Tissue-specific distribution of the androgen receptor (AR) in the porcine fetus

Testosterone Deficiency Caused by Castration Modulates Mitochondrial Biogenesis Through the AR/PGC1α/TFAM Pathway

Mammalian mitochondrial biogenesis is a complex process involving mitochondrial proliferation and differentiation. Mitochondrial DNA transcription factor A (TFAM), which encodes a major component of a protein-mitochondrial DNA (mtDNA) complex, is regulated by peroxisome proliferator-activated receptor γ coactivator 1α (PGC1α). Testosterone is the primary male sex hormone and plays an increasingly important role in mammalian development through its interaction with androgen receptor (AR). However, the function of AR in mitochondrial biogenesis induced by testosterone deficiency has not been investigated. Here, we explored the molecular mechanism underlying the effect of testosterone deficiency on mitochondrial biogenesis using a Yorkshire boar model. Testosterone deficiency caused by castration induced changes in mtDNA copy numbers in various tissues, and AR showed the opposite tendency to that of mtDNA copy number, particularly in adipose tissues and muscle tissues. In addition, castration weakened the correlation of PGC1α and mtDNA copy number, while AR and TFAM showed a relatively high correlation in both control and castrated pigs. Furthermore, luciferase assays revealed that AR binds to potential AR elements in the TFAM promoter to promote TFAM expression. Taken together, testosterone may be involved in the pathway linking PGC1α to mitochondrial biogenesis through the interaction between AR and TFAM.

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.

Maternal β-hydroxy-β-methylbutyrate (HMB) supplementation during pregnancy affects early folliculogenesis in the ovary of newborn piglets

Beta-hydroxy-beta-methylbutyrate (HMB) is a leucine metabolite with protein anabolic effects. This study was designed to determine whether prenatal HMB treatment has an effect on oogenesis and folliculogenesis in the ovary of newborn piglets. HMB decreased the number of egg nests and primordial follicles and increased the pool of developing follicles compared to the control group. Although the percentage of TUNEL-positive oocytes within the egg nests was higher in HMB-treated group no increase in the Bax/Bcl-2 ratio and active caspase-3 expression was observed. Moreover, the granulosa cell proliferation index and StAR protein expression were higher in HMB-treated group. In contrast to the control group, the expression of E-cadherins was reduced after the HMB treatment. In addition, a significant increase in the serum level of gonadotropins and steroid hormones was detected in HMB-treated piglets. In conclusion, prenatal HMB treatment dysregulates hormonal homeostasis which impairs early folliculogenesis in piglets.

"Positive Regulation of RNA Metabolic Process" Ontology Group Highly Regulated in Porcine Oocytes Matured In Vitro: A Microarray Approach

The cumulus-oocyte complexes (COCs) growth and development during folliculogenesis and oogenesis are accompanied by changes involving synthesis and accumulation of large amount of RNA and proteins. In this study, the transcriptomic profile of genes involved in “oocytes RNA synthesis” in relation to in vitro maturation in pigs was investigated for the first time. The RNA was isolated from oocytes before and after in vitro maturation (IVM). Interactions between differentially expressed genes/proteins belonging to “positive regulation of RNA metabolic process” ontology group were investigated by STRING10 software. Using microarray assays, we found expression of 12258 porcine transcripts. Genes with fold change higher than |2| and with corrected p value lower than 0.05 were considered as differentially expressed. The ontology group “positive regulation of RNA metabolic process” involved differential expression of AR, INHBA, WWTR1, FOS, MEF2C, VEGFA, IKZF2, IHH, RORA, MAP3K1, NFAT5, SMARCA1, EGR1, EGR2, MITF, SMAD4, APP, and NR5A1 transcripts. Since all of the presented genes were downregulated after IVM, we suggested that they might be significantly involved in regulation of RNA synthesis before reaching oocyte MII stage. Higher expression of “RNA metabolic process” related genes before IVM indicated that they might be recognized as important markers and specific “transcriptomic fingerprint” of RNA template accumulation and storage for further porcine embryos growth and development.

