Benefits of placental biopsies for rapid karyotyping in the second and third trimesters (late chorionic villus sampling) in high-risk pregnancies

Assessing hypoxic damage to placental trophoblasts by measuring membrane viscosity of extracellular vesicles

INTRODUCTION

As highly sophisticated intercellular communication vehicles in biological systems, extracellular vesicles (EVs) have been investigated as both promising liquid biopsy-based disease biomarkers and drug delivery carriers. Despite tremendous progress in understanding their biological and physiological functions, mechanical characterization of these nanoscale entities remains challenging due to the limited availability of proper techniques. Especially, whether damage to parental cells can be reflected by the mechanical properties of their EVs remains unknown.

METHODS

In this study, we characterized membrane viscosities of different types of EVs collected from primary human trophoblasts (PHTs), including apoptotic bodies, microvesicles and small extracellular vesicles, using fluorescence lifetime imaging microscopy (FLIM). The biochemical origin of EV membrane viscosity was examined by analyzing their phospholipid composition, using mass spectrometry.

RESULTS

We found that different EV types derived from the same cell type exhibit different membrane viscosities. The measured membrane viscosity values are well supported by the lipidomic analysis of the phospholipid compositions. We further demonstrate that the membrane viscosity of microvesicles can faithfully reveal hypoxic injury of the human trophoblasts. More specifically, the membrane of PHT microvesicles released under hypoxic condition is less viscous than its counterpart under standard culture condition, which is supported by the reduction in the phosphatidylethanolamine-to-phosphatidylcholine ratio in PHT microvesicles.

DISCUSSION

Our study suggests that biophysical properties of released trophoblastic microvesicles can reflect cell health. Characterizing EV's membrane viscosity may pave the way for the development of new EV-based clinical applications.

Outcome of fetal exomphalos diagnosed at 11-14 weeks of gestation

OBJECTIVE

To determine whether sonographic findings in cases of exomphalos detected at the 11-14-week scan can be used to guide pregnancy management.

METHODS

Retrospective study of cases of exomphalos identified from the Fetal Medicine Unit database, University College London Hospitals between January 1998 and January 2010. Pregnancy and neonatal data were ascertained from maternal and neonatal records. Fetal exomphalos was categorized into three groups: exomphalos associated with other major structural malformation(s), isolated exomphalos with increased nuchal translucency (NT) and isolated exomphalos with normal NT.

RESULTS

A total of 98 cases of exomphalos were identified, of which 45 (45.9%) were associated with other major structural malformation(s), identified antenatally. Isolated exomphalos was found with increased NT in 22 cases (22.4%) and with normal NT in 31 cases (31.6%). Of 80 (81.6%) fetuses that were karyotyped, 43 (53.8%) had a chromosomal abnormality; the most common aneuploidy was trisomy 18 (n = 31; 72.1%). Where exomphalos was associated with other major structural abnormalities, or was isolated with increased NT, the incidence of aneuploidy was high, at 78.9% and 72.2%, respectively. Cases of isolated exomphalos with normal NT were all euploid. In 21 cases (21.4%), exomphalos resolved later in pregnancy and none had apparent abnormalities at birth; isolated exomphalos persisted in only three neonates (3.1%).

CONCLUSIONS

The finding of a major structural abnormality or of increased NT in association with exomphalos in the first trimester implies a high risk of aneuploidy. Parents can be reassured that fetuses with isolated exomphalos and normal NT are likely to be euploid.

The use of needle biopsy for assessment of placental gene expression

OBJECTIVE

The purpose of this study was to test the hypothesis that placental samples that are obtained by needle aspiration ex vivo are useful for the determination of villus gene expression.

STUDY DESIGN

Placental biopsy was performed with a spinal needle after uncomplicated deliveries. Villi were inspected microscopically, and RNA was extracted and analyzed with capillary electrophoresis. Gene expression was determined with quantitative polymerase chain reaction.

RESULTS

We obtained more placental villous fragments per aspiration using a 20-gauge needle (5.2 +/- 1.8 fragments) than with a 22-gauge needle (3.3 +/- 1.6 fragments; P < .01). RNA quality was adequate, based on the 28S and 18S recombinant RNA bands, with a mean 260/280 ratio of 1.88. The amount of extracted RNA correlated with the number of villous fragments per aspirate. Importantly, the expression of NDRG1 and hPL, both markedly altered in hypoxia, was consistent between villi that were obtained by either needle or standard biopsy.

