Complete hydatidiform moles combine maternal mitochondria with a paternal nuclear genome

Heterozygous/dispermic complete mole confers a significantly higher risk for post-molar gestational trophoblastic disease

Hydatidiform moles are classified at the genetic level as androgenetic complete mole and diandric-monogynic partial mole. Conflicting data exist whether heterozygous complete moles are more aggressive clinically than homozygous complete moles. We investigated clinical outcome in a large cohort of hydatidiform moles in Chinese patients with an emphasis on genotypical correlation with post-molar gestational trophoblastic disease. Consecutive products of conceptions undergoing DNA genotyping and p57 immunohistochemistry to rule out molar gestations were included from a 5-year period at Beijing Obstetrics and Gynecology Hospital. Patient demographics and clinical follow-up information were obtained. Post-molar gestational trophoblastic disease or gestational trophoblastic neoplasia was determined by the 2002 WHO/FIGO criteria. A total of 1245 products of conceptions were classified based on genotyping results into 219 complete moles, 250 partial moles, and 776 non-molar gestations. Among 219 complete moles, 186 were homozygous/monospermic and 33 were heterozygous/dispermic. Among 250 partial moles, 246 were triploid dispermic, 2 were triploid monospermic, and 2 were tetraploid heterozygous partial moles. Among 776 non-molar gestations, 644 were diploid without chromosomal aneuploidies detectable by STR genotyping and 132 had various genetic abnormalities including 122 cases of various trisomies, 2 triploid digynic-monoandric non-molar gestations, 7 cases of possible chromosomal monosomy or uniparental disomy. Successful follow-up was achieved in 165 complete moles: post-molar gestational trophoblastic disease developed in 11.6% (16/138 cases) of homozygous complete moles and 37.0% (10/27 cases) of heterozygous complete moles. The difference between the two groups was highly significant (p = 0.0009, chi-square). None of the 218 partial moles and 367 non-molar gestations developed post-molar gestational trophoblastic disease. In conclusion, heterozygous/dispermic complete moles are clinically more aggressive with a significantly higher risk for development of post-molar gestational trophoblastic disease compared with homozygous/monospermic complete moles. Therefore, precise genotyping classification of complete moles is important for clinical prognosis and patient management.

Complete hydatidiform moles are composed of paternal chromosomes and maternal mitochondria

Mitochondrial DNA (mtDNA) and genomic DNA are produced in separate subcellular compartments. Human mtDNA is transmitted via maternal transmission in general. Complete hydatidiform moles (CHMs) represent major trophoblastic diseases that are cytogenetically exceptional because the chromosomal genomic DNA is derived only from sperm cells, making them strikingly different from normal concepti. However, few reports have described the mtDNA-transmission pattern in hydatidiform moles. To evaluate mtDNA transmission in androgenetic CHMs, we compared the sequences of hypervariable regions in 16 trios sets of mtDNAs from maternal, paternal, and villous samples of androgenetic CHMs diagnosed by short tandem repeat-polymorphism analysis. All mtDNAs in androgenetic CHMs were maternally derived, in line with the general human inheritance pattern. Three maternal mtDNAs were heteroplasmic. The heterozygous status of maternal mtDNA was reflected in villous tissue, in which variants status was also heterozygous. CHMs are composed of paternal chromosomes and maternal mitochondria.

A prospective study of ultrasound screening for molar pregnancies in missed miscarriages

OBJECTIVE

To examine the relationship between ultrasound and histological features in the screening for molar changes in missed miscarriage.

METHODS

A prospective cohort study was conducted on all missed miscarriages, with features suspicious of molar pregnancy, on transvaginal ultrasound and/or on histological examination over a 5-year period. All cases of molar pregnancy diagnosed histologically were examined and cross-referenced with cases diagnosed on ultrasound and with the supplementary report from the regional referral center. When available, maternal serum beta-human chorionic gonadotropin (hCG) levels were recorded.

