Cell cycle progression and activation of Akt kinase are required for insulin-like growth factor I-mediated suppression of apoptosis in granulosa cells

AKT, p-AKT, ERK1/2 and p-ERK1/2 in Mural Granulosa Cells Are Not Correlated to Different Ovarian Stimulation Protocols in Patients Undergoing Assisted Reproductive Treatment

(1) Background: In this paper we aim to study the relationship between the expression levels of molecules involved in apoptotic/survival pathways, considered as molecular markers of oocyte competence (i.e., AKT, p-AKT, ERK1/2, and p-ERK1/2) in mural granulosa cells (MGCs) and the administration of r-FSH alone or combined with exogenous r-LH, in ovarian stimulation protocol. Moreover, we aim to evaluate oocyte competence by comparing normally cleaved embryos that were transferred in the uterus, with embryos that were arrested during in vitro culture. (2) Methods: The study included 34 normo-responder women undergoing ICSI procedures. All subjects were divided into two groups. Group A consisted of 18 women stimulated with r-FSH and used as a control group; Group B consisted of 14 women stimulated with r-FSH combined with r-LH. The MGCs were obtained from individual follicles. Immunoblot analyses were carried out to analyze the AKT, p-AKT, ERK1/2, and p-ERK1/2 levels in MGCs and to correlate them with the ovarian stimulation protocol. Furthermore, the oocyte competence was evaluated, for each follicle, according to the development of the embryo during in vitro culture and the pregnancy outcome. (3) Results: We found no significant difference in the levels of molecules in isolated MGCs between groups A and B. These results, in light of our previous research, suggest for the first time, to our knowledge, that cumulus cells and mural granulosa cells in the same follicle show different expression levels of molecules involved in the apoptotic mechanism. (4) Conclusions: Our results could clarify some controversial data in the literature where cumulative cell pools of cumulus and granulosa were analyzed, described as ovarian follicle cells, and used as markers of oocyte competence. In this paper, we found evidence that cumulus and granulosa cells need to be analyzed separately.

Deconvolution at the single-cell level reveals ovarian cell-type-specific transcriptomic changes in PCOS

BACKGROUND

Polycystic ovary syndrome (PCOS) is one of the most common reproductive endocrine disorders in females of childbearing age. Various types of ovarian cells work together to maintain normal reproductive function, whose discordance often takes part in the development and progression of PCOS. Understanding the cellular heterogeneity and compositions of ovarian cells would provide insight into PCOS pathogenesis, but are, however, not well understood. Transcriptomic characterization of cells isolated from PCOS cases have been assessed using bulk RNA-seq but cells isolated contain a mixture of many ovarian cell types.

METHODS

Here we utilized the reference scRNA-seq data from human adult ovaries to deconvolute and estimate cell proportions and dysfunction of ovarian cells in PCOS, by integrating various granulosa cells(GCs) transcriptomic data.

RESULTS

We successfully defined 22 distinct cell clusters of human ovarian cells. Then after transcriptome integration, we obtained a gene expression matrix with 13,904 genes within 30 samples (15 control vs. 15 PCOS). Subsequent deconvolution analysis revealed decreased proportion of small antral GCs and increased proportion of KRT8high mural GCs, HTRA1high cumulus cells in PCOS, especially increased differentiation from small antral GCs to KRT8high mural GCs. For theca cells, the abundance of internal theca cells (TCs) and external TCs was both increased. Less TCF21high stroma cells (SCs) and more STARhigh SCs were observed. The proportions of NK cells and monocytes were decreased, and T cells occupied more in PCOS and communicated stronger with inTCs and exTCs. In the end, we predicted the candidate drugs which could be used to correct the proportion of ovarian cells in patients with PCOS.

CONCLUSIONS

Taken together, this study provides insights into the molecular alterations and cellular compositions in PCOS ovarian tissue. The findings might contribute to our understanding of PCOS pathophysiology and offer resource for PCOS basic research.

High levels of fatty acid-binding protein 5 excessively enhances fatty acid synthesis and proliferation of granulosa cells in polycystic ovary syndrome

BACKGROUND

Polycystic ovary syndrome (PCOS) is one of the most complex endocrine disorders in women of reproductive age. Abnormal proliferation of granulosa cells (GCs) is an important cause of PCOS. This study aimed to explore the role of fatty acid-binding protein 5 (FABP5) in granulosa cell (GC) proliferation in polycystic ovary syndrome (PCOS) patients.

METHODS

The FABP5 gene, which is related to lipid metabolism, was identified through data analysis of the gene expression profiles of GSE138518 from the Gene Expression Omnibus (GEO) database. The expression levels of FABP5 were measured by quantitative real-time PCR (qRT‒PCR) and western blotting. Cell proliferation was evaluated with a cell counting kit-8 (CCK-8) assay. Western blotting was used to assess the expression of the proliferation marker PCNA, and immunofluorescence microscopy was used to detect Ki67 expression. Moreover, lipid droplet formation was detected with Nile red staining, and qRT‒PCR was used to analyze fatty acid storage-related gene expression.

RESULTS

We found that FABP5 was upregulated in ovarian GCs obtained from PCOS patients and PCOS mice. FABP5 knockdown suppressed lipid droplet formation and proliferation in a human granulosa-like tumor cell line (KGN), whereas FABP5 overexpression significantly enhanced lipid droplet formation and KGN cell proliferation. Moreover, we determined that FABP5 knockdown inhibited PI3K-AKT signaling by suppressing AKT phosphorylation and that FABP5 overexpression activated PI3K-AKT signaling by facilitating AKT phosphorylation. Finally, we used the PI3K-AKT signaling pathway inhibitor LY294002 and found that the facilitation of KGN cell proliferation and lipid droplet formation induced by FABP5 overexpression was inhibited. In contrast, the PI3K-AKT signaling pathway agonist SC79 significantly rescued the suppression of KGN cell proliferation and lipid droplet formation caused by FABP5 knockdown.

CONCLUSIONS

FABP5 promotes active fatty acid synthesis and excessive proliferation of GCs by activating PI3K-AKT signaling, suggesting that abnormally high expression of FABP5 in GCs may be a novel biomarker or a research target for PCOS treatment.

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.

Krüppel-like factor 12 regulates aging ovarian granulosa cell apoptosis by repressing SPHK1 transcription and sphingosine-1-phosphate (S1P) production

Oxidative stress triggered by aging, radiation, or inflammation impairs ovarian function by inducing granulosa cell (GC) apoptosis. However, the mechanism inducing GC apoptosis has not been characterized. Here, we found that ovarian GCs from aging patients showed increased oxidative stress, enhanced reactive oxygen species activity, and significantly decreased expression of the known antiapoptotic factor sphingosine-1-phosphate/sphingosine kinase 1 (SPHK1) in GCs. Interestingly, the expression of Krüppel-like factor 12 (KLF12) was significantly increased in the ovarian GCs of aging patients. Furthermore, we determined that KLF12 was significantly upregulated in hydrogen peroxide-treated GCs and a 3-nitropropionic acid-induced in vivo model of ovarian oxidative stress. This phenotype was further confirmed to result from inhibition of SPHK1 by KLF12. Interestingly, when endogenous KLF12 was knocked down, it rescued oxidative stress-induced apoptosis. Meanwhile, supplementation with SPHK1 partially reversed oxidative stress-induced apoptosis. However, this function was lost in SPHK1 with deletion of the binding region to the KLF12 promoter. SPHK1 reversed apoptosis caused by hydrogen peroxide-KLF12 overexpression, a result further confirmed in an in vitro ovarian culture model and an in vivo 3-nitropropionic acid-induced ovarian oxidative stress model. Overall, our study reveals that KLF12 is involved in regulating apoptosis induced by oxidative stress in aging ovarian GCs and that sphingosine-1-phosphate/SPHK1 can rescue GC apoptosis by interacting with KLF12 in negative feedback.

