Changes in mRNA expression of MMP-2 in the Müllerian duct of chicken embryo

Ethynylestradiol feminizes gene expression partly in testis developing as ovotestis and disrupts asymmetric Müllerian duct development by eliminating asymmetric gene expression in Japanese quail embryos

In avian embryos, xenoestrogens induce abnormalities in reproductive organs, particularly the testes and Müllerian ducts (MDs). However, the molecular mechanisms remain poorly understood. We investigated the effects of ethynylestradiol (EE2) exposure on gene expression associated with reproductive organ development in Japanese quail embryos. Reverse transcription quantitative polymerase chain reaction (RT-qPCR) analysis revealed that the left testis containing ovary-like tissues following EE2 exposure highly expressed the genes for steroidogenic enzymes (P450scc, P45017α, lyase, and 3β-HSD) and estrogen receptor-β, compared to the right testis. No asymmetry was found in these gene expression without EE2. EE2 induced hypertrophy in female MDs and suppressed atrophy in male MDs on both sides. RNA sequencing analysis of female MDs showed 1,366 differentially expressed genes between developing left MD and atrophied right MD in the absence of EE2, and these genes were enriched in Gene Ontology terms related to organogenesis, including cell proliferation, migration and differentiation, and angiogenesis. However, EE2 reduced asymmetrically expressed genes to 21. RT-qPCR analysis indicated that genes promoting cell cycle progression and oncogenesis were more highly expressed in the left MD than in the right MD, but EE2 eliminated such asymmetric gene expression by increasing levels on the right side. EE2-exposed males showed overexpression of these genes in both MDs. This study reveals part of the molecular basis of xenoestrogen-induced abnormalities in avian reproductive organs, where EE2 may partly feminize gene expression in the left testis, developing as the ovotestis, and induce bilateral MD malformation by canceling asymmetric gene expression underlying MD development.

Sexually dimorphic expression of sexual differentiation genes in the internal genital organs of Japanese quail embryos

Japanese quail (Coturnix japonica) is an avian model used to evaluate the reproductive and developmental toxicity of chemicals. The National Institute for Environmental Studies (NIES) of Japan established a strain of Japanese quail, NIES-L, which may be a better model because of its highly inbred characteristics. To understand sexual differentiation of the reproductive organs and the value of using NIES-L quails for avian toxicity assessment, we profiled estradiol and androgen plasma levels by enzyme-linked immunosorbent assay; the mRNA levels of estrogen receptor-α (ERα), ERβ, and androgen receptor (AR) in the gonads, Müllerian ducts, Wolffian ducts; and the mRNA levels of steroidogenic enzymes, cholesterol side chain cleavage enzyme (P450_scc), 17α-hydroxylase/C_17-20 lyase (P450_{17α, lyase}), 3β-hydroxysteroid dehydrogenase (3β-HSD), 17β-hydroxysteroid dehydrogenase (17β-HSD), and aromatase (P450_arom), anti-Müllerian hormone (AMH), and AMH receptor type 2 (AMHR2) in the gonads of NIES-L Japanese quails on embryonic days 9, 12, and 15 using a real-time quantitative PCR method. The plasma estradiol concentration was higher in females than males on these embryonic days, but no sex difference was found in the plasma androgens. The mRNA levels of all examined steroidogenic enzymes were significantly higher in female than male embryos. In particular, the P450_arom mRNA levels showed a striking sex difference: P450_arom was expressed in female but not male gonads. In contrast, the AMH and AMHR2 mRNA levels in the gonads were higher in males than females. The ERα, ERβ, and AR mRNA levels increased in the left female gonad and peaked on embryonic day 15, but not in the left and right male gonads; therefore, there was a female-biased sex difference. The ERα, ERβ, and AR mRNA levels in the left Müllerian duct, but not in the right Müllerian duct, of females increased and peaked on embryonic day 15, which resulted in asymmetric mRNA levels. The Wolffian ducts expressed ERα, ERβ, and AR in both sexes, and no sex difference or asymmetry of mRNA levels was found. The information obtained from this study helps elucidate the molecular endocrinological basis of sexual dimorphism formation of reproductive organs and clarify the value of NIES-L quails for toxicity assessment.