Role of androgens in normal and pathological ovarian function

Androgens mediate their actions via the androgen receptor (AR), a member of the nuclear receptor superfamily. AR-mediated androgen action is essential in male reproductive development and function; however, only in the last decade has the suspected but unproven role for AR-mediated actions in female reproduction been firmly established. Deciphering the specific roles and precise pathways by which AR-mediated actions regulate ovarian function has been hindered by confusion on how to interpret results from pharmacological studies using androgens that can be converted into oestrogens, which exert actions via the oestrogen receptors. The generation and analysis of global and cell-specific femaleArknockout mouse models have deduced a role for AR-mediated actions in regulating ovarian function, maintaining female fertility, and have begun to unravel the mechanisms by which AR-mediated androgen actions regulate follicle health, development and ovulation. Furthermore, observational findings from human studies and animal models provide substantial evidence to support a role for AR-mediated effects not only in normal ovarian function but also in the development of the frequent ovarian pathological disorder, polycystic ovarian syndrome (PCOS). This review focuses on combining the findings from observational studies in humans, pharmacological studies and animal models to reveal the roles of AR-mediated actions in normal and pathological ovarian function. Together these findings will enable us to begin understanding the important roles of AR actions in the regulation of female fertility and ovarian ageing, as well as providing insights into the role of AR actions in the androgen-associated reproductive disorder PCOS.

Antiandrogen flutamide affects folliculogenesis during fetal development in pigs

Androgen deficiency during prenatal development may affect the expression of genes involved in the folliculogenesis regulation. In order to study the effect of antiandrogen on fetal ovarian development, pregnant gilts were injected with flutamide (for 7 days, 50 mg/kg bodyweight per day) or corn oil (control groups) starting on gestation days 43 (GD50), 83 (GD90), or 101 (GD108). The obtained fetal ovaries were fixed for histology and immunohistochemistry or frozen for real-time PCR. Morphological evaluation, TUNEL assay, and expression of selected factors (Ki-67, GATA binding transcription factor 4 (GATA4), E-Cadherin and tumor necrosis factor a (TNFa)) were performed. On GD90 and GD108, ovaries following flutamide administration showed a higher number of egg nests and lower number off ollicles than those in respective control groups. An increased mRNA and protein expression of Ki-67 was observed in flutamide-treated groups compared with controls on GD50 and GD108 but decreased expression was found on GD90. In comparison to control groups a higher percentage of TUNEL-positive cells was shown after flutamide exposure on GD50 and GD90 and a lower percentage of apoptotic cells was observed on GD108. These data were consistent with changes in TNF (TNFa) mRNA expression, which increased on GD90 and decreased on GD108. E-cadherin mRNA and protein expression was upregulated on GD50 and downregulated on GD90 and GD108. In conclusion diminished androgen action in porcine fetal ovaries during mid- and late gestation leads to changes in the expression of genes crucial for follicle formation. Consequently, delayed folliculogenesis was observed on GD90 and GD108. It seems however that androgens exhibit diverse biological effects depending on the gestational period.

In utero exposure to the anti-androgen flutamide influences connexin 43 and β-catenin expression in porcine fetal gonads

