Neonatal exposure to genistein induces estrogen receptor (ER)alpha expression and multioocyte follicles in the maturing mouse ovary: evidence for ERbeta-mediated and nonestrogenic actions

Inhibition of vascular endothelial growth factor receptor signal transduction blocks follicle progression but does not necessarily disrupt vascular development in perinatal rat ovaries

We hypothesized that vascular endothelial growth factor A (VEGFA) angiogenic isoforms and their receptors, FLT1 and KDR, regulate follicular progression in the perinatal rat ovary. Each VEGFA angiogenic isoform has unique functions (based on its exons) that affect diffusibility, cell migration, branching, and development of large vessels. The Vegfa angiogenic isoforms (Vegfa_120, Vegfa_164, and Vegfa_188) were detected in developing rat ovaries, and quantitative RT-PCR determined that Vegfa_120 and Vegfa_164 mRNA was more abundant after birth, while Vegfa_188 mRNA was highest at Embryonic Day 16. VEGFA and its receptors were localized to pregranulosa and granulosa cells of all follicle stages and to theca cells of advanced-stage follicles. To determine the role of VEGFA in developing ovaries, Postnatal Day 3/4 rat ovaries were cultured with 8 muM VEGFR-TKI, a tyrosine kinase inhibitor that blocks FLT1 and KDR. Ovaries treated with VEGFR-TKI had vascular development reduced by 94% (P < 0.0001), with more primordial follicles (stage 0), fewer early primary, transitional, and secondary follicles (stages 1, 3, and 4, respectively), and greater total follicle numbers compared with control ovaries (P < 0.005). V1, an inhibitor specific for KDR, was utilized to determine the effects of only KDR inhibition. Treatment with 30 muM V1 had no effect on vascular density; however, treated ovaries had fewer early primary, transitional, and secondary follicles and more primary follicles (stage 2) compared with control ovaries (P < 0.05). We conclude that VEGFA may be involved in primordial follicle activation and in follicle maturation and survival, which are regulated through vascular-dependent and vascular-independent mechanisms.

Fetal and neonatal exposure to the endocrine disruptor methoxychlor causes epigenetic alterations in adult ovarian genes

Exposure to endocrine-disrupting chemicals during development could alter the epigenetic programming of the genome and result in adult-onset disease. Methoxychlor (MXC) and its metabolites possess estrogenic, antiestrogenic, and antiandrogenic activities. Previous studies showed that fetal/neonatal exposure to MXC caused adult ovarian dysfunction due to altered expression of key ovarian genes including estrogen receptor (ER)-beta, which was down-regulated, whereas ERalpha was unaffected. The objective of the current study was to evaluate changes in global and gene-specific methylation patterns in adult ovaries associated with the observed defects. Rats were exposed to MXC (20 microg/kgxd or 100 mg/kg.d) between embryonic d 19 and postnatal d 7. We performed DNA methylation analysis of the known promoters of ERalpha and ERbeta genes in postnatal d 50-60 ovaries using bisulfite sequencing and methylation-specific PCRs. Developmental exposure to MXC led to significant hypermethylation in the ERbeta promoter regions (P < 0.05), whereas the ERalpha promoter was unaffected. We assessed global DNA methylation changes using methylation-sensitive arbitrarily primed PCR and identified 10 genes that were hypermethylated in ovaries from exposed rats. To determine whether the MXC-induced methylation changes were associated with increased DNA methyltransferase (DNMT) levels, we measured the expression levels of Dnmt3a, Dnmt3b, and Dnmt3l using semiquantitative RT-PCR. Whereas Dnmt3a and Dnmt3l were unchanged, Dnmt3b expression was stimulated in ovaries of the 100 mg/kg MXC group (P < 0.05), suggesting that increased DNMT3B may cause DNA hypermethylation in the ovary. Overall, these data suggest that transient exposure to MXC during fetal and neonatal development affects adult ovarian function via altered methylation patterns.

The primordial pool of follicles and nest breakdown in mammalian ovaries

The creation of the pool of follicles available for selection and ovulation is a multi-faceted, tightly regulated process that spans the period from embryonic development through to the first reproductive cycle of the organism. In mice, this development can occur in mere weeks, but in humans, it is sustained for years. Embryonic germ cell development involves the migration of primordial germs cells to the genital ridge, and the mitotic division of germ cell nuclei without complete cytokinesis to form a multi-nucleated syncytia, or germ cell nest. Through combined actions of germ cell apoptosis and somatic cell migration, the germ cell nuclei are packaged, with surrounding granulosa cells, into primordial follicles to form the initial follicle pool. Though often dismissed as quiescent and possibly uninteresting, this initial follicle pool is actually quite dynamic. In a very strictly controlled mechanism, a large portion of the initial primordial follicles formed is lost by atresia before cycling even begins. Remaining follicles can undergo alternate fates of continued dormancy or selection leading to follicular growth and differentiation. Together, the processes involved in the fate decisions of atresia, sustained dormancy, or activation carve out the follicle pool of puberty, the pool of available oocytes from which all future reproductive cycles of the female can choose. The formation of the initial and pubertal follicle pools can be predictably affected by exogenous treatment with hormones or molecules such as activin, demonstrating the ways the ovary controls the quality and quantity of germ cells maintained. Here, we review the biological processes involved in the formation of the initial follicle pool and the follicle pool of puberty, address the alternate models for regulating germ cell number and outline how the ovary quality-controls the germ cells produced.

Long-term effects of environmental endocrine disruptors on reproductive physiology and behavior

It is well established that, over the course of development, hormones shape the vertebrate brain such that sex specific physiology and behaviors emerge. Much of this occurs in discrete developmental windows that span gestation through the prenatal period, although it is now becoming clear that at least some of this process continues through puberty. Perturbation of this developmental progression can permanently alter the capacity for reproductive success. Wildlife studies have revealed that exposure to endocrine disrupting compounds (EDCs), either naturally occurring or man made, can profoundly alter reproductive physiology and ultimately impact entire populations. Laboratory studies in rodents and other species have elucidated some of the mechanisms by which this occurs and strongly indicate that humans are also vulnerable to disruption. Use of hormonally active compounds in human medicine has also unfortunately revealed that the developing fetus can be exposed to and affected by endocrine disruptors, and that it might take decades for adverse effects to manifest. Research within the field of environmental endocrine disruption has also contributed to the general understanding of how early life experiences can alter reproductive physiology and behavior through non-genomic, epigenetic mechanisms such as DNA methylation and histone acetylation. These types of effects have the potential to impact future generations if the germ line is affected. This review provides an overview of how exposure to EDCs, particularly those that interfere with estrogen action, impacts reproductive physiology and behaviors in vertebrates.

