Long pentraxin 3 and vitamin D receptor mRNA expression pattern of cumulus granulosa cells isolated from PCOS oocytes at different stages of nuclear maturation.

BACKGROUND: A fine-tuned pro-inflammatory and anti-inflammatory balance in the follicular unit is essential for cumulus expansion and successful ovulation. While the long pentraxin 3 (PTX3) gene is required for the expansion of cumulus cells (CCs), ovulation, resumption of meiosis and fertilization, the vitamin D receptor gene (VDR-X2) is required for intra-follicle redox balance. This study was planned to determine the expression pattern of VDR-X2 and PTX3 mRNA in CCs isolated from germinal vesicle (GV), metaphase I (MI), and metaphase II (MII) oocytes of PCOS patients with ovulatory dysfunction. METHODS: The relative expression of CC-PTX3 and CC-VDR-X2 mRNA were evaluated using qRT-PCR in a total of 79 CC samples collected from individual cumulus-oocyte complex of 40 infertile patients (20 PCOS and 20 non-PCOS normal responders) who underwent ovarian stimulation with the GnRH antagonist protocol. RESULTS: Relative PTX3 mRNA expressions of CCMI-control and CCMII-control showed 3- and 9-fold significant upregulation compared to CCGV-control, respectively. The relative PTX3 mRNA expression of CCMII-control increased approximately three fold compared to CCMI-control. Compared to CCGV-pcos, a 3-fold increase was noted in the relative PTX3 mRNA expression of CCMI-pcos and an approximately 4-fold increase in the PTX3 mRNA expression of CCMII-pcos. Relative PTX3 mRNA expression values of CCMII-pcos and CCMI-pcos were similar. A 6-fold upregulation of relative PTX3 mRNA and a 4-fold upregulation of VDR-X2 mRNA were detected in CCMII-control compared to CCMII-pcos. CC-VDR-X2 expression patterns of the PCOS and control groups overlapped with the CC-PTX3 pattern. Fertilization rates of the PCOS group exhibiting failed transcript expression were similar to normal responders. CONCLUSION: The fact that relative CC-PTX3 and CC-VDR mRNA expression does not increase during the transition from MI to MII stage in PCOS as in normal responders suggests that PTX3 and VDR expression may be defective in cumulus cells of PCOS patients with ovulatory dysfunction.

Unique hyaluronan structure of expanded oocyte-cumulus extracellular matrix in ovarian follicles.

In preovulatory follicles, after the endogenous gonadotropin surge, the oocyte-cumulus complexes (OCCs) produce hyaluronan (HA) in a process called "cumulus expansion". During this process, the heavy chains (HCs) of the serum-derived inter-alpha-trypsin inhibitor (IαI) family bind covalently to synthesized HA and form a unique structure of the expanded cumulus HA-rich extracellular matrix. Understanding the biochemical mechanism of the covalent linkage between HA and the HCs of the IαI family is one of the most significant discoveries in reproductive biology, since it explains basis of the cumulus expansion process running in parallel with the oocyte maturation, both essential for ovulation. Two recent studies have supported the above-mentioned findings: in the first, seven components of the extracellular matrix were detected by proteomic, evolutionary, and experimental analyses, and in the second, the essential role of serum in the process of cumulus expansion in vitro was confirmed. We have previously demonstrated the formation of unique structure of the covalent linkage of HA to HCs of IαI in the expanded gonadotropin-stimulated OCC, as well as interactions with several proteins produced by the cumulus cells: tumor necrosis factor-alpha-induced protein 6, pentraxin 3, and versican. Importantly, deletion of these genes in the mice produces female infertility due to defects in the oocyte-cumulus structure.

Human follicular fluid elicits select dose- and age-dependent effects on mouse oocytes and cumulus-oocyte complexes in a heterologous in vitro maturation assay.

