Developmentally arrested oviduct: a structural and functional defect in mice following prenatal exposure to diethylstilbestrol

New frontiers of developmental endocrinology opened by researchers connecting irreversible effects of sex hormones on developing organs

In the early 1960's, at Professor Bern's laboratory, University of California, Berkeley) in the US, Takasugi discovered ovary-independent, persistent vaginal changes in mice exposed neonatally to estrogen, which resulted in vaginal cancer later in life. Reproductive abnormalities in rodents were reported as a result of perinatal exposure to various estrogenic chemicals. Ten years later, vaginal cancers were reported in young women exposed in utero to the synthetic estrogen diethylstilbestrol (DES) and this has been called the "DES syndrome". The developing organism is particularly sensitive to developmental exposure to estrogens inducing long-term changes in various organs including the reproductive organs. The molecular mechanism underlying the persistent vaginal changes induced by perinatal estrogen exposure was partly demonstrated. Persistent phosphorylation and sustained expression of EGF-like growth factors, lead to estrogen receptor α (ESR1) activation, and then persistent vaginal epithelial cell proliferation. Agents which are weakly estrogenic by postnatal criteria may have major developmental effects, especially during a critical perinatal period. The present review outlines various studies conducted by four generations of investigators all under the influence of Prof. Bern. The studies include reports of persistent changes induced by neonatal androgen exposure, analyses of estrogen responsive genes, factors determining epithelial differentiation in the Müllerian duct, ESR and growth factor signaling, and polyovular follicles in mammals. This review is then expanded to the studies on the effects of environmental estrogens on wildlife and endocrine disruption in Daphnids.

Development of the human female reproductive tract

Development of the human female reproductive tract is reviewed from the ambisexual stage to advanced development of the uterine tube, uterine corpus, uterine cervix and vagina at 22 weeks. Historically this topic has been under-represented in the literature, and for the most part is based upon hematoxylin and eosin stained sections. Recent immunohistochemical studies for PAX2 (reactive with Müllerian epithelium) and FOXA1 (reactive with urogenital sinus epithelium and its known pelvic derivatives) shed light on an age-old debate on the derivation of vaginal epithelium supporting the idea that human vaginal epithelium derives solely from urogenital sinus epithelium. Aside for the vagina, most of the female reproductive tract is derived from the Müllerian ducts, which fuse in the midline to form the uterovaginal canal, the precursor of uterine corpus and uterine cervix an important player in vaginal development as well. Epithelial and mesenchymal differentiation markers are described during human female reproductive tract development (keratins, homeobox proteins (HOXA11 and ISL1), steroid receptors (estrogen receptor alpha and progesterone receptor), transcription factors and signaling molecules (TP63 and RUNX1), which are expressed in a temporally and spatially dynamic fashion. The utility of xenografts and epithelial-mesenchymal tissue recombination studies are reviewed.

Tissue interactions and estrogenic response during human female fetal reproductive tract development

The role of tissue interactions was explored to determine whether epithelial differentiation within the developing human reproductive tract is induced and specified by mesenchyme in tissue recombinants composed of mouse vaginal mesenchyme + human uterine tubal epithelium (mVgM+hTubE). The tissue recombinants were grown in DES-treated ovariectomized athymic mice. After 2-4 weeks of in vivo growth, several vaginal specific features were expressed in the human tubal epithelium. The mesenchyme-induced effects included morphological change as well as expression of several immunohistochemical markers. Although the mesenchyme-induced shift in vaginal differentiation in the human tubal epithelium was not complete, the partial induction of vaginal markers in human tubal epithelium verifies the importance of mesenchymal-epithelial interactions in development of the human female reproductive tract. In a separate experiment, DES-induction of uterine epithelial progesterone receptor (PGR) and estrogen receptor 1 (ESR1) was explored in tissue recombinants composed of wild-type or Esr1KO mouse uterine mesenchyme + human fetal uterine epithelium (wt UtM+hUtE and Esr1KO UtM+hUtE). The rationale of this experiment was to determine whether DES-induction of PGR and ESR1 is mediated directly via epithelial ESR1 or indirectly (paracrine mechanism) via mesenchymal ESR1. DES-induction of uterine epithelial ESR1 and PGR in Esr1KO UtM+hUtE tissue recombinants (devoid of mesenchymal ESR1) formally eliminates the paracrine mechanism and demonstrates that DES induction of human uterine epithelial ESR1 and PGR is directly mediated via epithelial ESR1.

Response of xenografts of developing human female reproductive tracts to the synthetic estrogen, diethylstilbestrol

Human female fetal reproductive tracts 9.5-22 weeks of gestation were grown for 1 month in ovariectomized athymic adult female mouse hosts that were either untreated or treated continuously with diethylstilbestrol (DES) via subcutaneous pellet. Normal morphogenesis and normal patterns of differentiation marker expression (KRT6, KRT7, KRT8, KRT10, KRT14, KRT19, ESR1, PGR, TP63, RUNX1, ISL1, HOXA11 and α-ACT2) were observed in xenografts grown in untreated hosts and mimicked observations of previously reported (Cunha et al., 2017) non-grafted specimens of comparable age. DES elicited several notable morphological affects: (a) induction of endometrial/cervical glands, (b) increased plication (folding) of tubal epithelium, (c) stratified squamous maturation of vaginal epithelium and (d) vaginal adenosis. DES also induced ESR1 in epithelia of the uterine corpus, cervix and globally induced PGR in most cells of the developing human female reproductive tract. Keratin expression (KRT6, KRT7, KRT8, KRT14 and KRT19) was minimally affected by DES. Simple columnar adenotic epithelium was devoid of TP63 and RUNX1, while DES-induced mature vaginal epithelium was positive for both transcription factors. Another striking effect of DES was observed in grafts of human uterine tube, in which DES perturbed smooth muscle patterning. These results define for the first time IHC protein markers of DES action on the developing human reproductive tract, which provide bio-endpoints of estrogen-induced teratogenesis in the developing human female reproductive tract for future testing of estrogenic endocrine disruptors.

Molecular mechanisms of development of the human fetal female reproductive tract

Human female reproductive tract development rests mostly upon hematoxilyn and eosin stained sections despite recent advances on molecular mechanisms in mouse studies. We report application of immunohistochemical methods to explore the ontogeny of epithelial and mesenchymal differentiation markers (keratins, homobox proteins, steroid receptors), transcription factors and signaling molecules (TP63 and RUNX1) during human female reproductive tract development. Keratins 6, 7, 8, 10, 14 and 19 (KRT6, KRT7, KRT8, KRT10, KRT14, KRT19) were expressed in a temporally and spatially dynamic fashion. The undifferentiated Müllerian duct and uterovaginal canal, lined by simple columnar epithelia, expressed KRT7, KRT8 and KRT19. Glandular derivatives of the Müllerian duct (uterine tube, uterine corpus and endocervix) maintained expression of these keratins, while tissues that undergo stratified squamous differentiation (exocervix and vagina) expressed KRT6, KRT14 and KRT10 during development in an age-dependent fashion. TP63 and RUNX1 were expressed prior to KRT14, as these two transcription factors are known to be upstream from KRT14 in developing Müllerian epithelium. In the vagina, KRT10, a marker of terminal differentiation, appeared after endogenous estrogens transformed the epithelium to a thick glycogenated squamous epithelium. Uroplakin, a protein unique to urothelium, was expressed only in the bladder, urethra and vaginal introitus, but not in the female reproductive tract itself. Mesenchymal differentiation was examined through immunostaining for HOXA11 (expressed in uterine mesenchyme) and ISL1 (expressed in vaginal mesenchyme). A detailed ontogeny of estrogen receptor alpha (ESR1), progesterone receptor (PGR) and the androgen receptor (AR) provides the mechanistic underpinning for the teratogenicity of estrogens, progestins and androgens on female reproductive tract development. Immunohistochemical analysis of differentiation markers and signaling molecules advance our understanding of normal development of the human female reproductive tract. These observations demonstrate remarkable similarities in mouse and human female reproductive tract development, but also highlight some key differences.

