Long-Term Changes in Ovarian Follicles of Gilts Exposed Neonatally to Methoxychlor: Effects on Oocyte-Derived Factors, Anti-Müllerian Hormone, Follicle-Stimulating Hormone, and Cognate Receptors.

In this paper, we investigated the effects of neonatal exposure to methoxychlor (MXC), a synthetic organochlorine used as an insecticide with estrogenic, antiestrogenic, and antiandrogenic activities on ovarian follicles of adult pigs. Piglets were injected with MXC (20 µg/kg body weight) or corn oil (controls) from postnatal Day 1 to Day 10 (n = 5 per group). Then, mRNA expression, protein abundance and immunolocalization of growth and differentiation factor 9 (GDF9), bone morphogenetic protein 15 (BMP15), anti-Müllerian hormone (AMH) and cognate receptors (ACVR1, BMPR1A, BMPR1B, TGFBR1, BMPR2, and AMHR2), as well as FSH receptor (FSHR) were examined in preantral and small antral ovarian follicles of sexually mature gilts. The plasma AMH and FSH levels were also assessed. In preantral follicles, neonatal exposure to MXC increased GDF9, BMPR1B, TGFBR1, and BMPR2 mRNAs, while the levels of AMH and BMP15 mRNAs decreased. In addition, MXC also decreased BMP15 and BMPR1B protein abundance. Regarding small antral follicles, neonatal exposure to MXC upregulated mRNAs for BMPR1B, BMPR2, and AMHR2 and downregulated mRNAs for AMH, BMPR1A, and FSHR. MXC decreased the protein abundance of AMH, and all examined receptors in small antral follicles. GDF9 and BMP15 were immunolocalized in oocytes and granulosa cells of preantral follicles of control and treated ovaries. All analyzed receptors were detected in the oocytes and granulosa cells of preantral follicles, and in the granulosa and theca cells of small antral follicles. The exception, however, was FSHR, which was detected only in the granulosa cells of small antral follicles. In addition, MXC decreased the plasma AMH and FSH concentrations. In conclusion, the present study may indicate long-term effects of neonatal MXC exposure on GDF9, BMP15, AMH, and FSH signaling in ovaries of adult pigs. However, the MXC effects varied at different stages of follicular development. It seems that neonatal MXC exposure may result in accelerated initial recruitment of ovarian follicles and impaired cyclic recruitment of antral follicles.

Effects of neonatal exposure to methoxychlor on corpus luteum in gilts: A transcriptomic analysis.

This study investigated the effects of neonatal exposure to methoxychlor (MXC), a synthetic organochlorine used as an insecticide with estrogenic, antiestrogenic, and antiandrogenic activities, on luteal function in pigs. Piglets were injected subcutaneously with MXC (20 µg/kg body weight) or corn oil (control) between postnatal Days 1 and 10 (N = 5/group). Corpora lutea from sexually mature gilts were examined for luteal steroid and prostaglandin concentrations and processed for total RNA isolation and subsequent RNA sequencing. Intra-luteal concentrations of androstenedione and prostaglandin E2 were greater, while that of estrone was lower when compared to control. Fifty-three differentially expressed (DE) microRNAS (miRNAs) (p-adjusted <.05 and log2(fold change) ≥.5) and 359 DE genes (p-adjusted <.05 and log2(fold change) ≥1) were identified in luteal tissue in response to neonatal MXC treatment. MXC was found to affect the expression of genes related to lipogenesis, steroidogenesis, membrane transport, immune response, cell signaling and adhesion. These results suggest an earlier onset of structural luteolysis in pigs caused by MXC actions in neonates. Since negative correlation analysis showed the potential interactions of miRNAs with specific messenger RNAs, we propose that these miRNAs are potential mediators of the long-term MXC effect on the CL function in pigs.

Altrenogest affects the development and endocrine milieu of ovarian follicles in prepubertal and mature gilts†.

