Rapid clearance of fetal DNA from maternal plasma

Effect of labor on postpartum clearance of cell-free fetal DNA from the maternal circulation

OBJECTIVE

The aim of this study was to compare the effect of mode of delivery on the postpartum clearance of cell-free fetal (cff) DNA.

METHODS

Women who gave birth to a single-term male infant by any mode of delivery had blood collected on three occasions: within 3 h of birth, on day 1-2 postpartum and at 2 weeks postpartum. The SRY sequence was used as a marker of cff DNA, and was detected using conventional PCR.

RESULTS

Eighty-seven women were included in the study. There were 28 women in the elective caesarean section group and 59 in the labor group. Cell-free fetal DNA was detected in 38/87 (44%) of women within 3 h of birth. There was a significant difference between the group that labored and the group that did not (54 vs 21%, p = 0.003). Twelve percent of women who labored had persistent cff DNA on day 1-2 postpartum, compared with none of the women who delivered without labor. No woman had DNA that persisted up to 2 weeks postpartum.

CONCLUSION

The presence of labor increases the rate of detectable DNA in women within 3 h of birth and on day 1-2 postpartum. Postpartum clearance was completed by 2 weeks in all women tested regardless of mode of delivery.

Early noninvasive prenatal detection of a fetal CRB1 mutation causing Leber congenital amaurosis

PURPOSE

Leber congenital amaurosis (LCA) is one of the most severe inherited retinal dystrophies with the earliest age of onset. Mutations in the Crumbs homologue 1 (CRB1; OMIM 600105) gene explain 10%-24% of cases with LCA depending on the population. The aim of the present work was to study a fetal mutation associated to LCA in maternal plasma by a new methodology in the noninvasive prenatal diagnosis field: the denaturing High Performance Liquid Chromatography (dHPLC).

METHODS

This study presents the case of a compound heterozygous fetus for two mutations in CRB1 (1q3.1-q32.2). dHPLC and automated DNA sequencing were used to detect the paternally inherited fetal mutation in a maternal plasma sample collected at the 12th week of gestation. To test the detection limit of dHPLC, we made serial dilutions of paternal DNA in control DNA.

RESULTS

We were able to detect the presence of the paternally inherited fetal CRB1 mutation in maternal plasma by dHPLC. Moreover, by comparing chromatograms of serial dilutions to the plasma sample, we could ascertain that the percentage of fetal DNA in maternal plasma was at least 2%. However, the detection of the fetal mutation was not possible by automated DNA sequencing.

CONCLUSIONS

dHPLC seems to be sensitive enough to detect small amounts of fetal DNA in maternal plasma samples. It could be a useful tool for the noninvasive prenatal detection of paternally inherited point mutations associated with retinopathies.

Fetomaternal trafficking in the mouse increases as delivery approaches and is highest in the maternal lung

The purpose of the study was to understand in more detail the natural history of fetomaternal cell trafficking in healthy pregnant mice. Our goal was to identify the best target organs and days during pregnancy for further mechanistic studies of the role of fetal cells in maternal disease and injury. C57BL/6J wild-type virgin females (n = 54) were mated with congenic enhanced green fluorescent protein (EGFP) transgenic males. During pregnancy and after delivery, female mice were euthanized, and eight organs and blood were analyzed for the presence of fetal GFP+ cells with flow cytometry and real-time quantitative PCR. Maternal lungs, liver, and spleen were also analyzed by fluorescent stereomicroscopy. Fetal GFP+ cells were first found at low frequency at Embryonic Day 11, increased to a maximum at Embryonic Day 19, and decreased rapidly postpartum. These fetal cell dynamics were significantly reproducible among all mice studied. In addition, there was a consistent distribution of fetal cells within maternal organs, with lung, liver, blood, and spleen having the greatest concentrations; these were highly correlated at all time points (P < 0.0001). Maternal lung contained 10- to 100-fold more fetal cells than any other organ, and using all three techniques, the number of fetal cells detected was the most consistent and reproducible in this organ. Stereomicroscopy showed that within the lung, fetal cells were widely and apparently randomly distributed. Using a murine model, our data demonstrate that fetomaternal cellular trafficking occurs in reproducible patterns, is maximal near term delivery, and has predilection for the maternal lung.

Noninvasive prenatal diagnosis of aneuploidy using cell-free nucleic acids in maternal blood: promises and unanswered questions

The discovery of cell-free fetal (cff) DNA and RNA in the maternal circulation has driven developments in noninvasive prenatal diagnosis (NIPD) for the past decade. Detection of paternally derived alleles in cff DNA is becoming well established. Now much interest is focussing on NIPD of fetal chromosomal abnormalities, such as trisomy 21, which is a considerable challenge because this demands accurate quantitative measurements of the amounts of specific cff DNA or cff RNA sequences in maternal blood samples. Emerging strategies for distinguishing and quantifying the fetal nucleic acids in the maternal circulation promise continued development of the field, and pose a number of unanswered questions.

Cell-free plasma DNA as a predictor of outcome in severe sepsis and septic shock

BACKGROUND

Increased concentrations of cell-free DNA have been found in plasma of septic and critically ill patients. We investigated the value of plasma DNA for the prediction of intensive care unit (ICU) and hospital mortality and its association with the degree of organ dysfunction and disease severity in patients with severe sepsis.

METHODS

We studied 255 patients with severe sepsis or septic shock. We obtained blood samples on the day of study inclusion and 72 h later and measured cell-free plasma DNA by real-time quantitative PCR assay for the beta-globin gene.

