SEVERE LIMB REDUCTION DEFECTS AFTER UTERINE LAVAGE AT 7–8 WEEKS' GESTATION

Altered Biomarkers in Trophoblast Cells Obtained Noninvasively Prior to Clinical Manifestation of Perinatal Disease

A contributing factor to poor placental perfusion, leading to intrauterine growth restriction and preeclampsia, is the failure of invading extravillous trophoblast (EVT) cells to remodel the maternal uterine arteries during the first and second trimesters of pregnancy. Noninvasive assessment of EVT cells in ongoing pregnancies is possible beginning three weeks after conception, using trophoblast retrieval and isolation from the cervix (TRIC). Seven proteins were semi-quantified by immunofluorescence microscopy in EVT cells obtained between gestational weeks 6 and 20 from pregnancies with normal outcomes (N = 29) and those with intrauterine growth restriction or preeclampsia (N = 12). Significant differences were measured in expression of PAPPA, FLT1, ENG, AFP, PGF, and LGALS14, but not LGALS13 or the lineage marker KRT7. These findings provide for the first time direct evidence of pathology-associated protein dysregulation in EVT cells during early placentation. The TRIC platform provides a novel approach to acquire molecular signatures of EVT cells that can be correlated with pregnancy outcome.

Transcervical retrieval of fetal cells in the practice of modern medicine: a review of the current literature and future direction

OBJECTIVE

To review published methods for transcervical collection of fetal cells and to assess the potential of this approach for application in prenatal diagnosis.

MAIN OUTCOME MEASURE(S)

Retrospective analysis of efforts at prenatal diagnosis with trophoblast cells shed into the lower uterine pole that accumulate within the cervical mucus at the level of the internal os.

RESULT(S)

Minimally invasive techniques that include cervical mucus aspiration, cervical swabbing, and cervical or intrauterine lavage can be used to retrieve trophoblast cells during the first trimester for diagnostic purposes, including for prenatal genetic analysis. Fetal cells have been identified in these specimens with success rates that vary from 40% to 90%. The disparity in reported success rates can be a function of gestational age, collection method, operator variability, detection sensitivity, or pregnancy status. Molecular approaches have been devised to determine fetal sex and identify aneuploidies. Antibody markers have proven useful to select trophoblast cells for genetic analysis and to demonstrate that the abundance of recoverable fetal cells diminishes in abnormal gestations, such as in ectopic pregnancy or blighted ovum.

CONCLUSION(S)

Transcervical collection of fetal cells offers several avenues for prenatal diagnosis that with further refinement could one day provide valuable information for the management of ongoing pregnancies.

The effect of hypoxia in development

There is increasing evidence that the oxygen supply to the human embryo in the first trimester is tightly controlled, suggesting that too much oxygen may interfere with development. The use of hypoxia probes in mammalian embryos during the organogenic period indicates that the embryo is normally in a state of partial hypoxia, and this may be essential to control cardiovascular development, perhaps under the control of hypoxia-inducible factor (HIF). A consequence of this state of partial hypoxia is that disturbances in the oxygen supply can more easily lead to a damaging degree of hypoxia. Experimental mammalian embryos show a surprising degree of resilience to hypoxia, with many organogenic stage embryos able to survive 30-60 min of anoxia. However, in some embryos this degree of hypoxia causes abnormal development, particularly transverse limb reduction defects. These abnormalities are preceded by hemorrhage/edema and tissue necrosis. Other parts of the embryo are also susceptible to this hypoxia-induced damage and include the genital tubercle, the developing nose, the tail, and the central nervous system. Other frequently observed defects in animal models of prenatal hypoxia include cleft lip, maxillary hypoplasia, and heart defects. Animal studies indicate that hypoxic episodes in the first trimester of human pregnancy could occur by temporary constriction of the uterine arteries. This could be a consequence of exposure to cocaine, misoprostol, or severe shock, and there is evidence that these exposures have resulted in hypoxia-related malformations in the human. Exposure to drugs that block the potassium current (IKr) can cause severe slowing and arrhythmia of the mammalian embryonic heart and consequently hypoxia in the embryo. These drugs are highly teratogenic in experimental animals. There is evidence that drugs with IKr blockade as a side effect, for example phenytoin, may cause birth defects in the human by causing periods of embryonic hypoxia. The strongest evidence of hypoxia causing birth defects in the human comes from studies of fetuses lacking hemoglobin (Hb) F. These fetuses are thought to be hypoxic from about the middle of the first trimester and show a range of birth defects, particularly transverse limb reduction defects.