Altrenogest with gonadotropins is commonly used to synchronize the estrous cycle, but it can also lead to follicular cyst formation, especially in prepubertal gilts. Here, we aimed to investigate how maturity and altrenogest treatment affect the development, endocrine milieu, and molecular control of ovarian follicles. Crossbred prepubertal and mature gilts were challenged or not (control) with altrenogest, and ovaries were collected in the morning on the first day of behavioral estrus. In prepubertal gilts, altrenogest decreased the percentage of primordial and atretic small follicles, but increased large antral follicles when compared with controls. In mature gilts, altrenogest reduced the percentage of primary follicles and elevated the total number of antral follicles. Maturity affected the estradiol level in the follicular fluid of preovulatory follicles, luteinizing hormone (LH)-stimulated cyclic adenosine monophosphate (cAMP) generation, and LH receptor messenger RNA (mRNA) expression in granulosa. Moreover, cytochrome P45017A1 (CYP17A1) mRNA levels in the theca layer were affected and correlated with follicular androstendione and estradiol concentration. Altrenogest negatively affected follicular fluid progesterone concentration and decreased levels of prostaglandin (PG) E2 in prepubertal gilts and PGF2alpha metabolite in mature gilts. LH-stimulated cAMP release in granulosa cells of mature gilts as well as human chorionic gonadotropin- and forskolin-induced cAMP were also affected. In addition, altrenogest downregulated CYP17A1 mRNA in the prepubertal theca layer and PGF2alpha synthase expression in the granulosa and theca layer of mature gilts. To the best of our knowledge, this is the first study to report multiple effects of maturity and altrenogest on the endocrine milieu and molecular regulations governing ovarian follicle development in gilts.

Effects of neonatal methoxychlor exposure on the ovarian transcriptome in piglets.

Methoxychlor (MXC) is a man-made organochlorine insecticide capable of disrupting endocrine functions due to its mixed steroidal properties (estrogenic, anti-estrogenic and/or anti-androgenic). Retarded follicle development was recently reported in neonatal pigs treated with MXC. The goal of the current study was to better understand the mechanism of MXC action in the ovary of newborn piglets. By employing RNA-Seq we studied the expression of protein coding (mRNA) and long non-coding RNA (lncRNA) transcripts in the ovary of the MXC-treated piglets. Piglets were injected (sc) daily with MXC (100 mg/kg body weight) or corn oil (controls) between postnatal Days 1 and 10 (n = 3 piglets/group). The ovaries excised from 11-day-old piglets were processed for total RNA isolation and subsequent RNA sequencing. Four hundred sixty differentially expressed genes (DEGs) and 143 differentially expressed lncRNAs (DELs) were identified in the ovaries of MXC-treated piglets (P-adjusted < 0.05; abs(log2FC) > 1). Functional enrichment analysis showed that MXC altered the expression of genes associated with intracellular and membrane transport, intra-ovarian signaling as well as cell-cell junction and communication. Moreover, positive and negative correlations determined between the identified DEGs and DELs suggest that some lncRNAs may mediate the MXC action in the ovary. The results support the hypothesis that MXC-induced changes in the expression of genes involved in neonatal ovarian folliculogenesis increase the risk of fertility problems in adults.

Effect of neonatal exposure to endocrine-active compounds on epigenetic regulation of gene expression in corpus luteum of gilts.

Recently, we have demonstrated that neonatal exposure to environmental endocrine-active compounds (EACs) with androgenic/antiandrogenic and estrogenic/antiestrogenic activities led to morphological and functional changes in the porcine corpus luteum (CL). To gain insight into the regulatory mechanisms of the long-term effects of EACs, we analyzed the impact of neonatal exposure of such compounds on global DNA methylation and the expression of miRNA biogenesis components in the porcine CL. Piglets were injected subcutaneously with testosterone propionate (TP, an androgen), flutamide (FLU, an antiandrogen), 4-tert-octylphenol (OP, an estrogenic compound), ICI 182,780 (ICI, an antiestrogen), methoxychlor (MXC, a compound with mixed activities) or corn oil (control) between postnatal days 1 and 10 (n = 5/group). The CLs from sexually mature gilts were examined for global DNA methylation and for the abundance of proteins related to DNA methylation (DNMT1, DNMT3A and DNMT3B) and miRNA biogenesis (DROSHA, XPO5, DICER1, AGO2) using an enzyme-linked immunosorbent assay, Western blotting and immunohistochemical staining. ICI and MXC increased the global DNA methylation levels and DNMT1 protein abundance in the luteal tissue. OP treatment led to a lower DROSHA protein abundance, while ICI treatment resulted in a greater DROSHA protein abundance. Both FLU and ICI increased DICER1 protein abundance in the luteal tissue. In addition, XPO5 showed immunolocalization exclusively in small luteal cells in the OP-treated pigs, in contrast to localization in both small and large luteal cells in the controls. In conclusion, the changes in DNA methylation, as well as the altered miRNA biogenesis components, seem to be a part of the regulatory network that mediates the long-term effects of EACs on CL function in pigs.

Transcriptomic profiles of the ovaries from piglets neonatally exposed to 4-tert-octylphenol.