Recent reports have indicated a role of cell-to-cell interactions during gonadal development and functions. Numerous reports indicate that fetal hormonal disruption induces abnormalities in the developing reproductive system and, therefore, may interfere with reproductive functions later in adult life. Hence, this study investigated the effect of androgen deficiency during late prenatal periods on the gap junction-associated connexin 43 (Cx43) and the adherens junction-associated β-catenin expression in the fetal porcine gonads. Thus, pregnant gilts were injected with anti-androgen flutamide (for 7 d, 50 mg/kg BW per day) or corn oil (control groups) starting at 83 (GD90) or 101 (GD108) gestational day. On GD90 and GD108 the fetuses were excised and fetal gonads were obtained. To assess Cx43 and β-catenin expression real-time PCR and immunohistochemistry were performed. In fetal testes, Cx43 was localized between Leydig cells, whereas β-catenin was observed mainly within the seminiferous tubules. In fetal ovaries, Cx43 was detected between interstitial cells and between granulosa cells of forming follicles, whereas β-catenin was found within egg nests, in oocytes' membrane, and in granulosa cells of forming follicles. Immunohistochemistry showed decreased Cx43 and β-catenin expression in fetal gonads from flutamide-treated pigs compared with respective controls. However, the ovaries from animals treated with flutamide on GD108 showed increased Cx43 expression. The changes of Cx43 and β-catenin expression after prenatal flutamide treatment were confirmed at the mRNA level. These findings suggest that androgen deficiency during late gestation may lead to disturbed intercellular interactions in fetal porcine testes affecting testicular functions, as well as impaired follicular formation in fetal ovaries. Our results further signify the role of androgens in the regulation of cell-to-cell interactions within fetal porcine gonads.

Influence of the antiandrogen flutamide on the androgen receptor gene expression in the placenta and umbilical cord during pregnancy in the pig

The aim of this study was to determine the immunolocalization and expression of the androgen receptor (AR) in the pig placenta and umbilical cord during pregnancy following exposure to flutamide, a non-steroidal antiandrogen, at its various stages. Pregnant pigs were injected with flutamide at a daily dose of 50mg/kg body weight at different stages of pregnancy: from day 83-89 (n=2); from day 101-107 (n=2). They were sacrificed and tissues collected one day after the last injection. Control animals, two for each experimental point, were injected only with the vehicle (corn oil). Collected tissue samples were fixed for immunohistochemistry or frozen for protein isolation. AR protein was detected in the nucleus of trophoblast cells forming the structure of ridges and in maternal endothelial cells, which are involved in the placental barrier formation. It was also localized in the nuclei of cells forming umbilical cord components: allantoic duct epithelium, amniotic epithelium, Wharton's jelly and the muscular layer of the umbilical cord vein and arteries. Relative optical density analysis showed increased expression in the material derived from animals treated with flutamide. The presence of AR in the placental barrier and in the umbilical cord components suggests a role of androgen in those temporary organs. Flutamide could impact on the levels of the AR protein in the reproductive tracts during pregnancy in sows.

The influence of the antiandrogen 2-hydroxyflutamide on the androgen receptor expression in the porcine ovarian follicles - an in vitro study

Androgens are one of the most important agents influencing ovarian follicles growth and development. The biological action of androgens is primarily exerted through transcriptional regulation by the androgen receptor (AR), a member of the steroid hormone receptor superfamily. The purpose of this study was to test the role of androgen receptor agonist testosterone (T) or antagonist 2-hydroxyflutamide (2-Hf) and in combination on AR expression in cultured porcine granulosa cells (GC) or whole follicles. Granulosa cells isolated from mature pig follicles were cultured for 48 h. During the last 12 and 24 h of culture, they were incubated in the presence of T (10(-7)  m/ml), 2-Hf (1.7 × 10(-4)  m) or both T and 2-Hf (T + 2-Hf, at the same concentrations as when added separately). To better imitate in vivo conditions, whole follicles (6-8 mm in diameter) isolated from porcine ovaries have been incubated (for 12 and 24 h) in an organ culture system with the addition of the same factors. Thereafter, cells or sections obtained from cultured follicles were processed for AR detection by immunocytochemistry or immunohistochemistry. Moreover, expression of AR mRNA and protein was determined by real-time PCR and Western blot analysis. It was shown that the addition of 2-Hf in the presence of T had a positive effect on AR mRNA and protein expression in porcine GC and ovarian follicles. Moreover, the addition of 2-Hf influenced AR distribution in GC cultures which is seen as change of its localization from nuclear to perinuclear. Our results suggest that androgens acting through AR could be involved in the control of AR expression in porcine GC in vitro and in vivo.