Overlapping but distinct effects of genistein and ethinyl estradiol (EE(2)) in female Sprague-Dawley rats in multigenerational reproductive and chronic toxicity studies

Genistein and ethinyl estradiol (EE(2)) were examined in multigenerational reproductive and chronic toxicity studies that had different treatment intervals among generations. Sprague-Dawley rats received genistein (0, 5, 100, or 500 ppm) or EE(2) (0, 2, 10, or 50 ppb) in a low phytoestrogen diet. Nonneoplastic effects in females are summarized here. Genistein at 500 ppm and EE(2) at 50 ppb produced similar effects in continuously exposed rats, including decreased body weights, accelerated vaginal opening, and altered estrous cycles in young animals. At the high dose, anogenital distance was subtly affected by both compounds, and a reduction in litter size was evident in genistein-treated animals. Genistein at 500 ppm induced an early onset of aberrant cycles relative to controls in the chronic studies. EE(2) significantly increased the incidence of uterine lesions (atypical focal hyperplasia and squamous metaplasia). These compound-specific effects appeared to be enhanced in the offspring of prior exposed generations.

Neonatal exposure to genistein disrupts ability of female mouse reproductive tract to support preimplantation embryo development and implantation

Female mice treated neonatally with the phytoestrogen genistein (50 mg/kg/day) have multioocyte follicles, lack regular estrous cyclicity, and are infertile even after superovulation. To determine the cause of their infertility, we examined oocyte developmental competence and timing of embryo loss. Eggs obtained by superovulation of genistein-treated or control females were equally capable of being fertilized in vitro and cultured to the blastocyst stage. However, if eggs were fertilized in vivo, retrieved at the pronucleus stage, and cultured, there was a significant reduction in the percentage of embryos from genistein-treated females reaching the blastocyst stage. When these blastocysts were transferred to pseudopregnant recipients, the number of live pups produced was similar to that in controls. Preimplantation embryo development in vivo was examined by flushing embryos from the oviduct and/or uterus. Similar numbers of one-cell and two-cell embryos were obtained from genistein-treated and control females. However, significantly fewer embryos (<50%) were obtained from genistein-treated females on postcoital Days 3 and 4. To determine if neonatal genistein treatment altered the ability of the uterus to support implantation, blastocysts from control donors were transferred to control and genistein-treated pseudopregnant recipients. These experiments demonstrated that genistein-treated females are not capable of supporting normal implantation of control embryos. Taken together, these results suggest that oocytes from mice treated neonatally with genistein are developmentally competent; however, the oviductal environment and the uterus have abnormalities that contribute to the observed reproductive failure.

Suppression of Notch signaling in the neonatal mouse ovary decreases primordial follicle formation

Notch signaling directs cell fate during embryogenesis by influencing cell proliferation, differentiation, and apoptosis. Notch genes are expressed in the adult mouse ovary, and roles for Notch in regulating folliculogenesis are beginning to emerge from mouse genetic models. We investigated how Notch signaling might influence the formation of primordial follicles. Follicle assembly takes place when germ cell syncytia within the ovary break down and germ cells are encapsulated by pregranulosa cells. In the mouse, this occurs during the first 4-5 d of postnatal life. The expression of Notch family genes in the neonatal mouse ovary was determined through RT-PCR measurements. Jagged1, Notch2, and Hes1 transcripts were the most abundantly expressed ligand, receptor, and target gene, respectively. Jagged1 and Hey2 mRNAs were up-regulated over the period of follicle formation. Localization studies demonstrated that JAGGED1 is expressed in germ cells prior to follicle assembly and in the oocytes of primordial follicles. Pregranulosa cells that surround germ cell nests express HES1. In addition, pregranulosa cells of primordial follicles expressed NOTCH2 and Hey2 mRNA. We used an ex vivo ovary culture system to assess the requirement for Notch signaling during early follicle development. Newborn ovaries cultured in the presence of gamma-secretase inhibitors, compounds that attenuate Notch signaling, had a marked reduction in primordial follicles compared with vehicle-treated ovaries, and there was a corresponding increase in germ cells that remained within nests. These data support a functional role for Notch signaling in regulating primordial follicle formation.

Roles for transforming growth factor beta superfamily proteins in early folliculogenesis

Primordial follicle formation and the subsequent transition of follicles to the primary and secondary stages encompass the early events during folliculogenesis in mammals. These processes establish the ovarian follicle pool and prime follicles for entry into subsequent growth phases during the reproductive cycle. Perturbations during follicle formation can affect the size of the primordial follicle pool significantly, and alterations in follicle transition can cause follicles to arrest at immature stages or result in premature depletion of the follicle reserve. Determining the molecular events that regulate primordial follicle formation and early follicle growth may lead to the development of new fertility treatments. Over the last decade, many of the growth factors and signaling proteins that mediate the early stages of folliculogenesis have been identified using mouse genetic models, in vivo injection studies, and ex vivo organ culture approaches. These studies reveal important roles for the transforming growth factor beta (TGF-beta) superfamily of proteins in the ovary. This article reviews these roles for TGF-beta family proteins and focuses in particular on work from our laboratories on the functions of activin in early folliculogenesis.

Preputialectomised and intact adult male mice exhibit an elevated urinary ratio of oestradiol to creatinine in the presence of developing females, whilst promoting uterine and ovarian growth of these females

Exposure to novel adult males and their urine can hasten the onset of sexual maturity in female mice. Some evidence implicates chemosignals from males’ preputial glands, while other evidence suggests that male urinary steroids, especially 17β-oestradiol, contribute to this effect. The present experiment was designed to determine whether preputial gland removal would influence the capacity of males to accelerate female sexual development, and to measure male urinary oestradiol and testosterone in the presence or absence of these glands. Juvenile females aged 28 days were housed for two weeks in isolation or underneath two outbred males that had undergone preputialectomy or sham surgery. Urine samples were collected non-invasively from males that were isolated or exposed to females, then assayed for oestradiol, testosterone and creatinine. Combined uterine and ovarian mass from females sacrificed at 43 days of age was increased by exposure to males, regardless of whether or not these males had been preputialectomised. Male urinary creatinine was reduced by exposure to developing females. Creatinine-adjusted oestradiol and testosterone were significantly greater in female-exposed than in isolated males, in both preputialectomised and intact males. These data suggest that the preputials are not necessary for the capacity of males to hasten female uterine and ovarian growth. As exogenous oestrogens can promote uterine growth and other parameters of female reproductive maturation, oestradiol in males’ urine may contribute to earlier sexual maturity in male-exposed females.

Female reproductive disorders: the roles of endocrine-disrupting compounds and developmental timing

OBJECTIVE

To evaluate the possible role of endocrine-disrupting compounds (EDCs) on female reproductive disorders emphasizing developmental plasticity and the complexity of endocrine-dependent ontogeny of reproductive organs. Declining conception rates and the high incidence of female reproductive disruptions warrant evaluation of the impact of EDCs on female reproductive health.

