Induction of ovarian primordial follicle assembly by connective tissue growth factor CTGF

Iron overload triggering ECM-mediated Hippo/YAP pathway in follicle development: a hypothetical model endowed with therapeutic implications

Disruption of iron homeostasis plays a negative role in follicle development. The dynamic changes in follicle growth are dependent on Hippo/YAP signaling and mechanical forces. However, little is known about the liaison between iron overload and the Hippo/YAP signalling pathway in term of folliculogenesis. Here, based on the available evidence, we established a hypothesized model linking excessive iron, extracellular matrix (ECM), transforming growth factor-β (TGF-β) and Hippo/Yes-associated protein (YAP) signal regarding follicle development. Hypothetically, the TGF-β signal and iron overload may play a synergistic role in ECM production via YAP. We speculate that the dynamic homeostasis of follicular iron interacts with YAP, increasing the risk of ovarian reserve loss and may enhance the sensitivity of follicles to accumulated iron. Hence, therapeutic interventions targeting iron metabolism disorders, and Hippo/YAP signal may alter the consequences of the impaired developmental process based on our hypothesis, which provides potential targets and inspiration for further drug discovery and development applied to clinical treatment.

Fetal exposure of Aristolochic Acid I undermines ovarian reserve by disturbing primordial folliculogenesis

The primordial follicle pool established in early life determines the ovarian reserve in the female reproductive lifespan. Premature exhaustion of primordial follicles contributes to primary ovarian insufficiency (POI), that is dependent by the initial size of the primordial follicle pool and by the rate of its activation and depletion. AAI, a powerful nephrotoxin with carcinogenic potential, is present in the Aristolochiaceae species, which can release AAI into soil as a persistent pollutant. In order to assess the potential risk of Aristolochic Acid I (AAI) exposure on mammalian oogenesis, we uncovered its adverse effect on primordial folliculogenesis in the neonatal mouse ovary and its effect on female fertility in adulthood. Pregnant mice were orally administrated with doses of AAI without hepatic or renal toxicity during late-gestation. Ovaries from offspring of administered female displayed gross aberrations during primordial folliculogenesis. Also, unenclosed oocytes in germ-cell cysts showed increased DNA damage. Furthermore, several key factors, including NANOS3, SOX9, KLF4, that govern early gonad's differentiation were abnormally expressed in the exposed ovary, while the follicle formation was partially restored by knockdown of Nanos3 or sox9. In adulthood, these aberrations evolved into a significant reduction in offspring number and impaired ovarian reserve. Together, our results show that AAI influences primordial folliculogenesis and, importantly, affected female fertility. This study shows that administration of drugs herbs or consumption of vegetables that contain AAs during pregnancy may adversely influence the fertility of offspring.

Effects of bone morphogenetic protein 4, gremlin, and connective tissue growth factor on estradiol and progesterone production by bovine granulosa cells

Bone morphogenetic proteins (BMPs) are members of the transforming growth factor-β family of proteins that have been implicated in the paracrine regulation of granulosa cell (GC) function, but whether responses to BMPs change with follicular size or interact with connective tissue growth factor (CTGF) or BMP antagonists (e.g., gremlin [GREM]) to directly affect GC function of cattle is unknown. Therefore, to determine the effects of BMP4 on proliferation and steroidogenesis of GCs and its interaction with GREM or CTGF, experiments were conducted using bovine GC cultures. In vitro, BMP4 (30 ng/mL) inhibited (P < 0.05) follicle-stimulating hormone (FSH) plus insulin-like growth factor 1 (IGF1)-induced progesterone and estradiol production by large- and small-follicle GCs, but the inhibitory effect of BMP4 on estradiol production was much more pronounced in large-follicle GCs. In small-follicle GCs, BMP4 had no effect (P > 0.10) on IGF1-induced proliferation, but GREM inhibited (P < 0.05) cell proliferation and estradiol and progesterone production in IGF1 plus FSH-treated GCs. In large-follicle GCs, BMP4 (10 to 30 ng/mL) increased (P < 0.05) GC numbers and GREM (100 ng/mL) blocked this effect. In large-follicle GCs, CTGF inhibited (P < 0.05) FSH plus IGF1-induced progesterone and estradiol production, and CTGF blocked the stimulatory effect of BMP4 on GC proliferation. These results indicate that BMP4, GREM, and CTGF inhibit GC aromatase activity and progesterone production. Also, the stimulatory effect of BMP4 on GC proliferation and the inhibitory effects of BMP4 on GC steroidogenesis are more pronounced in large vs. small follicles.

Ovarian Rejuvenation Using Autologous Platelet-Rich Plasma

Advanced maternal age is associated with the natural oocyte depletion, leading to low oocyte yield, high infertility treatment cancellation rates, and eventual decreases in pregnancy rates. Various innovative interventions have been introduced to improve the outcome of infertility treatment for aging patients. Numerous published data demonstrated that early follicle development was regulated by intraovarian growth factors through autocrine or paracrine mechanisms. Platelet-rich plasma (PRP), a plasma fraction of peripheral blood with a high concentration of platelets, has been implemented in regenerative medicine in the last decade. The plasma contains a variety of growth factors that were suggested to be able to enhance angiogenesis regeneration and the cell proliferation process. The initial report showed that an intraovarian injection of PRP improved the hormonal profile and increased the number of retrieved oocytes in patients with diminished ovarian reserve. Subsequently, several studies with larger sample sizes have reported that this approach resulted in several healthy live births with no apparent complications. However, the use of ovarian PRP treatment needs to be fully investigated, because no randomized controlled trial has yet been performed to confirm its efficacy.

Brain-derived neurotrophic factor (BDNF) expression and function in the mammalian reproductive Tract

BACKGROUND

Neurotrophins of the nerve growth factor family are soluble polypeptides that are best known for their role in nerve growth, survival and differentiation in the central nervous system. A growing body of literature shows that neurotrophins and their receptors are also expressed throughout the reproductive tract.

OBJECTIVE AND RATIONALE

Neurotrophins are key regulatory proteins in reproductive physiology during development and throughout adult life. Of the neurotrophins, the literature describing the expression and function of brain-derived neurotrophic factor (BDNF) and its high-affinity receptor, neurotrophin receptor kinase-2 (NTRK2), has been expanding rapidly. We therefore conducted a systematic inductive qualitative review of the literature to better define the role of the BDNF in the reproductive tract. We postulate that BDNF and NTRK2 are central regulatory proteins throughout the reproductive system.

SEARCH METHODS

An electronic search of Medline (PubMed) and Web of Science for articles relating to BDNF and the reproductive system was carried out between January 2018 and February 2019.

