a quiescent to a contractile phenotype. It is uncertain whether the same changes occur in the uterus during preterm labor. OBJECTIVE: This study aimed to compare the myometrial gene expression between term and preterm labor and to determine whether the presence of acute clinical chorioamnionitis or twin gestation affects these signatures. STUDY DESIGN: Myometrial specimens were collected during cesarean delivery from the following 7 different groups of patients: term not in labor (n=31), term labor (n=13), preterm not in labor (n=21), preterm labor with acute clinical chorioamnionitis (n=6), preterm labor with no acute clinical chorioamnionitis (n=9), twin preterm not in labor (n=8), and twin preterm labor with no acute clinical chorioamnionitis (n=5). RNA was extracted, reverse transcribed and quantitative polymerase chain reactions were performed on 44 candidate genes (with evidence for differential expression in human term labor) using the Fluidigm platform. Computational analysis was performed using 2-class unpaired Wilcoxon tests and principal component analysis. RESULTS: Computational analysis revealed that gene expression in the preterm myometrium, irrespective of whether in labor or not in labor, clustered tightly and is clearly different from the term labor and term not-in-labor groups. This was true for both singleton and twin pregnancies. Principal component analysis showed that 57% of the variation was explained by 3 principal components. These 44 genes interact in themes of prostaglandin activity and inflammatory signaling known to be important during term labor, but are not a full representation of the myometrium transcriptional activity. CONCLUSION: The myometrial contractions associated with preterm labor are associated with a pattern of gene expression that is distinct from term labor. Therefore, preterm labor may be initiated by a different myometrial process or processes outside the myometrium.

Role of serine-threonine phosphoprotein phosphatases in smooth muscle contractility.

The degree of phosphorylation of myosin light chain 20 (MLC20) is a major determinant of force generation in smooth muscle. Myosin phosphatases (MPs) contain protein phosphatase (PP) 1 as catalytic subunits and are the major enzymes that dephosphorylate MLC20. MP regulatory targeting subunit 1 (MYPT1), the main regulatory subunit of MP in all smooth muscles, is a key convergence point of contractile and relaxatory pathways. Combinations of regulatory mechanisms, including isoform splicing, multiple phosphorylation sites, and scaffolding proteins, modulate MYPT1 activity with tissue and agonist specificities to affect contraction and relaxation. Other members of the PP1 family that do not target myosin, as well as PP2A and PP2B, dephosphorylate a range of proteins that affect smooth muscle contraction. This review discusses the role of phosphatases in smooth muscle contractility with a focus on MYPT1 in uterine smooth muscle. Myometrium shares characteristics of vascular and other visceral smooth muscles yet, during healthy pregnancy, undergoes hypertrophy, hyperplasia, quiescence, and labor as physiological processes. Myometrium presents an accessible model for the study of normal and pathological smooth muscle function, and a better understanding of myometrial physiology may allow the development of novel therapeutics for the many disorders of myometrial physiology from preterm labor to dysmenorrhea.

Global DNA methylation and cognitive and behavioral outcomes at 4 years of age: A cross-sectional study.

BACKGROUND: Accumulating evidence suggests that breastfeeding exclusivity and duration are positively associated with child cognition. This study investigated whether DNA methylation, an epigenetic mechanism modified by nutrient intake, may contribute to the link between breastfeeding and child cognition. The aim was to quantify the relationship between global DNA methylation and cognition and behavior at 4 years of age. METHODS: Child behavior and cognition were measured at age 4 years using the Wechsler Preschool and Primary Scale of Intelligence, third version (WPPSI-III), and Child Behavior Checklist (CBC). Global DNA methylation (%5-methylcytosines (%5mC)) was measured in buccal cells at age 4 years, using an enzyme-linked immunosorbent assay (ELISA) commercial kit. Linear regression models were used to quantify the statistical relationships. RESULTS: Data were collected from 73 children recruited from the Women and Their Children's Health (WATCH) study. No statistically significant associations were found between global DNA methylation levels and child cognition or behavior (p > .05), though the estimates of effect were consistently negative. Global DNA methylation levels in males were significantly higher than in females (median %5mC: 1.82 vs. 1.03, males and females, respectively, (p < .05)). CONCLUSION: No association was found between global DNA methylation and child cognition and behavior; however given the small sample, this study should be pooled with other cohorts in future meta-analyses.