DESIGN

Publications related to the contribution of EDCs to disorders of the ovary (aneuploidy, polycystic ovary syndrome, and altered cyclicity), uterus (endometriosis, uterine fibroids, fetal growth restriction, and pregnancy loss), breast (breast cancer, reduced duration of lactation), and pubertal timing were identified, reviewed, and summarized at a workshop.

CONCLUSION(S)

The data reviewed illustrate that EDCs contribute to numerous human female reproductive disorders and emphasize the sensitivity of early life-stage exposures. Many research gaps are identified that limit full understanding of the contribution of EDCs to female reproductive problems. Moreover, there is an urgent need to reduce the incidence of these reproductive disorders, which can be addressed by correlative studies on early life exposure and adult reproductive dysfunction together with tools to assess the specific exposures and methods to block their effects. This review of the EDC literature as it relates to female health provides an important platform on which women's health can be improved.

Effects of diethylstilbestrol on ovarian follicle development in neonatal mice

Previous results show that diethylstilbestrol (DES) causes polyovular follicles through estrogen receptor (ER) beta and increases the number of follicles, suggesting that DES might affect follicular growth and development. Effects of neonatal DES exposure on follicle development were precisely examined in the ovaries of C57BL/6J and ERbeta knockout (betaERKO) mice. In the DES-exposed C57BL/6J mice, both primary follicle (PmF) progression from primordial follicles at 5 days of age and secondary follicle (SF) progression from PmFs at 10 days of age were delayed as compared with those in the oil-exposed controls. These results indicate that DES may suppress follicle development in neonatal mouse ovaries. DES exposure also decreased the number of follicles in 5-day-old C57BL/6J, WT and betaERKO mice, suggesting that DES inhibits follicle formation and development through ERalpha in the neonatal mouse ovaries.

Disrupted female reproductive physiology following neonatal exposure to phytoestrogens or estrogen specific ligands is associated with decreased GnRH activation and kisspeptin fiber density in the hypothalamus

It is well established that estrogen administration during neonatal development can advance pubertal onset and prevent the maintenance of regular estrous cycles in female rats. This treatment paradigm also eliminates the preovulatory rise of gonadotropin releasing hormone (GnRH). It remains unclear, however, through which of the two primary forms of the estrogen receptor (ERalpha or ERbeta) this effect is mediated. It is also unclear whether endocrine disrupting compounds (EDCs) can produce similar effects. Here we compared the effect of neonatal exposure to estradiol benzoate (EB), the ERalpha specific agonist 1,3,5-tris(4-hydroxyphenyl)-4-propyl-1H-pyrazole (PPT), the ERbeta specific agonist diarylpropionitrile (DPN) and the naturally occurring EDCs genistein (GEN) and equol (EQ) on pubertal onset, estrous cyclicity, GnRH activation, and kisspeptin content in the anteroventral periventricular (AVPV) and arcuate (ARC) nuclei. Vaginal opening was significantly advanced by EB and GEN. By 10 weeks post-puberty, irregular estrous cycles were observed in all groups except the control group. GnRH activation, as measured by the percentage of immunopositive GnRH neurons that were also immunopositive for Fos, was significantly lower in all treatment groups except the DPN group compared to the control group. GnRH activation was absent in the PPT group. These data suggest that neonatal exposure to EDCs can suppress GnRH activity in adulthood, and that ERalpha plays a pivotal role in this process. Kisspeptins (KISS) have recently been characterized to be potent stimulators of GnRH secretion. Therefore we quantified the density of KISS immunolabeled fibers in the AVPV and ARC. In the AVPV, KISS fiber density was significantly lower in the EB and GEN groups compared to the control group but only in the EB and PPT groups in the ARC. The data suggest that decreased stimulation of GnRH neurons by KISS could be a mechanism by which EDCs can impair female reproductive function.

Mouse fertility is enhanced by oocyte-specific loss of core 1-derived O-glycans

Regulation of the number of eggs ovulated by different mammalian species remains poorly understood. Here we show that oocyte-specific deletion at the primary follicle stage of core 1 beta1,3-galactosyltransferase (T-synthase; generates core 1-derived O-glycans), leads to a sustained increase in fertility. T-syn mutant females ovulated 30-50% more eggs and had a sustained increase in litter size compared to controls. Ovarian weights and follicle numbers were greater in mutants, but follicular apoptosis was not decreased. The number of follicles entering the growing pool was unaltered, but 3-wk mutants ovulated fewer eggs, suggesting that increased fertility results from prolonged follicle development. T-syn mutant ovaries also contained numerous multiple-oocyte follicles (MOFs) that appeared to form by adjacent, predominantly preantral, follicles joining--a new mechanism for MOF generation. Ovulation of multiple eggs from MOFs was not the reason for increased fertility based on ovulated egg and corpora lutea numbers. Thus, the absence of T-synthase caused modified follicular development, leading to the maturation and ovulation of more follicles, to MOF formation at late stages of folliculogenesis, and to increased fertility. These results identify novel roles for glycoproteins from the oocyte as suppressors of fertility and regulators of follicular integrity in the mouse.

Expression profiling of a high-fertility mouse line by microarray analysis and qPCR

Background

In a recent study it was demonstrated that a largely increased ovulation number is responsible for high prolificacy in two mouse lines selected for fertility performance. The objective of the present study was to identify genes that are involved in increasing the ovulation number in one of these lines, FL1. For differential expression profiling, ovaries of FL1 and of a non-selected control line, DUKsi, both lines derived from the same genetic pool, were analyzed with microarray analysis and quantitative polymerase chain reaction (qPCR). Ovaries from 30 animals of each line were collected at the metestrous stage, combined to 6 pools each, and processed for microarray analysis.

Results

The actual number of ova shed in FL1 exceeded that of the DUKsi control line more than twofold (26.6 vs. 12.9). 148 differentially expressed ovarian transcripts could be identified, 74 of them up- and 74 down-regulated. Of these, 47 significantly mapped to specific Gene Ontology (GO) terms representing different biological processes as steroid metabolism, folliculogenesis, immune response, intracellular signal transduction (particularly of the G protein signaling cascade), regulation of transcription and translation, cell cycle and others. qPCR was used to re-evaluate selected transcripts and to estimate inter-individual variation of expression levels. These data significantly correlated with microarray data in 12 out of 15 selected transcripts but revealed partly large variations of expression levels between individuals.

Conclusion

(1) The abundance of numerous ovarian transcripts was significantly different in FL1 compared to the non-selected control line DUKsi thus suggesting that at least some of the respective genes and corresponding biological processes are involved in improving reproductive traits, particularly by increasing the number of ovulation. (2) Selective qPCR re-evaluation largely confirmed the microarray data and in addition demonstrated that sample pooling can be beneficial to find out group-specific expression profiles despite of large inter-individual variation. (3) The present data will substantially help ongoing genetic association studies to identify candidate genes and causative mutations responsible for increased fertility performance in mice.

