Targeted suppression of Has2 mRNA in mouse cumulus cell-oocyte complexes by adenovirus-mediated short-hairpin RNA expression

Exploring the Role of Hyaluronic Acid in Reproductive Biology and Beyond: Applications in Assisted Reproduction and Tissue Engineering

Hyaluronic acid (HA) plays a prominent role in various aspects of reproductive biology and assisted reproductive technologies (ART). This review describes the multifaceted influence of HA, ranging from primordial germ cell migration, ovarian follicle development, and ovulation in females to sperm structure, physiology, motility, and capacitation in males. In addition, HA also plays an important role in fertilization and promotes embryo implantation by mediating cellular adhesion and communication within the uterus. Against this physiological background, the review examines the current applications of HA in the context of ART. In addition, the article addresses the emerging field of reproductive tissue engineering, where HA-based hydrogels offer promising perspectives as they can support the development of mature oocytes and spermatogenesis in vitro. Overall, this review highlights the integral role of HA in the intricate mechanisms of reproductive biology and its growing importance for improving ART outcomes and the field of tissue engineering of the reproductive system.

Chrysoeriol Improves the Early Development Potential of Porcine Oocytes by Maintaining Lipid Homeostasis and Improving Mitochondrial Function

Our previous study established that chrysoeriol (CHE) can reduce reactive oxygen species (ROS) accumulation, apoptosis, and autophagy in vitro culture (IVC) of porcine embryos. However, the role of CHE in oocyte maturation and lipid homeostasis is unclear. Herein, we aimed to elucidate the effect of CHE on porcine oocyte competence in vitro maturation (IVM) and subsequent embryo development. The study chooses parthenogenetic activated porcine oocytes as the research model. The study revealed that the cumulus expansion index and related gene expressions are significantly elevated after supplementing 1 μM CHE. Although there were no significant differences in nuclear maturation and cleavage rates, the blastocyst formation rate and total cell numbers were significantly increased in the 1 μM CHE group. In addition, CHE improved the expression of genes related to oocyte and embryo development. ROS was significantly downregulated in all CHE treatment groups, and intracellular GSH (glutathione) was significantly upregulated in 0.01, 0.1, and 1 μM CHE groups. The immunofluorescence results indicated that mitochondrial membrane potential (MMP) and lipid droplet (LD), fatty acid (FA), ATP, and functional mitochondria contents significantly increased with 1 μM CHE compared to the control. Furthermore, CHE increased the expression of genes related to lipid metabolism, mitochondrial biogenesis, and β-oxidation.

Sirtuin 3-mediated deacetylation of superoxide dismutase 2 ameliorates sodium fluoride-induced mitochondrial dysfunction in porcine oocytes

Fluoride exerts detrimental effects on germ cells and increases the infertility rate in women. Nevertheless, the precise mechanisms behind the developmental abnormalities caused by fluoride in oocytes remain poorly comprehended. The current study, we established mitochondrial damage model in oocytes via 50 μg/mL sodium fluoride (NaF) supplementation. We then examined the effects of honokiol in preventing mitochondrial deficits caused by NaF and investigated the mechanisms through which honokiol protects oocytes. The findings investigated that NaF increased levels of mitochondrial reactive oxygen species (mtROS) and hindered mitochondrial function, as evidenced by the dissipation of mitochondrial membrane potential, abnormal expression of mitochondrial DNA copy numbers, and mtDNA harm in oocytes. mtROS scavenging using Mito-TEMPO alleviated oxidative damage in mitochondria and restored the oocyte developmental competence. Superoxide dismutase 2 (SOD2) acetylation was significantly increased, whereas sirtuin 3 (SIRT3) expression was decreased in NaF-treated oocytes. The addition of honokiol helped in the deacetylation of SOD2 at K122 through SIRT3, resulting in the removal of excessive mtROS and the recovery of mitochondrial function. Therefore, SIRT3/SOD2 pathway aids honokiol in mitigating fluoride-induced mitochondrial dysfunction. Overall, honokiol improved the mitochondrial harm caused by NaF by controlling mtROS and mitochondrial function, with the SIRT3/SOD2 pathway having an important function. These findings suggest honokiol as a potential therapeutic strategy for NaF-induced oocyte development and mitochondrial deficits.

Follistatin (FST) is expressed in buffalo (Bubalus bubalis) ovarian follicles and promotes oocyte maturation and early embryonic development

Follistatin (FST), a member of the transforming growth factor-β (TGF-β) superfamily, has been identified as an inhibitor of follicle-stimulating hormone. Previous studies showed that it plays an important role in animal reproduction. Therefore, this study aims to investigate its effect on the maturation of buffalo oocytes in vitro, and the underlying mechanism of FST affecting oocyte maturation was also explored in buffalo cumulus cells. Results showed that FST was enriched in the ovary and expressed at different stages of buffalo ovarian follicles as well as during oocyte maturation and early embryo development. The FST expression level was up-regulated in MII buffalo oocytes compared with the GV stage (p < .05). To study the effects of FST on buffalo oocytes' maturation and early embryonic development, we added the pcD3.1 skeleton vector and PCD3.1-EGFP-FST vector into the maturation fluid of buffalo oocytes, respectively. It was demonstrated that FST promoted the in vitro maturation rate of buffalo oocytes and the blastocyst rate of embryos cultured in vitro (p < .05). By interfering with FST expression, we discovered that FST in cumulus cells plays a crucial role in oocyte maturation. Interference with the FST expression during the buffalo oocyte maturation did not affect the first polar body rate of buffalo oocyte (p > .05). In contrast, the location of mitochondria in oocytes was abnormal, and the cumulus expansion area was reduced (p < .05). After parthenogenetic activation, the cleavage and blastocyst rates of the FST-interfered group were reduced (p < .05). Furthermore, RT-qPCR was performed to investigate further the underlying mechanism by which FST enhances oocyte maturation. We found that overexpression of FST could up-regulate the expression level of apoptosis suppressor gene Bcl-2 and TGF-β/SMAD pathway-related genes TGF-β, SMAD2, and SMAD3 (p < .05). In contrast, the expression levels of SMAD4 and pro-apoptotic gene BAX were significantly decreased (p < .05). The FST gene could affect buffalo oocyte maturation by regulating the oocyte mitochondria integrity, the cumulus expansion, cumulus cell apoptosis, and the expression levels of TGF-β/SMAD pathway-related genes.

The effect of ACVR1B/TGFBR1/ACVR1C signaling inhibition on oocyte and granulosa cell development during in vitro growth culture

The signals of the transforming growth factor β (TGF-β) superfamily play a critical role in follicular development in mammals. ACVR1B/TGFBR1/ACVR1C receptors mediate the signaling of several TGF-β superfamily ligands in granulosa cells. Although the requirement for ACVR1B/TGFBR1/ACVR1C receptor signaling in follicular development has been confirmed using mutant mouse models, the detailed roles of the signaling in granulosa cell and oocyte development have not been clearly defined. In the present study, we examined the requirement for ACVR1B/TGFBR1/ACVR1C receptor signaling in granulosa cells using an in vitro growth culture of oocyte-granulosa cell complexes (OGCs) and SB431542, a potent inhibitor of the receptor signaling. Although cumulus-oocyte complexes isolated from the control OGCs were able to undergo cumulus expansion, those isolated from OGCs grown with the inhibitor were not competent, even in the presence of in vivo-grown oocytes. The diameter of the oocytes in the SB431542-treated OGCs was comparable with that of the control; however, these oocytes were not competent for complete meiotic maturation or preimplantation development. Therefore, ACVR1B/TGFBR1/ACVR1C receptor signaling is not required for oocytes to increase their volume but is essential for the normal development of cumulus cells and oocyte developmental competence.

Bovine in vitro oocyte maturation and embryo culture in liquid marbles 3D culture system

Despite the advances in in vitro embryo production (IVP) over the years, the technique still has limitations that need to be overcome. In cell cultures, it is already well established that three-dimensional culture techniques are more physiological and similar to the in vivo development. Liquid marble (LM) is a three-dimensional system based on the use of a hydrophobic substance to create in vitro microbioreactors. Thus, we hypothesized that the LM system improves bovine in vitro oocyte maturation and embryo culture. In experiment I, bovine cumulus-oocyte complexes (COCs) were placed for in vitro maturation for 22h in two different groups: control (conventional 2D culture) and LM (three-dimensional culture). We found that oocyte nuclear maturation was not altered by the LM system, however it was observed a decrease in expression of genes important in the oocyte maturation process in cumulus cells of LM group (BCL2, EIF4E, and GAPDH). In experiment II, the COCs were conventionally matured and fertilized, and for culture, they were divided into LM or control groups. There was a decrease in blastocyst rate and cell counting, a down-regulation of miR-615 expression, and an increase in the DNA global methylation and hydroxymethylation in embryos of LM group. Therefore, for the bovine in vitro embryo production, this specific three-dimensional system did not present the advantages that we expected, but demonstrated that the embryos changed their development and epigenetics according to the culture system.