Matrix Metalloproteinases (MMPs) and Inhibitors of MMPs in the Avian Reproductive System: An Overview

Many matrix metalloproteinases (MMPs) are produced in the mammalian reproductive system and participate in the regulation of its functions. In birds, the limited information available thus far indicates that MMPs are significant regulators of avian ovarian and oviductal functions, too. Some MMPs and inhibitors of MMPs are present in the hen reproductive tissues and their abundances and/or activities change according to the physiological state. The intraovarian role of MMPs likely includes the remodeling of the extracellular matrix (ECM) during folliculogenesis, follicle atresia, and postovulatory regression. In the oviduct, MMPs are also involved in ECM turnover during oviduct development and regression. This study provides a review of the current knowledge on the presence, activity, and regulation of MMPs in the female reproductive system of birds.

Tamoxifen-induced alterations in the expression of selected matrix metalloproteinases (MMP-2, -9, -10, and -13) and their tissue inhibitors (TIMP-2 and -3) in the chicken ovary

Matrix metalloproteinases (MMPs) are a family of peptidases that disintegrate extracellular matrix (ECM) molecules associated with tissue remodeling, including reproductive tissues. Their actions are largely controlled by specific tissue inhibitors of MMPs (TIMPs). The role and regulation of MMPs in the chicken ovary is largely unknown. The aim of the present study was to examine the effect of tamoxifen (TMX; estrogen receptor modulator) treatment on the expression of selected members of the MMP system in the laying hen ovary. The activity of MMP-2 and -9 was also examined. Real-time polymerase chain reaction and western blot analyses revealed changes in mRNA and/or protein expression of MMP-2, -9, -10, -13, TIMP-2, and TIMP-3 in the following ovarian follicles after TMX treatment: white (WF), yellowish (YF), small yellow (SYF), and the largest yellow preovulatory (F3-F1). The response to TMX depended on the stage of follicle development and the layer of follicular wall. Moreover, ovarian regression following TMX treatment was accompanied by both an increase in total activity of MMP-2 in the theca layer of F3-F2 and granulosa layer of F2, and a decrease in total activity of MMP-2 in the WF, YF, and SYF, and MMP-9 in theca of F3-F1. In conclusion, the TMX-induced changes in MMP-2, -9, -10, and -13, and TIMP-2 and -3 mRNA expression, as well as MMP-2 and -9 activity, were dependent on tissue and the stage of follicular maturation. Our findings strongly suggests a role for estrogen in regulating the transcription, translation, and/or posttranslational activity of members of the MMP system. Further, these components may be involved in the orchestration of ECM turnover and cellular functions during ovary regression, which occur under conditions of reduced estrogenic activity.

Expression and localization of matrix metalloproteinases (MMP-2, -7, -9) and their tissue inhibitors (TIMP-2, -3) in the chicken oviduct during pause in laying induced by tamoxifen