The environmental pollutants with hormonal activities may influence steroid-mediated processes in neonatal ovaries and increase the incidence of reproductive disorders. The aim of the current study was to examine effects of 4-tert-octylphenol (OP), a non-ionic surfactant widely used in a variety of industrial applications which has been reported to mimic the 17ß-estradiol activity, on the expression of protein-coding (mRNAs) and long non-coding (lncRNAs) transcripts in neonatal ovaries of the pig. By employing RNA-Seq we aimed to gain insights into regulatory networks underlying the OP effects on the follicular development in pigs. Piglets were injected (sc) daily with OP (100 mg/kg bw) or corn oil (controls) between postnatal Days 1 and 10 (n = 3/group). Ovaries were excised from the 11-day-old piglets and total cellular RNA was isolated and sequenced. Two hundred three differentially expressed genes (DEGs; P-adjusted < 0.05 and log2 fold change ≥1.0) and 23 differentially expressed lncRNAs (DELs; P-adjusted < 0.05 and log2 fold change ≥ 1.0) were identified in OP-treated piglet ovaries. The DEGs were assigned to Gene Ontology terms, covering biological processes, molecular functions and cellular components, which linked the DEGs to functions associated with movement of cell or subcellular component, regulation of plasma membrane bounded cell projection assembly as well as hydrolase and endopeptidase activity. In addition, STRING analysis demonstrated the strongest interactions between genes related to negative regulation of endopeptidase activity. Some correlations between DEGs and DELs were also found, revealing that the OP action on the ovary may be partially executed via the changes in the lncRNA expression. These results suggest that neonatal exposure of pigs to OP induces changes in the ovarian transcriptomic profile associated with genes encoding serine protease inhibitors and involved in steroid synthesis as well as genes linked to intracellular and membrane transport. We suggest that the changes in the mRNA and lncRNA expression in the ovaries of OP-treated piglets may disturb ovarian cellular function, including steroidogenesis, proliferation and apoptosis.

A transcriptome approach evaluating effects of neonatal androgen and anti-androgen treatments on regulation of luteal function in sexually mature pigs.

The current study was designed to gain insights into regulatory mechanisms mediating long-term effects of androgen excess or deficiency on corpus luteum function in pigs. Piglets were injected subcutaneously with testosterone propionate (TP, an androgen), flutamide (FLU, an anti-androgen) or corn oil (control) between postnatal Days 1 and 10. Corpora lutea from sexually mature gilts were examined for luteal steroid concentrations and processed for total RNA isolation and subsequent RNA sequencing to determine abundances of mRNA transcripts and microRNAs (miRNAs). Potential miRNA-mRNA interactions were explored in silico. Androstenedione, testosterone and estrone concentrations in corpora lutea were altered due to the disrupted androgen action in neonates. The luteal tissue had 465 and 353 genes for which there were differential mRNA abundances as compared with the control group (P-adjusted < 0.05; log2FC ≥ 1.0) in response to neonatal TP and FLU piglet treatments, respectively. Disruption of androgen signalling in neonates affected mRNA transcript abundance, as compared with the control group, for genes associated with apoptosis, angiogenesis and immune functions in the corpora lutea. Furthermore, there was a differential abundance of a group of miRNAs in the treatment groups compared with the control group. These results indicate the neonatal androgenic milieu affects the onset of luteolysis when these animals are sexually mature, although mechanisms for responses to TP or FLU likely differ. It is proposed that changes in specific miRNAs and mRNAs may, in part, account for long-term effects of androgen excess or androgen deficiency on corpus luteum function in pigs.

Neonatal exposure to agonists and antagonists of sex steroid receptors induces changes in the expression of oocyte-derived growth factors and their receptors in ovarian follicles in gilts.

The objective of the present study was to examine the effects of neonatal exposure to either agonists or antagonists of androgen and estrogen receptors on the expression of growth and differentiation factor 9 (GDF9) and bone morphogenetic protein 15 (BMP15) and their cognate receptors (TGFBR1, BMPR1B, and BMPR2) in ovarian follicles of adult pigs. Piglets were injected subcutaneously with testosterone propionate (TP, an androgen, at 20 mg/kg bw), flutamide (FLU, an antiandrogen, at 50 mg/kg bw), 4-tert-octylphenol (OP, an estrogenic compound, 100 mg/kg bw), ICI 182,780 (ICI, an antiestrogen, 400 µg/kg bw), or corn oil (control) between postnatal Days 1 and 10 (n = 5/group). Ovarian follicles were excised from adult pigs on Days 8-11 of the estrous cycle. The expression of GDF9, BMP15, TGFBR1, BMPR1B and BMPR2 were examined in the population of preantral and small antral ovarian follicles using real-time PCR, Western blot and immunohistochemistry. In preantral follicles, the upregulation of GDF9 mRNA and protein expression was found in pigs that were neonatally exposed to TP or FLU, while administration of TP or ICI resulted in upregulation of BMP15. TGFBR1 and BMPR2 mRNA and protein expression were upregulated in preantral follicles of adult pigs that were neonatally exposed to TP or FLU, while administration of TP or ICI resulted in upregulation of BMPR1B. In small antral follicles, the mRNA and protein for TGFBR1 and BMPR2 were upregulated, while BMPR1B was downregulated in response to neonatal OP treatment. In addition, treatment with FLU upregulated BMPR1B and BMPR2 mRNA and protein expression, while downregulated the expression of TGFBR1. Moreover, GDF9 and BMP15 were immunolocalized in oocytes and granulosa cells of preantral follicles obtained from both control and treated ovaries. TGFBR1, BMPR1B and BMPR2 receptors were observed in the oocytes and granulosa cells of preantral follicles as well as in granulosa and theca cells of small antral follicles. In conclusion, the present study demonstrated neonatal exposure to either agonists or antagonists of androgen and estrogen receptors affected GDF9 and BMP15 signalling in ovaries of adult pigs. It seems that neonatal androgen excess or deficiency may lead to the acceleration of initial follicle recruitment, while neonatal exposure to compounds with antiandrogenic and estrogenic activity may disturb small antral follicles fate. Therefore, it confirms that neonatal window is critical for programming of ovarian function in pigs.