Follicular fluid (FF) is a primary microenvironment of the oocyte within an antral follicle. Although several studies have defined the composition of human FF in normal physiology and determined how it is altered in disease states, the direct impacts of human FF on the oocyte are not well understood. The difficulty of obtaining suitable numbers of human oocytes for research makes addressing such a question challenging. Therefore, we used a heterologous model in which we cultured mouse oocytes in human FF. To determine whether FF has dose-dependent effects on gamete quality, we performed in vitro maturation of denuded oocytes from reproductively young mice (6-12 weeks) in 10%, 50%, or 100% FF from participants of mid-reproductive age (32-36 years). FF impacted meiotic competence in a dose-dependent manner, with concentrations >10% inhibiting meiotic progression and resulting in spindle and chromosome alignment defects. We previously demonstrated that human FF acquires a fibro-inflammatory cytokine signature with age. Thus, to determine whether exposure to an aging FF microenvironment contributes to the age-dependent decrease in gamete quality, we matured denuded oocytes and cumulus-oocyte complexes (COCs) in FF from reproductively young (28-30 years) and old (40-42 years) participants. FF decreased meiotic progression of COCs, but not oocytes, from reproductively young and old (9-12 months) mice in an age-dependent manner. Moreover, FF had modest age-dependent impacts on mitochondrial aggregation in denuded oocytes and cumulus layer expansion dynamics in COCs, which may influence fertilization or early embryo development. Overall, these findings demonstrate that acute human FF exposure can impact select markers of mouse oocyte quality in both dose- and age-dependent manners.

Ovarian stimulation with excessive FSH doses causes cumulus cell and oocyte dysfunction in small ovarian reserve heifers.

Excessive FSH doses during ovarian stimulation in the small ovarian reserve heifer (SORH) cause premature cumulus expansion and follicular hyperstimulation dysgenesis (FHD) in nearly all ovulatory-size follicles with predicted disruptions in cell-signaling pathways in cumulus cells and oocytes (before ovulatory hCG stimulation). These observations support the hypothesis that excessive FSH dysregulates cumulus cell function and oocyte maturation. To test this hypothesis, we determined whether excessive FSH-induced differentially expressed genes (DEGs) in cumulus cells identified in our previously published transcriptome analysis were altered independent of extreme phenotypic differences observed amongst ovulatory-size follicles, and assessed predicted roles of these DEGs in cumulus and oocyte biology. We also determined if excessive FSH alters cumulus cell morphology, and oocyte nuclear maturation before (premature) or after an ovulatory hCG stimulus or during IVM. Excessive FSH doses increased expression of 17 cumulus DEGs with known roles in cumulus cell and oocyte functions (responsiveness to gonadotrophins, survival, expansion, and oocyte maturation). Excessive FSH also induced premature cumulus expansion and oocyte maturation but inhibited cumulus expansion and oocyte maturation post-hCG and diminished the ability of oocytes with prematurely expanded cumulus cells to undergo IVF or nuclear maturation during IVM. Ovarian stimulation with excessive FSH is concluded to disrupt cumulus cell and oocyte functions by inducing premature cumulus expansion and dysregulating oocyte maturation without an ovulatory hCG stimulus yielding poor-quality cumulus-oocyte complexes that may be incorrectly judged morphologically as suitable for IVF during ART.

Effect of putrescine supplementation to in vitro maturation medium on embryo development and quality in cattle.

