Antiphospholipid and Anti‐DNA Antibodies Are Not Associated with the Elevated Release of Circulatory Fetal DNA in Pregnancies Affected by Preeclampsia

Circulating Nucleic Acids in Maternal Plasma and Serum in Pregnancy Complications: Are They Really Useful in Clinical Practice? A Systematic Review

OBJECTIVE

A systematic review was carried out to summarize the available evidence to assess whether circulating nucleic acids in maternal plasma and serum (CNAPS) have the potential to serve as extra and independent markers for the prediction and/or progression monitoring of the most common and severe complications of pregnancy, including preeclampsia, intrauterine growth restriction, preterm delivery, morbidly adherent placenta, gestational diabetes, antiphospholipid syndrome, threatened abortion, intrahepatic cholestasis of pregnancy, and hyperemesis gravidarum.

METHOD

A comprehensive literature search of the MEDLINE (PubMed), EMBASE, and ISI Web of Knowledge databases was conducted to identify relevant studies that included amounts of CNAPS in the abovementioned pregnancy complications.

RESULTS

Eighty-three studies met the eligibility criteria. The vast majority of studies were conducted on the quantity of total circulating cell free DNA (cfDNA) and cell free fetal DNA (cffDNA), and some were conducted on messenger RNA (mRNA) species. A few studies have instead evaluated the cell free DNA fetal fraction (cfDNAff), but only in a limited number of pregnancy complications. Despite the growing interest and the abundance of the papers available, little information is available for other new CNAPS, including microRNA (miRNA), long noncoding RNA (lncRNA), mitochondrial DNA (mtDNA), and circular RNA.

CONCLUSION

Due to the heterogeneity of the populations enrolled, the scarcity of the studies that adjusted the CNAPS values for possible confounding factors, and the difficulty in interpreting the published data, no conclusion regarding the statistical robustness and clinical relevance of the data can be made at present. If assayed at the third trimester, the CNAPS have, however, shown better performance, and could be used in populations already at risk of developing complications as suggested by the presence of other clinical features. Other CNAPS, including miRNA, are under investigation, especially for the screening of gestational diabetes mellitus, but no data about their clinical utility are available. Circulating DNA (cfDNA, cffDNA, and cfDNAff) and mRNA have not been properly evaluated yet, especially in patients asymptomatic early in pregnancy but who developed complications later, perhaps because of the high cost of these techniques and the availability of other predictors of pregnancy complications (biochemical, biophysical, and ultrasound markers). Therefore, from the analysis of the data, the positive predictive value is not available. As regards the new CNAPS, including miRNA, there are still no sufficient data to understand if they can be promising markers for pregnancy complications monitoring and screening, since CNAPS are statistically weak and expensive. It is reasonable to currently conclude that the use of the CNAPS in clinical practice is not recommended.

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.

Quantification of circulating fetal DNA as a tool for potential monitoring of pregnant patients with antiphospholipid antibodies

Apoptosis of tissues of fetal origin is thought to be one of the main sources of cell-free fetal DNA (cffDNA) in maternal circulation, impaired apoptosis is also involved in the mechanisms contributing to recurrent spontaneous miscarriages (RSM) associated with antiphospholipid syndrome (APS). The APS increases the risk for preeclampsia nine times. In preeclampsia, the elevated levels of cffDNA were described by different authors. To our knowledge, cffDNA in pregnant patients with APS was never studied. In our pilot study, we focused on the levels of cffDNA in four pregnant patients with treated primary APS and compared them with values obtained in twenty-one healthy subjects of comparable gestation age (the third trimester of pregnancy). We supposed that the increase of cffDNA concentration in our treated patients would signalize the elevated apoptosis of fetal tissues as in other pathological changes of placentation. The aim of our pilot study was to determine cffDNA concentrations in patients with treated APS and to compare them with values detected in healthy pregnant women of comparable gestation age in order to discover potential non-physiological elevations in patients. The elevated values of cffDNA were not observed in our patients (p value = 0.4363, Mann-Whitney test). All patients delivered healthy children. The measurement of concentrations of cffDNA seems to be a promising tool for monitoring of therapy effectiveness in pregnant women with APS but evaluation of randomized controlled trials would be necessary to determine the specificity and the sensitivity of this test.

Disturbances in placental immunology: ready for therapeutic interventions?

Recent studies have provided new insight into aberrations in the immunological interplay between mother and fetus and their potential role in the development of recurrent fetal loss and preeclampsia. The action of anti-phospholipid antibodies in recurrent fetal loss is now proposed to involve the complement system, neutrophil activation and the production of TNFalpha by immune bystander cells. A clear involvement of the immune system is emerging in preeclampsia, involving mainly the innate arm, especially neutrophils. The activation of peripheral neutrophils by placentally released inflammatory debris triggers the induction of neutrophil extracellular traps (NETs), which may lead to an occlusion of the intervillous space, thereby further promoting a condition of placental hypoxia. It has, hence, been suggested that new therapeutic strategies be developed, including the possible use of TNFalpha antagonists in cases of recurrent miscarriage. These strategies need to be addressed with caution due to the possible induction of fetal congenital abnormalities.

Fourth International Workshop on immunology of pre-eclampsia, December 2004, Reunion, France

The Fourth International Workshop on 'Reproductive Immunology, Immunological Tolerance and Immunology of Pre-eclampsia' was held in the Island of La Reunion in December 2004. Besides intense sharing of immunological data, it included also epidemiological studies from South Africa, USA and Australia, as well as genetic studies from South Africa and Mauritius, discussions on the future of graft transplant tolerance, implications of inositol-phosphoglycans in the pathogenesis of pre-eclampsia (PE), pathways to the inflammatory syndrome and other topics. Participants shared the belief that we may be witnessing significant steps forward in our comprehension of PE as an immunological event, with a prominent role for deregulation of the innate immune system, probably controlled by T cells and cytokine networks at the feto-placental interface. There was a growing consensus for an NK cell (KIR)-dependent event, with regulation exerted by T cells, as well as an important role for HLA-C presentation/recognition and HLA-G in mediating inflammatory cytokine imbalance, with an emphasis on IL-12 and IL-16 It is hoped that the next Workshop in 2006 will prove the immune involvement by dissecting the NK/Treg/Ts cell and HLA-CI HLA-G circuits leading to cytokine and vascular dysfunction.

Macrophage migration inhibition factor is elevated in pregnancy, but not to a greater extent in preeclampsia

BACKGROUND

Maternal serum concentrations of macrophage migration inhibitory factor (MIF) have recently been reported to be elevated in cases with preeclampsia. These findings may be important in increasing our understanding of the underlying events leading to the development of preeclampsia, as this cytokine is also expressed in the placenta, where it has been shown to possess immunemodulatory activities. For this reason we attempted to independently verify this report.

METHODS

Plasma levels of MIF were assessed by ELISA in plasma samples collected from normal healthy male and female blood donors (n=20 per group), as well as healthy normal pregnant women in all three trimesters of pregnancy (n=60). In addition, MIF levels were examined from cases with mild and severe preeclampsia (n=20 per study cohort) and matched normotensive pregnancies (n=20).

RESULTS

MIF levels were found to be elevated in pregnancy (median=10.1 ng/ml) when compared to non-pregnant controls (median=1.7 ng/ml). A moderate, but not significant, elevation was found to occur from the first to the third trimester of pregnancy. No significant difference was found to occur between the two preeclampsia study groups when compared to the normotensive control group.

CONCLUSIONS

Our data suggest that circulatory MIF concentrations are elevated throughout pregnancy, but are not further increased in preeclampsia.