Differential response of cumulus cell-enclosed and denuded mouse oocytes in a meiotic induction model system

Effect of early cumulus cells removal and early rescue ICSI on pregnancy outcomes in high-risk patients of fertilization failure

OBJECTIVE

The objective of this retrospective study was to evaluate clinical outcomes of early cumulus cells removal and early rescue intracytoplasmic sperm injection (ICSI) in high-risk patients of fertilization failure during human in vitro fertilization (IVF).

METHODS

A total of 5,518 patients were enrolled between January 2014 to December 2016. Of which 505 couples performed short insemination with >30% fertilization rate were included in short-term IVF group, 102 patients detected total fertilization failure (TFF) were treated with early rescue ICSI (R-ICSI group), and 4911 couples underwent conventional IVF with overnight co-incubation of gametes (traditional IVF group). The clinical outcomes were analyzed among the three groups.

RESULTS

The embryo implantation rates (40.34%, 39.78% and 42.42% for traditional, short-term IVF and R-ICSI groups, respectively) were comparable in the three groups. The clinical pregnancy rates among traditional IVF group, short-term IVF group and R-ICSI group were 57.95%, 57.03% and 60.78%, respectively, and the difference among three groups didn't reach significance.

CONCLUSION

The present study indicated that short insemination had no detrimental effects on clinical outcomes in human IVF and could prevent the occurrence of TFF combined with early rescue ICSI for high-risk patients of fertilization failure, which attained acceptable pregnancy outcomes.

Inductions of granulosa cell luteinization and cumulus expansion are dependent on the fibronectin-integrin pathway during ovulation process in mice

It has been known that EGF-like factor secreted from LH-stimulated granuloma cells acts on granulosa cells and cumulus cells to induce ovulation process. Granulosa cells are changed the morphology with differentiating cell functions to produce progesterone. Cumulus cells are detached to make a space between the cells to accumulate hyaluronan rich matrix. LH also changes extracellular matrix (ECM) components including fibronectin in the follicular walls and granulosa cell layers. EGF like factor and fibronectin synergistically play important roles in numerous cell functions, especially cancer cell migration, estimating that fibronectin would impact on granulosa cells and cumulus cells. To clear this hypothesis, the localizations of fibronectin and its receptor integrin were observed by immunofluorescence technique. The functions were monitored by the detection of downstream signaling pathway, focal adhesion kinase (FAK). The pharmacological approach in both in vivo and in vitro were used for analyzing the physiological roles of FAK during ovulation process. The immunofluorescence staining revealed that fibronectin and integrin were observed in granulosa cells, cumulus cells and the space between cumulus cells and oocyte at 4 and 8 h after hCG injection. Concomitantly with the changes of fibronectin-integrin localization, FAK was phosphorylated in periovulatory follicles. The injection of FAK inhibitor suppressed not only ovulation but also luteinization of granulosa cells and cumulus expansion. In cultured-granulosa cells, fibronectin-integrin synergistically activated FAK with amphiregulin (AREG). Such cooperative stimulations induced a morphological change in granulosa cells, which resulted in the maximum level of progesterone production via the induction of Hsd3b. When cumulus-oocyte complexes (COCs) were cultured with AREG in the presence of serum, the maximum level of cumulus expansion was observed. The AREG-induced cumulus expansion was also suppressed by FAK inhibitor. Thus, it is concluded that fibronectin and AREG synergistically activate FAK not only in granulosa cells and cumulus cells to induce successful ovulation process.

The value of second polar body detection 4 hours after insemination and early rescue ICSI in preventing complete fertilisation failure in patients with borderline semen

In this study we evaluated the value of short-time insemination and early rescue intra-cytoplasmic sperm injection (ICSI) in preventing the occurrence of complete fertilisation failure for mild or moderate male infertility patients. A total of 866 couples with borderline semen who underwent in vitro fertilisation treatment in 2010 were included. Regular insemination was performed between January and June of 2010 and short-term insemination was performed from July through December 2010, where, as early as 4h after insemination, oocytes were denuded from cumulus cells and extrusion of the second polar body was evaluated. Of the 4153 mature oocytes with a detectable second polar body 4 h after insemination, 3874 (93.3%) showed signs of fertilisation on Day 1. Where no second polar body was present in any of the retrieved oocytes for a given patient, rescue ICSI was performed immediately. Similar rates of normal fertilisation and percentage of good-quality embryos were obtained between early rescue ICSI and regular ICSI. Clinical pregnancy occurred in 16 of 43 patients (37.2%) receiving early rescue ICSI. Our results showed early rescue ICSI in combination with evaluation of the second polar body 4 h following insemination is an effective method to prevent complete fertilisation failure for patients with mild or moderate male infertility.