RESULTS

Cell-free plasma DNA concentrations were higher at admission in ICU nonsurvivors than in survivors (median 15 904 vs 7522 genome equivalents [GE]/mL, P < 0.001) and 72 h later (median 15 176 GE/mL vs 6758 GE/mL, P = 0.004). Plasma DNA values were also higher in hospital nonsurvivors than in survivors (P = 0.008 to 0.009). By ROC analysis, plasma DNA concentrations had moderate discriminative power for ICU mortality (AUC 0.70-0.71). In multiple regression analysis, first-day plasma DNA was an independent predictor for ICU mortality (P = 0.005) but not for hospital mortality. Maximum lactate value and Sequential Organ Failure Assessment score correlated independently with the first-day plasma DNA in linear regression analysis.

CONCLUSIONS

Cell-free plasma DNA concentrations were significantly higher in ICU and hospital nonsurvivors than in survivors and showed a moderate discriminative power regarding ICU mortality. Plasma DNA concentration was an independent predictor for ICU mortality, but not for hospital mortality, a finding that decreases its clinical value in severe sepsis and septic shock.

Non-invasive prenatal diagnosis of single gene disorders: how close are we?

Analysis of cell free fetal DNA (cffDNA) in maternal plasma provides the opportunity for reliable, timely, safe and cost-effective diagnosis of single gene disorders. The detection of certain fetal loci using cffDNA and conventional molecular analytic approaches is possible from 4 weeks gestation. To date, non-invasive first-trimester analysis for single gene disorders has been limited by assay sensitivity and specificity, due to the background maternal DNA. The anticipated ability to enrich the fetal component of cell free DNA will increase the robustness of tests and permit semi-quantitative analysis, broadening the scope of testing to include recessive disorders such as cystic fibrosis. Testing for large-scale mutations might remain limited by the fragmented nature of cffDNA and, when testing very early in gestation, careful ultrasound examination will be needed to determine the number of gestational sacs, because of the risk of discordant twin pregnancies.

Non-invasive prenatal diagnosis: implications for antenatal diagnosis and management of high-risk pregnancies

There has been a huge effort in the last 2-3 decades to develop non-invasive prenatal diagnosis to avoid the risks to the fetus caused by invasive procedures. Obtaining fetal nucleic material for molecular analysis without the need of invasive procedures has been a goal of prenatal diagnosis for many years; this is now been made possible by the use of non-cellular fetal nucleic acids circulating in maternal blood. The placenta is the primary source of these nucleic acids, raising the possibility that they could be a marker for pregnancy complications resulting from placental disease/dysfunction such as pre-eclampsia and fetal growth restriction. If so, these markers might be able to identify cases at risk, predict disease and/or its severity or allow early diagnosis. This has the potential to allow improvements in the management of complicated pregnancies.

Foetal sex determination in maternal blood from the seventh week of gestation and its role in diagnosing haemophilia in the foetuses of female carriers

The existence of foetal DNA in maternal blood, discovered in 1997, opened new possibilities for noninvasive prenatal diagnosis. This includes foetal sex assessment by the detection of specific Y chromosome sequences in maternal blood, particularly important when a foetus may be affected by an X-linked disorder such as haemophilia. This study aims to validate this sex assessment method and to test its clinical utility in the diagnosis of 15 potentially affected pregnancies in female carriers of haemophilia. In the validation study, 316 maternal blood samples from 196 pregnant women at gestations ranging from 5 weeks to 12 weeks were analysed. In the clinical study, 15 pregnancies at risk of having a haemophilic foetus were tested. All pregnancies in the validation study were correctly diagnosed. The accuracy and specificity of the methodology from the seventh week of gestation was 100%. The sex of all 15 pregnancies identified as being at risk of bearing a haemophilic foetus was correctly diagnosed. Foetal sex assessment by detecting specific Y chromosome sequences in maternal blood is now routinely used in our hospital because of its high accuracy from the seventh week of gestation. Reliable foetal gender determination from maternal blood of pregnant women carriers of haemophilia in the first trimester of gestation can avoid more conventional, invasive methods of prenatal diagnosis.

Plasma DNA: a molecular marker of surgical insult and postoperative recovery in esophageal cancer

AIM

To assess plasma DNA changes intraoperatively, to relate plasma DNA to the magnitude of the surgical insult and to monitor the changes during the postoperative recovery period.

MATERIAL AND METHOD

Prospective study of 35 patients with esophageal cancer who had esophagectomy of different magnitudes: 19 esophagectomy without thoracotomy and 16 esophagectomy with thoracotomy. The plasma DNA was measured prior to surgery, throughout the course of the operation on four different intervals, and on postoperative days 1, 3, 5, and 7.

RESULTS

A significant difference was seen in the median plasma DNA intraoperatively between the two groups: esophagectomy without thoracotomy, 507 ng/ml/min (range 211-2,708), esophagectomy with thoracotomy, median 1,098 ng/ml/min (range 295-22,284; p = 0.014). Postoperative complications were identified in 6 patients who demonstrated a significant elevation in plasma DNA on postoperative days 5 and 7.

CONCLUSION

Plasma DNA increases during surgery as a result of cell damage and the rise correlates with the magnitude of surgery. The descent of plasma DNA postoperatively correlates with surgical recovery. Elevation of the plasma DNA during the postoperative period correlates with postoperative complications. Plasma DNA is an objective molecular marker of surgical insult and can be used to monitor postoperative recovery after esophagectomy.

