Granulosa cell proliferation is impaired in the Igf1 null ovary

Roles of GDF9 and BMP15 in equine follicular development: in vivo content and in vitro effects of IGF1 and cortisol on granulosa cells

BACKGROUND

In horses, the mechanisms behind ovarian follicle growth and oocyte maturation remain largely unknown. In other species, oocyte-secreted factors growth differentiation factor 9 (GDF9) and bone morphogenetic protein 15 (BMP15) have been related to the acquisition of developmental competence and to interaction with granulosa cells for the regulation of follicle development. This study assessed the expression and localization of GDF9 in the equine ovary, and its possible relationship with granulosa cell function.

RESULTS

Using custom-made antibodies, GDF9 protein was localized in oocytes from the primary follicle stage onwards. Together with BMP15, its intrafollicular concentration was higher in small antral follicles compared to larger ones (P < 0.05). Negative correlations were observed between intrafollicular BMP15 concentration and estradiol sulfate (E2S) (r = -0.36, P = 0.048), as well as between BMP15 and E2S/P4 ratio (r = -0.37, P = 0.046). In vivo, equine granulosa cells showed increasing mRNA expression of genes involved in steroidogenesis (STAR and HSD3B2) and cell proliferation (KI67) with increasing follicle size, while expression of GDF9 and of apoptosis-related genes (BCL2 and CASP3) were not affected by follicle size. Simultaneous stimulation of granulosa cells in vitro with IGF1 and cortisol significantly increased HSD3B2 and CYP19A1 transcriptional levels, as well as E2 concentration in culture media, while IGF1-induced P4 secretion was suppressed in the presence of cortisol. Blocking the stimulatory effect of IGF1 on E2, E2S and P4 by H89 was associated with increased GDF9 mRNA levels and reduced STAR, PCNA, KI67 and BCL2 mRNA expression. Significant negative correlations of GDF9 with STAR and PCNA mRNA, respectively, were seen in vivo and in vitro.

CONCLUSIONS

Together, our results show GDF9 localization and expression in the equine ovary and a temporal relationship with steroidogenesis and cell proliferation within the surrounding granulosa cells. Moreover, results of the in vitro study suggest a supporting role of cortisol during follicle maturation. Our study sheds light on possible mechanisms for the regulation of ovarian function in horses using GDF9.

Acephate Exposure Induces Transgenerational Ovarian Developmental Toxicity by Altering the Expression of Follicular Growth Markers in Female Rats

Acephate is an organophosphate foliar and soil insecticide that is used worldwide. In this study, the transgenerational ovarian developmental toxicity caused by acephate, along with its in utero reprogramming mechanisms, were explored. Thirty female virgin Wistar albino rats were randomly assigned to three groups: one control group and two acephate treatment groups. The treatment groups received daily low or high doses of acephate (34.2 mg/kg or 68.5 mg/kg body weight, respectively) from gestational day 6 until spontaneous labor, resulting in F1 offspring. At 28 days, a subgroup of F1 females were euthanized. The ovaries were extracted, thoroughly cleaned, and weighed before being fixed for further analysis. The remaining F1 females were mated with normal males to produce the F2 generation. The F1 female offspring presented reduced fertility and body weight, whereas the ovarian weight index and sex ratio increased in a dose-dependent manner. Structural analysis revealed altered follicular abnormalities with ovarian cells displaying pyknotic nuclei. Additionally, the gene and protein expression of Cyp19 decreased, whereas that of Gdf-9 increased in the high-dose treatment group (68.5 mg/kg). We also observed significantly increased expression levels of ovarian estrogen receptor 1 (Esr1) and insulin-like growth factor 1 (Igf1), whereas Insl3 expression was significantly decreased. The F2 female offspring presented reproductive phenotype alterations similar to those of F1 females including decreased fertility, reduced Cyp19 gene and protein expression, and structural ovarian abnormalities similar to those of polycystic ovary syndrome (PCOS). In conclusion, acephate induced ovarian developmental toxicity across two generations of rats, which may be linked to changes in the ovarian Cyp19, Gdf9, Insl3, and Igf1 levels.

Inhibitor of DNA Binding Protein 2 (ID2) Mediates the Anti-Proliferative and Pro-Differentiation Effects of Insulin-like Growth Factor-1 (IGF-1)

In preeclampsia (PE), impaired trophoblast proliferation and differentiation are thought to cause abnormal placentation and subsequent clinical manifestations of the disease, i.e., hypertension, proteinuria, and end-organ damage. Insulin-like growth factor-1 (IGF-1) influences trophoblast cell function; however, the mechanism of IGF-1's action on trophoblasts is not understood well. Inhibitor of DNA binding protein 2 (ID2) is involved in trophoblast differentiation and implicated in many processes disrupted in PE, including placental development, vascular differentiation, and angiogenesis. We hypothesized that IGF-1 regulates trophoblast proliferation and differentiation via ID2. Immortalized human first trimester trophoblast cells (HTR-8/SVneo) were treated with IGF-1 for 24 h after serum starvation. ID2 mRNA and protein were measured, as well as trophoblast cell viability, proliferation, tube formation, and migration. IGF-1 decreased ID2 expression in a dose-dependent manner. IGF-1 decreased trophoblast proliferation but increased cell viability, differentiation, and migration. ID2 overexpression mitigated the effects of IGF-1 on trophoblast cells. These data suggest that IGF-1 could regulate trophoblast proliferation and differentiation through ID2. The dysregulation of ID2-mediated IGF-1 signaling in trophoblast cells could be involved in the pathogenesis of pregnancy disorders like uterine growth restriction and PE.

Expression and in vitro effect of phoenixin-14 on the porcine ovarian granulosa cells

Phoenixin-14 (PNX-14) regulates energy metabolism via the G protein-coupled receptor 173 (GPR173); elevated plasma levels have been described in patients with polycystic ovary syndrome. The aims were to investigate the ovarian expression of PNX-14/GPR173 and the in vitro effect of PNX-14 on granulosa cells (Gc) function. Transcript and protein levels of PNX-14/GRP173 were analysed by real-time PCR, western blot and immunohistochemistry in the porcine ovarian follicles at days 2-3, 10-12 and 16-18 of the oestrous. For in vitro experiments, Gc were isolated from follicles at days 10-12 of the oestrous (4-6 mm) and PNX-14 at doses 1-1000 nM was added for 24-72 h to determine Gc proliferation. Cell cycle progression, E2 secretion, expression of proliferating cells nuclear antigen, cyclins, mitogen-activated kinase (MAP3/1; ERK1/2), protein kinase B (AKT) and signal transducer and activator of transcription 3 (STAT3) were studied. The involvement of these kinases in PNX-14 action on Gc proliferation was analysed using pharmacological inhibitors. Levels of GPR173 were increased in the ovarian follicles with oestrous progression, while only PNX-14 protein was the highest at days 10-12 of the oestrous. Immuno-signal of PNX-14 was detected in Gc and theca cells and oocyte, while GPR173 was mostly in theca. Interestingly, PNX-14 stimulated Gc proliferation, E2 secretion, cell cycle progression and cyclins expression and had a modulatory effect on MAP3/1, AKT and STAT3 activation. Our study suggests that PNX-14 could be an important factor for porcine reproduction by influencing ovarian follicle growth through direct action on Gc function.

Molecular crosstalk between insulin-like growth factors and follicle-stimulating hormone in the regulation of granulosa cell function

Background

The last phase of folliculogenesis is driven by follicle-stimulating hormone (FSH) and locally produced insulin-like growth factors (IGFs), both essential for forming preovulatory follicles.