This study aimed to investigate the effect of putrescine supplementation to maturation medium during in vitro embryo production in cattle on maturation and embryo development/quality. Oocytes obtained from the ovaries of Holstein cattle were used in the study. Obtained cumulus-oocyte complexes were evaluated according to morphological structure, cytoplasmic features, and cumulus cell number, and only Category-I ones were used in the study. Before the in vitro maturation step, oocytes were randomly divided into two groups. In the first group (Putrescine group, n = 159), 0.5 mM putrescine was added to the maturation medium before in vitro maturation. No addition was applied to the maturation medium of the second group (Control group, n = 149). Cumulus expansion degrees of oocytes following maturation (Grade I: poor, Grade II: partial, and Grade III: complete) were determined. In addition, the meiosis of oocytes after maturation was evaluated by differential staining. Then the oocytes were left for fertilization with sperm and finally, possible zygotes were transferred to the culture medium. After determining the developmental stages and quality of the embryos after in vitro culture, only the embryos at the blastocyst stage were stained with the differential staining method to determine the cell numbers. When the cumulus expansion degrees of the groups were evaluated, the Grade III cumulus expansion rate in the putrescine group was higher than the control group (74.21% and 60.4%; respectively) and the Grade I expansion rate (11.95% and 26.17%; respectively) was found lower (p < .05). When the resumption of meiosis was evaluated according to the cumulus expansion degrees, it was determined that the rate of resumption of meiosis increased as the cumulus expansion increased. In addition, the cleavage rates of oocytes and reaching the blastocyst in the putrescine group were found to be higher than in the control group (p < .05). Moreover, inner cell mass, trophectoderm cells, and total cell counts were found to be higher in blastocysts obtained after the putrescine supplementation to the maturation medium compared to the control group (p < .05). As a result, it was determined that the putrescine supplementation to the maturation medium during in vitro embryo production in cattle increased the degree of cumulus expansion and the rate of resumption of meiosis. In addition, putrescine supplementation was thought to increase the rate of reaching the blastocyst of oocytes due to better cell development in embryos.

Effects of follicular fluid exosomes on in vitro maturation of porcine oocytes.

Exosomes are related to effective communication between cells. In this study we aimed to investigate the effect of porcine follicular fluid exosomes (FF-Exo) on cumulus expansion, oocyte mitochondrial membrane potential, and maturation in in vitro culture. We used different concentrations of FF-Exo (Exo-0, Exo-1, Exo-10, Exo-20, and Exo-40) and added them to an oocyte maturation medium. Transmission electron microscopy (TEM), nanoparticle tracking analysis (NTA) and western blot (WB) showed that the isolated samples were exosomes. Immunofluorescence showed that exosomes could be taken up by cumulus cells. Compared with the Exo-0 group, there was no significant difference in oocyte maturation rate in the Exo-1 group (p > 0.05), while the Exo-10 group (p < 0.05), Exo-20 group (p < 0.01) and Exo-40 group (p < 0.01) significantly increased. The maturation rate of the Exo-20 and Exo-40 groups was the highest, and there was no significant difference between the two groups (p > 0.05). However, different concentrations of treatment could not effectively induce cumulus expansion and the results of JC1 showed that it had no significant effect on mitochondrial membrane potential (p > 0.05). In conclusion, the results suggest that porcine FF-Exo are involved in oocyte nuclear maturation.

Morphokinetic parameters of mouse oocyte meiotic maturation and cumulus expansion are not affected by reproductive age or ploidy status.

INTRODUCTION: Morphokinetic analysis using a closed time-lapse monitoring system (EmbryoScope + ™) provides quantitative metrics of meiotic progression and cumulus expansion. The goal of this study was to use a physiologic aging mouse model, in which egg aneuploidy levels increase, to determine whether there are age-dependent differences in morphokinetic parameters of oocyte maturation. METHODS: Denuded oocytes and intact cumulus-oocyte complexes (COCs) were isolated from reproductively young and old mice and in vitro matured in the EmbryoScope + ™. Morphokinetic parameters of meiotic progression and cumulus expansion were evaluated, compared between reproductively young and old mice, and correlated with egg ploidy status. RESULTS: Oocytes from reproductively old mice were smaller than young counterparts in terms of GV area (446.42 ± 4.15 vs. 416.79 ± 5.24 µm2, p < 0.0001) and oocyte area (4195.71 ± 33.10 vs. 4081.62 ± 41.04 µm2, p < 0.05). In addition, the aneuploidy incidence was higher in eggs with advanced reproductive age (24-27% vs. 8-9%, p < 0.05). There were no differences in the morphokinetic parameters of oocyte maturation between oocytes from reproductively young and old mice with respect to time to germinal vesicle breakdown (GVBD) (1.03 ± 0.03 vs. 1.01 ± 0.04 h), polar body extrusion (PBE) (8.56 ± 0.11 vs. 8.52 ± 0.15 h), duration of meiosis I (7.58 ± 0.10 vs. 7.48 ± 0.11 h), and kinetics of cumulus expansion (0.093 ± 0.002 vs. 0.089 ± 0.003 µm/min). All morphokinetic parameters of oocyte maturation were similar between euploid and aneuploid eggs irrespective of age. CONCLUSION: There is no association between age or ploidy and the morphokinetics of mouse oocyte in vitro maturation (IVM). Future studies are needed to evaluate whether there is an association between morphokinetic dynamics of mouse IVM and embryo developmental competence.

