The level of vascular endothelial cell growth factor, nitric oxide, and endothelin-1 was correlated with ovarian volume or antral follicle counts: a potential predictor of pregnancy outcome in IVF

Nitrite and Nitrate Levels in Follicular Fluid From Human Oocyte Donors Are Related to Ovarian Response and Embryo Quality

Nitric oxide, a key regulatory molecule in the follicular fluid, has been suggested as a possible biomarker to predict ovarian response in stimulated cycles and the potential of the retrieved oocytes for developing high-quality embryos. Nevertheless, a consensus on whether or not nitric oxide can help in this context has not been reached. We simultaneously measured the oxidation products of nitric oxide, nitrite, and nitrate, via high-performance liquid chromatography (HPLC)-UV in follicular fluid samples from 72 oocyte donors. We found no associations of follicular fluid nitrite, nitrate, total nitric oxide, or nitrate/nitrite ratio with total or metaphase II (MII) oocyte yield. However, nitrite and nitrate levels were related to the yield of MII oocytes when this outcome was expressed as a proportion of all oocytes retrieved. The adjusted MII proportion in the lowest and highest nitrite levels were 68% (58–77%) and 79% (70–85%), respectively (p, linear trend = 0.02), whereas the adjusted MII proportion in extreme tertiles of nitrate levels were 79% (70–85%) and 68% (57–77%) (p, linear trend = 0.03). In addition, nitrate levels showed a suggestive inverse correlation with embryos with maximum or high potential of implantation (p = 0.07). These results suggest that the follicular fluid concentrations of nitrite and nitrate may be a useful tool in predicting how healthy oocyte donors respond to superovulation and the implantation potential of the embryos produced from their oocytes.

Vasomotor tone-associated factors and pregnancy outcomes of women who undergo in vitro fertilization

Vasomotor tone-associated factors play important roles in normal pregnancy, but their roles in the pregnancy outcome of women who undergo in vitro fertilization and embryo transfer (IVF-ET) remain unclear. A total of 82 infertile women who underwent successful IVF-ET were enrolled, including 18 pregnancy losses, 11 complications, and 53 normal deliveries. The serum NO and iNOS levels were significantly higher in the pregnancy loss group and significantly lower in the complication group than in the normal delivery group (p < 0.05). Significantly increased ET-1 and decreased PGI2 were found in both the pregnancy loss and complication groups compared with those in the normal delivery group (p < 0.05). NO, iNOS, and ET-1 are risk factors and PGI2 is a protective factor for pregnancy loss. ET-1 + PGI2 (AUC, 0.897; sensitivity, 90.6%; specificity, 83.3%) showed a relatively good predictive value for pregnancy loss following IVF-ET.

Description of the Follicular Fluid Cytokine and Hormone Profiles in Human Physiological Natural Cycles

PURPOSE

Exogenous gonadotrophins administration during in vitro fertilization/intracytoplasmic sperm injection (IVF/ICSI) cycles could significantly alter the endogenous follicular regulation system and could influence oocyte quality. The analysis of the follicular fluid (FF) cytokine and hormone profiles in physiological natural cycles is crucial to appreciate the role of FF milieu on follicle development. So far, the FF cytokine profile has been analyzed only in controlled ovarian stimulation cycles and in modified natural cycles. Our study defines, in physiological natural cycles, the cytokine and hormone profiles of individual FF aspirated from antral follicles.

METHODS

A total of 203 FFs obtained from 83 women with regular menstrual cycles undergoing ovarian tissue cryopreservation were analyzed: 115 FFs from Group 1 (10 to 29 years of age) and 88 FFs from Group 2 (30 to 40 years of age). In individual FF, 27 cytokines were measured with xMAP technology, and progesterone, estrone, estradiol, testosterone, androstenedione concentrations were determined by liquid chromatography-tandem mass spectrometry.

RESULTS

FF hormone profiles were not different in follicular and luteal phase, suggesting that FF hormones are regulated independently of the endogenous gonadotrophins-possibly because 74% of the punctured follicles, which were ≤6 mm, did not require cyclic pituitary function. The follicle size was influenced not only by the FF cytokine profile but also by the FF hormone profile, both of which are dependent on age.

MAIN CONCLUSIONS

In physiological natural cycles, FF hormones seems to be regulated independently of the endogenous gonadotropins. Age influences FF hormone and cytokine profiles and the compelling relationship between FF hormones and FF cytokines could influence the follicle development.

Effect of cold stress on ovarian & uterine microcirculation in rats and the role of endothelin system

BACKGROUND

Cold, an environmental factor, induces many reproductive diseases. It is known that endothelin (ET) is a potent vasoconstrictor, and cold stress can increase the expression of ET and its receptors. The cold stress rat model was developed to examine two parameters: (1) the effects of cold stress on ovarian and uterine morphology, function, and microvascular circulation and (2) possible mechanisms of ET and its receptors involved in cold stress-induced menstruation disorders.