RESULTS

Fifty-one cases of suspected molar pregnancy were referred to the regional center for further histological opinion and follow-up, and five cases were subsequently excluded from the final analysis because of the diagnosis of hydropic abortion (HA). In 33 cases a molar pregnancy was suspected at the initial scan. Of these, 26 (78.8%) were confirmed on histology, resulting in a 56% detection rate using ultrasound alone. In 15 cases hCG results were available, of which nine were greater than two multiples of the median.

CONCLUSIONS

The diagnosis of both complete (CHM) and partial (PHM) hydatidiform moles in first-trimester miscarriages is difficult. hCG is significantly higher in both CHM and PHM and, in conjunction with transvaginal ultrasound, could provide the screening test required to enable clinicians to counsel women more confidently towards non-surgical methods of management of their miscarriage, where histopathological examination is not available.

Genomic imprinting in gestational trophoblastic disease--a review

The abnormal pregnancy hydatidiform mole (HM) can be classified as complete (CHM) or partial (PHM) on the basis of both morphology and genetic origin. PHM are diandric triploids while almost all CHM are androgenetic. Thus the characteristic trophoblastic hyperplasia seen in both CHM and PHM is usually associated with the presence of two paternal genomes. Very occasionally CHM may be diploid, but biparental, in origin. These rare BiCHM are found in patients with recurrent HM and appear to be associated with an autosomal recessive condition predisposing to molar pregnancies. Since they are pathologically indistinguishable from androgenetic CHM, BiCHM are also likely to result from defects in genomic imprinting. There is evidence that the gene mutated in this condition, provisionally mapped to 19q13.3-13.4, may be important in setting the maternal imprint in the ovum. Women with BiCHM have a much higher risk of recurrent HM than women with AnCHM and an appreciable risk of persistent trophoblastic disease. Investigation of these unusual BiCHM and isolation of the defective gene will lead to a greater understanding of the function of genomic imprinting in early development.

Histopathological diagnosis of partial and complete hydatidiform mole in the first trimester of pregnancy

The diagnosis of molar pregnancy is a continuing diagnostic problem for many practicing histopathologists who are required to examine specimens of products of conception, particularly since changes in gynecological management in recent years have resulted in uterine evacuation at earlier gestations. The aim of this review is to provide practical, up-to-date, diagnostically useful information regarding the histological diagnosis of molar disease in early pregnancy. Pathophysiological issues relevant to molar pregnancies, such as genetic abnormalities, will be briefly summarized, but nonhistopathological aspects of molar disease will not be covered in detail in this review.

Current understandings of the molecular genetics of gestational trophoblastic diseases

Gestational trophoblastic disease (GTD) is a heterogeneous group of diseases characterized by abnormally proliferating trophoblastic tissues. This includes partial and complete hydatidiform moles, invasive mole, choriocarcinoma and placental site trophoblastic tumour. Cytogenetic studies revealed that hydatidiform moles contain either solely (as in complete moles) or an excess (as in partial moles) of paternal contribution to the genome. Genomic imprinting is believed to play a pivotal role in the pathogenesis of hydatidiform moles. However its precise role and mechanism remains poorly understood. Hydatidiform mole carries a potential of malignant transformation. Similar to other human cancers, malignant transformation in gestational trophoblastic tumours is likely a multistep process and involves multiple genetic alterations including activation of oncogenes and inactivation of tumour suppressor genes. In addition, expression of telomerase activity, altered expression of cell--cell adhesion molecules and abnormal expression of matrix metalloproteinases have also been reported in GTD. These represent disruption of the delicate balance and regulation of cellular processes including proliferation, differentiation, apoptosis and invasion. The significance of these alterations in the pathogenesis and malignant transformation of gestational trophoblastic diseases is reviewed in this paper.

