Prostaglandin synthesis by cumulus-oocyte complexes: effects on in vitro fertilization in mice

Exposure to Cumulus Cell Secretome Improves Sperm Function: New Perspectives for Sperm Selection In Vitro

In the literature, there is a well-known correlation between poor semen quality and DNA sperm integrity, which can turn into negative outcomes in terms of embryo development and clinical pregnancy. Sperm selection plays a pivotal role in clinical practice, and the most widely used methods are mainly based on sperm motility and morphology. The cumulus oophorus complex (COC) during natural fertilization represents a barrier that spermatozoa must overcome to reach the zona pellucida and fertilize the oocyte. Spermatozoa that can pass through the COC have better structural and metabolic characteristics as well as enhanced acrosome reaction (AR). The present study aimed to evaluate the exposure of sperm to cumulus cell secretome during swim-up treatment (SUC) compared with the routinely used swim-up method (SU). To determine the effectiveness of this method, biological factors critical for the ability of sperm to fertilize an oocyte, including capacitation, AR, tyrosine phosphorylation signature, DNA integrity, and mitochondrial functionality, were assessed. The SUC selection assures recovery of high-quality spermatozoa, with enhanced mitochondrial functionality and motility compared with both SU-selected and unselected (U) sperm. Furthermore, using this modified swim-up procedure, significantly reduced sperm DNA damage (p < 0.05) was detected. In conclusion, the SUC approach is a more physiological and integrated method for sperm selection that deserves further investigation for its translation into clinical practice.

Elevated and Sustained Intracellular Calcium Signalling Is Necessary for Efficacious Induction of the Human Sperm Acrosome Reaction

Progesterone and prostaglandin E1 are postulated to trigger the human sperm acrosome reaction (AR). However, their reported efficacy is very variable which likely, in part, reflects the plethora of experimental conditions and methodologies used to detect this physiologically relevant event. The purpose of this study was to develop an assay for the robust induction and objective measurement of the complete AR. Sperm from healthy volunteers or patients undertaking IVF were treated with a variety of ligands (progesterone, prostaglandin E1 or NH4Cl, alone or in combinations). AR, motility and intracellular calcium measurements were measured using flow cytometry, computer-assisted sperm analysis (CASA) and fluorimetry, respectively. The AR was significantly increased by the simultaneous application of progesterone, prostaglandin E1 and NH4Cl, following an elevated and sustained intracellular calcium concentration. However, we observed notable inter- and intra-donor sample heterogeneity of the AR induction. When studying the patient samples, we found no relationship between the IVF fertilization rate and the AR. We conclude that progesterone and prostaglandin E1 alone do not significantly increase the percentage of live acrosome-reacted sperm. This assay has utility for drug discovery and sperm toxicology studies but is not predictive for IVF success.

The Function of Cumulus Cells in Oocyte Growth and Maturation and in Subsequent Ovulation and Fertilization

Cumulus cells (CCs) originating from undifferentiated granulosa cells (GCs) differentiate in mural granulosa cells (MGCs) and CCs during antrum formation in the follicle by the distribution of location. CCs are supporting cells of the oocyte that protect the oocyte from the microenvironment, which helps oocyte growth and maturation in the follicles. Bi-directional communications between an oocyte and CCs are necessary for the oocyte for the acquisition of maturation and early embryonic developmental competence following fertilization. Follicle-stimulation hormone (FSH) and luteinizing hormone (LH) surges lead to the synthesis of an extracellular matrix in CCs, and CCs undergo expansion to assist meiotic resumption of the oocyte. The function of CCs is involved in the completion of oocyte meiotic maturation and ovulation, fertilization, and subsequent early embryo development. Therefore, understanding the function of CCs during follicular development may be helpful for predicting oocyte quality and subsequent embryonic development competence, as well as pregnancy outcomes in the field of reproductive medicine and assisted reproductive technology (ART) for infertility treatment.