OUTCOMES

In the ovary, BDNF expression and levels have been linked with follicle organisation during ovarian development, follicle recruitment and growth and oocyte maturation. In the endometrium, BDNF is involved in cell proliferation and neurogenesis. In contrast, literature describing the role of BDNF in other reproductive tissues is sparse and BDNF-NTRK2 signalling in the male reproductive tract has been largely overlooked. Whilst estradiol appears to be the primary regulator of BDNF expression, we also identified reports describing binding sites for glucocorticoid and myocyte enhancer factor-2, a calcium-response element through activation of an N-methyl-D-aspartate (NMDA) receptor, and aryl hydrocarbon receptor nuclear transporter protein-4 (ARNT) response elements in promoter regions of the BDNF gene. Expression is also regulated by multiple microRNAs and post-translational processing of precursor proteins and intracellular shuttling. BDNF-NTRK2 signalling is modulated through tissue specific receptor expression of either the full-length or truncated NTRK2 receptor; however, the functional importance remains to be elucidated. Dysregulation of BDNF expression and circulating concentrations have been implicated in several reproductive disorders including premature ovarian failure, endometriosis, pre-eclampsia, intra-uterine growth restriction (IUGR) and several reproductive cancers.

WIDER IMPLICATIONS

We conclude that BDNF and its receptors are key regulatory proteins central to gonadal development, ovarian regulation and uterine physiology, as well as embryo and placenta development. Furthermore, dysregulation of BDNF-NTRK2 in reproductive diseases suggests their potential role as candidate clinical markers of disease and potential therapeutic targets.

TGF-β1 sustains germ cell cyst reservoir via restraining follicle formation in the chicken

The transforming growth factor β (TGF-β) superfamily members are important molecules that regulate many ovarian functions under normal physiological and pathological conditions. TGF-β1 and its receptors are highly expressed in the ovarian cells of many species. However, the effect of TGF-β1 on the capacity of the avian germ cell reservoir remains unknown. In this study, 5-day-old chicks were injected with TGF-β1 (2.5, 12.5, and 62.5 μg/kg body weight) for 3 days to assess the effect of TGF-β1 on early follicle development. Morphological analysis showed that treatment with TGF-β1 (12.5 μg/kg) increased the number of germ cell cysts and reduced the number of primordial and growing follicles. The diameter and area of oocytes and follicles were decreased after TGF-β1 treatment. Immunohistochemical staining of the proliferating cell nuclear antigen revealed that the ratios of the positive somatic and granulosa cells were decreased by 16.2% and 2.48%, respectively. Furthermore, more apoptotic cells were observed in the TGF-β1 group than those of the control by terminal deoxynucleotidyl transferase dUTP nick end labeling assay. In addition, we cultured the 5d chicken ovaries for 3 days in vitro and found that treatment with TGF-β1 (10 ng/mL) manifested similar results as the in vivo experiment. However, the negative effect of TGF-β1 on early ovary development was rescued by treatment with a TGF-βR1 inhibitor SD208, resulting in increased expression of steroidogenic enzymes and cell cycle-regulating proteins. In conclusion, TGF-β1 could maintain the germ cell reservoir by restraining follicle activation involving reduced cell proliferation and steroidogenic enzymes gene expression at the early stage of ovarian development.

Effect of tamoxifen on the Notch signaling pathway in ovarian follicles of mice

We investigated the effect of tamoxifen (TAM) treatment on the Notch signaling pathway in mouse ovary. Mice were randomly divided into four groups. Control group A animals were untreated. Control group B animals were treated with the vehicle only. Animals of the 0.5 TAM group received 0.5 mg/day TAM. Animals of the 1.5 TAM group received 1.5 mg/day of TAM. TAM was injected subcutaneously for 5 days. Body weights were measured at the start and end of the experiment. Sections were stained using Crossman's modified trichrome to examine general ovarian structure. Other sections were immunostained to demonstrate Jagged 1, Ki 67 and Notch 2. The TUNEL method was used to detect apoptosis. No significant differences in body weight or ovarian weight were found among the experimental groups. The number of primordial follicles was greater in the treatment groups than in the control groups, while the number of antral follicles and corpora lutea were reduced in the treatment groups. Cell proliferation rates were decreased by TAM treatment and cystic follicles were formed in the ovarian stroma. Notch 2 expression in the granulosa cells was increased following TAM administration, but no change was found in Jagged 1 expression. TAM administration suppressed follicular development and exhibited a negative effect on ovarian morphology. Our findings suggest that the Notch pathway participates in the action of TAM. We suggest that it may be useful to use Notch pathway regulators to adjust the effects of TAM on the ovary.

SMAD3 directly regulates cell cycle genes to maintain arrest in granulosa cells of mouse primordial follicles

Primordial follicles, consisting of granulosa cell (GC)-enveloped oocytes are maintained in a state of developmental arrest until activated to grow. The mechanism that operates to maintain this arrested state in GCs is currently unknown. Here, we show the TGFβ-activated transcription factor SMAD3 is expressed in primordial GC nuclei alongside the cell cycle proteins, cyclin D2 (CCND2) and P27. Using neonatal C57/Bl6 mouse ovaries densely populated with primordial follicles, CCND2 protein co-localised and was detected in complex with P27 by immunofluorescence and co-immunoprecipitation, respectively. In the same tissue, SMAD3 co-precipitated with DNA sequences upstream of Ccnd2 and Myc transcription start sites implicating both as direct SMAD3 targets. In older ovaries follicle growth was associated with nuclear exclusion of SMAD3 and reduced P27 and CCND2 in GCs, alongside elevated Myc expression. Brief (2 H) exposure of neonatal ovaries to TGFβ1 (10 ng/ml) in vitro led to immediate dissociation of SMAD3 from the Ccnd2 and Myc promoters. This coincided with elevated Myc and phospho-S6, an indicator of mTOR signalling, followed by a small increase in mean primordial GC number after 48 H. These findings highlight a concentration-dependent role for TGFβ signalling in the maintenance and activation of primordial follicles, through SMAD-dependent and independent signalling pathways, respectively.

Effect of High-Fat Diet on Immature Female Mice and Messenger and Noncoding RNA Expression Profiling in Ovary and White Adipose Tissue

Obesity is a chronic multifactorial disease prevalent in many areas of the world and is a major cause of morbidity and mortality. In women, obesity increases the risks of both metabolic and reproductive diseases, such as diabetes and infertility. The mechanisms underlying these effects, especially in young women, are largely unknown. To explore these mechanisms, we established a high-fat diet (HFD) model of obesity in immature female mice. Microarray analysis of gene expression in ovaries and white adipose tissue identified a large number of differentially expressed genes (>1.3-fold change) in both tissues. In ovaries of the HFD group, there were 208 differentially expressed messenger RNAs (mRNAs), including 98 upregulated and 110 downregulated, and 295 differentially expressed lncRNAs (long non coding RNAs), including 63 upregulated and 232 downregulated. In white adipose tissue, there were 625 differentially expressed mRNAs, including 220 upregulated and 605 downregulated in the HFD group, and 1595 differentially expressed lncRNAs, including 1320 and 275 downregulated in the HFD group. Our results reveal significant differences between the transcriptomes of the HFD and control groups in both ovaries and white adipose tissue that provide clues to the molecular mechanisms of diet-induced female reproductive dysfunction and metabolic disorders, as well as biomarkers of risk for these disorders.