Endocervical fetal trophoblast for prenatal genetic diagnosis

PURPOSE OF REVIEW

For over a decade, methods of first-trimester, noninvasive prenatal genetic diagnosis have been actively pursued by many investigators. Isolation of fetal trophoblast from endocervical specimens remains an attractive approach, given the greater numbers of fetal cells than in maternal blood and the better potential for fetal-cell identification based on markers specific for a single cell type (trophoblasts).

RECENT FINDINGS

Current studies demonstrate feasibility in identification and molecular analysis of fetal trophoblast cells for prenatal genetic testing. Sampling methods involving lavage, cytobrush, or aspiration of cervical specimens, however, have limitations in the recovery of trophoblasts.

SUMMARY

Clinical applications await further systematic studies to determine safety and accuracy in recovery.

Non-invasive early prenatal diagnosis using fluorescent in situ hybridization on transcervical cells: comparison of two different methods for retrieval

OBJECTIVE

We compared the efficiencies of uterine and endocervical lavage to retrieve fetal cells from first trimester pregnancies for further analysis with fluorescent in situ hybridization (FISH).

STUDY DESIGN

Transcervical cell (TCC) samples were collected at 7-10 weeks of gestations by uterine lavage (13 women) and by endocervical lavage (12 women) who were scheduled for volunteer termination of pregnancy. A sample of placenta was also obtained for cytogenetic analysis to confirm the sex or genotype in the end of the procedure. FISH was performed using probes for the chromosomes 18, X and Y in a three color hybridization protocol. The statistical analysis included chi(2)-analysis, and t-test.

RESULTS

Sufficient cells were obtained in 12 of the 13 (92.3%) in uterine lavage and 10 of the 12 (83.3%) in endocervical lavage group for FISH procedures for fetal sex prediction. The mean success rate of signal detection for FISH procedure was 91.7% (range 83-97%). Fetal sex was correctly predicted in 11 of 12 (91.6%) with uterine lavage and 8 of 10 (80.0%) in endocervical lavage and the difference was statistically insignificant.

CONCLUSION

This study demonstrated that there are available cells of fetal origin in the lower part of the uterus and these cells may be collected successfully as early as 7 weeks of the gestation. In addition, our results show that endocervical lavage method is as effective as uterine lavage. FISH has been successfully used to detect status of aneuploidy and sex of the fetus from TCC.

Transcervical sampling as a means of detection of fetal cells during the first trimester of pregnancy

OBJECTIVE

Our aim was to evaluate the detection of fetal cells from transcervical samples by means of fluorescence in situ hybridization analysis.

STUDY DESIGN

Forty-seven women undergoing first-trimester termination of pregnancy were recruited for transcervical sampling and 16 were recruited for endocervical mucus aspiration. Subjects were asked to assess the discomfort of the procedure. Fluorescence in situ hybridization analyses were performed with X and Y chromosome-specific probes. Results were compared with those of conventional chromosomal analysis.

RESULTS

Male signals (XY) were observed in 19 of 25 male fetuses (76%), and female signals (XX) were observed in 21 of 22 female fetuses. There was a significant variation between operators in cell retrieval. With mucus aspiration only 37.5% of male fetuses were correctly identified. The subjects did not find the procedure uncomfortable and reported that it was comparable to having a cervical smear taken.

CONCLUSIONS

Transcervical irrigation correctly identified the sex of 76% of male fetuses, but it still has considerable operator variability. This variability might be reduced by improved catheter design.