Quantitative morphokinetic parameters identify novel dynamics of oocyte meiotic maturation and cumulus expansion†.

Meiotic maturation and cumulus expansion are essential for the generation of a developmentally competent gamete, and both processes can be recapitulated in vitro. We used a closed time-lapse incubator (EmbryoScope+™) to establish morphokinetic parameters of meiotic progression and cumulus expansion in mice and correlated these outcomes with egg ploidy. The average time to germinal vesicle breakdown (GVBD), time to first polar body extrusion (PBE), and duration of meiosis I were 0.91 ± 0.01, 8.82 ± 0.06, and 7.93 ± 0.06 h, respectively. The overall rate of cumulus layer expansion was 0.091 ± 0.002 µm/min, and the velocity of expansion peaked during the first 8 h of in vitro maturation (IVM) and then slowed. IVM of oocytes exposed to Nocodazole, a microtubule disrupting agent, and cumulus oocyte complexes (COCs) to 4-methylumbelliferone, a hyaluronan synthesis inhibitor, resulted in a dose-dependent perturbation of morphokinetics, thereby validating the system. The incidence of euploidy following IVM was >90% for both denuded oocytes and intact COCs. No differences were observed between euploid and aneuploid eggs with respect to time to GVBD (0.90 ± 0.22 vs. 0.97 ± 0.19 h), time to PBE (8.89 ± 0.98 vs. 9.10 ± 1.42 h), duration of meiosis I (8.01 ± 0.91 vs. 8.13 ± 1.38 h), and overall rate and kinetics of cumulus expansion (0.089 ± 0.02 vs 0.088 ± 0.03 µm/min) (P > 0.05). These morphokinetic parameters provide novel quantitative and non-invasive metrics for the evaluation of meiotic maturation and cumulus expansion and will enable screening compounds that modulate these processes.

Expression profiling and function analysis identified new microRNAs regulating cumulus expansion and apoptosis in cumulus cells.

Although microRNAs (miRNAs) expressed in cumulus cells (CCs) may be used to select competent oocytes/embryos, only a limited number of such miRNAs has been reported. To identify more miRNAs that regulate cumulus expansion (CE) and CC apoptosis, we first established that mouse cumulus-oocyte complexes (COCs) cultured in expansion-supporting medium supported full CE while undergoing mild apoptosis, whereas mouse oocytectomized COCs (OOXs) cultured in apoptosis-triggering medium underwent severe apoptosis while supporting no CE. RNA- and miRNA-sequencing and bioinformatics using CCs from these cultured COCs/OOXs identified candidate apoptosis- and/or CE-regulating miRNAs. Transfection of COCs/OOXs with miRNA mimic or inhibitor validated that miR-212-5p and 149-5p promoted CE by facilitating Has2 expression; miR-31-5p and 27a-3p promoted CE by increasing both Has2 and Ptx3 expression; and miR-351-5p and 503-5p inhibited CE by suppressing Ptx3 expression. Furthermore, miR-212-5p, 149-5p and Nov798 inhibited CC apoptosis, involving both Bcl2/Bax and Fas signaling. Analysis using in vivo matured COCs further verified the above apoptosis- and/or CE-regulating miRNAs, except for miR-149-5p. In conclusion, this study identified and validated new CE- and apoptosis-regulating miRNAs in CCs, which could be used as biomarkers to select competent oocytes/embryos and for elucidating how the oocyte-derived factors regulate CE and CC apoptosis.

Oocyte-secreted factor TGFB2 enables mouse cumulus cell expansion in vitro.