CONCLUSION

Placental samples that are obtained by ex vivo needle aspiration are useful for the extraction of RNA and for the determination of villous gene expression.

Fluorescence in situ hybridization of chorionic interphase cells for prenatal screening of Down syndrome

OBJECTIVE

Our purpose was to determine the usefulness and reliability of fluorescence in situ hybridization on interphase chorionic villi cells in the prenatal diagnosis of Down syndrome.

METHODS

A total of 336 samples of chorionic villi were analysed by direct chromosome preparation and FISH with a DNA probe specific to chromosome 21. The samples were obtained as part of the routine obstetric investigation and management.

RESULTS

The sampling and direct karyotyping was successful in all cases. At least 50 cells were valuable by FISH in 331 of 336 samples. Both methods showed Down syndrome in 12 cases. The follow-up investigations showed that there was no false-negative or false-positive result following these procedures.

CONCLUSION

Based on these results and the fact that it is possible to analyse by interphase FISH at least ten times more cells than by conventional cytogenetic methods, and these cells originate from different tissues of chorionic villi, it is concluded that FISH increases the reliability of the diagnosis. Nevertheless, more data are needed for correct statistical analysis. Since this method is cheaper and gives diagnosis earlier than cell culture, the combination of direct chromosome preparation and FISH on chorionic villi is offered for prenatal Down syndrome screening.

Transabdominal chorionic villus sampling in the second and third trimesters of high-risk pregnancies

Late chorionic villus sampling (placental biopsy) under ultrasound guidance was carried out in 800 (80 per cent) cases in the second trimester and 200 (20 per cent) cases in the third trimester of pregnancy. Out of 1000 placental biopsies, 250 (25 per cent) were performed because of suspicious ultrasonographic findings. Colour Doppler was used to investigate the uteroplacental and fetal vessels in 300 (30 per cent) pregnancies before and after late chorionic villus sampling (CVS). In the same group, mean serum alpha-fetoprotein (AFP) levels increased after sampling in 20 (6.7 per cent) patients. In 20 patients (2 per cent), complications between sampling and delivery were found. A placental haematoma measuring 0.5-1 ml was seen at the sampling site in 4 (0.4 per cent) patients in the second trimester of pregnancy and in 3 (0.3 per cent) in the third trimester. Two (0.2 per cent) demonstrated fever, but there were no instances of chorioamnionitis. There were only three (0.3 per cent) spontaneous abortions 4-6 weeks after late CVS. However, there was no correlation between AFP elevation, placental haematoma, Doppler measurements, and spontaneous abortion. Cytogenetic findings were obtained in 990 (99 per cent) of 1000 placental samplings. We found 60 (6.0 per cent) chromosomal abnormalities. In the group with suspicious ultrasonic findings (250 cases), we found significant oligohydramnios in 125 (50 per cent) and significant polyhydramnios in 60 (24 per cent), and 45 (18 per cent) had chromosomal abnormalities. Among the 60 patients with chromosomal abnormalities, ultrasonographic findings in 10 (16.7 per cent) were detected after the 20th week of pregnancy. There were no significant differences in mean pulsatility index (PI) in the uteroplacental and fetal vessels before and after late CVS. Preliminary data from five trisomic fetuses (three trisomy 21 and two trisomy 18) showed abnormally increased umbilical PI and abnormally decreased middle cerebral artery PI.

Prenatal diagnosis by transabdominal chorionic villus sampling in the second and third trimesters

From October 1989 through December 1993, 124 pregnant women (114 in the second trimester and 10 in the third trimester) underwent transabdominal chorionic villus sampling (CVS) for prenatal molecular or cytogenetic diagnosis. The mean gestational age was 18.2 weeks. Indications for CVS comprised single gene disease (72%), fetal anomalies detected by ultrasound (17%), advanced maternal age (6%), and previous siblings with chromosomal aberration (5%). Among the 89 fetuses at risk for single gene disease, 20 were diagnosed as affected by DNA analysis. Among the 35 fetuses at risk for chromosomal anomaly, 4 had trisomy, 3 had a 45,XO karyotype and 2 had a structural chromosomal abnormality. The miscarriage rate was 1.8% (2/114) and the spontaneous preterm birth rate was 2.4% (3/124). No maternal or other fetal complications occurred. This study suggested that second- and third trimester CVS is a safe and useful method for prenatal diagnosis.