Vasorin: a newly identified regulator of ovarian folliculogenesis

Members of the TGF-β superfamily take part in the control of folliculogenesis. Vasorin (Vasn) is a newly identified negative regulator of TGF-β signaling whose possible involvement in ovarian physiology has never been studied. Here, we demonstrate that Vasn is expressed in the ovary by somatic cells of follicles, and that its expression is up-regulated by LH. We established a conditional knockout (cKO) mouse model in which Vasn is deleted specifically in granulosa cells of growing follicles from the secondary stage onwards. Using this model, we show that, upon hormonal stimulation, follicle ovulation size is almost 2-fold higher. This enhanced ovulatory response is associated with overactivation of the TGF-β signaling pathway and a lower number of atretic antral follicles. Of importance, we demonstrate that the number of primordial follicles is reduced in prepubertal cKO mouse ovaries, which suggests that the production of VASN by growing follicles protects the ovarian reserve. Finally, analysis of systemic KO mice revealed that the ovarian reserve is almost 2.5-fold higher, which implies that Vasn may also play a role in primordial follicle formation. Overall, our findings reveal that Vasn is a new regulator that exerts an effect on several key ovarian functions, including folliculogenesis, maintenance of the ovarian reserve, and ovulation.-Rimon-Dahari, N., Heinemann-Yerushalmi, L., Hadas, R., Kalich-Philosoph, L., Ketter, D., Nevo, N., Galiani, D., Dekel, N. Vasorin: a newly identified regulator of ovarian folliculogenesis.

Effects of methoxychlor on IGF-I signaling pathway in rat ovary

Follicular development and other ovarian functions are regulated by growth factors that can be affected by exogenous agents. Methoxychlor (MXC) is an organochloride pesticide that causes female infertility. We investigated how MXC affects the distribution of developing ovarian follicles in adult rats after treatment between embryonic day (E) 18 and postnatal day (PND) 7. We also measured insulin-like growth factor-I (IGF-I) and its receptor, IGF-IR, expressions in ovarian follicles and investigated whether MXC changed the levels of IGF-I and IGF-IR in the ovary. Using immunohistochemical (IHC) staining, we detected IGF-I expression in oocytes and granulosa cells of the follicles, luteal cells, interstitial cells, theca externa and theca interna, and the smooth muscle of ovarian vessels. IGF-IR was co-localized with IGF-I in the ovary except for the theca externa. IGF-I expression was decreased in granulosa cells of preantral and antral follicles after treatment with MXC compared to granulosa cells of preantral and antral follicles of the control group. We also observed that oocytes of secondary follicles and granulosa cells of secondary and preantral follicles of the MXC treated groups showed increased IGF-IR expression compared to oocytes of secondary follicles and granulosa cells of secondary and preantral follicles of the control group. We also detected more secondary and preantral follicles, and fewer primordial and antral follicles after MXC administration compared to controls. Therefore, the IGF signaling pathway may participate in MXC induced ovary dysfunction and female infertility.

Ovarian Folliculogenesis

The ovary, the female gonad, serves as the source for the germ cells as well as the major supplier of steroid sex hormones. During embryonic development, the primordial germ cells (PGCs) are specified, migrate to the site of the future gonad, and proliferate, forming structures of germ cells nests, which will eventually break down to generate the primordial follicles (PMFs). Each PMF contains an oocyte arrested at the first prophase of meiosis, surrounded by a flattened layer of somatic pre-granulosa cells. Most of the PMFs are kept dormant and only a selected population is activated to join the growing pool of follicles in a process regulated by both intra- and extra-oocyte factors. The PMFs will further develop into secondary pre-antral follicles, a stage which depends on bidirectional communication between the oocyte and the surrounding somatic cells. Many of the signaling molecules involved in this dialog belong to the transforming growth factor β (TGF-β) superfamily. As the follicle continues to develop, a cavity called antrum is formed. The resulting antral follicles relay on the pituitary gonadotropins, follicle-stimulating hormone (FSH), and luteinizing hormone (LH) for their development. Most of the follicles undergo atretic degeneration and only a subset of the antral follicles, known as the dominant follicles, will reach the preovulatory stage at each reproductive cycle, respond to LH, and subsequently ovulate, releasing a fertilizable oocyte. The remaining somatic cells in the raptured follicle will undergo terminal differentiation and form the corpus luteum, which secretes progesterone necessary to maintain pregnancy.

Activin A-induced increase in LOX activity in human granulosa–lutein cells is mediated by CTGF

Lysyl oxidase (LOX) is the key enzyme involved in the crosslinking of collagen and elastin that is essential for the formation of extracellular matrix (ECM). LOX-mediated ECM remodeling plays a critical role in follicle development, oocyte maturation and corpus luteum formation. To date, the regulation of LOX in human ovary has never been elucidated. Activin A and its functional receptors are highly expressed in ovarian follicles from an early developmental stage. They locally regulate follicle progression. The aim of this study was to investigate the effects of activin A on the expression of LOX and its extracellular enzyme activity in primary and immortalized human granulosa–lutein cells obtained from patients undergoing anin vitrofertilization procedure. We demonstrated that activin A significantly upregulated the expression of connective tissue growth factor (CTGF) and LOX via an activin/TGF-β type I receptor mediated-signaling pathway. Using a target depletion small interfering RNA knockdown approach, we further confirmed that the upregulation of CTGF expression resulted in an activin-A-induced increases in LOX expression and activity. These findings may provide insight into the mechanisms by which intrafollicular growth factors regulate the expression of LOX for ECM formation and tissue remodeling in the human ovary.

Etoposide damages female germ cells in the developing ovary

BACKGROUND

As with many anti-cancer drugs, the topoisomerase II inhibitor etoposide is considered safe for administration to women in the second and third trimesters of pregnancy, but assessment of effects on the developing fetus have been limited. The purpose of this research was to examine the effect of etoposide on germ cells in the developing ovary. Mouse ovary tissue culture was used as the experimental model, thus allowing us to examine effects of etoposide on all stages of germ cell development in the same way, in vitro.

