Relationship of circulating cell-free DNA levels to cell-free fetal DNA levels, clinical characteristics and laboratory parameters in preeclampsia

Association between fetal fraction of cell-free DNA and adverse pregnancy outcomes

PURPOSE

To determine the association between fetal fraction (FF) levels in cell-free fetal DNA (cffDNA) testing and adverse pregnancy outcomes.

METHODS

This retrospective cohort study, conducted at a single center, involved 2063 pregnant women with normal 1st and 2nd trimester non-invasive prenatal test (NIPT) results between 2016 and 2021. Pregnancy outcomes were examined by determining the  < 4% and  < 5th percentile (3.6%) cut-off values for low fetal fraction (LFF). Pregnancy outcomes were also examined by dividing the FF into population-based quartiles. Adverse pregnancy outcomes were pregnancy-induced hypertensive diseases (PIHD), gestational diabetes mellitus (GDM), spontaneous preterm birth (PTB), intrahepatic cholestasis of pregnancy (ICP), small for gestational age (SGA), large for gestational age (LGA), low birth weight (LBW), macrosomia, and 1st and 5th minutes low APGAR scores (< 7).

RESULTS

PIHD was significantly higher in LFF (< 4% and  < 5th percentile) cases (p = 0.015 and p < 0.001, respectively). However, in population-based quartiles of FF, PIHD did not differ significantly between groups. Composite adverse maternal outcomes were significantly higher in the FF < 4% group (p = 0.042). When analyzes were adjusted for maternal age, BMI, and gestational age at NIPT, significance was maintained at  < 4%,  < 5th percentile LFF for PIHD, and  < 4% LFF for composite adverse maternal outcomes. However, there was no significant relationship between LFF with GDM, ICP and PTB. Additionally, there was no significant association between low APGAR scores, SGA, LGA, LBW, macrosomia, and LFF concerning neonatal outcomes.

CONCLUSION

Our study showed that LFF in pregnant women with normal NIPT results may be a predictor of subsequent PIHD.

Cell‑free fetal DNA at 11‑13 weeks of gestation is not altered in complicated pregnancies

Non-invasive maternal cell-free fetal DNA (cffDNA) is a promising biomarker for screening common genetic syndromes. Alterations in the expression levels of cffDNA in the maternal circulation have been demonstrated in abnormal pregnancies. However, the results are conflicting. The present study aimed to investigate whether cffDNA levels are associated with pregnancy complications. The study group comprised pregnant women who presented with pregnancy complications, such as preterm birth, gestational hypertension, intrauterine growth retardation, gestational diabetes, polyhydramnios, oligohydramnios, vaginal bleeding and placental abruption. The control group comprised women who had a normal pregnancy course. Blood samples were obtained from 500 pregnant women between 11-13 weeks of gestation. cffDNA was amplified, sequenced and analyzed using the next-generation aneuploidy test of a Panorama-Natera kit. Nuchal translucency (NT) thickness as well as pregnancy associated plasma protein-A (PAPP-A) and β-human chorionic gonadotropin (β-hCG) levels were also assessed. Statistical analysis was performed in 494 out of the 500 samples collected with SPSS v.26 using non-parametric methods. The parameters were normalized by the multiples of median (MoM) method. The expression levels of PAPP-A, β-hCG, and the NT mean MoM values were significantly different between the study and control groups (P=0.005, P<0.001 and P=0.007, respectively). However, the expression levels of cffDNA and the mean MoM values were not significantly different between these two groups (P=0.687). The findings of the present study support the conclusion that cffDNA expression is not altered in a series of pregnancy complications. The prognostic value of cffDNA in predicting adverse pregnancy outcomes requires further investigation.

A Reliable Method for Quantifying Plasma Cell-Free DNA Using an Internal Standard Strategy: Evaluation in a Cohort of Non-Pregnant and Pregnant Women

The use of plasma cell-free DNA (cfDNA) as a useful biomarker in obstetric clinical practice has been delayed due to the lack of reliable quantification protocols. We developed a protocol to quantify plasma cfDNA using an internal standard strategy to overcome difficulties posed by low levels and high fragmentation of cfDNA. cfDNA was isolated from plasma samples of non-pregnant (NP, n = 26) and pregnant (P, n = 26) women using a commercial kit and several elution volumes were evaluated. qPCR parameters were optimized for cfDNA quantification, and several quantities of a recombinant standard were evaluated as internal standard. Absolute quantification was performed using a standard curve and the quality of the complete method was evaluated. cfDNA was eluted in a 50-μl volume, actin-β (ACTB) was selected as the target gene, and qPCR parameters were optimized. The ACTB standard was constructed and 1000 copies were selected as internal standard. The standard curve showed R2 = 0.993 and E = 109.7%, and the linear dynamic range was defined between 102 and 106 ACTB copies/tube. Repeatability and reproducibility in terms of CV were 19% and up to 49.5% for ACTB copies per milliliter of plasma, respectively. The range of cfDNA levels was 428-18,851 copies/mL in NP women and 4031-2,019,363 copies/mL in P women, showing significant differences between the groups. We recommend the application of internal standard strategy for a reliable plasma cfDNA quantification. This methodology holds great potential for a future application in the obstetric field.

Etiological Value of Sterile Inflammation in Preeclampsia: Is It a Non-Infectious Pregnancy Complication?

Understanding of sterile inflammation and its associated biological triggers and diseases is still at the elementary stage. This becomes more warranted in cases where infections are not associated with the pathology. Detrimental effects of bacterial and viral infections on the immune responses at the maternal-fetal interface as well as pregnancy outcomes have been well documented. However, an infection-induced etiology is not thought to be a major contributing component to severe pregnancy complications such as preeclampsia (PE) and gestational diabetes. How is then an inflammatory signal thought to be associated with these pregnancy complications? It is not clear what type of inflammation is involved in the onset of PE-like features. We opine that sterile inflammation regulated by the inflammasome-gasdermins-caspase-1 axis is a contributory factor to the onset of PE. We hypothesize that increased production and release of damage-associated molecular patterns (DAMPs) or Alarmins such as high-mobility group box1 (HMGB1), cell-free fetal DNA, uric acid, the NOD-like receptor pyrin-containing receptor 3 (NLRP3) inflammasome, IL-1β and IL-18 occur in the PE placenta. Some of these molecules have already been observed in the placenta from women with PE. Mechanistically, emerging evidence has demonstrated that excessive placental endoplasmic reticulum (ER) stress, impaired autophagy and gasdermine D (GSDMD)-mediated intrinsic pyroptosis are key events that contribute to systemic sterile inflammation in patients with PE, especially early-onset PE (e-PE). In this review, we highlight the advances on the roles of sterile inflammation and inflammatory signaling cascades involving ER stress, autophagy deficiency and pyroptosis in PE pathophysiology. Deciphering the mechanisms underlying these inflammatory pathways may provide potential diagnostic biomarkers and facilitate the development of therapeutic strategies to treat this devastating disease.

