Genetically different cell subpopulations in hydatidiform moles. A study of three cases by RFLP, flow cytometric, cytogenetic, HLA, and morphologic analyses

Triploidy--Observations in 154 Diandric Cases

Hydatidiform moles (HMs) are abnormal human pregnancies with vesicular chorionic villi, imposing two clinical challenges; miscarriage and a risk of gestational trophoblastic neoplasia (GTN). The parental type of most HMs are either diandric diploid (PP) or diandric triploid (PPM). We consecutively collected 154 triploid or near-triploid samples from conceptuses with vesicular chorionic villi. We used analysis of DNA markers and/or methylation sensitive-MLPA and collected data from registries and patients records. We performed whole genome SNP analysis of one case of twinning (PP+PM).In all 154 triploids or near-triploids we found two different paternal contributions to the genome (P1P2M). The ratios between the sex chromosomal constitutions XXX, XXY, and XYY were 5.7: 6.9: 1.0. No cases of GTN were observed. Our results corroborate that all triploid human conceptuses with vesicular chorionic villi have the parental type P1P2M. The sex chromosomal ratios suggest approximately equal frequencies of meiosis I and meiosis II errors with selection against the XYY conceptuses or a combination of dispermy, non-disjunction in meiosis I and meiosis II and selection against XYY conceptuses. Although single cases of GTN after a triploid HM have been reported, the results of this study combined with data from previous prospective studies estimate the risk of GTN after a triploid mole to 0% (95% CI: 0–1,4%).

Genetic analysis of hydatidiform moles utilizing the oligonucleotide-DNA typing of the HLA-DRB gene

The genetic origin of hydatidiform moles was analysed utilizing HLA-DNA typing. Using HLA-DR type-specific oligonucleotide probes, the DRB types of seven moles were determined and compared with the parental DRB types to determine the paternal and/or maternal origin of the moles. In four cases, the molar tissues showed single DRB types of paternal origin, although in one, the molar DRB type was also possessed by the mother. These four moles were, therefore, considered to be androgenetic in origin. Chromosomal karyotyping was carried out for three of these cases and confirmed the DR-DNA typing results. Two moles demonstrated a DRB-type triplet, which strongly suggested triploidy. Although one mole showed a heterozygous DRB type, karyotyping indicated triploidy (69, XXX) and suggested that this mole was caused by dispermy-fertilization, in which both of the sperms had the same DRB type. Although the majority (about 80%) of partial hydatidiform moles have been reported to be triploid as a result of dispermy, four of the moles analysed in this study (cases 1, 2, 3 and 4), diagnosed as partial macroscopically and/or histopathologically, were found to be androgenetic in origin using karyotyping and DR-DNA typing. Therefore, HLA-DR DNA typing, combined in some cases with karyotyping, provides an accurate method for diagnosing androgenesis and triploidy in complete and partial hydatidiform moles.

DNA cytometric and interphase cytogenetic analyses of paraffin-embedded hydatidiform moles and hydropic abortions

The combined application of DNA cytometric and interphase cytogenetic analyses was used to find objective criteria for the differential diagnosis of complete hydatidiform mole, partial hydatidiform mole and hydropic abortion. DNA ploidy and G0/G1 exceeding rates were determined using image and flow cytometric analyses on paraffin-embedded tissues of 166 cases: 71 cases of complete mole, 20 cases of partial mole, and 75 cases of abortions. To determine the existence and histological distribution of cell subpopulations with numerical chromosome aberrations, interphase cytogenetic analysis using probes specific for chromosomes 1, X, and Y was applied to paraffin tissue sections of 23 cases: 12 cases of complete mole, 3 cases of partial mole, and 8 cases of abortions. In contrast to previously reported findings that complete moles are diploid, the results of this study showed that complete moles are DNA-polyploid (96 per cent), with high G0/G1 exceeding rates and a high frequency of numerical chromosomal aberrations in the trophoblast hyperplasia. The majority of the partial moles were DNA-triploid (55 per cent). This study, however, also showed the presence of DNA-polyploid partial moles (30 per cent). Abortions were DNA-diploid (60 per cent) or DNA-triploid (39 per cent). DNA cytometric analysis, especially image DNA cytometric analysis with determination of the G0/G1 exceeding rate, and interphase cytogenetic analysis provide objective measurements which are contributory in the differential diagnosis between complete mole, partial mole, and hydropic abortion.