Six years' experience with rapid karyotyping in prenatal diagnosis: correlations between phenotype detected by ultrasound and fetal karyotype

From September 1985 to March 1992, 804 amniotic fluid samples from 64 different diagnostic centres of the Federal Republic of Germany were sent to our laboratory exclusively for rapid karyotyping. The average time needed for notification of the analysed karyotype was 4.65 days when the 'pipette method' was used for chromosome harvesting and 5.97 days when the 'in situ' technique was used. The overall incidence of chromosome aberrations was 15.3 per cent. Data are presented about the likelihood of abnormal ultrasound findings being caused by chromosome aberrations. These findings include polyhydramnios, oligohydramnios, growth retardation, fetal effusions, neural tube defects, craniofacial defects, heart defects, gastroschisis and omphalocele, gastrointestinal tract defects, urinogenital defects, and limb defects. In future, such data need to contain larger numbers of cases for each week of gestation. This will improve the risk evaluation for each case with abnormal ultrasound findings, which should lead to better management during pregnancy, delivery, and postnatal care for those who require rapid karyotyping.

Rapid karyotyping in prenatal diagnosis: a comparative study of the 'pipette method' and the 'in situ' technique for chromosome harvesting

Rapid karyotyping in the second and third trimesters has important implications for the management of pregnancies at risk. From September 1985 to March 1992, 735 amniotic fluid samples sent to our laboratory for rapid karyotyping from 64 different diagnostic centres of the Federal Republic of Germany were included in a comparative study on harvesting for chromosome analysis using the 'pipette method' or the 'in situ' technique. The average time between preparation of the amniotic fluid and verbal notification of the analysed karyotype was 5.41 days. The 'pipette method' needed on average 4.65 days, and the 'in situ' technique 5.97 days. In comparison with other more invasive techniques available for rapid karyotyping such as cordocentesis and placental biopsy, amniocentesis and subsequent chromosome harvesting using the 'pipette method' and/or the 'in situ' technique proved very useful and efficient. The overall incidence of chromosome aberrations was 15.3 per cent. The high rate of structural chromosome aberrations and uncommon aneuploidies found in our investigation (12 per cent) indicates that for rapid karyotyping in the second and third trimesters, conventional cytogenetic techniques cannot be replaced by faster techniques based on fluorescent in situ hybridization on interphase cells in the near future.

Transabdominal chorionic villus sampling in the second and third trimesters of pregnancy: chromosome quality, reporting time, and feto-maternal bleeding

Transabdominal chorionic villus sampling (TA-CVS) was performed in 210 pregnancies from 13 to 38 weeks using a double-needle technique. The sampling success was comparable to first-trimester TA-CVS and the diagnostic success rate was 98.2 per cent for the short-term technique and 99.3 per cent for cultured villi. Two fetuses could not be karyotyped. We found the chromosome quality to be similar to that in the first trimester, comparing the number of G-bands and other chromosome attributes. There were no unintended losses in a group (n = 142) with no sonographic abnormality, except for one death in utero at 38 weeks, 20 weeks after sampling. Chromosomal aberrations were seen in 19 per cent of cases with abnormal sonograms (n = 58). One cases of a discordant karyotype was found (false-negative prediction of Down's syndrome by the short-term preparation). There were no cases of fetal demise due to feto-maternal bleeding. It is suggested that double-needle TA-CVS in advanced pregnancies combines the advantages of rapid karyotyping of chromosomes of good quality and low risk for the fetus, and seems to be easier to practise and is probably safer than cordocentesis.

Early transabdominal chorionic villus sampling in couples at high genetic risk

OBJECTIVE

The purpose of the study was to evaluate the feasibility and safety of transabdominal chorionic villus sampling before 9 weeks' gestation.

STUDY DESIGN

Two hundred pregnancies at risk for beta-thalassemia (n = 198) or Duchenne muscular dystrophy (n = 2) underwent transabdominal CVS at 6 through 8 weeks. Sampling success and fetal loss are expressed in percentages.