Methods

This review discusses the molecular crosstalk of the FSH and IGF signaling pathways in regulating follicular granulosa cells (GCs) during the antral-to-preovulatory phase.

Main findings

IGFs were considered co-gonadotropins since they amplify FSH actions in GCs. However, this view is not compatible with data showing that FSH requires IGFs to stimulate GCs, that FSH renders GCs sensitive to IGFs, and that FSH signaling interacts with factors downstream of AKT to stimulate GCs. New evidence suggests that FSH and IGF signaling pathways intersect at several levels to regulate gene expression and GC function.

Conclusion

FSH and locally produced IGFs form a positive feedback loop essential for preovulatory follicle formation in all species. Understanding the mechanisms by which FSH and IGFs interact to control GC function will help design new interventions to optimize follicle maturation, perfect treatment of ovulatory defects, improve in vitro fertilization, and develop new contraceptive approaches.

Bisphenol S and F affect cell cycle distribution and steroidogenic activity of human ovarian granulosa cells, but not primary granulosa tumour cells

Bisphenol S (BPS) and F (BPF), a new generation of bisphenols (BPs), are the main substitutes for bisphenol A (BPA). Both have been detected in human body fluids. Importantly, bisphenols are structurally similar to oestrogen, the main sex hormone in females. Because bisphenols bind to nuclear oestrogen receptors (ESR1 and ESR2) and to membrane G-coupled receptor 30 (GPR30), they can disrupt ovarian function. Here, we reveal the molecular mechanism underlying the effects of BPS and BPF on the cell cycle and steroidogenesis in the human ovarian granulosa cell (GC) line HGrC1. We show that BPS and BPF arrest GCs at the G0/G1 phase by inducing expression of cyclin D2, an important event that triggers maximal steroid synthesis in response to the BPS and BPF. We used pharmacological inhibitors to show that BPS and BPF, despite acting via already described pathways, also stimulate steroid secretion via IGF1R pathways in HGrC1 cells. Moreover, we identified differences critical to bisphenols response between normal (HGrC1) and primary tumour granulosa (COV434) cells, that enable COV434 cells to be more resistant to bisphenols. Overall, the data suggest that BPS and BPF drive steroidogenesis in human ovarian GCs by affecting the cell cycle. Furthermore, the results indicate that BPS and BPF act not only via the classical and non-classical ESR pathways, but also via the IGF1R pathway.

Role of insulin-like growth factor 1 (IGF1) in the regulation of mitochondrial bioenergetics in zebrafish oocytes: lessons from in vivo and in vitro investigations

Optimal mitochondrial functioning is indispensable for acquiring oocyte competence and meiotic maturation, whilst mitochondrial dysfunction may lead to diminished reproductive potential and impaired fertility. The role of the intra-ovarian IGF system in ovarian follicular dynamics has been implicated earlier. Although several studies have demonstrated the role of the IGF axis in facilitating mitochondrial function over a multitude of cell lines, its role in oocyte energy metabolism remains largely unexplored. Here using zebrafish, the relative importance of IGF1 in modulating oocyte mitochondrial bioenergetics has been investigated. A dramatic increase in ovarian lhcgr and igf1 expression accompanied heightened ATP levels and mitochondrial polarization in full-grown (FG) oocytes resuming meiotic maturation and ovulation in vivo. Concomitant with elevated igf1 expression and IGF1R phosphorylation, hCG (LH analog) stimulation of FG follicles in vitro prompted a sharp increase in NRF-1 and ATP levels, suggesting a positive influence of gonadotropin action on igf1 expression vis-à-vis oocyte bioenergetics. While recombinant IGF1 administration enhanced mitochondrial function, IGF1R immunodepletion or priming with PI3K inhibitor wortmannin could abrogate NRF-1 immunoreactivity, expression of respiratory chain subunits, ΔΨ_M, and ATP content. Mechanistically, activation of PI3K/Akt signaling in IGF1-treated follicles corroborated well with the rapid phosphorylation of GSK3β at Ser9 (inactive) followed by PGC-1β accumulation. While selective inhibition of GSK3β promoted PGC-1β, Akt inhibition could abrogate IGF1-induced p-GSK3β (Ser9) and PGC-1β immunoreactive protein indicating Akt-mediated GSK3β inactivation and PGC-1β stabilization. The IGF1-depleted follicles showed elevated superoxide anions, subdued steroidogenic potential, and attenuated G2-M1 transition. In summary, this study highlights the importance of IGF1 signaling in oocyte bioenergetics prior to resumption of meiosis.

Alterations in gonadotropin, apoptotic and metabolic pathways in granulosa cells warrant superior fertility of the Dummerstorf high fertility mouse line 1

The development and maturation of ovarian follicles is a complex and highly regulated process, which is essential for successful ovulation. During recent decades, several mouse models provided insights into the regulation of folliculogenesis. In contrast to the commonly used transgenic or knockout mouse models, the Dummerstorf high-fertility mouse line 1 (FL1) is a worldwide unique selection experiment for increased female reproductive performance and extraordinary high fertility. Interactions of cycle-related alterations of parameters of the hypothalamic pituitary gonadal axis and molecular factors in the ovary lead to improved follicular development and therefore increased ovulation rates in FL1 mice. FL1 females almost doubled the number of ovulated oocytes compared to the unselected control mouse line. To gain insights into the cellular mechanisms leading to the high fertility phenotype we used granulosa cells isolated from antral follicles for mRNA sequencing. Based on the results of the transcriptome analysis we additionally measured hormones and growth factors associated with follicular development to complement the picture of how the signaling pathways are regulated. While IGF1 levels are decreased in FL1 mice in estrus, we found no differences in insulin, prolactin and oxytocin levels in FL1 mice compared to the control line. The results of the mRNA sequencing approach revealed that the actions of insulin, prolactin and oxytocin are restricted local to the granulosa cells, since hormonal receptor expression is differentially regulated in FL1 mice. Additionally, numerous genes, which are involved in important gonadotropin, apoptotic and metabolic signaling pathways in granulosa cells, are differentially regulated in granulosa cells of FL1 mice.We showed that an overlap of different signaling pathways reflects the crosstalk between gonadotropin and growth factor signaling pathways, follicular atresia in FL1 mice is decreased due to improved granulosa cell survival and by improving the efficiency of intracellular signaling, glucose metabolism and signal transduction, FL1 mice have several advantages in reproductive performance and therefore increased the ovulation rate. Therefore, this worldwide unique high fertility model can provide new insights into different factors leading to improved follicular development and has the potential to improve our understanding of high fertility.

A Possible Mechanism for Double-Yolked Eggs in the Early Stage of Egg-Laying in Zhedong White Goose-Function of IGF1 and LHR Signaling

The cause of double-yolk (DY) egg production in birds is unclear, but it is related to body weight and adiposity. We explored the causes of the high proportion (up to 26%) of DY eggs in the first clutch of Zhedong white geese. We recorded the egg production of Zhedong white geese during the first egg-laying cycle and counted the proportion of DY eggs. We found that 30% of geese had 3 sets of double or triple follicles of the same diameter in the abdomen, which was close to the DY egg rate. In addition, the mRNA expression levels of the steroidogenic acute regulatory protein (StAR) and luteinizing hormone receptor (LHR) genes in granulosa cells were similar within the same set of follicles. Furthermore, the IGF1 concentration in geese that had at least 3 sets of follicles of the same diameter was significantly higher than that in birds with 0-1 set of follicles of the same diameter. Thus, we proposed that, in the first egg-laying stage of geese, high plasma concentrations of IGF1 stimulate the development of pre-hierarchal follicles and cause more than one follicle to be selected at the same time, mature at the same rate under the same gonadotrophin milieu, and ovulate at the same time to produce DY eggs.