Metabolites involved in cellular communication among human cumulus-oocyte-complex and sperm during in vitro fertilization

BACKGROUND

Fertilization is a key physiological process for the preservation of the species. Consequently, different mechanisms affecting the sperm and the oocyte have been developed to ensure a successful fertilization. Thus, sperm acrosome reaction is necessary for the egg coat penetration and sperm-oolema fusion. Several molecules are able to induce the sperm acrosome reaction; however, this process should be produced coordinately in time and in the space to allow the success of fertilization between gametes. The goal of this study was to analyze the metabolites secreted by cumulus-oocyte-complex (COC) to find out new components that could contribute to the induction of the human sperm acrosome reaction and other physiological processes at the time of gamete interaction and fertilization.

METHODS

For the metabolomic analysis, eighteen aliquots of medium were used in each group, containing: a) only COC before insemination and after 3 h of incubation; b) COC and capacitated spermatozoa after insemination and incubated for 16-20 hours; c) only capacitated sperm after 16-20 h in culture and d) only fertilization medium as control. Six patients undergoing assisted reproduction whose male partners provided normozoospermic samples were included in the study. Seventy-two COC were inseminated.

RESULTS

The metabolites identified were monoacylglycerol (MAG), lysophosphatidylcholine (LPC) and phytosphingosine (PHS). Analysis by PCR and in silico of the gene expression strongly suggests that the cumulus cells contribute to the formation of the PHS and LPC.

CONCLUSIONS

LPC and PHS are secreted by cumulus cells during in vitro fertilization and they could be involved in the induction of human acrosome reaction (AR). The identification of new molecules with a paracrine effect on oocytes, cumulus cells and spermatozoa will provide a better understanding of gamete interaction.

Impact of ketorolac administration around ovarian stimulation on in vivo and in vitro fertilization and subsequent embryo development

We performed this study to investigate the effect of ketorolac (a non-steroidal anti-inflammatory drug) administration around ovarian stimulation on in vivo and in vitro fertilization process. Sixty-four female mice (ICR) were injected with ketorolac (0, 7.5, 15 and 30 µg/d) for 3 d starting from the day of eCG treatment. In experiment 1, 41 mice were triggered by hCG and then mated; two-cell embryos were obtained and in vitro development up to blastocyst was observed. In experiment 2, 23 mice were triggered by hCG and mature oocytes were collected; in vitro fertilization rate and subsequent embryo development up to blastocyst was recorded. In experiment 1, the blastocyst-forming rates per in vivo fertilized two-cell embryo showed an inverse relationship with a dosage of ketorolac (97.6%, 64.2%, 35.4% and 25.9%). In experiment 2, degenerated oocytes were frequently observed in a dose-dependent manner (4.3%, 22.9%, 22.4% and 75.0%). Lower fertilization rates were noted in all the three ketorolac-treating groups; blastocyst-forming rate was significantly lower in 30-µg-treating group when compared with the control group. Administration of ketorolac around ovarian stimulation significantly affects the development of in vivo fertilized embryo in a dose-dependent manner. High-dose ketorolac could result in a poor oocyte quality and decreased embryo developmental competence.

Maturation and fertilization of nonhuman primate oocytes are compromised by oral administration of a cyclooxygenase-2 inhibitor

OBJECTIVE

To determine if oral administration of a cyclooxygenase-2 (COX2) inhibitor affects oocyte nuclear maturation and fertilization in nonhuman primates.

DESIGN

Laboratory research study.

SETTING

Medical school.

ANIMAL(S)

Adult female cynomolgus monkeys (Macaca fascicularis).

INTERVENTION(S)

Monkeys received gonadotropins to stimulate multiple follicular development. An ovulatory dose of hCG was administered either alone or with oral celecoxib, a COX2 inhibitor. Oocytes were retrieved 36 hours later and exposed to sperm in vitro.

MAIN OUTCOME MEASURE(S)

Oocytes were assessed for nuclear status at retrieval, resumption of meiosis in vitro, and success of in vitro fertilization.

RESULT(S)

Treatment with hCG alone yielded oocytes that were primarily (72.9%) at the meiosis II (MII) stage of nuclear maturation; few oocytes were obtained at the germinal vesicle and germinal vesicle breakdown stages. Treatment with hCG and celecoxib yielded fewer mature (MII) oocytes (35.6%) and more oocytes at less mature stages compared with oocytes from monkeys treated with hCG alone. The majority (68.3 ± 15.9%) of MII oocytes from monkeys treated with hCG alone fertilized in vitro, compared with only 11.0 ± 5.9% of MII oocytes from monkeys treated with hCG and celecoxib.