Cumulus expansion is necessary for the release of a fertilizable oocyte from the ovary, which is critical for the normal fertilization of mammals. Cumulus expansion requires cooperation between epidermal growth factor (EGF)-like growth factors and oocyte paracrine factors. Growth differentiation factor 9 (GDF9) and bone morphogenetic protein 15 (BMP15) are well-known paracrine factors secreted by oocytes. In addition, transforming growth factor-ß2 (TGFB2) was primarily expressed in oocytes and its membrane receptors type 1 receptor (TGFBR1) and type 2 receptor (TGFBR2) were located in cumulus cells. In our present study, TGFB2 induced expansion of oocytectomized (OOX) complexes and increased the expression of expansion-related genes in the presence of EGF, suggesting that TGFB2 enables cumulus expansion. Inhibition of TGF-ß signaling with SD208 blocked TGFB2-promoted cumulus expansion. Furthermore, in the culture of OOX complexes from mice of Tgfbr2-specific depletion in granulosa cells, TGFB2-promoted cumulus expansion and the expression of expansion-related genes were impaired. These results suggest that TGFB2 could induce cumulus expansion through TGFBR-SMAD2/3 signaling. Tgfb2-specific depletion in oocytes using Zp3-Cre mice had no effect on cumulus expansion in vivo, possibly due to the compensatory effect of other cumulus expansion-enabling factors. Taken together, TGFB2 is involved in expansion-related gene expression and consequent cumulus expansion.

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.

Silica encapsulation of ZnO nanoparticles reduces their toxicity for cumulus cell-oocyte-complex expansion.

BACKGROUND: Metal oxide nanoparticles (NPs) are increasingly used in many industrial and biomedical applications, hence their impact on occupational and public health has become a concern. In recent years, interest on the effect that exposure to NPs may exert on human reproduction has grown, however data are still scant. In the present work, we investigated whether different metal oxide NPs interfere with mouse cumulus cell-oocyte complex (COC) expansion. METHODS: Mouse COCs from pre-ovulatory follicles were cultured in vitro in the presence of various concentrations of two types of TiO2 NPs (JRC NM-103 and NM-104) and four types of ZnO NPs (JRC NM-110, NM-111, and in-house prepared uncoated and SiO2-coated NPs) and the organization of a muco-elastic extracellular matrix by cumulus cells during the process named cumulus expansion was investigated. RESULTS: We show that COC expansion was not affected by the presence of both types of TiO2 NPs at all tested doses, while ZnO NM-110 and NM-111 induced strong toxicity and inhibited COCs expansion at relatively low concentration. Medium conditioned by these NPs showed lower toxicity, suggesting that, beside ion release, inhibition of COC expansion also depends on NPs per se. To further elucidate this, we compared COC expansion in the presence of uncoated or SiO2-coated NPs. Differently from the uncoated NPs, SiO2-coated NPs underwent slower dissolution, were not internalized by the cells, and showed an overall lower toxicity. Gene expression analysis demonstrated that ZnO NPs, but not SiO2-coated ZnO NPs, affected the expression of genes fundamental for COC expansion. Dosimetry analysis revealed that the delivered-to-cell mass fractions for both NPs was very low. CONCLUSIONS: Altogether, these results suggest that chemical composition, dissolution, and cell internalization are all responsible for the adverse effects of the tested NPs and support the importance of a tailored, safer-by-design production of NPs to reduce toxicity.

Effects of oocyte-derived growth factors on the growth of porcine oocytes and oocyte-cumulus cell complexes in vitro.