RESULTS

Sampling was successful in all cases (100%). Forty-eight fetuses were affected by beta-thalassemia and one by Duchenne muscular dystrophy. The percentage of fetal loss, expressed as a proportion of continuing pregnancies, was 4.0%. All women (n = 144) have been delivered, and no misdiagnoses have occurred. We observed one anencephalus and one mild limb defect consisting of absence of distal phalanges of index and little fingers of both hands and distal phalanges of both little toes.

CONCLUSION

Transabdominal CVS before 9 weeks is a reliable and relatively safe method for prenatal diagnosis in patients at high risk for genetic diseases. However, further studies are necessary to assess the risk to the fetus.

Placental biopsy in the third trimester of pregnancy

Forty-two women with abnormal ultrasound findings after 27 weeks' gestation underwent a placental biopsy. In 39 cases, a karyotype was obtained from a direct preparation within 48 h, five abnormal karyotypes being detected (four trisomies and a triploidy). One confirmed placental mosaic was also detected. In one case, a small terminal deletion of chromosome 7 was not detected at the time due to the quality of the preparation. A karyotype can be obtained from a direct preparation in the third trimester in over 90 per cent of cases, the quality of the preparation allowing the reliable detection of abnormalities of chromosome number. We believe that this technique may be usefully, reliably, and safely employed in the third trimester of pregnancy by those with an interest in antenatal ultrasound diagnosis who do not have immediate access to a cytogenetics laboratory and who feel that cordocentesis is inappropriate for their situation.

Mosaicism and accuracy of prenatal cytogenetic diagnoses after chorionic villus sampling and placental biopsies

Discrepant chromosome findings in placenta and fetus (false negative and false positive) after chorionic villus sampling (CVS) are mainly due to confined mosaicism. Non-mosaic normal or abnormal chromosome counts after direct preparation and culture nearly always correctly reflect the fetal chromosome constitution. False-negative results have almost exclusively been restricted to cytotrophoblast cells not representing a fetal chromosome abnormality. Diagnosis of placental mosaicism definitely requires an adequate follow-up by amniocentesis, fetal blood sampling, or sonography before a pregnancy is terminated. When direct preparations and cultured cells are used for cytogenetic diagnoses and placental mosaicism is not taken as proof for a chromosomal abnormality in the fetus, CVS is an accurate diagnostic tool.

'False-negative' and 'false-positive' prenatal cytogenetic results due to 'true' mosaicism

A 37-year-old gravida was referred for CVS because of advanced maternal age. A trisomy 21 was present in all cells after short-term incubation (direct processing (DP)) and long-term culture. According to our policy, a retap was offered for confirmation of the result during the legally required 3-day waiting period between communication of the result and termination of pregnancy. Unexpectedly all cells after DP showed a normal male chromosome complement. Further investigations revealed mosaicism in trophoblast tissue and a normal karyotype in amniotic fluid cells and fetal blood (50 mitoses each). The parents elected to continue the pregnancy after extensive ultrasound examinations did not show suspicious findings. After the birth of a healthy child, cell cultures from ten different placental sites confirmed mosaicism. Four out of 100 mitoses from a lymphocyte culture showed an additional chromosome 21. The child had no dysmorphic features and the development was normal at the age of 10 weeks. This case demonstrates the restricted validity of prenatal cytogenetic analysis in the presence of true fetal mosaicism. It also stresses the benefit of our policy to offer a retap in cases with abnormal cytogenetic results prior to termination of pregnancy which is considered unnecessary by many cytogeneticists.

Transabdominal placental biopsy in the second and third trimester of pregnancy

Transabdominal placental biopsy under ultrasound guidance was carried out in 260 cases in the second trimester and 50 cases in the third trimester of pregnancy. Placental tissue was aspirated using an 18 or 20 gauge needle. In a total of 310 placental biopsies in the second and third trimester, 100 were performed because of suspicious ultrasonographic findings. Placental biopsy is simple in the presence of severe oligohydramnios where fetal blood sampling is usually more difficult. Oligohydramnios and polyhydramnios were the ultrasonographic findings in 50% of cases and were found to be associated with 30% of abnormal chromosomal findings. There was one (0.3%) abortion within two weeks following placental biopsy. Placental biopsy did not affect the outcome of the pregnancy.