205 research outputs found

    Localization of DNA methyltransferase-1 during oocyte differentiation, in vitro maturation and early embryonic development in cow

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    DNA methyltransferase-1 (Dnmt1) is involved in the maintenance of DNA methylation patterns and is crucial for normal mammalian development. The aim of the present study was to assess the localization of Dnmt1 in cow, during the latest phases of oocyte differentiation and during the early stages of segmentation. Dnmt1 expression and localization were assessed in oocytes according to the chromatin configuration, which in turn provides an important epigenetic mechanism for the control of global gene expression and represents a morphological marker of oocyte differentiation. We found that the initial chromatin condensation was accompanied by a slight increase in the level of global DNA methylation, as assessed by 5-methyl-cytosine immunostaining followed by laser scanning confocal microscopy analysis (LSCM). RT-PCR confirmed the presence of Dnmt1 transcripts throughout this phase of oocyte differentiation. Analogously, Dnmt1 immunodetection and LSCM indicated that the protein was always present and localized in the cytoplasm, regardless the chromatin configuration and the level of global DNA methylation. Moreover, our data indicate that while Dnmt1 is retained in the cytoplasm in metaphase II stage oocytes and zygotes, it enters the nuclei of 8-16 cell stage embryos. As suggested in mouse, the functional meaning of the presence of Dnmt1 in the bovine embryo nuclei could be the maintainement of the methylation pattern of imprinted genes. In conclusion, the present work provides useful elements for the study of Dnmt1 function during the late stage of oocyte differentiation, maturation and early embryonic development in mammals

    Reductions in the number of mid-sized antral follicles are associated with markers of premature ovarian senescence in dairy cows

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    High-producing dairy cows are subfertile; however, the mechanisms responsible for the decreased fertility are unknown. The aim of the present study was to test the hypothesis that culled dairy cows (4\u20138 years old) characterised by \u2018Lo\u2019 ovaries (i.e. those with <10 mid-antral follicles) are affected by premature ovarian senescence. Cows in which both ovaries were \u2018Lo\u2019 ovaries represented 5% of the total population analysed, and exhibited reduced ovarian size (P < 0.001) and increased perifollicular stroma (P < 0.05) compared with age-matched controls (i.e. cows in which both ovaries had >10 mid-antral follicles; \u2018Hi\u2019 ovaries). The total number of follicles, including healthy and atretic primordial, primary, secondary and small antral follicles, was lower in Lo ovaries (P < 0.01). Interestingly, the primordial follicle population in Lo ovaries was lower (P < 0.05) than in the control. Finally, the follicular fluid of mid-antral follicles from Lo ovaries had reduced oestradiol and anti-M\ufcllerian hormone levels (P < 0.05), but increased progesterone concentrations (P < 0.05). Together, these data account for the reduced fertility of cows with Lo ovaries and are in agreement with previous observations that oocytes isolated from Lo ovaries have reduced embryonic developmental competence. Cows with a specific Lo ovary condition may represent a suitable model to address the causes of low fertility in high-yielding dairy cows, as well as the condition of premature ovarian aging in single-ovulating species

    PGRMC1 localization and putative function in the nucleolus of bovine granulosa cells and oocytes

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    Progesterone Receptor Membrane Component-1 (PGRMC1) is a highly conserved multifunctional protein that is found in numerous systems, including reproductive system. Interestingly, PGRMC1 is expressed at several intracellular locations, including the nucleolus. The aim of this study is to investigate the functional relationship between PGRMC1 and nucleolus. Immunofluorescence experiments confirmed PGRMC1's nucleolar localization in cultured bovine granulosa cells (bGC) and oocytes. Additional experiments conducted on bGC revealed that PGRMC1 co-localizes with nucleolin (NCL), a major nucleolar protein. Furthermore, small interfering RNA (RNAi) mediated gene-silencing experiments showed that when PGRMC1 expression was depleted, NCL translocated from the nucleolus to the nucleoplasm. Similarly, oxidative stress induced by hydrogen peroxide (H2O2) treatment, reduced PGRMC1 immunofluorescent signal in the nucleolus and increased NCL nucleoplasmic signal, when compared to non-treated cells. Although PGRMC1 influenced NCL localization, a direct interaction between these two proteins was not detected using in situ proximity ligation assay. This suggests the involvement of additional molecules in mediating the co-localization of PGRMC1 and nucleolin. Since nucleolin translocates into the nucleoplasm in response to various cellular stressors, PGRMC1's ability to regulate its localization within the nucleolus is likely an important component of mechanism by which cells response to stress. This concept is consistent with PGRMC1's well-described ability to promote ovarian cell survival and provides a rationale for future studies on PGRMC1, NCL and the molecular mechanism by which these two proteins protect against the adverse effect of cellular stressors, including oxidative stress

    Expression of progesterone receptor membrane component-1 in bovine reproductive system during estrous cycle