During oocyte growth and follicle development, oocytes closely communicate with cumulus cells. We examined the effects of oocyte-derived growth factors, growth differentiation factor 9 (GDF9) and bone morphogenetic protein 15 (BMP15), on the growth and acquisition of meiotic competence of porcine oocytes collected from early antral follicles (1.2-1.5 mm). First, we confirmed that GDF9 and BMP15 mRNAs were expressed almost exclusively in the oocytes. Oocyte-cumulus cell complexes (OCCs) collected from early antral follicles were cultured in growth medium supplemented with 0-100 ng/ml of GDF9 or BMP15 for 5 days. GDF9 dose-dependently increased the OCC diameter, while BMP15 did not. GDF9 and BMP15 had no significant effects on oocyte growth (P > 0.05). When OCCs that had been cultured with 50 and 100 ng/ml BMP15 were subjected to a subsequent maturation culture, they expanded fully by gonadotropic stimulation and 49% and 61% of oocytes matured to metaphase II (MII), respectively. In contrast, GDF9 did not promote cumulus expansion, and < 10% of oocytes matured to MII. Based on the difference in cumulus expansion, we compared the expression of luteinizing hormone/choriogonadotropin receptor (LHCGR) and follicle stimulating hormone receptor (FSHR) mRNAs in cumulus cells. The level of LHCGR mRNA was increased in cumulus cells of the BMP15 group, although there were no significant differences in FSHR mRNA levels among the groups. These results suggest that GDF9 promotes the growth of OCCs and that BMP15 promotes LHCGR mRNA expression in cumulus cells during oocyte growth culture, which may contribute to cumulus expansion and oocyte maturation.

CREB activity is required for epidermal growth factor-induced mouse cumulus expansion.

The release of a fertilizable oocyte from the ovary is dependent upon the expansion of the cumulus cells. The expansion requires cooperation between epidermal growth factor (EGF) family peptide-activated mitogen-activated protein kinase (MAPK)3/1 and oocyte paracrine factor-activated-Sma- and Mad-related protein (SMAD)2/3 signaling in cumulus cells. However, the mechanism underlying (MAPK)3/1 signaling is unclear. In the present study, the EGF-activation of EGF receptor (EGFR) induced cyclic adenosine 3',5'-monophosphate (cAMP) response element-binding protein (CREB) phosphorylation in cumulus cells, and the interruption of CREB functional complex formation by naphthol AS-E phosphate (KG-501) completely blocked the EGF-stimulated expansion-related gene expression. EGF-stimulated phosphorylation of CREB was completely inhibited by MAPK3/1 inhibitor U0126, suggesting that EGF-activated MAPK3/1 results in the activation of CREB for cumulus expansion. Also, the role of EGF-stimulated calcium signaling was studied. Calcium-elevating reagents ionomycin and sphingosine-1-phosphate mimicked, but calcium chelators bis-(o'aminophenoxy)-ethane-N,N,N,N-tetraacetic acid, tetra(acetoxymethyl)-ester, and 8-(N,N-diethylamino)-octyl-3,4,5-trimethoxybenzoate abolished the activity of EGF on CREB phosphorylation, cumulus expansion, and expansion-related gene expression. Furthermore, EGF-induced cumulus expansion was inhibited by calmodulin (CaM)-dependent protein kinase II (CaMKII) inhibitors, KN-93 and autocamtide-2-related inhibitory peptide. However, the inhibition of SMAD2/3 activity by removal of oocyte from cumulus-oocyte complexes did not affect the EGF-induced CREB phosphorylation, indicating that EGF-activated CREB is independent of oocyte-activated SMAD2/3 signaling. Therefore, EGF-induced CREB activity by MAPK3/1 and Ca2+ /CaMKII signaling pathways promotes the expansion-related gene expression and consequent cumulus expansion.

Fibroblast growth factor 2 regulates cumulus differentiation under the control of the oocyte.

PURPOSE: We first assessed regulation of FGF2 expression in cumulus cells by FSH and oocyte-secreted factors during in vitro maturation (IVM). Then, we tested the hypothesis that FGF2 regulates meiotic progression, cumulus expansion, and apoptosis in cumulus-oocyte complexes (COC) undergoing IVM. METHODS: In vitro maturation of bovine COC was utilized as a model to assess regulation of FGF2 expression by FSH and oocyte-secreted factors (via microsurgical removal of the oocyte), as well as effects of graded doses of FGF2 on meiotic progression, degree of cumulus expansion, dissociation of cumulus cells, and cumulus cells apoptosis. Expression of genes regulating functional endpoints altered by FGF2 treatment was assessed in cumulus cells by real-time PCR. Cultures were replicated 4-5 times and effects of treatments were tested by ANOVA. RESULTS: FGF2 mRNA expression was increased by FSH and oocyte-secreted factors during IVM. Addition of FGF2 to the IVM medium advanced meiosis resumption, decreased the ease with which cumulus cells were dissociated, and inhibited cumulus cells apoptosis. Decreased cumulus dissociation was accompanied by decreased expression of TNFAIP6. CONCLUSIONS: This is the first study showing that FGF2 expression is regulated by the oocyte in cumulus cells. Moreover, we report novel effects of FGF2 on cumulus cell survival and extracellular matrix (ECM) quality during IVM that may favor acquisition of developmental competence and suggest physiological roles during the final steps of COC differentiation.