Misleading Westerns: Common Quantification Mistakes in Western Blot Densitometry and Proposed Corrective Measures.

Densitometry data generated for Western blots are commonly used to compare protein abundance between samples. In the last decade, it has become apparent that assumptions underpinning these comparisons are often violated in studies reporting Western blot data in the literature. These violations can lead to erroneous interpretations of data and may contribute to poor reproducibility of research. We assessed the reliability of Western blot data obtained to study human myometrial tissue proteins. We ran dilution series of protein lysates to explore the linearity of densitometry data. Proteins analysed included αSMA, HSP27, ERK1/2, and GAPDH. While ideal densitometry data are directly proportional to protein abundance, our data confirm that densitometry data often deviate from this ideal, in which case they can fit nonproportional linear or hyperbolic mathematical models and can reach saturation. Nonlinear densitometry data were observed when Western blots were detected using infrared fluorescence or chemiluminescence, and under different SDS-PAGE conditions. We confirm that ghosting artefacts associated with overabundance of proteins of interest in Western blots can skew findings. We also confirm that when data to be normalised are not directly proportional to protein abundance, it is a mistake to use the normalisation technique of dividing densitometry data from the protein-of-interest with densitometry data from loading control protein(s), as this can cause the normalised data to be unusable for making comparisons. Using spiked proteins in a way that allowed us to control the total protein amount per lane, while only changing the amount of spiked proteins, we confirm that nonlinearity and saturation of densitometry data, and errors introduced from normalisation processes, can occur in routine assays that compare equal amounts of lysate. These findings apply to all Western blot studies, and we highlight quality control checks that should be performed to make Western blot data more quantitative.

Evidence that a protein kinase A substrate, small heat-shock protein 20, modulates myometrial relaxation in human pregnancy.

For a successful human pregnancy, the phasic smooth muscle of the myometrium must remain quiescent until labor. Activation of cAMP/cAMP-dependent protein kinase A (PKA) pathways contributes to this quiescence. The small heat-shock protein 20 (HSP20) is a target of PKA, and phosphorylated HSP20 (pHSP20) modulates relaxation of tonic vascular smooth muscle via interaction with actin, independent of myosin dephosphorylation. Our objective was to determine whether relaxation in human myometrium is associated with changes in phosphorylation of HSP20. Myometrium was obtained at elective cesarean. Elevating cAMP with forskolin or rolipram (a phosphodiesterase inhibitor) caused substantial relaxation of spontaneously contracting human myometrial strips, of 92 +/- 4% (mean +/- sem, n = 10) and 84 +/- 7% (n = 6), respectively. Subsequent two-dimensional electrophoresis with immunoblotting of strip extracts showed a significant 2.6- and 2.1-fold increase in phosphorylated HSP20 (pHSP20) after forskolin (P < 0.01; n = 5) or rolipram treatment (P < 0.05; n = 4). Noncyclic-nucleotide-mediated relaxation, induced by the calcium channel blocker nifedipine, did not alter pHSP20. Inhibition of PKA with H89 significantly attenuated rolipram-induced relaxation (P < 0.01; n = 4), and partially reduced rolipram-stimulated pHSP20. Total and pHSP20 protein was unchanged in term laboring and nonlaboring myometria. Coimmunoprecipitation studies revealed a specific association of HSP20 with alpha-smooth muscle actin and HSP27, a key regulator of actin filament dynamics. Finally, coimmunofluorescence demonstrated moderate colocalization of HSP20 with alpha-smooth muscle actin in the cytoplasm of laboring myometria. Our data support a novel role for pHSP20 in the modulation of cyclic-nucleotide-mediated myometrial relaxation, through interaction with actin. pHSP20 represents an important new target for future tocolytic therapy.

Contraction in human myometrium is associated with changes in small heat shock proteins.