CONCLUSION(S)

Oral administration of a COX2 inhibitor reduced the rate of oocyte nuclear maturation and the success of in vitro fertilization. Drugs of this class may block multiple essential steps in female reproduction and be effective contraceptives for women.

PACAP-mediated sperm-cumulus cell interaction promotes fertilization

The developing acrosome in spermatids contains pituitary adenylate cyclase-activating polypeptide (PACAP). However, the role of the acrosomal PACAP remains unclear because it has not been detected in mature spermatids and sperm. We reinvestigated whether the sperm acrosome contains PACAP. An antiserum produced against PACAP reacted to the anterior acrosome in epididymal sperm fixed under mild conditions, suggesting that PACAP acts on oocytes and/or cumulus cells at the site of fertilization. Immunolabeling and RT-PCR demonstrated the presence of PACAP type I receptor, a PACAP-specific receptor, in postovulatory cumulus cells. To investigate the role of PACAP in fertilization, we pretreated cumulus-oocyte complexes with the polypeptide. At a low concentration of sperm, the fertilization rate was significantly enhanced by PACAP in a dose-dependent manner. Sperm penetration through the oocyte investment, cumulus layer, and zona pellucida was also enhanced by PACAP. The enhancement was probably due to an enhancement in sperm motility and the zona-induced acrosome reaction, which were stimulated by a cumulus cell-releasing factor. Indeed, PACAP treatment increased the secretion of progesterone from the cumulus-oocyte complexes. These results strongly suggest that in response to PACAP, cumulus cells release a soluble factor that probably stimulates sperm motility and the acrosome reaction, thereby promoting fertilization.

The effect of linolenic Acid on bovine oocyte maturation and development

Dietary polyunsaturated fatty acids can influence reproductive performance. In dairy cattle, some high-fat diets resulted in higher blastocyst rates and improved embryo quality. These effects may partly be mediated by a direct action of fatty acids on oocyte development. The present study investigated the effect of linolenic acid (ALA; 18:3 n-3) supplementation on bovine oocyte maturation and early embryo development in vitro. Treatment of cumulus-oocyte complexes (COCs) with 50 muM ALA significantly increased the percentage of oocytes at the metaphase II (MII) stage compared with untreated controls (95% +/- 2% vs. 84% +/- 2%, respectively). Higher doses of ALA were detrimental. Treatment of COCs with 50 muM ALA compared with controls also resulted in a significantly higher percentage of cleaved embryos (77% +/- 9% vs. 69% +/- 9%, respectively) and blastocyst rate (36% +/- 4% vs. 23% +/- 5%, respectively) and better-quality embryos. Furthermore, COCs treated with ALA had significant increases compared with controls in: 1) prostaglandin E(2) (PGE(2)) concentration (233% +/- 41%) in the medium, 2) intracellular cAMP at 3 h of maturation, and 3) phosphorylation of the mitogen-activated protein kinases (MAPKs) during the first 6 h of maturation. Moreover, ALA overcame the suppressive effects of the prostaglandin-endoperoxide synthase 2 inhibitor (NS-398) on oocyte maturation and partially improved the maturation rate in the presence of the MAPK kinase inhibitor (U-0126). Linolenic acid could not, however, recover maturation in the presence of both inhibitors. In conclusion, treatment of bovine COCs with ALA during oocyte maturation affects the molecular mechanisms controlling oocyte nuclear maturation, leading to an increased number of MII-stage oocytes and improved subsequent early embryo development. This effect is mediated both directly through MAPK pathway and indirectly through PGE(2) synthesis.

Effect of a selective nonsteroidal anti-inflammatory drug, celecoxib, on the reproductive function of female mice

BACKGROUND

The aim of the present study was to determine if long-term use of a cyclooxygenase-2 (COX-2) inhibitor affects fertility or ovulation in female mice.

METHODS

Twenty-four female mice, 25 days of age, were given a selective COX-2 inhibitor: 3 mg/kg celecoxib (n = 8), 5 mg/kg celecoxib (n = 8),or placebo (n = 8) in a random fashion. Eight female mice, 10-11 weeks old, given 3 mg/kg celecoxib (n = 4) or placebo (n = 4) were subjected to continuous mating studies.

