Origin of mitotic cells of the chorionic villi in direct chromosome analysis

A prospective cytogenetic study of third-trimester placentae in small-for-date but otherwise normal newborns

Data in the literature suggest that confined placental mosaicism might be associated with intrauterine growth retardation. However, this association may be coincidental and due to bias of ascertainment. We therefore started a prospective study based on the cytogenetic evaluation of placentae derived from growth-retarded newborns. We further minimized possible bias by excluding those small-for-date infants displaying findings which already could explain intrauterine growth retardation (mothers who are smokers, multiple pregnancies, gestosis, dysmorphic infants). In a collection of 71 small-for-gestational age newborns, we did not see a single case of true confined placental mosaicism.

Nuclear and chromosomal replication patterns in chorionic villi cells by bromodeoxyuridine labelling and DNA flow cytometry

Cell kinetics of chorionic villi (CV) were studied by BrdUrd-incorporation detected by fluorescence-plus-Giemsa and BrdUrd-antibody techniques, and by DNA flow cytometry. Growth characteristics of long-term cultures of CV resembled fibroblasts with a total cell cycle time of 26 h, final S phase of 9 h, penultimate S phase of 16 h and G2/M phase of 3-4 h. Especially useful for a quick routine diagnostic approach, Ultroser RG, a commercially available serum supplement, significantly increased cell proliferation and stabilized cell cycle lengths to a total cell cycle time of 14 h, final S phase of 7 h, penultimate S phase of 6 h and G2/M phase of 4 h. Moreover, mitotic activity steadily increased in cultured CV, when studying six successive subculturings. This reflects adaptation to the culture conditions rather than an inherent response of cultured CV cells of increasing passage numbers. Native villi exposed to BrdUrd immediately after biopsy show lower rates of uptake than do aliquots after overnight incubation. As shown by BrdUrd-pulse labelling studies, more than 7 h are required to overcome the proposed 'biopsy stress'. This correlates with routine diagnostic techniques, in which many more metaphase cells are observed in short-term cultures than in direct preparations.

Proliferation kinetics in native chorionic villus cells

In accordance with observations by other groups direct CVS preparations reveal only a few mitoses, whereas semi-direct cultures (overnight incubation) give good results. By monitoring the BrdU uptake with an immunological method, a delay in the proliferation activity in native villi could be observed up to 7 h after biopsy.

Cell cycle studies in chorionic villi

We have studied the cell cycle of cells obtained from chorionic villi in direct and culture preparations by incorporation of the thymidine analogue BrdU to produce late-labelling or sister chromatid differentiation patterns. We have, therefore, been able to estimate the duration of the cell cycle and, more specifically, the length of some of its phases. While results for chorionic villus sample cells in culture resembled those obtained for fibroblasts, data for the spontaneously dividing trophoblastic cells in direct preparations were different. Villi exposed to BrdU immediately after sampling showed a slight delay in the incorporation of the analogue and a lower percentage of labelled cells compared to villi treated after an overnight incubation, probably due to a temporary effect of the sampling technique. Results from semi-direct protocols suggest that cells have a G2 of no more than 4 h, and a mid-S phase of 10-16 h. The G1 period is very variable. After 48 h incubation with BrdU, only 4% of cells reach their second generation, whereas this percentage increases up to 70% after 72 h, indicating that under these experimental conditions most cells have a cell cycle of approximately 36 h. The average number of sister chromatid exchanges was similar in both direct preparations and cultures: 5.2 +/- 2.1 SCE per cell.

Admixture of maternal metaphases in first trimester direct chromosome preparations?

The autoradiographic labelling of different cell types in chorionic villi and decidual tissue was investigated after [3H]-thymidine incorporation in vitro. Although the extent of labelling was found to be lower in decidual than in villus tissue the possibility that direct chromosome preparations may contain maternal metaphases should be considered. The need for careful selection of villi for direct cytogenetic analysis was stressed.

First trimester chorionic villi sampling and direct chromosome preparations

Chorionic villi sampling was performed on 52 patients prior to elective termination of their pregnancies. Villi were obtained in 42, and direct chromosome preparations were successful in 41 of them. The use of a mixture of 0.075 M potassium chloride and 1% sodium citrate in the ratio of 2:1 for hypotonic treatment and 40% acetic acid for cell dispersal yielded chromosomes with good morphology and G-bands.

Cytogenetic analysis of chorionic villi: a technical assessment

Eighty-five samples of chorionic villi from women undergoing prenatal diagnosis at 8 to 12 weeks' gestation were subjected to cytogenetic analysis. Samples were prepared by a direct technique that permits limited analysis within two hours and by a short-term culture technique that permits detailed structural analysis within one week. An adequate number of cell divisions for cytogenetic analysis was obtained from 96% of living fetuses. Using both the direct technique and short-term culture, satisfactory banded chromosomal preparations were made in 93% of cases. Eleven of 12 pregnancies (92%) shown by ultrasound to be dead shortly before sampling, had cytogenetic abnormalities. Further studies are needed to develop banding definition equivalent to that available on cultured amniocytes.

[Chorion biopsy--a new method of prenatal diagnosis]

Chorionic villi are derivates of the trophoectoderm and therefore have the same genetic constitution as the embryo. The recently developed techniques of chorionic villi sampling in the 9th to 11th week of pregnancy and the cytogenetic analysis of this material open a new field in the prenatal diagnosis of chromosomal aberrations. With this method, a result is obtained about 8 weeks earlier than with the classical procedures performed by amniocentesis. This offers major advantages to both patient and physician.