DNA methylation in circulating tumour DNA as a biomarker for cancer

Free circulating DNA, which is thought to be derived from the primary tumour, can be detected in the blood of patients with cancer. Detection of genetic and epigenetic alteration in this tumour DNA offers a potential source of development of prognostic and predictive biomarkers for cancer. One such change is DNA methylation of the promotor region of tumour suppressor genes. This causes down regulation of tumour suppressor gene expression, a frequent event in carcinogenesis. Hypermethylation of the promotor region of a number of genes has been detected in many tumour types and more recently these changes have been detected in circulating tumour DNA. This review will summarise the literature detailing DNA methylation in circulating tumour DNA and discuss some of the current controversies and technical challenges facing its use as a potential biomarker for cancer.

DNA Methylation in Circulating Tumour DNA as a Biomarker for Cancer

Free circulating DNA, which is thought to be derived from the primary tumour, can be detected in the blood of patients with cancer. Detection of genetic and epigenetic alteration in this tumour DNA offers a potential source of development of prognostic and predictive biomarkers for cancer. One such change is DNA methylation of the promotor region of tumour suppressor genes. This causes down regulation of tumour suppressor gene expression, a frequent event in carcinogenesis. Hypermethylation of the promotor region of a number of genes has been detected in many tumour types and more recently these changes have been detected in circulating tumour DNA. This review will summarise the literature detailing DNA methylation in circulating tumour DNA and discuss some of the current controversies and technical challenges facing its use as a potential biomarker for cancer.

Y chromosome detection by Real Time PCR and pyrophosphorolysis-activated polymerisation using free fetal DNA isolated from maternal plasma

OBJECTIVES

To validate the use of Real Time PCR, a widely used technique that can detect very low levels of Y chromosomal sequence, and to assess the use of a highly sensitive PCR technique, pyrophosphorolysis-activated polymerisation (PAP), for fetal sex determination using free fetal DNA (ffDNA).

METHODS

The fetal sex was determined by Real Time PCR in 58 pregnancies using ffDNA isolated from maternal plasma. In parallel with the Real Time PCR experiments, the presence of Y chromosome sequence was also determined using PAP on 54 isolated ffDNA samples.

RESULTS

Both techniques detected Y chromosome sequence at very low levels with 98% specificity and 100% sensitivity (Real Time n = 44, PAP n = 54). Furthermore, the PAP technique was shown to be more robust than the Real Time PCR as none of the samples tested failed to meet the acceptance criteria. Combining the two techniques for male fetal sex detection from maternal blood plasma increases the sensitivity and specificity to 100% in this series.

CONCLUSIONS

This study shows that both Real Time PCR and PAP can be used for Y chromosome detection on ffDNA. Furthermore, by using PAP in combination with Real Time PCR more reliable early prenatal sexing can be performed using ffDNA.

Prognostic value of preoperative serum cell-free circulating DNA in men with prostate cancer undergoing radical prostatectomy

PURPOSE

We evaluated the association of preoperative serum cell-free circulating DNA concentration in men with clinically localized prostate cancer who underwent radical prostatectomy with prostate-specific antigen (PSA) recurrence.

EXPERIMENTAL DESIGN

One hundred and ninety-two men with clinically localized prostate cancer, who underwent radical prostatectomy at the Johns Hopkins Hospital and had preoperative serum available for analyses constituted our study population. All serum samples were collected before prostate biopsy or at least 4 months after prostate biopsy. The total amount of serum cell-free circulating DNA from each sample was calculated using a standard curve generated via quantitative real-time PCR. PSA recurrence was defined as a single postoperative PSA level of > or =0.2. The natural logarithm (ln) of the DNA concentration was used for statistical analyses.

RESULTS

Of the 192 men in our study, 56 (29%) experienced PSA recurrence within the study period (median time to PSA recurrence 2 years). The median follow-up time for men free of disease at last follow-up was 3 years. The median serum cell-free DNA concentration of all men in the study was 5.3 ng/mL (mean 18.05 ng/mL; range 0.2-320 ng/mL). The mean serum DNA concentration for men who recurred and for those who did not was 3.8 +/- 34.1 and 13.7 +/- 33.6 ng/mL, respectively (P = 0.001). In a univariate analysis, ln DNA concentration was significantly associated with PSA recurrence (hazard ratio, 1.49; 95% confidence interval, 1.3-1.8; P < 0.001). In the multivariate model, ln DNA concentration was significantly associated with PSA recurrence (hazard ratio, 2.56; 95% confidence interval, 1.1-1.6; P = 0.003). Using bootstrap analyses, serum cell-free DNA concentrations > or =5.75 ng/mL were associated with an increased risk of PSA recurrence within 2 years of radical prostatectomy.

CONCLUSION

Our study suggests that preoperative serum cell-free DNA concentration may be a useful prognostic biomarker for men with clinically localized prostate cancer treated with radical prostatectomy.

No correlation between the number of fetal nucleated cells and the amount of cell-free fetal DNA in maternal circulation either before or after delivery

OBJECTIVES

We have determined the number of fetal nucleated cells and the concentration of cell-free fetal DNA in parallel in the same maternal blood samples either before or after delivery, and studied the relationship between these two.

METHODS

Venous blood samples were taken at four points around delivery from ten women who had singleton male fetus with informed consent. The number of fetal nucleated cells having a Y chromosome specific signal treated by two-color fluorescence in situ hybridization technique was counted using maternal whole blood. The concentration of sex-determining region Y gene sequence was determined using real-time quantitative PCR.

