Maternal plasma RNA sequencing

Circulating Non-coding RNAs and Exosomes: Liquid Biopsies for Monitoring Preeclampsia

Preeclampsia (PE) remains a leading cause of maternal and fetal mortality, due to ineffective treatment and diagnostic strategies, compounded by the lack of clarity on the etiology of the disorder. The early prediction or accurate diagnosis of PE is a concern of researchers. Liquid biopsy can be analyzed for cell-free nucleic acids and exosomes. Because circulating non-coding RNAs (ncRNAs) and peripheral blood exosomes can be detected in the peripheral blood of women in early pregnancy, these vesicles and their contents have become the focus of research on early predictive and diagnostic biomarkers for preeclampsia. In this review, we focus on recent studies addressing the roles of circulating ncRNAs and exosomes in PE, with particular attention paid to the potential application value of placenta-derived exosomes and circulating ncRNAs as PE-specific biomarkers.

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.

Maternal Plasma DNA and RNA Sequencing for Prenatal Testing

Cell-free DNA (cfDNA) testing has recently become indispensable in diagnostic testing and screening. In the prenatal setting, this type of testing is often called noninvasive prenatal testing (NIPT). With a number of techniques, using either next-generation sequencing or single nucleotide polymorphism-based approaches, fetal cfDNA in maternal plasma can be analyzed to screen for rhesus D genotype, common chromosomal aneuploidies, and increasingly for testing other conditions, including monogenic disorders. With regard to screening for common aneuploidies, challenges arise when implementing NIPT in current prenatal settings. Depending on the method used (targeted or nontargeted), chromosomal anomalies other than trisomy 21, 18, or 13 can be detected, either of fetal or maternal origin, also referred to as unsolicited or incidental findings. For various biological reasons, there is a small chance of having either a false-positive or false-negative NIPT result, or no result, also referred to as a "no-call." Both pre- and posttest counseling for NIPT should include discussing potential discrepancies. Since NIPT remains a screening test, a positive NIPT result should be confirmed by invasive diagnostic testing (either by chorionic villus biopsy or by amniocentesis). As the scope of NIPT is widening, professional guidelines need to discuss the ethics of what to offer and how to offer. In this review, we discuss the current biochemical, clinical, and ethical challenges of cfDNA testing in the prenatal setting and its future perspectives including novel applications that target RNA instead of DNA.

Gene expression profiling of pre-eclamptic placentae by RNA sequencing

Pre-eclampsia is a common and complex pregnancy disorder that often involves impaired placental development. In order to identify altered gene expression in pre-eclamptic placenta, we sequenced placental transcriptomes of nine pre-eclamptic and nine healthy pregnant women in pools of three. The differential gene expression was tested both by including all the pools in the analysis and by excluding some of the pools based on phenotypic characteristics. From these analyses, we identified altogether 53 differently expressed genes, a subset of which was validated by qPCR in 20 cases and 19 controls. Furthermore, we conducted pathway and functional analyses which revealed disturbed vascular function and immunological balance in pre-eclamptic placenta. Some of the genes identified in our study have been reported by numerous microarray studies (BHLHE40, FSTL3, HK2, HTRA4, LEP, PVRL4, SASH1, SIGLEC6), but many have been implicated in only few studies or have not previously been linked to pre-eclampsia (ARMS2, BTNL9, CCSAP, DIO2, FER1L4, HPSE, LOC100129345, LYN, MYO7B, NCMAP, NDRG1, NRIP1, PLIN2, SBSPON, SERPINB9, SH3BP5, TET3, TPBG, ZNF175). Several of the molecules produced by these genes may have a role in the pathogenesis of pre-eclampsia, and some could qualify as biomarkers for prediction or detection of this pregnancy complication.