Genetic analysis of repeated, biparental, diploid, hydatidiform moles

A woman presented with five consecutive pregnancies displaying molar morphology. In the fifth pregnancy, a non-malformed, liveborn infant was delivered. Genetic analyses (RFLP analysis, cytogenetics, flow cytometry) were performed in pregnancies II-V. It was demonstrated that these pregnancies originated in separate conceptions, all conceptuses were diploid, and all had maternally as well as paternally derived genetic markers. By cytogenetic analysis, aberrant heteromorphisms were noted; no other abnormalities were observed in chromosome structure or in DNA sequence. Many different causes for the abnormal development can be envisaged, environmental as well as genetic. To conform to current ideas of molar pathogenesis, it is suggested that the present conceptuses might have arisen from imbalances in imprinted genomic regions. This could be a consequence of uniparental disomy in critical regions generated by somatic crossing over. Alternatively, it could be caused by a malfunction in the generation or maintenance of imprinting.

Partial hydatidiform moles have impaired differentiated function (human chorionic gonadotropin and human placental lactogen secretion) in response to epidermal growth factor and 8-bromo-cyclic adenosine monophosphate

OBJECTIVE

The null hypothesis is that partial hydatidiform moles have normal differentiated function (human chorionic gonadotropin and human placental lactogen secretion) in response to epidermal growth factor and 8-bromo-cyclic adenosine monophosphate.

STUDY DESIGN

Two complete moles, 10 partial hydatidiform moles, and 19 normal first-trimester placentas in monolayer culture were exposed to 10 ng/ml epidermal growth factor, 1 mmol/L 8-bromo-cyclic adenosine monophosphate plus 1 mmol/L theophylline, or control. Human chorionic gonadotropin and human placental lactogen secretion was measured. Frequency of response to stimuli was compared by chi 2 analysis, and hormone secretion was compared by analysis of variance.

RESULTS

Partial moles demonstrated reduced frequencies of response of human chorionic gonadotropin and human placental lactogen to epidermal growth factor (partial moles 2/8 and 2/8, respectively; normal placentas 16/19 and 7/18, respectively; p less than 0.025) and of human chorionic gonadotropin to 8-bromo-cyclic adenosine monophosphate (partial moles 3/5, normal placentas 13/16; p less than 0.005).

CONCLUSION

Partial hydatidiform moles demonstrate impaired human chorionic gonadotropin and human placental lactogen secretory responsiveness to epidermal growth factor and cyclic nucleotides in comparison with normal first-trimester trophoblast.

Interphase cytogenetics in paraffin sections of routinely processed hydatidiform moles and hydropic abortions

The differential diagnosis of complete (CM) and partial (PM) hydatidiform moles and hydropic abortions (HA) can be difficult when based on histology alone. Therefore, a more objective approach of chromosome ploidy analysis as detected by in situ hybridization (ISH) was performed on 6 microns paraffin sections of seven cases, originally classified as three CM, two PM, and two HA with a histologic pattern suggestive of triploidy. Probes for repetitive DNA targets in the (peri)centromeric region of chromosomes 1 and X and in the q arm of chromosome Y were used to determine chromosome ploidy and sex chromosome composition. The findings in the three CM were consistent with diploidy: two copies of chromosomes 1 and X and none of chromosome Y. In the two HA with a histologic pattern suggestive of triploidy, three copies of chromosomes 1 and X and none of chromosome Y confirmed triploidy. Two cases originally classified as PM both appeared to have two copies of chromosome 1 with an XX pattern in one case and an XY pattern in the other case, which is consistent with diploidy instead of triploidy. After reviewing, both cases most likely represented CM. We conclude that interphase cytogenetics by ISH on paraffin sections of hydatidiform moles and hydropic abortions enables chromosome ploidy analysis with preservation of histological context.(ABSTRACT TRUNCATED AT 250 WORDS)

Current topic: trophoblastic pathology

Selected topics in trophoblastic pathology which are arousing current interest are briefly reviewed. These include the concept of villitis as a non-specific immunological lesion, changing views on the distinction between partial and complete hydatidiform mole, a reconsideration of the role of inadequate placentation in pregnancy hypertension and in spontaneous abortion, the significance of confined placental mosaicism and the importance of infection and defective collagen synthesis in premature rupture of the membranes.

Molecular genetic analysis of complete hydatidiform moles

Complete hydatidiform moles (CHM) are the most common form of gestational trophoblastic disease and a frequent antecedent to choriocarcinoma. Cytogenetic investigations into the origin of these tumors have shown that they can arise by virtue of unusual fertilization events. In this study we used molecular genetic "fingerprinting" methods to examine the genome of 22 consecutive CHM in order to determine their derivation. We found that 60% contained alleles consistent with a completely homozygous androgenic origin. The remaining 40% were heterozygous for marker alleles; half of these were completely androgenic in origin. The other half of these heterozygous CHM contained alleles from the maternal genome, indicating a biparental contribution. These findings suggest that the pathogenesis of CHM is more heterogenous than previously suspected, and can arise from biparental fertilization events. In addition, we found that mutations occur frequently at many loci in these tumors, which may reflect a generalized genetic instability perhaps related to subsequent malignant change. Thus, molecular genetic analysis of CHM provides new insights into the genesis of CHM and will be a powerful method for understanding their clinical biology.