Developmental exposure to endocrine disruptor chemicals alters follicular dynamics and steroid levels in Caiman latirostris

Human and wildlife are exposed at critical periods of development to endocrine disruptor chemicals (EDC) that may be responsible for reproductive disorders. To test the hypothesis that in ovum exposure to EDC at a critical period for gonadal organogenesis alters post-hatching folliculogenesis and steroidogenesis in Caiman latirostris, we studied the impact of in ovum exposure to 17 beta-estradiol (E2), bisphenol A (BPA), endosulfan (END) and atrazine (ATZ) on gonadal differentiation, follicular dynamics and circulating levels of steroid hormones in neonatal and juvenile caiman. Since C. latirostris is a species with temperature dependent sex determination, eggs were incubated at male (33 degrees C) or female (30 degrees C) producing temperatures and the effect of EDC was evaluated. Neonatal ovaries exhibited germ cells mainly located in clusters evidencing proliferative activity and type I to III follicles. Juvenile ovaries exhibited germ cells and advanced stages of pre-vitellogenic follicles. Prenatal exposure to the highest doses of E2 (1.4 ppm) or BPA (140 ppm) overrode male temperature effect on sex determination. Neonatal females produced by sex reversion lacked type III follicles, while females prenatally exposed to the lowest doses of E2 (0.014 ppm) and BPA (1.4 ppm) or ATZ (0.2 ppm) showed an increase in type III follicles. Juvenile caiman prenatally exposed to E2 or BPA showed an augmented incidence of multioocyte follicles. Neonatal female caiman exposed in ovum to E2 or BPA had higher estrogen serum levels whereas exposure to E2, BPA, ATZ and END decreased T levels. Present data demonstrates that exposure to EDC during gonadal organogenesis alters follicular dynamics and steroid levels later in life. These effects might have an impact on caiman fertility.

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.

Fetal and early postnatal environmental exposures and reproductive health effects in the female

This short review presents current research into the role of the environment in normal female reproductive function and pathogenesis, specifically focusing on the ovary and uterus.

Breast development in the first 2 years of life: an association with soy-based infant formulas

OBJECTIVE

To evaluate the estrogenic effect of soy-based formulas in female infants. These formulas contain significant amounts of phytoestrogens, compounds with structural similarity to estradiol.

PATIENTS AND METHODS

A cross-sectional study consisting of 694 female infants ages 3 to 24 months that consecutively attended 10 general pediatric clinics, none of them having been referred for breast development. The presence of breast buds served as a marker for the endocrine effect of soy-derived phytoestrogens.

RESULTS

Of the participants, 92 had consumed soy formulas for more than 3 months. Breast tissue was more prevalent in the second year of life in infants fed soy-based formula vs those that were breast-fed and those fed dairy-based formula (22.0% vs 10.3%; P = 0.02) with an odds ratio of 2.45 (95% confidence interval 1.11-5.39). No differences in breast bud prevalence were observed during the first year of life. Unlike infants on dairy-based formulas and breast-feeding, infants fed a soy-based formula did not demonstrate a decline in the prevalence of breast during the second year of life.

CONCLUSIONS

We suggest that phytoestrogens impose a preserving effect on breast tissue that is evolved in early infancy, leading eventually to a slower waning of infantile breast tissue.

The onset of puberty in female mice as reflected in urinary steroids and uterine/ovarian mass: interactions of exposure to males, phyto-oestrogen content of diet, and ano-genital distance

Development of puberty in female mice was examined in relationship with the ano-genital distance index (AGDI), phyto-oestrogen content of diet and exposure to males post weaning. Throughout gestation and post-natal development, females were exposed to a regular diet or a nutritionally similar diet deficient in phyto-oestrogens. After segregation at weaning on the basis of short or long AGDI, an indirect measure ofin uteroandrogen exposure, females were housed alone or underneath two outbred adult males for 2 weeks. Female urinary samples were collected non-invasively throughout this exposure, then assayed for oestradiol, progesterone and creatinine. Females were then killed and uterine and ovarian mass was determined. Urinary oestradiol was substantially reduced in females raised on the phyto-oestrogen-free diet. Oestradiol levels were more dynamic over days in urine of male-exposed females, especially among those on the regular diet. Urinary progesterone was not strongly influenced by diet. Progesterone was more dynamic in urine of male-exposed females, and was generally elevated compared with levels in isolated females, the size of this effect dependent on AGDI, diet and whether the measure was adjusted for creatinine. Urinary creatinine was elevated by the phyto-oestrogen-free diet and reduced by male exposure, tending to decline over days in females exposed to males. Male exposure increased uterine and ovarian mass and was influenced by AGDI in interaction with diet and male exposure.

Neonatal exposure to estradiol valerate programs ovarian sympathetic innervation and follicular development in the adult rat

A single injection of estradiol valerate (EV) to 14-day-old rats (when the ovarian follicle population has been already established) disrupts cyclicity, increases the activity of key enzymes of androgen biosynthesis, and develops polycystic ovary by a causally related increase in ovarian noradrenaline (NA). The current study examined an early window of ovarian development to look for a specific stage of development at which estradiol can induce such changes in sympathetic activity and follicular development. A single dose of EV applied to rats before the first 12 h of life rapidly increases (after 24 h) the ovarian expression of nerve growth factor (Ngfb) and p75 low-affinity neurotrophic receptor (Ngfr) mRNAs. When adults, rats presented early vaginal opening, disrupted cyclicity, appearance of follicular cyst, absence of corpus luteum, and infertility. Total follicles decreased, mainly due to a reduced number of primordial follicles, suggesting that estradiol acts in the first stages of folliculogenesis, when primordial follicles are organizing. These changes paralleled a 6-fold increase in NA concentration. No changes in NA content were found in the celiac ganglia, suggesting a local, non-centrally mediated effect of estradiol. Surgical section of the superior ovarian nerve (the main source of sympathetic nerves to the ovary) to rats neonatally treated with EV decreased intraovarian NA, delayed vaginal opening, and blocked the development of follicular cyst and that of preovulatory follicles. Therefore, we can conclude that early exposure to estradiol permanently modifies ovarian sympathetic activity and causes profound changes in follicular development, leading to the polycystic ovary condition.

