Lower Maternal PLAC1 mRNA in Pregnancies Complicated with Vaginal Bleeding (Threatened Abortion <20 Weeks) and a Surviving Fetus

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.

Placenta specific protein-1 in recurrent pregnancy loss and in In Vitro Fertilisation failure: a prospective observational case-control study

Observations from studies have provided evidence that Placenta-specific protein1 (PLAC1) is important for the establishment and maintenance of pregnancy and suggest it as a potential biomarker for gestational pathologies. The aim of this study is to investigate whether maternal serum PLAC1 levels have any impact on etiopathogenesis of recurrent pregnancy loss (RPL) and repeated implantation failure after In Vitro Fertilisation (RIF). We conducted a prospective observational case-control study in a Research Hospital. Twenty-eight patients with RPL (group 1), 30 patients with unexplained infertility and RIF (group 2), 29 fertile patients (group 3) were included. The demographic features and serum PLAC1 levels were compared. There was a significant difference in PLAC1 levels between the groups (group 1 = 19.71 + 16.55 ng/ml; group 2 = 4.82 + 1.44 ng/ml; group 3 = 0.89 + 0.62 ng/ml, respectively) (p=.001). Positive correlation was found between serum PLAC1 levels and abortion rates (r = 0.64; p=.001), a negative correlation was found between serum PLAC1 levels and live birth rates (r = -0.69; p=.001). PLAC1 might have a negative effect on implantation in RPL and RIF. There may be a subgroup of PLAC with different bioactivity. There are no relevant studies conducted among these populations, further large-scale studies are needed to assess the molecular role of PLAC1 on implantation.IMPACT STATEMENTWhat is already known about this subject? PLAC1 (placenta-specific protein-1) gene is located on the X chromosome which encodes for a protein that is thought to be important for placental development although its role has not been clearly defined. Studies in the literature have provided evidence that PLAC1 has an important role in the establishment and maintenance of pregnancy and suggest it as a potential biomarker for gestational pathologies. Several reports over the past few years have demonstrated PLAC1 expression in a variety of human tumours including lung cancers, breast cancer, hepatocellular and colorectal cancers, gastric cancers and uterine cancers.What do the results of this study add? There have been no previous studies conducted among patients with recurrent pregnancy loss (RPL) or repeated implantation failure after In Vitro Fertilisation (RIF) that have searched for any association between PLAC1 levels and implantation failure. This study has demonstrated higher PLAC1 levels in infertile women with RIF and RPL for the first time; suggesting that it could have a negative effect on implantation in these populations. PLAC1 could be detected in the serum as a biomarker that is associated with RIF and RPL. What are the implications of these findings for clinical practice and/or further research? Defining the precise role of PLAC1 during implantation will provide new insight into understanding of poor reproductive outcomes such as RIF and RPL and help in developing treatment strategies. Further large-scale studies with more patients are needed to uncover the clinical value of PLAC1 as a biomarker to predict repeated implantation failure and RPL.

PLAC1 immunization does not induce infertility in mice

Aim: Placenta specific 1 (PLAC1) is a protein rarely expressed in normal cells, except it is important for placental development, with a possible role in the establishment of the mother–fetus interface. The gene is also highly active in a wide variety of cancers and therefore, immunization with PLAC1 peptides could possibly be part of future immunotherapeutic strategies. We investigated whether vaccination against PLAC1 could induce infertility. Materials & methods: We inoculated female mice with PLAC1 peptides, put them in mating, measured antibody response (ELISA assay) and checked, in immunohistochemistry, binding of the induced antibodies to the native antigen. Results: We demonstrated that mice consistently develop antibody responses. We also demonstrated that female mice, after being inoculated with the PLAC1 peptide mix, do became pregnant and can give birth to normal infants. Conclusion: PLAC1 antigens as a specific anti-cancer vaccine could induce anti-PLAC1 antibodies which do not necessarily cause infertility.