RESULTS

Fetal ovaries from embryonic day 13.5 CD1 mice or neonatal ovaries from postnatal day 0 CD1 mice were cultured with 50-150 ng ml(-1) or 50-200 ng ml(-1) etoposide respectively, concentrations that are low relative to that in patient serum. When fetal ovaries were treated prior to follicle formation, etoposide resulted in dose-dependent damage, with 150 ng ml(-1) inducing a near-complete absence of healthy follicles. In contrast, treatment of neonatal ovaries, after follicle formation, had no effect on follicle numbers and only a minor effect on follicle health, even at 200 ng ml(-1). The sensitivity of female germ cells to etoposide coincided with topoisomerase IIα expression: in the developing ovary of both mouse and human, topoisomerase IIα was expressed in germ cells only prior to follicle formation.

CONCLUSIONS

Exposure of pre-follicular ovaries, in which topoisomerase IIα expression was germ cell-specific, resulted in a near-complete elimination of germ cells prior to follicle formation, with the remaining germ cells going on to form unhealthy follicles by the end of culture. In contrast, exposure to follicle-enclosed oocytes, which no longer expressed topoisomerase IIα in the germ cells, had no effect on total follicle numbers or health, the only effect seen specific to transitional follicles. Results indicate the potential for adverse effects on fetal ovarian development if etoposide is administered to pregnant women when germ cells are not yet enclosed within ovarian follicles, a process that starts at approximately 17 weeks gestation and is only complete towards the end of pregnancy.

Novel action of FOXL2 as mediator of Col1a2 gene autoregulation

FOXL2 belongs to the evolutionarily conserved forkhead box (FOX) superfamily and is a master transcription factor in a spectrum of developmental pathways, including ovarian and eyelid development and bone, cartilage and uterine maturation. To analyse its action, we searched for proteins that interact with FOXL2. We found that FOXL2 interacts with specific C-terminal propeptides of several fibrillary collagens. Because these propeptides can participate in feedback regulation of collagen biosynthesis, we inferred that FOXL2 could thereby affect the transcription of the cognate collagen genes. Focusing on COL1A2, we found that FOXL2 indeed affects collagen synthesis, by binding to a DNA response element located about 65Kb upstream of this gene. According to our hypothesis we found that in Foxl2(-/-) mouse ovaries, Col1a2 was elevated from birth to adulthood. The extracellular matrix (ECM) compartmentalizes the ovary during folliculogenesis, (with type I, type III and type IV collagens as primary components), and ECM composition changes during the reproductive lifespan. In Foxl2(-/-) mouse ovaries, in addition to up-regulation of Col1a2, Col3a1, Col4a1 and fibronectin were also upregulated, while laminin expression was reduced. Thus, by regulating levels of extracellular matrix components, FOXL2 may contribute to both ovarian histogenesis and the fibrosis attendant on depletion of the follicle reserve during reproductive aging and menopause.

Control of Oocyte Growth and Development by Intercellular Communication Within the Follicular Niche

In the mammalian ovary, each oocyte grows and develops within its own structural and developmental niche-the follicle. Together with the female germ cell in the follicle are somatic granulosa cells, specialized companion cells that surround the oocyte and provide support to it, and an outer layer of thecal cells that serve crucial roles including steroid synthesis. These follicular compartments function as a single physiological unit whose purpose is to produce a healthy egg, which upon ovulation can be fertilized and give rise to a healthy embryo, thus enabling the female germ cell to fulfill its reproductive potential. Beginning from the initial stage of follicle formation and until terminal differentiation at ovulation, oocyte and follicle growth depend absolutely on cooperation between the different cellular compartments. This cooperation synchronizes the initiation of oocyte growth with follicle activation. During growth, it enables metabolic support for the follicle-enclosed oocyte and allows the follicle to fulfill its steroidogenic potential. Near the end of the growth period, intra-follicular interactions prevent the precocious meiotic resumption of the oocyte and ensure its nuclear differentiation. Finally, cooperation enables the events of ovulation, including meiotic maturation of the oocyte and expansion of the cumulus granulosa cells. In this chapter, we discuss the cellular interactions that enable the growing follicle to produce a healthy oocyte, focusing on the communication between the germ cell and the surrounding granulosa cells.

Lats1 Deletion Causes Increased Germ Cell Apoptosis and Follicular Cysts in Mouse Ovaries

The Hippo signaling pathway is essential for regulating proliferation and apoptosis in mammalian cells. The LATS1 kinase is a core member of the Hippo signaling pathway that phosphorylates and inactivates the transcriptional co-activators YAP1 and WWTR1. Deletion of Lats1 results in low neonate survival and ovarian stromal tumors in surviving adults, but the effects of Lats1 on early follicular development are not understood. Here, the expression of Hippo pathway components including Wwtr1, Stk4, Stk3, Lats2, and Yap1 transcripts were decreased by 50% in mouse ovaries between 2 and 8 days of age while expression was maintained from 8 days to 21 days and after priming with eCG. LATS1, LATS2, and MOB1B were localized to both germ and somatic cells of primordial to antral follicles. Interestingly, YAP1 was predominantly cytoplasmic, whereas WWTR1 was nuclear in oocytes and somatic cells. Deletion of Lats1 caused an increase in germ cell apoptosis from 1.7% in control ovaries to 3.6% in Lats1 mutant ovaries and a 58% and 32% decrease in primordial and activated follicle numbers in cultured mutant ovaries. Surprisingly, there was an increase in Bmp15 but not Gdf9, Figla, Nobox transcripts or the somatic-specific transcripts Amh and Wnt4 in cultured Lats1 mutant ovaries. Last, Lats1 mutant ovaries developed ovarian cysts at a higher frequency (43%) than heterozygous (24%) and control ovaries (8%). Results showed that the Hippo pathway is active in ovarian follicles and that LATS1 is required to maintain the pool of germ cells and primordial follicles.

Factors in Early-Life Programming of Reproductive Fitness

Fertility rates have been declining worldwide, with a growing number of young women suffering from infertility. Infectious and inflammatory diseases are important causes of infertility, and recent evidence points to the critical role of the early-life microbial environment in developmental programming of adult reproductive fitness. Our laboratory and others have demonstrated that acute exposure to an immunological challenge early in life has a profound and prolonged impact on male and female reproductive development. This review presents evidence that perinatal exposure to immunological challenge by a bacterial endotoxin, lipopolysaccharide, acts at all levels of the hypothalamic-pituitary-gonadal axis, resulting in long-lasting changes in reproductive function, suggesting that disposition to infertility may begin early in life.