RESULTS

Results from the 24 mice (n = 8 for each group) showed that oocyte number was not significantly different between female mice treated with either 3 mg/kg or 5 mg/kg celecoxib and placebo (21.4 +/- 2.5, 21.5 +/- 3.3, 23.3 +/- 3.8, respectively). From the continuous mating study, the litter size of female mice treated with celecoxib was not significantly different (8.2 +/- 1.3 pups/litter) compared to those treated with placebo (8.3 +/- 1.2 pups/litter). In addition, female mice treated with celecoxib had an average of 2.8 +/- 0.5 litters in a 12-week period, which was similar to female mice treated with placebo (3.0 +/- 0.8 litters/female).

CONCLUSION

This study suggests that use of low-dose (<or= 5 mg/kg) selective COX-2 inhibitor in a mouse model does not significantly impair the female reproductive function.

Rescue of Female Infertility from the Loss of Cyclooxygenase-2 by Compensatory Up-regulation of Cyclooxygenase-1 Is a Function of Genetic Makeup

Cyclooxygenase-2 (COX-2), an inducible rate-limiting enzyme in prostaglandin biosynthesis, is implicated in various physiological and pathological processes including female fertility, renal function, angiogenesis, inflammation, and tumorigenesis. We showed previously that targeted deletion of Ptgs2 encoding COX-2, but not Ptgs1 encoding COX-1, in C57BL/6J/129 mice produces complete female infertility resulting from multiple reproductive failures spanning ovulation, fertilization, and implantation. Here we show that Ptgs2 null mice on a CD1 background have dramatically improved female fertility including ovulation, fertilization, and implantation, giving rise to live births. We provide evidence that this improved fertility in CD1 Ptgs2 null mice is the result of a compensatory up-regulation of Ptgs1 which does not occur in C57BL/6J/129 mice missing Ptgs2. These results clearly demonstrate for the first time that COX-1 can replace specific functions of COX-2 in vivo in the context of genetic disparity. In light of this finding, the therapeutic use and efficacy of COX-2-specific inhibitors among human populations without regard for genetic and ethnic diversities should be revisited.

Expression of messenger RNA for prostaglandin E receptor subtypes EP4/EP2 and cyclooxygenase isozymes in mouse periovulatory follicles and oviducts during superovulation

Prostaglandin (PG) E(2) is synthesized from arachidonic acid by cyclooxygenase (COX) and acts as a regulator in ovulation and fertilization reactions. We present the temporal and regional expression patterns of mRNAs for the two Gs-coupled PGE receptors, EP2 and EP4, and for COX-1 and COX-2 in mouse periovulatory follicles and oviducts during superovulation. Analysis using reverse transcription polymerase chain reaction revealed that the mouse ovaries express a significant amount of EP4 mRNA in addition to EP2 mRNA during superovulation. In situ hybridization results revealed that the signals for EP4 mRNA were localized mostly to oocytes in the preantral follicles. Three hours after hCG injection, the signals for EP4 and EP2 mRNA were present in both granulosa and cumulus cells. However, 9 h after hCG injection, just before ovulation, the signals for EP4 mRNA were still detectable in both cell types, whereas those for EP2 mRNA were found only in cumulus cells. COX-2 mRNA expression was present in both granulosa and cumulus cells at 3 h but was present only in cumulus cells at 9 h. COX-1 mRNA expression was not found in granulosa cells at 3 h but was found in these cells at 9 h. In the oviduct, the expression of EP4 and COX-1 mRNA was localized to epithelial cells, whereas expression of EP2 mRNA was localized to the smooth muscle layer. The tightly regulated expression of both EP2 and EP4 in the preovulatory follicles may reflect the essential role of PGE(2) in the ovulation process.