Ramelteon Reduces Oxidative Stress by Maintenance of Lipid Homeostasis in Porcine Oocytes

This study aimed to determine the underlying mechanism of ramelteon on the competence of oocyte and subsequent embryo development in pigs during in vitro maturation (IVM). Our results showed that the cumulus expansion index was significantly lower in the control group compared to the ramelteon groups (p < 0.05). Moreover, supplementation of 10−11 and 10−9 M ramelteon significantly increased the cumulus expansion and development-related genes expression, and reduced apoptosis in cumulus cells (p < 0.05). In oocytes, the nuclear maturation rate was significantly improved in 10−11, 10−9, and 10−7 M ramelteon groups compared to the control (p < 0.05). Additionally, the level of intracellular GSH was significantly increased and ROS was significantly decreased in ramelteon-supplemented groups, and the gene expression of oocyte development and apoptosis were significantly up- and down-regulated by 10−11 and 10−9 M ramelteon (p < 0.05), respectively. The immunofluorescence results showed that the protein levels of GDF9, BMP15, SOD1, CDK1, and PGC1α were significantly increased by 10−11 M ramelteon compared to the control (p < 0.05). Although there was no significant difference in cleavage rate, the blastocyst formation rate, total cell numbers, and hatching/-ed rate were significantly improved in 10−11 M ramelteon group compared to the control (p < 0.05). Furthermore, embryo development, hatching, and mitochondrial biogenesis-related genes were dramatically up-regulated by 10−11 M ramelteon (p < 0.05). In addition, the activities of lipogenesis and lipolysis in oocytes were dramatically increased by 10−11 M ramelteon compared to the control (p < 0.05). In conclusion, supplementation of 10−11 M ramelteon during IVM improved the oocyte maturation and subsequent embryo development by reducing oxidative stress and maintenance of lipid homeostasis.

Effect of fibroblast growth factor signaling on cumulus expansion in mice in vitro

The expansion of cumulus cells associated with oocytes is an essential phenomenon in normal mammalian ovulation. Indeed, attenuated expression of cumulus expansion-related genes, including Has2, Ptgs2, Ptx3, and Tnfaip6, results in ovulation failure, leading to female subfertility or infertility. Moreover, emerging evidence suggests that proteins of the fibroblast growth factor (FGF) family, produced within ovarian follicles, regulate the development and function of cumulus cells; however, the effects of FGF signaling on cumulus expansion have not been investigated extensively. Herein, we investigate the effects of FGF signaling, particularly those of FGF8 secreted by oocytes, on epidermal growth factor-induced cumulus expansion in mice. The phosphorylation level of MAPK3/1, an intracellular mediator of FGF signaling, was significantly decreased in cumulus-oocyte complexes (COCs) following treatment with NVP-BGJ398, an FGF receptor inhibitor. Moreover, even though NVP-BGJ398 treatment did not affect cumulus cell expansion, it significantly upregulated the expression of Ptgs2 and Ptx3. In contrast, treatment with recombinant FGF8 did not affect the degree of cumulus expansion or the expression of expansion-related genes in COCs or oocytectomized cumulus cell complexes. Collectively, these results suggest that FGFs, other than FGF8, exert suppressive effects on the cumulus expansion process in mice.

Melatonin Regulates Lipid Metabolism in Porcine Cumulus–Oocyte Complexes via the Melatonin Receptor 2

Previous studies suggest that the inclusion of melatonin (MTn) in in vitro maturation protocols improves the developmental competence of oocytes by scavenging reactive oxygen species (ROS). However, the molecular mechanisms integrating melatonin receptor (MT)-mediated lipid metabolism and redox signaling during in vitro cumulus–oocyte complex (COC) development still remain unclear. Here, we aimed to elucidate the potential role of MTn receptors in lipid metabolic adjustments during in vitro porcine COC development. We observed that MTn-mediated Gsα–cAMP/PKA signaling facilitated lipolysis primarily through the MT2 receptor and subsequently increased fatty acid (FA) release by hydrolyzing intracellular triglycerides (TGs) in cumulus cells. Furthermore, CD36 was a critical FA transporter that transported available FAs from cumulus cells to oocytes and promoted de novo TG synthesis in the latter. In addition, MTn regulated lipogenesis and intracellular lipolysis to maintain lipid homeostasis and limit ROS production, thereby supporting oocyte cytoplasmic maturation and the subsequent embryo development. Taken together, these findings provide insight into the possible mechanism integrating MT2-mediated lipid homeostasis and redox signaling, which limits ROS production during in vitro COC development. Therefore, understanding the dynamics of the interactions between lipid homeostasis and redox signaling driven by MT2 is necessary in order to predict drug targets and the effects of therapeutics used to improve female reproductive health.

Tannin Supplementation Improves Oocyte Cytoplasmic Maturation and Subsequent Embryo Development in Pigs

To investigate the effects of tannins (TA) on porcine oocyte in vitro maturation (IVM), different concentrations of TA (0, 1, 10 and 100 μg/mL) were supplemented with a maturation medium and the COCs and subsequent embryonic development were examined. The results showed that 10 µg/mL TA significantly improved the cumulus expansion index (CEI), cumulus-expansion-related genes (PTGS1, PTGS2, PTX-3, TNFAIP6 and HAS2) expression and blastocyst formation rates after parthenogenetic activation (PA), in vitro fertilization (IVF) and somatic cell nuclear transfer (SCNT) compared to the control groups, but not oocyte nuclear maturation. Nevertheless, 10 µg/mL TA dramatically enhanced the mRNA expression of oocyte-development-related genes (BMP15, GDF9, CDC2 and CYCLIN B1), GSH, ATP, SOD1, PGC1α, BMP15, GDF9 and CDC2 levels and reduced intracellular ROS level in porcine oocytes. These results indicated that porcine oocyte cytoplasmic maturation was improved by 10 µg/mL TA treatment during IVM. In contrast, a high concentration of TA (100 μg/mL) significantly decreased the CEI and PTGS1, PTGS2, PTX-3 and HAS2 mRNA expressions in cumulus cells, and reduced oocyte nuclear maturation and the total cell numbers/blastocyst. In general, these data showed that 10 μg/mL TA supplementation has beneficial effects on oocyte cytoplasmic maturation and subsequent embryonic development in pigs.

The Molecular Regulation in the Pathophysiology in Ovarian Aging

The female reproductive system is of great significance to women’s health. Aging of the female reproductive system occurs approximately 10 years prior to the natural age-associated functional decline of other organ systems. With an increase in life expectancy worldwide, reproductive aging has gradually become a key health issue among women. Therefore, an adequate understanding of the causes and molecular mechanisms of ovarian aging is essential towards the inhibition of age-related diseases and the promotion of health and longevity in women. In general, women begin to experience a decline in ovarian function around the age of 35 years, which is mainly manifested as a decrease in the number of ovarian follicles and the quality of oocytes. Studies have revealed the occurrence of mitochondrial dysfunction, reduced DNA repair, epigenetic changes, and metabolic alterations in the cells within the ovaries as age increases. In the present work, we reviewed the possible factors of aging-induced ovarian insufficiency based on its clinical diagnosis and performed an in-depth investigation of the relevant molecular mechanisms and potential targets to provide novel approaches for the effective improvement of ovarian function in older women.

Expression patterns of ZO-1/2 and their effects on porcine oocyte in vitro maturation and early embryonic development

Zonula occludens (ZO)-1 and ZO-2 are involved in epithelial polarity maintenance, gene transcription, cell proliferation and tumor cell metastasis. Regulating ZO-1/2 expression influences the early embryonic development of mice, but whether they are involved in oocyte maturation is still poorly understood. In the present study, the expression patterns of ZO-1 and ZO-2 in porcine cumulus cells and oocytes matured in vitro and early embryos from parthenogenetic activation were detected by qRT-PCR or Western blot, and then their roles in porcine oocyte maturation and early embryo development were investigated by shRNA technology. ZO-1 and ZO-2 were found to be expressed in cumulus cells, oocytes and early embryos, while ZO-1α⁺ was expressed only in cumulus cells, morula and blastocysts. During in vitro maturation (IVM), the abundance of ZO-1 and ZO-2 in oocytes was significantly higher than that in cumulus cells at 0 h (P < 0.01), and their mRNA and protein levels displayed relatively higher expression at 0 and 18 h, respectively. Compared with the control groups, cumulus cell expansion, oocyte nucleus maturation, and subsequent cleavage were not influenced by treatment of the cumulus-oocyte complexes (COCs) with ZO-1-shRNA1, ZO-2-shRNA2 or combined ZO-1-shRNA1 and ZO-2-shRNA2 lentivirus (P > 0.05). However, the blastocyst rate was reduced by treatment of COCs with ZO-1-shRNA1 but not ZO-2-shRNA2. The total cell number of blastocysts was decreased by downregulation of ZO-1 and ZO-2 (P < 0.05). Downregulation of ZO-1 and ZO-2 also resulted in a significant decrease (P < 0.05) in the expression of Cx43, Cx45, PTX3 and PTGS2 in cumulus cells, Cx45, BMP15, ZP3 and C-KIT in MII oocytes, and Nanog in blastocysts, with the exception of HAS2 expression in cumulus cells and Oct4 expression in blastocysts (P > 0.05). Altogether, the above results indicate that ZO-1 and ZO-2 display similar expression patterns during porcine oocyte IVM and are critical to porcine oocyte maturation and early embryonic development.