The placental specific gene, PLAC1, is induced by the Epstein-Barr virus and is expressed in human tumor cells

BACKGROUND

The Epstein-Barr virus (EBV) is a causal agent in a number of malignancies in humans including hematopoietic tumors and non-hematopoietic tumors. Burkitt's lymphoma cell lines containing the Epstein-Barr virus have been shown to form tumors in nude mice while clonal derivatives of such cell lines in which the viral genome has been lost do not (JID 177: 1194-1201, 1998; JV 72: 9150-9156, 1998; JV 68: 6069-6073, 1994). The re-introduction of EBV into these EBV negative BLs reconstitutes the tumor phenotype. Thus, EBV-induced cellular genes play critical role in EBV-related tumors.

METHODS AND RESULTS

In an attempt to identify cellular genes regulated by EBV that may contribute to its tumorigenic properties, we have enforced genome loss in the Burkitt's lymphoma (BL) line, MutuI, by introducing a dominant negative form of the episomal replication factor, EBNA1 and carried out gene array analysis. One of the genes identified by this analysis is PLAC1, a gene originally identified as being expressed exclusively in placental tissue. Real time RT-PCR analysis verified higher expression in EBV positive vs. EBV negative Mutu clones. Analysis of a panel of RNAs from 20 normal tissues demonstrated the highest level of expression in placenta but significant expression was also observed in testis and brain cerebellum. PLAC1 expression was also observed in non-BL tumor cell lines derived from breast, ovary, and prostate. Lastly, expression of PLAC1 was found to be higher in some primary breast tumors compared to normal adjacent tissues.

CONCLUSION

This data suggests that the EBV-induced PLAC1 is a member of the cancer/testis group of tumor antigens.

The Role of RNAs and microRNAs in Non-Invasive Prenatal Diagnosis

In this paper, all possible clinical applications of circulating mRNA and miRNA for non-invasive prenatal diagnosis appearing in the medical literature so far are described. Data from the literature have also been reported and commented on along with some possible future applications.

The nexus of prematurity, birth defects, and intrauterine growth restriction: a role for plac1-regulated pathways

Epidemiological studies have demonstrated an increased prevalence of birth defects and intrauterine growth restriction (IUGR) among infants born prematurely suggesting they share common biological determinants. The identification of key regulatory pathways contributing to this nexus is essential to ongoing efforts to develop effective intervention strategies. Plac1 is a paternally imprinted and X-linked gene that conforms to this paradigm. Examination of a mutant mouse model has confirmed that Plac1 is essential for normal placental development and function. Moreover, it is expressed throughout the developing embryo indicating that it also has broad relevance to embryogenesis. Most notably, its absence in the developing embryo is associated with abnormal brain development and an increased risk of lethal, postnatal hydrocephalus identifying it as a novel, X-linked determinant of brain development. The essential and non-redundant roles of Plac1 in placental and neurological development represent a novel regulatory paradigm for embryonic growth and pregnancy maintenance. Regulatory pathways influenced, in part, by Plac1 are likely to contribute to the observed nexus of IUGR, prematurity, and birth defects.

PLAC1 Expression Decreases in Chorionic Villi in Response to Labor

PLAC1 (Placenta-Specific 1) is a recently described, trophoblast-expressed gene essential for normal placental development. The protein localizes to the microvillus membrane surface of the syncytiotrophoblast in direct proximity to the maternal compartment. Although its role has not been defined, increased circulating levels of human PLAC1 mRNA in maternal blood are associated with preeclampsia. Furthermore, PLAC1-null mice exhibit decreased viability in the peripartum period suggesting a role in pregnancy maintenance late in gestation. We examined PLAC1 gene expression in the human placenta during normal pregnancy and pregnancies associated with maternal diabetes and preeclampsia using quantitative, real time PCR (q-RT-PCR). Although there was no apparent difference in PLAC1 gene expression among human pregnancies complicated by diabetes or preeclampsia, an unexpected effect of labor was noted at term. PLAC1 expression in placentae delivered vaginally following induced or spontaneous labor was significantly reduced compared to placentae not exposed to labor making it one of only a few placental genes influenced by labor. The significance of this finding is unknown. Viewed in the context of its importance in placental development, however, these findings are consistent with a role for PLAC1 in the maintenance of the maternal-fetal interface.