Insulin-like growth factor 1 promotes the gonadal development of Pampus argenteus by regulating energy metabolism†

Insulin-like growth factor 1 (Igf1) is known to promote ovarian maturation by interacting with other hormones. However, the limited research on the role of Igf1 in the energy metabolism supply of gonads has hindered further exploration. To explore the role of Igf1 in gonadal development of silver pomfret, we analyzed the expression levels and the localization of igf1 mRNA and protein during testicular and ovarian development of silver pomfret. The results of the study showed upregulation of Igf1 in the critical period of vitellogenesis and sperm meiosis, which was found to be mainly expressed in the somatic cells of the gonads. Upon adding E2 and Igf1 to cultured gonadal tissues, the expression of energy-related genes was significantly increased, along with the E2-enhanced effect of Igf1 in the testis. Importantly, stimulation of both ovaries and testes with E2 and Igf1 led to a remarkable increase in the expression of vitellogenesis and meiosis-related genes. Therefore, we conclude that Igf1 promotes vitellogenesis and sperm meiosis by regulating gonadal energy production. Moreover, the expression of Igf1 in gonads is significantly regulated by E2. These findings provide new insights for the research of Igf1 in fish breeding, thus allowing the regulation of energy metabolism between growth and reproduction for successful reproductive outcomes.

A Role of PI3K/Akt Signaling in Oocyte Maturation and Early Embryo Development

A serine/threonine-specific protein kinase B (PKB), also known as Akt, is a key factor in the phosphoinositide 3-kinase (PI3K)/Akt signaling pathway that regulates cell survival, metabolism and proliferation. Akt phosphorylates many downstream specific substrates, which subsequently control the nuclear envelope breakdown (NEBD), centrosome maturation, spindle assembly, chromosome segregation, and cytokinesis. In vertebrates, Akt is also an important player during oogenesis and preimplantation development. In the signaling pathways regulating mRNA translation, Akt is involved in the control of mammalian target of rapamycin complex 1 (mTORC1) and thereby regulates the activity of a translational repressor, the eukaryotic initiation factor 4E (eIF4E) binding protein 1 (4E-BP1). In this review, we summarize the functions of Akt in mitosis, meiosis and early embryonic development. Additionally, the role of Akt in the regulation of mRNA translation is addressed with respect to the significance of this process during early development.

Contribution of key elements of nutritional metabolism to the development of cystic ovarian disease in dairy cattle

The alteration of signaling molecules involved in the general metabolism of animals can negatively influence reproduction. In dairy cattle, the development of follicular cysts and the subsequent appearance of ovarian cystic disease (COD) often lead to decreased reproductive efficiency in the herd. The objective of this review is to summarize the contribution of relevant metabolic and nutritional sensors to the development of COD in dairy cows. In particular, we focus on the study of alterations of the insulin signaling pathway, adiponectin, and other sensors and metabolites relevant to ovarian functionality, which may be related to the development of follicular persistence and follicular formation of cysts in dairy cattle. The results of these studies support the hypothesis that systemic factors could alter the local scenario in the follicle, generating an adverse microenvironment for the resumption of ovarian activity and possibly leading to the persistence of follicles and to the development and recurrence of COD.

Kisspeptin regulates the proliferation and apoptosis of ovary granulosa cells in polycystic ovary syndrome by modulating the PI3K/AKT/ERK signalling pathway

BACKGROUND

The development of polycystic ovary syndrome (PCOS) is closely correlated with apoptosis and oxidative stress in ovarian granulosa cells. Kisspeptin plays an important role in reproductive organ function. This study aimed to explore the role of kisspeptin in PCOS and oxidative stress-triggered apoptosis of ovarian granular cells.

METHODS

A PCOS rat model was established by injecting dehydroepiandrosterone (DHEA) and feeding the rats a high-fat diet. The RNA and protein levels of kisspeptin were analysed by quantitative PCR, western blotting, and histological staining. Tissue damage was evaluated using haematoxylin and eosin (H&E) staining. The viability and proliferation of human granulosa cell KGN were measured using the cell counting kit-8 (CCK-8) and 5-ethynyl-2'-deoxyuridine (EdU) assays. Cell cycle and apoptosis were analysed by flow cytometry. Oxidative stress was analysed by measuring reactive oxygen species (ROS), malondialdehyde (MDA), glutathione (GSH), superoxide dismutase (SOD), and catalase (CAT) levels.

RESULTS

Kisspeptin was downregulated in the ovarian granulosa cells of PCOS rats compared to those of control rats. Kisspeptin overexpression enhanced KGN cell proliferation and inhibited apoptosis. ROS generation was suppressed by kisspeptin, along with decreased levels of MDA and increased levels of the antioxidants GSH, SOD, and CAT. Kisspeptin activates PI3K/AKT and ERK signalling, and inactivation of ERK1/2 suppresses the protective role of kisspeptin in ovarian granulosa cells.

CONCLUSION

Kisspeptin improves proliferation and alleviates apoptosis and oxidative stress in ovarian granulosa cells by activating PI3K/AKT and ERK signalling.

Endocrine Disrupting Chemicals in Polycystic Ovary Syndrome: The Relevant Role of the Theca and Granulosa Cells in the Pathogenesis of the Ovarian Dysfunction

Polycystic ovary syndrome (PCOS) is the most common heterogeneous endocrine disorder among women of reproductive age. The pathogenesis of PCOS remains elusive; however, there is evidence suggesting the potential contribution of genetic interactions or predispositions combined with environmental factors. Among these, endocrine disrupting chemicals (EDCs) have been proposed to potentially contribute to the etiology of PCOS. Granulosa and theca cells are known to cooperate to maintain ovarian function, and any disturbance can lead to endocrine disorders, such as PCOS. This article provides a review of the recent knowledge on PCOS pathophysiology, the role of granulosa and theca cells in PCOS pathogenesis, and the evidence linking exposure to EDCs with reproductive disorders such as PCOS.

Insulin resistance, autophagy and apoptosis in patients with polycystic ovary syndrome: Association with PI3K signaling pathway

Polycystic ovary syndrome (PCOS) is a disease in which endocrine metabolic abnormalities coexist with reproductive system abnormalities, with the main clinical manifestations including abnormal menstruation, hirsutism, acne, infertility, and obesity, and it is also a high risk for the development of many pregnancy complications, gynecological malignancies and other diseases. Therefore, timely intervention to prevent the progression of PCOS is of great significance for improving the quality of life of most female patients. Insulin resistance (IR) is one of the most common endocrine disorders in PCOS patients, with approximately 75% of PCOS patients experiencing varying degrees of IR. It is now believed that it is mainly related to the PI3K signaling pathway. The role of autophagy and apoptosis of ovarian granulosa cells (GCs) in the pathogenesis of PCOS has also been gradually verified in recent years. Coincidentally, it also seems to be associated with the PI3K signaling pathway. Our aim is to review these relevant studies, to explore the association between the IR, cellular autophagy and apoptosis in PCOS patients and the PI3K pathway. We summarize some of the drug studies that have improved PCOS as well. We have also found that proteomics holds great promise in exploring the pathogenesis of PCOS, and we have published our views on this.

