Amniotic fluid cell-free DNA in preterm prelabor rupture of membranes

Trafficking and effect of released DNA on cGAS-STING signaling pathway and cardiovascular disease

Evidence from clinical research and animal studies indicates that inflammation is an important factor in the occurrence and development of cardiovascular disease (CVD). Emerging evidence shows that nucleic acids serve as crucial pathogen-associated molecular patterns (PAMPs) or non-infectious damage-associated molecular patterns (DAMPs), are released and then recognized by pattern recognition receptors (PRRs), which activates immunological signaling pathways for host defense. Mechanistically, the released nucleic acids activate cyclic GMP-AMP synthase (cGAS) and its downstream receptor stimulator of interferon genes (STING) to promote type I interferons (IFNs) production, which play an important regulatory function during the initiation of an innate immune response to various diseases, including CVD. This pathway represents an essential defense regulatory mechanism in an organism's innate immune system. In this review, we outline the overall profile of cGAS-STING signaling, summarize the latest findings on nucleic acid release and trafficking, and discuss their potential role in CVD. This review also sheds light on potential directions for future investigations on CVD.

Fetal DNA Causes Sex-Specific Inflammation From Human Fetal Membranes

Inflammation is central to the mechanisms of parturition, but the lack of understanding of how it is controlled in normal parturition hampers our ability to understand how it may diverge resulting in preterm birth. Cell-free fetal DNA is found in the amniotic fluid, and it is thought to be able to activate inflammation as a danger-associated molecular pattern. Although its levels increases with gestational age, its effect has not been studied on the human fetal membranes. Thus, the aim of this study was to determine if the fetal DNA can trigger inflammation in the human fetal membranes and, thus, potentially contribute to the inflammatory load. Isolated human amniotic epithelial cells and fetal membrane explants were treated apically with fetal DNA causing the translocation of NF-KB into the nucleus of cells and throughout the cells of the explant layers with time. Fetal membrane explants were treated apically with either small or larger fragments of fetal DNA. IL-6, TNFα, and GM-CSF secretion was measured by ELISA, and pro-MMP2 and pro-MMP9 activity was measured by zymography from apical and basal media. Increased apical IL-6 secretion and basal pro-MMP2 activity was seen with small fragments of fetal DNA. When the data were disaggregated based on fetal sex, males had significant increases in IL-6 secretion and basal increased activity in pro-MMP2 and 9, whereas females had significantly increased basal secretion of TNFα. This was caused by the smaller fragments of fetal DNA, whereas the larger fragments did not cause any significant increases. Male fetal DNA had significantly lower percentages of methylation than females. Thus, when the cytokine and pro-MMP activity data were correlated with methylation percentage, IL-6 secretion significantly correlated negatively, whereas GM-CSF secretion positively correlated. These data support the role of fetal DNA as an inflammatory stimulus in the FM, as measured by increased NF-κB translocation, cytokine secretion, and increased pro-MMP activity. However, the data also suggested that the responses are different from FM tissues of male and female fetuses, and both the fragment size and methylation status of the fetal DNA can influence the magnitude and type of molecule secreted.

Prevalence and Load of Cervical Ureaplasma Species With Respect to Intra-amniotic Complications in Women With Preterm Prelabor Rupture of Membranes Before 34 weeks

Objectives: To determine the prevalence and load of Ureaplasma spp. DNA in the cervical fluid of women with singleton pregnancies complicated by preterm prelabor rupture of membranes (PPROM) with respect to intra-amniotic infection, sterile intra-amniotic inflammation, and colonization of the amniotic fluid.

Methods: A total of 217 women with PPROM between gestational ages 24 + 0 and 33 + 6 weeks were included in this study. Paired amniotic and cervical fluid samples were collected at the time of admission via transabdominal amniocentesis and using a Dacron polyester swab, respectively. Microbial invasion of the amniotic cavity was diagnosed using a combination of culture and molecular biology methods. Intra-amniotic inflammation was determined based on the concentration of interleukin-6 in the amniotic fluid. Based on the presence or absence of these conditions, the women were stratified into the following subgroups: intra-amniotic infection (with both), sterile intra-amniotic inflammation (with inflammation only), colonization (with microorganisms only), and negative amniotic fluid (without either). The Ureaplasma spp. DNA load in the cervical fluid was assessed using PCR.

Results:Ureaplasma spp. DNA in the cervical fluid was found in 61% (133/217) of the women. Women with negative amniotic had similar prevalence of Ureaplasma spp. DNA in cervical fluid (55%) to those with sterile intra-amniotic inflammation (54%) but lower than those with intra-amniotic infection (73%) and colonization (86%; p < 0.0001). Women with negative amniotic fluid had a lower load of Ureaplasma spp. DNA in their cervical fluid (median: 4.7 × 10³ copies of DNA/ml) than those with intra-amniotic infection (median: 2.8 × 10⁵ copies DNA/ml), sterile intra-amniotic inflammation (median: 5.3 × 10⁴ copies DNA/ml), and colonization (median: 1.2 × 10⁵ copies DNA/mL; p < 0.0001).