Stanniocalcin-1 in the female reproductive system and pregnancy

BACKGROUND

Stanniocalcin-1 (STC-1) is a widely expressed glycoprotein hormone involved in a diverse spectrum of physiological and pathophysiological processes including angiogenesis, mineral homeostasis, cell proliferation, inflammation and apoptosis. Over the last 20 years, numerous studies have reported STC-1 expression within female reproductive tissues including the uterus, ovaries and placenta and implicated STC-1 in processes such as ovarian follicular development, blastocyst implantation, vascular remodelling in early pregnancy and placental development. Notably, dysregulation of STC-1 within reproductive tissues has been linked to the onset of severe reproductive disorders including endometriosis, polycystic ovary syndrome, poor trophoblast invasion and placental perfusion in early pregnancy. Furthermore, significant changes in tissue expression and in maternal systemic concentration take place throughout pregnancy and further substantiate the vital role of this protein in reproductive health and disease.

OBJECTIVE AND RATIONALE

Our aim is to provide a comprehensive overview of the existing literature, to summarise the expression profile and roles of STC-1 within the female reproductive system and its associated pathologies. We highlight the gaps in the current knowledge and suggest potential avenues for future research.

SEARCH METHODS

Relevant studies were identified through searching the PubMed database using the following search terms: ‘stanniocalcin-1’, ‘placenta’, ‘ovary’, ‘endometrium’, ‘pregnancy’, ‘reproduction’, ‘early gestation’. Only English language papers published between 1995 and 2020 were included.

OUTCOMES

This review provides compelling evidence of the vital function that STC-1 plays within the female reproductive system. The literature presented summarise the wide expression profile of STC-1 within female reproductive organs, as well as highlighting the putative roles of STC-1 in various functions in the reproductive system. Moreover, the observed link between altered STC-1 expression and the onset of various reproductive pathologies is presented, including those in pregnancy whose aetiology occurs in the first trimester. This summary emphasises the requirement for further studies on the mechanisms underlying the regulation of STC-1 expression and function.

WIDER IMPLICATIONS

STC-1 is a pleiotropic hormone involved in the regulation of a number of important biological functions needed to maintain female reproductive health. There is also growing evidence that dysregulation of STC-1 is implicated in common reproductive and obstetric disorders. Greater understanding of the physiology and biochemistry of STC-1 within the field may therefore identify possible targets for therapeutic intervention and/or diagnosis.

Insulin-like growth factor-I prevents hypoxia-inducible factor-1 alpha-dependent G1/S arrest by activating cyclin E/cyclin-dependent kinase2 via the phoshatidylinositol-3 kinase/AKT/forkhead box O1/Cdkn1b pathway in porcine granulosa cells†

As the follicle develops, the thickening of the granulosa compartment leads to progressively deficient supply of oxygen in granulosa cells (GCs) due to the growing distances from the follicular vessels. These conditions are believed to cause hypoxia in GCs during folliculogenesis. Upon hypoxic conditions, several types of mammalian cells have been reported to undergo cell cycle arrest. However, it remains unclear whether hypoxia exerts any impact on cell cycle progression of GCs. On the other hand, although the GCs may live in a hypoxic environment, their mitotic capability appears to be unaffected in growing follicles. It thus raises the question whether there are certain intraovarian factors that might overcome the inhibitory effects of hypoxia. The present study provides the first evidence suggesting that cobalt chloride (CoCl2)-mimicked hypoxia prevented G1-to-S cell cycle progression in porcine GCs. In addition, we demonstrated that the inhibitory effects of CoCl2 on GCs cell cycle are mediated through hypoxia-inducible factor-1 alpha/FOXO1/Cdkn1b pathway. Moreover, we identified insulin-like growth factor-I (IGF-I) as an intrafollicular factor required for cell cycle recovery by binding to IGF-I receptor in GCs suffering CoCl2 stimulation. Further investigations confirmed a role of IGF-I in preserving G1/S progression of CoCl2-treated GCs via activating the cyclin E/cyclin-dependent kinase2 complex through the phoshatidylinositol-3 kinase/protein kinase B (AKT)/FOXO1/Cdkn1b axis. Although the present findings were based on a hypoxia mimicking model by using CoCl2, our study might shed new light on the regulatory mechanism of GCs cell cycle upon hypoxic stimulation.

IGF-1 Inhibits Apoptosis of Porcine Primary Granulosa Cell by Targeting Degradation of BimEL

Insulin-like growth factor-1 (IGF-1) is an intra-ovarian growth factor that plays important endocrine or paracrine roles during ovarian development. IGF-1 affects ovarian function and female fertility through reducing apoptosis of granulosa cells, yet the underlying mechanism remains poorly characterized. Here, we aimed to address these knowledge gaps using porcine primary granulosa cells and examining the anti-apoptotic mechanisms of IGF-1. IGF-1 prevented the granulosa cell from apoptosis, as shown by TUNEL and Annexin V/PI detection, and gained the anti-apoptotic index, the ratio of Bcl-2/Bax. This process was partly mediated by reducing the pro-apoptotic Bim_EL (Bcl-2 Interacting Mediator of Cell Death-Extra Long) protein level. Western blotting showed that IGF-1 promoted Bim_EL phosphorylation through activating p-ERK1/2, and that the proteasome system was responsible for degradation of phosphorylated Bim_EL. Meanwhile, IGF-1 enhanced the Beclin1 level and the rate of LC3 II/LC3 I, indicating that autophagy was induced by IGF-1. By blocking the proteolysis processes of both proteasome and autophagy flux with MG132 and chloroquine, respectively, the Bim_EL did not reduce and the phosphorylated Bim_EL protein accumulated, thereby indicating that both proteasome and autophagy pathways were involved in the degradation of Bim_EL stimulated by IGF-1. In conclusion, IGF-1 inhibited porcine primary granulosa cell apoptosis via degradation of pro-apoptotic Bim_EL. This study is critical for us to further understand the mechanisms of follicular survival and atresia regulated by IGF-1. Moreover, it provides a direction for the treatment of infertility caused by ovarian dysplasia, such as polycystic ovary syndrome and the improvement of assisted reproductive technology.

Female Age Affects the Mesenchymal Stem Cell Characteristics of Aspirated Follicular Cells in the In Vitro Fertilization Programme

Aspirated follicular cells (AFCs) from the in vitro fertilization program can express various stem cell markers and are even able to differentiate into different types of cells in vitro. The female reproductive potential decreases with increasing age due to lowered ovarian reserve and oocyte quality, but data on the effect of female age on stem cell characteristics of AFCs are scarce. Therefore, the aim of this study was to elucidate whether female age affects the mesenchymal stem cell (MSC) characteristics of AFCs. Follicular aspirates were collected from 12 patients included in the in vitro fertilization programme with a normal ovarian reserve. Patients were divided into four age groups: Group A ≤ 30 years, Group B 31-35 years, Group C 36-39 years and Group D ≥ 40 years. After removal of the oocytes, AFCs were collected from follicular aspirates using hypo-osmotic technique and cultured in vitro, and their stemness was compared according to female age. The cultured AFCs were analysed for gene expression using the Human Mesenchymal Stem Cell RT² Profiler™ PCR Array, for their potential for differentiation into adipogenic and osteogenic lineage, and for their expression of MSC-related markers using immunocytochemistry. We found that female age can significantly influence their stemness: expression of pluripotency and MSC-related genes, and their differentiation potential. Despite the relatively high expression of MSC-related genes, the AFCs of the oldest patients had the lowest potential to differentiate into osteogenic and adipogenic lineages in vitro, which may be related to their age and the changed ovarian function.

