Human Labour is Associated with a Decline in Myometrial Chemokine Receptor Expression: The Role of Prostaglandins, Oxytocin and Cytokines

Multiple pregnancies, the myometrium and the role of mechanical factors in the timing of labour

Multiple pregnancy remains a relatively common occurrence, but it is associated with increased risks of adverse outcomes for the mother and her babies and presents unique challenges to healthcare providers. This review will briefly discuss multiple pregnancies, their aetiology and their problems, including preterm birth, before reviewing the processes leading to normal labour onset and how they may be different in a multiple pregnancy. The mechanisms by which mechanical factors i.e., uterine distension or 'stretch' contribute to uterine excitability and the timing of labour onset will be the major focus, and how over distention may pre-dispose multiple pregnancies to preterm birth. This includes current thinking around the role of mechano (stretch) sensitive ion channels in the myometrium and changes to other important regulators of excitability and contraction which have been identified from studies using in vitro and in vivo models of uterine stretch. Physiological stimuli arising from the fetus(es) and placenta(s) will also be discussed. In reviewing what we know about the myometrium in multiple pregnancy in humans, the focus will be on twin pregnancy as it is the most common type of multiple pregnancy and has been the most studied.

Telomere-Related Disorders in Fetal Membranes Associated With Birth and Adverse Pregnancy Outcomes

Telomere disorders have been associated with aging-related diseases, including diabetes, vascular, and neurodegenerative diseases. The main consequence of altered telomere is the induction of the state of irreversible cell cycle arrest. Though several mechanisms responsible for the activation of senescence have been identified, it is still unclear how a cell is indeed induced to become irreversibly arrested. Most tissues in the body will experience senescence throughout its lifespan, but intrinsic and extrinsic stressors, such as chemicals, pollution, oxidative stress (OS), and inflammation accelerate the process. Pregnancy is a state of OS, as the higher metabolic demand of the growing fetus results in increased reactive oxygen species production. As a temporary organ in the mother, senescence in fetal membranes and placenta is expected and linked to term parturition (>37 weeks of gestation). However, a persistent, overwhelming, or premature OS affects placental antioxidant capacity, with consequent accumulation of OS causing damage to lipids, proteins, and DNA in the placental tissues. Therefore, senescence and its main inducer, telomere length (TL) reduction, have been associated with pregnancy complications, including stillbirth, preeclampsia, intrauterine growth restriction, and prematurity. Fetal membranes have a notable role in preterm births, which continue to be a major health issue associated with increased risk of neo and perinatal adverse outcomes and/or predisposition to disease in later life; however, the ability to mediate a delay in parturition during such cases is limited, because the pathophysiology of preterm births and physiological mechanisms of term births are not yet fully elucidated. Here, we review the current knowledge regarding the regulation of telomere-related senescence mechanisms in fetal membranes, highlighting the role of inflammation, methylation, and telomerase activity. Moreover, we present the evidences of TL reduction and senescence in gestational tissues by the time of term parturition. In conclusion, we verified that telomere regulation in fetal membranes requires a more complete understanding, in order to support the development of successful effective interventions of the molecular mechanisms that triggers parturition, including telomere signals, which may vary throughout placental tissues.

Comparison of the myometrial transcriptome from singleton and twin pregnancies by RNA-Seq

Preterm birth is recognized as the primary cause of infant mortality worldwide. Twin pregnancies are significantly more at risk of preterm birth than singleton pregnancies. A greater understanding of why this is and better modes of treatment and prevention are needed. Key to this is determining the differing pathophysiological mechanisms of preterm birth in twins, including the role of the myometrium and premature uterine contraction. We performed RNA sequencing (RNA-Seq) of human myometrium from singleton and twin pregnancies at term (> 37+0 weeks) and preterm (< 37+0 weeks), collected during pre-labour Caesarean Section. RNA-Seq libraries were prepared from polyA-selected RNA and sequenced on the Illumina HiSeq 4000 platform. Differentially expressed genes (DEGs), GO (Gene Ontology) and KEGG (Kyoto Encyclopedia of Genes and Genomes) pathway enrichment were conducted using R software. Significance was determined with a false discovery rate-adjusted P value of <0.05. Only 3 DEGs were identified between gestational age-matched singleton and twin myometrium and only 1 DEG identified between singleton term and twin preterm tissues. Comparison of singleton preterm myometrium with twin term myometrium however, revealed 75 down-regulated and 24 up-regulated genes in twin myometrium. This included genes associated with inflammation and immune response, T cell maturation and differentiation and steroid biosynthesis. GO and KEGG enrichment analyses for biologically relevant processes and functions also revealed several terms related to inflammation and immune response, as well as cytokine-cytokine receptor interaction and chemokine receptor signalling. Data indicate that little or no differences exist in the transcriptome of singleton and twin myometrium when matched for gestational age. The significant up- and down-regulation of genes identified between preterm singleton and twin myometrium at term may point to transcriptome changes associated with the chronic levels of uterine stretch in twin pregnancy or genes associated with the myometrium transitioning to labour onset.