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    Several reports suggest the participation of progesterone receptor membrane component 1 (PGRMC1) in progesterone signaling in the reproductive system. This study aimed at investigating the presence and localization of PGRMC1 in bovine ovary, oviduct and uterus, during the follicular and luteal phases of the estrous cycle. In the ovary, PGRMC1 has been detected in surface germinal epithelium, granulosa cells, theca cells and in the germinal vesicle of the oocytes at all stages of folliculogenesis. In the corpus luteum the expression of PGRMC1 was influenced by the stage of the estrous cycle. In the oviducts and in the uterus horns, PGRMC1 was immunolocalized in the luminal epithelium, in the muscle layer cells and in the endothelial cells. In the uterus, PGRMC1 was intensely localized also in the glandular endometrium. However, in the oviducts and in the uterus horns, the localization of PGRMC1 was independent on the stage of the estrous cycle and on whether evaluating the ipsilateral or the contralateral organ. In conclusion, the present immunohistochemical study showed that PGRMC1 is located in various compartments of the bovine female reproductive organs. With the exception of the corpora lutea, PGRMC1 localization showed similar pattern during different stages of the estrous cycle

    Effect of pharmacological inhibition of Progesterone receptors PGRMC1 and nPR on bovine oocyte meiosis

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    Folliculogenesis is the fundamental process leading to oocyte maturation and its developmental competence, which are determined by oocyte and follicular cells interplay (Luciano et al., 2004). Recent studies in cattle describe Progesterone (P4) as a key molecule acting during follicle development through different signaling pathways involving different receptors (Aparicio et al., 2011, Nilsson et al., 2009). The aim of this study is to evaluate the effect on oocyte meiotic maturation of inhibiting two P4 receptors: Progesterone Receptor Membrane Component 1 (PGRMC1) and the classic nuclear Progesterone Receptor (nPR) respectively using the specific inhibitors AG205 and Aglepristone. Bovine cumulus cell-oocyte complexes (COCs) and denuded oocytes (DOs) were in vitro matured with different concentrations of AG205. Our results showed a decrease both in first polar body (PBI) extrusion and in the percentage of oocytes reaching MII stage in treated oocytes compared to controls (one way ANOVA, P<0.05); these effects were more marked in DOs, confirming PGRMC1 specific role in the oocyte. In AG205 treated oocytes aberrant meiotic figures were observed, including double metaphase plates or DNA scattered in the ooplasm. In addition, aberrant meiotic plates showed irregular co-localization of PGRMC1 and AURKB; the proteins didn\u2019t localize at the centromeric region of each chromosomes as previously described (Luciano et al., 2013). This results suggests a P4 role in meiotic division mediated by PGRMC1 receptor. By contrast, Aglepristone inhibition of nPR didn\u2019t affect dramatically the percentage of oocytes reaching MII stage of maturation. However, MII plates morphology analysis showed a significantly greater tubulin spindle length. This feature could account for the previously described reduced in vitro embryo development consequent to nPR inhibition (Aparicio et al., 2011). Thus, P4 driven nuclear maturation could act on different oocyte development stages. Further studies are in progress to elucidate P4 complex action in mammalian oocyte functio

    Role of gap junction-mediated communications in regulating large-scale chromatin configuration remodeling and embryonic developmental competence acquisition in fully grown bovine oocyte

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    PURPOSE: This study was aimed to test the hypothesis that gap junction mediated communications (GJC) are required to allow the progressive chromatin configuration remodeling (from GV1 to GV3) process to occur in fully grown oocytes in order to gain the final step of developmental competence acquisition, and that a premature disruption of GJC can alter this process. METHODS: Bovine cumulus-oocytes complexes collected from medium antral follicles were cultured for 2, 4, 6 and 8 h in the presence of 10-4 IU/ml of r-hFSH and with 2 mM of the non-selective PDE inhibitor 3-isobutyl-1-methyl-xanthine (IBMX) to prevent meiotic resumption. GJC functionality and chromatin configuration were monitored during the culture period. After meiotic arrest, the developmental capability of oocytes was assessed after IVM and IVF. RESULTS: IBMX was effective in significantly sustaining GJC up to 6 h and maintaining meiotic arrest, when compared to control group. Moreover, the percentage of oocytes with less condensed chromatin (GV1) decreased within 4 h of culture, while the proportion of GV2 oocytes gradually increased up to 6 h. Interestingly, a decline in the proportion of GV2 oocytes and an increase in the proportion of GV3 oocytes were observed after 6 h of culture, when the major drop of GJC occurred. On the contrary, when GJC were uncoupled by adding 3 mM of 1-heptanol or through cumulus cells removal, chromatin condensation occurred rapidly throughout the culture period, more promptly in denuded oocytes. Moreover, the maintenance of GJC during meiotic arrest was accompanied by a significant increase of developmental competence compared to the control, as indicated by a higher percentage of hatched blastocysts and blastocyst cell number. CONCLUSIONS: Altogether, our data indicate that both paracrine and junctional mechanisms are involved in modulating large-scale chromatin structure during the final phase of oocyte differentiation