Induced pause in egg laying simulates natural molting events in which the hen's reproductive organs regress and rejuvenate. Such processes require extracellular matrix remodeling that is maintained, at least in part, by the action of proteolytic enzymes known as matrix metalloproteinases (MMPs). Nevertheless, information concerning the expression and hormonal regulation of MMP system members in chickens is scarce. Therefore, MMP-2, -7, and -9 and their tissue inhibitors (TIMP-2, -3) expression and localization were investigated in all segments of the domestic hen oviduct (infundibulum, magnum, isthmus, shell gland, vagina) during a pause in egg laying induced by tamoxifen (TMX)-an estrogen receptor modulator. Hy-Line Brown hens were treated daily with TMX (n = 6) at a dose of 6 mg/kg of body weight or a vehicle (n = 6) until complete cessation of egg laying (for 7 days). Chickens were decapitated on Day 7 of the experiment. Real-time polymerase chain reaction and Western blotting revealed section-dependent expression of MMP-2, -7, -9 and TIMP-2 and -3. Immunohistochemistry found tissue and cell-dependent localization of examined proteins in the wall of the oviduct. The MMP-2, TIMP-2, and TIMP-3 were localized mainly in the luminal epithelium, MMP-7 in the luminal and glandular epithelium, whereas MMP-9 was detected only in the connective tissue. Treatment of chickens with TMX markedly elevated the relative expression of MMP-7 and MMP-9 mRNA in the oviduct, but did not affect MMP-2, TIMP-2, and TIMP-3 mRNA levels. However, TMX increased the MMP-2 protein level in the infundibulum, shell gland, and vagina as well as activity of MMP-2 evaluated by gelatin zymography. The results obtained indicate that MMP-2, MMP-7, and MMP-9 are involved in chicken oviduct regression. Moreover, changes in the expression and activity of chosen MMPs after TMX treatment may indicate a contribution of estrogen in the regulation of transcription, translation, and/or the activity of selected elements of the MMP system.

Involvement of matrix metalloproteinases (MMP-2, -7, -9) and their tissue inhibitors (TIMP-2, -3) in the chicken oviduct regression and recrudescence

This study was undertaken to examine mRNA and protein expression, localization of selected MMPs and their tissue inhibitors (TIMPs), and the activity of MMPs in all segments of the chicken oviduct (infundibulum, magnum, isthmus, shell gland, vagina) during a pause in egg laying induced by food deprivation. Control chickens (n = 18) were fed ad libitum, while experimental birds (n = 18) were fasted for 5 days, followed by being fed every other day, and then fed daily from day 10 onwards. Chickens were decapitated on day 6 (when the oviduct was regressed), day 13 (during oviduct recrudescence), and days 17-20 (oviduct rejuvenation) of the experiment. A pause in laying occurred between days 6 and 13 and resumption of laying before days 17-20. Real-time polymerase chain reaction and western blot revealed different expression of MMP-2, -7, -9 and TIMP-2 and -3 on mRNA and protein levels, respectively, as well as activity of MMP-2 and -9 by activity assay in the oviduct parts. Immunohistochemistry showed cell- and tissue-dependent localization of the examined members of the MMP system. Regression of the oviduct was accompanied predominantly by an increase in the relative expression of MMP-2, -7 and -9, and TIMP-2 and -3 mRNAs. The protein expression levels and localization of MMPs and TIMPs did not show pronounced changes during the examined period. During oviduct regression and recrudescence, elevated activity of MMP-2 and -9 was found. In summary, the results showing the stage of reproductive cycle-dependent changes as well as cell- and tissue-dependent differences in the expression of selected MMPs and TIMPs, and activity of MMP-2 and MMP-9 point to the significance that these molecules might be the local regulators of remodeling and functions of the hen oviduct.

Expression and localization of matrix metalloproteinases (MMP-2, -7, -9) and their tissue inhibitors (TIMP-2, -3) in the chicken oviduct during maturation