Folliculogenic factors in photoregressed ovaries: Differences in mRNA expression in early compared to late follicle development

The early stages of ovarian folliculogenesis generally progress independent of gonadotropins, whereas later stages require signaling initiated by FSH. In Siberian hamsters, cycles of folliculogenesis are mediated by changes in photoperiod which depress the hypothalamic pituitary gonadal axis. Reduced gonadotropins lead to decreases in mature follicle development and ovulation; however, early stages of folliculogenesis have not been explored in regressed ovaries. We hypothesized that intraovarian factors that contribute predominantly to later stages of folliculogenesis would react to changes in photoperiod, whereas factors contributing to earlier stages would not change. To probe if the early stages of folliculogenesis continue in the photoinhibited ovary while late stages decline, we measured the mRNA abundance of factors that interact with FSH signaling (Fshr, Igf1, Cox2) and factors that can function independently of FSH (c-Kit, Kitl, Foxo3, Figla, Nobox, Sohlh1, Lhx8). While plasma FSH, antral follicles, and corpora lutea numbers declined with exposure to inhibitory photoperiod, the numbers of primordial, primary, and secondary follicles did not change. Expression of factors that interact with FSH signaling changed with changes in photoperiod; however, expression of factors that do not interact with FSH were not significantly altered. These results suggest that the photoinhibited ovary is not completely quiescent, as factors important for follicle selection and early follicle growth are still expressed in regressed ovaries. Instead, the lack of gonadotropin support that characterizes the non-breeding season appears to inhibit only final stages of folliculogenesis in Siberian hamsters.

Human umbilical cord mesenchymal stem cells improve the reserve function of perimenopausal ovary via a paracrine mechanism

Background

Human umbilical cord mesenchymal stem cells (hUCMSCs) are a type of pluripotent stem cell which are isolated from the umbilical cord of newborns. hUCMSCs have great therapeutic potential. We designed this experimental study in order to investigate whether the transplantation of hUCMSCs can improve the ovarian reserve function of perimenopausal rats and delay ovarian senescence.

Method

We selected naturally aging rats confirmed by vaginal smears as models of perimenopausal rats, divided into the control group and the treatment group, and selected young fertile female rats as normal controls. hUCMSCs were transplanted into rats of the treatment group through tail veins. Enzyme-linked immunosorbent assay (ELISA) detected serum levels of sex hormones, H&E staining showed ovarian tissue structure and allowed follicle counting, immunohistochemistry and western blot analysis revealed ovarian expression of hepatocyte growth factor (HGF), vascular endothelial cell growth factor (VEGF), and insulin-like growth factor-1 (IGF-1), polymerase chain reaction (PCR) and western blot analysis revealed hUCMSCs expression of HGF, VEGF, and IGF-1.

Results

At time points of 14, 21, and 28 days after hUCMSCs transplantation, estradiol (E₂) and anti-Müllerian hormone (AMH) increased while follicle-stimulating hormone (FSH) decreased; ovarian structure improved and follicle number increased; ovarian expression of HGF, VEGF, and IGF-1 protein elevated significantly. Meanwhile, PCR and western blot analysis indicated hUCMSCs have the capacity of secreting HGF, VEGF, and IGF-1 cytokines.

Conclusions

Our results suggest that hUCMSCs can promote ovarian expression of HGF, VEGF, and IGF-1 through secreting those cytokines, resulting in improving ovarian reserve function and withstanding ovarian senescence.

Influence of exogenous supplementation of IGF-I, cysteamine and their combination on in vitro caprine blastocyst development

The present study was carried out to investigate the putative beneficial effects of insulin-like growth factor-I (IGF-I) and cysteamine supplementation alone or their combination on in vitro embryo development competence of fertilized goat oocytes. Presumptive zygotes (18 h post insemination) were randomly assigned for in vitro embryo development in embryo development medium (EDM) supplemented with IGF-I (Gr. 1), Cysteamine (Gr. 2), IGF- I + Cysteamine (Gr. 3) and Control containing only EDM (Gr. 4). Statistically non-significant difference was observed in cleavage rate among all the treated groups. Morula formation rate was significantly higher in IGF-I supplemented group compared to IGF-I + cysteamine supplemented and non-supplemented (control) groups. Furthermore, supplementation of IGF-I, cysteamine and IGF-I + cysteamine in embryo culture medium significantly improved blastocyst formation rate compared to control. However, a nonsignificant difference in blastocyst formation was observed among the supplemented groups. These findings lead to the conclusion that under in vitro conditions, supplementation of IGF-I and cysteamine alone or combination in IVC media were equally effective in embryo development and blastocyst production, however, this effect was significantly higher as compared to non- supplemented group (control).

Quantifying growing versus non-growing ovarian follicles in the mouse

Background

A standard histomorphometric approach has been used for nearly 40 years that identifies atretic (e.g., dying) follicles by counting the number of pyknotic granulosa cells (GC) in the largest follicle cross-section. This method holds that if one pyknotic granulosa nucleus is seen in the largest cross section of a primary follicle, or three pyknotic cells are found in a larger follicle, it should be categorized as atretic. Many studies have used these criteria to estimate the fraction of atretic follicles that result from genetic manipulation or environmental insult. During an analysis of follicle development in a mouse model of Fragile X premutation, we asked whether these ‘historical’ criteria could correctly identify follicles that were not growing (and could thus confirmed to be dying).

Methods

Reasoning that the fraction of mitotic GC reveals whether the GC population was increasing at the time of sample fixation, we compared the number of pyknotic nuclei to the number of mitotic figures in follicles within a set of age-matched ovaries.

Results

We found that, by itself, pyknotic nuclei quantification resulted in high numbers of false positives (improperly categorized as atretic) and false negatives (improperly categorized intact). For preantral follicles, scoring mitotic and pyknotic GC nuclei allowed rapid, accurate identification of non-growing follicles with 98% accuracy. This method most often required the evaluation of one follicle section, and at most two serial follicle sections to correctly categorize follicle status. For antral follicles, we show that a rapid evaluation of follicle shape reveals which are intact and likely to survive to ovulation.

Conclusions

Combined, these improved, non-arbitrary methods will greatly improve our ability to estimate the fractions of growing/intact and non-growing/atretic follicles in mouse ovaries.

Promotion of glucose utilization by insulin enhances granulosa cell proliferation and developmental competence of porcine oocyte grown in vitro

In vitro culture of the oocyte granulosa cell complexes (OGCs) from early antral follicles (EAFs) shows granulosa cell (GC) proliferation, but to a lesser extent than that observed in vivo during follicle development. As the number of GCs closely relates to energy sufficiency of the oocytes, enhancement of GC proliferation influences oocyte development. GC proliferation depends on glycolysis and insulin-mediated AKT/mTOR signaling pathway; therefore, addition of culture medium containing insulin and glucose may potentially promote GC proliferation and hence improve oocyte development. In the present study, we assessed the effect of exogenous insulin and glucose concentration on GC proliferation and oocyte energy status as well as developmental abilities of porcine oocytes grown in vitro. In the presence of 5.5 mM of glucose (Low), a comparison of 10 versus 20 μg/ml insulin showed that high insulin enhanced GC proliferation but exhausted glucose from the medium, which resulted in low energy status including lipid and adenosine triphosphate of the oocyte. Whereas, in the presence of 20 μg/ml insulin, medium with 11 mM glucose (High) enhanced GC proliferation and oocyte energy status as well as developmental ability up to the blastocyst stage. Considering that there was no difference in OGCs development observed with medium (10 μg/ml insulin) containing 5.5 versus 11 mM glucose, we concluded that the combination of high insulin and glucose enhanced GC proliferation and energy status of oocytes as well as the developmental ability of the oocytes grown in vitro.