Association between low fetal fraction in cell-free DNA testing and adverse pregnancy outcome: A systematic review

Objective

Low fetal fraction (LFF) in prenatal cell‐free DNA (cfDNA) testing is an important cause of test failure and no‐call results. LFF might reflect early abnormal placentation and therefore be associated with adverse pregnancy outcome. Here, we review the available literature on the relationship between LFF in cfDNA testing and adverse pregnancy outcome.

Method

A systematic literature search was conducted in MEDLINE and EMBASE up to November 1, 2020.

Results

Five studies met the criteria for inclusion; all were retrospective observational cohort studies. The cohort sizes ranged from 370 to 6375 pregnancies, with all tests performed in the first trimester or early second trimester. A 4% cutoff for LFF was used in two studies, two studies used the 5th and 25th percentiles, respectively, and one study used a variety of cutoff values for LFF. LFF in prenatal cfDNA testing was observed to be associated with hypertensive disease of pregnancy, small for gestational age neonates, and preterm birth. Conflicting results were found regarding the association between LFF and gestational diabetes mellitus.

Conclusions

LFF in cfDNA testing is associated with adverse pregnancy outcome,specifically pregnancy‐related hypertensive disorders, preterm birth, and impaired fetal growth related to placental dysfunction. Since the available evidence is limited, a large prospective cohort study on the relationship between fetal fraction and pregnancy outcomes is needed.

What's already known about this topic?

Low fetal fraction (LFF) in prenatal cell‐free DNA (cfDNA) testing is an important cause of test failure and no‐call results and has been associated with aneuploidy

LFF might also reflect early abnormal placentation and therefore be associated with adverse pregnancy outcome

What does this review add?

This review summarizes the available data on LFF in prenatal cfDNA testing and its relation to adverse pregnancy outcomes

LFF was found to be associated with pregnancy‐related hypertensive disorders, preterm birth, and impaired fetal growth related to placental dysfunction

Since the available evidence is limited, a large prospective cohort study on the relationship between fetal fraction and pregnancy outcomes is needed

At Preeclampsia Diagnosis, Total Cell-Free DNA Concentration is Elevated and Correlates With Disease Severity

Background

Placental derived cell‐free DNA (cfDNA), widely utilized for prenatal screening, may serve as a biomarker for preeclampsia. To determine whether cfDNA parameters are altered in preeclampsia, we conducted a case‐control study using prospectively collected maternal plasma (n=20 preeclampsia, n=22 normal) using our in‐house validated prenatal screening assay.

Methods and Results

Isolated cfDNA was quantified, sequenced using Illumina NextSeq 500, and the placental‐derived fraction was determined. Clinical and test characteristics were compared between preeclampsia and controls, followed by comparisons within the preeclampsia cohort dichotomized by cfDNA concentration. Lastly, cfDNA parameters in preeclampsia were correlated with markers of disease severity. Maternal age, body mass index, gestational age at delivery, cesarean rate, and neonatal birthweight were expectedly different between groups (P≤0.05). The placental‐derived cfDNA fraction did not differ between groups (21.4% versus 16.9%, P=0.06); however, total cfDNA was more than 10 times higher in preeclampsia (1235 versus 106.5 pg/µL, P<0.001). This relationship persisted when controlling for important confounders (OR 1.22, 95% CI 1.04–1.43, P=0.01). The dichotomized preeclampsia group with the highest cfDNA concentration delivered earlier (33.2 versus 36.6 weeks, P=0.02) and had lower placental‐derived fractions (9.1% versus 21.4%, P=0.04). Among preeclampsia cases, higher total cfDNA correlated with earlier gestational age at delivery (P=0.01) and higher maximum systolic blood pressure (P=0.04).

Conclusions

At diagnosis, total cfDNA is notably higher in preeclampsia, whereas the placental derived fraction remains similar to healthy pregnancies. In preeclampsia, higher total cfDNA correlates with earlier gestational age at delivery and higher systolic blood pressure. These findings may indicate increased release of cfDNA from maternal tissue injury.

Increased cell-free fetal DNA release after apoptosis and sterile inflammation in human trophoblast cells

PROBLEM

Cell-free fetal DNA (cffDNA) shed from the placenta can be detected in maternal blood and increases incrementally during gestation. Concentrations are further elevated with pregnancy complications. Specific activators of cffDNA release in such complications have not been identified. Here, we use trophoblast cells from early and term placenta to examine cffDNA release following apoptosis, infection, and sterile inflammatory stress.

METHOD OF STUDY

HTR8/SVneo cells were used to model first-trimester trophoblasts, and term cytotrophoblasts (CTBs) were isolated from placentae collected after uncomplicated deliveries. Trophoblasts were treated with varying concentrations of doxorubicin (DOX), lipopolysaccharide (LPS), or high-mobility group box protein 1 (HMGB1) for 18 h. Cells or supernatants were quantified for caspase-3/7 cleavage, pro-inflammatory cytokine secretion, and cffDNA release.

RESULTS

Both HTR8/SVneo and CTBs underwent caspase-3/7 cleavage following DOX treatment, with HTR8/SVneo cells more sensitive to apoptosis than term CTBs. Apoptotic cells released more cffDNA in a dose-dependent manner. Treatment with LPS resulted in an increase in pro-inflammatory IL-6 release, particularly in term CTBs compared to early trophoblasts; however, LPS did not affect cffDNA release. Lastly, while neither cell released more TNF-α following stimulation with HMGB1, both HTR8/SVneo and CTBs released significantly more cffDNA in the presence of HMGB1.