Prenatal and neonatal exposure to flutamide affects function of Leydig cells in adult boar

In this study, flutamide, an androgen receptor antagonist, was used as a tool to better understand the role of androgen receptor signaling and androgen signaling disruption during fetal and neonatal periods on porcine Leydig cell development and function. Flutamide, 50 mg kg(-1) d(-1) was administered into pregnant gilts during gestational days 20 to 28 and days 80 to 88 and into male piglets on postnatal days 2 to 10 (PD2). Leydig cells of flutamide-exposed boars, especially those of PD2 males, displayed morphologic alterations, increased size, and occupied increased area (P < 0.001) of the testes when compared with the control. Despite this, testosterone concentrations were reduced significantly in comparison with those of controls (P < 0.05, P < 0.001). Reduced testosterone production in response to flutamide exposure appeared to be related to changes in testosterone metabolism, as shown by increased aromatase mRNA (P < 0.05, P < 0.01), protein expression (P < 0.01, P < 0.001), and elevated estradiol concentrations (P < 0.001). Moreover, impaired Leydig cell responsiveness to LH was indicated by the decreased expression of LH receptor (P < 0.05, P < 0.001). No significant effect of flutamide was found on LH and FSH concentrations. Taken together, our data indicate that flutamide when administered during prenatal or neonatal period have a long-term effect on Leydig cell structure and function, leading to androgen-estrogen imbalance. Leydig cell failure was most evident in adult boars neonatally exposed to flutamide, suggesting that androgen action during neonatal development is of pivotal importance for the differentiation and function of porcine adult Leydig cell population.

Immunohistochemical studies on the proliferative marker Ki-67 and estrogen receptor alpha (ERα) in the uterus of neonatal and immature pigs following exposure to flutamide

The development of uterine glands is characterized by the proliferation of epithelial cells and by estrogen receptor alpha (ERα) expression in the nascent glandular epithelium. It is known that androgen receptors are present in the porcine uterus during prenatal development and the neonatal window, when adenogenesis occurs. Therefore, the objective of the study was to determine whether the effects of maternal or neonatal administration of the anti-androgen, flutamide, could entail changes in the presence of ERα and proliferation of uterine cells in neonatal and three-month-old pigs. Following prenatal flutamide exposure, morphological differences and the acceleration of uterus differentiation marked by ERα expression in epithelial crypts were observed in the neonatal piglets. In the three-month-old pig uterus, the proliferation of stromal cells was observed only after prenatal exposure to flutamide, whereas ERα staining was weaker. The neonatal administration of flutamide caused a significant decrease in the proliferation of the surface epithelium and diminished intensity of ERα staining in the stromal cells of the uterus of three-month-old pigs, which paralleled decreased estrogen levels in these animals. Overall, prenatal flutamide exposure promoted growth and development of the neonatal porcine uterus. Moreover, in three-month-old pigs, flutamide application during the neonatal period decreased surface epithelium proliferation and stromal ERα expression, which confirmed the importance of epithelial-stromal interactions in the adenogenesis.

Connexin 43 gene expression in male and female gonads of porcine offspring following in utero exposure to an anti-androgen, flutamide

The aim of this study was to show the effect of maternal exposure to flutamide on connexin 43 (Cx43) gene expression in testes and ovaries of 2-day-old piglets. Additionally, anogenital distance (AGD) was measured both in male and female offspring. Immunohistochemistry, Western blotting, and RT-PCR were performed to assess the immunoreactivity and the presence of Cx43 protein and it's mRNA, respectively. Following flutamide exposure strong immunostaining for Cx43 was observed between testicular Leydig cells, between granulosa cells of primary follicles, and between interstitial cells surrounding clusters of oocyte nests in the ovarian cortex as in the respective controls. Differences between the flutamide-treated groups and the controls obtained by qualitative immunohistochemistry were confirmed by quantitative image analysis (*P<0.05; **P<0.01). In Western blotting, Cx43 appeared as a band of 43kDa, whereas electrophoresis revealed PCR products of the predicted sizes. Screening for Cx43 expression revealed the presence of a transcript, both in control and in flutamide-treated pigs. The AGD values differed significantly from the control (*P<0.05). Overall, since no obvious changes in gonad morphology were observed and the Cx43 signal was present in all the examined tissues, it seems likely that androgens acting through ARs are not involved in the control of Cx43 gene expression in neonatal pig gonads.