Conclusion: In conclusion, in PPROM at <34 weeks, the presence of intra-amniotic infection, sterile intra-amniotic inflammation, or colonization of the amniotic fluid was associated with a higher prevalence and/or load of Ureaplasma spp. DNA in the cervical fluid than the absence of intra-amniotic complications.

The Role of Innate Immune System in the Human Amniotic Membrane and Human Amniotic Fluid in Protection Against Intra-Amniotic Infections and Inflammation

Intra-amniotic infection and inflammation (IAI) affect fetal development and are highly associated with preterm labor and premature rupture of membranes, which often lead to adverse neonatal outcomes. Human amniotic membrane (hAM), the inner part of the amnio-chorionic membrane, protects the embryo/fetus from environmental dangers, including microbial infection. However, weakened amnio-chorionic membrane may be breached or pathogens may enter through a different route, leading to IAI. The hAM and human amniotic fluid (hAF) respond by activation of all components of the innate immune system. This includes changes in 1) hAM structure, 2) presence of immune cells, 3) pattern recognition receptors, 4) cytokines, 5) antimicrobial peptides, 6) lipid derivatives, and 7) complement system. Herein we provide a comprehensive and integrative review of the current understanding of the innate immune response in the hAM and hAF, which will aid in design of novel studies that may lead to breakthroughs in how we perceive the IAI.

Relationship between amniotic fluid metabolic profile with fetal gender, maternal age, and gestational week

BACKGROUND

Amniotic fluid (AF) provides vital information on fetal development, which is also valuable in identifying fetal abnormalities during pregnancy. However, the relationship between the metabolic profile of AF in the second trimester of a normal pregnancy with several maternal-fetal parameters remains poorly understood, which therefore limits its application in clinical practice. The aim of this study was to explore the association between the metabolic profile of AF with fetal gender, maternal age, and gestational week using an untargeted metabolomics method.

METHODS

A total of 114 AF samples were analyzed in this study. Clinical data on fetal gender, maternal age, and gestational week of these samples were collected. Samples were analyzed by gas chromatography/time-of-flight-mass spectrometry (GC-TOF/MS). Principal component analysis(PCA), orthogonal partial least square discrimination analysis(OPLS-DA) or partial least square discrimination analysis (PLS-DA) were conducted to compare metabolic profiles, and differential metabolites were obtained by univariate analysis.

RESULTS

Both PCA and OPLS-DA demonstrated no significant separation trend between the metabolic profiles of male and female fetuses, and there were only 7 differential metabolites. When the association between the maternal age on AF metabolic profile was explored, both PCA and PLS-DA revealed that the maternal age in the range of 21 to 40 years had no significant effect on the metabolic profile of AF, and only four different metabolites were found. There was no significant difference in the metabolic profiles of AF from fetuses of 17-22 weeks, and 23 differential metabolites were found.

CONCLUSIONS

In the scope of our study, there was no significant correlation between the AF metabolic profile and the fetal gender, maternal age and gestational week of a small range. Nevertheless, few metabolites appeared differentially expressed.

Pathophysiological Implication of Pattern Recognition Receptors in Fetal Membranes Rupture: RAGE and NLRP Inflammasome

Preterm prelabor ruptures of fetal membranes (pPROM) are a pregnancy complication responsible for 30% of all preterm births. This pathology currently appears more as a consequence of early and uncontrolled process runaway activation, which is usually implicated in the physiologic rupture at term: inflammation. This phenomenon can be septic but also sterile. In this latter case, the inflammation depends on some specific molecules called “alarmins” or “damage-associated molecular patterns” (DAMPs) that are recognized by pattern recognition receptors (PRRs), leading to a microbial-free inflammatory response. Recent data clarify how this activation works and which receptor translates this inflammatory signaling into fetal membranes (FM) to manage a successful rupture after 37 weeks of gestation. In this context, this review focused on two PRRs: the receptor for advanced glycation end-products (RAGE) and the NLRP7 inflammasome.

Deoxyribonuclease activity negative correlates with extracellular DNA in uncomplicated singleton pregnancies in the third trimester

OBJECTIVES

It is not clear, which factors affect extracellular DNA (ecDNA) concentrations in healthy women with singleton uncomplicated pregnancies, although deoxyribonucleases (DNases) are hypothesized to be responsible for the cleavage of plasma ecDNA. The aim of this study was to analyze potential determinants of total ecDNA including plasma DNase activity.

METHODS

Plasma samples were collected from 48 healthy women with singleton uncomplicated pregnancies in the third trimester (gestation week 37). DNA was isolated and quantified using fluorometry and real time PCR. DNase activity was assessed using the single radial enzyme-diffusion method.