RESULTS

The number of fetal nucleated cells decreased after delivery, and some fetal cells were present 1 month after delivery. While cell-free fetal DNA decreased rapidly after delivery and became undetectable 1 day after delivery in eight out of ten cases. The number of fetal nucleated cells did not correlate with the concentration of cell-free fetal DNA in maternal circulation.

CONCLUSION

The present study demonstrates that cell-free fetal DNA disappears very rapidly after delivery and fetal nucleated cells remain longer in maternal circulation, and that there is no correlation between these two either before or after delivery.

Circulating DNA: a potential marker of sickle cell crisis

Free circulating DNA is present in the plasma of healthy subjects, and is elevated in conditions characterized by increased cell death, such as cancer and physical trauma. Analysis of circulating DNA in plasma could provide a useful biomarker in sickle cell disease (SCD) in view of the increased cell turnover through chronic ongoing haemolysis, recurrent vaso-occlusion and inflammation. Plasma DNA was determined by real-time quantitative polymerase chain reaction (PCR) amplification of the beta-globin gene (HBB) in 154 patients with SCD [105 haemoglobin (Hb)SS, 46 HbSC and three HbS/beta(0) thalassaemia] and 53 ethnically matched controls. Blood samples were obtained from all patients in steady state; 21 of the 154 patients were also sampled during admission to hospital for acute pain. Median concentration of circulating plasma DNA in acute pain was more than 10-fold that in steady state and in controls - 10070 vs. 841 and 10070 vs. 933 genome equivalents/ml respectively (P < 0.0001, in both cases). During steady state, patients had plasma DNA levels similar to controls. Plasma DNA levels in SCD correlated with C-reactive protein levels (P < 0.005) and total white cell counts (P < 0.05) in steady state. The study shows that plasma DNA concentration may have potential as a biomarker in sickle cell patients.

Increased concentrations of antibody-bound circulatory cell-free DNA in rheumatoid arthritis

BACKGROUND

Increased concentrations of cell-free DNA have been found in several disorders and have been interpreted as evidence of increased rates of cell death or turnover. Evidence from in vitro and animal experiments suggests that DNA may play a role in the pathogenesis of rheumatoid arthritis (RA).

METHODS

We measured cell-free DNA in plasma and serum from patients with RA and healthy controls by use of quantitative PCR for glyceraldehyde-3-phosphate dehydrogenase (GAPDH) DNA. We used protein G Sepharosetrade mark bead adsorption of plasma and elution to isolate antibody-bound DNA.

RESULTS

In paired plasma and serum samples of 16 healthy controls the median GAPDH copies were 4500 genome equivalents (GE)/mL plasma (range 319-21 000) and in 26 RA patients 17 000 GE/mL plasma (2100-2 375 000, P = 0.0001). In the serum from normal controls the median GAPDH copies were 35 000 GE/mL (1700-239 000) and from RA patients 222 000 GE/mL (21 000-2 375 000, P = 0.004). A median of 81% of the cell-free DNA in RA was associated with antibody compared with 9% in healthy controls (P = 0.001). The concentrations of DNA did not vary with the type of therapy patients received.

CONCLUSIONS

These results provide new evidence for a role of cell-free DNA-antibody complexes in the etiology of RA, suggest new avenues for basic research, and may prove to be relevant to diagnosis and assessment of therapy.

Circulating nucleic acids in plasma/serum

Since the discovery of circulating nucleic acids in plasma in 1948, many diagnostic applications have emerged. For example, diagnostic and prognostic potentials of circulating tumour-derived DNA have been demonstrated for many types of cancer. The parallel development of fetal-derived DNA detection in maternal plasma has opened up the possibility of non-invasive prenatal diagnosis and monitoring of many pregnancy-associated disorders. In this regard, non-invasive fetal rhesus blood group genotyping has already been translated to clinical practice. Other applications of circulating DNA in traumatology and transplant monitoring have also been reported. The more recent discoveries of circulating tumour-derived RNA and fetal-derived RNA have proven to be equally important as their DNA counterparts. Successful prenatal diagnosis of Down's syndrome by fetal RNA analysis has recently been reported. However, the definite origin and release mechanisms of circulating nucleic acids have remained incompletely understood, with cell death being suggested to be associated with such nucleic acid release. Pre-analytical standardisation will become increasingly relevant when comparing data from different laboratories. In conclusion, studies of circulating nucleic acids have promised exciting developments in molecular diagnostics in the years to come.

Short-term clearance of cell-free nucleic acids after first-trimester termination of pregnancy

To determine the kinetics of the short-term clearance of cell-free nucleic acids in maternal plasma, we conducted a prospective cohort study of 36 women who underwent first-trimester elective surgical termination. By using real-time polymerase chain reaction (PCR) amplification and measurement of the sex-determining region of the Y chromosome (SRY) gene (as a marker of fetal DNA), beta-hCG (a placental messenger RNA transcript), and glyceraldehyde phosphate dehydrogenase (GAPDH; as a marker of both total DNA and mitochondrial RNA), we found that cell-free nucleic acids in maternal plasma are not cleared within 90 minutes after the procedure, in contrast to the case of term delivery, in which levels decrease rapidly after birth.