Although participation of matrix metalloproteinases (MMPs) in reproductive tract remodeling has been strongly suggested in mammalian species, the role of MMPs in the avian oviduct has received little attention. To gain a better understanding of the potential role of the MMP system in avian oviduct development, mRNA and protein expression, localization of selected MMPs and their tissue inhibitors (TIMPs), and gelatinolytic activity in the oviduct of growing chickens were examined. The oviducts were collected from Hy-Line Brown hens before (10, 12, 14 and 16 weeks of age) and after (week 17) the onset of egg laying. The MMP-2, -7, -9 and TIMP-2 and -3 genes were found to be differentially expressed in all examined oviductal sections: the infundibulum, magnum, isthmus and shell gland on both mRNA (by real time polymerase chain reaction) and protein (by western blotting and immunohistochemistry) levels. In the course of oviduct development, the relative expression of all genes decreased in most sections. Protein level of MMP-9 was diminished, while MMP-7 and TIMP-3 were elevated in the oviduct of growing birds. MMP-2 and TIMP-2 protein levels remained constant, with a slight increase in MMP-2 concentration just before reaching maturity. The relative activity of MMP-2 and -9 (assessed by gelatin zymography) was higher (P < 0.05, P < 0.01) in immature birds compared with adults. Immunohistochemistry demonstrated cell- and tissue-specific localization of MMPs and TIMPs in the wall of the chicken oviduct. We concluded that changes in the expression of examined MMPs and their inhibitors, as well as alterations in MMP activity occurring simultaneously with changes in the morphology of the chicken oviduct, suggest the involvement of the MMP system in the proper development and functioning of this organ. Mechanisms regulating the expression and activity of MMPs require further clarification.

In ovo administration of human recombinant leptin shows dose dependent angiogenic effect on chicken chorioallantoic membrane

Background

Leptin, the cytokine produced by white adipose tissue is known to regulate food energy homeostasis through its hypothalamic receptor. In vitro studies have demonstrated that leptin plays a major role in angiogenesis through binding to the receptor Ob-R present on ECs by stimulating and initiating new capillary like structures from ECs. Various in vivo studies indicate that leptin has diverse effect on angiogenesis. A few reports have showed that leptin exerts pro angiogenic effects while some suggested that it has antiangiogenic potential. It is theoretically highly important to understand the effect of leptin on angiogenesis to use as a therapeutic molecule in various angiogenesis related pathological conditions. Chicken chorio allantoic membrane (CAM) on 9th day of incubation was incubated with 1, 3 and 5 μg concentration of HRL for 72 h using gelatin sponge. Images where taken after every 24 h of incubation and analysed with Angioguant software. The treated area was observed under microscope and histological evaluation was performed for the same. Tissue thickness was calculated morphometrically from haematoxylin and eosin stained cross sections. Reverse transcriptase PCR and immunohistochemistry were also performed to study the gene and protein level expression of angiogenic molecules.

Results

HRL has the ability to induce new vessel formation at the treated area and growth of the newly formed vessels and cellular morphological changes occur in a dose dependent manner. Increase in the tissue thickness at the treated area is suggestive of initiation of new capillary like structures. Elevated mRNA and protein level expression of VEGF165 and MMP2 along with the activation of ECs as demonstrated by the presence of CD34 expression supports the neovascularization potential of HRL.

Conclusion

Angiogenic potential of HRL depends on the concentration and time of incubation and is involved in the activation of ECs along with the major interaction of VEGF 165 and MMP2. It is also observed that 3 μg of HRL exhibits maximum angiogenic potential at 72 h of incubation. Thus our data suggest that dose dependent angiogenic potential HRL could provide a novel role in angiogenic dependent therapeutics such as ischemia and wound healing conditions.

Expression and regulation of MMP1, MMP3, and MMP9 in the chicken ovary in response to gonadotropins, sex hormones, and TGFB1