Stimulatory effects of TGFα in granulosa cells of bovine small antral follicles

Intraovarian growth factors play a vital role in influencing the fate of ovarian follicles. They affect proliferation and apoptosis of granulosa cells (GC) and can influence whether small antral follicles continue their growth or undergo atresia. Transforming growth factor-alpha (TGFα), an oocyte-derived growth factor, is thought to regulate granulosa cell function; yet its investigation has been largely overshadowed by emerging interest in TGF-beta superfamily members, such as bone morphogenetic proteins (BMP) and anti-Mullerian hormone (AMH). Here, effects of TGFα on bovine GC proliferation, intracellular signaling, and cytokine-induced apoptosis were evaluated. Briefly, all small antral follicles (3-5 mm) from slaughterhouse specimens of bovine ovary pairs were aspirated and the cells were plated in T25 flasks containing DMEM/F12 medium, 10% FBS, and antibiotic-antimycotic, and incubated at 37 °C in 5% CO2 for 3 to 4 d. Once confluent, the cells were sub-cultured for experiments (in 96-, 12-, or 6-well plates) in serum-free conditions (DMEM/F12 medium with ITS). Exposure of the bGC to TGFα (10 or 100 ng/mL) for 24 h stimulated cell proliferation compared to control (P < 0.05; n = 7 ovary pairs). Proliferation was accompanied by a concomitant increase in mitogen-activated protein kinase (MAPK) signaling within 2 h of treatment, as evidenced by phosphorylated ERK1/2 expression (P < 0.05, n = 3 ovary pairs). These effects were entirely negated, however, by the MAPK inhibitor, U0126 (10uM, P < 0.05). Additionally, prior exposure of the bGC to TGFα (100 ng/mL) failed to prevent Fas Ligand (100 ng/mL)-induced apoptosis, as measured by caspase 3/7 activity (P < 0.05, n = 7 ovary pairs). Collectively, the results indicate TGFα stimulates proliferation of bGC from small antral follicles via a MAPK/ERK-mediated mechanism, but this action alone fails to prevent apoptosis, suggesting that TGFα may be incapable of promoting their persistence in follicles during the process of follicular selection/dominance.

Inhibition of Nicotinamide adenine dinucleotide phosphate oxidase 4 attenuates cell apoptosis and oxidative stress in a rat model of polycystic ovary syndrome through the activation of Nrf-2/HO-1 signaling pathway

Polycystic ovary syndrome (PCOS) is a common reproductive endocrine disorder in reproductive-aged women. In this study, a rat model of PCOS was established by subcutaneous injection of dehydroepiandrosterone (DHEA). NOX4 was highly expressed in PCOS rat ovaries, while its specific role in PCOS remains unclear. Lentivirus-mediated shRNA targeting NOX4 inhibited oxidative stress by reducing ROS, 4-HNE and MDA levels, and increasing SOD and GPX activities in rat ovaries. NOX4 deficiency increased Bcl-2 levels and decreased Bax, cleaved caspase-3 and cleaved caspase-9 levels and DHEA-induced cell apoptosis in rat ovaries. Similar to the in vivo results, NOX4 silencing inhibited oxidative stress and cell apoptosis in DHEA-treated rat granulosa cells. Moreover, NOX4 silencing promoted Nrf-2 translocation, and the expression of Nrf-2 and HO-1 both in vivo and in vitro. Thus, NOX4 deficiency may ameliorate PCOS in rats by reducing oxidative stress and cell apoptosis via activating the Nrf-2/HO-1 signal pathway.

USP25 Regulates the Proliferation and Apoptosis of Ovarian Granulosa Cells in Polycystic Ovary Syndrome by Modulating the PI3K/AKT Pathway via Deubiquitinating PTEN

Background: Polycystic ovarian syndrome (PCOS) is an endocrine-related disease related to abnormal folliculogenesis and is a leading cause of infertility worldwide. Inhibition of granulosa cells (GCs) proliferation and increased GCs apoptosis have been identified as the major factors in aberrant follicle maturation. Methods: USP25 and PTEN expression in GCs from women with and without PCOS was analyzed using Western blotting. A PCOS-like mouse model was constructed using USP25 knockout and wild-type mice to explore the role of USP25 in PCOS. The human granular cell line KGN was cultured for proliferation and apoptosis assays, and the effect of USP25 on PTEN was investigated after transfection with shRNA-USP25 lentivirus. Results: USP25 expression was found to be elevated in patients and mice with PCOS. With mouse model, we observed a reduction in PCOS symptoms in mice after USP25 deletion. Increased proliferation, reduced apoptosis, activation of the phosphoinositide-3-kinase (PI3K)/protein kinase B (AKT) signaling pathway and decreased PTEN expression were found in KGN cells after USP25 knockdown. Finally, we verified that USP25 could deubiquitinate PTEN in KGN cells. Conclusions: In this study, we investigated that USP25 can regulate the PI3K/AKT signaling pathway by deubiquitinating PTEN, thus affecting the proliferation and apoptosis of GCs and contributing to the pathogenesis of PCOS.

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.

Pseudo-Starvation Driven Energy Expenditure Negatively Affects Ovarian Follicle Development

In the present investigation, we examined whether a change in whole body energy fluxes could affect ovarian follicular development, employing mice ectopically expressing uncoupling protein 1 in skeletal muscle (UCP1-TG). Female UCP1-TG and wild-type (WT) mice were dissected at the age of 12 weeks. Energy intake and expenditure, activity, body weight and length, and body composition were measured. Plasma insulin, glucose, leptin, plasma fibroblast growth factor 21 (FGF21) and plasma insulin-like growth factor 1 (IGF1) levels were analyzed and ovarian follicle and corpus luteum numbers were counted. IGF1 signaling was analyzed by immunohistochemical staining for the activation of insulin receptor substrate 1/2 (IRS1/2) and AKT. UCP1-TG female mice had increased energy expenditure, reduced body size, maintained adiposity, and decreased IGF1 concentrations compared to their WT littermates, while preantral and antral follicle numbers were reduced by 40% and 60%, respectively. Corpora lutea were absent in 40% of the ovaries of UCP1-TG mice. Phospho-IRS1, phospho-AKT -Ser473 and -Thr308 immunostaining was present in the granulosa cells of antral follicles in WT ovaries, but faint to absent in the antral follicles of UCP1-TG mice. In conclusion, the reduction in circulating IGF1 levels due to the ectopic expression of UCP1 is associated with reduced immunostaining of the IRS1-PI3/AKT pathway, which may negatively affect ovarian follicle development and ovulation.

Growth hormone activates PI3K/Akt signaling and inhibits ROS accumulation and apoptosis in granulosa cells of patients with polycystic ovary syndrome

BACKGROUND

It is reported that growth hormone (GH) can alleviate oxidative stress (OS) induced apoptosis in some types of cells by activating the PI3K/Akt signaling pathway. This study investigated the role and underlying mechanism of GH in OS and apoptosis in granulosa cells (GCs) of patients with polycystic ovary syndrome (PCOS).

METHODS

Primary GCs were collected from patients with and without PCOS (controls, n = 32) during oocyte retrieval. The patients with PCOS were randomly assigned to take GH treatment (PCOS-GH, n = 30) or without GH treatment (PCOS-C, n = 31). Reactive oxygen species (ROS) level was determined by spectrophotometry and fluorescence microscopy. GC apoptosis and mitochondrial membrane potential (MMP) were detected by Annexin V-FITC/PI double-staining and JC-1 staining, respectively (flow cytometry). The expression of apoptosis-related genes and proteins involved in PI3K/Akt signaling was determined by quantitative reverse-transcription polymerase chain reaction and western blotting, while active caspase-9 and caspase-3 levels of GCs were determined by enzyme-linked immunosorbent assay.