CONCLUSIONS

These data show that apoptosis and sterile inflammation induced by DOX and HMGB1, respectively, cause an increase in cffDNA concentrations in both first-trimester and term trophoblasts. Understanding physiologic release of cffDNA during healthy and complicated pregnancy can identify new targets for the diagnosis and treatment of gestational complications.

Circulating Total Cell-Free DNA Levels Are Increased in Hypertensive Disorders of Pregnancy and Associated with Prohypertensive Factors and Adverse Clinical Outcomes

Previous studies have described increased circulating cell-free DNA (cfDNA) in hypertensive disorders of pregnancy (HDP). Here, we aimed first to confirm this information using a simple, but sensible fluorescent assay, and second to investigate whether total cfDNA is associated with circulating factors known to be linked to the pathophysiology of HDP as well as with poor maternal-fetal outcomes. We studied 98 women with healthy pregnancies (HP), 88 with gestational hypertension (GH), and 91 with preeclampsia (PE). Total DNA was extracted from plasma using the QIAamp DNA blood mini kit and quantified using Quant-iT™ PicoGreen® dsDNA fluorescent detection kit. We found higher total cfDNA levels in GH and PE (197.0 and 174.2 ng/mL, respectively) than in HP (140.5 ng/mL; both p < 0.0001). Interestingly, total cfDNA levels were elevated in both male and female-bearing pregnancies diagnosed with either HDP, and in more severe versus less severe HDP cases, as classified according to responsiveness to antihypertensive therapy. In addition, total cfDNA was independently associated with HDP, and a cutoff concentration of 160 ng/mL provided appropriate sensitivity and specificity values for diagnosing GH and PE compared to HP (70-85%, both p < 0.0001). Moreover, high total cfDNA was associated with adverse clinical outcomes (high blood pressure, low platelet count, preterm delivery, fetal growth restriction) and high prohypertensive factors (sFLT-1, sEndoglin, MMP-2). These findings represent a step towards to the establishment of cfDNA as a diagnostic tool and the need to understand its role in HDP.

Genome-wide noninvasive prenatal diagnosis of monogenic disorders: Current and future trends

Noninvasive prenatal diagnosis (NIPD) is a risk-free alternative to invasive methods for prenatal diagnosis, e.g. amniocentesis. NIPD is based on the presence of fetal DNA within the mother’s plasma cell-free DNA (cfDNA). Though currently available for various monogenic diseases through detection of point mutations, NIPD is limited to detecting one mutation or up to several genes simultaneously. Noninvasive prenatal whole exome/genome sequencing (WES/WGS) has demonstrated genome-wide detection of fetal point mutations in a few studies. However, Genome-wide NIPD of monogenic disorders currently has several challenges and limitations, mainly due to the small amounts of cfDNA and fetal-derived fragments, and the deep coverage required. Several approaches have been suggested for addressing these hurdles, based on various technologies and algorithms. The first relevant software tool, Hoobari, recently became available. Here we review the approaches proposed and the paths required to make genome-wide monogenic NIPD widely available in the clinic.

Maternal total cell-free DNA in preeclampsia with and without intrauterine growth restriction

Elevation of total cell-free DNA (cfDNA) in patients with preeclampsia is well-known; however, whether this change precedes the onset of symptoms remains inconclusive. Here, we conducted a nested case-control study to determine the elevation of cfDNA levels in women who subsequently developed preeclampsia. Methylated HYP2 (m-HYP2) levels were determined in 68 blood samples collected from women with hypertensive disorders of pregnancy, along with 136 control samples, using real-time quantitative PCR. The measured m-HYP2 levels were converted to multiples of the median (MoM) values for correction of maternal characteristics. The m-HYP2 levels and MoM values in patients with preeclampsia were significantly higher than in controls during the third trimester (P < 0.001, both), whereas those for women who subsequently developed preeclampsia did not differ during the second trimester. However, when patients with preeclampsia were divided based on the onset-time of preeclampsia or 10th percentile birth weight, both values were significantly higher in women who subsequently developed early-onset preeclampsia (P < 0.05, both) and preeclampsia with small-for-gestational-age (SGA) neonate (P < 0.01, both) than controls. These results suggested that total cfDNA levels could be used to predict early-onset preeclampsia or preeclampsia with SGA neonate.

The potential of serum fetal DNA for early diagnosis of gestational trophoblastic disease

Objective:

To study cell-free DNA (cfDNA) levels in patients with gestational trophoblastic disease (GTD) in order to test the hypothesis that cfDNA circulating in maternal plasma could provide early detection of GTD.

Materials and Methods:

This study included 32 patients with GTD (complete mole and partial mole) and 30 non-GTD patients in the first trimester of pregnancy with no other medical problems. cfDNA levels in maternal serum were measured using polymerase chain reaction analysis on Y-chromosome–specific sequences.

Results:

cfDNA was found as 327±367 pg on average in the control group and 600±535 pg in the GTD group. Within the GTD group, the partial mole group had an cfDNA average of 636±549 pg, and the complete mole group had an cfDNA average of 563±536 pg. Although there was a statistically significant difference between the GTD group and the control group in terms of cfDNA (p=0.02), there was no statistically significant difference between the complete mole group and the partial mole group (p=0.76).

Conclusion:

Non-parametric analysis of covariance in terms of cfDNA in GTD was performed, thereby increasing its power and revealing a significant difference compared with the control group. This indicates that maternal peripheral bloodstream cfDNA monitoring might be significant in the early diagnosis of GTD.

[Cell-free DNA fraction: Can it be used to evaluate the risk of obstetrical issues?]

OBJECTIVE

The aim of the study was to evaluate if fetal cell-free DNA (cfDNA) fraction circulating in maternal blood at the beginning of the second trimester is associated with obstetrical complications.

METHODS

This is a retrospective unicentric study conducted at the hospital of Poissy Saint Germain between the 1^st January 2015, and the 31^st. December 2016, Each woman who had a genetic counseling in order to realize a non-invasive prenatal test (NIPT) was included. Only singleton pregnancies with a documented-issue were analysed. The primary criteria was a composite criteria, defined as the occurrence of preeclampsia, in utero fetal growth, or a spontaneous preterm delivery. A descriptive analyse was first conducted, secondly completed by a sub-group one: "high fetal fraction" (>90^th percentile) group, "low fetal-fraction" group (<10^th percentile) and "medium fetal-fraction" (control group) group.