Circulating Anti-PLAC1 Antibodies during Pregnancy and in Women with Reproductive Failure: A Preliminary Analysis

The aims of this study were to determine the prevalence of anti-PLAC1 antibodies in normal pregnant women and in women with infertility or recurrent pregnancy loss (RPL). Secondary outcomes were the development of complications associated with anti-PLAC1 seropositivity and the rate of seroconversion during pregnancy. Sera from 103 healthy pregnant women and 45 women with unexplained infertility or RPL were analyzed by ELISA. The prevalence of anti-PLAC1 antibodies was 2% in healthy pregnant women and 4.5% in women with unexplained infertility or RPL (P=0.355). There was no detectable association of seropositivity with increased risk of pregnancy complications. Finally, 2% of women seroconverted during pregnancy. The prevalence of anti-PLAC1 antibodies in women with unexplained infertility or RPL is not significantly higher than the prevalence in normal pregnant women. However, the sample size in this study was too small. The exposure to the PLAC1 antigen during pregnancy can lead to the spontaneous development of antibodies.

PLAC1 (Placenta-specific 1): a novel, X-linked gene with roles in reproductive and cancer biology

Placenta-specific 1 (PLAC1) is a recently described X-linked gene with expression restricted primarily to cells derived from trophoblast lineage during embryonic development. PLAC1 localizes to a region of the X chromosome thought to be important in placental development although its role in this process has not been defined. This review summarizes our current understanding of its expression, regulation, and function. PLAC1 is expressed throughout human pregnancy by the differentiated trophoblast and localizes to membranous structures in the syncytiotrophoblast, including the microvillous plasma membrane surface. Recent studies have demonstrated that PLAC1 is also expressed by a wide variety of human cancers. Studies of the PLAC1 promoter regions indicate that its expression in both normal placenta and cancer cells is driven by specific interactions involving a combination of transcription factors. Although functional insight into PLAC1 in the normal trophoblast is lacking, preliminary studies suggest that cancer-derived PLAC1 has the potential to promote tumor growth and function. In addition, it also appears to elicit a specific immunologic response that may influence survival in some cancer patients, suggesting that it may provide a therapeutic target for the treatment of some cancers. We also discuss a potential role for PLAC1 as a biomarker predictive of specific pregnancy complications, such as preeclampsia.

Placenta-derived fetal specific mRNA is more readily detectable in maternal plasma than in whole blood

BACKGROUND

Placental mRNA was detected in maternal whole blood, raising the possibility of using maternal blood for noninvasive prenatal diagnosis. We investigated fetal mRNA detection in maternal whole blood and determined if it offered advantages over maternal plasma analysis.

METHODOLOGY

The concentrations of placental expressed genes, CSH1, KISS1, PLAC4 and PLAC1 in plasma and whole blood from healthy pregnant and non-pregnant individuals were compared by real-time quantitative reverse-transcriptase polymerase chain reaction analysis. Their fetal specificity was investigated by comparing the transcript concentrations in pre- and post-delivery samples and through SNP genotyping by matrix-assisted laser-desorption and ionization time-of-flight mass spectrometry. The gene expression profiles of pregnant and non-pregnant whole blood were investigated by microarray analysis. Upregulated genes in pregnant whole blood were selected for further quantitative analysis.

PRINCIPAL FINDINGS

The concentrations of the four transcripts were significantly higher in third trimester maternal whole blood than corresponding plasma without significant correlations. KISS1, PLAC4 and PLAC1 were detected in non-pregnant whole blood but not plasma. The transcripts remained detectable in some postpartum whole blood samples. The PLAC4 mRNA in maternal plasma showed fetal genotype while that in corresponding whole blood indicated both fetal and maternal contributions. Microarray analysis revealed upregulation of genes involved in neutrophil functions in pregnant whole blood including DEFA4, CEACAM8, OLFM4, ORM1, MMP8 and MPO. Though possibly pregnancy-related, they were not pregnancy-specific as suggested by the lack of post-delivery reduction in concentrations.

CONCLUSIONS

Maternal plasma is preferred over maternal whole blood for placenta-derived fetal RNA detection. Most studied 'placental' mRNA molecules in maternal whole blood were of maternal origin and might be derived from processes such as 'illegitimate transcription'.