Herbal formula menoprogen alters insulin-like growth factor-1 and insulin-like growth factor binding protein-1 levels in the serum and ovaries of an aged female rat model of menopause

OBJECTIVE

Menoprogen (MPG), a traditional Chinese medicine formula for menopause, improves menopausal symptoms; however, its mechanism remains unknown. Previous studies have shown that MPG is not directly estrogenic; thus, the goal of this study was to investigate the effects of MPG on insulin-like growth factor-1 (IGF-1) and insulin-like growth factor binding protein-1 (IGFBP-1) levels in an aged female rat model of menopause.

METHODS

In a six-arm study, 14-month-old female Sprague-Dawley rats (n = 8 per arm) were randomly divided into the following groups: untreated aged, 17β-estradiol-treated aged (estradiol [E2]), and three arms with increasing doses of MPG (162, 324, or 648 mg/kg/d). The sixth arm contained 4-month-old female Sprague-Dawley rats as a normal comparison group. Four weeks after MPG or E2 administration, animals were killed after blood draws, and ovarian tissues were excised. Levels of E2 and progesterone (P4) were determined by radioimmunoassay. Serum and ovarian tissue levels of IGF-1, IGFBP-1, and IGF-1 receptor were determined by enzyme-linked immunosorbent assay.

RESULTS

Compared with the normal group, aged rats had significantly reduced serum levels of E2, P4, and IGF-1, and increased serum and ovarian tissue levels of IGFBP-1. MPG restored serum IGF-1 and IGFBP-1 levels and down-regulated ovarian levels of IGFBP-1, which were closely related to increases in E2 and P4 levels in aged rats. No significant differences in either IGF-1 or IGFBP-1 were observed between the three doses of MPG.

CONCLUSIONS

MPG exerts a direct in vivo effect on aged female rats by positively regulating serum and ovarian IGF-1 and IGFBP-1 levels.

The proteolytic activity of pregnancy-associated plasma protein-A is potentially regulated by stanniocalcin-1 and -2 during human ovarian follicle development

STUDY QUESTION

Is the proteolytic activity of pregnancy-associated plasma protein-A (PAPP-A) regulated by the stanniocalcins (STC1 and STC2) during human follicle maturation?

SUMMARY ANSWER

The STCs and PAPP-A show similar expression by immunohistochemistry in developing follicles, and regulation of PAPP-A proteolytic activity is suggested by the identification of inhibited protein complexes between PAPP-A and STC1 or STC2 in human follicular fluid (FF).

WHAT IS KNOWN ALREADY

The insulin-like growth factor (IGF)-regulating proteinase PAPP-A is secreted by the granulosa cells of estrogen-dominant follicles and is involved in follicle growth. STC1 and STC2 have recently been identified as novel PAPP-A inhibitors, and their expression in non-human mammalian ovaries has previously been observed.

STUDY DESIGN, SIZE, DURATION

The proteolytic activity of PAPP-A in human follicular fluid was assessed, and the interaction between PAPP-A and the STCs in human ovarian tissues and follicular fluid was analyzed using immunoassays. From 21 women, matched pairs of follicular fluid were obtained from one follicle just prior to final maturation of follicles with human chorionic gonadotrophin (hCG), and from another follicle in connection with oocyte aspiration after hCG treatment. Ovarian tissues were obtained from women having one ovary removed for fertility preservation by cryopreservation prior to gonadotoxic treatment.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The concentration and activity of PAPP-A were determined in all samples of follicular fluid. Furthermore, to investigate PAPP-A regulation during follicle development, immunohistochemical staining of PAPP-A, STC1, and STC2 was performed on pre-antral and antral human follicles. To attempt the demonstration of native complexes between PAPP-A and the STCs, immunoprecipitation from a pool of human follicular fluid was performed.

MAIN RESULTS AND THE ROLE OF CHANCE

The concentration of PAPP-A antigen in follicular fluid increased upon stimulation of ovulation with hCG (P < 0.02), but at the same time, PAPP-A activity was decreased. PAPP-A, STC1, and STC2 were localized together in primordial, late primary, and antral follicles, indicating that complex formation is possible in ovarian tissue. Covalent PAPP-A:STC2 and non-covalent PAPP-A:STC1 complexes were immunoprecipitated from follicular fluid, documenting for the first time native inhibited complexes between PAPP-A and the STCs.

LIMITATIONS, REASONS FOR CAUTION

We have demonstrated the presence of native complexes between PAPP-A and the STCs in the human ovary, indicating STC-mediated PAPP-A proteolytic inhibition. Further investigation is required to extend this principle to other tissues.

WIDER IMPLICATIONS OF THE FINDINGS

Our data suggest that the STCs contribute to PAPP-A regulation during folliculogenesis and support a general model in which STC1 and STC2 are regulators of mammalian IGF activity through inhibition of PAPP-A. We suggest that future functional studies take both PAPP-A and the STCs into consideration.

STUDY FUNDING/COMPETING INTERESTS

This work was supported by grants from the Novo Nordisk Foundation, and the Danish Council for Independent Research. No competing interests declared.

Regimen of ovarian stimulation affects oocyte and therefore embryo quality

Without any doubt the regimen used to mature multiple capable oocytes for IVF impacts IVF outcomes. Studies have indicated that the inclusion of LH activity, adjuvant agents such as growth hormone (GH), and regimens providing for simultaneous action of both LH and FSH during final oocyte maturation may have beneficial effects on IVF outcomes. Because of the difficulty in improving IVF outcomes in poor responders, the studies on GH are of particular interest. As pointed out in this review, the apparent beneficial effects of GH on oocyte competence may also apply to older women or to normal responders with reduced embryo quality. A much more difficult question is whether and how much ovarian stimulation impacts on oocyte competence. Paradoxically it seems that there are not demonstrated differences between the stimulated and the natural unstimulated cycle, whereas studies in laboratory animals and IVF patients have shown deleterious effects of higher compared with lower doses of gonadotropins. Recent studies suggest that the use of high doses of gonadotropins as an independent factor correlates negatively with the probability of live birth, whereas a high ovarian response per se is associated with better cumulative pregnancy rates, owing to the availability of more euploid and good-quality embryos. Although adjunctive use of androgens has not been discussed here, it is briefly covered in the first review of this series.