RESULTS

A total of 417 women had a cfDNA test, which was performed at a mean gestational age of 17.1 weeks of gestation. A total of 17% of pregnancies met the primary criteria. Among them, there were 8 (1.9%) pre-eclampsia, 49 (11.8%) intra-uterine growth restriction and 14 (3.4%) preterm births. There was no significant difference for the occurrence of the primary criteria (P>0.99) and of each obstetrical complication between each group.

CONCLUSION

Fetal cf-DNA fraction measured at the beginning of the second trimester is not associated with common obstetrical complications.

Cell-Free Fetal DNA: A Novel Biomarker for Early Prediction of Pre-eclampsia and Other Obstetric Complications

Hypertensive disorder of pregnancy, especially Pre-eclampsia is one of the major causes of increased maternal and perinatal morbidity and mortality all over the world. Early prediction of pre-eclampsia is the need of modern obstetrics, as this can timely prevent the progress of disease as well as related fetal and maternal morbidity and mortality. In addition to the screening of fetal aneuploidies, Rhesus-D status, fetal sex, single gene disorders, the cell-free fetal Deoxyribonucleic acid (DNA) quantification has emerged as a promising biomarker for the prediction of pre-eclampsia. Hence, its use can help in the early prediction of hypertensive disorders of pregnancy, especially pre-eclampsia even before the appearance of symptoms. Furthermore, in future, it can also help in the determination of the complete DNA sequence of every gene of the fetus. The present review focuses on recent literature concerning the use of cell-free fetal DNA in early prediction of preeclampsia as well as for non-invasive prenatal genetic screening of fetus for various disorders. Methods: The recent literature related to cell-free fetal DNA was searched from numerous English language journals and published peer-reviewed articles on Pubmed, Google Scholar, MEDLINE and various government agencies till 2016.

Low fetal fraction of cell-free DNA predicts placental dysfunction and hypertensive disease in pregnancy

OBJECTIVE

To examine the association of low fetal fraction of cell-free DNA (cfDNA) with placental compromise and adverse perinatal outcomes.

MATERIALS AND METHODS

This was a retrospective cohort utilizing a sample of convenience including 639 women undergoing cfDNA screening at our institution from January 2013 to January 2017. Low fetal fraction was defined as less than the 25th percentile. Indicators of placental compromise were examined individually and as a composite outcome, including hypertensive disease of pregnancy, intrauterine growth restriction, abruption, and oligohydramnios. Neonatal outcomes, including preterm delivery, low Apgar scores, and small for gestational age, also were examined. We calculated risk ratios (RR) and 95% confidence intervals (CI).

RESULTS

Low fetal fraction was associated with placental compromise (RR 1.6 [CI 1.1-2.2]), hypertensive disease of pregnancy (RR 1.6 [CI 1.003-2.6]), and preeclampsia with severe features (RR 3.3 [CI 1.2-8.9]). Low fetal faction was not associated with preterm delivery, low Apgar scores, or small for gestational age.

CONCLUSIONS

Low fetal fraction of cfDNA among asymptomatic women may serve as a predictor of subsequent placental dysfunction and hypertensive disease.

Maternal Serum sEndoglin and Cell-Free Fetal DNA as Probable Markers of Preeclampsia: A Study in Single Center, Egypt

Background: This study was conducted to compare the levels of maternal serum soluble endoglin (sEng) and cell-free fetal DNA (cffDNA) in pregnant females with PE to normotensive pregnant ones, together with relating these levels to preeclampsia (PE) severity and onset. Method of the study: It was a comparative study in Mansoura University Hospital, Egypt, to detect the levels of serum sEng by ELISA besides the levels of cffDNA by quantitative real-time polymerase chain reaction in 80 pregnant females suffering from PE in addition to 80 normotensive pregnant ones that were included as control. Results: Levels of serum sEng and cffDNA were higher in PE cases than control (p < 0.0001٭ both) and were significantly related to the severity of the disease. Levels were also higher in early than late onset PE (p < 0.003٭ and <0.002٭, respectively). Sensitivities, specificities, positive, and negative predictive values in addition to accuracy of serum sEng and cffDNA were 97.5%, 98.8%, 98.7%, 97.5%, and 98.1% and 97.5%, 93.8%, 94.0%, 97.4%, and 95.6%, respectively. Conclusion: Maternal serum sEng and cffDNA can be good markers for diagnosis of PE in Egyptian patients. They are positively related to the disease severity. Abbreviations: cffDNA; Cell-Free Fetal DNA, sEng; soluble Endoglin, PE; preeclampsia, qRT PCR; Quantitative real-time polymerase chain reaction.

Alarmins at the maternal-fetal interface: involvement of inflammation in placental dysfunction and pregnancy complications 1

Inflammation is known to be associated with placental dysfunction and pregnancy complications. Infections are well known to be a cause of inflammation but they are frequently undetectable in pregnancy complications. More recently, the focus has been extended to inflammation of noninfectious origin, namely caused by endogenous mediators known as "damage-associated molecular patterns (DAMPs)" or alarmins. In this manuscript, we review the mechanism by which inflammation, sterile or infectious, can alter the placenta and its function. We discuss some classical DAMPs, such as uric acid, high mobility group box 1 (HMGB1), cell-free fetal deoxyribonucleic acid (DNA) (cffDNA), S100 proteins, heat shock protein 70 (HSP70), and adenosine triphosphate (ATP) and their impact on the placenta. We focus on the main placental cells (i.e., trophoblast and Hofbauer cells) and describe the placental response to, and release of, DAMPs. We also covered the current state of knowledge about the role of DAMPs in pregnancy complications including preeclampsia, fetal growth restriction, preterm birth, and stillbirth and possible therapeutic strategies to preserve placental function.

Maternal total cell-free DNA in preeclampsia and fetal growth restriction: Evidence of differences in maternal response to abnormal implantation

Objectives

Preeclampsia and fetal growth restriction are obstetrical syndromes associated with abnormal placental implantation and changes in the activation status of maternal leukocytes. This study is aimed to determine by a simple, rapid fluorescent assay the changes in maternal serum total cell-free DNA (t-cfDNA) concentrations in women with preeclampsia and those with fetal growth restriction (FGR).