RESULTS

Neither ecDNA, nor DNase activity were affected by maternal age or BMI. DNase activity negatively correlated with total plasma ecDNA (r=-0.40, p=0.007). Similar associations were found for ecDNA of nuclear and mitochondrial origin, but not with fetal DNA quantified using Y-targeted PCR in male fetus-bearing pregnancies.

CONCLUSIONS

The role of plasma ecDNA of fetal and maternal origin is studied in the pathogenesis of pregnancy-complications. The results indicate that plasma DNase activity could negatively regulate ecDNA concentrations and should, thus, be analyzed in preeclampsia, preterm birth and other ecDNA-related pregnancy complications.

Transabdominal amniocentesis in expectant management of preterm premature rupture of membranes: A single center prospective study

AIMS

The aim of this study was to evaluate the role of IL-6 point-of-care test in amniotic fluid obtained from serial amniocentesis in expectantly managed women with PPROM between 24 and 34 weeks of gestation.

METHODS

We conducted a prospective observational cohort study which included 62 pregnant women with PPROM in gestational weeks between 22+0 and 34+0. Women aged >18 years were eligible if they presented with PPROM and a singleton pregnancy. Only women who delivered at >24.0 weeks were included in the study. In all women, the maternal blood sampling and a transabdominal amniocentesis were performed at the time of admission prior to the administration of corticosteroids, antibiotics, or tocolytics, to rule out signs of chorioamnionitis. Maternal temperature, maternal serum C-reactive protein (CRP) and white blood cell (WBC) counts were assayed every subsequent day until delivery. Amniotic fluid was used for the clinical assessment (IL-6 point-of-care test, identification of microorganisms in the amniotic fluid. After one week of expectant management of PPROM, second amniocentesis with amniotic fluid sampling was performed in patients who did not deliver. For all newborns, medical records regarding neonatal morbidity and mortality were reviewed.

RESULTS

In total, 62 women aged 19 to 41 years were recruited in the study. The mean gestational age at the time of PPROM was 31+0, the mean gestational age at labor was 32+1, and the median time from PPROM to childbirth was 112 h. IL-6 point-of-care test values above 1,000 pg/mL (positive Il-6 AMC) were found in 12 women (19.4%) with median interval from PPROM to childbirth 56 h (min-max: 6.4-288). IL-6 point-of-care test values below 1,000 pg/mL (negative Il-6 AMC) were found in 51 women (81.0%). The neonatal mortality rate was 1.9% and was associated with prematurity.

CONCLUSION

The major clinical finding of our study is that serial transabdominal amniocentesis with Il-6 point-of-care test helps to identify a high inflammatory status in amniotic fluid in women with PPROM. Subsequent expectant management of women with PPROM does not lead to worsening of short-term neonatal outcomes.

Antibiotic administration reduces the rate of intraamniotic inflammation in preterm prelabor rupture of the membranes

BACKGROUND

Preterm prelabor rupture of the membranes (PPROM) is frequently complicated by intraamniotic inflammatory processes such as intraamniotic infection and sterile intraamniotic inflammation. Antibiotic therapy is recommended to patients with PPROM to prolong the interval between this complication and delivery (latency period), reduce the risk of clinical chorioamnionitis, and improve neonatal outcome. However, there is a lack of information regarding whether the administration of antibiotics can reduce the intensity of the intraamniotic inflammatory response or eradicate microorganisms in patients with PPROM.

OBJECTIVE

The first aim of the study was to determine whether antimicrobial agents can reduce the magnitude of the intraamniotic inflammatory response in patients with PPROM by assessing the concentrations of interleukin-6 in amniotic fluid before and after antibiotic treatment. The second aim was to determine whether treatment with intravenous clarithromycin changes the microbial load of Ureaplasma spp DNA in amniotic fluid.

STUDY DESIGN

A retrospective cohort study included patients who had (1) a singleton gestation, (2) PPROM between 24+0 and 33+6 weeks, (3) a transabdominal amniocentesis at the time of admission, and (4) intravenous antibiotic treatment (clarithromycin for patients with intraamniotic inflammation and benzylpenicillin/clindamycin in the cases of allergy in patients without intraamniotic inflammation) for 7 days. Follow-up amniocenteses (7^th day after admission) were performed in the subset of patients with a latency period lasting longer than 7 days. Concentrations of interleukin-6 were measured in the samples of amniotic fluid with a bedside test, and the presence of microbial invasion of the amniotic cavity was assessed with culture and molecular microbiological methods. Intraamniotic inflammation was defined as a bedside interleukin-6 concentration ≥745 pg/mL in the samples of amniotic fluid. Intraamniotic infection was defined as the presence of both microbial invasion of the amniotic cavity and intraamniotic inflammation; sterile intraamniotic inflammation was defined as the presence of intraamniotic inflammation without microbial invasion of the amniotic cavity.