The myometrium undergoes substantial remodeling at the time of labor including rearrangement of the cellular contractile machinery. The regulation of this process in human myometrium at the time of labor is poorly defined, but evidence in other muscle types suggests modulation by small heat shock proteins (sHSP). The aim of this study was to investigate whether similar changes in sHSP occur in the myometrium at labor. Using a quantitative proteomic approach (two-dimensional difference gel electrophoresis), we found a 69% decrease in the sHSP alphaB-crystallin in the myometrium at labor plus multiple isoforms of HSP27. Immunoblotting using phosphospecific HSP27 antibodies (HSP27-serine15, -78, and -82) detected marked changes in HSP27 phosphorylation at labor. Although total HSP27 levels were unchanged, HSP27-Ser15 was 3-fold higher at labor. Coimmunoprecipitation studies showed that HSP27 coprecipitates with alphaB-crystallin and also smooth muscle alpha-actin. Coimmunofluorescence studies demonstrated a relocation of HSP27 from the perinuclear region to the actin cytoskeleton at labor. The functional significance of these changes was demonstrated in vitro where myometrial strips stimulated to contract with oxytocin exhibited increased HSP27-Ser15 phosphorylation. Our findings provide data consistent with a novel pathway regulating human myometrial contraction at labor and identify HSP27 and alphaB-crystallin as potential targets for future tocolytic design.

Methyl-Donor and Cofactor Nutrient Intakes in the First 2-3 Years and Global DNA Methylation at Age 4: A Prospective Cohort Study.

BACKGROUND: During the early postnatal period, the impact of nutrition on DNA methylation has not been well studied in humans. The aim was to quantify the relationship between one-carbon metabolism nutrient intake during the first three years of life and global DNA methylation levels at four years. DESIGN: Childhood dietary intake was assessed using infant feeding questionnaires, food frequency questionnaires, 4-day weighed food records and 24-h food records. The dietary records were used to estimate the intake of methionine, folate, vitamins B2, B6 and B12 and choline. The accumulative nutrient intake specific rank from three months to three years of age was used for analysis. Global DNA methylation (%5-methyl cytosines (%5-mC)) was measured in buccal cells at four years of age, using an enzyme-linked immunosorbent assay (ELISA) commercial kit. Linear regression models were used to quantify the statistical relationships. RESULTS: Data were collected from 73 children recruited from the Women and their Children's Health (WATCH) study. No association was found between one-carbon metabolism nutrient intake and global DNA methylation levels (P > 0.05). Global DNA methylation levels in males were significantly higher than in females (median %5-mC: 1.82 vs. 1.03, males and females respectively, (P < 0.05)). CONCLUSION: No association was found between the intake of one-carbon metabolism nutrients during the early postnatal period and global DNA methylation levels at age four years. Higher global DNA methylation levels in males warrants further investigation.

3D Cell Culturing and Possibilities for Myometrial Tissue Engineering.

Research insights into uterine function and the mechanisms of labour have been hindered by the lack of suitable animal and cellular models. The use of traditional culturing methods limits the exploration of complex uterine functions, such as cell interactions, connectivity and contractile behaviour, as it fails to mimic the three-dimensional (3D) nature of uterine cell interactions in vivo. Animal models are an option, however, use of these models is constrained by ethical considerations as well as translational limitations to humans. Evidence indicates that these limitations can be overcome by using 3D culture systems, or 3D Bioprinters, to model the in vivo cytological architecture of the tissue in an in vitro environment. 3D cultured or 3D printed cells can be used to form an artificial tissue. This artificial tissue can not only be used as an appropriate model in which to study cellular function and organisation, but could also be used for regenerative medicine purposes including organ or tissue transplantation, organ donation and obstetric care. The current review describes recent developments in cell culture that can facilitate the development of myometrial 3D structures and tissue engineering applications.

Progesterone withdrawal and estrogen activation in human parturition are coordinated by progesterone receptor A expression in the myometrium.

