In the past decade, extracellular vesicles (EVs) have been recognized as potent vehicles of intercellular communication, both in prokaryotes and eukaryotes. This is due to their capacity to transfer proteins, lipids and nucleic acids, thereby influencing various physiological and pathological functions of both recipient and parent cells. While intensive investigation has targeted the role of EVs in different pathological processes, for example, in cancer and autoimmune diseases, the EV-mediated maintenance of homeostasis and the regulation of physiological functions have remained less explored. Here, we provide a comprehensive overview of the current understanding of the physiological roles of EVs, which has been written by crowd-sourcing, drawing on the unique EV expertise of academia-based scientists, clinicians and industry based in 27 European countries, the United States and Australia. This review is intended to be of relevance to both researchers already working on EV biology and to newcomers who will encounter this universal cell biological system. Therefore, here we address the molecular contents and functions of EVs in various tissues and body fluids from cell systems to organs. We also review the physiological mechanisms of EVs in bacteria, lower eukaryotes and plants to highlight the functional uniformity of this emerging communication system.

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Biological properties of extracellular vesicles and their physiological functions

Background 
Preterm delivery causes substantial neonatal mortality and morbidity. Unrecognized intra-amniotic infections caused by cultivation-resistant microbes may play a role. Molecular methods can detect, characterize and quantify microbes independently of traditional culture techniques. However, molecular studies that define the diversity and abundance of microbes invading the amniotic cavity, and evaluate their clinical significance within a causal framework, are lacking.


Methods and Findings 
In parallel with culture, we used broad-range end-point and real-time PCR assays to amplify, identify and quantify ribosomal DNA (rDNA) of bacteria, fungi and archaea from amniotic fluid of 166 women in preterm labor with intact membranes. We sequenced up to 24 rRNA clones per positive specimen and assigned taxonomic designations to approximately the species level. Microbial prevalence, diversity and abundance were correlated with host inflammation and with gestational and neonatal outcomes. Study subjects who delivered at term served as controls. The combined use of molecular and culture methods revealed a greater prevalence (15% of subjects) and diversity (18 taxa) of microbes in amniotic fluid than did culture alone (9.6% of subjects; 11 taxa). The taxa detected only by PCR included a related group of fastidious bacteria, comprised of Sneathia sanguinegens, Leptotrichia amnionii and an unassigned, uncultivated, and previously-uncharacterized bacterium; one or more members of this group were detected in 25% of positive specimens. A positive PCR was associated with histologic chorioamnionitis (adjusted odds ratio [OR] 20; 95% CI, 2.4 to 172), and funisitis (adjusted OR 18; 95% CI, 3.1 to 99). The positive predictive value of PCR for preterm delivery was 100 percent. A temporal association between a positive PCR and delivery was supported by a shortened amniocentesis-to-delivery interval (adjusted hazard ratio 4.6; 95% CI, 2.2 to 9.5). A dose-response association was demonstrated between bacterial rDNA abundance and gestational age at delivery (r2 = 0.42; P<0.002).


Conclusions 
The amniotic cavity of women in preterm labor harbors DNA from a greater diversity of microbes than previously suspected, including as-yet uncultivated, previously-uncharacterized taxa. The strength, temporality and gradient with which these microbial sequence types are associated with preterm delivery support a causal relationship.

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Microbial Prevalence, Diversity and Abundance in Amniotic Fluid During Preterm Labor: A Molecular and Culture-Based Investigation