METHODS

The rat cold stress model was prepared with an ice water bath. The estrous cycle was observed by methylene blue and hematoxylin and eosin (H&E) staining. Serum estradiol 2 (E₂), testosterone (T), progesterone (P) were detected by radioimmunoassay. Hemorheology indices were measured. The real-time blood flow of auricle and uterine surfaces was measured. Expressions of CD34 and α-SMA in ovarian and uterine tissues were detected by immunohistochemistry. ET-1 contents in serum were tested, and expressions of ET-receptor types A and B (ET-AR and ET-BR) in ovarian tissues were detected via Western blotting.

RESULTS

Cold stress extended the estrous cycle, thereby causing reproductive hormone disorder, imbalance of local endothelin/nitric oxide expression, and microcirculation disturbance. Cold-stress led to up-regulation of ET-AR expression and protein and down-regulation of ET-BR expression in rats.

CONCLUSIONS

This study suggests that the reason for cold stress-induced dysfunction in reproductive organs may be closely related to the imbalance of ET-1 and its receptor expressions, leading to microvascular circulation disorders in local tissues.

Endothelin-1 promotes human germinal vesicle-stage oocyte maturation by downregulating connexin-26 expression in cumulus cells

STUDY QUESTION

Does endothelin-1 (ET-1) promote human oocyte maturation and by what mechanism?

SUMMARY ANSWER

Addition of ET-1 to the medium in which human germinal vesicle (GV)-stage immature oocytes are cultured enhances the GV breakdown (GVBD) rate; the resumption of meiosis may be initiated by ET-1 downregulating the expression of connexin-26 (Cx26) in cumulus cells via endothelin receptor type B (ETRB), leading to decreased cAMP levels in the oocyte.

WHAT IS KNOWN ALREADY

The paracrine factor ET-1 is secreted by ovarian somatic cells in pre-ovulatory follicles and regulates oocyte maturation in mice. Connexins, or gap junction proteins, form intercellular membrane channels that play important roles in the resumption of meiosis.

STUDY DESIGN, SIZE, DURATION

This laboratory study was conducted over a 1-year period. The effects of ET-1 on meiotic resumption were evaluated in human GV-stage cumulus-oocyte complexes (COCs; 70 oocytes/group). The transcriptome profiles of ET-1-treated or untreated cumulus cells were compared to explore the possible mechanisms by which ET-1 may regulate oocyte maturation.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The ET-1, ETRA and ETRB expression levels in human cumulus cells from oocytes at different stages of maturation were evaluated using real-time quantitative PCR. Human GV-stage COCs collected from patients undergoing IVF at a university-affiliated infertility centre were cultured with or without ET-1, and cumulus cells were subsequently denuded using hyaluronidase and cultured in α-MEM. A GeneChip® Human Transcriptome Array was applied to explore differences in the whole-genome transcriptome profiles of cumulus cells treated with or without ET-1. Real-time quantitative PCR and Western blotting were used respectively to examine Cx26 mRNA and protein levels in cumulus cells. Changes in cAMP levels in both oocytes and cumulus cells after ET-1 treatment were measured using an enzyme-linked immunosorbent assay.

MAIN RESULTS AND THE ROLE OF CHANCE

Cumulus cells from MII-stage oocytes exhibited upregulated ET-1 expression, compared to those from GV-stage oocytes. The addition of ET-1 to the culture medium enhanced the GVBD rate of cumulus cell-enclosed human oocytes. Whole-genome transcriptome microarray analyses revealed significantly downregulated Cx26 expression in cumulus cells after ET-1 treatment, and this action was blocked by an ETRB antagonist. The involvement of Cx26 was further supported by the finding that ET-1 treatment led to decreased cAMP levels in oocytes but increased cAMP levels in cumulus cells.

LARGE SCALE DATA

Microarray data are published in the GEO database (GSE97684).

LIMITATIONS, REASONS FOR CAUTION

The heterogeneity of human COCs collected from patients undergoing IVF might affect the maturation results in vitro. Although we focused on the effects of ET-1 on human oocyte maturation in the present study, mammalian oocyte maturation is a complicated process involving many endocrine and paracrine factors.

WIDER IMPLICATIONS OF THE FINDINGS

Our present study suggests that in vitro, human GV-stage oocyte maturation could be enhanced by adding ET-1 to the culture medium. In the present study, we explored the molecular mechanisms by which ET-1 initiates the resumption of meiosis and demonstrated that ET-1 promotes oocyte maturation by downregulating the expression of the gap junction protein Cx26 in cumulus cells. These results expand our understanding of the molecular mechanisms underlying mammalian oocyte maturation and provide a basis for better in-vitro maturation strategies.

STUDY FUNDING AND COMPETING INTERESTS

This work was supported by grants from the China Natural Science Foundation (Grant Nos. 81170567 and 81370761). The authors declare that they have no conflicts of interest associated with this manuscript.