Plac1 is a tumor-specific antigen capable of eliciting spontaneous antibody responses in human cancer patients

Immunoselection and tumor evasion constitutes one of the major obstacles in cancer immunotherapy. A potential solution to this problem is the development of polyvalent vaccines, and the identification of more tumor-specific antigens is a prerequisite for the development of cancer vaccines. To identify novel tumor-specific antigens, suppression subtractive hybridization (SSH) was performed to isolate genes differentially expressed in human hepatocellular cancer (HCC) tissues. PLAC1 (PLACenta-specific 1) was one of the genes identified highly expressed in HCC tissues but not in paired noncancerous tissues. Further analyses revealed its expression in several other types of cancer tissues as well as tumor cell lines, but not in normal tissues except for placenta. Among HCC samples tested, 32% (22/69) showed PLAC1 mRNA expression while the protein was detected in 23.3% (7/30). A serological survey revealed that 3.8% (4/101) of HCC patients had anti-PLAC1 antibody response, suggesting the immunogenicity of PLAC1 in HCC patients. PLAC1 represents a new class of tumor associated antigen with restricted expression in placenta and cancer tissues, that may serve as a target for cancer vaccination.

PLAC1 mRNA levels in maternal blood at induction of labor correlate negatively with induction–delivery interval

OBJECTIVE

This study was conducted to determine whether, in low risk women having labor induced using prostaglandin gel (dinoprostone gel), there is a relationship between the concentration of mRNA for the PLAC1 gene (a trophoblast-specific gene) in maternal blood and the time elapsed between the first gel administration and spontaneous delivery.

STUDY DESIGN

Blood was collected from 49 selected women at 40.2-41.4 weeks' gestation. Total RNA was extracted by means of an ABI Prism 6100 nucleic acid Prep Station and quantitative real-time PCR analysis was performed by use of a PE Applied Biosystems 5700 Sequence Detection System. Sequence data were obtained from the Genebank Sequence Database. To determine the amount of cDNA, the PLAC1 locus was used.

RESULTS

Thirty women (61.2%) had a spontaneous delivery. A caesarean section, either for fetal dystocia or fetal distress, was performed in 19 (38.8%). The crude delivery rates of the women who ended up with a spontaneous delivery were 30% at 24 h and 43% at 48 h. Women (n=19) with a blood concentration of logPLAC1 mRNA>or=2.00 displayed a median time to delivery of 23.50h, (95% CI: 13.13-33.87) while those with a logPLAC1 mRNA<2.00 (n=30) had a median time of 54 h. (95% CI: 37.86-70.14; p=0.0043, log-rank test). By means of multivariate analysis, quantitative Bishop score (from 2 to 7) at the time of the first gel administration and logPLAC1 mRNA>or=2.00 were associated with a higher rate of delivery per unit of time with an odds ratio of 1.35 (95% CI: 1.07-1.71) and 3.48 (95% CI: 1.55-7.80), respectively.

CONCLUSIONS

In induced term pregnancies, PLAC1 mRNA in maternal blood at the beginning of the treatment correlates with the time elapsed before delivery. This evidence demonstrates that the fetomaternal trafficking of nucleic acids is more consistent when the labor is about to begin.

Cell-Free mRNA Concentrations of Plasminogen Activator Inhibitor-1 and Tissue-Type Plasminogen Activator Are Increased in the Plasma of Pregnant Women with Preeclampsia

Background: Detection of placental mRNA in maternal plasma has been reported in high-risk pregnancies. We attempted to investigate the concentrations of plasminogen activator inhibitor-1 (PAI-1) and tissue-type plasminogen activator (tPA) mRNA in maternal plasma in preeclampsia.

Methods: Peripheral blood samples were obtained from healthy pregnant women before and after delivery and also from women with or without preeclampsia. Plasma was isolated from these samples, and RNA was extracted. Plasma PAI-1 and tPA mRNA concentrations were then measured by use of reverse transcription PCR assays. The concentrations were converted into multiples of the median (MoM) of the controls adjusted for gestational age. Data were stratified and analyzed according to the clinical severity of preeclampsia and quantitative distribution of blood pressure and proteinuria.