Oxytocin-secreting system: A major part of the neuroendocrine center regulating immunologic activity

Interactions between the nervous system and immune system have been studied extensively. However, the mechanisms underlying the neural regulation of immune activity, particularly the neuroendocrine regulation of immunologic functions, remain elusive. In this review, we provide a comprehensive examination of current evidence on interactions between the immune system and hypothalamic oxytocin-secreting system. We highlight the fact that oxytocin may have significant effects in the body, beyond its classical functions in lactation and parturition. Similar to the hypothalamo-pituitary-adrenal axis, the oxytocin-secreting system closely interacts with classical immune system, integrating both neurochemical and immunologic signals in the central nervous system and in turn affects immunologic defense, homeostasis, and surveillance. Lastly, this review explores therapeutic potentials of oxytocin in treating immunologic disorders.

Whole blood gene expression profile associated with spontaneous preterm birth in women with threatened preterm labor

Threatened preterm labor (TPTL) is defined as persistent premature uterine contractions between 20 and 37 weeks of gestation and is the most common condition that requires hospitalization during pregnancy. Most of these TPTL women continue their pregnancies to term while only an estimated 5% will deliver a premature baby within ten days. The aim of this work was to study differential whole blood gene expression associated with spontaneous preterm birth (sPTB) within 48 hours of hospital admission. Peripheral blood was collected at point of hospital admission from 154 women with TPTL before any medical treatment. Microarrays were utilized to investigate differential whole blood gene expression between TPTL women who did (n = 48) or did not have a sPTB (n = 106) within 48 hours of admission. Total leukocyte and neutrophil counts were significantly higher (35% and 41% respectively) in women who had sPTB than women who did not deliver within 48 hours (p<0.001). Fetal fibronectin (fFN) test was performed on 62 women. There was no difference in the urine, vaginal and placental microbiology and histopathology reports between the two groups of women. There were 469 significant differentially expressed genes (FDR<0.05); 28 differentially expressed genes were chosen for microarray validation using qRT-PCR and 20 out of 28 genes were successfully validated (p<0.05). An optimal random forest classifier model to predict sPTB was achieved using the top nine differentially expressed genes coupled with peripheral clinical blood data (sensitivity 70.8%, specificity 75.5%). These differentially expressed genes may further elucidate the underlying mechanisms of sPTB and pave the way for future systems biology studies to predict sPTB.

Transcriptome interrogation of human myometrium identifies differentially expressed sense-antisense pairs of protein-coding and long non-coding RNA genes in spontaneous labor at term

OBJECTIVE

To identify differentially expressed long non-coding RNA (lncRNA) genes in human myometrium in women with spontaneous labor at term.

MATERIALS AND METHODS

Myometrium was obtained from women undergoing cesarean deliveries who were not in labor (n = 19) and women in spontaneous labor at term (n = 20). RNA was extracted and profiled using an Illumina® microarray platform. We have used computational approaches to bound the extent of long non-coding RNA representation on this platform, and to identify co-differentially expressed and correlated pairs of long non-coding RNA genes and protein-coding genes sharing the same genomic loci.

RESULTS

We identified co-differential expression and correlation at two genomic loci that contain coding-lncRNA gene pairs: SOCS2-AK054607 and LMCD1-NR_024065 in women in spontaneous labor at term. This co-differential expression and correlation was validated by qRT-PCR, an experimental method completely independent of the microarray analysis. Intriguingly, one of the two lncRNA genes differentially expressed in term labor had a key genomic structure element, a splice site, that lacked evolutionary conservation beyond primates.

CONCLUSIONS

We provide, for the first time, evidence for coordinated differential expression and correlation of cis-encoded antisense lncRNAs and protein-coding genes with known as well as novel roles in pregnancy in the myometrium of women in spontaneous labor at term.