Fetal cells in cervical mucus and maternal blood

Research in developing effective and accurate methods for non-invasive prenatal diagnosis has focused on two main techniques: the retrieval of trophoblast cells from the cervix and the enrichment of fetal erythroblasts from the blood of pregnant women. The isolation of fetal cells by both approaches has permitted the identification of fetal aneuploidies by the use of fluorescence in-situ hybridization (FISH) with appropriate probes, as well as fetal single gene disorders by polymerase chain reaction (PCR). In the latter instance, it has been shown that in order to attain the high degree of specificity required for prenatal diagnosis, it is necessary to analyse single fetal cells isolated by micromanipulation. This practice has permitted the successful characterization of fetal rhesus status, haemoglobinopathies, Duchenné's muscular dystrophy and spinal muscular atrophy, amongst others.Further developments include investigations into whether the diagnostic potential of fetal cells retrieved by either method can be expanded by the possible culturing of such cells, as well as the possibility of performing successive rounds of FISH and PCR by the recycling of isolated fetal cells.A novel observation that our group has made is that the traffic of fetal cells is enhanced in pregnancies affected by the pregnancy related disorder, pre-eclampsia. Our subsequent investigations have shown that this elevation in fetal cell traffic may serve as an early marker for those pregnancies at risk for this disorder.A very recent exciting discovery has been that free extracellular fetal DNA can be detected in the plasma and serum of pregnant women, which may permit the rapid and accurate detection of uniquely fetal loci, such as the fetal rhesus D gene in rhesus D negative pregnant women.

Transcervical recovery of fetal cells from the lower uterine pole: reliability of recovery and histological/immunocytochemical analysis of recovered cell populations

The aim of this work was to isolate, enumerate and attempt the identification of fetal cells recovered from the lower uterine pole. Immediately before elective termination of pregnancy at 7-17 weeks gestation, samples were recovered by transcervical flushing of the lower uterine pole (n = 108) or transcervical aspiration of mucus from just above the internal os (n = 187), and their contents examined using histological, immunohistochemical and molecular techniques. Syncytiotrophoblasts were identified morphologically in 28 out of 89 (31%) and 50 out of 180 (28%) flushings and aspirates respectively (mean 29%). Immunocytochemistry with monoclonal antibodies (mAbs) recognizing trophoblast or epithelial cell antigens on a smaller number of samples (n = 69) identified putative placental cells in 13 out of 19 (68%) and 25 out of 50 (50%) flushings and aspirates respectively (mean 55%). These included groups of distinctive cells with a small, round, hyperchromatic nucleus, strongly reactive with mAbs PLAP, NDOG1 and FT1.41.1. Smaller groups of larger, amorphous cells, usually containing multiple large, pale staining nuclei, reactive with mAb 340 and to a lesser degree with mAb NDOG5 were also observed. Taking cellular morphology and immunophenotype into consideration, the smaller uninucleate cells were likely to be villous mesenchymal cells, while the larger cells were possibly degrading villous syncytiotrophoblast. There was no significant difference in the frequency of fetal cells obtained by the two recovery methods. Squamous or columnar epithelial cells, labelled strongly with antibodies to cytokeratins or human milk fat globule protein, were observed in 97% (29 out of 30) of aspirates. The use of cervagem in a small number of patients prior to termination of pregnancy did not appear to influence the subsequent recovery of placental cells. Y-specific DNA was detected by polymerase chain reaction (PCR) in 13 out of 26 (50%) flushings and (99 out of 154) 64% aspirates analysed (mean 62%). In-situ hybridization (ISH) revealed Y-specific targets in 40 out of 69 (60%) of aspirates analysed. A comparison of PCR data obtained from transcervical recovered samples and placental tissues showed a concordance of 80% (76 out of 95), with 10 false positives. Comparing the PCR data from tissues with data derived by ISH from 41 aspirates gave a concordance of 90% with two false positives. Although syncytiotrophoblasts were much more likely to be present in samples containing immunoreactive placental cells, the detection rates of fetal-derived DNA were similar regardless of the morphological and/or immunological presence of placental cells. We conclude that the transcervical recovery of fetal cells, while promising, requires considerable additional effort being expended in further research and development, particular in the sampling procedure.