RESULTS

Our study found that in GCs of the PCOS-GH group, the ROS levels and apoptotic rates were significantly decreased, whereas MMP was significantly increased when compared to those in the PCOS-C group (P < 0.05). The mRNA levels of FOXO1, Bax, caspase-9, and caspase-3 were significantly decreased, whereas Bcl-2 was increased in GCs of the PCOS-GH group than those in the PCOS-C group (P < 0.05). The protein levels of FOXO1, Bax, cleaved caspase-9/caspase-9 and cleaved caspase-3/caspase-3 were decreased, whereas p-PI3K/PI3K, p-Akt/Akt, p-FOXO1 and Bcl-2 were increased in GCs of the PCOS-GH group, compared with those in the PCOS-C group (P < 0.05).

CONCLUSION

OS induced apoptosis and downregulated the PI3K/Akt signaling pathway in patients with PCOS. GH could alleviate apoptosis and activate the PI3K/Akt signaling pathway.

CLINICAL TRIAL REGISTRATION NUMBER

Chinese Clinical Trial Registry. ChiCTR1800019437 . Prospectively registered on October 20, 2018.

STAT4 targets KISS1 to promote the apoptosis of ovarian granulosa cells

Background

In mammals, it is known that the estradiol-17β (E2) is mainly synthetized in ovarian granulosa cells (GCs), and the excessive apoptosis of GCs induces the follicular atresia. Many studies have implicated the essential role of KISS1, with the pro-synthetic effect of E2 and the anti-apoptotic effect on GCs, in the mammalian folliculogenesis, and several STAT4 potential binding sites were previously predicted on the promoter of KISS1 in pigs. However, the biological effects of STAT4 on GCs and the molecular regulation between STAT4 and KISS1 remained largely unknown.

Methods

Using the porcine GCs as the cellular model, the overexpression plasmid, small interfering RNA, 5′-deletion and luciferase assay were applied to investigate the molecular mechanisms for STAT4 regulating the expression of KISS1.

Results

In this study, the STAT4 negatively regulated the mRNA and protein levels of KISS1 in porcine GCs, and the mRNA level of STAT4 was observed to significantly decrease from immature to mature follicles, which was inversed with that of KISS1. The relative luciferase activity of KISS1 promoter was significantly increased with deletion of the fourth potential binding site (− 305/− 295), and ChIP further confirmed that the STAT4 bound at − 305/− 295 region of KISS1. Besides, the STAT4 significantly regulated the mRNA levels of PDK1, FOXO3 and TSC2 of PI3K signaling pathway to promote the cell apoptosis and the percentage of cells at G0/G1 phase of cell cycle in GCs. Alternatively, the STAT4 significantly decreased the mRNA levels of CYP17, 3B-HSD, 17B-33 HSD, ESR1, and ESR2, as well as the concentration of E2 in GCs. Furthermore, interfering with the expression of STAT4 was observed to significantly stimulate the pro-synthetic effect of E2 and anti-apoptotic effect of KISS1 in GCs.

Conclusions

Collectively, the STAT4 might directly target at − 305/− 295 region of KISS1 to negatively regulate the transcription of KISS1, promote the cell apoptosis via PI3K signaling pathway, suppress the synthesis of E2 through the estrogen signaling pathway in porcine GCs. These proposed works could provide useful insight in further investigations on the molecular functionalities of STAT4 and KISS1 in the folliculogenesis of mammals.

Gene analysis of major signaling pathways regulated by gonadotropins in human ovarian granulosa tumor cells (KGN)†

The female reproductive function largely depends on timing and coordination between follicle-stimulating hormone (FSH) and luteinizing hormone. Even though it was suggested that these hormones act on granulosa cells via shared signaling pathways, mainly protein kinases A, B, and C (PKA, PKB, and PKC), there is still very little information available on how these signaling pathways are regulated by each hormone to provide such differences in gene expression throughout folliculogenesis. To obtain a global picture of the principal upstream factors involved in PKA, PKB, and PKC signaling in granulosa cells, human granulosa-like tumor cells (KGN) were treated with FSH or specific activators (forskolin, SC79, and phorbol 12-myristate 13-acetate) for each pathway to analyze gene expression with RNA-seq technology. Normalization and cutoffs (FC 1.5, P ≤ 0.05) revealed 3864 differentially expressed genes between treatments. Analysis of major upstream regulators showed that PKA is a master kinase of early cell differentiation as its activation resulted in the gene expression profile that accompanies granulosa cell differentiation. Our data also revealed that the activation of PKC in granulosa cells is also a strong differentiation signal that could control "advanced" differentiation in granulosa cells and the inflammatory cascade that occurs in the dominant follicle. According to our results, PKB activation provides support for PKA-stimulated gene expression and is also involved in granulosa cell survival throughout follicular development. Taken together, our results provide new information on PKA, PKB, and PKC signaling pathways and their roles in stimulating a follicle at the crossroad between maturation/ovulation and atresia.

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.

Insulin-like growth factor-1 (IGF-1) promotes primordial follicle growth and reduces DNA fragmentation through the phosphatidylinositol 3-kinase/protein kinase B (PI3K/AKT) signalling pathway

We investigated the effects of insulin-like growth factor 1 (IGF-1) on the morphology and follicular activation of ovine preantral follicles cultured in situ and whether the phosphatidylinositol 3-kinase/protein kinase B (PI3K/AKT) pathway is involved in IGF-1 action in the sheep ovary. Ovine ovarian fragments were fixed for histological and terminal deoxynucleotidyl transferase dUTP nick-end labelling (TUNEL) analyses (fresh control) or cultured in supplemented alpha-minimum essential medium (α-MEM+; control) or α-MEM+ with IGF-1 (1, 10, 50, 100 or 200ngmL-1) for 7 days. Follicles were classified as normal or atretic, primordial or growing and the oocyte and follicle diameters were measured. DNA fragmentation was evaluated by TUNEL assay. Proliferating cell nuclear antigen (PCNA) immunohistochemistry was performed on the fresh control, α-MEM+ and 100ngmL-1 IGF-1 samples. Inhibition of PI3K activity was performed through pretreatment with the PI3K inhibitor LY294002 and phosphorylated AKT (pAKT) expression was analysed after culture in the absence or presence of LY294002. IGF-1 at 100ngmL-1 increased (P<0.05) follicular activation compared with α-MEM+ and decreased TUNEL-positive cells (P<0.05) compared with other treatments. PCNA-positive cells also increased (P<0.05) in 100ngmL-1 IGF-1. LY294002 significantly inhibited follicular activation stimulated by α-MEM+ and 100ngmL-1 IGF-1 and reduced pAKT expression in follicles. Overall, IGF-1 at 100ngmL-1 promoted primordial follicle activation, cell proliferation and reduced DNA fragmentation after in situ culture through the PI3K/AKT pathway.

Ochratoxin A Exposure Impairs Porcine Granulosa Cell Growth via the PI3K/AKT Signaling Pathway

The mycotoxin ochratoxin A (OTA), a naturally occurring food contaminant, has a toxic effect on the growth and development of follicles in pigs. However, little is known regarding the specific toxic effects of OTA exposure on oocytes and granulosa cells (GCs). In this study, we cultured porcine ovarian GCs and exposed them to OTA in vitro in order to explore the mechanism causing the negative effects. Initially, it was found that OTA exposure inhibited cell viability in a time and dose dependent manner. We also showed that OTA exposure increased oxidative stress, decreased proliferation ratio, and increased apoptosis ratio in GCs. We revealed an important role for the PI3K/AKT signal pathway in GC proliferation and apoptosis by RNA-seq analysis. The results not only showed that OTA treatment significantly affected the expression of genes within the PI3K/AKT pathway but also demonstrated a concrete relationship between the PI3K/AKT pathway and GC cell proliferation and apoptosis. In conclusion, the results demonstrated that OTA exposure impaired porcine GC growth via the PI3K/AKT signaling pathway.