Nuclear receptors: Key regulators of somatic cell functions in the ovulatory process

The development of the ovarian follicle to its culmination by ovulation is an essential element of fertility. The final stages of ovarian follicular growth are characterized by granulosa cell proliferation and differentiation, and steroid synthesis under the influence of follicle-stimulating hormone (FSH). The result is a population of granulosa cells poised to respond to the ovulatory surge of luteinizing hormone (LH). Members of the nuclear receptor superfamily of transcription factors play indispensable roles in the regulation of these events. The key regulators of the final stages of follicular growth that precede ovulation from this family include the estrogen receptor beta (ESR2) and the androgen receptor (AR), with additional roles for others, including steroidogenic factor-1 (SF-1) and liver receptor homolog-1 (LRH-1). Following the LH surge, the mural and cumulus granulosa cells undergo rapid changes that result in expansion of the cumulus layer, and a shift in ovarian steroid hormone biosynthesis from estradiol to progesterone production. The nuclear receptor best associated with these events is LRH-1. Inadequate cumulus expansion is also observed in the absence of AR and ESR2, but not the progesterone receptor (PGR). The terminal stages of ovulation are regulated by PGR, which increases the abundance of the proteases that are directly responsible for rupture. It further regulates the prostaglandins and cytokines associated with the inflammatory-like characteristics of ovulation. LRH-1 regulates PGR, and is also a key regulator of steroidogenesis, cellular proliferation, and cellular migration, and cytoskeletal remodeling. In summary, nuclear receptors are among the panoply of transcriptional regulators with roles in ovulation, and several are necessary for normal ovarian function.

Estrogen improves the development of yak (Bos grunniens) oocytes by targeting cumulus expansion and levels of oocyte-secreted factors during in vitro maturation

The estrogen-signalling pathway is critical for normal follicular development; however, little is known about its importance during in vitro maturation (IVM) in large animals, particularly yaks (Bos grunniens). Through the present study, we aimed to determine the mechanisms underlying estrogen involvement in cumulus expansion and the subsequent development of cumulus-oocyte complexes (COCs). COCs were cultured in the maturation medium supplemented with different concentrations (10⁻⁶–10⁻³ mM) of 17β-estradiol (E2) or its receptor antagonist, fulvestrant, and quantitative reverse-transcription polymerase chain reaction (qRT-PCR) and western blot were performed to determine the expression of cumulus-expansion related factors and oocyte-secreted factors (OSFs). The cumulus expansion of COCs was observed using an inverted microscope, and COCs developmental ability were judged by the evaluation of cleavage and blastulation rates per inseminated oocytes by IVF, and the number of cells in the blastocyst. Cumulus expansion increased with 10⁻⁶–10⁻³ mM E2, but decreased with fulvestrant. HAS2, PTGS2, PTX3 and OSFs expression increased in the 10⁻⁶–10⁻³ mM E2 groups. Significantly higher cleavage and blastocyst rates were observed in the 10⁻⁴ mM E2 group than in the fulvestrant and 0 mM E2 groups. Moreover, in the 10⁻⁴ mM group, blastocysts at 7 days had higher cell counts than the other groups. In conclusion, the increase in cumulus expansion and subsequent oocyte development after the addition of E2 to IVM medium may have resulted from increased cumulus-expansion-related factor expression and OSF levels.

Up-regulated FHL2 inhibits ovulation through interacting with androgen receptor and ERK1/2 in polycystic ovary syndrome

BACKGROUND

The ovulatory dysfunction mechanisms underlying polycystic ovary syndrome (PCOS) are not completely understood. There is no effective therapy for PCOS so far.

METHODS

We measured the expression of four and a half LIM domain 2 (FHL2) and other related-genes in human granulosa cells (hGCs) from patients with and without PCOS. To minimise the heterogeneity of patients with PCOS, we only included PCOS patients meeting all three criteria according to the revised Rotterdam consensus. The in vitro effects of FHL2 on ovulatory genes and the underlying mechanisms were examined in KGN cells. The role of FHL2 in ovulation was investigated in vivo by overexpressing FHL2 in rat ovaries via intrabursal lentivirus injection.

FINDINGS

Increased FHL2 and androgen receptor (AR) expression and decreased CCAAT/enhancer-binding protein β (C/EBPβ) expression were observed in hGCs from patients with PCOS. FHL2 inhibited the expression of ovulation-related genes, including phosphorylated ERK1/2, C/EBPβ, COX2 and HAS2 in KGN cells. It was partially by interacting with AR to act as its co-regulator to inhibit C/EBPβ expression and by binding to ERK1/2 to inhibit its phosphorylation. Moreover, FHL2 abundance in hGCs was positively correlated with the basal serum testosterone concentration of patients with PCOS, and dihydrotestosterone (DHT)-induced FHL2 upregulation was mediated by AR signalling in KGN cells. Additionally, lentiviral-mediated functional FHL2 overexpression in rat ovaries for 1 week contributed to an impaired superovulatory response, displaying decreased numbers of retrieved oocytes and a lower MII oocyte rate. 3-week FHL2 overexpression rat models without superovulation led to acyclicity and polycystic ovary morphology.

INTERPRETATION

Our findings provide novel insights into the mechanisms underlying the pathogenesis of PCOS, suggesting that FHL2 could be a potential treatment target for ovulatory obstacles in PCOS. FUND: National Key Research and Development Program of China, National Natural Science Foundation, National Institutes of Health project and Shanghai Commission of Science and Technology.

Brain-derived neurotrophic factor (BDNF) is expressed in buffalo (Bubalus bubalis) ovarian follicles and promotes oocyte maturation and early embryonic development

Brain-derived neurotrophic factor (BDNF) has been discovered and characterized for several decades, yet its expression pattern in non-neuronal tissues like ovary and potential mechanism during oocyte maturation are still poorly understood. Thus the present study was devised to determine the expression pattern and mechanism of BDNF during buffalo oocyte maturation. The results revealed that BDNF was presented at different stages of buffalo ovarian follicles as well as during oocyte maturation and early embryo development. BDNF's receptor p75 was detected in granulosa cells, cumulus cells, oocytes, and early embryos, while another receptor neurotrophic tyrosine kinase receptor, type2 (NTRK2) was only identified in granulosa cells and cumulus cells. To determine the effect of BDNF on oocyte maturation and early embryo development, different concentrations (0, 1, 10, 100 ng/mL) of BDNF were added into the in vitro maturation media, respectively. It was divulged that 10 ng/mL BDNF promoted the in vitro maturation rate of buffalo oocytes and the blastocysts rate of embryos cultured in vitro (P < 0.05). Then through using NTRK2 inhibitor K-252a, we found BDNF and its receptor NTRK2 in cumulus cells played an essential role during oocyte maturation. Moreover, to further investigate the underlying mechanism by which BDNF enhances oocyte maturation, RT-qPCR was performed. 10 ng/mL BDNF treatment could decrease the expression level of apoptosis-related genes CCASP9, FAS, up-regulate the expression level of receptor gene NTRK2, cell proliferation-related genes CCNB1, PCNA, gap junction-related genes GJA4, GJA1 as well as cumulus cells expansion-related genes HAS2, PTX3 and TNFAIP6 (P < 0.05). Altogether, our results showed for the first time that BDNF was expressed throughout buffalo ovarian follicle development, oocyte maturation and early embryogenesis. Furthermore, BDNF treatment could improve the efficiency of buffalo oocyte maturation through regulating genes expression in cumulus cells and then promote early embryo development.

Oocyte-specific ablation of N- and O-glycans alters cumulus cell signalling and extracellular matrix composition

Cumulus-oocyte complex (COC) expansion is essential for ovulation and fertilisation and is linked to oocyte quality. Hyaluronan (HA), the major matrix constituent, is cross-linked via inter-α-inhibitor heavy chains (HCs), pentraxin 3 (PTX3) and tumour necrosis factor-stimulated gene 6 (TSG-6). All except HCs are secreted by cumulus cells in response to oocyte-secreted factors, which signal via SMAD pathways. The double mutant (DM) mouse generates oocytes lacking complex N- and O-glycans due to oocyte-specific deletion of core 1 β1,3-galactosyltransferase (C1galt1) and N-acetylglucosaminyltransferase I (Mgat1) and has modified cumulus expansion. We compared COCs before expansion (48 h-post-pregnant mare serum gonadotrophin (PMSG)) and at late-stage expansion (9 h-post-human chorionic gonadotrophin (hCG); control n=3 mice, DM n=3 per group). Using histochemistry the levels of HA, HCs, PTX3, TSG-6 and phosphorylated-SMAD1/5/8 and -SMAD2 (12-25 COCs per group) were assessed. DM COCs did not differ from Controls in cumulus size or cell density at 9 h-post-hCG; however, HA and HC levels and phosphorylated-SMAD1/5/8 were reduced. Furthermore, no correlations were found between the levels of matrix molecules and cumulus area in DM or Control samples. These data suggest that HA and HCs can support cumulus expansion provided that they are present above minimum threshold levels. We propose that oocyte-specific ablation of C1galt1 and Mgat1 may affect bone morphogenetic protein 15 synthesis or bioactivity, thereby reducing SMAD1/5/8 phosphorylation and HA production.