The homozygous complete hydatidiform mole: a unique resource for genome studies

The most frequent type of complete hydatidiform mole is a 46, XX homozygote formed by the fertilization of an empty ovum by a single haploid sperm that later duplicates its chromosomes to give a diploid tumor. The homozygous nature of these complete hydatidiform moles makes them unique resources for human genome studies. They can serve as homozygous controls in the development of single nucleotide polymorphism (SNP) markers and provide a way to obtain long-range haplotypes that are useful in population studies. The use of a homozygous control makes it possible to estimate the allele frequencies of the SNP markers in any population by sequencing pooled DNA samples. In this report, we present evidence of homozygosity of a complete hydatidiform mole using 20 diallelic markers distributed across the genome. Furthermore, its usefulness as a homozygous control in SNP development and as a resource for long-range haplotype determination is demonstrated using 11 newly discovered loci in the BRCA2 region on chromosome 13q12-q13.

Sad fetus syndrome--gestational trophoblastic disease concurrent with a living fetus or fetuses

The term gestational trophoblastic disease is used to indicate a group of both benign and malignant trophoblast, including molar degeneration of villi, hydatid mole, invasive mole and choriocarcinoma. This study shows a new classification of trophoblastic disease existing with a living fetus or fetuses. Benign hydatid mole is the initial stage of the disease continuum, whereas highly malignant choriocarcinoma is the final stage of this spectrum.

The immune system in disease: gestational trophoblastic tumours

Trophoblastic tumours form a spectrum of disease from the borderline malignancy of HM to highly aggressive choriocarcinoma. Their management requires the integration of the information derived from serial hCG estimations, the clinical history and pattern of spread of the disease, so that our understanding of the prognostic variables can be applied appropriately. This maximizes the patient's chances of complete remission from her disease with the minimum of toxicity. Given our knowledge of this group of diseases and an integrated approach to management, it should be uncommon for any woman to die from her trophoblastic tumour.

Kinetic analysis of 3 beta-hydroxysteroid dehydrogenase activity in microsomes from complete hydatidiform mole

Microsomes isolated from complete hydatidiform moles (CHM) were able to convert [3H]pregnenolone to [3H]progesterone which indicates the presence of 3 beta-hydroxysteroid dehydrogenase/isomerase (3 beta-HSD) activity. The kinetic parameters found (Km = 0.63 microM and Vmax = 1-3.05 nmol/min/mg of protein) were like those observed in microsomes from normal early placenta (NEP) of similar gestational age (herein) and term placenta suggesting that the enzymes from the three sources are kinetically similar. Testosterone, progesterone and estradiol in a dose range of 0.05-5 mumol/l inhibited differently the in vitro conversion of [3H]pregnenolone to [3H]progesterone in a dose-dependent manner. The steroid concentrations necessary to inhibit the conversion of pregnenolone to progesterone by 50% (ID50) in CHM were 0.1 microM for testosterone, 0.6 microM for progesterone and 3 microM for estradiol, whereas in NEP they were 2.5, 1 and 5 microM respectively. The Ki values calculated from these ID50 in CHM together with the reported levels of endogenous steroids indicate that the accumulation of testosterone and progesterone inside the molar vesicle could physiologically regulate the rate of further conversion of pregnenolone to progesterone. The present findings could provide an explanation for the low level of progesterone in patients with CHM in the second trimester of pregnancy which in turn may directly or indirectly affect the spontaneous expulsion of this aberrant tissue.

Gestational trophoblastic disease: what have we learned in the past decade?

Hydatidiform moles can be classified into two distinct entities: complete and partial. Complete moles are androgenetically derived, are characterized by a predominance of the 46,XX karyotype, and are associated with a significantly higher incidence of malignant sequelae than are partial moles. A subset of complete moles resulting from dispermy are heterozygous (46,XY) and appear to be associated with the greatest risk of malignancy. Free subunits of human chorionic gonadotropin, beta core fragments, and acidic variants of human chorionic gonadotropin can now be readily measured by radioimmunoassays, fluoroimmunoassays, or isoelectric focusing techniques. Determination of these markers can be of value not only in monitoring response to therapy, but also as prognostic indicators. A subgroup of patients, traditionally classified as "high risk" or poor prognosis, who show poor responses to conventional combination chemotherapy have recently been designated as "ultra-high-risk" patients. They require more complex chemotherapy and possibly surgery and radiotherapy to achieve remission. The development of chemotherapy over the past decade, including the introduction of etoposide and cisplatin into current protocols and the treatment of patients with advanced gestational trophoblastic disease, are considered in this review.