KISS1 Suppresses Apoptosis and Stimulates the Synthesis of E2 in Porcine Ovarian Granulosa Cells

Previous studies have strongly recommended that KISS-1 metastasis suppressor (KISS1) plays an essential gatekeeper of the initiation of reproductive maturation in mammals. However, KISS1 has been recently reported to highly express in ovarian granulosa cells (GCs). But the biological functionalities of KISS1 on cell apoptosis, cell cycle, and synthesis of estradiol-17β (E2) have not been explored in GCs. In this study, using porcine GCs as a cellular model, the overexpression plasmid of KISS1 was built to explore the biological effects of KISS1 on the PI3K signaling pathway, estrogen signaling pathway, cell apoptosis, cell cycle, and E2 secretion. We found that mRNA of KISS1 highly expressed in the ovary and significantly increased from immature to mature follicles in gilts. Overexpression of KISS1 could significantly increase the mRNA expression of PIK3CG, PIK3C1, and PDK1, and significantly decreased the mRNA levels of FOXO3, TSC2, and BAD of PI3K signaling pathway. Furthermore, results of the flow cytometry showed that overexpression of KISS1 significantly inhibited the apoptosis of GCs and decreased the percentage of GCs at G0/G1 phase of the cell cycle. Additionally, overexpression of KISS1 could increase the mRNA levels of Star, CYP17, 3B-HSD, 17B-HSD of estrogen synthesis signaling pathway, significantly increase the concentration of E2 in the supernatant of the cultured GCs, and up-regulate the mRNA expression levels of ESR1 and ESR2. These results suggested that KISS1 might suppress cell apoptosis through activating the PI3K signaling pathway and stimulate synthesis of E2 via boosting the estrogen synthesis signaling pathway. This study would be of great interests for exploring the biological functionalities of KISS1 in the folliculogenesis and sex steroid production of the ovaries in mammals.

Morphological study of apoptosis in granulosa cells and ovulation in a model of atresia in rat preovulatory follicles

Previous studies have established a model of atresia in preovulatory follicles after stimulation of immature rats with equine chorionic gonadotropin (eCG). This gonadotropin recruits a follicular pool and the deprivation of preovulatory luteinizing hormone (LH) surge induces the atresia in preovulatory follicles. The present study investigated the occurrence of ovulation and provided some morphological features of granulosa cell (GC) apoptosis of atretic follicles at 0, 48, 72 and 120 h after eCG stimulation. Histological sections of ovaries from untreated animals (0 h) showed primordial, primary, secondary and early antral follicles. After 48 h ovaries showed large antral follicles. Preovulatory follicles were observed at 72 h, and two out of five rats displayed cumulus–oocyte complexes (COCs) in the oviducts. All animals exhibited corpora lutea after 120 h. We observed increased estradiol (E2) levels 48 h after eCG treatment that might trigger an endogenous preovulatory gonadotropin surge. Higher progesterone (P4) level, which is the hallmark of a functional corpus luteum, was observed at 120 h. Atresia in secondary and antral follicles was observed by pyknotic granulosa cell nuclei in histology and positive immunolabelling for cleaved caspase 3. We also observed macrophages in secondary and antral follicles in atresia. Transmission electron microscopy revealed GCs with compacted chromatin against the nuclear envelope, nuclear fragmentation, cell shrinkage and fragmentation. No preovulatory follicles showed apoptosis of GCs. In conclusion, our results suggested the occurrence of an endogenous gonadotropin surge, promoting ovulation and preventing atresia of preovulatory follicles.

Genetic deletion of the Angiotensin-(1-7) receptor Mas leads to a reduced ovulatory rate

Angiotensin-(1-7) [Ang-(1-7)] is a component of Renin-Angiotensin System (RAS) that acts through activation of the G-protein-coupled receptor Mas. Recent studies highlight Ang-(1-7) as an intermediate of gonadotropin in ovarian physiology. Genetically Mas-deficient mice allow the investigation of Ang-(1-7) in the ovulatory process. Therefore, the present study aimed to analyze the effects of Mas gene deletion on ovulation to confirm our hypothesis that Mas Knockout (Mas-KO) mice exhibit impairment in the ovulatory outcome. First, we evaluated the breeding data from our animal facilities and from a breeding experiment. The ovulation was observed directly from oviducts after a superovulation protocol and in the estrus morning. We also checked the follicular pool and mRNA expression of Insulin-like growth factor-1 (IGF-1) in ovaries to investigate a possible reason underlying the reduced ovulation. Mas-KO mice showed a reduced litter size and decreased spontaneous ovulatory rate. Ovarian stimulation by gonadotropins reversed ovulation outcome in Mas-KO mice. Mas deficiency also promoted a reduced ovarian follicular pool and lower IGF-1 mRNA levels, suggesting that Mas receptor plays a role in the survival of ovarian follicle. The reduction of ovulatory rate highlights the relevance of Ang-(1-7)/Mas axis in female reproduction, probably through a reduction of IGF-1 mRNA levels.

Temporal regulation of extracellular signal-regulated kinase 1/2 phosphorylation, heat shock protein 70 and activating transcription factor 3 during prostaglandin F-induced luteal regression in pseudopregnant rats following heat stress

The aim of the present study was to investigate the effects of heat stress on heat shock protein (HSP) 70 expression and mitogen-activated protein kinase (MAPK) and protein kinase (PK) B signalling during prostaglandin F (PGF)-induced luteal regression. During pseudopregnancy, rats were exposed to heat stress (HS, 40°C, 2h) for 7 days and treated with PGF or physiological saline on Day 7; serum and ovaries were collected 0, 1, 2, 8 or 24h after PGF treatment. The early inhibitory effect of PGF on progesterone was reduced in HS rats. HSP70 expression in response to PGF was significantly enhanced in HS rats. PGF-induced phosphorylation of extracellular signal-regulated kinase (ERK) 1/2 was significantly greater in the HS group; however, HS rats exhibited elevated basal levels of phosphorylation of p38 MAPK, but not ERK1/2. PGF treatment increased expression of activating transcription factor (ATF) 3 at 2h, which was inhibited by heat stress. Evaluating PKB signalling revealed that phosphorylation of p-Akt (Thr³⁰⁸ and Ser⁴⁷³) was reduced at 8 and 24h after PGF treatment in both non-heat stress (NHS) and HS groups, but there were no significant differences between the HS and NHS groups at any of the time points. In conclusion, the present study provides further evidence that heat stress may enhance HSP70 and affect ERK1/2 and ATF3 expression, but not Akt activation, during PGF-induced luteal regression in pseudopregnant rats.