Role of Plasma DNA as a Predictive Marker of Fatal Outcome following Severe Head Injury in Males

The prediction of outcome is one of the major problems associated with traumatic brain injury. Recently, investigations have been performed on the potential use of circulating cell-free DNA in plasma for clinical diagnosis and prognosis of a variety of conditions. In this study, we investigated DNA plasma concentrations after severe traumatic brain injury (TBI) and its correlation with primary outcome. We studied 41 male victims of TBI, with isolated severe TBI or severe TBI with associated exracranial injuries. Control samples were obtained from 13 healthy male volunteers. Plasma DNA was measured by a real-time PCR assay for the beta-globin gene. The mean time for first sampling (study entry) was 11.7 +/- 5.2 h after injury; subsequent DNA determinations were performed 24 h after study entry. Mean plasma DNA concentrations were significantly increased in TBI patients (366,485 and 131,708 kilogenomes-equivalents/L, at study entry and 24 h later, respectively) compared with the control group (3031 kilogenomes-equivalents/L). Additionally, a significant correlation between higher plasma DNA concentrations, determined 24 h after study entry, and fatal outcome was observed. However, at second sampling, there was no significant correlation between plasma DNA concentrations and the presence of associated extracranial injuries. High plasma DNA concentrations at second sampling time predicted fatal outcome with a sensitivity of 67% and specificity of 76%, considering a cut-off value of 77,883 kilogenomes-equivalents/L. Thus, this study showed that severe TBI is associated with elevated DNA plasma levels and suggests that persistent DNA elevations correlate with mortality.

Placenta Accreta: A Review of Current Advances in Prenatal Diagnosis

Placenta accreta is a life-threatening obstetrical condition requiring a multidisciplinary approach. Despite identified obstetrical risk factors, the diagnosis is often made at the time of delivery. Recent advances in biology could allow a prenatal screening of placenta accreta with the identification of biological markers in maternal blood including cell-free fetal DNA, placental mRNA, and DNA microarray. These promising technologies can detect the presence of anomalies and should play a future role in developing a better understanding of placental invasion. Ultrasound imaging is popular due to its low cost and accessibility and widely used for the screening of placenta location and potential abnormal development. This exam is associated with high sensitivity and specificity for diagnosis of placenta accreta when specific defined criteria are used for the diagnosis. A placental MRI provides a morphological description, as well as recently demonstrated topographical information that optimizes diagnosis and surgical management. The screening of placenta accreta should be improved with the use of a combination of these diagnostic techniques and benefit high-risk populations with a reduction in morbidity.

Free fetal DNA in maternal plasma in anembryonic pregnancies: confirmation that the origin is the trophoblast

OBJECTIVE

To test the hypothesis that free fetal DNA (ffDNA) circulating in maternal plasma originates mainly from the placenta we studied ffDNA levels in anembryonic pregnancies.

METHODS

Maternal blood samples were collected from 15 normal first-trimester pregnancies in which fetal sex was subsequently determined and nine patients with a diagnosis of anembryonic gestation (AG). The Y chromosome DYS14 gene was quantified by real-time quantitative PCR (RT-PCR) for the determination of fetal sex in both plasma and chorionic tissue samples. Fetal sex in chorionic tissue samples was also determined using quantitative fluorescence PCR (QF-PCR).

RESULTS

The correct sex result was obtained from maternal plasma in all. Four AG pregnancies were female (DYS14 negative) results. In five of the AG cases, the chorionic tissue was found to be male (by both QF-PCR and RT-PCR which agreed) and positive male signal was found in maternal plasma by RT-PCR. There was no statistical difference between median free fetal DNA concentration in plasma between the AG male cases (148.3 GE/mL) and controls (145.8 GE/mL).

CONCLUSION

Since ffDNA levels are normal in pregnancies without a fetus, the data support the hypothesis that the trophoblastic cells are the major source ffDNA in maternal plasma.

Modifying the proliferative state of target cells to control DNA expression and identifying cell types transfected in vivo

Although the majority of current gene transfer techniques have focused on increasing the ability of the DNA to enter the cell, it is possible that changing the proliferative and migratory state of cells will influence the cells ability to take up and express plasmid DNA. This study was designed to test the hypothesis that growth factors (basic fibroblast growth factor (bFGF) and hepatocyte growth factor/scatter factor (HGF/SF)) used to alter the proliferative and migratory state of cells can alter plasmid DNA uptake and expression. In vitro studies indicate that enhancing cell proliferation with growth factor exposure enhances plasmid DNA uptake and expression. Furthermore, dual localized delivery of bFGF and plasmid DNA in vivo increases the expression, 3-6 times over control, as compared to plasmid delivery alone. Dual delivery of a factor promoting cell proliferation and a plasmid led to a further increase in the expression of the plasmid encoding bone morphogenetic protein-2 in a rat cranial defect by specific cell populations. The results of these studies suggest that increasing the proliferative state of target cell populations can enhance non-viral gene transfer.

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.

The remission of rheumatoid arthritis during pregnancy

Rheumatoid arthritis (RA) is an autoimmune disease that is favorably influenced by pregnancy but relapses after delivery. A variety of circulating factors has been considered as candidates for inducing gestational improvement of RA; however, the factors/pathways responsible remain still elusive. This review discusses recent research on the effect of pregnancy on RA with a focus on immunregulation, cytokine secretion, HLA antigens, microchimerism, and innate immunity. The complex hormonal and immunological alterations of pregnancy may temporarily correct the disturbed immunregulation of RA.

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.