The impact of obesity on egg quality

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

Regulation of the G2/M transition in rodent oocytes

Regulation of maturation in meiotically competent mammalian oocytes is a complex process involving the carefully coordinated exchange of signals between the somatic and germ cell compartments of the ovarian follicle via paracrine and cell-cell coupling pathways. This review highlights recent advances in our understanding of how such signaling controls both meiotic arrest and gonadotropin-triggered meiotic resumption in competent oocytes and relates them to the historical context. Emphasis will be on rodent systems, where many of these new findings have taken place. A regulatory scheme is then proposed that integrates this information into an overall framework for meiotic regulation that demonstrates the complex interplay between different follicular compartments.

Nongenomic steroid-triggered oocyte maturation: of mice and frogs

Luteinizing hormone (LH) mediates many important processes in ovarian follicles, including cumulus cell expansion, changes in gap junction expression and activity, sterol and steroid production, and the release of paracrine signaling molecules. All of these functions work together to trigger oocyte maturation (meiotic progression) and subsequent ovulation. Many laboratories are interested in better understanding both the extra-oocyte follicular processes that trigger oocyte maturation, as well as the intra-oocyte molecules and signals that regulate meiosis. Multiple model systems have been used to study LH-effects in the ovary, including fish, frogs, mice, rats, pigs, and primates. Here we provide a brief summary of oocyte maturation, focusing primarily on steroid-triggered meiotic progression in frogs and mice. Furthermore, we present new studies that implicate classical steroid receptors rather than alternative non-classical membrane steroid receptors as the primary regulators of steroid-mediated oocyte maturation in both of these model systems.

Paracrine factors from cumulus-enclosed oocytes ensure the successful maturation and fertilization in vitro of denuded oocytes in the cat model

OBJECTIVE

To better characterize cumulus-oocyte interactions during oocyte maturation and fertilization in the cat model.

DESIGN

Experimental in vitro study.

SETTING

Smithsonian Institution.

ANIMAL(S)

Domestic shorthair cats.

INTERVENTION(S)

Groups of denuded oocytes (DOs) and cumulus-oocyte complexes (COCs) were subjected to in vitro maturation (with or without FSH and LH, with or without the gap junction disruptor 1-heptanol, in separated groups or in coculture) and inseminated in vitro (IVF; in separated groups or in coculture).

MAIN OUTCOME MEASURE(S)

Nuclear maturation, pronuclear formation, kinetics of early embryo cleavage, and blastocyst formation and quality after different in vitro conditions were compared between DOs cultured separately and DOs cocultured with COCs.

RESULT(S)

Without FSH and LH, the removal of cumulus cells prevented spontaneous meiotic resumption in DOs. With FSH and LH, groups of DOs progressed to the metaphase I stage but fully advanced to metaphase II only in coculture with intact (nondisrupted) COCs. Groups of DOs cultured separately were fertilized poorly and exhibited no blastocyst formation. In contrast, DOs cocultured with intact COCs during in vitro maturation and IVF recovered fertilizability, and approximately 35% formed blastocysts.

CONCLUSION(S)

Paracrine factors produced by cumulus-enclosed oocytes in the cat model will help to develop synthetic media for successful in vitro culture of DOs.

EGF-like peptides mediate FSH-induced maturation of cumulus cell-enclosed mouse oocytes