Luteinizing Hormone Facilitates Antral Follicular Maturation and Survival via Thecal Paracrine Signaling in Cattle

LH supplementation in assisted reproductive technology cycles improves the ongoing pregnancy rate in women with poor ovarian response (POR). However, our knowledge of the precise role of LH during the follicular phase of the menstrual cycle is incomplete. To explore the role of LH in the maturation of small antral follicles, we used an in vitro two-cell system that involved coculturing bovine granulosa cells (GCs) and theca cells (TCs) on a collagen membrane. Treatment of TCs with LH stimulated androgen production in TCs by inducing the expression of androgenic factors, subsequently increasing estrogen biosynthesis in GCs by providing androgen substrates, and inducing aromatase expression. LH stimulation of TCs induced functional LH receptor expression in GCs, a response modulated by the synthesis and action of estrogen. In the presence of TCs, LH stimulation of TCs and FSH stimulation of GCs increased the expression of IGF-1, IGF-2, and IGF-1 receptor in GCs. LH-induced expression of thecal IGF-1 protected GCs from apoptosis and promoted GC survival. Furthermore, LH stimulation of TCs increased FSH sensitivity in GCs. Thus, the LH-TC axis may be involved in the acquisition of LH dependence and the survival of small antral follicles by upregulating androgen/estrogen biosynthesis and activating the IGF system. The use of LH supplementation in ovarian stimulation may increase gonadotropin sensitivity in small antral follicles and promote follicular growth and survival by suppressing GC apoptosis and follicular atresia, resulting in multiple follicular development, even in patients with POR.

Effect of luteinizing hormone on goat theca cell apoptosis and steroidogenesis through activation of the PI3K/AKT pathway

Luteinizing hormone (LH) is a glycoprotein that regulates the function of ovarian follicular cells. Theca cells (TCs) also have a key role in follicular growth and atresia. The effects and intracellular signaling mechanisms were investigated of LH on apoptosis and steroidogenesis in goat gonadotropin-independent follicular (1.0-4.0 mm) TCs. The results indicated that LH increased androstenedione secretion and relative abundance of CYP17A1 and BCL2 mRNA in the TCs, whereas LH in combination with LY294002, a PI3K/AKT inhibitor, decreased LH-induced function. The apoptosis ratio and expression of the BAX gene in TCs were less with LH treatment, and the extent of this inhibition was decreased by suppressing the PI3K/AKT pathway. In conclusion, results of the present study indicate LH regulates apoptosis and steroidogenesis in goat TCs by activating the PI3K/AKT pathway.

Gonadotropin-Dependent Neuregulin-1 Signaling Regulates Female Rat Ovarian Granulosa Cell Survival

Mammalian ovarian follicular development and maturation of an oocyte competent to be fertilized and develop into an embryo depends on tightly regulated, spatiotemporally orchestrated crosstalk among cell death, survival, and differentiation signals through extra- and intraovarian signals, as well as on a permissive ovarian follicular microenvironment. Neuregulin-1 (NRG1) is a member of the epidermal growth factor-like factor family that mediates its effects by binding to a member of the erythroblastoma (ErbB) family. Our experimental results suggest gonadotropins promote differential expression of NRG1 and erbB receptors in granulosa cells (GCs), and NRG1 in theca cells during follicular development, and promote NRG1 secretions in the follicular fluid (FF) of rat ovaries. During the estrous cycle of rat, NRG1 and erbB receptors are differentially expressed in GCs and correlate positively with serum gonadotropins and steroid hormones. Moreover, in vitro experimental studies suggest that the protein kinase C inhibitor staurosporine (STS) causes the physical destruction of GCs by the activation of caspase-3. Exogenous NRG1 treatment of GCs delayed onset of STS-induced apoptosis and inhibited cleaved caspase-3 expressions. Moreover, exogenous NRG1 treatment of GCs alters STS-induced death by maintaining the expression of ErbB2, ErbB3, pAkt, Bcl2, and BclxL proteins. Taken together, these studies demonstrate that NRG1 is gonadotropin dependent, differentially regulated in GCs and theca cells, and secreted in ovarian FF as an intracellular survival factor that may govern follicular maturation.

Alpinia oxyphylla Miq. fruit extract activates IGFR-PI3K/Akt signaling to induce Schwann cell proliferation and sciatic nerve regeneration

BACKGROUND

It is known that the medicinal herb Alpinia oxyphylla Miq. is widely used as a remedy for diarrhea as well as the symptoms accompanying hypertension and cerebrovascular disorders. Moreover, it has also been reported that Alpinia oxyphylla Miq. has beneficial effects on anti-senescence and neuro-protection. This study focuses on the molecular mechanisms by which the Alpinia oxyphylla Miq. fruits promote neuron regeneration.

METHODS

A piece of silicone rubber was guided across a 15 mm gap in the sciatic nerve of a rat. This nerve gap was then filled with various doses of Alpinia oxyphylla Miq. fruits to assess their regenerative effect on damaged nerves. Further, we investigated the role of Alpinia oxyphylla Miq. fruits in RSC96 Schwann cell proliferation.

RESULTS

Our current results showed that treatment with the extract of Alpinia oxyphylla Miq. fruits triggers the phosphorylated insulin-like growth factor-1 receptor- phosphatidylinositol 3-kinase/serine-threonine kinase pathway, and up-regulated the proliferating cell nuclear antigen in a dose-dependent manner. Cell cycle analysis on RSC96 Schwann cells showed that, after exposure to Alpinia oxyphylla Miq. fruit extract, the transition from the first gap phase to the synthesis phase occurs in 12-18 h. The expression of the cell cycle regulatory proteins cyclin D1, cyclin E and cyclin A increased in a dose-dependent manner. Transfection with a small interfering RNA blocked the expression of phosphatidylinositol 3-kinase and induced down-regulation both on the mRNA and protein levels, which resulted in a reduction of the expression of the survival factor B-cell lymphoma 2.

CONCLUSION

We provide positive results that demonstrate that Alpinia oxyphylla Miq. fruits facilitate the survival and proliferation of RSC96 cells via insulin-like growth factor-1 signaling.

Comparative analysis of granulosa cell gene expression in association with oocyte competence in FSH-stimulated Holstein cows

Ovarian stimulation with exogenous FSH followed by FSH withdrawal or ‘coasting’ is an effective means of increasing the number of oocytes obtainable for the in vitro production of cattle embryos. However, the quality of the oocytes thus obtained varies considerably from one cow to the next. The aim of the present study was to gain a better understanding of the follicular conditions associated with low oocyte developmental competence. Granulosa cells from 94 Holstein cows in a commercial embryo production facility were collected following ovarian stimulation and coasting. Microarray analysis showed 120 genes expressed with a differential of at least 1.5 when comparing donors of mostly competent with donors of mostly incompetent oocytes. Using ingenuity pathway analysis, we revealed the main biological functions and potential upstream regulators that distinguish donors of mostly incompetent oocytes. These are involved in cell proliferation, apoptosis, lipid metabolism, retinol availability and insulin signalling. In summary, we demonstrated that differences in follicle maturity at collection could explain differences in oocyte competence associated with individual animals. We also revealed deficiencies in lipid metabolism and retinol signalling in granulosa cells from donors of mostly incompetent oocytes.

Effects of concanavalin A on the progesterone production by bovine steroidogenic luteal cells in vitro

The aim of this study was to evaluate the effects of concanavalin A (CONA) on the progesterone (P4) production by bovine steroidogenic luteal cells (LCs) in vitro. Luteal cells were collected during the mid-luteal stage (at 10-12 days following ovulation) and processed in the laboratory. Luteal cells were grown for 7 days in a humid atmosphere with 5% CO2 , with or without 10% foetal bovine serum, and were subjected to the following treatments: control: no treatment; CONA (10 μg/ml); LH (100 μg/ml); CONA + LH; LH (100 μg/ml) + prostaglandin F2α (PGF2α) (10 ng/ml); CONA + LH + PGF2α. Samples of the culture media were collected on days 1 (D1) and 7 (D7) for P4 quantification. The cells were counted on D7 of culture. Differences between treatments were considered statistically significant at p < .05. Culture in the presence of CONA decreased the P4-secreting capacity of LCs on D7 of culture, particularly in the absence of serum. The cell numbers did not change between treatments.