Study design

A cross-sectional study was conducted measuring maternal serum t-cfDNA concentrations. Women were classified into the following groups: 1) patients with preeclampsia (n = 21); 2) FGR-estimated fetal weight below the 10^thpercentile (n = 28); and 3) normal pregnancy (n = 39). Serum samples were directly assayed for t-cfDNA using a rapid fluorescent SYBR Gold assay. Elevated maternal serum t-cfDNA concentrations were defined as a cutoff>850ng/ml. Nonparametric statistics were used for analysis.

Results

Women with preeclampsia had a higher median maternal serum concentration (802 ng/ml, 400–2272 ng/ml) than women with a normal pregnancy (499 ng/ml, 0–1892 ng/ml, p = 0.004) and those with FGR (484 ng/ml, 72–2187 ng/ml, p = 0.012). Moreover, even patients with FGR <5^th percentile and abnormal Doppler had a lower median maternal serum t-cfDNA than those with preeclampsia (median 487 ng/ml, 144–1971 ng/ml, p = 0.022). The median concentration of t-cfDNA did not differ between women with a normal pregnancy and those with FGR (p = 0.54), as well as those with fetuses <5th percentile and abnormal Doppler (p = 0.7). Women with preeclampsia had a higher proportion of elevated t-cfDNA than those with a normal pregnancy (p = 0.015) and patients with FGR (p = 0.025).

Conclusions

Preeclampsia is associated with higher maternal serum t-cfDNA concentration than normal pregnancy or FGR. This observation may reflect an increased systemic activation of the maternal inflammation, rather than placental; this assumption is supported by the fact that we did not observe a significant change in the maternal serum t-cfDNA in patients with placental-mediated FGR.

Maternal-fetal cross talk through cell-free fetal DNA, telomere shortening, microchimerism, and inflammation

There exists a strong correlation between unscheduled inflammation at the maternal-fetal interface and the continuum of pregnancy complications. In normal pregnancy, immunological tolerance is established to protect the semi-allogeneic fetus. There has been extensive research on how the immunity, endovascular trophoblast migration, and hormonal nexus are orchestrated during pregnancy at the maternal-fetal interface to program a normal pregnancy outcome. It is not clear what contributes to the plasticity of uterine immune tolerance, fetal survial, and long-term post-partum health of the mother and the offspring. Old and new concepts have reemerged and emerged that include cell-free fetal DNA (cffDNA), telomere shortening, microchimerism involving bidirectional migration of maternal and fetal cells, and pregnancy as a stress factor. The question is how these pathways converge in a gestational age-dependent manner to contribute to the health of the mother and the offspring later in life and respond to an array of inflammatory challenges. In this Review, we provide pertinent discussion on maternal-fetal cross talk through cffDNA, telomere shortening, and microchimerism in the context of inflammatory and anti-inflammatory settings, particularly how these pathways lead to normal and adverse pregnancy outcomes.

Cell-Free Total and Fetal DNA in First Trimester Maternal Serum and Subsequent Development of Preeclampsia

Objective The objective of this study was to assess the relationship between first trimester cell-free total and fetal DNA in maternal plasma and the subsequent development of preeclampsia. Study Design Nested case-control study of patients enrolled in the Combined Antioxidant and Preeclampsia Prediction Studies prediction study of 175 women who did and 175 women who did not develop preeclampsia. The predictive values of cell-free total and fetal DNA and the subsequent development of preeclampsia were measured using receiver operating characteristic curves. Results Cell-free total DNA was higher in African American (median; 25-75%; 6.15; 0.14-28.73; p = 0.02) and Hispanic (4.95; 0.20-26.82; p = 0.037) compared with white women (2.33; 0.03-13.10). Levels of cell-free total DNA were also associated with maternal body mass index (BMI) (p = 0.02). Cell-free total DNA levels were similar between women who later developed preeclampsia (3.52; 0.11-25.3) and controls (3.74; 0.12-21.14, p = 0.96). Conclusion There is no significant difference in levels of cell-free total DNA in the first trimester in women who subsequently develop preeclampsia. Levels of cell-free total DNA in the first trimester are increased in African American and Hispanic compared with white women, and levels increase with increasing BMI.

Sterile inflammation and pregnancy complications: a review

Inflammation is essential for successful embryo implantation, pregnancy maintenance and delivery. In the last decade, important advances have been made in regard to endogenous, and therefore non-infectious, initiators of inflammation, which can act through the same receptors as pathogens. These molecules are referred to as damage-associated molecular patterns (DAMPs), and their involvement in reproduction has only recently been unraveled. Even though inflammation is necessary for successful reproduction, untimely activation of inflammatory processes can have devastating effect on pregnancy outcomes. Many DAMPs, such as uric acid, high-mobility group box 1 (HMGB1), interleukin (IL)-1 and cell-free fetal DNA, have been associated with pregnancy complications, such as miscarriages, preeclampsia and preterm birth in preclinical models and in humans. However, the specific contribution of alarmins to these conditions is still under debate, as currently there is lack of information on their mechanism of action. In this review, we discuss the role of sterile inflammation in reproduction, including early implantation and pregnancy complications. Particularly, we focus on major alarmins vastly implicated in numerous sterile inflammatory processes, such as uric acid, HMGB1, IL-1α and cell-free DNA (especially that of fetal origin) while giving an overview of the potential role of other candidate alarmins.

A Dormant Microbial Component in the Development of Preeclampsia

Preeclampsia (PE) is a complex, multisystem disorder that remains a leading cause of morbidity and mortality in pregnancy. Four main classes of dysregulation accompany PE and are widely considered to contribute to its severity. These are abnormal trophoblast invasion of the placenta, anti-angiogenic responses, oxidative stress, and inflammation. What is lacking, however, is an explanation of how these themselves are caused. We here develop the unifying idea, and the considerable evidence for it, that the originating cause of PE (and of the four classes of dysregulation) is, in fact, microbial infection, that most such microbes are dormant and hence resist detection by conventional (replication-dependent) microbiology, and that by occasional resuscitation and growth it is they that are responsible for all the observable sequelae, including the continuing, chronic inflammation. In particular, bacterial products such as lipopolysaccharide (LPS), also known as endotoxin, are well known as highly inflammagenic and stimulate an innate (and possibly trained) immune response that exacerbates the inflammation further. The known need of microbes for free iron can explain the iron dysregulation that accompanies PE. We describe the main routes of infection (gut, oral, and urinary tract infection) and the regularly observed presence of microbes in placental and other tissues in PE. Every known proteomic biomarker of "preeclampsia" that we assessed has, in fact, also been shown to be raised in response to infection. An infectious component to PE fulfills the Bradford Hill criteria for ascribing a disease to an environmental cause and suggests a number of treatments, some of which have, in fact, been shown to be successful. PE was classically referred to as endotoxemia or toxemia of pregnancy, and it is ironic that it seems that LPS and other microbial endotoxins really are involved. Overall, the recognition of an infectious component in the etiology of PE mirrors that for ulcers and other diseases that were previously considered to lack one.