Estradiol, progesterone, and genistein inhibit oocyte nest breakdown and primordial follicle assembly in the neonatal mouse ovary in vitro and in vivo

In developing mouse ovaries, oocytes develop as clusters of cells called nests or germ cell cysts. Shortly after birth, oocyte nests dissociate and granulosa cells surround individual oocytes forming primordial follicles. At the same time, two thirds of the oocytes die by apoptosis, but the link between oocyte nest breakdown and oocyte death is unclear. Although mechanisms controlling breakdown of nests into individual oocytes and selection of oocytes for survival are currently unknown, steroid hormones may play a role. Treatment of neonatal mice with natural or synthetic estrogens results in abnormal multiple oocyte follicles in adult ovaries. Neonatal genistein treatment inhibits nest breakdown suggesting multiple oocyte follicles are nests that did not break down. Here we investigated the role of estrogen signaling in nest breakdown and oocyte survival. We characterized an ovary organ culture system that recapitulates nest breakdown, reduction in oocyte number, primordial follicle assembly, and follicle growth in vitro. We found that estradiol, progesterone, and genistein inhibit nest breakdown and primordial follicle assembly but have no effect on oocyte number both in organ culture and in vivo. Fetal ovaries, removed from their normal environment of high levels of pregnancy hormones, underwent premature nest breakdown and oocyte loss that was rescued by addition of estradiol or progesterone. Our results implicate hormone signaling in ovarian differentiation with decreased estrogen and progesterone at birth as the primary signal to initiate oocyte nest breakdown and follicle assembly. These findings also provide insight into the mechanism of multiple oocyte follicle formation.

Disruption of the developing female reproductive system by phytoestrogens: Genistein as an example

Studies in our laboratory have shown that exposure to genistein causes deleterious effects on the developing female reproductive system. Mice treated neonatally on days 1-5 by subcutaneous injection of genistein (0.5-50 mg/kg) exhibited altered ovarian differentiation leading to multioocyte follicles (MOFs) at 2 months of age. Ovarian function and estrous cyclicity were also disrupted by neonatal exposure to genistein with increasing severity observed over time. Reduced fertility was observed in mice treated with genistein (0.5, 5, or 25 mg/kg) and infertility was observed at 50 mg/kg. Mammary gland and behavioral endpoints were also affected by neonatal genistein treatment. Further, transgenerational effects were observed; female offspring obtained from breeding genistein treated females (25 mg/kg) to control males had increased MOFs. Thus, neonatal treatment with genistein at environmentally relevant doses caused adverse consequences on female development which is manifested in adulthood. Whether adverse effects occur in human infants exposed to soy-based products such as soy infant formulas is unknown but the neonatal murine model may help address some of the current uncertainties since we have shown that many effects obtained from feeding genistin, the glycosolated form of genistein found in soy formula, are similar to those obtained from injecting genistein.

Exposure of adult rats to estradiol valerate induces ovarian cyst with early senescence of follicles

Environmental and therapeutic estrogens are known to play an important role in modulating the reproductive life and pubertal maturation in males as well as in females. Animal studies have shown that exogenously administered estrogen induces follicular cysts. However, the probable mechanisms underlying this abnormal ovarian development and its impact on steroidogenesis have been ill defined. The present study was therefore carried out to understand the ontogeny of ovarian pathology owing to adult estrogenisation. Regularly cycling female Holtzman rats were sacrificed at one week, two weeks, three weeks and four weeks after a subcutaneous administration of 2 mg of estradiol valerate (E(2)V). The effect of this supra-physiological estrogen on serum endocrine profiles, development of follicular cysts, follicular apoptosis and expression of markers of folliculogenesis viz., estrogen receptor (ER)-beta, inhibin A and progesterone receptor (PR) were studied. Results indicate a temporal augmentation of steroidogenesis, which was associated with induction of follicular cyst with theca cell hyperplasia and induction of apoptosis in the primary and secondary follicles of the ovaries. Immuno-histochemical localization showed an increase in inhibin A with a reduction in ER-beta and PR indicating early maturation, poor follicle growth and granulosa cell differentiation. Results indicate that exposure to exogenous estrogen in adulthood can have deleterious effects on the ovarian physiology and endocrinology which may ultimately lead to cystogenesis, loss of follicle pool and early senescence.

Specificity of the requirement for Foxo3 in primordial follicle activation

Primordial follicles are long-lived structures assembled early in life. The mechanisms that control the balance between the conservation and the activation of primordial follicles are critically important for fertility and dictate the onset of menopause. The forkhead transcription factor Foxo3 serves an essential role in these processes by suppressing the growth of primordial follicles, thereby preserving them until later in life. While other factors regulating primordial follicle growth have been described, most serve multiple functions at several stages of female germ cell or follicle development, and corresponding mouse mutants exhibit pleiotropic phenotypes with disruption of multiple stages of follicle assembly, development, or survival. To investigate the possibility that Foxo3 also functions in other aspects of ovarian development beyond its known role in primordial follicle activation (PFA), we performed detailed analyses of mouse ovaries including electron microscopy to study primordial follicle structure, assembly, and early growth. These analyses revealed that the timing of primordial follicle assembly, early oocyte survival, and the expression of early germ line markers were unaffected in early Foxo3 ovaries. Taken together, these studies demonstrate that the phenotype associated with Foxo3 deficiency is remarkably specific for PFA and further support the placement of Foxo3 in a unique phenotypic class among mammalian female sterile mutants. Lastly, we discuss the implications of the specificity of this mutant phenotype with regard to the hypothesis that oocyte regeneration may occur in adults and serves as a means to replenish oocytes lost via natural physiological processes.

Neonatal exposure to estrogens suppresses activin expression and signaling in the mouse ovary

In the ovary, the steroid hormone estrogen and the TGF-beta superfamily member activin are both produced by granulosa cells and they both have intraovarian functions. Emerging evidence has indicated an interaction of these two signaling pathways. Based on the fact that estrogen and activin can impact early follicle formation and development, we hypothesize that estrogen treatment may alter activin signaling in the neonatal ovary. Therefore, this study was designed to examine the effect of neonatal diethylstilbestrol (DES) and estradiol (E(2)) exposure on the mRNA and protein levels of the key factors involved in activin signaling in the mouse ovary. CD-1 mouse pups were given daily injections of DES, E(2), or oil on postnatal d 1-5, and ovaries and sera were collected on d 19. Neonatal DES or E(2) exposure decreased the number of small antral follicles, induced multioocytic follicle formation, and decreased activin beta-subunit mRNA and protein levels. Consistent with local loss of beta-subunit expression, the phosphorylation of Smad 2, a marker of activin-dependent signaling, was decreased in the estrogen-treated ovaries. The decreased beta-subunit expression resulted in a decrease in serum inhibin levels, with a corresponding increase in FSH. Estrogen also suppressed activin subunit gene promoter activities, suggesting a direct transcriptional effect. Overall, this study demonstrates that activin subunits are targets of estrogen action in the early mouse ovary.