Apoptotic Cell Localization in Preantral and Antral Follicles in Relation to Non-cyclic and Cyclic Gilts

The objective of this study was to determine apoptotic cell localization in preantral and antral follicles of porcine ovaries. Additionally, the proportion of cells undergoing apoptosis was also compared between delayed puberty gilts and normal cyclic gilts. Ovarian tissues were obtained from 34 culled gilts with age and weight of 270.1 ± 3.9 days and 143.8 ± 2.4 kg, respectively. The gilts were classified according to their ovarian appearance as 'non-cyclic' (n = 7) and 'cyclic' (n = 27) gilts. The terminal deoxynucleotidyl transferase-mediated dUTP nick end labelling (TUNEL) assay was used to determine apoptotic cell expression in different compartments of the ovarian tissue sections. All apparent preantral (n = 110) and antral (n = 262) follicles were evaluated using image analysis software. It was found that apoptotic cells were expressed in both granulosa (22.2%) and theca cell layers (21.3%) of the follicles in the porcine ovaries. The proportion of apoptotic cells in the granulosa layer in the follicles was positively correlated with that in the theca layer (r = 0.90, p < 0.001). Apoptosis did not differ significantly between preantral and antral follicles in either granulosa (27.8% and 26.4%, p > 0.05) or theca cell layers (28.6% and 26.5%, p > 0.05). The proportion of apoptotic cells in non-cyclic gilts was higher than cyclic gilts in both granulosa (31.7% and 22.6%, p < 0.001) and theca cell layers (34.8% and 20.2%, p < 0.001). This study indicated that apoptosis of the granulosa and theca cell layers in the follicles was more pronounced in the ovarian tissue of delayed puberty gilts than cyclic gilts. This implied that apoptosis could be used as a biologic marker for follicular development/function and also that apoptosis was significantly associated with anoestrus or delayed puberty in gilts, commonly observed in tropical climates.

Molecular manipulation of keratin 8/18 intermediate filaments: modulators of FAS-mediated death signaling in human ovarian granulosa tumor cells

Background

Granulosa cell tumors (GCT) are a rare ovarian neoplasm but prognosis is poor following recurrence. Keratin intermediate filaments expressed in these tumors are a diagnostic marker, yet paradoxically, may also constitute a target for therapeutic intervention. In the current study, we evaluated keratin 8/18 (K8/18) filament expression as a mechanism of resistance to apoptosis in GCT, specifically focusing on regulation of the cell surface death receptor, Fas (FAS).

Methods

The GCT cell line, KGN, was transiently transfected with siRNA to KRT8 and KRT18 to reduce K8/18 filament expression. Expression of K8/18, FAS, and apoptotic proteins (PARP, cleaved PARP) were evaluated by fluorescence microscopy, flow cytometric analysis, and immunoblotting, respectively. The incidence of FAS-mediated apoptosis in KGN cells was measured by caspase 3/7 activity. All experiments were performed independently three to six times, using a fresh aliquot of KGN cells for each experiment. Quantitative data were analyzed by one- or two-way analysis of variance (ANOVA), followed by a Tukey’s post-test for multiple comparisons; differences among means were considered statistically significant at P < 0.05.

Results

Control cultures of KGN cells exhibited abundant K8/18 filament expression (~90 % of cells), and minimal expression of FAS (<25 % of cells). These cells were resistant to FAS-activating antibody (FasAb)-induced apoptosis, as determined by detection of cleaved PARP and measurement of caspase 3/7 activity. Conversely, siRNA-mediated knock-down of K8/18 filament expression enhanced FAS expression (> 70 % of cells) and facilitated FasAb-induced apoptosis, evident by increased caspase 3/7 activity (P < 0.05). Additional experiments revealed that inhibition of protein synthesis, but not MEK1/2 or PI3K signaling, also prompted FasAb-induced apoptosis.

Conclusions

The results demonstrated that K8/18 filaments provide resistance to apoptosis in GCT by impairing FAS expression. The abundance of keratin filaments in these cells and their role in apoptotic resistance provides a greater mechanistic understanding of ovarian tumorgenicity, specifically GCT, as well as a clinically-relevant target for potential therapeutic intervention.

Expression pattern of RAGE and IGF-1 in the human fetal ovary and ovarian serous carcinoma

The expression pattern of RAGE and IGF-1 proteins in different ovarian cell lineages was histologically analyzed in six fetal, nine adult human ovaries, and nine serous ovarian carcinomas (OSC) using immunohistochemical methods. Mild expression of IGF-1 in ovarian surface epithelium (Ose) and oocytes in the 15-week human ovaries increased to moderate or strong in the stromal cells, oocytes and follicular cells in week 22. Occasional mild RAGE expression was observed in Ose during week 15, while strong expression characterized primordial follicles in week 22. In the reproductive human ovary, IGF-1 was mildly to moderately expressed in all ovarian cell lineages except in theca cells of the tertiary follicle where IGF-1 was negative. RAGE was strongly positive in the granulosa cells and some theca cells of the tertiary follicle, while negative to mildly positive in all cells of the secondary follicle. In the postmenopausal human ovary IGF-1 and RAGE were mildly expressed in Ose and stroma. In OSC, cells were strongly positive to IGF-1 and RAGE, except for some negative stromal cells. Different levels of IGF-1 and RAGE co-expression characterized fetal ovarian cells during development. In reproductive ovaries, IGF-1 and RAGE were co-localized in the granulosa and theca interna cells of tertiary follicles, while in postmenopausal ovaries and OSC, IGF-1 and RAGE were co-localized in Ose and OSC cells respectively. Our results indicate that intracellular levels of IGF-1 and RAGE protein might regulate the final destiny of the ovarian cell populations prior and during folliculogenesis, possibly controlling the metastatic potential of OSC as well.

Crybb2 deficiency impairs fertility in female mice

Beta-B2-crystallin (CRYBB2), encoded by Crybb2 gene, is a major protein in the mammalian eye lens that plays an important role in maintaining the transparency of the ocular lens. However, CRYBB2 also plays important roles in many extra-lenticular tissues and organs such as the retina, brain and testis. Our previous studies demonstrated that male Crybb2 deficient (Crybb2(-/-)) mice have reduced fertility compared with wild-type (WT) mice, while female Crybb2(-/-) mice exhibited reduced ovary weights and shorter estrous cycle percentages. Here we specifically investigated the role of CRYBB2 in the female reproductive system. Our studies revealed that ovaries from female Crybb2(-/-) mice exhibited significantly reduced numbers of primordial, secondary and pre-ovulatory follicles when compared with WT mice, while the rate of atretic follicles was also increased. Additionally, fewer eggs were collected from the oviduct of Crybb2(-/-) female mice after superovulation. Estrogen levels were higher in the metestrus and diestrus cycles of female Crybb2(-/-) mice, while progesterone levels were lower in diestrus cycles. Furthermore, the expression of survival and cell cycle genes, Bcl-2, Cdk4 and Ccnd2, were significantly decreased in granulosa cells isolated from female Crybb2(-/-) mice, consistent with the predominant expression of CRYBB2 in ovarian granulosa cells. Our results reveal a critical role for CRYBB2 in female fertility and specific effects on the proliferation and survival status of ovarian granulosa cells.