Chorionic villus sampling: cytogenetic experience in preliminary investigations and in 50 diagnostic cases

The results of preliminary cytogenetic investigations of chorionic villus sampling (CVS) and its diagnostic application in 50 cases are reported. Preliminary investigations included the effect of short delays between biopsy and processing, levels of mitotic activity related to variations in processing, the incidence of tetraploidy, correlation of the karyotype of the chorionic villi with that of the fetus, and the results of banding studies. A protocol was then designed for application to diagnostic CVS. The 50 diagnostic cases included 4 with male karyotypes which were terminated due to a family history of an X-linked disorder, 1 trisomy 21, 1 trisomy 18, the finding of 1 aberrant cell out of 50 in an otherwise normal analysis, a 45, XY, t (13;21) karyotype, 2 fragile X negative karyotypes and in one case the presence of mosaicism was detected in chorionic villi and subsequently not confirmed at amniocentesis. The karyotype on the chorionic villi was 46XY/47XY +3.

Chorionic villi sampling: clinical experience, immediate complications, and patient attitudes

To develop chorionic villi sampling as a procedure for prenatal diagnosis, a pilot study was undertaken to perfect the obstetric and laboratory techniques, to evaluate our success with the procedure in continuing pregnancies, and to assess the attitudes of potential users of the procedure. Women about to have elective first-trimester abortions for nongenetic reasons were enrolled in the first phase of the study. Of the patients with a positive pregnancy test, 12.4% were found to have a nonviable pregnancy on ultrasound examination. Samples adequate for cytogenetic analysis were obtained in 130 of the 155 remaining cases, and the success rate was 93% in the 100 most recent cases. Direct cytogenetic analysis was undertaken in those cases successfully sampled, and karyotypes could be prepared in 97%. Immediate complications occurred in 5% of the pregnancies. Eight women at risk of bearing a child with a genetic defect had diagnostic chorionic villi sampling. Cytogenetic analysis was performed successfully on all of them. One had an induced abortion following the procedure because of the fetal diagnosis (a male with a 50% risk of Duchenne's muscular dystrophy). The other pregnancies are continuing uneventfully at 22 to 35 weeks' gestation. Finally, from preliminary analysis of our survey of potential users it appears that women 35 years old or over would prefer chorionic villi sampling to amniocentesis if the risks of the sampling were known to be low.

A fetus with a chromosome 13 ring and placenta with chromosome 13 rod/ring mosaicism

A fetus was identified by prenatal cytogenetic diagnosis as having a karyotype 46,XY,r(13) (p11q13). Termination of the pregnancy yielded a severely malformed fetus. Fetal abnormalities included anencephaly, imperforate anus and urethral meatus, severe talipes, syndactyly, cardiac defects and other anomalies. Confirmatory studies on cultured placental villi cells indicated a second cell line, 46,XY, -13,+13qter leads to cen::13q13 leads to qter. This cell line was not detectable in cells derived from the fetus despite extensive studies. It seems likely that the two cell lines arose simultaneously with selection favouring the 46,XY,r(13) line. How the chromosome rearrangements may have arisen is discussed. We are unaware of other cases where a cell line identifiable by a chromosome abnormality appeared to be confined to placental tissue. However, studies on placental tissue may be helpful in understanding the origin of other unbalanced de novo rearrangements.

Efficient direct chromosome analyses and enzyme determinations from chorionic villi samples in the first trimester of pregnancy

Chorionic villi were obtained by an aspiration technique which proved to be the best of four alternative procedures. We report in detail the series of experiments which led to (1) successful, rapidly growing cell cultures practically free of maternal cell contamination (the use of hormone-supplemented Chang medium greatly increased the growth rate); (2) an efficient direct method to obtain high quality metaphases from the Langhans cells of the cytotrophoblast tissue and with which the fetal karyotype is defined within a few hours of chorionic villi sampling; and (3) successful testing for the activity of eight enzymes directly from the villi samples, thus showing that this material is suitable for a rapid, direct diagnosis of the related metabolic diseases.

Causes of chromosome anomalies suggested by cytogenetic epidemiology of induced abortions

Women who visited hospitals requesting induced abortions were asked about their obstetric and medical histories by attending physicians prior to the operation. The information was solely based on their reports at the interview. The period of coverage was nine weeks, comprising six weeks before and three weeks after the onset of the last menstruation. Both the occurrence of acute respiratory infectious diseases, which included the common cold, upper respiratory tract infection (U.R.T.I.), influenza, and pneumonia, and the use of analgesics and antipyretics were most frequently reported. Regardless of whether they had an acute respiratory illness, the women who took analgesics and antipyretics (including antihistamine, cough remedy, and nasal decongestant) had 13.8% (8/58) gross chromosome anomalies. The women without the treatment had 6.3% (71/1136) anomalies. The difference was statistically significant (P less than 0.05). Triploid formation was particularly related to drug consumption, thus there were 5.2% (3/58) in the treated group and 0.5% (6/1136) in the untreated group (P=0.0074). In contrast, trisomy was not considered to be related to drug consumption on account of 8.6% (5/58) and 4.1% (47/1136) in the corresponding groups (0.10 less than P less than 0.20). When the occurrence of trisomy was examined in connection with two variables, i.e., the presence of drug consumption and the age of mothers, association was not evident (X2 assoc. = 0.883, d.f. = 1 by Cochran's method). Besides these results, neither maternal X-irradiation nor irregularity of the menstrual period was found to be related to the frequency of chromosome anomalies in the progeny.