Cyclic AMP in oocytes controls meiotic prophase I and primordial folliculogenesis in the perinatal mouse ovary

In mammalian ovaries, a fixed population of primordial follicles forms during the perinatal stage and the oocytes contained within are arrested at the dictyate stage of meiotic prophase I. In the current study, we provide evidence that the level of cyclic AMP (cAMP) in oocytes regulates oocyte meiotic prophase I and primordial folliculogenesis in the perinatal mouse ovary. Our results show that the early meiotic development of oocytes is closely correlated with increased levels of intra-oocyte cAMP. Inhibiting cAMP synthesis in fetal ovaries delayed oocyte meiotic progression and inhibited the disassembly and degradation of synaptonemal complex protein 1. In addition, inhibiting cAMP synthesis in in vitro cultured fetal ovaries prevented primordial follicle formation. Finally, using an in situ oocyte chromosome analysis approach, we found that the dictyate arrest of oocytes is essential for primordial follicle formation under physiological conditions. Taken together, these results suggest a role for cAMP in early meiotic development and primordial follicle formation in the mouse ovary.

The gene expression profile of cumulus cells reveals altered pathways in patients with endometriosis

PURPOSE

The objective of this experimental study was to compare the global gene expression profile of CC of mature oocytes in 18 patients with severe endometriosis and CC in 18 control patients affected by a severe male factor.

METHODS

For each group, the CC were pooled, RNA was extracted and a microarray performed. For validating the microarray, a quantitative real-time PCR was performed in the CC of an independent set of patients with endometriosis (n = 5) and controls (n = 7).

RESULTS

595 differentially expressed genes (320 down-regulated, 275 up-regulated, p < 0.05, fold change ≥1.5) were identified. The most significant changes were observed in genes involved in the chemokine signaling and cell-cell or cell-extracellular matrix adhesion pathways. Several genes of these pathways were down-regulated in endometriosis. Individual RT-PCR assays confirmed the microarray for ten genes.

CONCLUSIONS

Several genes involved in the chemokine mediated-signaling pathway and in the functional cross-talk between CC and the oocyte are down-regulated in endometriosis CC. The impairment of these processes could explain the reduction of oocyte competence in endometriosis. This preliminary knowledge could be the starting point for a more detailed elucidation of the relationship between endometriosis and oocyte competence.

Postnatal ovary development in the rat: morphologic study and correlation of morphology to neuroendocrine parameters

Histopathologic examination of the immature ovary is a required end point on juvenile toxicity studies and female pubertal and thyroid function assays. To aid in this evaluation and interpretation of the immature ovary, the characteristic histologic features of rat ovary through the developmental periods are described. These histologic features are correlated with published changes in neuroendocrine profiles as the hypothalamic-pituitary-gonadal axis matures. During the neonatal stage (postnatal day [PND] 0-7), ovarian follicle development is independent of pituitary gonadotropins (luteinizing hormone [LH] or follicle-stimulating hormone [FSH]), and follicles remain preantral. Antral development of "atypical" follicles occurs in the early infantile period (PND 8-14) when the ovary becomes responsive to pituitary gonadotropins. In the late infantile period (PND 15-20), the zona pellucida appears, the hilus forms, and antral follicles mature by losing their "atypical" appearance. The juvenile stage (PND 21-32) is the stage when atresia of medullary follicles occurs corresponding to a nadir in FSH levels. In the peripubertal period (PND 33-37), atresia subsides as FSH levels rebound, and LH begins its bimodal surge pattern leading to ovulation. This report will provide pathologists with baseline morphologic and endocrinologic information to aid in identification and interpretation of xenobiotic effects in the ovary of the prepubertal rat.

The role of the CCN family of proteins in female reproduction

The CCN family of proteins consists of six high homologous matricellular proteins which act predominantly by binding to heparin sulphate proteoglycan and a variety of integrins. Interestingly, CCN proteins are regulated by ovarian steroid hormones and are able to adapt to changes in oxygen concentration, which is a necessary condition for successful implantation. CCN1 is involved in processes of angiogenesis within reproductive systems, thereby potentially contributing to diseases such as endometriosis and disturbed angiogenesis in the placenta and fetus. In the ovary, CCN2 is the key factor for follicular development, ovulation and corpora luteal luteolysis, and its deletion leads to fertility defects. CCN1, CCN2 and CCN3 seem to be regulators for human trophoblast proliferation and migration, but with CCN2 acting as a counterweight. Alterations in the expression of these three proteins could contribute to the shallow invasion properties observed in preeclampsia. Little is known about the role of CCN4-6 in the reproductive organs. The ability of CCN1, CCN2 and CCN3 to interact with numerous receptors enables them to adapt their biological function rapidly to the continuous remodelling of the reproductive organs and in the development of the placenta. The CCN proteins mediate their specific cell physiological function through the receptor type of their binding partner followed by a defined signalling cascade. Because of their partly overlapping expression patterns, they could act in a concert synergistically or in an opposite way within the reproductive organs. Imbalances in their expression levels are correlated to different human reproductive diseases, such as endometriosis and preeclampsia.

Transforming growth factor-β signaling participates in the maintenance of the primordial follicle pool in the mouse ovary

Physiologically, only a few primordial follicles are activated to enter the growing follicle pool each wave. Recent studies in knock-out mice show that early follicular activation depends on signaling from the tuberous sclerosis complex, the mammalian target of rapamycin complex 1 (mTORC1), phosphatase and tensin homolog deleted on chromosome 10, and phosphatidylinositol 3-kinase (PI3K) pathways. However, the manner in which these pathways are normally regulated, and whether or not TGF-β acts on them are poorly understood. So, this study aims to identify whether or not TGF-β acts on the process. Ovary organ culture experiments showed that the culture of 18.5 days post-coitus (dpc) ovaries with TGF-β1 reduced the total population of oocytes and activated follicles, accelerated oocyte growth was observed in ovaries treated with TGF-βR1 inhibitor 2-(5-chloro-2-fluorophenyl)pteridin-4-yl]pyridin-4-yl-amine (SD208) compared with control ovaries, the down-regulation of TGF-βR1 gene expression also activated early primordial follicle oocyte growth. We further showed that there was dramatically more proliferation of granulosa cells in SD208-treated ovaries and less proliferation in TGF-β1-treated ovaries. Western blot and morphological analyses indicated that TGF-β signaling manipulated primordial follicle growth through tuberous sclerosis complex/mTORC1 signaling in oocytes, and the mTORC1-specific inhibitor rapamycin could partially reverse the stimulated effect of SD208 on the oocyte growth and decreased the numbers of growing follicles. In conclusion, our results suggest that TGF-β signaling plays an important physiological role in the maintenance of the dormant pool of primordial follicles, which functions through activation of p70 S6 kinase 1 (S6K1)/ribosomal protein S6 (rpS6) signaling in mouse ovaries.