Growth differentiation factor-9 stimulates progesterone synthesis in granulosa cells via a prostaglandin E2/EP2 receptor pathway

Growth differentiation factor-9 (GDF-9), an oocyte-secreted member of the transforming growth factor beta superfamily, progesterone receptor, cyclooxygenase 2 (Cox2; Ptgs2), and the EP2 prostaglandin E(2) (PGE(2)) receptor (EP2; Ptgerep2) are required for fertility in female but not male mice. To define the interrelationship of these factors, we used a preovulatory granulosa cell culture system in which we added recombinant GDF-9, prostaglandins, prostaglandin receptor agonists, or cyclooxygenase inhibitors. GDF-9 stimulated Cox2 mRNA within 2 h, and PGE(2) within 6 h; however, progesterone was not increased until 12 h after addition of GDF-9. This suggested that Cox2 is a direct downstream target of GDF-9 but that progesterone synthesis required an intermediate. To determine whether prostaglandin synthesis was required for progesterone production, we analyzed the effects of PGE(2) and cyclooxygenase inhibitors on this process. PGE(2) can stimulate progesterone synthesis by itself, although less effectively than GDF-9 (3-fold vs. 6-fold increase over 24 h, respectively). Furthermore, indomethacin or NS-398, inhibitors of Cox2, block basal and GDF-9-stimulated progesterone synthesis. However, addition of PGE(2) to cultures containing both GDF-9 and NS-398 overrides the NS-398 block in progesterone synthesis. To further define the PGE(2)-dependent pathway, we show that butaprost, a specific EP2 agonist, stimulates progesterone synthesis and overrides the NS-398 block. In addition, GDF-9 stimulates EP2 mRNA synthesis by a prostaglandin- and progesterone-independent pathway. Thus, GDF-9 induces an EP2 signal transduction pathway which appears to be required for progesterone synthesis in cumulus granulosa cells. These studies further demonstrate the importance of oocyte-somatic cell interactions in female reproduction.

Mouse oocyte quality and prostaglandin synthesis by cumulus oocyte complex after moderate chronic ethanol intake

Chronic ingestion of ethanol produces a variety of effects on female reproductive function, depending on the dose and the exposure time but the mechanism of alcohol-induced ovarian failure has been little studied. Also the effects of chronic ethanol consumption on the oocyte quality in relation to morphological alterations and PGE synthesis by the oocyte cumulus complexes (OCCs) have not been described. In this study, immature female mice were treated with 10% ethanol in drinking water for 30 days. Then they were induced to superovulate, and at 14, 16 and 20 h post-hCG the quality of the ovarian and oviductal oocytes and PGE production by OCC was determined. At 14 h post-hCG, the percentage of oviductal immature oocytes was increased in the ethanol-treated females (P < 0.05). At 16 h post-hCG, the percent of oviductal activated oocytes was higher in the treated females (P < 0.05), and the ovarian immature oocytes were decreased as compared to the control females (P < 0.05). At 20 h post-hCG, the ethanol-treated females had higher percents of activated oocytes in the oviducts and in the ovaries (P < 0.05) with respect to the controls. PGE synthesis by OCCs, assessed by RIA, was decreased in the treated female mice (P < 0.001). In summary, moderate chronic ethanol treatment in immature female mice can produce morphologic abnormalities in the oocytes (high parthenogenetic activated rates) and altered PGE production in the OCCs.

Altered prostanoid production by cumulus-oocyte complexes in a rat model of non-insulin-dependent diabetes mellitus

Ovulation, oocyte maturation and PGE and PGF2 alpha production by oocyte-cumulus complexes were evaluated in rats with non-insulin-dependent diabetes induced by neonatal streptozotocin. Diabetic rats had normal estrous cycles, but ovulated a lower number of oocytes at estrus. When oocytes from control and diabetic rats obtained at proestrus were matured "in vitro" during 1, 2 or 4 hours (hr) of culture, differences were not found in the percent of germinal vesicle breakdown between both experimental groups. PGE and PGF2 alpha accumulation was higher in ovulated oocyte-cumulus complexes when compared to immature or "in vitro"-matured oocyte-cumulus complexes in both normal and diabetic rats. When control and diabetic rats are compared, more PGE and PGF2 alpha accumulation was observed in immature, "in vitro"-matured and in ovulated oocyte-cumulus complexes. A lower number of oocytes ovulated and increased oocyte-cumulus complexes prostaglandin production has been observed in this mildly diabetic experimental model. These abnormalities are similar to those previously found when 10 day embryos were evaluated in non-insulin-dependent diabetic rats.