    The endothelial nitric oxide synthase/nitric oxide system is involved in the defective quality of bovine oocytes from low mid-antral follicle count ovaries

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    In a previous survey concerning cows of reproductive age, we demonstrated that oocytes isolated from ovaries with 10 medium antral follicles (High ovaries, Hi). The aim of the present study was to evaluate whether a defective endothelial nitric oxide synthase/nitric oxide (eNOS/NO) system and vasculature in healthy medium antral follicles is likely to reduce oocyte competence from Lo ovaries. Thus, experiments were conducted to: (1) immunolocalize eNOS protein during folliculogenesis; (2) quantify eNOS protein/vasculature in the follicle wall; and (3) verify if NO donor, S-nitroso acetyl penicillamine (SNAP) administration during in vitro maturation affects developmental competence of oocytes isolated from Lo ovaries. Endothelial-NOS protein was detected in granulosa and theca cells, as well as in blood vessels from primordial to antral follicles. Quantitative analysis indicated that in medium antral follicles from Lo ovaries, eNOS protein expression and vasculature were reduced (P < 0.05). The addition of SNAP improved blastocyst and hatching rates of oocytes from Lo ovaries, promoting a percentage similar to oocytes from Hi ovaries, and reduced the percentage of apoptotic nuclei in in vitro-produced blastocysts (P < 0.05). Results from our study suggest that in bovine ovaries with low mid antral follicle number, a defective eNOS/NO system is related to a reduced follicle vasculature and may impact oocyte quality, thus inducing a premature decline of fertility

    Morphological markers to select populations of oocytes with different cultural needs for dedicated pre-maturation protocols

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    Oocyte’s chromatin gradually becomes more compacted during the final stage of oocyte development and the level of chromatin compaction is considered a marker of oocyte differentiation [Luciano et al, 2014]. Moreover, several studies demonstrate that in vitro pre-maturation treatments (Pre-IVM), aimed to improve the developmental capability of immature oocytes, might behave differently depending on the oocyte metabolic status, when it is isolated from follicle [Luciano et al., 2011]. This study aims at identifying correlations between cumulus-oocyte complex (COC) morphology and oocyte chromatin configuration and secondly at testing the hypothesis that only fully grown oocytes at earlier stages of differentiation with loosely compacted chromatin  (GV1) can benefit from Pre-IVM treatment.   COCs were collected from bovine 2-6mm ovarian follicles, and further divided in three groups according to their morphology (Class-1, 2 and 3) as previously described [Blondin & Sirard, 1995]. Analysis of chromatin configuration revealed that only Class-1 COC was enriched in GV1 oocyte, while Class-2 and 3 presented a similar distribution of GV1, GV2 and GV3 oocytes, where GV2 and 3 oocytes are characterized by increased chromatin compaction [Lodde et al., 2007]. Then COCs were divided into two groups, one containing Class-1 COCs and the other containing Class-2 and 3 COCs and subjected to pre-IVM for 6 hours in presence of cilostamide and 10-4 UI/ml rhFSH. Finally, COCs underwent standard in vitro maturation (IVM) for 22 hours, in vitro fertilization and embryo culture. Blastocyst rate and embryos cell number were assessed at day 7. Pre-IVM positively affected developmental competences of Class-1, while in Classes 2 and 3 Pre-IVM had detrimental effects.In conclusion COCs morphology could be used as a non-invasive approach to select population of oocyte with different cultural needs. These data could be useful in setting-up dedicated IVM protocols considering specific genes and pathways to improve IVP efficiency

    The Expression of Vasoactive Intestinal Peptide Receptor 1 Is Negatively Modulated by MicroRNA 525-5p

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    Background: The human Vasoactive Intestinal Peptide (VIP) is a neurokine with effects on the immune system where it is involved in promoting tolerance. In this context, one of its receptors, VPAC1, has been found to be down-modulated in cells of the immune network in response to activating stimuli. In particular, the bacterial liposaccaride (LPS), a strong activator of the innate immune system, induces a rapid decrease of VPAC1 expression in monocytes and this event correlates with polymorphisms in the 3'-UTR of the gene. Methodology/Principal Findings: MicroRNA 525-5p, having as putative target the 3'-UTR region of VPAC1, has been analysed for its expression in monocytes and for its role in down-modulating VPAC1 expression. We report here that miR-525-5p is promptly up-regulated in LPS-treated monocytes. This microRNA, when co-transfected in 293T cells together with a construct containing the 3'-UTR of the VPAC1 gene, significantly reduced the luciferase activity in a standard expression assay. The U937 cell line as well as primary monocytes enforced to express miR-525-5p, both down-modulate VPAC1 expression at similar extent. Conclusions/Significance: Our results show that the response to an inflammatory stimulus elicits in monocytes a rapid increase of miR-525-5p that targets a signaling pathway involved in the control of the immune homeostasis
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