Neonatal Exposure to Agonists and Antagonists of Sex Steroid Receptors Affects AMH and FSH Plasma Level and Their Receptors Expression in the Adult Pig Ovary.

In this study piglets were injected with testosterone propionate (TP, an androgen), flutamide (FLU, an antiandrogen), 4-tert-octylphenol (OP, an estrogenic compound), ICI 182,780 (ICI, an antiestrogen) or corn oil (controls) between postnatal days 1 and 10 (N = 5/group). Then plasma anti-Müllerian hormone (AMH) and follicle stimulating hormone (FSH) concentration and the expression of their receptors were examined in the adult pig ovary. TP and FLU decreased plasma AMH and FSH concentration. In preantral follicles, TP resulted in upregulation of AMHR2 and FSHR expression, but decreased AMH protein abundance. FLU upregulated AMHR2 expression, while OP increased FSHR mRNA. In small antral follicles, OP upregulated ACVR1 and BMPR1A expression, while FLU increased BMPR1A mRNA. FLU and ICI resulted in upregulation of AMHR2 expression. TP and FLU upregulated AMH expression, while it was downregulated in response to OP or ICI. Moreover, OP and ICI resulted in downregulation of FSHR expression, while FLU decreased FSHR protein abundance. In conclusion, neonatal exposure to either agonist or antagonist of androgen receptor affected AMH and FSH signalling systems in preantral follicles. In small antral follicles these systems were influenced by compounds with estrogenic, antiestrogenic, and antiandrogenic activity. Consequently, these hormonal agents may cause an accelerated recruitment of primordial follicles and affect the cycling recruitment of small antral follicles in pigs.

Flutamide-induced alterations in transcriptional profiling of neonatal porcine ovaries.

BACKGROUND: Androgens are involved in the regulation of ovarian development during fetal/neonatal life. Environmental chemicals displaying anti-androgenic activities may affect multiple signal transduction pathways by blocking endogenous androgen action. The aim of the current study was to examine effects of the anti-androgen flutamide on the expression of coding transcripts and long non-coding RNAs (lncRNAs) in neonatal porcine ovaries. By employing RNA-Seq technology we aimed to extend our understanding of the role of androgens in neonatal folliculogenesis and examine the impact of the anti-androgen flutamide on ovarian function. METHOD: Piglets were subcutaneously injected with flutamide (50 mg/kg BW) or corn oil (controls) between postnatal days 1 and 10 (n = 3/group). Ovaries were excised from the 11-day-old piglets and total cellular RNAs were isolated and sequenced. RESULTS: Flutamide-treated piglet ovaries showed 280 differentially expressed genes (DEGs; P-adjusted < 0.05 and log2 fold change ≥1.0) and 98 differentially expressed lncRNAs (DELs; P-adjusted < 0.05 and log2FC ≥ 1.0). The DEGs were assigned to GO term, covering biological processes, molecular functions and cellular components, which linked the DEGs to functions associated with cellular transport, cell divisions and cytoskeleton. In addition, STRING software demonstrated strongest interactions between genes related to cell proliferation. Correlations between DEGs and DELs were also found, revealing that a majority of the genes targeted by the flutamide-affected lncRNAs were associated with intracellular transport and cell division. CONCLUSIONS: Our results suggest that neonatal exposure of pigs to flutamide alters the expression of genes involved in ovarian cell proliferation, ovarian steroidogenesis and oocyte fertilization, which in turn may affect female reproduction in adult life.