Induced cumulus expansion of poor quality buffalo cumulus oocyte complexes by Interleukin-1beta improves their developmental ability

The present study was conceived with the aim of modulating the cumulus expansion characteristics of poor quality (BCB-) buffalo oocyte complexes (COCs) in order to improve their fertilization outcomes. BCB- COCs were subjected to in vitro maturation (IVM) in presence of Interleukin-1 beta (IL-1β) along with BCB- (control) and good quality (BCB+) COCs. Results were assessed morphologically, by scanning electron microscopy (SEM) and by expression analysis of cumulus expansion related genes. Also, numbers of zona pellucida bound spermatozoa were counted and development rates of oocytes were monitored under different groups. Expression of versican isoforms and ADAMTS-1 was observed to be significantly different between cumulus cells of BCB+ and BCB- COCs. Upon IL-1β supplementation, ADAMTS-1 expression increased in BCB- COCs along with corresponding cumulus expansion rates. SEM analysis also revealed improved cumulus expansion in IL-1β supplemented BCB- COCs. HAS2 and TNFAIP-6 were significantly up-regulated after IL-1β supplementation while PTGS2 expression remained unaffected. Significantly more numbers of sperms crossed the cumulus barrier, especially in 100 ng/mL IL-1β supplemented COCs. Besides, cleavage and blastocyst development rates were also improved upon IL-1β addition. We concluded that IL-1β supplementation in IVM medium can improve cumulus expansion and development ability of poor quality buffalo oocytes.

Evaluating The Effect of Melatonin on HAS2, and PGR expression, as well as Cumulus Expansion, and Fertility Potential in Mice

OBJECTIVES

Infertility is a worldwide health problem which affects approximately 15% of sexually active couples. One of the factors influencing the fertility is melatonin. Also, protection of oocytes and embryos from oxidative stress inducing chemicals in the culture medium is important. The aim of the present study was to investigate if melatonin could regulate hyaluronan synthase-2 (HAS2) and Progesterone receptor (PGR) expressions in the cumulus cells of mice oocytes and provide an in vitro fertilization (IVF) approach.

MATERIALS AND METHODS

In this experimental study, for this purpose, 30 adult female mice and 15 adult male mice were used. The female mice were superovulated using 10 U of pregnant mare serum gonadotropin (PMSG) and 24 hours later, 10 U of human chorionic gonadotropin (hCG) were injected. Next, cumulus oocyte complexes (COCs) were collected from the oviducts of the female mice by using a matrix-flushing method. The cumulus cells were cultured with melatonin 10 μM for 6 hours and for real-time reverse transcription-polymerase chain reaction (RT-PCR) was used for evaluation of HAS2 and PGR expression levels. The fertilization rate was evaluated through IVF. All the data were analyzed using a t test.

RESULTS

The results of this study showed that HAS2 and PGR expressions in the cumulus cells of the mice receiving melatonin increased in comparison to the control groups. Also, IVF results revealed an enhancement in fertilization rate in the experimental groups compared to the control groups.

CONCLUSIONS

To improve the oocyte quality and provide new approaches for infertility treatment, administration of melatonin as an antioxidant, showed promising results. Thus, it is concluded that fertility outcomes can be improved by melatonin it enhances PGR.

MicroRNA-574 suppresses oocyte maturation via targeting hyaluronan synthase 2 in porcine cumulus cells

MicroRNAs (miRNAs) have been established as important regulators of gene expression in the mammalian ovary. A previous screen of small RNA in the porcine ovary identified the downregulation of miR-574 during oocyte maturation, although its role during this process was not established. Here, we found that miR-574 directly targets the transcript for hyaluronan synthase 2 protein (HAS2), a key enzyme in the production of extracellular matrix by the surrounding cumulus cells. Inhibiting this miRNA during in vitro maturation (IVM) increased HAS2 levels along with several markers of oocyte quality. Furthermore, inhibiting miR-574 increased oocyte meiotic progression. We then stably overexpressed miR-574 using a lentiviral vector to transduce cumulus cells during IVM. This gain-of-function approach resulted in a 50% decrease in HAS2 expression and nearly 20% reduction in oocyte progression through meiosis. To confirm the specific targeting of HAS2 by miR-574, we constructed several luciferase vectors harboring the HAS2 3'-untranslated region. Cotransfection of the reporter and miR-574 attenuated luciferase activity. After mutating the putative miR-574 binding site, however, this effect was abolished and luciferase activity remained high. Our results show that the direct targeting of HAS2 by miR-574 negatively impacts oocyte quality during IVM and that inhibiting miR-574 derepresses HAS2 expression and subsequently improves oocyte maturation. Taken together, we help to elucidate a mechanism of posttranscriptional regulation by miRNA in the mammalian ovary.

Effects of exosome-like vesicles on cumulus expansion in pigs in vitro

Cell-secreted vesicles, such as exosomes, have recently been recognized as mediators of cell communication. A recent study in cattle showed the involvement of exosome-like vesicles in the control of cumulus expansion, a prerequisite process for normal ovulation; however, whether this is the case in other mammalian species is not known. Therefore, this study aimed to examine the presence of exosome-like vesicles in ovarian follicles and their effects on cumulus expansion in vitro in pigs. The presence of exosome-like vesicles in porcine follicular fluid (pFF) was confirmed by transmission electron microscopic observation, the detection of marker proteins, and RNA profiles specific to exosomes. Fluorescently labeled exosome-like vesicles isolated from pFF were incorporated into both cumulus and mural granulosa cells in vitro. Exosome-like vesicles were not capable of inducing cumulus expansion to a degree comparable to that induced by follicle-stimulating hormone (FSH). Moreover, exosome-like vesicles had no significant effects on the expression levels of transcripts required for the normal expansion process (HAS2, TNFAIP6, and PTGS2). Interestingly, FSH-induced expression of HAS2 and TNFAIP6 mRNA, but not of PTGS2 mRNA, was significantly increased by the presence of exosome-like vesicles; however, the degree of FSH-induced expansion was not affected. In addition, porcine exosome-like vesicles had no significant effects on the expansion of mouse cumulus-oocyte complexes. Collectively, the present results suggest that exosome-like vesicles are present in pFF, but they are not efficient in inducing cumulus expansion in pigs.

Oocyte-dependent activation of MTOR in cumulus cells controls the development and survival of cumulus-oocyte complexes

Communication between oocytes and their companion somatic cells promotes the healthy development of ovarian follicles, which is crucial for producing oocytes that can be fertilized and are competent to support embryogenesis. However, how oocyte-derived signaling regulates these essential processes remains largely undefined. Here, we demonstrate that oocyte-derived paracrine factors, particularly GDF9 and GDF9-BMP15 heterodimer, promote the development and survival of cumulus-cell-oocyte complexes (COCs), partly by suppressing the expression of Ddit4l, a negative regulator of MTOR, and enabling the activation of MTOR signaling in cumulus cells. Cumulus cells expressed less Ddit4l mRNA and protein than mural granulosa cells, which is in striking contrast to the expression of phosphorylated RPS6 (a major downstream effector of MTOR). Knockdown of Ddit4l activated MTOR signaling in cumulus cells, whereas inhibition of MTOR in COCs compromised oocyte developmental competence and cumulus cell survival, with the latter likely to be attributable to specific changes in a subset of transcripts in the transcriptome of COCs. Therefore, oocyte suppression of Ddit4l expression allows for MTOR activation in cumulus cells, and this oocyte-dependent activation of MTOR signaling in cumulus cells controls the development and survival of COCs.

Impact of Prunus Cerasus on PGR and HAS2 in Cumulus Cells and Fertility Outcome

PURPOSE

Cumulus cells have a critical role in normal oocyte development and fertilization. Prunus cerasus is an anthocyanin rich berry and performs strong antioxidant activity. The present study set to determine if Prunus cerasus can affect expression of HAS2 (hyaluronan synthase 2) and progesterone receptor in Cumulus cells and its consequences outcome of the in vitro fertilization.

METHODS

60 female and 15 male adult mice were used for mating and IVF (in vitro fertilization). Prunus cerasus extraction was added to the diet of female mice for 30 days. Ovulation induction and oocytes collection were done as routine. The cumulus cells were dissected apart, and the expression of progesterone receptor and HAS2 was detected using RT-PCR (real-time polymerase chain reaction). Fertilization rate was evaluated by IVF. All data were analyzed using t-test.