Differential gene expression of granulosa cells after ovarian superstimulation in beef cattle

Microarray analysis was used to compare the gene expression of granulosa cells from dominant follicles with that of those after superstimulatory treatment. Cows were allocated randomly to two groups (superstimulation and control, n=6/group). A new follicular wave was induced by ablation of follicles ≥5 mm in diameter, and a progesterone-releasing device controlled internal drug release (CIDR) was placed in the vagina. The superstimulation group was given eight doses of 25 mg FSH at 12-h intervals starting from the day of wave emergence (day 0), whereas the control group was not given FSH treatment. Both groups were given prostaglandin F2α twice, 12 h apart, on day 3 and the CIDR was removed at the second injection; 25 mg porcine luteinizing hormone (pLH) was given 24 h after CIDR removal, and cows were ovariectomized 24 h later. Granulosa cells were collected for RNA extraction, amplification, and microarray hybridization. A total of 190 genes were downregulated and 280 genes were upregulated. To validate the microarray results, five genes were selected for real-time PCR (NTS, FOS, THBS1, FN1, and IGF2). Expression of four genes increased significantly in the three different animals tested (NTS, FOS, THBS1, and FN1). The upregulated genes are related to matrix remodeling (i.e. tissue proliferation), disturbance of angiogenesis, apoptosis, and oxidative stress response. We conclude that superstimulation treatment i) results in granulosa cells that lag behind in maturation and differentiation (most of the upregulated genes are markers of the follicular growth stage), ii) activates genes involved with the NFE2L2 oxidative stress response and endoplasmic reticulum stress response, and iii) disturbs angiogenesis.

Short-term culture of ovarian cortical strips from capuchin monkeys (Sapajus apella): a morphological, viability, and molecular study of preantral follicular development in vitro

The aim of this study was to evaluate whether an in vitro culture (IVC) medium containing either or not β-mercaptoethanol (BME), bone morphogenetic protein 4 (BMP4), or pregnant mare serum gonadotrophin (PMSG) could be able to promote the development of capuchin monkeys' preantral follicles enclosed in ovarian cortical strips. Follicular viability after IVC was similar to control (89.32%). Primordial follicle recruitment to primary stage was not reached with IVC, but the rate of secondary follicle formation was increased in the medium supplemented with BME, BMP4, and PMSG (44.86%) when compared to IVC control (9.20%). In the medium supplemented with BME, BMP4, and PMSG, contrary to other media, anti-müllerian hormone-messenger RNA (mRNA) expression in ovarian tissue was upregulated (3.4-fold), while that of growth differentiation factor-9 was maintained. The BMP4-mRNA expression, however, appeared downregulated in all cultured tissues. Our findings show a favorable effect of BME, BMP4, and PMSG on the in vitro development of secondary follicles from capuchin monkeys.

Gene bionetworks that regulate ovarian primordial follicle assembly

Background

Primordial follicle assembly is the process by which ovarian primordial follicles are formed. During follicle assembly oocyte nests break down and a layer of pre-granulosa cells surrounds individual oocytes to form primordial follicles. The pool of primordial follicles formed is the source of oocytes for ovulation during a female’s reproductive life.

Results

The current study utilized a systems approach to detect all genes that are differentially expressed in response to seven different growth factor and hormone treatments known to influence (increase or decrease) primordial follicle assembly in a neonatal rat ovary culture system. One novel factor, basic fibroblast growth factor (FGF2), was experimentally determined to inhibit follicle assembly. The different growth factor and hormone treatments were all found to affect similar physiological pathways, but each treatment affected a unique set of differentially expressed genes (signature gene set). A gene bionetwork analysis identified gene modules of coordinately expressed interconnected genes and it was found that different gene modules appear to accomplish distinct tasks during primordial follicle assembly. Predictions of physiological pathways important to follicle assembly were validated using ovary culture experiments in which ERK1/2 (MAPK1) activity was increased.

Conclusions

A number of the highly interconnected genes in these gene networks have previously been linked to primary ovarian insufficiency (POI) and polycystic ovarian disease syndrome (PCOS). Observations have identified novel factors and gene networks that regulate primordial follicle assembly. This systems biology approach has helped elucidate the molecular control of primordial follicle assembly and provided potential therapeutic targets for the treatment of ovarian disease.

Immune regulation of ovarian development: programming by neonatal immune challenge

Neonatal immune challenge by administration of lipopolysaccharide (LPS) produces enduring alterations in the development and activity of neuroendocrine, immune and other physiological systems. We have recently reported that neonatal exposure to an immune challenge by administration of LPS results in altered reproductive development in the female Wistar rat. Specifically, LPS-treated animals exhibited diminished ovarian reserve and altered reproductive lifespan. In the current study, we examined the cellular mechanisms that lead to the previously documented impaired ovulation and reduced follicular pool. Rats were administered intraperitoneally either 0.05 mg/kg of LPS (Salmonella Enteritidis) or an equivalent volume of non-pyrogenic saline on postnatal days (PNDs) 3 and 5, and ovaries were obtained on PND 7. Microarray analysis revealed a significant upregulation in transcript expression (2-fold change; p < 0.05) for a substantial number of genes in the ovaries of LPS-treated animals, implicated in immune cell signaling, inflammatory responses, reproductive system development and disease. Several canonical pathways involved in immune recognition were affected by LPS treatment, such as nuclear factor-κB (NF-κB) activation and LPS-stimulated mitogen-activated protein kinase (MAPK) signaling. Quantitative Real-time PCR analysis supported the microarray results. Protein expression analysis of several components of the MAPK signaling pathway revealed a significant upregulation in the expression of Toll-like receptor 4 (TLR4) in the neonatal ovary of LPS-treated animals. These results indicate that neonatal immune challenge by administration of LPS has a direct effect on the ovary during the sensitive period of follicular formation. Given the pivotal role of inflammatory processes in the regulation of reproductive health, our findings suggest that early life immune activation via TLR signaling may have significant implications for the programming of ovarian development and fertility.

Signaling modalities during oogenesis in mammals

During oogenesis in mammals, the germ line interacts with ovarian somatic cells as follicles assemble, grow, ovulate, and die. As a result, these interactions with granulosa cells determine germ cell fate as the oocyte undergoes hypertrophy, the final stages of meiosis, and preparations required for successful fertilization. Over the past 15 years, investigators using a range of experimental approaches have uncovered the existence of multiple modalities for signaling between the oocyte and companion granulosa cells that play essential and sometimes overlapping roles during the growth and maturative phases of oogenesis. Five modalities of intercellular signaling are considered in the context of regulating oocyte gene expression, metabolism, spatial patterning, and the cell cycle. While some forms of signaling predominate at specific stages of oogenesis, such as during the assembly of primordial follicles, it is apparent that combinations of modalities work in concert to control events associated with ovulation when both nuclear and cytoplasmic maturation occur. A final key feature of the signaling platform underscoring the protracted process of oogenesis is the existence of negative and positive feedback loops designed to coordinate the tempo of oogenesis and folliculogenesis at key developmental transitions.