Circulating free DNA in plasma or serum as biomarker of carcinogenesis: practical aspects and biological significance

The presence of small amounts of tumor DNA in cell free DNA (CFDNA) circulating in the plasma or serum of cancer patients was first demonstrated 30 years ago. Since then, overall plasma DNA concentration in cancer patients and genetic or epigenetic alterations specific to tumor DNA have been investigated in patients diagnosed with different types of cancer. The proportion of patients with altered CFDNA varies with the pathology and the nature of the marker. However, several studies have reported the presence of altered CFDNA in over 50% of cancer patients, suggesting that this marker may be common and amenable for a variety of clinical and epidemiological studies. Because the mechanisms and timing of CFDNA release in the blood stream are poorly understood, only few studies have addressed the use of CFDNA for early cancer detection or as a biomarker for mutagenesis and tumourigenesis in molecular epidemiology. In this review, we discuss the technical issues involved in obtaining, using and analyzing CFDNA in cancer or healthy subjects. We also summarize the literature available on the mechanisms of CDNA release as well as on cross-sectional or prospective studies aimed at assessing the clinical and biological significance of CFDNA. These studies show that, in some circumstances, CFDNA alterations are detectable ahead of cancer diagnosis, raising the possibility of exploiting them as biomarkers for monitoring cancer occurrence. Testing these hypotheses will require well-designed studies, assessing multiple markers with quantitative and sensitive methods, with adequate follow-up of subjects, and we provide recommendations for the development of such studies.

Polymerase-chain-reaction-based detection of fetal rhesus D and Y-chromosome-specific DNA in the whole blood of pregnant women during different trimesters of pregnancy

OBJECTIVE

The aim of this study was to determine whether or not a noninvasive procedure utilizing maternal peripheral blood as the source of DNA and polymerase chain reaction (PCR) could be used to detect fetal rhesus D (RhD) status as well as fetal gender during different gestational stages of pregnancy.

MATERIALS AND METHODS

Maternal blood samples were obtained from 54 RhD-negative pregnant women during the first trimester (6-13 weeks, n = 14), second trimester (14-26 weeks, n = 26) and third trimester (27-40 weeks, n = 14). Genomic DNA was extracted from the whole blood and analyzed by seminested and nested PCR for detection of DNA sequences corresponding to RhD (n = 54) and Y chromosome (n = 48) using RhD and Y-chromosome-specific oligonucleotide primers, respectively. The seminested/nested PCR results were compared with the RhD status and gender of the babies after delivery.

RESULTS

The sensitivity and specificity of seminested PCR for detection of fetal RhD positivity in whole blood of pregnant women were 81 and 100%, respectively, while the sensitivity and specificity of nested PCR for detection of male fetuses, using Y-chromosome-specific DNA as a marker, were 96 and 91%, respectively. There were no significant differences in the PCR results with samples obtained from women at different gestational stages of pregnancy.

CONCLUSION

Seminested and nested PCRs for detection of fetal RhD and gender status, respectively, by using the blood of pregnant women during different gestational stages of pregnancy, are reliable noninvasive procedures with high sensitivity and specificity.

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.

Use of maternal plasma for non-invasive prenatal diagnosis of fetal ABO genotypes

BACKGROUND

Measurement of free fetal DNA in maternal plasma opened a door for non-invasive prenatal diagnosis. Prenatal diagnosis of fetal ABO genotypes can provide a basis for the prevention and therapy of maternal-fetal incompatibility. We identified fetal ABO genotypes using fetal DNA in plasma from pregnant women with blood group O. The aim of the study was to investigate the accuracy and feasibility of this method.

METHODS

A total of 105 blood group O women in middle or late pregnancy were enrolled. Fetal DNA in maternal plasma and genomic DNA in umbilical vein blood from newborns were extracted using a QIAamp DNA Blood Kit. DNA was amplified to identify ABO genotypes by PCR with sequence-specific primers (PCR-SSP). The genotype results were evaluated using serologic tests for ABO phenotyping.

RESULTS

Using DNA from umbilical vein blood, ABO genotypes of 105 newborns were successfully identified by PCR-SSP. Using fetal DNA from maternal plasma, 88.6% (93/105) fetal ABO genotypes was correct; 12 false results were from 66 pregnant women with fetuses of type non-O. The accuracy in middle pregnancy was lower than that in late pregnancy, although the difference was not significant (0.05<p<0.10).

CONCLUSIONS

It is feasible to use measurement of fetal DNA in plasma from pregnant women with blood group O for prenatal diagnosis of fetal ABO genotypes. The method is useful for the diagnosis and therapy of ABO maternal-fetal incompatibility and hemolytic disease of the newborn.

Prenatal diagnosis using cell-free nucleic acids in maternal body fluids: A decade of progress

The ability to detect cell-free fetal nucleic acids in pregnant women has greatly evolved over the past decade. Dozens of papers have explored the biology, kinetics, and clinical significance of both cell-free fetal DNA and mRNA in the maternal circulation. As a result, our overall understanding of fetal nucleic acid trafficking has expanded. To date, two applications, gender determination and fetal RhD status, have translated into clinical medicine. However, with advanced molecular techniques such as mass spectrometry, real-time quantitative polymerase chain reaction, and gene expression arrays, the ease with which fetal genes can be detected within the mother has greatly improved. Newly identified placental and fetal mRNA transcripts as well as an epigenetically modified placental DNA marker, maspin, have universal applicability. Global expression analyses of fetal mRNA in both amniotic fluid and blood provide new insights into fetal development and pathology. Prenatal diagnosis is poised to evolve from detection of aneuploidy to detection of deviation from normal development, which should provide novel opportunities for fetal treatment.

Haemophilia A: molecular insights

Haemophilia A is the most common inherited bleeding disorder caused by defects in the

Clin Chem Lab Med 2007;45:450–61.

Prenatal diagnosis: progress through plasma nucleic acids

Over the past 40 years, much effort has been spent on developing non-invasive prenatal diagnostic methods. Since 1997, the progress of this field has been accelerated by the unexpected finding of extracellular fetal nucleic acids in maternal plasma. These developments have been translated into many novel genetic, epigenetic and gene-expression markers, and are expected to have a fundamental impact on the future practice of prenatal diagnosis.