RESULTS

Data was showed that expression of progesterone receptor and HAS2 in cumulus cells of mice that received prunus cerasus increased. Moreover, oocyte fertilization rate also increased significantly.

CONCLUSION

Prunus cerasus as an antioxidant natural can become an important medication for improving oocyte quality and opening new opportunities for infertility treatment. It is concluded that Prunus cerasus consumption could improve fertility rate by increasing progesterone receptor and HAS2 activity in cumulus cells.

NPR2 is involved in FSH-mediated mouse oocyte meiotic resumption

Background

Previous studies have reported that follicle-stimulating hormone (FSH) is often added to culture media to induce oocyte meiotic resumption and maturation and to improve subsequent embryonic development during in vitro maturation (IVM). However, the underlying mechanisms remain unclear.

Methods

Cumulus-oocyte complexes (COCs) were collected from ovaries 46–48 h after the female mice were intraperitoneally injected with 8 IU equine chorionic gonadotropin (eCG) and then the COCs were cultured in different medium. qRT-PCR analysis was used to assess mRNA expression of EGF-like factors and natriuretic peptide receptor 2 (NPR2). Western Blot analysis was used to assess phosphorylation of mitogen-activated protein kinase 3/1 (MAPK3/1). The oocytes were morphologically assessed for meiotic resumption.

Results

FSH stimulated the expression of EGF-like factors, the activation of MAPK3/1, a decrease in NPR2 mRNA and oocyte meiotic resumption. Moreover, the FSH-induced decrease in NPR2 and oocyte meiotic resumption occurred via the MAPK3/1 singling pathway, which was activated by the epidermal growth factor receptor (EGFR) pathway.

Conclusions

NPR2 is involved in FSH-mediated oocyte meiotic resumption, and this process is associated with the EGFR and MAPK3/1 signaling pathways.

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

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

MicroRNA-378 regulates oocyte maturation via the suppression of aromatase in porcine cumulus cells

We sought to investigate whether miR-378 plays a role in cumulus cells and whether the manipulation of miRNA levels in cumulus cells influences oocyte maturation in vitro. Cumulus-oocyte complexes (COCs) from ovarian follicles had significantly lower levels of precursor and mature miR-378 in cumulus cells surrounding metaphase II (MII) oocytes than cumulus cells surrounding germinal vesicle (GV) oocytes, suggesting a possible role of miR-378 during COC maturation. Overexpression of miR-378 in cumulus cells impaired expansion and decreased expression of genes associated with expansion (HAS2, PTGS2) and oocyte maturation (CX43, ADAMTS1, PGR). Cumulus cell expression of miR-378 also suppressed oocyte progression from the GV to MII stage (from 54 ± 2.7 to 31 ± 5.1%), accompanied by a decrease of growth differentiation factor 9 (GDF9), bone morphogenetic protein 15 (BMP15), zona pellucida 3 (ZP3), and CX37 in the oocytes. Subsequent in vitro fertilization resulted in fewer oocytes from COCs overexpressing miR-378 reaching the blastocyst stage (7.3 ± 0.7 vs. 16.6 ± 0.5%). miR-378 knockdown led to increased cumulus expansion and oocyte progression to MII, confirming a specific effect of miR-378 in suppressing COC maturation. Aromatase (CYP19A1) expression in cumulus cells was also inhibited by miR-378, leading to a significant decrease in estradiol production. The addition of estradiol to IVM culture medium reversed the effect of miR-378 on cumulus expansion and oocyte meiotic progression, suggesting that decreased estradiol production via suppression of aromatase may be one of the mechanisms by which miR-378 regulates the maturation of COCs. Our data suggest that miR-378 alters gene expression and function in cumulus cells and influences oocyte maturation, possibly via oocyte-cumulus interaction and paracrine regulation.

Follicle-stimulating hormone regulates expression and activity of epidermal growth factor receptor in the murine ovarian follicle

Fertility depends on the precise coordination of multiple events within the ovarian follicle to ensure ovulation of a fertilizable egg. FSH promotes late follicular development, including expression of luteinizing hormone (LH) receptor by the granulosa cells. Expression of its receptor permits the subsequent LH surge to trigger the release of ligands that activate EGF receptors (EGFR) on the granulosa, thereby initiating the ovulatory events. Here we identify a previously unknown role for FSH in this signaling cascade. We show that follicles of Fshb(-/-) mice, which cannot produce FSH, have a severely impaired ability to support two essential EGFR-regulated events: expansion of the cumulus granulosa cell layer that encloses the oocyte and meiotic maturation of the oocyte. These defects are not caused by an inability of Fshb(-/-) oocytes to produce essential oocyte-secreted factors or of Fshb(-/-) cumulus cells to respond. In contrast, although expression of both Egfr and EGFR increases during late folliculogenesis in Fshb(+/-) females, these increases fail to occur in Fshb(-/-) females. Remarkably, supplying a single dose of exogenous FSH activity to Fshb(-/-) females is sufficient to increase Egfr and EGFR expression and to restore EGFR-dependent cumulus expansion and oocyte maturation. These studies show that FSH induces an increase in EGFR expression during late folliculogenesis and provide evidence that the FSH-dependent increase is necessary for EGFR physiological function. Our results demonstrate an unanticipated role for FSH in establishing the signaling axis that coordinates ovulatory events and may contribute to the diagnosis and treatment of some types of human infertility.

Knockdown of CEBPβ by RNAi in porcine granulosa cells resulted in S phase cell cycle arrest and decreased progesterone and estradiol synthesis

Cultured ovarian granulosa cells (GCs) are essential models to study molecular mechanisms of gene regulation during folliculogenesis. CCAAT enhancer binding proteins β (CEBPβ) has been identified in the ovary and is critical for follicular growth, ovulation and luteinization in mice. In the present study, hormonal treatment indicated that luteinizing hormone (LH) and exogenous human chorionic gonadotropins (hCG) significantly increased the expression of CEBPβ in porcine GCs. By RNAi-Ready pSIREN-RetroQ-ZsGreen Vector mediated recombinant pshRNA vectors, CEBPβ gene was successfully knocked down in porcine GCs, confirmed by mRNA and protein level analyzed by real time PCR and western blot, respectively. We further found that knockdown of CEBPβ significantly increased the expression of p-ERK1/2. Furthermore, CEBPβ knockdown arrested the GCs at S phase of cell cycle, but had no effects on cell apoptosis. More importantly, it markedly down regulated the concentration of estradiol (E2) and progesterone (P4) in the culture medium. To uncover the regulatory mechanism of CEBPβ knockdown on cell cycle and steroids synthesis, we found that the mRNA expression of bcl-2 (anti-apoptosis), StAR and Runx2 (steroid hormone synthesis) was up-regulated, while genes related to apoptosis (Caspase-3 and p53), hormonal synthesis (CYP11A1) and cell cycle (cyclinA1, cyclinB1, cyclinD1) were down-regulated, suggesting that knockdown of CEBPβ may inhibit apoptosis, regulate cell cycle and hormone secretions at the transcriptional level in porcine GCs. Furthermore, knockdown of CEBPβ significantly increased the expression of PTGS2 and decreased the expression of IGFBP4, Has2 and PTGFR which are important for folliculogenesis in porcine GCs. In conclusion, this study reveals that CEBPβ is a key regulator of porcine GCs through modulation of cell cycle, apoptosis, steroid synthesis, and other regulators of folliculogenesis.

Role of oocyte-derived paracrine factors in follicular development

Mammalian oocytes secrete transforming growth factor β (TGF-β) superfamily proteins, such as growth differentiation factor 9 (GDF9), bone morphogenetic protein 6 (BMP6) and BMP15, and fibroblast growth factors (FGFs). These oocyte-derived paracrine factors (ODPFs) play essential roles in regulating the differentiation and function of somatic granulosa cells as well as the development of ovarian follicles. In addition to the importance of individual ODPFs, emerging evidence suggests that the interaction of ODPF signals with other intra-follicular signals, such as estrogen, is critical for folliculogenesis. In this review, we will discuss the current understanding of the role of ODPFs in follicular development with an emphasis on their interaction with estrogen signaling in regulation of the differentiation and function of granulosa cells.