Lindane may modulate the female reproductive development through the interaction with ER-beta: an in vivo-in vitro approach

Lindane (gamma-HCH) is a persistent environmental pollutant that may act as endocrine disrupter, affecting the nervous, immune and reproductive system, possibly through endocrine-mediated mechanisms. Since both estrogen receptors (ER-alpha and -beta) have shown to be target for endocrine disruption, we investigated the role of gamma-HCH on the development of female reproductive system. For an in vivo evaluation of gamma-HCH effects during prenatal period, pregnant CD1 mice were treated p.o. on gestational days 9-16 with 15 mg/kg bw/day of gamma-HCH and vehicle. The in vivo findings in treated F1 pups - in the absence of signs of systemic toxicity - included increase in the absolute and relative and absolute uterus weight revealed on post-natal day 22, earlier vaginal patency and reduced diameters of primary oocytes at fully sexual maturity. No effects on steroid hormone metabolism (aromatase, testosterone catabolism) were observed. Thus, gamma-HCH elicited subtle effects on female reproductive development likely mediated by ER-beta-mediated pathway(s), without a concurrent impairment of steroid hormone metabolism. Furthermore, to verify whether the endocrine interference of gamma-HCH is attributable to stimulation of ER-beta-mediated pathway(s), its effect has been evaluated in vitro on a cell line, LNCaP, expressing only functional ER-beta. In vitro treatments revealed a concentration-related effect on LNCaP cell viability and proliferation. Significantly, the contemporary addition of a pure anti-estrogen, the ER antagonist ICI 182,780, completely reversed gamma-HCH effects indicating an ER-beta-mediated action. Our findings indicate that gamma-HCH may act as endocrine disruptor during the female reproductive system development and ER-beta as a potential target for this compound and other endocrine disrupting chemicals as well.

[High intake of phytoestrogens and precocious thelarche: case report with a possible correlation]

Precocious thelarche is the breast development before 8 years of age with two peaks of incidence during the first two years of life and after 6 years of age. A 4.75-year-old girl presented with thelarche associated to an excessive intake of phytoestrogens (phye). Tanner development B2P1-2, hormonal levels and pelvic US were compatible with peripheral precocious puberty. During follow-up, a daily intake of soy-based foods was observed (> 40 mg phye/day). Soy is rich in phytoestrogens, mainly genistein and daidzein. Although phye are less strong than estradiol, its concentration could be from 13,000 to 22,000 times stronger in children fed only by soy-based formulas. Parents were advised and soy intake was reduced to once a week. Progression of pubertal development ceased at B2-3P1. The patient, now 8.66 years old, keeps growing with similar bone and chronological ages. Some questions related to industrial food security, mainly the soy-based food, remain without precise answer. Although it is well known the entity of non-progressive precocious puberty and premature thelarche, pubertal development in this case was strongly related to excessive daily intake of soy and other phye-rich food that could trigger puberty as endocrine disruptor.

Dietary isoflavones act on bone marrow osteoprogenitor cells and stimulate ovary development before influencing bone mass in pre-pubertal piglets

Food containing soybeans provide isoflavone phytoestrogens that can preserve bone mass in postmenopausal women, and prevent bone loss in ovariectomized rats. But their effects on bone remain unclear, particularly on bone formation during growth. Two groups of eight pre-pubertal piglets were fed a basal or an isoflavone-enriched (S800) diet for 6 weeks. The S800 diet contained 800 mg SoyLifetrade mark/kg, providing 2.8 mg isoflavones/kg body weight/day. Several bones were collected and tested for bone strength and density. Bone marrow was collected from humeri together with blood samples and genital tracts. The plasma concentrations of isoflavones were increased in the pigs fed S800, but growth rate, body weight, plasma bone markers, bone mineral density, and strength were all unaffected. In contrast, cultured stromal cells from S800 pigs had more alkaline phosphatase-rich cells and mineralized nodules, secreted more osteocalcin, osteoprotegerin and RANK-L, synthesized more osteoprotegerin, and RANK-L. Cultured mononucleated nonadherent bone marrow cells from S800 pigs developed fewer tartrate-resistant acid phosphatase mononucleated cells (osteoclast progenitors) when cultured with 1,25(OH)(2)D(3), and resorbed a smaller area of dentine slices. Freshly isolated bone marrow osteoclast progenitors from S800 pigs had more caspase-3 cleavage activity, and synthesized less RANK. Both osteoclast and osteoblast progenitors had ERalpha and ERbeta, whose syntheses were stimulated by the S800 diet. The S800 piglets had heavier ovaries with more follicles, but their uterus weight was unaffected. We conclude that dietary isoflavones have no detectable effect on the bone mass of growing female piglets, but act on bone marrow osteoprogenitors via ERs--mainly ERbeta, and stimulate ovary development.

From primordial germ cell to primordial follicle: mammalian female germ cell development

In mammals, the final number of oocytes available for reproduction of the next generation is defined at birth. Establishment of this oocyte pool is essential for fertility. Mammalian primordial germ cells form and migrate to the gonad during embryonic development. After arriving at the gonad, the germ cells are called oogonia and develop in clusters of cells called germ line cysts or oocyte nests. Subsequently, the oogonia enter meiosis and become oocytes. The oocyte nests break apart into individual cells and become packaged into primordial follicles. During this time, only a subset of oocytes ultimately survive and the remaining immature eggs die by programmed cell death. This phase of oocyte differentiation is poorly understood but molecules and mechanisms that regulate oocyte development are beginning to be identified. This review focuses on these early stages of female germ cell development.

Effect of neonatal exposure to genistein on bone metabolism in mice at adulthood

Infants fed soy-based infant formulas are exposed to high levels of genistein, an isoflavone, with potential estrogen-like activity. This study determined whether neonatal exposure of mice to genistein resulted in higher bone mineral density (BMD) and greater resistance to fracture at adulthood. Male and female CD-1 mice (n = 4-14/group) were randomized to control (CON) (corn oil, s.c.), diethylstilbestrol (DES) (2 microg/pup/d, s.c.), or genistein (GEN) (4 microg/pup/d, s.c.) from d 1 through 5 of life. At 21 d of age, pups were weaned and studied until 4 mo of age when tissues were collected. Among females, femur (p = 0.016) and lumbar vertebrae (LV1-LV4) (p < 0.001) BMD were higher among DES and GEN groups compared with CON group. Importantly, the higher LV1-LV4 BMD was associated with stronger vertebrae that were more resistant to fracture as the peak load of LV3 (p = 0.012) was higher in the GEN and DES groups compared with CON group. In males, DES and GEN had divergent effects on femur and lumbar vertebrae BMD and peak load. In conclusion, early exposure to GEN has positive effects on femur and lumbar spine of females, likely due to estrogenic effects, while only the lumbar spine of males benefits from early exposure to GEN.