Evaluation of a New Reproductive Toxicology Protocol Using Diethylstilbestrol (DES) as a Positive Control Compound

A new National Toxicology Program (NTP) reproductive toxicology assay designated Fertility Assessment by Continuous Breeding was evaluated using trans-diethylstilbestrol (DES) as a positive control compound. The testing scheme employs young adult CD-1 male and female mice and is comprised of 5 possible tasks: task 1, 14-day dose-finding (repeated or continuous dosing); task 2, continuous breeding; task 3, determination of affected sex; task 4, offspring assessment; task 5, hormone patterns. Only tasks 2 and 3 were performed in the present study. Task 2 employed dietary levels of 0, 1, 10, and 50 ppb DES (99% pure). Task 3 used the control and high dose parental mice from task 2 in a crossover mating trial (control x treated) to determine whether one or both sexes in the F0 generation were adversely affected. Continuous exposure of F0 mice to 50 ppb DES in the diet during task 2 significantly decreased (P < 0.01) the proportion of pairs that produced at least 1 litter as compared to pairs continuously exposed to dietary levels of 0, 1, and 10 ppb DES. In addition, continuous exposure to 50 ppb DES in the diet had a cumulative adverse effect on the production and viability of litters. Thus, the pairs fed 50 ppb DES produced significantly fewer litters (P < 0.01), had fewer live pups per litter (P < 0.01), and tended toward a lower proportion of pups born alive per litter than did pairs in the 0, 1, and 10 ppb DES groups. In the crossover mating trial (task 3) the proportion of F0 females that mated (number with copulatory plugs/number cohabited) and that were fecund (number delivering litters/number with copulatory plugs) did not differ significantly among the 3 different combinations of paired mice. It was noted, however, that the proportion of cohabited F0 females delivering litters (number delivering litters/number cohabited) was significantly reduced (P < 0.05) in the control male x 50 ppb DES female group vs. the control male x control female group. The proportion of cohabited F0 females delivering litters in the 50 ppb DES male x control female group did not differ significantly from either of the above groups. Further, the number of live pups per litter and the proportion of pups born alive were significantly lower (P < 0.01) in the F0 control male x 50 ppb DES female group than in the other 2 groups. The proportion of male pups born alive (males/total) and the live pup weights, however, did not differ significantly among the 3 combinations of paired mice. Collectively, these results indicated that DES interfered with ovulation, conception, pre- and postimplantational processes in female mice. Thus, this new assay readily discriminated DES as a reproductive toxicant in CD-1 mice.

Constitutive Notch Signaling Causes Abnormal Development of the Oviducts, Abnormal Angiogenesis, and Cyst Formation in Mouse Female Reproductive Tract

The Notch signaling pathway is critical for the differentiation of many tissues and organs in the embryo. To study the consequences of Notch1 gain-of-function signaling on female reproductive tract development, we used a cre-loxP strategy and Amhr2-cre transgene to generate mice with conditionally activated Notch1 (Rosa(Notch1)). The Amhr2-cre transgene is expressed in the mesenchyme of developing female reproductive tract and in granulosa cells in the ovary. Double transgenic Amhr2-cre, Rosa(Notch1) females were infertile, whereas control Rosa(Notch1) mice had normal fertility. All female reproductive organs in mutants showed hemorrhaging of blood vessels progressing with age. The mutant oviducts did not develop coiling, and were instead looped around the ovary. There were multiple blockages in the lumen along the oviduct length, creating a barrier for sperm or oocyte passage. Mutant females demonstrated inflamed uteri with increased vascularization and an influx of inflammatory cells. Additionally, older females developed ovarian, oviductal, and uterine cysts. The significant change in gene expression was detected in the mutant oviduct expression of Wnt4, essential for female reproductive tract development. Similar oviductal phenotypes have been detected previously in mice with activated Smo and in beta-catenin, Wnt4, Wnt7a, and Dicer conditional knockouts, indicating a common regulatory pathway disrupted by these genetic abnormalities.

Male reprotoxicity and endocrine disruption

Mammalian reproductive tract development is a tightly regulated process that can be disrupted following exposure to drugs, toxicants, endocrine-disrupting chemicals (EDCs), or other compounds via alterations to gene and protein expression or epigenetic regulation. Indeed, the impacts of developmental exposure to certain toxicants may not be fully realized until puberty or adulthood when the reproductive tract becomes sexually mature and altered functionality is manifested. Exposures that occur later in life, once development is complete, can also disrupt the intricate hormonal and paracrine interactions responsible for adult functions, such as spermatogenesis. In this chapter, the biology and toxicology of the male reproductive tract is explored, proceeding through the various life stages including in utero development, puberty, adulthood, and senescence. Special attention is given to the discussion of EDCs, chemical mixtures, low-dose effects, transgenerational effects, and potential exposure-related causes of male reproductive tract cancers.

Mouse oviduct development

The oviduct, or Fallopian tube in humans, transports oocytes and sperm, serves as the site of fertilization, and supports early embryonic development. The oviduct is essential for fertility. In the mouse, the oviduct is a coiled, complex structure that develops from the simple embryonic Müllerian duct. The oviduct consists of four segments, including the infundibulum, ampulla, isthmus, and uterotubal junction. Additionally, the mouse oviduct forms coils, develops longitudinal folds, and undergoes both mesenchymal and epithelial differentiation. Oviduct development and differentiation occurs perinatally. Several signaling pathways have been found to be involved in oviduct formation, such as Wnt, Tgfβ, microRNA processing, as well as others. Overall, the process of oviduct development is poorly understood and can be utilized to further knowledge of epithelial-mesenchymal interactions, regulation of coiling, characteristics of pseudostratified epithelia, and smooth muscle differentiation.

Dominant activation of the hedgehog signaling pathway alters development of the female reproductive tract

The role of hedgehog (HH) signaling in reproductive tract development was studied in mice in which a dominant active allele of the signal transducer smoothened (SmoM2) was conditionally expressed in the Müllerian duct and ovary. Mutant females are infertile, primarily because they fail to ovulate. Levels of mRNA for targets of HH signaling, Gli1, Ptch1, and Hhip, were elevated in reproductive tracts of 24-day-old mutant mice, confirming overactivation of HH signaling. The tracts of mutant mice developed abnormally. The uterine luminal epithelium had a simple columnar morphology in control mice, but in mutants contained stratified squamous cells typical of the cervix and vagina. In mutant mice, the number of uterine glands were reduced and the oviducts were not coiled. Expression of genes within the Hox and Wnt families that regulate patterning of the reproductive tract were altered. Hoxa13, which is normally expressed primarily in the vagina and cervix, was expressed at 12-fold higher levels in the uterus of mutant mice compared with controls. Wnt5a, which is required for development of the cervix and vagina and postnatal differentiation of the uterus, was expressed at higher levels in the oviduct and uterus of mutant mice compared with controls. Mating mutant females with fertile or vasectomized males induced a severe inflammatory response in the tract. In summary, overactivation of HH signaling causes aberrant development of the reproductive tract. The phenotype observed could be mediated by ectopic expression of Hoxa13 in the uterus and elevated levels of Wnt5a in the oviducts and uterus.