Soy isoflavones administered to rats from weaning until sexual maturity affect ovarian follicle development by inducing apoptosis

Twenty-one-day-old female Wistar rats were treated daily with orally administered soy isoflavones (SIFs) at concentrations of 50, 100, or 200 mg/kg body weight from weaning until sexual maturity (3 mo.), and ovarian follicle development was evaluated. At the end of the treatment period, the ultrastructure of the ovarian granulosa cells was examined by transmission electron microscopy. The apoptotic cell death of ovarian granulosa cells was detected using TUNEL staining. The mRNA expression levels of caspase-3, caspase-8, caspase-9, Bcl2, Bax, and Fas were determined by real-time quantitative PCR. The protein expression levels of caspase-3, Bcl2, Bax, and Fas were determined by western blotting. Our data showed that exposure to SIFs resulted in morphological changes consistent with ovarian granulosa cell apoptosis. The percentage of TUNEL-positive granulosa cells was increased. The mRNA expression levels of the apoptosis-related genes caspase-3, caspase-8, caspase-9, Bax, and Fas increased significantly. The protein levels of Bax, Fas, and cleaved caspase-3 were also increased. These results indicate that the exposure of rats to modest doses of SIFs from weaning until sexual maturity can affect ovarian follicle development by inducing apoptosis. The mechanism of SIF-induced alterations in ovarian follicle development may involve the activation of Fas-mediated and Bcl2/Bax-mediated apoptotic signaling pathways.

IGF-1 gene expression is differentially regulated by estrogen receptors α and β in mouse endometrial stromal cells and ovarian granulosa cells

Insulin-like growth factor 1 (IGF-1) is involved in regulations of reproductive functions in rats and mice. IGF-1 expression is regulated by estrogen in several reproductive organs including the uterus and ovary. Two types of estrogen receptor (ERα and ERβ) are expressed in mouse uteri and ovaries, and it is unclear whether they differently mediate IGF-1 gene transcription. To clarify the roles of ERα and ERβ, mouse endometrial stromal cells and ovarian granulosa cells were treated with ligands specific for individual estrogen receptors. In endometrial stromal cells, propyl-pyrazole-triol (PPT; ERα-selective agonist) increased Igf1 mRNA expression, which was suppressed by methyl-piperidino-pyrazole (MPP, ERα-selective antagonist), while diarylpropionitrile (DPN, ERβ-potency selective agonist) increased Igf1 mRNA expression, which was inhibited by MPP but not by 4-[2-phenyl-5,7-bis(trifluoromethyl)pyrazolo[1,5-α]pyrimidin-3-yl]phenol (PHTPP; ERβ antagonist). PHTPP enhanced the DPN-induced increase in Igf1 mRNA expression. In ovarian granulosa cells, E2 and DPN decreased Igf1 mRNA expression, whereas PPT did not affect Igf1 mRNA levels. In these cells, PHTPP inhibited the DPN-induced decrease in Igf1 mRNA expression. These results suggest that ERα facilitates Igf1 transcription, whereas ERβ appears to inhibit Igf1 gene transcription in mouse endometrial stromal cells and ovarian granulosa cells.

Incorporation of genetic technologies associated with applied reproductive technologies to enhance world food production

Animal breeding and reproductive physiology have been closely related throughout the history of animal production science. Artificial insemination provides the best method of increasing the influence of sires with superior genetics to improve production traits. Multiple ovulation embryo transfer (MOET) provides some ability to increase the genetic influence of the maternal line as well. The addition of genetic technologies to this paradigm allows for improved methods of selecting sires and dams carrying the best genes for production and yield of edible products and resistance to diseases and parasites. However, decreasing the number of influential parents within a population also increases the risk of propagating a recessive gene that could negatively impact the species (Reprod Domest Anim 44:792-796, 2009; BMC Genomics 11:337, 2010). Furthermore, antagonistic genotypic relationships between production traits and fertility (Anim Prod Sci 49:399-412, 2009; Anim Genet 43:442-446, 2012) suggest that care must be taken to ensure that increasing the frequency of genes with a positive influence on production does not negatively impact the fertility of the replacement females entering the herd.

Mice producing reduced levels of insulin-like growth factor type 1 display an increase in maximum, but not mean, life span

Reduced signaling through the IGF type 1 (IGF-1) receptor increases life span in multiple invertebrate organisms. Studies on mammalian longevity suggest that reducing levels of IGF-1 may also increase life span. However, the data are conflicting and complicated by the physiology of the mammalian neuroendocrine system. We have performed life-span analysis on mice homozygous for an insertion in the Igf1 gene. These mice produce reduced levels of IGF-1 and display a phenotype consistent with a significant decrease in IGF-1. Life-span analysis was carried out at three independent locations. Although the life-span data varied between sites, the maximum life span of the IGF-1-deficient mice was significantly increased and age-specific mortality rates were reduced in the IGF-1-deficient mice; however, mean life span did not differ except at one site, where mean life span was increased in female IGF-1-deficient animals. Early life mortality was noted in one cohort of IGF-1-deficient mice. The results are consistent with a significant role for IGF-1 in the modulation of life span but contrast with the published life-span data for the hypopituitary Ames and Snell dwarf mice and growth hormone receptor null mice, indicating that a reduction in IGF-1 alone is insufficient to increase both mean and maximal life span in mice.

Follicle growth, ovulation, and luteal formation in primates and rodents: A comparative perspective

Ovarian function has a great deal of functional overlap between species; antral follicles grow in response to FSH, ovulation involves proteolysis, and the steroidogenic pathway is largely the same. However, embedded in these similarities are important differences that reflect the evolutionary and natural history of species and may focus future research into these critical areas. This review compares ovarian function of rats and mice with primates, focusing on estradiol and follicle growth, steroidogenesis and rupture during the periovulatory interval, and the formation of a functional corpus luteum, drawing the conclusion that careful comparison of species yields more functional information about both than studying them in isolation.

Ghrelin and obestatin expression in serous ovarian tumours

OBJECTIVE

To investigate ghrelin and obestatin expression in serous ovarian tumours.

MATERIALS AND METHODS

Preparations of deparaffinized blocks obtained from the pathology archives of a total of 47 previously diagnosed cases of benign serous tumour (n = 20), borderline serous tumour (n = 7) and malignant serous tumour (n = 20) were subjected to immunohistochemical examination to find out ghrelin and obestatin expressions.

RESULTS

Mean ghrelin expressions decreased significantly in the benign group, relative to the malignant group (p < 0.05), while there was no significant change in mean obestatin expression. It was established that rates of preparations with moderate and severe ghrelin and obestatin expression displayed a significant increase from benign to malignant ones (p < 0.05).

CONCLUSION

The fact that rates of preparations with severe expression correlated with an increase in malignancy suggests that ghrelin and obestatin may be effective in the malignant transformation in at least some cases.

Follicular growth and atresia in mammalian ovaries: regulation by survival and death of granulosa cells

The mammalian ovary is an extremely dynamic organ in which a large majority of follicles are effectively eliminated throughout their reproductive life. Due to the numerous efforts of researchers, mechanisms regulating follicular growth and atresia in mammalian ovaries have been clarified, not only their systemic regulation by hormones (gonadotropins) but also their intraovarian regulation by gonadal steroids, growth factors, cytokines and intracellular proteins. Granulosa cells in particular have been demonstrated to play a major role in deciding the fate of follicles, serving molecules that are essential for follicular growth and maintenance as well as killing themselves by an apoptotic process that results in follicular atresia. In this review, we discuss the factors that govern follicular growth and atresia, with a special focus on their regulation by granulosa cells. First, ovarian folliculogenesis in adult life is outlined. Then, we explain about the regulation of follicular growth and atresia by granulosa cells, in which hormones, growth factors and cytokines, death ligand-receptor system and B cell lymphoma/leukemia 2 (BCL2) family members (mitochondria-mediated apoptosis) are further discussed.