Unmethylated-maspin DNA in maternal plasma is associated with severe preeclampsia

INTRODUCTION

Cell-free fetal DNA in maternal plasma is associated with complications of pregnancy, including preeclampsia. Determination of levels is affected by fetal gender and genetic polymorphisms. Unmethylated maspin (u-maspin) is present in the placenta, and is placental-specific. The purpose of this study was to determine whether u-maspin DNA in maternal blood could serve as a marker of preeclampsia by measuring levels in different trimesters of normal pregnancies and in those complicated by preeclampsia.

MATERIAL AND METHODS

This case-control study was set in a tertiary care hospital. The population consisted of 45 women with normal pregnancies (15 in the 1st trimester, 15 in the 2nd trimester, 15 in the 3rd trimester), 20 women with mild preeclampsia, 25 women with severe preeclampsia, and six women with gestational trophoblastic disease. Peripheral blood was collected and methylation-specific PCR and fluorescence quantitative PCR were performed to measure the content of u-maspin DNA in maternal blood.

RESULTS

U-maspin DNA was 5.5-fold higher in women with severe preeclampsia than in those with a normal 3rd trimester pregnancy (p < 0.05). During normal pregnancy, u-maspin DNA in maternal plasma tended to increase with advancing gestational age (p = 0.06). U-maspin DNA was not detected in healthy non-pregnant women or those with gestational trophoblastic disease.

CONCLUSION

U-maspin DNA in maternal blood is associated with severe preeclampsia.

Fetal DNA in maternal plasma in preeclamptic pregnancies

Cell-free fetal DNA present in maternal circulation has revolutionized non-invasive prenatal diagnosis of genetic diseases. In preeclampsia, the quantity of fetal DNA in maternal plasma has been studied and found to be higher in comparison to healthy pregnant women. Whether the quantity of fetal DNA can be used as a reliable predictive biomarker of preeclampsia is currently uncertain. This is a systematic review on studies quantifying fetal DNA in preeclamptic pregnancies. Using a PubMed search 22 studies were identified. In all of them, elevated levels of fetal DNA in maternal plasma in preeclampsia were found. In some of the studies, the higher concentration of fetal DNA was observed before the onset of clinical symptoms. This shows that fetal DNA levels might have a potential informative value as an early diagnostic biomarker of preeclampsia. However, in most of the studies important data are missing and there is an enormous variability in the reported results between the studies. From the available data it is currently not possible to perform a meta-analysis due to the variation between studies. If once fetal DNA should be used as a marker for determining preeclampsia at early stage, it is necessary to reduce these variations via standardized protocols for the quantification of cell-free fetal DNA as well as its reporting in the publications.

Cell-free nucleic acids as non-invasive biomarkers of gynecological cancers, ovarian, endometrial and obstetric disorders and fetal aneuploidy

BACKGROUND

Proper folliculogenesis is fundamental to obtain a competent oocyte that, once fertilized, can support the acquisition of embryo developmental competence and pregnancy. MicroRNAs (miRNAs) are crucial regulators of folliculogenesis, which are expressed in the cumulus-oocyte complex and in granulosa cells and some can also be found in the bloodstream. These circulating miRNAs are intensively studied and used as diagnostic/prognostic markers of many diseases, including gynecological and pregnancy disorders. In addition, serum contains small amounts of cell-free DNA (cfDNA), presumably resulting from the release of genetic material from apoptotic/necrotic cells. The quantification of nucleic acids in serum samples could be used as a diagnostic tool for female infertility.

METHODS

An overview of the published literature on miRNAs, and particularly on the use of circulating miRNAs and cfDNA as non-invasive biomarkers of gynecological diseases, was performed (up to January 2014).

RESULTS

In the past decade, cell-free nucleic acids have been studied for potential use as biomarkers in many diseases, particularly in gynecological cancers, ovarian and endometrial disorders, as well as in pregnancy-related pathologies and fetal aneuploidy. The data strongly suggest that the concentration of cell-free nucleic acids in serum from IVF patients or in embryo culture medium could be related to the ovarian hormone status and embryo quality, respectively, and be used as a non-invasive biomarker of IVF outcome.

CONCLUSIONS

The profiling of circulating nucleic acids, such as miRNAs and cfDNA, opens new perspectives for the diagnosis/prognosis of ovarian disorders and for the prediction of IVF outcomes, namely (embryo quality and pregnancy).

Can the quantity of cell-free fetal DNA predict preeclampsia: a systematic review

OBJECTIVE

Previous studies have demonstrated an increase in the quantity of cell-free fetal DNA (cffDNA) before the onset of preeclampsia. It would be beneficial if the quantity of cffDNA predicted preeclampsia in order to implement preventative trials and strategies to decrease maternal and fetal morbidity. Our objective was to review the literature on using cffDNA levels as a predictor of preeclampsia.

METHODS

We performed a systematic review following the Meta-analyses and Systematic Review of Observational Studies guidelines. Included studies evaluated cffDNA levels in pregnant women before the clinical onset of preeclampsia.

RESULTS

Thirteen studies met inclusion criteria. There was considerable heterogeneity between included studies, and all received a quality grade of C on the Grading of Recommendations Assessment, Development, and Evaluation scale. Of the 13 studies, 11 found an increase in cffDNA among pregnant women who subsequently developed preeclampsia. In addition, all four studies analyzing early-onset or severe preeclampsia found significantly elevated cffDNA levels prior to disease onset.