Background: This study was undertaken to characterize the vaginal microbiota throughout normal human pregnancy using sequence-based techniques. We compared the vaginal microbial composition of non-pregnant patients with a group of pregnant women who delivered at term. Results: A retrospective case–control longitudinal study was designed and included non-pregnant women (n = 32) and pregnant women who delivered at term (38 to 42 weeks) without complications (n = 22). Serial samples of vaginal fluid were collected from both non-pregnant and pregnant patients. A 16S rRNA gene sequence-based survey was conducted using pyrosequencing to characterize the structure and stability of the vaginal microbiota. Linear mixed effects models and generalized estimating equations were used to identify the phylotypes whose relative abundance was different between the two study groups. The vaginal microbiota of normal pregnant women was different from that of non-pregnant women (higher abundance of Lactobacillus vaginalis, L. crispatus, L. gasseri and L. jensenii and lower abundance of 22 other phylotypes in pregnant women). Bacterial community state type (CST) IV-B or CST IV-A characterized by high relative abundance of species of genus Atopobium as well as the presence of Prevotella, Sneathia, Gardnerella, Ruminococcaceae, Parvimonas, Mobiluncus and other taxa previously shown to be associated with bacterial vaginosis were less frequent in normal pregnancy. The stability of the vaginal microbiota of pregnant women was higher than that of non-pregnant women; however, during normal pregnancy, bacterial communities shift almost exclusively from one CST dominated by Lactobacillus spp. to another CST dominated by Lactobacillus spp. Conclusion: We report the first longitudinal study of the vaginal microbiota in normal pregnancy. Differences in the composition and stability of the microbial community between pregnant and non-pregnant women were observed. Lactobacillus spp. were the predominant members of the microbial community in normal pregnancy. These results can serve as the basis to study the relationship between the vaginal microbiome and adverse pregnancy outcomes.

/pdf/the-composition-and-stability-of-the-vaginal-microbiota-of-2ovue5t683.pdf

The composition and stability of the vaginal microbiota of normal pregnant women is different from that of non-pregnant women

Acute chorioamnionitis and funisitis: definition, pathologic features, and clinical significance.

Predictive value for preterm birth of abnormal vaginal flora, bacterial vaginosis and aerobic vaginitis during the first trimester of pregnancy

Mycoplasma hominis and Ureaplasma urealyticum in midtrimester amniotic fluid: Association with amniotic fluid cytokine levels and pregnancy outcome

Objective

To assess the intra- and interobserver reproducibility of ultrasound measurements of fetal biometric parameters.



Methods

We assessed the intraobserver and the interobserver agreement in measurements of fetal biparietal diameter (BPD), abdominal circumference (AC), head circumference (HC) and femur length (FL) on 122 singleton pregnancies. Patients were each examined twice by the first sonographer to determine the intraobserver reliability of measurements of fetal biometry. Subsequently, during the same ultrasound examination, a second blinded sonographer measured fetal biometric parameters to assess interobserver reliability. The consensus between and among observers was analyzed using the intraclass correlation coefficient (intra-CC) and interclass correlation coefficient (inter-CC) and the reliability coefficients (RC, α) for the four biometric measurements. A value > 0.75 was considered a reliable consensus for the intra-CC and inter-CC. A Bland and Altman plot was also created for the fetal biometric parameters to assess the repeatability of the measurements.



Results

Reliable consensus was observed for both the intra-CC and inter-CC and RC for all four biometric parameters. The intra-CC with the 95% CI and RC for the BPD, AC, HC and FL were as follows: 0.996 (0.995, 0.997), α 0.998; 0.994 (0.992, 0.996), α 0.997; 0.996 (0.994, 0.997), α 0.998; and 0.994 (0.992, 0.996), α 0.997, respectively. Similarly, the inter-CC with the 95% CI and RC for the same parameters were as follows: 0.995 (0.993, 0.997), α 0.998; 0.980 (0.971, 0.990), α 0.990; 0.994 (0.992, 0.996), α 0.997; and 0.990 (0.985,0.993), α 0.995, respectively. The Bland and Altman plots demonstrated a high degree of repeatability of BPD, AC, HC, and FL measurements.



Conclusion

Our results demonstrate that the intra- and interobserver reproducibility of ultrasound measurements of fetal biometry are highly reliable. Copyright © 2004 ISUOG. Published by John Wiley & Sons, Ltd.

https://obgyn.onlinelibrary.wiley.com/doi/epdf/10.1002/uog.1717

Sriram C. Perni

Papers

Mycoplasma hominis and Ureaplasma urealyticum in midtrimester amniotic fluid: Association with amniotic fluid cytokine levels and pregnancy outcome

Intraobserver and interobserver reproducibility of fetal biometry

First trimester prediction of growth discordance in twin gestations

Interleukin-4 and -10 gene polymorphisms and spontaneous preterm birth in multifetal gestations.

Ultrasound evaluation of abnormal umbilical cord coiling in second trimester of gestation in association with adverse pregnancy outcome