Long-term effects of early-life exposure to environmental oestrogens on ovarian function: role of epigenetics

Oestrogens play an important role in development and function of the brain and reproductive tract. Accordingly, it is considered that developmental exposure to environmental oestrogens can disrupt neural and reproductive tract development, potentially resulting in long-term alterations in neurobehaviour and reproductive function. Many chemicals have been shown to have oestrogenic activity, whereas others affect oestrogen production and turnover, resulting in the disruption of oestrogen signalling pathways. However, these mechanisms and the concentrations required to induce these effects cannot account for the myriad adverse effects of environmental toxicants on oestrogen-sensitive target tissues. Hence, alternative mechanisms are assumed to underlie the adverse effects documented in experimental animal models and thus could be important to human health. In this review, the epigenetic regulation of gene expression is explored as a potential target of environmental toxicants including oestrogenic chemicals. We suggest that toxicant-induced changes in epigenetic signatures are important mechanisms underlying the disruption of ovarian follicular development. In addition, we discuss how exposure to environmental oestrogens during early life can alter gene expression through effects on epigenetic control potentially leading to permanent changes in ovarian physiology.

MDM2-mediated degradation of SIRT6 phosphorylated by AKT1 promotes tumorigenesis and trastuzumab resistance in breast cancer

Sirtuin 6 (SIRT6) is associated with longevity and is also a tumor suppressor. Identification of molecular regulators of SIRT6 might enable its activation therapeutically in cancer patients. In various breast cancer cell lines, we found that SIRT6 was phosphorylated at Ser(338) by the kinase AKT1, which induced the interaction and ubiquitination of SIRT6 by MDM2, targeting SIRT6 for protease-dependent degradation. The survival of breast cancer patients positively correlated with the abundance of SIRT6 and inversely correlated with the phosphorylation of SIRT6 at Ser(338). In a panel of breast tumor biopsies, SIRT6 abundance inversely correlated with the abundance of phosphorylated AKT. Inhibiting AKT or preventing SIRT6 phosphorylation by mutating Ser(338) prevented the degradation of SIRT6 mediated by MDM2, suppressed the proliferation of breast cancer cells in culture, and inhibited the growth of breast tumor xenografts in mice. Overexpressing MDM2 decreased the abundance of SIRT6 in cells, whereas overexpressing an E3 ligase-deficient MDM2 or knocking down endogenous MDM2 increased SIRT6 abundance. Trastuzumab (known as Herceptin) is a drug that targets a specific receptor common in some breast cancers, and knocking down SIRT6 increased the survival of a breast cancer cell exposed to trastuzumab. Overexpression of a nonphosphorylatable SIRT6 mutant increased trastuzumab sensitivity in a resistant breast cancer cell line. Thus, stabilizing SIRT6 may be a clinical strategy for overcoming trastuzumab resistance in breast cancer patients.

Role of the cell cycle in regression of the corpus luteum

The corpus luteum contains differentiated steroidogenic cells that have exited the cell cycle of proliferation. In some tissues, deletion of quiescent, differentiated cells by apoptosis in response to injury or pathology is preceded by reentry into the cell cycle. We tested whether luteal cells reenter the cell cycle during the physiological process of luteolysis. Ovaries were obtained after injection of cows with a luteolytic dose of prostaglandin F(2)(α) (PGF). In luteal sections, cells co-staining for markers of cell proliferation (MKI67) and apoptosis (cPARP1) increased 24  h after PGF, indicating that cells that reenter the cell cycle undergo apoptosis. The percent of steroidogenic cells (CYP11A1-positive) co-staining for MKI67 increased after PGF, while co-staining of non-steroidogenic cells did not change. Dispersed luteal cells were stained with Nile Red to distinguish lipid-rich steroidogenic cells from nonsteroidogenic cells and co-stained for DNA. Flow cytometry showed that the percent of steroidogenic cells progressing through the cell cycle and undergoing apoptosis increased after PGF. Culturing luteal cells induced reentry of steroidogenic cells into the cell cycle, providing a model to test the influence of the cell cycle on susceptibility to apoptosis. Blocking cells early in the cell cycle using inhibitors reduced cell death in response to treatment with the apoptosis-inducing protein, Fas ligand (FASL). Progesterone treatment reduced progression through the cell cycle and decreased FASL-induced apoptosis. In summary, steroidogenic cells reenter the cell cycle upon induction of luteal regression. While quiescent cells are resistant to apoptosis, entry into the cell cycle promotes susceptibility to apoptosis.

cAMP-dependent regulation of ovulatory response genes is amplified by IGF1 due to synergistic effects on Akt phosphorylation and NF-κB transcription factors

Granulosa cells play a crucial role as mediator of the LH-dependent ovulatory response. The intraovarian factor IGF1 is produced by ovarian somatic cells of healthy follicles during the ovulatory response. The objective of this study was to identify mechanisms by which IGF1, alone or in combination with LH, regulates the expression of genes in granulosa cells, which are crucial for ovulation. To achieve this objective, short-term, primary murine granulosa cell cultures were treated for 2-8  h with 1 mM 8-bromoadenosine 3',5'-cAMP to mimic the LH surge and/or 100  ng/ml IGF1. While cAMP induced significant increases in the expression of important ovulatory response genes including amphiregulin (Areg), epiregulin (Ereg), betacellulin (Btc), or interleukin 6 (Il6), IGF1 alone had no effect. However, co-treatment of cells with IGF1 and cAMP had a synergistic effect on Areg, Ereg, Btc, and Il6 mRNA abundance. Pretreatment of granulosa cells with the MEK1/2 inhibitor U0126 demonstrated that cAMP-dependent increases in Areg, Ereg, Btc, and Il6 were mediated by extracellular regulated kinase 1/2 phosphorylation. However, western blot analyses coupled with pretreatment of cells with the PI3K inhibitor LY294002 indicated that the synergistic effect of cAMP and IGF1 on transcript levels was due in part to cooperative increases in Akt phosphorylation. Western blot analyses also demonstrated that IGF1 and the combined treatment of cAMP and IGF1 decreased NF-κB p65 phosphorylation and increased NF-κB p52 levels. Together, these data indicate that IGF1 may amplify cAMP-dependent regulation of ovulatory response gene expression above an important threshold level and therefore represents a novel role for IGF1 during ovulation.

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.

Gene expression profiling of preovulatory follicle in the buffalo cow: effects of increased IGF-I concentration on periovulatory events

The preovulatory follicle in response to gonadotropin surge undergoes dramatic biochemical, and morphological changes orchestrated by expression changes in hundreds of genes. Employing well characterized bovine preovulatory follicle model, granulosa cells (GCs) and follicle wall were collected from the preovulatory follicle before, 1, 10 and 22 h post peak LH surge. Microarray analysis performed on GCs revealed that 450 and 111 genes were differentially expressed at 1 and 22 h post peak LH surge, respectively. For validation, qPCR and immunocytochemistry analyses were carried out for some of the differentially expressed genes. Expression analysis of many of these genes showed distinct expression patterns in GCs and the follicle wall. To study molecular functions and genetic networks, microarray data was analyzed using Ingenuity Pathway Analysis which revealed majority of the differentially expressed genes to cluster within processes like steroidogenesis, cell survival and cell differentiation. In the ovarian follicle, IGF-I is established to be an important regulator of the above mentioned molecular functions. Thus, further experiments were conducted to verify the effects of increased intrafollicular IGF-I levels on the expression of genes associated with the above mentioned processes. For this purpose, buffalo cows were administered with exogenous bGH to transiently increase circulating and intrafollicular concentrations of IGF-I. The results indicated that increased intrafollicular concentrations of IGF-I caused changes in expression of genes associated with steroidogenesis (StAR, SRF) and apoptosis (BCL-2, FKHR, PAWR). These results taken together suggest that onset of gonadotropin surge triggers activation of various biological pathways and that the effects of growth factors and peptides on gonadotropin actions could be examined during preovulatory follicle development.