CONCLUSION

Cell-free fetal DNA quantification is a promising marker for preeclampsia prediction, especially for the development of early-onset or severe preeclampsia. However, because of the heterogeneity in published studies, a precise conclusion about the statistical and clinical relevance cannot be made.

Role of circulating cell-free DNA levels in patients with severe preeclampsia and HELLP syndrome

BACKGROUND

Increased plasma levels of circulating cell-free DNA (c-f DNA) have been recently described in diseases related to ischemia and/or hypoxia. Preeclampsia (PCL) is a hypertensive disorder of pregnancy, of unknown origin, where a defective placentation resulting in placental ischemia plays an important role. HELLP syndrome (haemolysis, elevated liver enzymes, and low platelet count) is the most serious form of PCL. The origin of the disease is unknown, and there are no markers to help us to make an early diagnosis of disease or to predict patients who are at risk of suffering serious complications.

METHODS

We measured circulating c-f DNA levels in a group of control pregnant women (n = 20), patients with mild PCL (n = 9), patients with severe PCL (n = 24), and patients with HELLP syndrome (n = 8).

RESULTS

Values of circulating c-f DNA were 333.59 ± 64.3 ng/ml in control subjects; 635.11 ± 111.7 ng/ml in patients with mild PCL; 1,264.63 ± 127.1 ng/ml in patients with severe PCL, and 1,595.95 ± 269.8 ng/ml in patients with HELPP syndrome. (P < 0.0001). Values of c-f DNA >950 ng/ml had a sensitivity and specificity for detecting severe PCL and/or HELLLP syndrome of 0.71 and 0.93, respectively.

CONCLUSIONS

As far as we know, this is the first report of increased c-f DNA levels in HELLP syndrome. In this preliminary report, we have observed a gradual and strong relation between c-f DNA levels and range of severity of PCL, with it the highest in patients with HELLP syndrome. Further studies are needed for evaluating the utility of this technique in hypertensive disorders of pregnancy and, particularly, in HELLP syndrome.

Comparison of four DNA extraction methods for detecting Mycobacterium tuberculosis by real-time PCR and its clinical application in pulmonary tuberculosis

OBJECTIVES

China is one of the countries with a high burden of Mycobacterium tuberculosis (MTB) infection. One challenge for the earlier diagnosis of tuberculosis is the DNA extraction of MTB. This study was to compare four MTB DNA extraction methods, and use the best one in the diagnosis of pulmonary tuberculosis.

METHODS

A total of 43 serum and 94 plasma samples were collected from 124 clinical diagnosed pulmonary tuberculosis patients. Four different MTB DNA extraction methods, including phenol-chloroform method, Qiagen kit, Omega kit and magnetic bead method, were compared to determine which method displayed the highest sensitivity. A quantitative fluorescent PCR assay was also designed for the detection of MTB DNA.

RESULTS

The highest DNA extraction efficiency (52.8%) and the best reproducibility (coefficient of variance =26.7%) were observed using the magnetic bead method. For 39 of the 124 (31.5%) pulmonary tuberculosis patients, MTB DNA was detected in their plasma or serum samples. Interestingly, 35.3% (12/34) of smear-negative cases were MTB DNA positive.

CONCLUSIONS

In conclusion, magnetic bead method is the best one for the DNA extraction of MTB. The detection of MTB DNA may provide valuable information for the diagnosis of acid-fast bacilli (AFB) negative pulmonary tuberculosis patients.

Quantification of maternal serum cell-free fetal DNA in early-onset preeclampsia

The aim of this study was to determine whether the increased serum cell-free fetal DNA (cffDNA) level of gravidas developed into early-onset preeclampsia (EOPE) subsequently in the early second trimesters is related to prenatal screening markers. Serum was collected from 1011 gravidas. The level of cffDNA and prenatal screening markers were analyzed in 20 cases with EOPE and 20 controls. All fetuses were male. The maternal serum cffDNA level was assessed by amplification of the Y chromosome specific gene. Correlations between the variables were examined. (Logged) cffDNA in EOPE (median, 3.08; interquartile range, 2.93-3.68) was higher than controls (median, 1.79; interquartile range, 1.46-2.53). The increased level of (logged) cffDNA was correlated significantly with the increased human chorionic gonadotropin (HCG) level (r = 0.628, p < 0.001). Significant reciprocal correlations between cffDNA and babies' birth weight as well as gestation weeks at delivery were noted (r = -0.516, p = 0.001; r = -0.623, p < 0.001, respectively). The sensitivity and specificity of cffDNA to discriminate between the EOPE cases and the controls were 90% and 85%, respectively. CffDNA is a potential marker for EOPE, which had a significant reciprocal correlation with babies' birth weight and gestation weeks at delivery. Moreover, it may help in indicating the underlying hypoxic condition in the placenta.

RASSF1A in maternal plasma as a molecular marker of preeclampsia

OBJECTIVES

This study aimed to quantitate cell free (cf) and cell free fetal (cff) DNA in maternal plasma by determining RASSF1A levels before and after enzyme digestion in women who subsequently developed preeclampsia (PE) and compare them with uncomplicated pregnancies.

METHODS

Twenty-four samples from pregnant women who developed PE and 48 samples from women with uncomplicated pregnancies were analysed. Blood samples were obtained at 11-13 weeks. cfDNA was determined by quantifying RASSF1A using qRT-PCR. A second qRT-PCR was performed following methylation-sensitive enzyme digestion by BstUI, to quantitate hypermethylated RASSF1A sequences of fetal origin. ACTB gene was used as control to confirm complete enzyme digestion.

RESULTS

cfDNA and cffDNA levels were significantly increased in women who developed PE as compared with uncomplicated pregnancies (median cfDNA: 9402 vs 2698, median cffDNA: 934.5 vs 62, respectively). Following operating characteristic curve analysis, cut-off values of 7486 Εq/mL for cfDNA and 512 Εq/mL for cffDNA were chosen, which provided a sensitivity of 75% and 100% and specificity of 98% and 100%, respectively, to identify women at risk for PE.

CONCLUSIONS

The study demonstrates potential use of cfDNA and cffDNA in maternal plasma as markers for the early prediction of women at risk for PE.