Molecular mechanisms of induction of persistent changes by estrogenic chemicals on female reproductive tracts and external genitalia

The effects of environmental endocrine-disrupting chemicals (EDCs) are a great and growing concern for human and animal development and life. The reproductive organs are considered as a primary target of EDCs, yet the effects on reproductive organs can extend to other body systems. Perinatal diethylstilbestrol (DES)-exposed mice exhibit various reproductive organ abnormalities. The perinatal DES-exposure model has allowed insight into our understanding of the mechanisms of persistent reproductive organ abnormalities elicited by exposure to estrogens and/or estrogenic EDCs. The persistent changes in the vagina of neonatally DES-exposed mice result from sustained expression of growth factors by ligand-independent transcriptional activation of the estrogen receptor. Developmental regulatory genes, such as Wnt and Hox genes, are also targets of DES during fetal stages and altered gene expression can induce malformations of the reproductive organs. In this review, we focus on the development of female reproductive tracts and external genitalia, and discuss the recent progress in understanding the disruptive effects of estrogens and EDCs on these organs.

Perinatal exposure to environmentally relevant levels of bisphenol A decreases fertility and fecundity in CD-1 mice

BACKGROUND

Perinatal exposure to low-doses of bisphenol A (BPA) results in alterations in the ovary, uterus, and mammary glands and in a sexually dimorphic region of the brain known to be important for estrous cyclicity.

OBJECTIVES

We aimed to determine whether perinatal exposure to environmentally relevant doses of BPA alters reproductive capacity.

METHODS

Female CD-1 mice that were exposed to BPA at 0, 25 ng, 250 ng, or 25 µg/kg body weight (BW)/day or diethylstilbestrol (DES) at 10 ng/kg BW/day (positive control) from gestational day 8 through day 16 of lactation were continuously housed with proven breeder males for 32 weeks starting at 2 months of age. At each delivery, pups born to these mating pairs were removed. The cumulative number of pups, number of deliveries, and litter size were recorded. The purity of the BPA used in this and our previous studies was assessed using HPLC, mass spectrometry, and nuclear magnetic resonance.

RESULTS

The forced breeding experiment revealed a decrease in the cumulative number of pups, observed as a nonmonotonic dose-response effect, and a decline in fertility and fecundity over time in female mice exposed perinatally to BPA. The BPA was 97% pure, with no evidence of contamination by other phenolic compounds.

CONCLUSIONS

Perinatal exposure to BPA leads to a dose-dependent decline in the reproductive capacity of female mice. The effects on the cumulative number of pups are comparable to those previously reported in mice developmentally exposed to DES, a compound well known to impair reproduction in women. This association suggests the possibility that early BPA exposure may also affect reproductive capacity in women.

Dicer is required for female reproductive tract development and fertility in the mouse

Dicer encodes a riboendonuclease required for microRNA biosynthesis. Dicer was inactivated in Müllerian duct mesenchyme-derived tissues of the reproductive tract of the mouse, using an Amhr2-Cre allele. Although Amhr2-Cre; Dicer conditional mutant males appeared normal and were fertile, mutant females were infertile. In adult mutant females, there was a reduction in the size of the oviducts and uterine horns. The oviducts were less coiled compared to controls and cysts formed at the isthmus near the uterotubal junction. Unfertilized, degenerate oocytes were commonly found within these cysts, indicating a defect in embryo transit. Beads transferred into the mutant oviduct failed to migrate into the uterus. In addition, blastocysts transferred directly into the mutant uterus did not result in pregnancy. Histological analysis demonstrated that the mutant uterus contained less glandular tissue and often the few glands that remained were found within the myometrium, an abnormal condition known as adenomyosis. In adult mutants, there was ectopic expression of Wnt4 and Wnt5a in the luminal epithelium (LE) and glandular epithelium (GE) of the uterus, and Wnt11 was ectopically expressed in GE. These results demonstrate that Dicer is necessary for postnatal differentiation of Müllerian duct mesenchyme-derived tissues of the female reproductive tract, suggesting that microRNAs are important regulators of female reproductive tract development and fertility.

Prenatal exposure to bisphenol a at environmentally relevant doses adversely affects the murine female reproductive tract later in life

BACKGROUND

Exposure to endocrine-disrupting chemicals during critical developmental periods causes adverse consequences later in life; an example is prenatal exposure to the pharmaceutical diethylstilbestrol (DES). Bisphenol A (BPA), an environmental estrogen used in the synthesis of plastics, is of concern because its chemical structure resembles that of DES, and it is a "high-volume production" chemical with widespread human exposure.

OBJECTIVES

In this study we investigated whether prenatal BPA causes long-term adverse effects in female reproductive tissues in an experimental animal model previously shown useful in studying effects of prenatal DES.

METHODS

Timed pregnant CD-1 mice were treated on days 9-16 of gestation with BPA (0.1, 1, 10, 100, or 1,000 mug/kg/day). After delivery, pups were held for 18 months; reproductive tissues were then evaluated.

RESULTS

Ovarian cysts were significantly increased in the 1-mug/kg BPA group; ovarian cyst-adenomas were seen in the other three BPA-treated groups but not in corn-oil controls. We observed increased progressive proliferative lesions of the oviduct after BPA treatment, similar to those described in response to DES. Further, although not statistically different from the controls, prominent mesonephric (Wolffian) remnants and squamous metaplasia of the uterus, as well as vaginal adenosis, were present in BPA-treated mice, similar to lesions reported following DES treatment. More severe pathologies observed in some BPA-treated animals included atypical hyperplasia and stromal polyps of the uterus; sarcoma of the uterine cervix; and mammary adenocarcinoma. We did not observe these lesions in controls.

CONCLUSIONS

These data suggest that BPA causes long-term adverse reproductive and carcinogenic effects if exposure occurs during critical periods of differentiation.

Proceedings of the Summit on Environmental Challenges to Reproductive Health and Fertility: executive summary

The 2007 Summit on Environmental Challenges to Reproductive Health and Fertility convened scientists, health care professionals, community groups, political representatives, and the media to hear presentations on the impact of environmental contaminants on reproductive health and fertility, and to discuss opportunities to improve health through research, education, communication, and policy. Environmental reproductive health focuses on exposures to environmental contaminants, particularly during critical periods of development, and their potential effects on future reproductive health, including conception, fertility, pregnancy, adolescent development, and adult health. Approximately 87,000 chemical substances are registered for commercial use in the United States, with ubiquitous human exposures to environmental contaminants in air, water, food, and consumer products. Exposures during critical windows of susceptibility may result in adverse effects with lifelong and even intergenerational health impacts. Effects can include impaired development and function of the reproductive tract and permanently altered gene expression, leading to metabolic and hormonal disorders, reduced fertility and fecundity, and illnesses such as testicular, prostate, uterine, and cervical cancers later in life. This executive summary reviews effects of pre- and postnatal exposures on male and female reproductive health, and provides a series of recommendations for advancing the field in the areas of research, policy, health care, and community action.