Matrix metalloproteinases (MMPs) are a specific class of proteolytic enzymes that play critical roles in follicular development and luteinization in mammals. However, the role of MMPs in avian ovary remains largely unknown. We found that three MMP genes (MMP1, MMP3, and MMP9) were significantly up-regulated in 23-wk-old (laying phase) chicken ovaries compared with 6-wk-old ovaries (prepubertal phase). In reproductively active chicken ovary, MMP1 expression (both mRNA and protein) remained low in prehierarchical and preovulatory follicles but increased in postovulatory follicles (POFs). Both MMP3 and MMP9 expression levels increased during follicular maturation. MMP3 reached maximal expression in the first largest follicle (F1), while MMP9 levels continued to rise in POF1 and POF2 after ovulation. Immunohistochemistry, Western blot analysis, and zymography experiments indicated that MMP1, MMP3, and MMP9 were synthesized and secreted by granulosa cells of different follicles in the chicken ovary. The mRNA expression of MMP1 and MMP3 in the granulosa cells was stimulated by follicle-stimulating hormone, luteinizing hormone, progesterone, and estrogen but not by transforming growth factor beta 1 (TGFB1). However, the mRNA of MMP9 was induced by TGFB1 but not follicle-stimulating hormone, luteinizing hormone, progesterone, or estrogen. Luciferase reporter and mutagenesis analysis indicated the AP1 and NFkappaB elements located in the promoter region from -1700 to -2400 bp were critical for both basal and TGFB1-induced MMP9 transcription. These data provide the first spatial-temporal expression analysis of MMP system in the chicken ovary.

Activation of estrogen receptor alpha disrupts differentiation of the reproductive organs in chicken embryos

Gonadal estrogen plays an important role in the differentiation of a female phenotype in birds. Exogenous compounds that interfere with estrogen signaling, for instance by binding to the estrogen receptors alpha and beta (ERα and ERβ), are therefore potential disruptors of sexual differentiation in birds. The ERα agonist propyl-pyrazole-triol (PPT), the ERα antagonist methyl piperidino pyrazole (MPP) and the ERβ agonist diarylproprionitrile (DPN) were used in the present study to explore the roles of the ERs in normal and disrupted sex differentiation in the chicken embryo. Activation of ERα by PPT caused disturbed differentiation of the reproductive organs in both sexes. In male embryos, PPT caused left-side ovotestis formation and retention of the Müllerian ducts. In female embryos, PPT caused retention of the right Müllerian duct (which normally regresses) and malformation of both Müllerian ducts. PPT also induced hepatic expression of mRNA for the estrogen-regulated egg yolk protein apoVLDL II. Notably, none of these effects were observed following treatment with DPN. ERα-inactivation by MPP counteracted the action of PPT but had little effect by its own. Our results indicate that ERα plays an important role in sex differentiation of the reproductive tract in female chicken embryos and show that ERα can mediate xenoestrogen-induced disturbances of sex differentiation.

Effects on differentiation of reproductive organs and sexual behaviour in Japanese quail by excessive embryonic ERalpha activation

Exposure of Japanese quail (Coturnix japonica) embryos to oestrogenic substances disrupts sexual differentiation of the reproductive tract of both sexes and impairs the copulatory behaviour of the adult male. To examine whether these effects can be induced by selective activation of oestrogen receptor alpha (ERalpha), Japanese quail eggs were injected with various doses of the selective ERalpha agonist 16alpha-lactone-oestradiol (16alpha-LE(2)). The natural oestrogen 17beta-oestradiol (E(2)) was used as a positive control. Both 16alpha-LE(2) and E(2) induced formation of an ovary-like cortex in the left testis (ovotestis) and reduced the size of the right testis in male embryos. The asymmetry in testis size remained in sexually mature males. Both substances induced retention and malformation of the Müllerian ducts in embryos of both sexes and malformed oviducts in juveniles. Male copulatory behaviour was suppressed by embryonic exposure to E(2) and the highest dose of 16alpha-LE(2). However, the lower dose of 16alpha-LE(2), which markedly affected development of the reproductive organs, was without effects on behaviour. It can therefore not be excluded that the behavioural demasculinisation at the 100-fold higher dose involved cross-activation of oestrogen receptor beta (ERbeta). In conclusion, our results suggest that oestrogen-induced disruption of reproductive organ development in Japanese quail can be mediated via ERalpha, whereas the role of ERalpha in demasculinisation of copulatory behaviour remains to be clarified.