RESULTS

A total of 270 patients with PPROM were included in this study: 207 patients delivered within 7 days and 63 patients delivered after 7 days of admission. Of the 63 patients who delivered after 7 days following the initial amniocentesis, 40 underwent a follow-up amniocentesis. Patients with intraamniotic infection (n = 7) and sterile intraamniotic inflammation (n = 7) were treated with intravenous clarithromycin. Patients without either microbial invasion of the amniotic cavity or intraamniotic inflammation (n = 26) were treated with benzylpenicillin or clindamycin. Treatment with clarithromycin decreased the interleukin-6 concentration in amniotic fluid at the follow-up amniocentesis compared to the initial amniocentesis in patients with intraamniotic infection (follow-up: median, 295 pg/mL, interquartile range [IQR], 72-673 vs initial: median, 2973 pg/mL, IQR, 1750-6296; P = .02) and in those with sterile intraamniotic inflammation (follow-up: median, 221 pg/mL, IQR 118-366 pg/mL vs initial: median, 1446 pg/mL, IQR, 1300-2941; P = .02). Samples of amniotic fluid with Ureaplasma spp DNA had a lower microbial load at the time of follow-up amniocentesis compared to the initial amniocentesis (follow-up: median, 1.8 × 10⁴ copies DNA/mL, 2.9 × 10⁴ to 6.7 × 10⁸ vs initial: median, 4.7 × 10⁷ copies DNA/mL, interquartile range, 2.9 × 10³ to 3.6 × 10⁷; P = .03).

CONCLUSION

Intravenous therapy with clarithromycin was associated with a reduction in the intensity of the intraamniotic inflammatory response in patients with PPROM with either intraamniotic infection or sterile intraamniotic inflammation. Moreover, treatment with clarithromycin was related to a reduction in the load of Ureaplasma spp DNA in the amniotic fluid of patients with PPROM <34 weeks of gestation.

Exosomes-Associated DNA-New Marker in Pregnancy Complications?

Despite a large number of studies, the etiology of pregnancy complications remains unknown. The involvement of cell-free DNA or fetal cell-free DNA in the pathogenesis of pregnancy complications is currently being hypothesized. Cell-free DNA occurs in different forms-free; part of neutrophil extracellular traps; or as recently discovered, carried by extracellular vesicles. Cell-free DNA is believed to activate an inflammatory pathway, which could possibly cause pregnancy complications. It could be hypothesized that DNA in its free form could be easily degraded by nucleases to prevent the inflammatory activation. However, recently, there has been a growing interest in the role of exosomes, potential protectors of cell-free DNA, in pregnancy complications. Most of the interest from recent years is directed towards the micro RNA carried by exosomes. However, exosome-associated DNA in relation to pregnancy complications has not been truly studied yet. DNA, as an important cargo of exosomes, has been so far studied mostly in cancer research. This review collects all the known information on the topic of not only exosome-associated DNA but also some information on vesicles-associated DNA and the studies regarding the role of exosomes in pregnancy complications from recent years. It also suggests possible analysis of exosome-associated DNA in pregnancy from plasma and emphasizes the importance of such analysis for future investigations of pregnancy complications. A major obstacle to the advancement in this field is the proper uniformed technique for exosomes isolation. Similarly, the sensitivity of methods analyzing a small fraction of DNA, potentially fetal DNA, carried by exosomes is variable.

Association between periodontal disease and preterm prelabour rupture of membranes

OBJECTIVE

Periodontal disease is a possible contributing factor to preterm delivery. The aim of this study was to compare the periodontal status of women with preterm prelabour rupture of membranes (PPROM) and women with uncomplicated singleton pregnancies.

PATIENTS AND METHODS

Seventy-eight women with PPROM at gestational ages between 24 + 0 and 36 + 6 weeks and 77 healthy women with uncomplicated pregnancies, matched for gestational age at sampling without preterm birth, were included in this study. All women underwent evaluation of periodontal and oral hygiene status.

RESULTS

Women with PPROM had higher gingival and plaque indexes in crude analysis (gingival index: median 0.80 versus 0.20; p < 0.0001; plaque index: median 0.80 versus 0.10; p < 0.0001), even after adjustment for smoking status (p < 0.0001 and p < 0.0001). Mean clinical attachment loss (CAL) and probing pocket depth (PPD) values were higher in women with PPROM in the crude analysis (CAL: median 2.3 mm versus 1.8 mm; p < 0.0001; PPD: median 2.3 mm versus 1.8; p < 0.0001), as well as after adjustment for smoking status (p < 0.0001 and p < 0.0001).

CONCLUSIONS

Pregnant women with PPROM residing in central Europe had worse periodontal status than women with uncomplicated pregnancies.