Two high-fertility mouse lines show differences in component fertility traits after long-term selection

Two selected high-fertility mouse lines, namely FL1 and FL2, and a non-selected control (Fzt:DU), all derived from the same genetic pool, were analysed as an animal model for polytocous species to elucidate the effects of long-term selection and to identify relevant component traits that may be responsible for fertility performance. The index trait used for breeding selection was largely increased by 104% and 142% in the FL1 and FL2 lines, respectively, resulting in an average litter size of 17.3 pups and 18.7 pups per litter in the FL1 and FL2 lines, respectively, compared with a litter size of 11.0 pups per litter in the control (Fzt:DU). In addition, different component fertility traits were analysed in females of all three lines at different stages of the oestrous cycle and pregnancy. In conclusion: (1) early embryonic development was accelerated in the FL1 and FL2 lines compared with control; (2) plasma progesterone levels were not correlated with fertility performance; (3) a largely increased ovulation number (i.e. number of corpora lutea) was responsible for high prolificacy in both lines; however, (4) the number of ova shed, as well as the rate of loss of ova and pre- and postimplantation conceptuses, was very different in the FL1 and FL2 lines, suggesting that different genetic components may be responsible for the high prolificacy in both high-fertility lines.

Effect of exposure to high isoflavone-containing diets on prenatal and postnatal offspring mice

Isoflavone (IF), a type of phytoestrogen, has multiple beneficial effects, but too much phytoestrogen can have adverse effects on offspring. To examine whether chronic exposure to high IF has adverse effects on reproductive development, mice offspring were exposed to IF through dietary administration to dams during pregnancy and lactation and to the offspring directly after weaning until sacrifice. In male offspring, there was no difference between the IF group and controls; however, in female offspring in the IF group, remarkably earlier puberty and induction of multioocyte follicles on postnatal day (PND) 21 were observed. Gene expression levels of estrogen receptor beta decreased in the ovary and vagina on PND 21. These results suggest that chronic exposure to higher than normal levels of IF induces alterations in the reproductive development of female mice through an estrogenic effect.

Neonatal exposure to the phytoestrogen genistein alters mammary gland growth and developmental programming of hormone receptor levels

Developmental effects of genistein (Gen) on the mammary gland were investigated using outbred female CD-1 mice treated neonatally on d 1-5 by sc injections at doses of 0.5, 5, or 50 mg/kg.d. Examination of mammary gland whole mounts (no. 4) before puberty (4 wk) revealed no morphological differences in development after Gen treatment. However, mice treated with Gen-50 had stunted development characterized by less branching at 5 wk and decreased numbers of terminal end buds at 5 and 6 wk. Conversely, at 6 wk, Gen-0.5-treated mice exhibited advanced development with increased ductal elongation compared with controls. Measurements of hormone receptor levels showed increased levels of progesterone receptor protein and estrogen receptor-beta mRNA in Gen-0.5-treated mice compared with controls; ERalpha expression was decreased after all doses of Gen treatment. Lactation ability, measured by pup weight gain and survival, was not affected after neonatal Gen-0.5 and Gen-5. Mice treated with Gen-50 did not deliver live pups; therefore, lactation ability could not be determined. Evaluation of mammary glands in aged mice (9 months) showed no differences between Gen-0.5-treated mice and controls but mice treated with Gen-5 and Gen-50 exhibited altered morphology including reduced lobular alveolar development, dilated ducts, and focal areas of "beaded" ducts lined with hyperplastic ductal epithelium. In summary, neonatal Gen exposure altered mammary gland growth and development as well as hormone receptor levels at all doses examined; higher doses of Gen led to permanent long-lasting morphological changes.

Endocrine-disrupting chemicals use distinct mechanisms of action to modulate endocrine system function

The term endocrine-disrupting chemicals is used to define a structurally diverse class of synthetic and natural compounds that possess the ability to alter various components of the endocrine system and potentially induce adverse health effects in exposed individuals and populations. Research on these compounds has revealed that they use a variety of both nuclear receptor-mediated and non-receptor-mediated mechanisms to modulate different components of the endocrine system. This review will describe in vitro and in vivo studies that highlight the spectrum of unique mechanisms of action and biological effects of four endocrine-disrupting chemicals--diethylstilbestrol, genistein, di(n-butyl)phthalate, and methoxyacetic acid--to illustrate the diverse and complex nature of this class of compounds.

Folliculogenesis in the domestic cat (Felis catus)

The dynamic regulation of mammalian folliculogenesis is a key component of the reproductive process. Traditionally, the rodent had been used as a model to study ovarian function and reproductive physiology due to the availability of animals, their relatively short cycle length, high rate of fecundity and short generation interval. We maintain that much basic information can be determined using domestic cat ovaries retrieved from local veterinary clinics following routine spaying, without having the expense of maintaining a colony of laboratory cats. Studies of normal feline reproductive physiology and advances in reproductive technology may be extrapolated for use in endangered non-domestic felids. Increased understanding of feline reproduction will be beneficial to veterinary medicine, and to groups working to control feral cat populations. It is important to examine reproductive mechanisms in alternative animal models as there are a vast number of threatened and endangered species in which we lack the critical reproductive information needed to assist in preserving their long-term survival.

Soy isoflavones and bone health: a double-edged sword?

Numerous publications and research studies on isoflavones have prompted a nationwide increase in the consumption of soy-based foods and supplements in the United States. Isoflavones are natural endocrine active compounds generally considered to promote health and prevent or slow the onset of certain chronic diseases such as osteoporosis. The beneficial effects of soy isoflavones on bone may, however, be life-stage specific and dependent on the estrogen receptor number and endogenous hormone milieu. Perimenopausal and early menopausal women may therefore be more receptive to the therapeutic effects of isoflavones on bone loss prior to the diminution of estrogen receptors that occurs in the postmenopausal years, whereas laboratory studies in developmental age range animals have demonstrated the potential for adverse effects following exposure to high levels of soy isoflavones. Clinical studies in developing humans that either support or refute findings in animal studies are lacking. The effects of chronic consumption of high levels of soy isoflavones at each life stage to assess risk-benefit ratios should be a high priority of research.

Neonatal Genistein Treatment Alters Ovarian Differentiation in the Mouse: Inhibition of Oocyte Nest Breakdown and Increased Oocyte Survival1

Early in ovarian differentiation, female mouse germ cells develop in clusters called oocyte nests or germline cysts. After birth, mouse germ cell nests break down into individual oocytes that are surrounded by somatic pregranulosa cells to form primordial follicles. Previously, we have shown that mice treated neonatally with genistein, the primary soy phytoestrogen, have multi-oocyte follicles (MOFs), an effect apparently mediated by estrogen receptor 2 (ESR2, more commonly known as ERbeta). To determine if genistein treatment leads to MOFs by inhibiting breakdown of oocyte nests, mice were treated neonatally with genistein (50 mg/kg per day) on Days 1-5, and the differentiation of the ovary was compared with untreated controls. Mice treated with genistein had fewer single oocytes and a higher percentage of oocytes not enclosed in follicles. Oocytes from genistein-treated mice exhibited intercellular bridges at 4 days of age, long after disappearing in controls by 2 days of age. There was also an increase in the number of oocytes that survived during the nest breakdown period and fewer oocytes undergoing apoptosis on Neonatal Day 3 in genistein-treated mice as determined by poly (ADP-ribose) polymerase (PARP1) and deoxynucleotidyl transferase mediated deoxyuridine triphosphate nick end-labeling (TUNEL). These data taken together suggest that genistein exposure during development alters ovarian differentiation by inhibiting oocyte nest breakdown and attenuating oocyte cell death.