Clinical evaluations of cell-free fetal DNA quantities in pre-eclamptic pregnancies

AIM

Quantitative changes of cell-free fetal DNA in maternal plasma as an indicator for impending pre-eclampsia was reported in different studies. Cell-free fetal nucleic acids can be detected in maternal circulation during pregnancy. Our aim was to determine the higher rate of fetal DNA levels in maternal blood in pre-eclampsia compared to normal pregnancies and the clinical use of real-time polymerase chain reaction (PCR) in the Turkish population as a marker.

MATERIAL AND METHODS

According to their gestational ages, the plasma levels of 30 pre-eclamptic women at 26-40 weeks of pregnancy were matched with 18 healthy pregnant women. Cell-free fetal DNA levels in maternal plasma were compared using real-time PCR technology. For the quantitative measurement of fetal DNA from maternal blood, the relative quantification PCR process was applied to all samples, using SRY and GAPDH genes. These patients were classified as pre-eclamptic and control groups and were matched according to weeks of pregnancy.

RESULTS

Free fetal DNA levels of 30 pre-eclamptic patients were compared to healthy pregnant women and an average 3.06-fold increase was observed. During the second trimester, free fetal DNA levels were 1.5 times higher in pre-eclamptic patients. This increase was 3.5-fold during the third trimester. The DNA increase of pre-eclamptic patients was 4.1-fold and 3.4-fold during 29th-33rd and 34th-40th weeks, respectively.

CONCLUSIONS

Cell-free fetal DNA in maternal blood could be used as a marker for identifying subjects at increased risk of developing pre-eclampsia.

Cell-free fetal DNA and adverse outcome in low risk pregnancies

OBJECTIVE

To analyze in a large prospective cohort study of low risk pregnancies whether cell-free fetal (cff) DNA in maternal plasma of the second trimester might be associated with the development of preeclampsia, preterm delivery, and small for gestational age.

STUDY DESIGN

A subset of a large prospective cohort study in serological RhD negative pregnant women with RHD positive fetuses was used. Cff DNA was determined through the detection of RHD specific sequences with real-time PCR.

RESULTS

In 611 pregnancies, rates of 7.2% preeclampsia, 1.6% preterm birth ≤32, 2.9% ≤34, and 12.4% ≤37 weeks of gestation, 5.7% of small for gestational age <5th percentile, and 8.2% <10th percentile were observed. For none of these risk groups an association with cff DNA could be established.

CONCLUSION

Cff DNA in maternal plasma of the second trimester was not found to be a marker for an adverse pregnancy outcome in low risk pregnancies.

Mass spectrometric based analysis, characterization and applications of circulating cell free DNA isolated from human body fluids

In the past decade, cell free DNA, or circulating cell free DNA, or cell free circulating DNA, isolated from body fluids such as plasma/serum/urine has emerged as an important tool for clinical diagnostics. The molecular biology of circulating cell free DNA is poorly understood but there is currently an increased effort to understand the origin, mechanism of its circulation, and sensitive characterization for the development of diagnostic applications. There has been considerable progress towards these goals using real time polymerase chain reaction technique (rt-PCR). More recently, new attempts to incorporate mass spectrometric techniques to develop accurate and highly sensitive high-throughput clinical diagnostic tests have been reported. This review focuses on the methods to isolate circulating cell free DNA from body fluids, their quantitative analysis and mass spectrometry based characterization in evolving applications as prenatal and cancer diagnostic tools.

Circulating cytokines, chemokines and adhesion molecules in normal pregnancy and preeclampsia determined by multiplex suspension array

BACKGROUND

Preeclampsia is a severe complication of pregnancy characterized by an excessive maternal systemic inflammatory response with activation of both the innate and adaptive arms of the immune system. Cytokines, chemokines and adhesion molecules are central to innate and adaptive immune processes. The purpose of this study was to determine circulating levels of cytokines, chemokines and adhesion molecules in normal pregnancy and preeclampsia in a comprehensive manner, and to investigate their relationship to the clinical features and laboratory parameters of the study participants, including markers of overall inflammation (C-reactive protein), endothelial activation (von Willebrand factor antigen) and endothelial injury (fibronectin), oxidative stress (malondialdehyde) and trophoblast debris (cell-free fetal DNA).

RESULTS

Serum levels of interleukin (IL)-1beta, IL-1 receptor antagonist (IL-1ra), IL-2, IL-4, IL-6, IL-8, IL-10, IL-12p40, IL-12p70, IL-18, interferon (IFN)-gamma, tumor necrosis factor (TNF)-alpha, transforming growth factor (TGF)-beta1, interferon-gamma-inducible protein (IP)-10, monocyte chemotactic protein (MCP)-1, intercellular adhesion molecule (ICAM)-1 and vascular cell adhesion molecule (VCAM)-1 were measured in 60 preeclamptic patients, 60 healthy pregnant women and 59 healthy non-pregnant women by multiplex suspension array and ELISA. In normal pregnancy, the relative abundance of circulating IL-18 over IL-12p70 and the relative deficiency of the bioactive IL-12p70 in relation to IL-12p40 might favour Th2-type immunity. Although decreased IL-1ra, TNF-alpha and MCP-1 concentrations of healthy pregnant relative to non-pregnant women reflect anti-inflammatory changes in circulating cytokine profile, their decreased serum IL-10 and increased IP-10 levels might drive pro-inflammatory responses. In addition to a shift towards Th1-type immunity (expressed by the increased IL-2/IL-4 and IFN-gamma/IL-4 ratios), circulating levels of the pro-inflammatory cytokines IL-6 and TNF-alpha, the chemokines IL-8, IP-10 and MCP-1, as well as the adhesion molecules ICAM-1 and VCAM-1, were raised in preeclampsia compared with healthy pregnancy, resulting in an overall pro-inflammatory systemic environment. Increased IP-10, MCP-1, ICAM-1 and VCAM-1 concentrations of preeclamptic patients showed significant correlations with blood pressure values, renal and liver function parameters, as well as with CRP, malondialdehyde, von Willebrand factor antigen and fibronectin levels.

CONCLUSIONS

According to our findings, preeclampsia was associated with an overall pro-inflammatory systemic environment. Elevated amounts of pro-inflammatory cytokines, chemokines and adhesion molecules in the maternal circulation might play a central role in the excessive systemic inflammatory response, as well as in the generalized endothelial dysfunction characteristics of the maternal syndrome of preeclampsia.