Results: The median (minimum–maximum) PAI-1 mRNA MoM values for women with preeclampsia and controls were 2.48 (0.82–8.53) and 1.00 (0.41–2.33), respectively, whereas the median (minimum–maximum) tPA mRNA MoM values were 3.33 (1.01–10.58) and 1.00 (0.95–1.20), respectively. The concentrations of both PAI-1 and tPA mRNA were significantly increased in cases of preeclampsia, compared with controls (P &lt;0.0001). The MoM values of both mRNA species were directly correlated with the severity of preeclampsia and were greatest among a subgroup of hemolysis, increased liver enzymes, and low platelets pregnancies.

Conclusion: Maternal plasma PAI-1 and tPA mRNAs are significantly increased in patients with preeclampsia and are positively correlated with the severity of preeclampsia.

Measurement of mRNA of trophoblast-specific genes in cellular and plasma components of maternal blood

BACKGROUND

Placental mRNA in maternal plasma is suitable for quantitative analysis regardless of fetal gender and genetic polymorphism status.

METHODS

We obtained 155 blood samples from pregnant women to compare human placental lactogen (hPL) and beta-subunit of human chorionic gonadotropin (beta hCG) mRNA and protein levels between the cellular and plasma components of maternal blood. To assess clearance of hPL mRNA expression, we obtained blood samples from nine women immediately before and after delivery by caesarean section. mRNA was extracted from the cellular and plasma components of all samples, and hPL and beta hCG mRNA expression was analysed by reverse transcription-PCR assay.

RESULTS

The concentration of beta hCG mRNA in the cellular component positively correlated with the plasma concentration of beta hCG protein and beta hCG mRNA (p = 0.001 for both). The concentration of hPL protein in the plasma correlated with the hPL mRNA concentration of the cellular component (p<0.05). For both hPL and beta hCG, the mRNA concentration of the cellular component was greater than that of the plasma component (22.9-fold higher for hPL and 4.3-fold higher for beta hCG). The half life of hPL mRNA clearance was significantly longer for the cellular fraction (mean half life = 203.8 min, range 150-3465 min) than for the plasma fraction (mean half life = 32.2 min, range 15-385 min) (p = 0.008).

CONCLUSION

The present findings indicate that the concentration of hPL and beta hCG mRNA is significantly higher in the cellular component of maternal blood samples than in the plasma component. Cellular mRNA in maternal blood is useful for non-invasive evaluation of placental function.

Cell-free mRNA concentrations of CRH,PLAC1, and selectin-P are increased in the plasma of pregnant women with preeclampsia

OBJECTIVE

To compare mRNA concentrations of corticotrophin-releasing hormone (CRH), placenta specific-1 (PLAC1), and selectin-P in preeclamptic and normal pregnancies.

METHODS

Peripheral blood samples were obtained from 43 pregnant women with preeclampsia and 41 control subjects. Plasma was harvested from samples and RNA extracted. Plasma RNA was analyzed using reverse transcription polymerase chain reaction (PCR) assay. Median concentrations of CRH, PLAC1, and selectin-P mRNA in plasma were compared, to assess possible differences in distribution. Data were also stratified and compared according to clinical severity of preeclampsia. Finally, CRH, PLAC1, and selectin-P were plotted against quantitative distributions of blood pressure and proteinuria.

RESULTS

All markers were differently distributed between cases and controls. Median values in subgroups correlated with severity of preeclampsia. All markers correlated with both. Selectin-P was identified as the marker with the highest degree of correlation. No correlation was found between any markers in the control group and proteinuria or blood pressure.

CONCLUSION

CRH, PLAC1, and selectin-P are distributed differently in preeclampsia cases compared to controls and correlate with signs of preeclampsia.