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.

Sonic hedgehog signaling mediates resveratrol to improve maturation of pig oocytes in vitro and subsequent preimplantation embryo development.

The beneficial effects of resveratrol on in vitro maturation (IVM) have been explained mainly by indirect antioxidant effects and limited information is available on the underlying mechanism by which resveratrol acts directly on porcine cumulus oocyte complexes (COCs). Recently, several studies reported that sonic hedgehog (SHH) signaling mediates resveratrol to exert its biological activities. Furthermore, SHH is an important signaling molecule for follicle development, oocyte maturation, and embryo development. Therefore, to elucidate the relationship between resveratrol and SHH signaling, we designed three groups: (i) control; (ii) resveratrol; and (iii) resveratrol with cyclopamine (SHH signaling inhibitor). We evaluated the effects of these agents on cumulus expansion, oocyte maturation, embryo development after parthenogenetic activation, expression levels of mRNAs in cumulus cells, oocytes and blastocysts, and protein expression in COCs. Resveratrol significantly increased the proportion of COCs exhibiting complete cumulus expansion (degree 4), oocyte nuclear maturation, cleavage and blastocyst formation rates and total cell numbers, which were blocked in the presence of cyclopamine. At the same time, a significant increase in the expression levels of mRNAs related to cumulus expansion, oocyte maturation and SHH signaling-related mRNAs and proteins from the resveratrol treatment group was also inhibited by simultaneous addition of cyclopamine. In conclusion, our results indicate that SHH signaling mediates resveratrol to improve porcine cumulus expansion, oocyte maturation, and subsequent embryo development.

Stimulatory Effects of Melatonin on Porcine In Vitro Maturation Are Mediated by MT2 Receptor.

Melatonin is a multifunctional molecule with numerous biological activities. The fact that melatonin modulates the functions of porcine granulosa cells via the MT2 receptor suggests the possibility of MT2 receptor-mediation for melatonin to promote cumulus expansion of porcine cumulus-oocyte complexes (COCs). Therefore, we investigated the presence of MT2 in porcine COCs, and the effects of melatonin with or without selective MT2 antagonists (luzindole and 4-P-PDOT) on this process; COCs underwent in vitro maturation culturing with six different conditions (control, melatonin, luzindole, 4-P-PDOT, melatonin + luzindole or melatonin + 4-P-PDOT). Cumulus expansion, oocyte nuclear maturation, and subsequent embryo development after parthenogenetic activation (PA) were evaluated. In experiment 1, MT2 was expressed in both oocytes and cumulus cells. In experiment 2, melatonin significantly increased the proportion of complete cumulus expansion (degree 4), which was inhibited by simultaneous addition of either luzindole or 4-P-PDOT. A similar pattern was observed in the expression of genes related to cumulus expansion, apoptosis, and MT2. In experiment 3, no significant difference was observed in immature, degenerate, and MII oocyte rates among the groups. In experiment 4, melatonin significantly increased blastocyst formation rates and total blastocyst cell numbers after PA, but these effects were abolished when either luzindole or 4-P-PDOT was added concomitantly. In conclusion, our results indicate that the MT2 receptor mediated the stimulatory effects of melatonin on porcine cumulus expansion and subsequent embryo development.

The effect of poly(ADP-ribosyl)ation inhibition on the porcine cumulus-oocyte complex during in vitro maturation.