Proceedings of the Summit on Environmental Challenges to Reproductive Health and Fertility: executive summary

The 2007 Summit on Environmental Challenges to Reproductive Health and Fertility convened scientists, health care professionals, community groups, political representatives, and the media to hear presentations on the impact of environmental contaminants on reproductive health and fertility, and to discuss opportunities to improve health through research, education, communication, and policy. Environmental reproductive health focuses on exposures to environmental contaminants, particularly during critical periods of development, and their potential effects on future reproductive health, including conception, fertility, pregnancy, adolescent development, and adult health. Approximately 87,000 chemical substances are registered for commercial use in the United States, with ubiquitous human exposures to environmental contaminants in air, water, food, and consumer products. Exposures during critical windows of susceptibility may result in adverse effects with lifelong and even intergenerational health impacts. Effects can include impaired development and function of the reproductive tract and permanently altered gene expression, leading to metabolic and hormonal disorders, reduced fertility and fecundity, and illnesses such as testicular, prostate, uterine, and cervical cancers later in life. This executive summary reviews effects of pre- and postnatal exposures on male and female reproductive health, and provides a series of recommendations for advancing the field in the areas of research, policy, health care, and community action.

Long-term adverse effects of neonatal exposure to bisphenol A on the murine female reproductive tract

The developing fetus is uniquely sensitive to perturbation by chemicals with hormone-like activity. The adverse effects of prenatal diethylstilbestrol (DES) exposure are a classic example. Since concern has been mounting regarding the human health and environmental effects of bisphenol A (BPA), a high-production-volume chemical with estrogenic activity used in the synthesis of plastics, we investigated its long-term effects in an experimental animal model that was previously shown useful in studying the adverse effects of developmental exposure to DES. Outbred female CD-1 mice were treated on days 1-5 with subcutaneous injections of BPA (10, 100 or 1000 microg/kg/day) dissolved in corn oil or corn oil alone (Control). At 18 months, ovaries and reproductive tract tissues were examined. There was a statistically significant increase in cystic ovaries and cystic endometrial hyperplasia (CEH) in the BPA-100 group as compared to Controls. Progressive proliferative lesion (PPL) of the oviduct and cystic mesonephric (Wolffian) duct remnants were also seen in all of the BPA groups. More severe pathologies of the uterus following neonatal BPA treatment included adenomyosis, leiomyomas, atypical hyperplasia, and stromal polyps. These data suggest that BPA causes long-term adverse effects if exposure occurs during critical periods of differentiation.

Adverse effects of the model environmental estrogen diethylstilbestrol are transmitted to subsequent generations

The synthetic estrogen diethylstilbestrol (DES) is a potent perinatal endocrine disruptor. In humans and experimental animals, exposure to DES during critical periods of reproductive tract differentiation permanently alters estrogen target tissues and results in long-term abnormalities such as uterine neoplasia that are not manifested until later in life. Using the developmentally exposed DES mouse, multiple mechanisms have been identified that play a role in its carcinogenic and toxic effects. Analysis of the DES murine uterus reveals altered gene expression pathways that include an estrogen-regulated component. Thus, perinatal DES exposure, especially at low doses, offers the opportunity to study effects caused by weaker environmental estrogens and provides an example of the emerging scientific field termed the developmental origin of adult disease. As a model endocrine disruptor, it is of particular interest that even low doses of DES increase uterine tumor incidence. Additional studies have verified that DES is not unique; when other environmental estrogens are tested at equal estrogenic doses, developmental exposure results in increased incidence of uterine neoplasia similar to that caused by DES. Interestingly, our data suggest that this increased susceptibility for tumors is passed on from the maternal lineage to subsequent generations of male and female descendants; the mechanisms involved in these transgenerational events include genetic and epigenetic events. Together, our data point out the unique sensitivity of the developing organism to endocrine-disrupting chemicals, the occurrence of long-term effects after developmental exposure, and the possibility for adverse effects to be transmitted to subsequent generations.

Evaluation of a two-generation reproduction toxicity study adding endpoints to detect endocrine disrupting activity using vinclozolin

A two-generation reproduction toxicity study in rats adding extra endpoints to detect endocrine disrupting activity was conducted using vinclozolin by dietary administration at 0, 40, 200, and 1000 ppm, for investigation of its utility. The extra endpoints included anogenital distance (AGD), nipple development, sexual maturation (vaginal opening and preputial separation), estrous cycle, spermatogenesis, sex organ weights, and blood hormone concentrations (thyroid and sex hormones). Hepatic drug-metabolizing enzyme activities were also measured. The results revealed changes due to vinclozolin in the AGD, nipple development, sexual maturation, sex organ weights, and blood sex hormone concentrations in males of both parental animals and offspring, even at the lowest dose of 40 ppm, confirmed by results for the classical endpoints of histopathological examination at 200 ppm and mating at 1000 ppm. The effects on parental males included increased pituitary and testis weights, and decreased epididymis weights at 1000 ppm in both generations, and decreased prostate and epididymis weights at 200 and 1000 ppm and seminal vesicle weights at 1000 ppm in F1 males. Histopathological examination revealed hypertrophy of the basophilic cells in the pituitary at these two doses, and diffuse hyperplasia of the testicular interstitial cells and atrophy of the seminal vesicle mucosa at 1000 ppm in F0 and F1 males. In addition, F1 males demonstrated decrease in prostate fluid at 200 and 1000 ppm. Blood hormone analysis revealed increases in LH, FSH, testosterone, and DHT in F0 and F1 males at 1000 ppm. General toxicological effects included suppressed body weight gain in F0 and F1 females and in F1 males, and reduced food consumption in F0 and F1 females at 1000 ppm. Histopathological examination revealed centrilobular hepatocellular hypertrophy in males at 200 and 1000 ppm and in females at 1000 ppm, increased lipid droplets in the adrenal zona fasciculata and zona glomerulosa in males at 200 and 1000 ppm and in females at 40 ppm and above, and hyperplasia of ovarian interstitial cells and vacuolation of lutein cells in females at 1000 ppm in both generations. Almost all the tissue changes were accompanied by changes in weights. Decreases in T3 and/or T4 were observed in both sexes and generations at 1000 ppm and in F0 females at 200 ppm. However, these were presumed to be secondary to induction of hepatic drug-metabolizing enzymes, activities being increased for a range of enzymes in both sexes and generations at 1000 ppm. Rise in BROD activity was the most prominent, suggesting that vinclozolin mainly induces CYP2B. As for effects on reproductive function, a marked decrease in the fertility index caused by male infertility was observed in F1 animals at 1000 ppm. However, no effects on spermatogenesis were seen in either F0 or F1 males. Since cleft prepuce and penile hypoplasia were observed in infertile males, it is probable that the cause of infertility in F1 males was related to morphological abnormalities in the external genitalia. Vinclozolin did not affect the estrous cycle, mating, fertility, pregnancy, parturition, or nursing behavior in either F0 or F1 females. In offspring, in addition to suppressed body weight gain in F1 males and females at 1000 ppm, neonatal toxicity caused by antiandrogen activity of vinclozolin was observed in F1 and F2 males. Effects included shortened AGD in F1 males at 1000 ppm and in F2 males at 200 and 1000 ppm, and nipple/areola remnants in F1 males at 200 and 1000 ppm and in F2 males at 40 ppm and above. In addition, decreased epididymis weights at weaning and morphological abnormalities of the external genitalia, including cleft prepuce, penile hypoplasia, and vaginal pouch, were seen in F1 and F2 males at 1000 ppm.