The impact of obesity on egg quality

Obesity in women is a concern in many countries. This causes numerous health issues; however, this review focuses on the impact of obesity on women's reproduction, and in particular the oocyte. Data from infertility clinics and experimental animal models that address the effects of obesity are presented. Bidirectional communication and metabolic support from the surrounding cumulus cells are critical for oocyte development, and the impact of obesity on these cells is also addressed. Both oocyte maturation and metabolism are impaired due to obesity, negatively impacting further development. In addition to reproductive hormones, obesity induced elevations in insulin, glucose, or free fatty acids, and changes in adipokines appear to impact the developmental competence of the oocyte. The data indicate that any one of these hormones or metabolites can impair oocyte developmental competence in vivo, and the combination of all of these factors and their interactions are the subject of ongoing investigations.

Elevated levels of insulin-like growth factor (IGF)-I in serum rescue the severe growth retardation of IGF-I null mice

IGF-I plays a vital role in growth and development and acts in an endocrine and an autocrine/paracrine fashion. The purpose of the current study was to clarify whether elevated levels of IGF-I in serum can rescue the severe growth retardation and organ development and function of igf-I null mice. To address that, we overexpressed a rat igf-I transgene specifically in the liver of igf-I null mice. We found that in the total absence of tissue IGF-I, elevated levels of IGF-I in serum can support normal body size at puberty and after puberty but are insufficient to fully support the female reproductive system (evident by irregular estrous cycle, impaired development of ovarian corpus luteum, reduced number of uterine glands and endometrial hypoplasia, all leading to decreased number of pregnancies and litter size). We conclude that most autocrine/paracrine actions of IGF-I that determine organ growth and function can be compensated by elevated levels of endocrine IGF-I. However, in mice, full compensatory responses are evident later in development, suggesting that autocrine/paracrine IGF-I is critical for neonatal development. Furthermore, we show that tissue IGF-I is necessary for the development of the female reproductive system and cannot be compensated by elevated levels of serum IGF-I.

The role of IGF1 in the in vivo production of bovine embryos from superovulated donors

IGF1 plays an important role in bovine follicular growth, acquisition of oocyte competence and embryo viability. Current data also indicate a critical role for IGF1 in both the ovarian response and the embryo yield following the superovulatory treatments. IGF1 can have either positive or negative effects on embryo viability which is related to the concentration of IGF1 induced by superovulation treatment. These effects impact either on oocyte competence or directly on the embryo. Concentrations in the physiological range appear to result in the production of higher quality embryos, mainly due to the mitogenic and the anti-apoptotic activities of IGF1. However, high superovulatory responses are associated with decreased embryo viability and a concomitant increase in apoptosis. Studies in mice suggest that this increase in apoptosis is related to the downregulation of the IGF1 receptor in the embryo associated with high IGF1 concentrations. Strategies capable of controlling the IGF1 concentrations could be one approach to improve superovulation responses. A range of possible approaches for research within the IGF system in gonadotrophin-stimulated cattle is discussed in this review, including the possible use of superovulated female cattle as an alternative animal experimental model for research on reproductive disorders in humans associated with abnormal IGF1 concentrations.

The role of endocrine insulin-like growth factor-I (IGF-I) in female bovine reproduction

Insulin-like growth factor-I (IGF-I) plays a pivotal role in cattle fertility, acting as a monitoring signal that allows reproductive events to occur when nutritional conditions for successful reproduction are reached. However, endocrine IGF-I is not a predictor of reproductive events, but rather an indirect estimator of the suitability of the animal to achieve the reproductive event in question. Although measuring circulating IGF-I concentrations might not have any clinical application in the cattle industry, endocrine IGF-I screening will continue to be important for the study of interactions between nutrition and reproduction. In addition, endocrine IGF-I screening could be used as an ancillary test for the selection of cattle for high reproductive potential, especially in herds of high genetic merit for milk production, in which a decline in fertility has been identified.

Differentiation of the bovine dominant follicle from the cohort upregulates mRNA expression for new tissue development genes

This study was designed to identify genes that regulate the transition from FSH- to LH-dependent development in the bovine dominant follicle (DF). Serial analysis of gene expression (SAGE) was used to compare the transcriptome of granulosa cells isolated from the most oestrogenic growing cohort follicle (COH), the newly selected DF and its largest subordinate follicle (SF) which is destined for atresia. Follicle diameter, follicular fluid oestradiol (E) and E:progesterone ratio confirmed follicle identity. Results show that there are 93 transcript species differentially expressed in DF granulosa cells, but only 8 of these encode proteins known to be involved in DF development. Most characterised transcripts upregulated in the DF are from tissue development genes that regulate cell differentiation, proliferation, apoptosis, signalling and tissue remodelling. Semiquantitative real-time PCR analysis confirmed seven genes with upregulated (P≤0.05) mRNA expression in DF compared with both COH and SF granulosa cells. Thus, the new genes identified by SAGE and real-time PCR, which show enhanced mRNA expression in the DF, may regulate proliferation (cyclin D2;CCND2), prevention of apoptosis or DNA damage (growth arrest and DNA damage-inducible, β;GADD45B), RNA synthesis (splicing factor, arginine/serine rich 9;SFRS9) and unknown processes associated with enhanced steroidogenesis (ovary-specific acidic protein; DQ004742) in granulosa cells of DF at the onset of LH-dependent development. Further studies are required to show whether the expression of identified genes is dysregulated when abnormalities occur during DF selection or subsequent development.

Genetic removal of Smad3 from inhibin-null mice attenuates tumor progression by uncoupling extracellular mitogenic signals from the cell cycle machinery

Inhibin and activin are members of the TGFbeta family that perform mutually antagonistic signaling roles in the anterior pituitary, gonads, and adrenal gland. Unopposed activin signaling in inhibin-null (Inha-/-) mice causes the formation of granulosa cell tumors in the gonads and adrenal cortex, which depend upon FSH for efficient growth and progression. In this study, we demonstrate that Smad3, a key effector of activin signaling, is expressed at high levels and is constitutively activated in tumors from these mice. Removal of Smad3 from Inha-/- mice by a genetic cross to Smad3-null (Madh3-/-) mice leads to a significant decrease in cyclinD2 expression and a significant attenuation of tumor progression in the gonads and adrenal. The decrease in cyclinD2 levels in compound knockout mice is related to a reduction in mitogenic signaling through the phosphoinositide-3-kinase (PI3-kinase)/Akt pathway, which is required for normal cell cycle progression in tumor cells. Loss of PI3-kinase/Akt signaling cannot be attributed to alterations in IGF expression, suggesting instead that signaling through the FSH receptor is attenuated. Gene expression profiling in the ovaries of Madh3-/- and Inha-/-:Madh3-/- compound knockout mice supports this hypothesis and further suggests that Smad3 is specifically required for FSH to activate PI3-kinase/Akt, but not protein kinase A. Together these observations imply that activin/Smad3 signaling is necessary for efficient signaling by FSH in Inha-/- tumor cells and that interruption of this pathway uncouples FSH from its intracellular mitogenic effectors.

The role of the IGF-I system for vitellogenesis in maturing female sterlet, Acipenser ruthenus Linnaeus, 1758

Transition from previtellogeneic to vitellogenic oocyte growth is a critical phase for folliculogenesis in sturgeon and may often be postponed for several years. Recent findings on the involvement of insulin-like growth factor I (IGF-I) in cell differentiation processes of oocyte follicle and ovarian steroidogenesis of teleosts in vitro led to the hypothesis that paracrine IGF-I could function as a potential trigger in vivo. For the first time, IGF-I and its corresponding receptor (IGF-IR) were identified in a non-teleostean fish. Real-time PCR assays for IGF-I and IGF-IR mRNA were established, normalising mRNA expression of the target genes to beta-microglobulin (beta2m). We clearly show that expression of IGF-I in the gonad is a substantial source for IGF-I-mediated effects in follicles compared to liver, brain, muscle and adipose tissue. Among these tissues, IGF-IR mRNA was highest in the gonad. With regard to different cohorts of coexisting follicles, highest expression of IGF-I and IGF-IR were met in developing follicles, indicating that IGF-I functions as an intraovarian modulator of follicle faith. Comparing previtellogenic follicles in females that matured within two years with non-maturing females f the same age, revealed an increases of 2.3-fold for IGF-I and 2.8-fold for IGF-IR mRNA expression in maturing females. These findings implicate an important role of paracrine IGF-I in early vitellogenesis and identify it as candidate vitellogenesis inducing factor (VIF), determining the faith of the follicle.