Differential expression of CTGF in pre- and post-ovulatory granulosa cells in the hen ovary is regulated by TGFβ1 and gonadotrophins

Connective tissue growth factor (CTGF) is a cysteine-rich, matrix-associated heparin-binding protein that is important in many cell types as a regulator of cell proliferation, angiogenesis, cell remodelling and other cellular processes. CTGF is necessary for normal follicle growth and luteinisation in mammals. The avian follicular hierarchy provides an excellent experimental model to study developmental events, particularly the role of cellular remodelling factors in the process of folliculogenesis. In this study, we examined CTGF expression and regulation in the hen ovary. CTGF expression was increased considerably as follicular development proceeds in pre-ovulatory follicles, peaking in expression at the time of ovulation. Immunohistochemistry revealed that CTGF protein was concentrated in the cytoplasm of follicular granulosa cells throughout the ovulation cycle. We isolated granulosa cells from the follicles at two key stages of the ovulation cycle (in terms of cellular alteration): during pre-ovulatory growth and during post-ovulatory regression. Follicle-stimulating hormone (FSH) and luteinising hormone (LH) inhibited CTGF expression in pre-ovulatory granulosa cells but stimulated CTGF expression in post-ovulatory granulosa cells. Moreover, TGFβ1 stimulated CTGF expression in both pre- and post-ovulatory granulosa cells. Nevertheless, TGFβ1 could rescue the inhibition of gonadotrophins on pre-ovulatory granulosa CTGF expression but could not further stimulate CTGF expression in gonadotrophin-treated post-ovulatory granulosa cells. The results of this study indicate that CTGF expression in avian granulosa cells is modulated by a combination of gonadotrophins and TGFβ1 according to the different stages of follicle maturation and degradation. The results also suggest that the gonadotrophic action on post-ovulatory follicles in the avian ovary differs from the gonadotrophin-induced luteinisation in mammals.

[Molecular characterization of corona radiata cells from patients with diminished ovarian reserve]

OBJECTIVES

Diminished ovarian reserve (DOR) is one of the causes of infertility. In this prospective study, gene expression profiling (GEP) of corona radiata cells (CRC) was performed to identify genes deregulated in DOR patients.

PATIENTS AND METHODS

Microarray-based GEP of CRC isolated from eight women undergoing IVF was performed to identify genes differentially expressed between patients with normal ovarian reserve and DOR patients. Microfluidic-based quantitative RT-PCR assay were used to validate selected transcripts on 40 independent patients.

RESULTS

Forty-eight transcripts were differentially expressed, including CXXC5 and FOXC1 down regulated in DOR, as well as CTGF, FSTL3, PTGS2 and SOCS2 up regulated in DOR. According to these transcripts, two DOR patients'subgroups (DOR Gr1 and Gr2) were identified. In DOR Gr2 patients, CITED2, CTGF, GAS-1, IRS2, PTGS2, SOCS2, VCAN were expressed at significantly higher levels, and CXXC5, FOXC1, GBP2 and ZMIZ1 at significantly lower level. Eleven of those genes are transcriptional targets of Estrogens and higher baseline oestradiol levels were observed in DOR Gr2 patients (P<0.006).

DISCUSSION AND CONCLUSION

Twelve genes deregulated in CRC of DOR patients were identified, which could be involved in DOR pathogenesis. The distinction of a particular subgroup of DOR patients suggests the possibility of deregulation of estrogen response genes.

Neonatal immune challenge alters reproductive development in the female rat

Neonatal lipopolysaccharide (LPS) exposure alters neuroendocrine, immune and behavioural responses in adult rats. Recent findings indicate that neonatal LPS treatment may have a more pronounced effect on the mating behaviours of females compared to males. The current study further explored the impact of neonatal inflammation on reproductive development in the female rat. Wistar rats were administered LPS (0.05 mg/kg, i.p.) or saline (equivolume) on postnatal days (PNDs) 3 and 5. The immediate effect of treatment was assessed on plasma corticosterone and tyrosine hydroxylase (TH) phosphorylation in the adrenal medulla. Weight gain and vaginal opening were recorded, and oestrous cyclicity was monitored post-puberty and in late adulthood. Blood and ovaries were collected throughout development to assess HPA and HPG hormones and to examine ovarian morphology. Reproductive success in the first (F1) generation and reproductive development in the second (F2) generation were also assessed. Neonatal LPS exposure resulted in increased TH phosphorylation in the neonatal adrenals. LPS treatment increased the corticosterone concentrations of females as juveniles, adolescents and adults, and reduced FSH in adolescence. Increased catch-up growth was evident in LPS-treated females, prompting earlier onset of puberty. Diminished follicular reserve was observed in neonatally LPS-treated females along with the advanced reproductive senescence. While fertility rates were not compromised, higher mortality and morbidity were observed in litters born to LPS-treated mothers. Female offspring of LPS-treated mothers displayed increased corticosterone on PND 14, increased catch-up growth and delayed emergence of the first oestrous cycle. No differences in any of the parameters assessed were observed in F2 males. These data suggest that neonatal immunological challenge has a profound impact on the female reproductive development, via the alteration of metabolic and neuroendocrine factors which regulate sexual maturation. Evidence of altered development in the female, but not male offspring of LPS-treated dams suggests increased susceptibility of females to the deleterious effects of neonatal immunological stress and its possible transferability to a subsequent generation.

Oogenesis: transcriptional regulators and mouse models

Oocyte differentiation into a totipotent cell requires initial germ cell cyst breakdown to form primordial follicles, recruitment of primordial follicles for development into primary follicles and remarkable growth of the ovarian follicle which culminates in ovulation. During oogenesis, the oocyte undergoes dynamic alterations in gene expression which are regulated by a set of well-coordinated transcription factors active in the germ line and soma. A number of germ cell specific as well as somatic expressed transcriptional regulators are critical in ovarian formation and folliculogenesis. These transcriptional regulators include: Foxo3, Foxl2, Figla, Lhx8, Nobox, Sohlh1 and Sohlh2. A subset of these transcriptional regulators is mutated in women with ovarian insufficiency and infertility. Studies on transcriptional regulators preferentially expressed in the ovary are important to develop a better understanding of the mechanisms of activation and survival of ovarian follicles, as well as an understanding of ovary specific pathways that can be modulated in the future to regulate fertility and protect against external insults such as chemotherapy.