MSX2 promotes vaginal epithelial differentiation and wolffian duct regression and dampens the vaginal response to diethylstilbestrol

In utero exposure to diethylstilbestrol (DES) leads to patterning defects in the female reproductive tract (FRT) and a propensity to the development of vaginal adenocarcinomas in humans. In the mouse, DES treatment similarly induces a plethora of FRT developmental defects, including stratification of uterine epithelium and presence of glandular tissue in cervix and vagina. Uterine abnormalities are associated with repression of the homeobox gene Msx2, and DES leads to an altered uterine response in Msx2 mutants including a dilated uterine lumen. Here we investigate the role of Msx2 in normal vaginal development and in FRT response to DES. During vaginal development, Msx2 is required for Tgfbeta2 and Tgfbeta3 expression and for proper vaginal epithelial differentiation. Moreover, Msx2 is involved in caudal Wolffian duct regression by promoting apoptosis. Consistently, neonatal DES exposure represses Msx2 expression in the Wolffian duct epithelium and inhibits its apoptosis and subsequent regression. Intriguingly, although DES treatment also represses Msx2 expression in the vaginal epithelium, a much more severe DES-induced vaginal phenotype was observed in Msx2 mutant mice, including a complete failure of Müllerian vaginal epithelial stratification and a severely dilated vaginal lumen, accompanied by loss of p63 and water channel protein expression. These results demonstrate a critical role for Msx2 in counteracting the effect of DES on FRT patterning and suggest that the response to DES may be highly variable depending on the genotype of an individual.

EVALUATION OF A TWO-GENERATION REPRODUCTION TOXICITY STUDY ADDING ENDOPOINTS TO DETECT ENDOCRINE DISRUPTING ACTIVITY USING LINDANE

A two-generation reproduction toxicity study in rats adding extra endpoints to detect endocrine disrupting activity was conducted using lindane by dietary administration at 0, 10, 60, and 300 ppm, for investigation of its utility. The extra endpoints included anogenital distance (AGD), nipple development, sexual maturation (vaginal opening and preputial separation), estrous cycle, spermatogenesis, sex organ weights, and blood hormone concentrations (thyroid and sex hormones). F1 offspring were examined for emotionality (open field test), motor coordination (rotarod test), as well as learning and memory (pole-climbing test). Hepatic drug-metabolizing enzyme activities were also measured. The results revealed general toxicological effects on parental animals, influence on reproductive function, and altered development of offspring; however, they did not demonstrate any distinct changes in the extra endpoints for detection of endocrine disrupting activity. Adult toxicity was observed in both F0 and F1 animals, including suppressed body weight gain and reduced food consumption in both sexes, and deaths of females at 300 ppm. Convulsions and irritability were observed during the perinatal period in pregnant F1 females given 300 ppm. Pathological examination revealed increased liver weights and centrilobular hepatocellular hypertrophy in both sexes and generations at 10 or 60 ppm and above; in addition, increased kidney weights and increased hyaline droplets in the proximal tubule epithelium, and basophilic renal tubules in males were noted at 10 ppm and above. Pituitary weights were decreased in F0 females and in F1 males and females and adrenal weights were increased in F1 males and females at 300 ppm; however, no histological changes were observed, and manifestations suggesting endocrine disrupting activity related to these changes were lacking. Hypertrophy of the thyroid follicular epithelium in F0 females at 300 ppm and in F1 males at 60 and 300 ppm, and decreases in T3 and/or T4 in both sexes and generations at 300 ppm were presumed to be secondary changes associated with the induction of hepatic drug-metabolizing enzymes. Blood hormone analysis revealed no changes in sex hormones attributable to lindane in males or females. Hepatic drug-metabolizing enzyme activities were increased dose-dependently from 10 ppm in both sexes and generations, with the rise in BROD activity being the most prominent. There were also increases in MROD, EROD, T-6beta-OH, and T4-UDP-GT activities (BROD >> EROD > MROD, T-6beta-OH, T4-UDP-GT). This suggests that while lindane most strongly induces CYP2B, it also upregulates a number of other drug metabolizing enzymes, such as CYP1A, CYP3A, and UDP-GT. As for effects on reproductive function, lack of maternal behavior, including lactation and retrieval behavior, and consequent total litter loss were observed in F1 dams at 300 ppm. There were no effects of lindane on the estrous cycle, spermatogenesis, mating, fertility, pregnancy, or parturition. Neonatal toxicity was observed in both sexes and generations, including suppressed body weight gain at 60 and 300 ppm, and decreased thymus and spleen weights without histological change at 300 ppm. The postnatal survival rate in F2 offspring was decreased due to lack of maternal behavior in dams at 300 ppm.

SEX STEROID HORMONE RECEPTORS IN THE DEVELOPING FEMALE REPRODUCTIVE TRACT OF LABORATORY RODENTS

Many chemicals released into the environment potentially disrupt the endocrine system in wildlife and humans. Some of these chemicals exhibit estrogenic activity by binding to the estrogen receptors. The developing organism is particularly sensitive to estrogenic chemicals during the critical period in which the induction of long-term changes and persistent molecular alterations in female reproductive tracts occur. Perinatal mouse and rat models can be utilized as indicators for determining the consequences of exposure to exogenous estrogenic agents, including possible xenoestrogens or environmental endocrine disruptors. Estrogen receptors (ER) and estrogen responsive genes, therefore, need to be identified in order to understand the molecular basis of estrogenic actions. Recent identifications of ER subtypes and isoforms make understanding target organ responses to these estrogenic chemicals even more difficult. Indeed, many reports suggest that these chemicals do affect the reproductive and developmental processes of female laboratory rodents that had been perinatally exposed, and that interactions between sex steroid hormone receptors occur. Much information concerning the expression of sex steroid receptors in rodents has been reported concerning the normal development of the Müllerian duct. Thus, accumulated information on the expression of ER subtypes and isoforms as well as that of progesterone and androgen receptors in laboratory rodents is herein reviewed, in addition to the presentation of our own data.