The PLAC1 protein localizes to membranous compartments in the apical region of the syncytiotrophoblast

PLAC1 is a trophoblast-specific gene that maps to a locus on the X-chromosome important to placental development. We have previously shown that PLAC1 gene expression is linked to trophoblast differentiation. The objective of this study was to define the localization of the PLAC1 polypeptide as a prerequisite to understanding its function. Polyclonal antibodies specific for the putative PLAC1 polypeptide were generated. The subcellular localization of PLAC1 in the trophoblast was examined by immunohistochemical analysis of human placenta complemented by immunoblot analysis of subcellular fractions. Brightfield immunohistochemical analysis of placental tissue indicated that the PLAC1 protein localizes to the differentiated syncytiotrophoblast in the apical region of the cell. Deconvlution immunofluorescence microscopy confirmed localization to the apical region of the syncytiotrophoblast. Its distribution included both intracellular compartments as well as loci in close association with the maternal-facing, microvillous brush border membrane (MVM). These findings were supported by immunoblot analysis of subcellular fractions. A 30 kDa band was associated with the microsomal fraction of placental lysates but not the mitochondrial, nuclear, or soluble fractions, suggesting PLAC1 is targeted to a membrane location. Plasma membranes were obtained from the fetal-facing, basal surface (BM) and the maternal-facing, MVM of the syncytiotrophoblast membrane. PLAC1 immunoreactivity was only detected in membrane fractions derived from the apical MVM consistent with immunohistochemical analyses. These data demonstrate that the PLAC1 protein is restricted primarily to the differentiated trophoblast, localizing to intracellular membranous compartment(s) in the apical region of the syncytiotrophoblast and associated with its apical, microvillous membrane surface.

PLAC1 mRNA in maternal blood correlates with Doppler waveform in uterine arteries in normal pregnancies at the second and third trimester

Doppler analysis of the uterine arteries is currently used for pre-eclampsia (PE) screening. PLAC1 is a trophoblast-specific gene, and it is known that in normal pregnancies, trophoblastic cells are released into the maternal circulation, where specific trophoblastic mRNA can be detected. In PE, as in women who eventually develop PE, an abnormal passage of fetal and placental cells is also present. In this study, we aimed to verify whether, in normal pregnancies, Doppler waveform of the uterine arteries correlates with PLAC1 mRNA concentrations. Thirteen cases of normal pregnancies at 37 weeks' gestation (23-41) were enrolled in the study. PLAC1 mRNA was extracted from 2 mL of blood by ABI PRISM 6100 nucleic acid Prep Station (Applied Biosystems, Foster City, CA) and quantitative reverse transcriptase-polymerase chain reaction (RT-PCR) analysis was performed by a PE 5700 Sequence detection system. Bulk RNA from normal placental tissue was used as the reference curve, and the amount of PLAC1 mRNA in the study samples was then expressed as the "relative amount" of weight of placental tissue (ng/mL). The uterine arterial mean resistance index (RI) and presence/absence of a dicrote waveform were calculated by using a 5 MHz transabdominal probe (Tecnos, ESAOTE) at the uterine cervico-corporal junction. Doppler measurement was performed on the same day as blood collection. The median of the means of uterine arterial RI was 0.52 (0.39-0.68). RI of uterine arteries and PLAC1 mRNA were significantly correlated in a log-linear regression (R(2) = 0.483, P = 0.024). Our data support that in normal pregnancy, the passage of trophoblast material into the maternal circulation is correlated with the quantitative measurement of uterine hemodynamics.

Recovery and amplification of placental RNA from dried maternal blood spots: utility for non-invasive prenatal diagnosis

Methods utilizing circulating cell-free RNA in plasma have clinical applications for cancer and prenatal genetic analysis. Given these potential roles, the feasibility of detecting placental specific RNA in dried maternal blood spots after storage at room temperature for varying lengths of time was investigated. Using real-time polymerase chain reaction (PCR), positive amplification of placental-specific beta-human chorionic gonadotrophin transcripts was demonstrated in nine of 11 dried blood samples from first and second trimester pregnancies stored at room temperature for up to 4 weeks. This work demonstrates feasibility in isolation and amplification of placental mRNA using dried maternal blood spots. With the development of fetal and placental RNA markers, this approach would allow simplified collection, transport, and storage of samples for prenatal genetic diagnosis and pregnancy related complications.