Environmentally induced epigenetic transgenerational inheritance of ovarian disease

The actions of environmental toxicants and relevant mixtures in promoting the epigenetic transgenerational inheritance of ovarian disease was investigated with the use of a fungicide, a pesticide mixture, a plastic mixture, dioxin and a hydrocarbon mixture. After transient exposure of an F0 gestating female rat during embryonic gonadal sex determination, the F1 and F3 generation progeny adult onset ovarian disease was assessed. Transgenerational disease phenotypes observed included an increase in cysts resembling human polycystic ovarian disease (PCO) and a decrease in the ovarian primordial follicle pool size resembling primary ovarian insufficiency (POI). The F3 generation granulosa cells were isolated and found to have a transgenerational effect on the transcriptome and epigenome (differential DNA methylation). Epigenetic biomarkers for environmental exposure and associated gene networks were identified. Epigenetic transgenerational inheritance of ovarian disease states was induced by all the different classes of environmental compounds, suggesting a role of environmental epigenetics in ovarian disease etiology.

Effect of androgen treatment during foetal and/or neonatal life on ovarian function in prepubertal and adult rats

We investigated the effects of different windows of testosterone propionate (TP) treatment during foetal and neonatal life in female rats to determine whether and when excess androgen exposure would cause disruption of adult reproductive function. Animals were killed prepubertally at d25 and as adults at d90. Plasma samples were taken for hormone analysis and ovaries serial sectioned for morphometric analyses. In prepubertal animals, only foetal+postnatal and late postnatal TP resulted in increased body weights, and an increase in transitory, but reduced antral follicle numbers without affecting total follicle populations. Treatment with TP during both foetal+postnatal life resulted in the development of streak ovaries with activated follicles containing oocytes that only progressed to a small antral (smA) stage and inactive uteri. TP exposure during foetal or late postnatal life had no effect upon adult reproductive function or the total follicle population, although there was a reduction in the primordial follicle pool. In contrast, TP treatment during full postnatal life (d1-25) resulted in anovulation in adults (d90). These animals were heavier, had a greater ovarian stromal compartment, no differences in follicle thecal cell area, but reduced numbers of anti-Mullerian hormone-positive smA follicles when compared with controls. Significantly reduced uterine weights lead reduced follicle oestradiol production. These results support the concept that androgen programming of adult female reproductive function occurs only during specific time windows in foetal and neonatal life with implications for the development of polycystic ovary syndrome in women.

Follicular assembly: mechanisms of action

The differentiation of primordial germ cells (PGCs) into functional oocytes is important for the continuation of species. In mammals, PGCs begin to differentiate into oocytes during embryonic development. Oocytes develop in clusters called germ line cysts. During fetal or neonatal development, germ cell cysts break apart into single oocytes that become surrounded by pregranulosa cells to form primordial follicles. During the process of cyst breakdown, a subset of cells in each cyst undergoes cell death with only one-third of the initial number of oocytes surviving to form primordial follicles. The mechanisms that control cyst breakdown, oocyte survival, and follicle assembly are currently under investigation. This review describes the mechanisms that have been implicated in the control of primordial follicle formation, which include programmed cell death regulation, growth factor and other signaling pathways, regulation by transcription factors and hormones, meiotic progression, and changes in cell adhesion. Elucidation of mechanisms leading to formation of the primordial follicle pool will help research efforts in ovarian biology and improve treatments of female infertility, premature ovarian failure, and reproductive cancers.

Connective tissue growth factor is required for normal follicle development and ovulation

Connective tissue growth factor (CTGF) is a cysteine-rich protein the synthesis and secretion of which are hypothesized to be selectively regulated by activins and other members of the TGF-β superfamily. To investigate the in vivo roles of CTGF in female reproduction, we generated Ctgf ovarian and uterine conditional knockout (cKO) mice. Ctgf cKO mice exhibit severe subfertility and multiple reproductive defects including disrupted follicle development, decreased ovulation rates, increased numbers of corpus luteum, and smaller but functionally normal uterine horns. Steroidogenesis is disrupted in the Ctgf cKO mice, leading to increased levels of serum progesterone. We show that disrupted follicle development is accompanied by a significant increase in granulosa cell apoptosis. Moreover, despite normal cumulus expansion, Ctgf cKO mice exhibit a significant decrease in oocytes ovulated, likely due to impaired ovulatory process. During analyses of mRNA expression, we discovered that Ctgf cKO granulosa cells show gene expression changes similar to our previously reported granulosa cell-specific knockouts of activin and Smad4, the common TGF-β family intracellular signaling protein. We also discovered a significant down-regulation of Adamts1, a progesterone-regulated gene that is critical for the remodeling of extracellular matrix surrounding granulosa cells of preovulatory follicles. These findings demonstrate that CTGF is a downstream mediator in TGF-β and progesterone signaling cascades and is necessary for normal follicle development and ovulation.

Inhibitory actions of Anti-Müllerian Hormone (AMH) on ovarian primordial follicle assembly

The current study was designed to investigate the actions of Anti-Müllerian Hormone (AMH) on primordial follicle assembly. Ovarian primordial follicles develop from the breakdown of oocyte nests during fetal development for the human and immediately after birth in rodents. AMH was found to inhibit primordial follicle assembly and decrease the initial primordial follicle pool size in a rat ovarian organ culture. The AMH expression was found to be primarily in the stromal tissue of the ovaries at this period of development, suggesting a stromal-epithelial cell interaction for primordial follicle assembly. AMH was found to promote alterations in the ovarian transcriptome during primordial follicle assembly with over 200 genes with altered expression. A gene network was identified suggesting a potential central role for the Fgf2/Nudt6 antisense transcript in the follicle assembly process. A number of signal transduction pathways are regulated by AMH actions on the ovarian transcriptome, in particular the transforming growth factor – beta (TGFß) signaling process. AMH is the first hormone/protein shown to have an inhibitory action on primordial follicle assembly. Due to the critical role of the primordial follicle pool size for female reproduction, elucidation of factors, such as AMH, that regulate the assembly process will provide insights into potential therapeutics to manipulate the pool size and female reproduction.

Basic helix-loop-helix transcription factor TCF21 is a downstream target of the male sex determining gene SRY

The cascade of molecular events involved in mammalian sex determination has been shown to involve the SRY gene, but specific downstream events have eluded researchers for decades. The current study identifies one of the first direct downstream targets of the male sex determining factor SRY as the basic-helix-loop-helix (bHLH) transcription factor TCF21. SRY was found to bind to the Tcf21 promoter and activate gene expression. Mutagenesis of SRY/SOX9 response elements in the Tcf21 promoter eliminated the actions of SRY. SRY was found to directly associate with the Tcf21 promoter SRY/SOX9 response elements in vivo during fetal rat testis development. TCF21 was found to promote an in vitro sex reversal of embryonic ovarian cells to induce precursor Sertoli cell differentiation. TCF21 and SRY had similar effects on the in vitro sex reversal gonadal cell transcriptomes. Therefore, SRY acts directly on the Tcf21 promoter to in part initiate a cascade of events associated with Sertoli cell differentiation and embryonic testis development.