Lessons learned from perinatal exposure to diethylstilbestrol

The synthetic estrogen diethylstilbestrol (DES) is well documented to be a perinatal carcinogen in both humans and experimental animals. Exposure to DES during critical periods of differentiation permanently alters the programming of estrogen target tissues resulting in benign and malignant abnormalities in the reproductive tract later in life. Using the perinatal DES-exposed rodent model, cellular and molecular mechanisms have been identified that play a role in these carcinogenic effects. Although DES is a potent estrogenic chemical, effects of low doses of the compound are being used to predict health risks of weaker environmental estrogens. Therefore, it is of particular interest that developmental exposure to very low doses of DES has been found to adversely affect fertility and to increase tumor incidence in murine reproductive tract tissues. These adverse effects are seen at environmentally relevant estrogen dose levels. New studies from our lab verify that DES effects are not unique; when numerous environmental chemicals with weak estrogenic activity are tested in the experimental neonatal mouse model, developmental exposure results in an increased incidence of benign and malignant tumors including uterine leiomyomas and adenocarcinomas that are similar to those shown following DES exposure. Finally, growing evidence in experimental animals suggests that some adverse effects can be passed on to subsequent generations, although the mechanisms involved in these trans-generational events remain unknown. Although the complete spectrum of risks to DES-exposed humans are uncertain at this time, the scientific community continues to learn more about cellular and molecular mechanisms by which perinatal carcinogenesis occurs. These advances in knowledge of both genetic and epigenetic mechanisms will be significant in ultimately predicting risks to other environmental estrogens and understanding more about the role of estrogens in normal and abnormal development.

Fertility potential of women with congenital ampullary atresia of the fallopian tube

OBJECTIVE

To determine the fertility potential of women with congenital ampullary atresia of the fallopian tube.

DESIGN

Case report and review of literature.

SETTING

University-affiliated tertiary care infertility clinic.

PATIENT(S)

Six infertile women with congenital ampullary atresia of the oviduct.

INTERVENTION(S)

Salpingostomy and fimbrial approximation.

MAIN OUTCOME MEASURE(S)

Pregnancy.

RESULT(S)

Of six reported cases of congenital ampullary atresia of the fallopian tube who underwent surgery, four women conceived intrauterine pregnancies (IUP) and another, a pregnancy of undetermined site.

CONCLUSION(S)

Salpingostomy and fimbrial approximation is a therapeutic option for infertile women with congenital ampullary atresia of the fallopian tube.

Characterization of uterine leiomyomas in CD-1 mice following developmental exposure to diethylstilbestrol (DES)

Experimental animal and clinical studies have well established the association of prenatal exposure to diethylstilbestrol (DES) and the subsequent development of reproductive tract abnormalities, including poor reproductive outcome and neoplasia. Overwhelmingly, the focus has been on DES-induced epithelial lesions, particularly vaginal adenosis and adenocarcinoma; however, uterine smooth muscle cells are also recognized as cellular targets of DES. This descriptive report characterizes uterine leiomyomas that occur in outbred CD-1 mice following exposure to DES prenatally on days 9 to 16 of gestation or on neonatal days 1 to 5. These DES-induced uterine leiomyomas have typical histomorphologic, and some immunohistochemical characteristics of spontaneously occurring uterine smooth muscle tumors of B6C3F1 mice previously described in our laboratory, and they are also similar to uterine leiomyomas (fibroids) commonly observed in premenopausal women.

Abdominal B (AbdB) Hoxa genes: regulation in adult uterus by estrogen and progesterone and repression in müllerian duct by the synthetic estrogen diethylstilbestrol (DES)

Mice deficient for the Abdominal B (AbdB) Hox gene Hoxa-10 exhibit reduced fertility due to defects in implantation. During the peri-implantation period Hoxa-10 is sequentially expressed in the uterine epithelium and stroma. These observations, combined with the stringent regulation of uterine implantation by ovarian steroids, prompted us to test whether estrogen and progesterone directly regulate the expression of Hoxa-10 and other AbdB Hoxa genes. Here we show that Hoxa-10 expression in the adult uterus is strongly activated by progesterone. This activation is blocked by the progesterone receptor antagonist RU486 and is independent of new protein synthesis. In addition, Hoxa-10 expression is repressed by estrogen in a protein synthesis-independent manner. Analysis of adjacent AbdB Hoxa genes reveals that Hoxa-9 and a-11 are also activated in a colinear fashion by progesterone but differentially regulated by estrogen. These results suggest that the regulation of AbdB Hox gene expression in the adult uterus by ovarian steroids is a property related to position within the cluster, mediated by the direct action of estrogen and progesterone receptors upon these genes. We next examined whether the embryonic expression of Hoxa10 is regulable by hormonal factors. Previous work has demonstrated that perinatal administration of the synthetic estrogen diethylstilbestrol (DES) to mice and humans produces uterine, cervical, and oviductal malformations. Certain of these phenotypes resemble those in Hoxa-10 knockout mice, suggesting that Hoxa-10 gene expression might be repressed by DES during reproductive tract morphogenesis. Exposure of the developing female reproductive tract to DES, either in vivo or in organ culture, represses the expression of Hoxa-10 in the Müllerian duct. Thus, these data not only establish a direct link between ovarian steroids and AbdB Hoxa gene expression in the adult uterus, but also provide a potential mechanism for the teratogenic effects of DES on the developing reproductive tract.

Activation by human chorionic gonadotropin of ovarian carbonyl reductase in mature rats exposed in vivo to estrogens

We investigated the effects of exogenous estrogens and human chorionic gonadotropin (hCG) on the activity, content, and immunohistochemical localization of ovarian carbonyl reductase (CR) in mature cycling rats. Estrogens, estradiol, hexestrol (HEX) and diethylstilbestrol (DES) were given s.c. to rats daily for 3 days from the first day of diestrus, and hCG was given s.c. at 3:00 p.m. on the day of expected proestrus. The ovaries were isolated on the day of expected estrus. Ovarian CR activity was measured by using two substrates that reflect the activity of the enzyme in rats, and the enzyme content was determined by western blot analysis. Ovarian CR activity and content were decreased by estrogens as well as by inhibition of ovulation; hCG restored both the activity and the content decreased by estrogens to levels produced by hCG alone. Nevertheless, the number of ova in the oviduct when ovulation was decreased or blocked by estrogens was not restored completely by hCG treatment. Faint immunostaining in the interstitial gland cells of HEX-treated rat ovaries was observed. These results suggest that (i) although hCG activates ovarian CR in estrogen-treated rats, this increase in both enzyme activity and content may not be an obligatory event in the ovulatory process, and (ii) exogenous estrogens may predominantly influence the ovarian CR in the interstitial gland cells in mature rats by inhibiting luteinizing hormone release from the pituitary.

Gender-related behavior in women exposed prenatally to diethylstilbestrol

Accumulating evidence in experimental animals over the past three decades suggests that mammalian brain development and differentiation of the central nervous system are influenced by perinatal exposure to sex hormones. Hence, changes in human behavioral patterns may be associated with prenatal exposure to estrogenic substances such as diethylstilbestrol (DES). This paper reviews relevant studies from a series of laboratories and finds that no clear-cut differences can be demonstrated to date between unexposed and DES-exposed women in gender-related behavior, although the physical and psychological impact of the problems associated with exposure to DES are well documented. If both prenatal and postnatal influences such as social, economic, and environmental factors are taken into consideration, individual variation is more apparent than differences in gender-related behavior between unexposed and DES-exposed women. In summary, gender-related behavior is determined by a complex array of interacting factors, and prenatal influences are only one of many developmental events. More studies are needed using larger populations with carefully controlled selection criteria to suggest a direct role of prenatal DES exposure on subsequent gender-related behavior.