This study was carried out to examine the participation of epidermal growth factor (EGF)-like peptides in the induction of germinal vesicle breakdown (GVB) in mouse cumulus cell-enclosed oocytes (CEO). The EGF-like peptide, amphiregulin (AR), dose-dependently stimulated meiotic resumption in CEO, but not denuded oocytes (DO) maintained in meiotic arrest with 300 microM dbcAMP. The EGF receptor (EGFR) kinase inhibitor, AG1478, blocked meiotic resumption induced by FSH and AR in CEO, but had no effect in DO. FSH-induced maturation was also suppressed by antisera to both EGFR and EGF. Maturation occurred with slightly faster kinetics in AR-stimulated CEO when compared to FSH-stimulated CEO. When CEO were maintained in meiotic arrest with a low level of dbcAMP, FSH was initially inhibitory to maturation and later stimulatory; the stimulatory phase was prevented by AG1478, indicating mediation by EGF-like peptides. Pulsing CEO with high levels of dbcAMP also stimulated GVB and could be blocked by AG1478. Treatment of arrested CEO with PKC agonists stimulated maturation and this was prevented with AG1478 as well as antibodies to EGFR. FSH-induced maturation of dbcAMP-arrested CEO was blocked by bisindolylmaleimide I (BIM-I), an inhibitor of PKC, implicating PKC in FSH action. EGF-stimulated CEO failed to resume maturation in the presence of glycerrhetinic acid, a gap junction inhibitor, suggesting transfer of positive signal through the cell-cell coupling pathway. These data support the idea that EGF-like peptides provide a common pathway mediating the meiosis-inducing influence of FSH, cAMP pulsing, and PKC activation in mouse CEO by a gap junction-dependent process.

Morphological and biochemical analysis of immature ovine oocytes vitrified with or without cumulus cells

The cryopreservation of oocytes is an open problem as a result of their structural sensitivity to the freezing process. This study examined (i) the survival and meiotic competence of ovine oocytes vitrified at the GV stage with or without cumulus cells; (ii) the viability and functional status of cumulus cells after cryopreservation; (iii) the effect of cytochalasin B treatment before vitrification; (iv) chromatin and spindle organization; (v) the maturation promoting factor (MPF) and mitogen-activated protein kinase (MAPK) activity of vitrified oocytes after in vitro maturation. Sheep oocytes were vitrified at different times during in vitro maturation (0, 2, and 6 h) with (COCs) or without cumulus cells (DOs). After warming and in vitro maturation, oocytes denuded at 0 h culture showed a significantly higher survival and meiotic maturation rate compared to the other groups. Hoechst 33342/propidium iodide double staining of COCs and microinjection of Lucifer Yellow revealed extensive cumulus cell membrane damage and reduced oocyte-cumulus cell communications after vitrification. Cytochalasin B treatment of COCs before vitrification exerted a negative effect on oocyte survival. After in vitro maturation, the number of vitrified oocytes with abnormal spindle and chromatin configuration was significantly higher compared to control oocytes, independently of the presence or absence of cumulus cells. The removal of cumulus cells combined with vitrification significantly decreased the MPF and MAPK levels. This study provides evidence that the removal of cumulus cells before vitrification enhances oocyte survival and meiotic competence, while impairing the activity of important proteins that could affect the developmental competence of oocytes.

Concentrations of monosaccharides and their amino and alcohol derivatives in human preovulatory follicular fluid

The study purpose was to compare sugar and polyol concentrations in preovulatory ovarian follicular fluid (FF) with those in the circulation. Samples of FF and peripheral venous blood were obtained after an overnight fast from 14 women attending an IVF program. High performance liquid chromatography measurements of seven polyols, two aminohexoses and four hexoses were the main outcome measures. Glucose concentrations in FF and plasma were 2781.26 +/- 205.64 and 4431.25 +/- 65.17 microM, respectively (P < 0.001). Mannose concentration in FF was 38.99 +/- 3.33 microM, significantly lower than plasma concentration (55.38 +/- 2.29 microM; P < 0.001). A concentration gradient from plasma to FF was also significant for glycerol (99.41 +/- 8.47 versus 74.32 +/- 6.54 microM; P < 0.002), galactose (31.69 +/- 1.58 versus 26.73 +/- 1.93 microM; P < 0.01) and galactosamine (11.49 +/- 0.69 versus 6.38 +/- 0.59 microM; P < 0.001). The plasma-to-FF concentration difference was greatest for glucose (1649.99 +/- 204.09 microM). There was a significant correlation between plasma and FF concentrations for galactose and glycerol. This study supports a substantial utilization of glucose by the oocyte/granulosa cells complex, and documents a significant concentration gradient from plasma to FF for glycerol, mannose, galactose and galactosamine. These plasma-FF differences may reflect both utilization of these carbohydrates by the cells of the preovulatory ovarian follicle and/or transport characteristics of these cells.