Ovarian granulosa cell survival and proliferation requires the gonad-selective TFIID subunit TAF4b

Oocyte development in the mammalian ovary requires productive interactions with somatic granulosa cells of the ovarian follicle. Proliferating granulosa cells support the progression of follicular growth and maturation, multiplying dramatically as it unfolds. The cell cycle recruitment of granulosa cells is regulated at least in part by hormones such as follicle-stimulating hormone (FSH) and estrogen. Follicles recruited into the growth phase following formation of multiple layers of granulosa cells have two major fates: either to continue proliferation followed by differentiation, or to die by programmed cell death, or atresia. While many of the signaling pathways orchestrating ovarian follicle development are known, the downstream transcriptional regulators that integrate such signals in the mammalian ovary remain to be defined. Recent experiments in diverse organisms have revealed multiple instances of gonad-selective components of the basal transcriptional machinery. One such protein, TAF4b, is a gonadal-enriched coactivator subunit of the TFIID complex required for normal female fertility in the mouse. To determine the etiology of female infertility of the TAF4b-deficient mice, we have determined multiple functions of TAF4b during postnatal ovarian follicle development. Here we demonstrate that the TAF4b protein is expressed in the granulosa cell compartment of the mammalian ovarian follicle. Furthermore, TAF4b-deficient mouse ovaries contain reduced numbers of primordial as well as growing follicles and a concomitant increased proportion of apoptotic follicles in comparison to wild type counterparts. Importantly, TAF4b-null follicles are largely resistant to induction of proliferation in response to multiple hormonal stimuli including estrogen and FSH and demonstrate compromised granulosa cell survival. Together, these data suggest that TAF4b integrates a program of granulosa cell gene expression required for normal ovarian follicle survival and proliferation in response to diverse ovarian signaling events.

Somatotropic and gonadotropic axes linkages in infancy, childhood, and the puberty-adult transition

Integrative neuroendocrine control of the gonadotropic and somatotropic axes in childhood, puberty, and young adulthood proceeds via multiple convergent and divergent pathways in the human and experimental animal. Emerging ensemble concepts are required to embody independent, parallel, and interacting mechanisms that subserve physiological adaptations and pathological disruption of reproduction and growth. Significant advances in systems biology will be needed to address these challenges.

Ovarian follicular development in cattle selected for twin ovulations and births12

Comparisons of numbers of antral ovarian follicles and corpora lutea (CL), of blood hormone concentrations, and of follicular fluid steroid concentrations and IGFBP activity were conducted between cows selected (twinner) and unselected (control) for twin births to elucidate genetic differences in the regulation of ovarian follicular development. Ovarian follicular development was synchronized among cows by a single i.m. injection of PGF2alpha on d 18 of the estrous cycle; six cows per population were slaughtered at 0, 24, 48, and 72 h after PGF2alpha. Jugular vein blood was collected from each animal at PGF2alpha injection and at 24-h intervals until slaughter. Ovaries of twinner cows contained more small (< or = 5 mm in diameter, P < 0.05), medium (5.1 to 9.9 mm, P < 0.05), and large (> or = 10.0 mm, P < 0.01) follicles and more (P < 0.01) CL than ovaries of controls. Follicular fluid concentrations of estradiol, androstenedione, testosterone, and progesterone reflected the stage of follicular development and were similar for twinner and control follicles at the same stage. Earlier initiation of follicular development and/or selection of twin-dominant follicles in some twinner cows resulted in greater concentrations of estradiol in plasma at 0, 24, and 48 h and of estradiol, androstenedione, and testosterone in follicular fluid of large follicles at 0 h after PGF2alpha for twinner vs. control cows (follicular status x time x population, P < 0.01). Binding activities of IGFBP-5 and -4 were absent or reduced (P < 0.01) in follicular fluid of developing medium and large estro-gen-active (estradiol:progesterone ratio > 1) follicles but increased with atresia. Only preovulatory Graafian follicles lacked IGFBP-2 binding, suggesting a possible role for IGFBP-2 in selection of the dominant follicle. Concentrations of IGF-I were twofold greater (P < 0.01), but GH (P = 0.10) and cholesterol (P < 0.05) were less in blood of twinners. Three generations of selection of cattle for twin ovulations and births enhanced ovarian follicular development as manifested by increased numbers of follicles within a follicular wave and subsequent selection of twin dominant follicles. Because gonadotropin secretion and ovarian steroidogenesis were similar for control and twinner cattle, enhanced follicular development in twinners may result from decreased inhibition by the dominant follicle(s), increased ovarian sensitivity to gonadotropins, and/or increased intragonadal stimulation, possibly by increased IGF-I.

Insulin-like growth factor binding protein 4 expression parallels luteinizing hormone receptor expression and follicular luteinization in the primate ovary

It has been suggested that locally produced insulin-like growth factor binding protein 4 (IGFBP4) inhibits ovarian follicular growth and ovulation by interfering with IGF action. According to this hypothesis, IGFBP4-expressing follicles should demonstrate atresia, whereas healthy dominant follicles should be devoid of IGFBP4. Alternatively, according to this view, there could be constitutive expression of the inhibitory IGFBP4 but selective expression of an IGFBP4 protease in dominant follicles, allowing the follicle to mature and ovulate because of degradation of the binding protein. To examine these views concerning the role of IGFBP4 in primate follicular selection, we analyzed cellular patterns of IGFs 1 and 2, IGFBP4, and the IGFBP4 protease (pregnancy-associated plasma protein A [PAPP-A]) mRNA expression in ovaries from late follicular phase rhesus monkeys using in situ hybridization. The IGF1 mRNA was not detected, but the IGF2 mRNA was abundant in theca interna and externa of all antral follicles and was present in the granulosa of large preovulatory and ovulatory follicles. The IGFBP4 mRNA was selectively expressed by LH receptor (LHR) mRNA-positive theca interna cells of healthy antral follicles (defined by aromatase and gonadotropin receptor expression) and by LHR-expressing granulosa cells found only in large preovulatory and ovulatory follicles (defined by size and aromatase expression). The PAPP-A mRNA was abundant in granulosa cells of most follicles without obvious relation to IGFBP4 expression. Ovarian IGFBP4 mRNA levels were markedly increased after treatment with the LH analog, hCG, whereas IGF2 and PAPP-A mRNAs were not significantly altered. In summary, IGFBP4 expression appears to be associated with follicular selection, not with atresia, in the monkey ovary. The IGFBP4 is consistently expressed in healthy theca interna and in luteinized granulosa cells, likely under LH regulation. The IGFBP4 protease, PAPP-A, is widely expressed without apparent selectivity for IGFBP4-expressing follicles or for dominant follicles. These observations suggest that IGFBP4 or an IGFBP4 proteolytic product may be involved with LH-induced steroidogenesis and/or luteinization rather than with inhibition of follicular growth.