Altered patterns of proteins released in vitro from oviductal and uterine tissue from adult female mice treated neonatally with diethylstilbestrol

Proteins released during incubation in vitro of oviductal and uterine tissues from 8-week-old female NMRI mice treated neonatally with diethylstilbestrol (DES) or vehicle were studied. The objective was to study if neonatal DES treatment altered the patterns of proteins released from the oviduct and uterus, as earlier studies had shown a detrimental effect of the oviductal environment in DES exposed females on early embryo development. In separate experiments nonlabeled and 35S-labeled proteins released from oviductal/uterine tissues during organ incubations were characterized with 1 and 2D gel electrophoresis. The incubation media of both oviducts and uteri from DES females had increased levels of a serum derived nonlabeled protein, identified as apolipoprotein A1. The amount of this protein in the incubation medium was not influenced by previous ovariectomy but increased by in vivo treatment with estradiol, in both ovariectomized controls and DES treated females. Three other unlabeled proteins were consistently found in higher amounts in the incubation media from DES exposed oviduct/uterine tissue, than in incubates of control tissue. In tissue incubates of oviducts from DES females, three synthesized proteins (35 kDa-pl 6.2, 112 and 143 kDa) were released in lower amounts and two in higher amounts (53 kDa-pl 6.6 and 53 kDa-pl 6.8) than in controls. In uterus from DES treated females one labeled protein was released in increased amounts (80 kDa-pl 6.7) and one in decreased amounts (43 kDa-pl 6.6), when compared with controls. In estrogen induced uterine luminal fluid from 8-week-old DES treated females the levels of four proteins (26, 42, 53 and 97 kDa) were increased and two (24 and 32 kDa) were decreased. These results show permanent alterations in levels of secreted proteins in both the oviduct and uterus of adult but neonatally DES treated females, which could be of importance for their poor reproductive performance.

The functional importance of the oviduct in neonatally estrogenized mouse females for early embryo survival

Eight-week-old virgin untreated female mice were induced to ovulate using equine chorionic gonadotropin (eCG) and human chorionic gonadotropin (hCG), and were then caged with males overnight. Females with a vaginal plug on the following morning were killed 24 hours later and 2-cell embryos were flushed from the oviduct. These embryos were transferred to the oviduct of 8-week-old control females, to females of the same age treated with 5 micrograms diethylstilbestrol (DES) sc in olive oil for the first 5 days after birth, or to females treated with 1 microgram estradiol-17 beta for 2 days before and 2 days after transfer (estrogen dominated/ED/females). Two days after transfer, a significantly lower number of embryos were recovered from oviducts of DES females compared to control females and a still lower number from ED females. The recovered embryos were cultured in vitro for 4 days testing trophoblast outgrowth ("implantation stage"). The incidence of embryos reaching this stage after development in DES-exposed oviducts was only half of that for embryos passing control oviducts or ED oviducts. It is concluded that the adult oviductal environment in neonatally DES-treated females significantly decreases early embryo developmental potential. The oviductal factor(s) harmful to the embryo may be related to a persistent and possibly increased level of circulating estrogen level in DES females.

Ontogeny of peroxidase activity in epithelium and eosinophils of the mouse uterus

Outbred CD-1 mice treated for 1 or 4 days with 1 mg/kg of diethylstilbestrol (DES) at various ages after birth were examined for histochemical localization of peroxidase in the uterine epithelium. Peroxidase activity in uterine extracts was also measured by a radiometric assay and the conversion of [3H]DES to [3H]Z,Z-diensestrol (Z,Z-DIES). While no peroxidase activity was detected by a histochemical method in uterine epithelium from untreated 5-day old mice, the enzyme was apparent in mice treated for 4 days with DES; uterine eosinophils were absent at this age. By day 9, DES-induced staining for peroxidase in uterine epithelial cells and the number of uterine eosinophils had increased significantly. In addition, at this age, the biochemical assays for uterine peroxidase were sensitive enough to show that DES is converted to Z,Z-DIES and that [3H]estradiol gives rise to 3H2O and water-soluble radioactive metabolites. The peroxidase response to DES, determined by both histochemical and biochemical methods, increased with the age of the immature mice. These data indicate that the neonatal uterus, although deficient in eosinophils, demonstrates a peroxidase response to estrogen and that this response is localized primarily in the luminal epithelium. The role of this DES-induced peroxidase activity in converting DES to activated metabolites that may cause cell damage is discussed.

Epidermal growth factor binding and receptor distribution in the mouse reproductive tract during development

The ontogeny of the epidermal growth factor (EGF) receptor in the different cell types in the neonatal and immature mouse uterus and vagina was examined. Immunohistochemical examination of prenatal and neonatal reproductive tracts with a polyclonal antibody to the EGF receptor shows immunoreactive EGF receptors as early as Day 13 of gestation. Autoradiographic analysis of tissue sections at 3 to 17 days of age (the day of birth is Day 1) demonstrates that both uterine and vaginal epithelial and stromal cells are capable of binding 125I-labeled EGF. Both the 125I-labeled EGF autoradiography and immunohistochemistry in whole tissue show higher EGF receptor levels in the uterine epithelium than the uterine stroma. The presence of EGF receptors was also confirmed by affinity labeling and Scatchard analysis of isolated uterine cell types at 7 and/or 17 days of age. However, in contrast to the autoradiography and immunohistochemistry data of intact tissue, the affinity labeling and Scatchard data of isolated cells indicate that the uterine stroma contains higher levels of EGF receptor than that of the uterine epithelium. The reason for this discrepancy between the different techniques is, as yet, unknown. Regardless of the differences in the actual numbers of EGF receptors obtained, our data demonstrate that the developing mouse reproductive tract contains immunoreactive EGF receptors that are capable of binding 125I-labeled EGF.

Expression of nuclear estrogen-binding sites within developing human fetal vagina and urogenital sinus

An autoradiographic study of nuclear estrogen binding was performed in developing human urogenital sinuses and vaginas derived from first and second trimester specimens. Nuclear estrogen binding was detected in all specimens greater than or equal to 10 weeks of gestation within mesenchymal cells. Nuclear labelling within epithelium was observed only in those specimens whose development and differentiation was advanced. Thus, mesenchyme appears to be the initial estrogen target tissue within the developing human vagina and may play a fundamental role in estrogen-induced teratogenesis of the human genital tract.

Histology of the adult mouse oviduct and endometrium following a single prenatal exposure to diethylstilbestrol

Light microscopy was used to examine the oviduct and endometrium of offspring from mice administered DES (10 micrograms/kg in 0.1 cc of corn oil, subcutaneously) or corn oil alone on Day 15 of gestation. Offspring were sacrificed at 5, 7 and 9 months of age. Oviduct changes in DES exposed offspring included numerous abnormal secretory cells which lined the mucosal folds of the isthmus. These cells contained a distinct granular cytoplasm which was eosinophilic and a nucleus displaced towards the apical surface. In addition both the ampulla and isthmus had mucosal folds which extended to the serosal surface and an accumulation of subepithelial fibrinoid material. Endometrial changes included squamous metaplasia of both the surface and glandular epithelial layer as well as extensive cystic glandular hyperplasia. In addition the endometrial connective tissue stroma exhibited fibrinoid accumulation. These changes may reflect an altered endocrine environment resulting from ovarian abnormalities during adulthood.