In human parturition, progesterone withdrawal and estrogen activation are not mediated by changes in progesterone and estrogen levels. Instead, these events could be facilitated by changes in the responsiveness of the myometrium to progesterone and estrogens via changes in PR and ER expression. We hypothesized that functional progesterone withdrawal occurs by increased expression of the type A PR (PR-A), which suppresses progesterone responsiveness, and that functional estrogen activation occurs by increased myometrial expression of ERalpha and/or ERbeta. To test this hypothesis we compared the abundance of mRNAs (assessed by quantitative RT-PCR) encoding PR-A, PR-B, ERalpha, and ERbeta in nonlaboring (n = 12) and laboring (n = 12) term human myometrium. PR-A, PR-B, the PR-A/PR-B mRNA ratio, and ERalpha mRNA were significantly increased in laboring myometrium, whereas ERbeta mRNA was low and unchanged. The PR-A/PR-B mRNA ratio correlated positively with ERalpha mRNA levels in nonlaboring myometrium and with HOXA10 mRNA levels in laboring myometrium. Because progesterone inhibits ERalpha and HOXA10 expression, these findings indicate that myometrial progesterone responsiveness is inversely related to the extent of expression of PR-A relative to PR-B. ERalpha mRNA levels correlated positively with cyclooxygenase type 2 and oxytocin receptor mRNA levels in nonlaboring myometrium, indicating that the increase in ERalpha expression is directly associated with the activation of contraction-associated genes and estrogen responsiveness. These data indicate that in the term human myometrium, responsiveness to progesterone is controlled by the expression of PR-A relative to PR-B and that a significant increase in this ratio underlies functional progesterone withdrawal. Our data also indicate that functional estrogen activation occurs by increased expression of ERalpha and is linked to functional progesterone withdrawal. Interaction between the PR and ER systems in the human myometrium may be critical for the control of human parturition and the coordination of progesterone withdrawal and estrogen activation required for parturition.

Estrogen represses whereas the estrogen-antagonist ICI 182780 stimulates placental CRH gene expression.

CRH and estrogens, produced by placental trophoblasts, have been suggested to play pivotal roles in the control of human parturition. Estrogen has been shown to affect hypothalamic CRH expression. Therefore, we evaluated 17 beta-estradiol (E2) in the regulation of CRH gene expression in placental cells. E2 inhibited CRH mRNA expression in a dose-dependent manner, which paralleled the decrease in CRH protein levels in culture media. A complete estrogen receptor (ER) antagonist, ICI 182780, not only blocked repression of CRH mRNA levels by E2, but up-regulated CRH mRNA and protein synthesis. An ER alpha-mixed agonist/antagonist and ER beta antagonist, 4-hydroxytamoxifen, also down-regulated CRH gene expression. Using quantitative RT-PCR, we found that placental trophoblasts express predominantly the ER alpha form of the receptor. Transient transfection assays conducted in the choriocarcinoma cell line JEG-3 demonstrated that E2 repressed CRH promoter activity, whereas the antagonist ICI 182780 up-regulated CRH promoter activity when ER alpha was cotransfected. These studies demonstrate that E2 represses placental CRH gene expression through an ER alpha-mediated mechanism. Estrogen may therefore modulate placental CRH production, influencing the rate of rise of maternal plasma CRH concentrations and potentially the length of gestation.

Diminished hERG K+ channel activity facilitates strong human labour contractions but is dysregulated in obese women.

Human ether-a-go-go-related gene (hERG) potassium channels determine cardiac action potential and contraction duration. Human uterine contractions are underpinned by an action potential that also possesses an initial spike followed by prolonged depolarization. Here we show that hERG channel proteins (α-conducting and ß-inhibitory subunits) and hERG currents exist in isolated patch-clamped human myometrial cells. We show that hERG channel activity suppresses contraction amplitude and duration before labour, thereby facilitating quiescence. During established labour, expression of ß-inhibitory protein is markedly enhanced, resulting in reduced hERG activity that is associated with an increased duration of uterine action potentials and contractions. Thus, changes in hERG channel activity contribute to electrophysiological mechanisms that produce contractions during labour. We also demonstrate that this system fails in women with elevated BMI, who have enhanced hERG activity as a result of low ß-inhibitory protein expression, which likely contributes to the weak contractions and poor labour outcomes observed in many obese women necessitating caesarean delivery.