Mitochondrial encephalomyopathy with associated aminoacidopathy in a male sibship

We report two brothers with a previously undescribed type of mitochondrial encephalomyopathy and associated aminoacidopathy. Both have growth failure, progressive intellectual decline, deafness, neurologic dysfunction, exercise intolerance, lactic acidosis, and abnormal plasma and cerebrospinal fluid amino acid levels (elevated levels of alanine and low levels of threonine, methionine, citrulline, tryptophan, ornithine, arginine, and lysine). A muscle biopsy specimen taken from the younger, more severely affected brother showed abnormal mitochondrial morphology. Activities of the following enzymes in cultured fibroblasts from both boys were normal: pyruvate dehydrogenase, pyruvate carboxylase, phosphoenolpyruvate carboxykinase, cytochrome oxidase, reduced nicotinamide-adenine dinucleotide-cytochrome c reductase, and succinate cytochrome c reductase. Fibroblast mitochondria from the younger boy showed undetectable (less than 1% of control values) adenosine triphosphate synthesis with pyruvate and malate, whereas adenosine triphosphate synthesis with succinate was 70% of control values. These data indicate probably deficient activity of complex I of the electron transport chain. The boys' mother has progressive neurosensory hearing loss; their sister is clinically normal. Both mother and sister have many of the biochemical abnormalities found in the boys. It is possible, but not proved, that this disorder is inherited through maternal mitochondria.

Frequency of heterozygous complete hydatidiform moles, estimated by locus-specific minisatellite and Y chromosome-specific probes

Restriction fragment length polymorphisms identified with three locus-specific minisatellite probes and banding patterns with Y chromosome-specific probes have been examined in 39 cases of complete hydatidiform mole (CHM) and the parents. All 39 cases were shown to be androgenetic. Of the 39 cases, 8 were identified as heterozygous CHM using the minisatellite probes. Estimates for the total number of heterozygous CHM in the series ranged from 23%-29%, higher than previously reported. Of the eight identified heterozygous CHM, six had Y chromosome-specific sequences whereas two were female; this is not significantly different from the 2:1 ratio expected. The low frequency of 46,XX heterozygous CHM in the literature may reflect difficulties in distinguishing them from 46,XX homozygous CHM. Examination of RFLPs with a small panel of locus-specific minisatellite probes provides a powerful method of classifying hydatidiform mole, enabling the rare heterozygous 46,XX CHM to be accurately identified.

Genetically homozygous choriocarcinoma following pregnancy with hydatidiform mole

Genetic studies have been made in two cases of primary choriocarcinoma from patients in whom the antecedent pregnancy was a hydatidiform mole. Restriction fragment length polymorphisms of the DNA from the tumour, the patient and her partner were examined and in both cases the tumours were shown to be androgenetic in origin, having only paternal polymorphisms. While one tumour was shown to be heterozygous, two different paternal alleles being demonstrated with some probes, the other tumour was shown to be homozygous for all informative polymorphisms examined. Thus choriocarcinoma can follow complete hydatidiform mole which may be either heterozygous or homozygous.

Genetic studies in hydatidiform mole with clinical correlations

In an elective study of 163 hydatidiform moles 38 were classified as partial mole (PHM) and 125 as complete mole (CHM) on the basis of pathology. Genetic studies showed the PHM to be triploid with one maternal and two paternal chromosome sets. In all cases of PHM the molar pregnancy resolved spontaneously after evacuation. On the basis of genetic studies CHM which were diploid could be subdivided into two entities: homozygous androgenetic CHMs that were 46,XX, and heterozygous CHMs which were androgenetic and usually 46,XY. In informative cases in this series the frequency of heterozygous CHM was 10 per cent. Twenty-two (17.6 per cent) of all the patients with CHM required subsequent chemotherapy for post-mole trophoblastic tumour. Where patients with CHM could be classified as having homozygous or heterozygous CHM the requirement for treatment (17.8 per cent and 25 per cent, respectively) was not found to be significantly different in the two groups.