The antiestrogen LY117018 is estrogenic in the fetal rat

LY117018 (LY) has high affinity for the adult rat uterine estrogen receptor, has little uterotrophic activity, and inhibits many estradiol (E2)-induced responses in the adult or immature uterus. In these studies, LY was injected into day 19 rat fetuses, with and without diethylstilbestrol (DES) or E2, to determine whether it could block the estrogen-induced teratogenesis. LY at 1, 25, or 50 micrograms/fetus failed to decrease the 15-70% incidences of oviduct malformation and cleft phallus induced by DES (2.5 micrograms/fetus) or E2 (50 micrograms/fetus). However, LY alone (1-50 micrograms/fetus) was more potent than E2 in eliciting these same urogenital malformations. LY also failed to compete in vitro for plasma protein-bound 3H-E2, and therefore, like DES, is more available than E2 for uptake into fetal tissues. Thus, in the fetus, unlike the adult, LY was an estrogen agonist, which indicates that the fetus has a very different sensitivity than the adult to estrogenic compounds.

Frequent occurrence of polyovular follicles in ovaries of mice exposed neonatally to diethylstilbestrol

The occurrence of polyovular follicles (PF) was examined at 10-34 days of age in the ovaries of BALB/cCrgl female mice given five daily injections of 0.1 microgram diethylstilbestrol (DES), 2 micrograms DES, 100 micrograms progesterone (P), 137 micrograms 17 alpha-hydroxyprogesterone caproate (HPC), 20 micrograms testosterone (T), 20 micrograms 5 alpha-dihydrotestosterone (5 alpha-DHT), or oil vehicle alone starting on the day of birth, and of C57BL/Tw females given five neonatal injections of 1 microgram DES, 20 micrograms 17 beta-estradiol (E2), 50 micrograms 5 alpha-DHT, 50 micrograms 5 beta-DHT, or the vehicle alone. Ovaries of 30-day-old C57BL mice given five daily injections of 1 microgram DES starting at 3-25 days of age were also examined. PF incidence (% of PF per ovary) and PF frequency (% of mice with PF) were significantly greater in BALB/c mice receiving injections of DES, P, HPC, and T than in the controls. In DES-treated mice at 34 days, PF incidence (2-13 oocytes/follicle) was 120-340 times higher than in the controls. BALB/c mice treated with T, P, and HPC showed PF incidence (two to four oocytes/follicle) three- to six-fold higher than in the controls. In 30-day-old C57BL mice treated with T, E2, and DES, PF incidence also increased by two- to 50-fold. 5 alpha-DHT and 5 beta-DHT failed to increase PF incidence. PF incidence was significantly increased only when neonatal DES treatment was begun on days 0 to 3, but was reduced when started at days 10-25.(ABSTRACT TRUNCATED AT 250 WORDS)

Decreased ovalbumin-gene response to oestrogen in the prenatally diethylstilboestrol-exposed chick oviduct

Prenatal exposure of the female chick-embryo Müllerian duct to diethylstilboestrol (DES) decreases its future capacity for epithelial tubular-gland-cell differentiation and oviduct ovalbumin-gene expression. Chick Müllerian ducts after prenatal exposure to different concentrations of DES were tested after birth to determine the response of the oviduct toward the oestrogen induction. The quantity of DNA was biochemically determined, the differentiation of tubular-gland cells in the oviduct was studied by light microscopy, and the expression of the ovalbumin gene was detected by hybridization of the total RNA with radioactive ovalbumin cDNA. Comparisons among these three parameters revealed that the expression of the ovalbumin gene was affected most by DES exposure. Exposure to high doses of DES suppressed ovalbumin-gene expression by 75-78%, and inhibited tubular-gland-cell differentiation and thus decreased the DNA content by 29 and 32% respectively. Exposure to low doses of DES caused suppression of ovalbumin-gene expression by 47-53%, but it did not affect the other two parameters. Prenatal DES exposure has strong inhibitory effects on the Müllerian duct at the age (5-8-day-old embryos) when the organ is undifferentiated. Less inhibition is observed when the organ becomes differentiated (15-day-old embryos and older).

Progressive proliferative changes in the oviduct of mice following developmental exposure to diethylstilbestrol

Structural malformation of the oviduct has been reported in experimental animal models and women following prenatal exposure to diethylstilbestrol (DES). To study histological changes in the oviduct in the absence of gross structural malformation, neonatal CD-1 mice were treated with DES (2 micrograms/pup/day) on days 1-5 of age. Focal epithelial hyperplasia was present at 1 month of age in 16 out of 18 (89%) of the DES-treated mice. At 4 months of age, general epithelial hyperplasia with multiple gland-like structures into and through the muscle wall of the oviduct was observed in 90% of the treated mice; by 12 months of age, epithelial hyperplasia and pseudogland formation were seen in 100% of the DES-exposed animals. Epithelial hyperplasia and gland formation were not observed in control mice. The alteration induced by DES in the differentiation and proliferation of mouse oviductal epithelium suggests that the oviduct is a target for DES toxic effects. In addition, there was a progression of the epithelial changes with age. The histological changes described in this study may be partially responsible for the decreased fertility previously reported in this mouse model. Similar changes in the oviduct of DES-exposed women remain to be determined.

The role of the estrogen receptor in diethylstilbestrol toxicity

The site and specificity of the tissue response to a toxicant are of central importance; it is in this area of diethylstilbestrol (DES) toxicity that the estrogen receptor would appear to play its primary role. Compilation of the various sites of DES toxicity in humans and experimental animals indicates that lesions appear predominantly in estrogen responsive target tissues suggesting that the presence of the estrogen receptor in such target tissues may help govern the tissue specificity of the toxic insult. DES and many of its oxidative metabolites interact with high affinity with the estrogen receptor. Such an interaction may be responsible for localizing DES to target tissues. Autoradiographic and biochemical studies have supported the localization of radiolabeled DES in susceptible tissues. The intracellular mechanism of receptor binding of DES and certain metabolites could then result in mobilization of these compounds to the nucleus. Experimental evidence has shown that DES and a number of its metabolites are able to translocate receptor to the nucleus of uterine cells. Such an action by the receptor results in an increased probability of potential chemical interactions with the genome. The actual induction of a chemical lesion in the target cell may, at this point, proceed by non-receptor mediated mechanisms. For example, studies using in vitro cell culture systems which contain no estrogen receptors have shown that DES can induce neoplastic cell transformation, mutagenesis, irreversible binding to DNA and protein and unscheduled DNA synthesis. These results raise the possibility that a part of DES toxicity may follow pharmacologic principles established for chemical carcinogens. Following induction of the molecular lesion, the role of the receptor continues in this process by mediating increased protein synthesis and mitogenesis in responsive target tissues which ultimately permits a more extensive expression of the toxic effects. It has been demonstrated that DES is a potent mitogen in vivo in both uterine and pituitary tissues, subsequently, the lesion will perpetuate itself through this receptor mediated biological response. This is particularly important since a number of DES induced reproductive tract tumors are expressed only after additional estrogen exposure. While other tumors have been shown to be estrogen sensitive and will regress without continued estrogen stimulation. Therefore, it should be considered that the presence of the estrogen receptor and the estrogen receptor mediated biological responsiveness of a particular tissue are most important in explaining the specificity of DES toxicity.