Knockdown of TrkA in cumulus oocyte complexes (COCs) inhibits EGF-induced cumulus expansion by down-regulation of IL-6

Tyrosine kinase receptor A (TrkA), the high-affinity receptor of nerve growth factor (NGF), is known to play key roles in ovarian follicular development, such as assembly of early follicles and follicular ovulation. However, little is known about the roles of TrkA in cumulus oocyte complex (COC) expansion. In this study, we found that TrkA was abundant in large antral follicles and knockdown of TrkA in COCs attenuated epidermal growth factor (EGF)-induced COC expansion and further decreased the ovulation rate. The effect of TrkA on COC expansion was not mediated through downstream EGF effectors, phosphorylation of extracellular regulated protein kinases 1/2 (ERK1/2) or drosophila mothers against decapentaplegic protein (SMAD), or through up-regulation of COC expansion-related transcripts such as prostaglandin-endoperoxide synthase 2 (Ptgs2), hyaluronan synthase 2 (Has2), TNF-induced protein 6 (Tnfaip6) or pentraxin 3 (Ptx3). However, pharmacological blockade of TrkA transducing activity (K252α) in COCs decreased the mRNA expression and protein secretion of interleukin-6 (IL-6), identified from mRNA microarray of K252α-treated COCs. Meanwhile, knockdown of IL-6 attenuated EGF-induced COC expansion. In addition, IL-6 rescued the inhibitory effect of K252α on EGF-induced cumulus expansion. Therefore, IL-6 may act as a new potential cumulus expansion-related transcript, which may be involved in the integration of TrkA and EGF signaling in affecting COC expansion. Here, we provide mechanistic insights into the roles of TrkA in EGF-induced cumulus expansion. Understanding potential cross-points between TrkA and EGF affecting cumulus expansion will help in the discovery of new therapeutic targets in ovulation-related diseases.

MicroRNA-224 is involved in the regulation of mouse cumulus expansion by targeting Ptx3

MicroRNAs (miRNAs) are indicated to regulate ovarian development in a cell- or stage-specific manner. Our previous study showed that miR-224 is involved in TGF-β1-mediated follicular granulosa cell (GC) growth and estradiol (E2) production during the transition from the preantral to early antral stage by targeting Smad4. In this study, miR-224 was found to target pentraxin 3 (Ptx3), a gene critical for cumulus expansion during ovulation. In addition, PTX3 was up-regulated in mouse mural GCs and cumulus-oocyte complexes (COCs) by TGF-β1 treatment, which was partially mediated by miR-224. The effect of miR-224 during ovulation was further examined in vitro and in vivo by construction of an adenovirus-mediated expression vector for miR-224 (Ad-miR-224). In vitro studies demonstrated that miR-224 could perturb cumulus expansion in EGF-stimulated COCs by decreasing PTX3 secretion. In vivo studies also showed that injection of Ad-miR-224 into ovarian bursa decreased PTX3 expression and disrupted ovulation, which led to a decreased number of implantation sites and offspring being born. These results indicate that miR-224 may affect ovulation and subsequent embryo development by targeting Ptx3, suggesting potential roles for miRNAs in offering new treatments for ovulation disorder-associated infertility, or, conversely, designing new contraceptives.

Bidirectional communication between oocytes and ovarian follicular somatic cells is required for meiotic arrest of mammalian oocytes

Coordinated regulation of oocyte and ovarian follicular development is essential for fertility. In particular, the progression of meiosis, a germ cell-specific cell division that reduces the number of chromosomes from diploid to haploid, must be arrested until just before ovulation. Follicular somatic cells are well-known to impose this arrest, which is essential for oocyte-follicle developmental synchrony. Follicular somatic cells sustain meiotic arrest via the natriuretic peptide C/natriuretic peptide receptor 2 (NPPC/NPR2) system, and possibly also via high levels of the purine hypoxanthine in the follicular fluid. Upon activation by the ligand NPPC, NPR2, the predominant guanylyl cyclase in follicular somatic cells, produces cyclic guanosine monophosphate (cGMP), which maintains meiotic arrest after transfer to the oocyte via gap junctions. Here we report that both the NPPC/NPR2 system and hypoxanthine require the activity of inosine monophosphate dehydrogenase (IMPDH), the rate-limiting enzyme required for the production of guanylyl metabolites and cGMP. Furthermore, oocyte-derived paracrine factors, particularly the growth differentiation factor 9-bone morphogenetic protein 15 heterodimer, promote expression of Impdh and Npr2 and elevate cGMP levels in cumulus cells. Thus, although the somatic compartment of ovarian follicles plays an essential role in the maintenance of oocyte meiotic arrest, as has been known for many years, this function of the somatic cells is surprisingly regulated by signals from the oocyte itself.

Bone morphogenetic protein 15 and fibroblast growth factor 10 enhance cumulus expansion, glucose uptake, and expression of genes in the ovulatory cascade during in vitro maturation of bovine cumulus-oocyte complexes

Oocyte-secreted factors (OSFs) regulate differentiation of cumulus cells and are of pivotal relevance for fertility. Bone morphogenetic protein 15 (BMP15) and fibroblast growth factor 10 (FGF10) are OSFs and enhance oocyte competence by unknown mechanisms. We tested the hypothesis that BMP15 and FGF10, alone or combined in the maturation medium, enhance cumulus expansion and expression of genes in the preovulatory cascade and regulate glucose metabolism favouring hyaluronic acid production in bovine cumulus-oocyte complexes (COCs). BMP15 or FGF10 increased the percentage of fully expanded COCs, but the combination did not further stimulate it. BMP15 increased cumulus cell levels of mRNA encoding a disintegrin and metalloprotease 10 (ADAM10), ADAM17, amphiregulin (AREG), and epiregulin (EREG) at 12 h of culture and of prostaglandin (PG)-endoperoxide synthase 2 (PTGS2), pentraxin 3 (PTX3) and tumor necrosis factor alpha-induced protein 6 (TNFAIP6 (TSG6)) at 22 h of culture. FGF10 did not alter the expression of epidermal growth factor-like factors but enhanced the mRNA expression of PTGS2 at 4 h, PTX3 at 12 h, and TNFAIP6 at 22 h. FGF10 and BMP15 stimulated glucose consumption by cumulus cells but did not affect lactate production or levels of mRNA encoding glycolytic enzymes phosphofructokinase and lactate dehydrogenase A. Each growth factor increased mRNA encoding glucosamine:fructose-6-PO4 transaminases, key enzymes in the hexosamine pathway leading to hyaluronic acid production, and BMP15 also stimulated hyaluronan synthase 2 (HAS2) mRNA expression. This study provides evidence that BMP15 and FGF10 stimulate expansion of in vitro-matured bovine COCs by driving glucose metabolism toward hyaluronic acid production and controlling the expression of genes in the ovulatory cascade, the first acting upon ADAM10, ADAM17, AREG, and EREG and the second on downstream genes, particularly PTGS2.

The absence of ER-β results in altered gene expression in ovarian granulosa cells isolated from in vivo preovulatory follicles

Determining the spatial and temporal expression of genes involved in the ovulatory pathway is critical for the understanding of the role of each estrogen receptor in the modulation of folliculogenesis and ovulation. Estrogen receptor (ER)-β is highly expressed in ovarian granulosa cells, and mice lacking ER-β are subfertile due to inefficient ovulation. Previous work has focused on isolated granulosa cells or cultured follicles and, although informative, provides confounding results due to the heterogeneous cell types present including granulosa and theca cells and oocytes and exposure to in vitro conditions. Herein we isolated preovulatory granulosa cells from wild-type (WT) and ERβ-null mice using laser capture microdissection to examine the genomic transcriptional response downstream of pregnant mare serum gonadotropin (mimicking FSH) and pregnant mare serum gonadotropin/human chorionic gonadotropin (mimicking LH) stimulation. This allows for a direct comparison of in vivo granulosa cells at the same stage of development from both WT and ERβ-null ovaries. ERβ-null granulosa cells showed altered expression of genes known to be regulated by FSH (Akap12 and Runx2) as well as not previously reported (Arnt2 and Pou5f1) in WT granulosa cells. Our analysis also identified 304 genes not previously associated with ERβ in granulosa cells. LH-responsive genes including Abcb1b and Fam110c show reduced expression in ERβ-null granulosa cells; however, novel genes including Rassf2 and Megf10 were also identified as being downstream of LH signaling in granulosa cells. Collectively, our data suggest that granulosa cells from ERβ-null ovaries may not be appropriately differentiated and are unable to respond properly to gonadotropin stimulation.

Hormonal coordination of natriuretic peptide type C and natriuretic peptide receptor 3 expression in mouse granulosa cells

Natriuretic peptide type C (NPPC) and its receptor natriuretic peptide receptor 2 (NPR2) regulate cGMP in ovarian follicles and participate in maintaining oocyte meiotic arrest. We investigated the regulation of Nppc expression in mouse granulosa cells in vivo and in vitro. In mural granulosa cells (MGCs) in vivo, eCG caused an increase in Nppc mRNA, and subsequent human chorionic gonadotropin (hCG) treatment caused a decrease. A culture system was established for MGCs isolated from follicles not stimulated with equine chorionic gonadotropin to further define the mechanisms controlling Nppc expression. In this system, expression of Nppc mRNA was increased by estradiol (E2), with augmentation by follicle-stimulating hormone (FSH), but FSH or luteinizing hormone (LH) alone had no effect. Thus, estrogens are important for regulating Nppc expression, probably by feedback mechanisms enhancing the action of gonadotropins. In MGCs treated with E2 plus FSH in vitro, subsequent treatment with EGF, but not LH, decreased Nppc mRNA. MGCs express higher levels of both Nppc and Lhcgr mRNAs than cumulus cells. Oocyte-derived paracrine factors suppressed cumulus cell Lhcgr but not Nppc expression. Thus, higher Nppc expression by MGCs is not the result of oocyte suppression of expression in cumulus cells. Another possible regulator of the LH-induced NPPC decrease is NPR3, an NPPC clearance receptor. Human chorionic gonadotropin increased Npr3 expression in vivo and LH increased Npr3 mRNA in cultured MGCs, independently of EGF receptor activation. Interestingly, despite the increase in Npr3 mRNA, the hCG-induced decrease in ovarian NPPC occurred normally in an Npr3 mutant (lgj), thus NPR3 probably does not participate in regulation of ovarian NPPC levels or oocyte development.