Kinetics of genistein and its conjugated metabolites in pregnant Sprague-Dawley rats following single and repeated genistein administration

Diets high in soy-based products are well known for their estrogenic activity. Genistein, the predominant phytoestrogen present in soy, is known to interact with estrogen receptors (ER) alpha and beta and elicits reproductive effects in developing rodents. In the rat, genistein is metabolized predominantly to glucuronide and sulfate conjugates, neither of which is capable of activating ER. Therefore, it is critical to understand the delivery of free and conjugated genistein across the placenta to the fetus following maternal genistein exposure such that the potential fetal exposure to free genistein can be assessed. Genistein (4 or 40 mg/kg) was administered to pregnant Sprague-Dawley rats by oral gavage daily from gestation day (GD) 5 through 19 or on GD 19 alone. Maternal and GD 19 fetal tissues were collected 0.5, 1, 2, 4, 6, 8, 12, and 24 h following administration of the final dose on GD 19. Concentrations of genistein, genistein glucuronide, and genistein sulfate were quantitated by LC-MS/MS. In maternal plasma, genistein glucuronide was the predominant metabolite. In the fetal plasma, genistein glucuronide and genistein sulfate were the primary metabolites. Genistein levels in maternal and fetal plasma were much lower than its conjugates. The concentration of genistein in placental tissue was higher than either conjugate. Fetal concentrations of unconjugated genistein following administration of 40 mg/kg were above the EC50 for ERbeta activation. Repeated administration of 40 mg/kg genistein resulted in minor changes in genistein kinetics in the pregnant rat compared to single administration of the same dose. These data suggest that conjugated forms of genistein are not transported across the placenta. High placental concentrations of genistein indicate the placenta is a potential target organ for genistein action during gestation.

The development of a mouse model of ovarian endosalpingiosis

Pelvic pain is a common presenting ailment in women often linked to ovulation, endometriosis, early pregnancy, ovarian cancer, and cysts. Clear differential diagnosis for each condition caused by these varied etiologies is difficult and may slow the delivery of therapy that, in the case of ovarian cancer, could be fatal. Ovarian endosalpingiosis, a pelvic condition typified by the presence of cystic glandular structures lined by benign tubal/salpingeal epithelium, is also associated with pelvic pain in women. The exact cellular antecedents of these epithelial lined cystic structures are not known, nor is there a known link to ovarian cancer. A mouse model of ovarian endosalpingiosis has been developed by directing a dominant-negative version of the TGF-beta transcription factor, Smad2, to the ovary using the Müllerian-inhibiting substance promoter (MIS-Smad2-dn). Female mice develop an ovarian endosalpingeal phenotype as early as 3 months of age. Importantly, cysts continuous with the ovarian surface epithelial have been identified, indicating that these cyst cells may be derived from the highly plastic ovarian surface epithelial cell layer. A second transgenic mouse model that causes loss of activin action (inhibin alpha-subunit transgenic mice) develops similar cystic structures, supporting a TGF-beta/activin/Smad2 dependence in the onset of this disease.

Lactational transfer of the soy isoflavone, genistein, in Sprague-Dawley rats consuming dietary genistein

Exposures of Sprague-Dawley rats to the soy isoflavone, genistein, throughout the entire lifespan have produced a number of effects on reproductive tissues, immune function, neuroendocrine function and behavior. Our previous studies investigated pharmacokinetics and disposition of genistein during adult and fetal periods and this study describes the internal exposures of post-natal day 10 (PND10) rat pups due to lactational transfer of genistein. Conjugated and aglycone forms of genistein were measured by using LC/MS/MS in serum (PND10) and milk (PND7) from lactating dams consuming a genistein-fortified soy-free diet, and in serum from their pups at a time when milk was the only food source (PND10). This study shows that limited lactational transfer of genistein to rat pups occurs and that internal exposures to the active aglycone form of genistein are generally lower than those measured previously in the fetal period. These results suggest that developmental effects attributable to genistein exposure in our chronic and multi-generation studies are more likely to result from fetal exposures because of the higher levels of the active estrogenic aglycone form of genistein in utero, although the possibility of neonatal responses cannot be excluded.

Uterine phenotype of young adult rats exposed to dietary soy or genistein during development

Dietary soy intake is associated with protection from breast cancer, but questions persist on the potential risks of the major soy isoflavone genistein (GEN) on female reproductive health. Here, we evaluated intermediate markers of cancer risk in uteri of cycling, young adult Sprague-Dawley rats lifetime exposed to one of three AIN-93G semipurified diets: casein (CAS), soy protein isolate (SPI+ with 276 mg GEN aglycone equivalents/kg) and CAS+GEN (GEN at 250 mg/kg). Postnatal day 50 (PND50) rats lifetime exposed to GEN or SPI+ had similar uterine luminal epithelium height, myometrial thickness, endometrial gland numbers, endometrial immunoreactive proliferating cell nuclear antigen (PCNA), and serum estrogen and progesterone, as CAS-fed rats. GEN-fed rats showed modestly increased apoptosis in uterine glandular epithelium, compared to those of CAS- or SPI+-fed groups. Diet had no effect on the uterine expression of genes for the tumor suppressors PTEN, p53 and p21, and the apoptotic-associated proteins Bcl2, Bax and progesterone receptor. Uterine tissue and serum concentrations of total GEN were higher in rats fed GEN than in those fed SPI+. Human Ishikawa endocarcinoma cells treated with GEN-fed rat serum tended to exhibit increased apoptotic status than those treated with CAS-fed rat serum. Exogenously added GEN (0.2 and 2 microM) increased, while estradiol-17beta (0.1 microM) decreased Ishikawa cell apoptosis, relative to untreated cells. Results suggest that lifetime dietary exposure to soy foods does not alter uterine cell phenotype in young adult rats, while GEN, by enhancing uterine endometrial glandular apoptosis in vivo and in vitro, may confer protection against uterine carcinoma. Given its limited influence on uterine phenotype of young adult females, GEN, when taken as part of soy foods or as supplement, should be favorably considered for other potential health benefits.