Poly(ADP-ribosyl)ation (PARylation) plays important roles in DNA repair, apoptosis, transcriptional regulation, and cell death, and occurs via the activity of poly(ADP-ribose) polymerases (PARPs). Previous studies have shown that PARylation affects mouse and porcine pre-implantation development and participates in mechanisms of autophagy. However, there have not yet been reported the role of PARylation during in vitro maturation (IVM) of porcine oocytes. Thus, we investigated the effect of PARylation inhibition on this process; cumulus-oocyte complexes (COCs) were cultured with 3-aminobenzamide (3-ABA, PARP inhibitor) during porcine IVM. Full cumulus expansion was significantly reduced (10.34 ± 1.23 [3-ABA] vs. 48.17 ± 2.03% [control]), but nuclear maturation rates were not changed in the 3-ABA treatment group. Especially, we observed that cumulus cells were little expanded after 22 h in 3-ABA treated COCs. The mRNA expression levels of oocyte maturation- and cumulus expansion-related genes were evaluated at 22 and 44 h. GDF9, BMP15, COX-2, and PTX3 expression were upregulated at 44 h, whereas the levels of HAS2 and TNFAIP6 were downregulated in the 3-ABA treated group. Furthermore, 3-ABA treatment significantly decreased the developmental rate (28.24 ± 1.06 vs. 40.24 ± 3.03%) and total cell number (41.12 ± 2.10 vs. 50.38 ± 2.27), but increased the total apoptotic index (6.44 ± 0.81 vs. 3.08 ± 0.51) in parthenogenetically activated embryos. In conclusion, these results showed that PARylation regulates cumulus expansion through the regulation of gene expression and affects developmental competence and quality in parthenogenetic embryos.

Ovary-specific depletion of the nuclear receptor Nr5a2 compromises expansion of the cumulus oophorus but not fertilization by intracytoplasmic sperm injection.

The orphan nuclear receptor, liver receptor homolog-1 (aka Nuclear receptor subfamily 5, Group A, Member 2 (Nr5a2)), is widely expressed in mammalian tissues, and its ovarian expression is restricted to granulosa cells of activated follicles. We employed the floxed Nr5a2 (Nr5a2f/f) mutant mouse line and two granulosa-specific Cre lines, Anti-Müllerian hormone receptor- 2 (Amhr2Cre) and transgenic cytochrome P450 family 19 subfamily A polypeptide 1 (tgCyp19Cre), to develop two tissue- and time-specific Nr5a2 depletion models: Nr5a2Amhr2-/- and Nr5a2Cyp19-/-. In the Nr5a2Cyp19-/- ovaries, Nr5a2 was depleted in mural granulosa, but not cumulus cells. We induced follicular development in mutant and wild-type (control, CON) mice with equine chorionic gonadotropin followed 44 h later treatment with human chorionic gonadotropin (hCG) to induce ovulation. Both Nr5a2Amhr2-/- and Nr5a2Cyp19-/- cumulus-oocyte complexes underwent a reduced degree of expansion in vitro relative to wild-type mice. We found downregulation of epiregulin (Ereg), amphiregulin (Areg), betacellulin (Btc) and tumor necrosis factor stimulated gene-6 (Tnfaip6) transcripts in Nr5a2Amhr2-/- and Nr5a2Cyp19-/- ovaries. Tnfaip6 protein abundance, by quantitative immunofluorescence, was likewise substantially reduced in the Nr5a2-depleted model. Transcript abundance for connexin 43 (Gja1) in granulosa cells was lower at 0 h and maximum at 8 h post-hCG in both Nr5a2Amhr2-/- and Nr5a2Cyp19-/- follicles, while Gja1 protein was not different prior to the ovulatory signal, but elevated at 8 h in Nr5a2Amhr2-/- and Nr5a2Cyp19-/- follicles. In both mutant genotypes, oocytes can mature in vivo and resulting embryos were capable of proceeding to blastocyst stagein vitro. We conclude that Nr5a2 is essential for cumulus expansion in granulosa cells throughout follicular development. The disruption of Nr5a2 in follicular somatic cells does not affect the capacity of the oocyte to be fertilized by intracytoplasmic sperm injection.