Hyal-1 but not Hyal-3 deficiency has an impact on ovarian folliculogenesis and female fertility by altering the follistatin/activin/Smad3 pathway and the apoptotic process

Ovarian follicle development is a process regulated by various endocrine, paracrine and autocrine factors that act coordinately to promote follicle growth. However, the vast majority of follicles does not reach the pre-ovulatory stage but instead, undergo atresia by apoptosis. We have recently described a role for the somatic hyaluronidases (Hyal-1, Hyal-2, and Hyal-3) in ovarian follicular atresia and induction of granulosa cell apoptosis. Herein, we show that Hyal-1 but not Hyal-3 null mice have decreased apoptotic granulosa cells after the induction of atresia and an increased number of retrieved oocytes after stimulation of ovulation. Furthermore, young Hyal-1 null mice had a significantly higher number of primordial follicles than age matched wild-type animals. Recruitment of these follicles at puberty resulted in an increased number of primary and healthy preantral follicles in Hyal-1 null mice. Consequently, older Hyal-1 deficient female mice have prolonged fertility. At the molecular level, immature Hyal-1 null mice have decreased mRNA expression of follistatin and higher levels of phospho-Smad3 protein, resulting in increased levels of phospho-Akt in pubertal mice. Hyal-1 null ovarian follicles did not exhibit hyaluronan accumulation. For Hyal-3 null mice, compensation by Hyal-1 or Hyal-2 might be related to the lack of an ovarian phenotype. In conclusion, our results demonstrate that Hyal-1 plays a key role in the early phases of folliculogenesis by negatively regulating ovarian follicle growth and survival. Our findings add Hyal-1 as an ovarian regulator factor for follicle development, showing for the first time an interrelationship between this enzyme and the follistatin/activin/Smad3 pathway.

Cellular content of UDP-N-acetylhexosamines controls hyaluronan synthase 2 expression and correlates with O-linked N-acetylglucosamine modification of transcription factors YY1 and SP1

Hyaluronan, a high molecular mass polysaccharide on the vertebrate cell surface and extracellular matrix, is produced at the plasma membrane by hyaluronan synthases using UDP-GlcNAc and UDP-GlcUA as substrates. The availability of these UDP-sugar substrates can limit the synthesis rate of hyaluronan. In this study, we show that the cellular level of UDP-HexNAc also controls hyaluronan synthesis by modulating the expression of HAS2 (hyaluronan synthase 2). Increasing UDP-HexNAc in HaCaT keratinocytes by adding glucosamine down-regulated HAS2 gene expression, whereas a decrease in UDP-HexNAc, realized by mannose treatment or siRNA for GFAT1 (glutamine:fructose-6-phosphate amidotransferase 1), enhanced expression of the gene. Tracing the UDP-HexNAc-initiated signal to the HAS2 promoter revealed no change in the binding of STAT3, NF-κB, and cAMP response element-binding protein, shown previously to mediate growth factor and cytokine signals on HAS2 expression. Instead, altered binding of SP1 and YY1 to the promoter correlated with cellular UDP-HexNAc content and inhibition of HAS2 expression. siRNA silencing of YY1 and SP1 confirmed their inhibitory effects on HAS2 expression. Reduced and increased levels of O-GlcNAc-modified SP1 and YY1 proteins were associated with stimulation or inhibition of HAS2 expression, respectively. Our data are consistent with the hypothesis that, by regulating the level of protein O-GlcNAc modifications, cellular UDP-HexNAc content controls HAS2 transcription and decreases the effects on hyaluronan synthesis that would result from cellular fluctuations of this substrate.

CCAAT/enhancer-binding proteins (C/EBP)-α and -β are essential for ovulation, luteinization, and the expression of key target genes

LH activation of the epidermal growth factor receptor/RAS/ERK1/2 pathway is essential for ovulation and luteinization because granulosa cell (GC) depletion of ERK1/2 (ERK1/2(gc)(-/-) mice) renders mice infertile. As mediators of ERK1/2-dependent GC differentiation, the CCAAT/enhancer-binding proteins, (C/EBP)α and C/EBPβ, were also disrupted. Female Cebpb(gc)(-/-) mutant mice, but not Cebpa(gc)(-/-) mice, were subfertile whereas Cebpa/b(gc)(-/-) double-mutant females were sterile. Follicles failed to ovulate, ovaries were devoid of corpora lutea, luteal cell marker genes (Lhcgr, Prlr, Ptgfr, Cyp11a1, and Star) were absent, and serum progesterone levels were low. Microarray analyses identified numerous C/EBPα/β target genes in equine chorionic gonadotropin (eCG)-human (h)CG-treated mice. At 4 h post-hCG, a subset (19%) of genes altered in the Cebpa/b-depleted cells was also altered in ERK1/2-depleted cells; hence they are common effectors of ERK1/2. Additional genes down-regulated in the Cebpa/b-depleted cells at 8 and 24 h post-hCG include known (Akr1b7, Runx2, Star, Saa3) and novel (Abcb1b, Apln, Igfbp4, Prlr, Ptgfr Timp4) C/EBP targets and effectors of luteal and vascular cell development. Bhmt, a gene controlling methionine metabolism and thought to be expressed exclusively in liver and kidney, was high in wild-type luteal cells but totally absent in Cebpa/b mutant cells. Because numerous genes potentially associated with vascular development were suppressed in the mutant cells, C/EBPα/β appear to dictate the luteinization process by also controlling genes that regulate the formation of the extensive vascular network required to sustain luteal cells. Thus, C/EBPα/β mediate the terminal differentiation of GCs during the complex process of luteinization.

Estrogen promotes the development of mouse cumulus cells in coordination with oocyte-derived GDF9 and BMP15

The differentiation and function of cumulus cells depend upon oocyte-derived paracrine factors, but studies on the estrogen receptor knockout mice suggested that estrogen also participates in these processes. This study investigates the possible coordination of estrogen and oocytes in the development and function of cumulus cells using cumulus expansion and the expression of transcripts required for expansion as functional endpoints. Preantral granulosa cell-oocyte complexes developed in vitro with 17β-estradiol (E2) exhibited increased levels of cumulus expansion and Has2 transcripts, encoding hyaluronan synthase 2, compared with those developed without E2. Moreover, cumulus cell-oocyte complexes (COCs) isolated from antral follicles and maintained in culture without E2 exhibited reduced cumulus expansion and Has2 mRNA levels compared with freshly isolated COCs. Exogenous E2, provided during the maintenance culture, alleviated these deficiencies. However, when oocytes were removed from COCs, E2 supplementation did not maintain competence to undergo expansion; the presence in culture of either fully grown oocytes or recombinant growth differentiation factor 9 (GDF9) was required. Recombinant bone morphogenetic protein 15, but not fibroblast growth factor 8, augmented the GDF9 effect. Oocytes or GDF9 suppressed cumulus cell levels of Nrip1 transcripts encoding nuclear receptor-interacting protein 1, a potential inhibitor of estrogen receptor signals. Therefore, E2 and oocyte-derived paracrine factors GDF9 and bone morphogenetic protein 15 coordinate to promote the development of cumulus cells and maintain their competence to undergo expansion. Furthermore, suppression of Nrip1 expression in cumulus cells by oocyte may be one mechanism mediating cross talk between oocyte and E2 signals that promotes follicular development.

Cumulus cell gene expression following the LH surge in bovine preovulatory follicles: potential early markers of oocyte competence

Cumulus cells (CCs) are essential for oocytes to reach full development competency and become fertilized. Many major functional properties of CCs are triggered by gonadotropins and governed by the oocyte. Consequently, cumulus may reflect oocyte quality and is often used for oocyte selection. The most visible function of CCs is their ability for rapid extracellular matrix expansion after the LH surge. Although unexplained, LH induces the final maturation and improves oocyte quality. To study the LH signaling and gene expression cascade patterns close to the germinal vesicle breakdown, bovine CCs collected at 2 h before and 6 h after the LH surge were hybridized to a custom-made microarray to better understand the LH genomic action and find differentially expressed genes associated with the LH-induced oocyte final maturation. Functional genomic analysis of the 141 overexpressed and 161 underexpressed clones was performed according to their molecular functions, gene networks, and cell compartments. Following real-time PCR validation of our gene lists, some interesting pathways associated with the LH genomic action on CCs and their possible roles in oocyte final maturation, ovulation, and fertilization are discussed. A list of early potential markers of oocyte competency in vivo and in vitro is thereafter suggested. These early biomarkers are a preamble to understand the LH molecular pathways that trigger the final oocyte competence acquisition process in bovine.