Phasic phosphorylation of caldesmon and ERK 1/2 during contractions in human myometrium.

Human myometrium develops phasic contractions during labor. Phosphorylation of caldesmon (h-CaD) and extracellular signal-regulated kinase 1/2 (ERK 1/2) has been implicated in development of these contractions, however the phospho-regulation of these proteins is yet to be examined during periods of both contraction and relaxation. We hypothesized that protein phosphorylation events are implicated in the phasic nature of myometrial contractions, and aimed to examine h-CaD and ERK 1/2 phosphorylation in myometrium snap frozen at specific stages, including; (1) prior to onset of contractions, (2) at peak contraction and (3) during relaxation. We aimed to compare h-CaD and ERK 1/2 phosphorylation in vitro against results from in vivo studies that compared not-in-labor (NIL) and laboring (L) myometrium. Comparison of NIL (n = 8) and L (n = 8) myometrium revealed a 2-fold increase in h-CaD phosphorylation (ser-789; P = 0.012) during onset of labor in vivo, and was associated with significantly up-regulated ERK2 expression (P = 0.022), however no change in ERK2 phosphorylation was observed (P = 0.475). During in vitro studies (n = 5), transition from non-contracting tissue to tissue at peak contraction was associated with increased phosphorylation of both h-CaD and ERK 1/2. Furthermore, tissue preserved at relaxation phase exhibited diminished levels of h-CaD and ERK 1/2 phosphorylation compared to tissue preserved at peak contraction, thereby producing a phasic phosphorylation profile for h-CaD and ERK 1/2. h-CaD and ERK 1/2 are phosphorylated during myometrial contractions, however their phospho-regulation is dynamic, in that h-CaD and ERK 1/2 are phosphorylated and dephosphorylated in phase with contraction and relaxation respectively. Comparisons of NIL and L tissue are at risk of failing to detect these changes, as L samples are not necessarily preserved in the midst of an active contraction.

Spontaneous and induced labour are associated with different myometrial proteomes in the human.

Human myometrium undergoes a major phenotypic change at labour likely involving modifications to key regulatory proteins. In some cases, the myometrium fails to activate normally and medical intervention is required to induce labour. In this study, 2-D DIGE was used to examine changes in the myometrial proteome at the time of spontaneous (SL) and induced labour (IL). Proteomic profiles of nonlabouring term myometria (NL, n = 6) were quantitatively compared to SL (n = 6) and prostaglandin/oxytocin-IL term myometria (n = 6). In SL samples, 23 differentially expressed protein spots were detected (9 increased/14 decreased compared to NL, p<0.05). In IL samples, 59 differentially expressed spots were observed (13 increased/46 decreased compared to NL). Comparison of SL and IL proteomes revealed 69 differentially expressed proteins (7 increased/62 decreased). Two proteins consistently decreased in SL and IL samples were identified as transgelin (1.98- and 1.97-fold decrease in SL and IL, respectively) and αB-crystallin (3.27- and 2.49-fold decrease). Levels of desmin and cytosolic phospholipase A2 ß were decreased 2.9- and 2.65-fold, respectively only in IL samples. Our results show human labour is accompanied by general downregulation of specific myometrial proteins. Differences exist between SL and IL myometrial proteomes indicating divergence of underlying processes and highlighting the importance of distinguishing these groups in future studies of parturition. Our findings underscore the utility of discovery approaches in investigations of organ-wide protein changes that underlie discrete physiological events including human labour.

Pathological interactions with the timing of birth and uterine activation.

The physiological processes that regulate the onset of parturition and birth are slowly being elucidated, and the points at which pathology can intervene are becoming more apparent. The data support the view that multiple pathways lead to myometrial activation. The clinical corollary is that combinations of tocolytics that operate via different mechanisms may be more effective than single agents. It may also be necessary to divide preterm labour into groups based on underlying mechanisms and to tailor therapy accordingly.