Non-invasive fetal sex determination using real-time PCR

OBJECTIVE

The aim of this study was to evaluate the specificity and sensitivity of the real-time quantitative PCR method for fetal gender determination in early pregnancy.

METHODS

Blood samples were collected from 46 pregnant women prior to amniocentesis. DNA was extracted from maternal plasma using a QIAmp DNA Blood Mini Kit. DNA samples were subjected to real-time quantitative PCR amplification of SRY (as a fetus-specific marker) and beta-globin (as a marker for total plasma DNA) genes.

RESULTS

The beta-globin gene sequence was detected in all samples. The SRY gene was detected in 25 of 28 plasma samples from women with male fetuses and in none of the 18 samples from women with female fetuses (sensitivity 89.2% and specificity 100%). The fetal gender was correctly determined in 43 (93.5%) of 46 maternal plasma samples. The concentration of the beta-globin gene ranged from 161 to 25,568 genome-equivalents (GE)/mL (median 1051.1), while the concentration of the SRY gene ranged from 5 to 166 GE/mL (median 27.4). The percentage of free fetal DNA ranged from 0.1% to 46.1% (median 2.0%).

CONCLUSION

Amplification of fetal DNA from maternal plasma by real-time quantitative PCR is a promising method for fetal sex determination in early pregnancy. However, further studies are necessary before this procedure can be included into a clinical routine.

Évaluation de la détermination du statut Rhésus-D fœtal sur plasma maternel par la technique d’hemi-nested PCR

AIMS

The aim of our study was to evaluate the possibility of identifying the fetal RhD status in maternal plasma using conventional hemi nested PCR analysis.

SUBJECTS AND METHODS

After informed written consent, 20 mL of peripheral blood were collected in 99 D-negative pregnant women either at an amniocentesis for prenatal diagnosis or at a prenatal checkup. Fetal DNA extracted from 400 microL of maternal plasma was analyzed by two different operators with a hemi-nested PCR extending an area of the RhD gene exon 10. The results were compared to the fetal RhD status obtained by PCR amniotic fluid analysis or blood analysis of newborns after delivery. The influence of mother's and baby's phenotype were also studied.

RESULTS

Among the 99 D-negative pregnant women, all Caucasian, 47 were in their second trimester and 52 in their third trimester (mean: 27.20 weeks of gestation +/-8.25). Sixty-nine fetuses were D-positive and thirty D-negative. The sensitivity and specificity of our technique were respectively 100% and 86.7% and 15% of discordant results were observed between the two operators. Four false positives were observed. According to maternal phenotype, a fetal unexpressed RHD gene was suspected in only one case because of a particular fetal phenotype (ddCcEe).

CONCLUSION

A conventional hemi nested PCR analysis of maternal plasma could be used for accurate fetal RhD status. However this procedure is difficult to apply for routine analysis because of the importance of anti-contamination measures required to obtain good results. Real time quantitative PCR analysis on fetal DNA is more suitable. Whatever the operating procedure used, polymorphism of RhD gene may follow in either false negative from presence of rearranged gene or false positive from occasional presence of a non functional RHD gene.

Circulating nucleic acids (CNAs) and cancer--a survey

It has been known for decades that it is possible to detect small amounts of extracellular nucleic acids in plasma and serum of healthy and diseased human beings. The unequivocal proof that part of these circulating nucleic acids (CNAs) is of tumor origin, initiated a surge of studies which confirmed and extended the original observations. In the past few years many experiments showed that tumor-associated alterations can be detected at the DNA and RNA level. At the DNA level the detection of point mutations, microsatellite alterations, chromosomal alterations, i.e. inversion and deletion, and hypermethylation of promoter sequences were demonstrated. At the RNA level the overexpression of tumor-associated genes was shown. These observations laid the foundation for the development of assays for an early detection of cancer as well as for other clinical means.

Circulating Nucleic Acids and Critical Illness

This article reviews some of the early work that has been performed to investigate the potential roles of circulating nucleic acids as prediction markers in acute illness and injury. Circulating DNA and RNA concentrations are elevated early in patients with trauma, stroke and ACS, and are generally highest in patients with a high risk of death. Circulating nucleic acids may be useful markers for the evaluation and risk-stratification of such patients.

Placental RNA in Maternal Plasma: Toward Noninvasive Fetal Gene Expression Profiling

The recent demonstration of the presence of placenta-derived fetal RNA in maternal plasma has opened up new opportunities for noninvasive prenatal investigation. Circulating fetal RNA analysis could in principle be applied to all pregnancies without the limitations by fetal gender or polymorphisms between the mother and fetus. The use of fetus- or disease-specific circulating RNA markers would greatly increase the number of markers that can be used for prenatal monitoring. With the recent advances in microarray technology, new placenta-derived plasma RNA markers could be rapidly identified. These newly identified placental transcripts were robustly detectable in maternal plasma and were pregnancy-specific. Remarkably, the relative concentrations of the placental mRNA in maternal plasma directly reflect the gene expression patterns in the placenta, an observation which suggests that placental gene expression level plays a predominant role in determining the placental mRNA concentrations in maternal plasma. Thus, fetal mRNA measurement in maternal plasma may be a useful tool for noninvasive prenatal placental gene expressing profiling.