Effects of estrogens on sex differentiation in Japanese quail and chicken

Estrogen production by the female avian embryo induces development of a female phenotype of the reproductive organs whereas the low estrogen concentration in the male embryo results in a male phenotype. Treatment of female embryos with exogenous estrogens disrupts Müllerian duct development resulting in malformations and impaired oviductal function. Exposure of male embryos to estrogens results in ovotestis formation and persisting Müllerian ducts in the embryos and testicular malformations, reduced semen production and partially developed oviducts in the adult bird. Furthermore, studies in Japanese quail show that the male copulatory behavior is impaired by embryonic estrogen treatment. Results from our experiments with selective agonists for ERalpha and ERbeta suggest that the effects of estrogens on the reproductive organs are mediated via activation of ERalpha. Abundant expression of ERalpha mRNA was shown in gonads and Müllerian ducts of early Japanese quail embryos. Both ERalpha and ERbeta transcripts were detected by real-time PCR in early embryo brains of Japanese quail indicating that both receptors may be involved in sex differentiation of the brain. However, in 9-day-old quail embryo brains in situ hybridization showed expression of ERbeta mRNA, but not of ERalpha mRNA, in the medial preoptic nucleus (POM) and the bed nucleus of the stria terminalis (BSTm), areas implicated in copulatory behavior of adult male quail. Furthermore, embryonic treatment with the selective ERalpha agonist propyl pyrazol triol (PPT) had no effect on the male copulatory behavior. These results suggest that ERbeta may be important for the effects of estrogens on brain differentiation.

Selective estrogen receptor α activation disrupts sex organ differentiation and induces expression of vitellogenin II and very low-density apolipoprotein II in Japanese quail embryos

The Japanese quail (Coturnix japonica) is a widely used model species for studying the roles of steroid hormones in avian sex differentiation. The aim of the present study was to elucidate the significance of estrogen receptors α and β (ERα and ERβ) in normal sex differentiation of the reproductive organs in the Japanese quail and in xenoestrogen-induced disruption of reproductive organ differentiation. Real-time PCR indicated that ERα (ESR1) mRNA is expressed in both right and left gonads and Müllerian ducts (MDs) in both sexes during early morphological differentiation. ERβ (ESR2) transcripts were also detected in gonads and MDs, but at very low levels. Both receptor subtypes were expressed in the liver and may therefore mediate the expression of estrogen-regulated egg-yolk proteins. Aromatase mRNA was expressed at much higher levels in female than male gonads as early as embryonic day 5, indicating early sex differences in estrogen synthesis. Treatment with the ERα-selective agonist propyl pyrazole triol showed that frequently reported xenoestrogen effects, such as ovotestis formation, abnormal MD development, and hepatic expression of egg-yolk proteins, were induced by selective activation of ERα. Taken together, our results suggest that activation of ERα is crucial for estrogen-dependent sex differentiation of the reproductive organs and that ERα mediates xenoestrogen-induced toxicity during reproductive development in birds.

The Müllerian duct: recent insights into its development and regression

Several recent publications have contributed to our understanding of the processes involved in development of the Müllerian ducts in both sexes and regression of these structures in male embryos. Additionally, new insights in the regulation of the anti-Müllerian hormone (AMH) signaling pathway, the pathway, which mediates the male specific degeneration of Müllerian ducts, have been gained. It has become clear that the Müllerian duct is formed by invagination of the coelomic epithelium and elongates primarily by proliferation. Later on cells of the coelomic epithelium perform epithelial to mesenchymal transition and move around the epithelium of the Müllerian duct to induce degeneration of this structure in male embryos. Besides AMH and its specific type II receptor AMHR2 two different type I receptors as well as different SMAD family members have been shown to be involved in the AMH signaling cascade. Other factors including WT1, WNT7a, beta-catenin and MMP2 act upstream and downstream of AMH signaling. Here we try to draw an overall picture of Müllerian duct formation and regression by integrating the recent literature in the field.