Prenatal and neonatal exposure to the antiandrogen flutamide alters connexin 43 gene expression in adult porcine ovary

Connexin 43 (Cx43) is the predominant gap junction protein within porcine ovary and is required for proper follicle and corpus luteum (CL) development. Recent research suggests maternally or neonatally mediated effects of antiandrogens on reproductive function during adulthood, notably those dependent on gap junctional communication. The current study was conducted to determine whether late gestational or neonatal exposure to the antiandrogen flutamide influences Cx43 gene expression in the adult porcine ovary. Flutamide was injected into pregnant gilts between days 80 and 88 of gestation and into female piglets between days 2 and 10 posnatally. After animals reached sexual maturity, the ovaries were collected from treated and nontreated (control) pigs. Expression of Cx43 mRNA and protein was determined for preantral and antral follicles and for CLs. In addition, 3β-hydroxysteroid dehydrogenase (3β-HSD) expression and progesterone concentration were determined for luteal tissues. In preantral follicles, Cx43 mRNA was down-regulated (P < 0.01) following maternal and neonatal flutamide exposure. In large antral follicles, Cx43 mRNA was up-regulated (P < 0.01) after neonatal flutamide administration. Immunofluorescence showed that Cx43 expression decreased (P < 0.001) in preantral follicles and increased (P < 0.001) in large antral follicles following flutamide exposure. In luteal tissues, Cx43 and 3β-HSD expression and progesterone concentration decreased (P < 0.01) after postnatal flutamide treatment. Overall, these results suggest the involvement of androgens in the regulation of Cx43 expression in pig ovary. Moreover, alteration of Cx43 expression by the administration of flutamide during particular prenatal and neonatal time periods may affect porcine follicle development, as well as CL formation and function.

Testosterone induces activation of porcine primordial follicles in vitro

Purpose

The mechanism underlying primordial follicle activation is poorly understood. In this study, in-vitro culture and subsequent xenotransplantation were conducted to determine whether testosterone promotes the activation of porcine primordial follicles.

Methods

Prepubertal porcine ovarian cortical strips containing primordial follicles were cultured in the presence of testosterone for 7 days, and subsequently transplanted to immunodeficient mice for 2 months. After culture and transplantation, development of follicles was examined histologically. The presence of androgen receptors in oocytes was assessed by use of western blot and immunohistochemical analyses.

Results

Testosterone at 10^-6 m induced the primordial follicle transition to the intermediate (19 ± 4%) and primary (3 ± 1%) stages after 7-day culture, while 56 ± 5% of primordial follicles remained in the initial pool. Higher concentrations, above 10^-5 m, or lower concentrations, below 10^-6 m, did not induce follicle transition to the primary stage. After 7-day culture with 10^-6 m testosterone, ovarian cortical strips were transplanted to immunodeficient mice. Some of the follicles developed to the secondary (15 ± 3%) and antral (10 ± 3%) stages, whereas 44 ± 7% of primordial follicles remained in the initial pool. In the culture experiment, estradiol-17β (10^-7-10^-5 m) had no significant effect on follicle activation. The androgen receptor antagonist, cyproterone acetate, inhibited the stimulatory effect of testosterone on primordial follicle activation, suggesting an androgen receptor-mediated action of testosterone. Western blot and immunohistochemical analyses revealed that androgen receptors were present in the oocytes of primordial follicles.

Conclusions

These results suggest that testosterone at 10^-6 m promotes the activation of porcine primordial follicles in vitro through the androgen receptors in the oocytes.