Identification of fetal gender in maternal blood is a helpful tool in the prenatal diagnosis of haemophilia

Fetal DNA identification in maternal circulation has provided a new approach for non-invasive prenatal diagnosis. However, fetal DNA can persist in maternal blood long after the delivery, severely hampering this possibility. We addressed the issue of fetal DNA persistence in maternal blood. Thus, we investigated cell-free fetal DNA as a reliable approach in prenatal diagnosis of haemophilia. Forty non-pregnant women, who had had at least a male fetus, 29 control pregnant women, and 14 pregnant women, carriers of hemophilia A or B. The assessment of Y-chromosomal sequences was performed by analysing SRY and amelogenin genes using PCR-based techniques. A protocol consisting of double centrifugation at full speed followed by plasma filtration hampered the detection of Y chromosome-specific sequence in non-pregnant women. In 29 control pregnant women, blinded determination of fetal sex confirmed the specificity and sensitivity of the method applied. In 14 pregnant carriers of hemophilia, the investigation revealed a male fetus in nine pregnancies. Excluding the three cases in which a spontaneous miscarriage occurred, the sensitivity and specificity of fetal sex prediction by SRY and amelogenin gene analyses were both 100% as compared with the invasive approach and the fetal sex outcome at birth (six males and five females). Because of its high accuracy in prediction, fetal gender determination with cell-free fetal DNA in maternal plasma may be a useful tool in prenatal diagnosis of haemophilia allowing for the avoidance of invasive procedures for female fetuses.

Plasma β-globin DNA as a prognostic marker in chest pain patients

BACKGROUND

Acute coronary syndrome may involve cell death and the release of nucleic acids into the circulation. We thus investigated whether plasma DNA concentrations are increased and determined its prognostic significance in patients with ACS.

METHODS

Real-time polymerase chain reaction was used to quantitatively measure the beta-globin gene from blood samples taken from patients presenting to an emergency department with chest pain of probable cardiac cause.

RESULTS

Samples from 58 patients with chest pain, and from 21 age- and sex-matched healthy control subjects were analysed. Compared with the control group, median plasma DNA concentrations were increased 1.5-fold in patients with minor cardiac injury, were increased further in patients with STEA and STEMI, and were the highest in those patients who died within 2 years (P=0.0005; post-hoc Dunn's, P<0.05). Median plasma DNA concentrations were higher in patients who later developed heart failure (1060 vs. 500 kGE/l; P=0.0095); higher in patients who later reinfarcted (1000 vs. 530 kGE/l; P=0.0298); higher in patients who had a cardiac arrest in that admission (1350 vs. 525 kGE/l; P=0.04); and were higher in patients who were readmitted within 6 months of discharge (725 vs. 475 kGE/l; P=0.04).

CONCLUSION

Plasma DNA is a potential marker for post-ACS complications.

The struggle to detect circulating DNA

In various diseases, such as cancer, autoimmune disease, sepsis or myocardial infarction, elevated levels of circulating DNA can be measured. However, its predictive value is under debate. Circulating DNA in plasma is protein-bound (nucleosomal) DNA. Quantification of circulating DNA can be performed by real-time quantitative PCR or immunological methods such as ELISA. The diagnostic value of both methods can be impaired by inappropriate handling of the samples. Assessment of circulating DNA in patients admitted to the intensive care unit offers a tool for predicting morbidity and mortality.

Recent developments in fetal nucleic acids in maternal plasma: implications to noninvasive prenatal fetal blood group genotyping

The discovery of circulating cell-free fetal DNA in maternal plasma has opened up new possibilities for noninvasive prenatal diagnosis. Fetal DNA in maternal plasma has been used for the noninvasive prenatal determination of the RhD status of fetuses carried by RhD-negative pregnant women. In such analysis, the possible need of an internal control for the presence of detectable amounts of fetal DNA in a particular maternal plasma sample has been actively discussed. Recently, the development of a robust method for discriminating single nucleotide differences in plasma DNA using single allele base extension reaction (SABER) followed by matrix-assisted laser-desorption and ionization time-of-flight mass spectrometry (MALDI-TOF MS) has opened up the possibilities of using a panel of single nucleotide polymorphisms as such a positive control. A second approach is the recent successful development of fetal epigenetic markers which can be developed into universal fetal DNA markers. These developments hold promise to allow the eventual widespread utilization of maternal plasma DNA analysis for the noninvasive prenatal diagnosis of blood group mismatches between the mother and fetus.

Time Profile of Appearance and Disappearance of Circulating Placenta-Derived mRNA in Maternal Plasma

Background: Fetal RNA of placental origin has been detected in the plasma of pregnant women, but the timing of the first appearance and the detailed kinetics of postdelivery clearance of such circulating RNA have not been studied.

Methods: To address the timing of the first appearance of circulating placental RNA, we collected serial maternal blood samples from 47 women who had conceived by assisted reproductive procedures. To address the postdelivery clearance kinetics, we collected serial postdelivery blood samples from 6 pregnant women who had delivered by cesarean section. Placenta-derived transcripts were sought by real-time quantitative reverse transcription-PCR.

Results: The earliest gestational age at which human placental lactogen and human chorionic gonadotropin β-subunit mRNAs were detectable in a proportion of the pregnant women was the 4th week of gestation. The postdelivery study indicated that the median apparent half-life for the clearance of human placental lactogen mRNA was 14 min.

Conclusions: Placenta-derived mRNA can be found in maternal plasma from very early on in gestation, suggesting a possible role for early noninvasive prenatal diagnosis or monitoring. The rapid kinetics of circulating placental mRNA suggest that its plasma concentrations may be used to monitor recent physiologic or pathologic events.