Does bone morphogenetic protein 6 (BMP6) affect female fertility in the mouse?

Bone morphogenetic protein 6 (BMP6) is a transforming growth factor beta superfamily member produced by mammalian oocytes as well as other cell types. Despite well-characterized effects of recombinant BMP6 on granulosa cells in vitro, the function of BMP6 in vivo has been ill-defined. Therefore, the effects of genetic deletion of the Bmp6 gene on female mouse fertility were assessed. The mean litter size of Bmp6(-/-) females was reduced by 22% (P < 0.05) compared to Bmp6(+/+) controls. Not only did Bmp6(-/-) females naturally ovulate 24% fewer eggs, but competence of in vitro-matured oocytes to complete preimplantation development after fertilization in vitro was decreased by 50%. No apparent effect of Bmp6 deletion on either the morphology or the dynamics of follicular development was apparent. Nevertheless, levels of luteinizing hormone (LH)/human chorionic gonadotropin (hCG)-induced transcripts, which encode proteins required for cumulus expansion (HAS2, PTGS2, PTX3, and TNFAIP6), and of epidermal growth factor-like peptides (AREG, BTC, and EREG) were lower in Bmp6(-/-) mice than in controls after administration of a reduced dose of hCG (1 IU) in vivo. LH receptor (Lhcgr) transcript levels were not significantly lower in Bmp6(-/-) granulosa cells, suggesting that BMP6 is required for processes downstream of LH receptors. To assess whether another oocyte-derived BMP, BMP15, could have BMP6-redundant functions in vivo, the fertility of Bmp15/Bmp6 double mutants was assessed. Fertility was not significantly reduced in double-homozygous mutants compared with that in double-heterozygous controls. Therefore, BMP6 promotes normal fertility in female mice, at least in part, by enabling appropriate responses to LH and normal oocyte quality. Thus, Bmp6 probably is part of the complex genetic network that determines female fertility.

Peritoneal adhesion and angiogenesis in ovarian carcinoma are inversely regulated by hyaluronan: the role of gonadotropins

Ovarian carcinoma is the leading cause of death among gynecologic cancers. Although transformation of the outer ovarian epithelium was linked with ovulation, the disease is significantly more prevalent and severe in postmenopausal women. We postulated that menopause could augment ovarian cancer progression through the effects of gonadotropins on multifocal seeding to the mesothelial layer lining the peritoneum. This seeding is mediated by integrins as well as by CD44 interaction with hyaluronan (HA). Here, we report the effect of gonadotropins on HA synthesis and degradation and on peritoneal adhesion. A significant concentration- and time-dependent induction in expression levels of HA synthases (HASs) and hyaluronidases (Hyals) was observed in vitro on stimulation of human epithelial ovarian carcinoma cells by gonadotropins. Hormonal regulation of HA-mediated adhesion was manifested in vivo as well, by fluorescence microscopy of stained MLS multicellular tumor spheroids. The number of spheroids adhered to the mesothelium of ovariectomized CD-1 nude mice 9.5 hours after intraperitoneal insertion was significantly higher than in nonovariectomized mice. Inhibition of HA synthesis by 6-diazo-5-oxo-1-norleucine (DON) both in spheroids and ovariectomized mice significantly reduced the number of adhered spheroids. Thus, the change in the hormonal environment during menopause assists in HA-dependent adherence of ovarian cancer spheroids onto the peritoneum. However, HA is antiangiogenic and it can significantly suppress tumor progression. Accordingly, angiogenesis of the adhered spheroids was significantly elevated in DON-treated tumors. These results can explain the selective pressure that can lead to simultaneously increased tumor expression of both HASs and Hyals.

Mouse oocytes enable LH-induced maturation of the cumulus-oocyte complex via promoting EGF receptor-dependent signaling

LH triggers the maturation of the cumulus-oocyte complex (COC), which is followed by ovulation. These ovarian follicular responses to LH are mediated by epidermal growth factor (EGF)-like growth factors produced by granulosa cells and require the participation of oocyte-derived paracrine factors. However, it is not clear how oocytes coordinate with the EGF receptor (EGFR) signaling to achieve COC maturation. The aim of the present study was to test the hypothesis that oocytes promote the expression of EGFR by cumulus cells, thus enabling them to respond to the LH-induced EGF-like peptides. Egfr mRNA and protein expression were dramatically reduced in cumulus cells of mutant mice deficient in the production of the oocyte-derived paracrine factors growth differentiation factor 9 (GDF9) and bone morphogenetic protein 15 (BMP15). Moreover, microsurgical removal of oocytes from wild-type COCs dramatically reduced expression of Egfr mRNA and protein, and these levels were restored by either coculture with oocytes or treatment with recombinant GDF9 or GDF9 plus recombinant BMP15. Blocking Sma- and Mad-related protein (SMAD)2/3 phosphorylation in vitro inhibited Egfr expression in wild-type COCs and in GDF9-treated wild-type cumulus cells, and conditional deletion of Smad2 and Smad3 genes in granulosa cells in vivo resulted in the reduction of Egfr mRNA in cumulus cells. These results indicate that oocytes promote expression of Egfr in cumulus cells, and a SMAD2/3-dependent pathway is involved in this process. At least two oocyte-derived growth factors, GDF9 and BMP15, are required for EGFR expression by cumulus cells.

Fibroblast growth factors and epidermal growth factor cooperate with oocyte-derived members of the TGFbeta superfamily to regulate Spry2 mRNA levels in mouse cumulus cells

Mouse oocytes produce members of the transforming growth factor beta (TGFbeta) superfamily, including bone morphogenetic protein 15 (BMP15) and growth differentiation factor 9 (GDF9), as well as fibroblast growth factors (FGFs). These growth factors cooperate to regulate cumulus cell function. To identify potential mechanisms involved in these interactions, the ability of fully grown oocytes to regulate expression of BMP or FGF antagonists in cumulus cells was examined. Oocytes promoted cumulus cell expression of transcripts encoding antagonists to TGFbeta superfamily members, including Grem2, Htra1, Htra3, and Nog mRNAs. In contrast, oocytes suppressed cumulus cell expression of Spry2 mRNA, which encodes a regulator of receptor tyrosine kinase signals, such as FGF and epidermal growth factor (EGF) receptor signals. The regulation of Spry2 mRNA levels in cumulus cells was studied further as a model for analysis of potential mechanisms for cooperativity of FGF/EGF signaling with oocyte-derived members of the TGFbeta superfamily. Oocytes suppressed basal and FGF-stimulated Spry2 mRNA levels in cumulus cells but promoted EGF-stimulated levels. Furthermore, recombinant TGFbeta superfamily proteins, including BMP15 and GDF9, mimicked these effects of oocytes. Elevated expression of Spry2 mRNA in cumulus and mural granulosa cells correlated with human chorionic gonadotropin-induced expression of mRNAs encoding EGF-like peptides. Therefore, oocyte-derived members of the TGFbeta superfamily suppress FGF-stimulated Spry2 mRNA levels before the luteinizing hormone surge but promote Spry2 mRNA levels stimulated by EGF receptor-mediated signals after the surge.

The mammalian ovary from genesis to revelation

Two major functions of the mammalian ovary are the production of germ cells (oocytes), which allow continuation of the species, and the generation of bioactive molecules, primarily steroids (mainly estrogens and progestins) and peptide growth factors, which are critical for ovarian function, regulation of the hypothalamic-pituitary-ovarian axis, and development of secondary sex characteristics. The female germline is created during embryogenesis when the precursors of primordial germ cells differentiate from somatic lineages of the embryo and take a unique route to reach the urogenital ridge. This undifferentiated gonad will differentiate along a female pathway, and the newly formed oocytes will proliferate and subsequently enter meiosis. At this point, the oocyte has two alternative fates: die, a common destiny of millions of oocytes, or be fertilized, a fate of at most approximately 100 oocytes, depending on the species. At every step from germline development and ovary formation to oogenesis and ovarian development and differentiation, there are coordinated interactions of hundreds of proteins and small RNAs. These studies have helped reproductive biologists to understand not only the normal functioning of the ovary but also the pathophysiology and genetics of diseases such as infertility and ovarian cancer. Over the last two decades, parallel progress has been made in the assisted reproductive technology clinic including better hormonal preparations, prenatal genetic testing, and optimal oocyte and embryo analysis and cryopreservation. Clearly, we have learned much about the mammalian ovary and manipulating its most important cargo, the oocyte, since the birth of Louise Brown over 30 yr ago.