Ovarian Fibrosis: A Phenomenon of Concern

Objective:

Ovarian fibrosis is characterized by excessive proliferation of ovarian fibroblasts and deposition of extracellular matrix (ECM) and it is one of the principal reasons for ovarian dysfunction. This review aimed to investigate the pathogenetic mechanism of ovarian fibrosis and to clarify the relationship between ovarian diseases and fibrosis.

Data Sources:

We searched PubMed for English language articles published up to November 2016. The search terms included ovarian fibrosis OR fibrosis, ovarian chocolate cyst OR ovarian endometrioma, polycystic ovarian syndrome (PCOS), premature ovarian failure, ECM, matrix metalloproteinases (MMPs), tissue inhibitors of matrix metalloproteinases (TIMPs), transforming growth factor-beta 1 (TGF-β1), connective tissue growth factor (CTGF), peroxisome proliferator-activated receptor gamma (PPAR-γ), vascular endothelial growth factor (VEGF), endothelin-1 (ET-1), and combinations of these terms.

Study Selection:

Articles were obtained and reviewed to analyze the pathogenic mechanism of ovarian fibrosis and related ovarian diseases.

Results:

Many cytokines, such as MMPs, TIMPs, TGF-β1, CTGF, PPAR-γ, VEGF, and ET-1, are involved in ovarian fibrogenesis. Ovarian fibrogenesis is associated with various ovarian diseases, including ovarian chocolate cyst, PCOS, and premature ovarian failure. One finding of particular interest is that fibrogenesis in peripheral tissues around an ovarian chocolate cyst commonly causes ovarian function diminution, and therefore, this medical problem should arouse widespread concern in clinicians worldwide.

Conclusions:

Patients with ovarian fibrosis are susceptible to infertility and tend to have decreased responses to assisted fertility treatment. Thus, protection of ovarian function should be a priority for women who wish to reproduce when making therapeutic decisions about ovarian fibrosis-related diseases.

The balance of proangiogenic and antiangiogenic VEGFA isoforms regulate follicle development

Vascular endothelial growth factor A (VEGFA) has been extensively studied because of its role in follicular development and is a principal angiogenic factor essential for angiogenesis. Since vascularization of the theca layer increases as follicles progress in size through preantral and antral stages, VEGFA might influence follicle growth via the regulation of angiogenesis. However, VEGFA might also influence follicular development through nonangiogenic mechanisms, since its expression has been localized in nonvascular follicles and cells. Alternative mRNA splicing of eight exons from the VEGFA gene results in the formation of various VEGFA isoforms. Each isoform has unique properties and is identified by the number of amino acids within the mature protein. Proangiogenic isoforms (VEGFA_XXX) are encoded by exon 8a, whereas a sister set of isoforms (VEGFA_XXXB) with antiangiogenic properties is encoded by exon 8b. The antiangiogenic VEGFA_XXXB isoforms comprise the majority of VEGFA expressed in most tissues, whereas expression of the proangiogenic VEGFA isoforms is upregulated in tissues undergoing active angiogenesis. Although proangiogenic and antiangiogenic isoforms can now be distinguished from one another, many studies evaluating VEGFA in ovarian and follicular development up to now have not differentiated proangiogenic VEGFA from antiangiogenic VEGFA. Experiments from our laboratory indicate that proangiogenic VEGFA promotes follicle recruitment and early follicular development and antiangiogenic VEGFA inhibits these processes. The balance of proangiogenic versus antiangiognic VEGFA isoforms is thus of importance during follicle development. Further studies are warranted to elucidate the way that this balance regulates follicular formation and progression.

Research resource: interactome of human embryo implantation: identification of gene expression pathways, regulation, and integrated regulatory networks

A prerequisite for successful embryo implantation is adequate preparation of receptive endometrium and the establishment and maintenance of a viable embryo. The success of implantation further relies upon a two-way dialogue between the embryo and uterus. However, molecular bases of these preimplantation and implantation processes in humans are not well known. We performed genome expression analyses of human embryos (n = 128) and human endometria (n = 8). We integrated these data with protein-protein interactions in order to identify molecular networks within the endometrium and the embryo, and potential embryo-endometrium interactions at the time of implantation. For that, we applied a novel network profiling algorithm HyperModules, which combines topological module identification and functional enrichment analysis. We found a major wave of transcriptional down-regulation in preimplantation embryos. In receptive-stage endometrium, several genes and signaling pathways were identified, including JAK-STAT signaling and inflammatory pathways. The main curated embryo-endometrium interaction network highlighted the importance of cell adhesion molecules in the implantation process. We also identified cytokine-cytokine receptor interactions involved in implantation, where osteopontin (SPP1), leukemia inhibitory factor (LIF) and leptin (LEP) pathways were intertwining. Further, we identified a number of novel players in human embryo-endometrium interactions, such as apolipoprotein D (APOD), endothelin 1 (END1), fibroblast growth factor 7 (FGF7), gastrin (GAST), kringle containing trnasmembrane protein 1 (KREMEN1), neuropilin 1 (NRP1), serpin peptidase inhibitor clade A member 3 (SERPINA3), versican (VCAN), and others. Our findings provide a fundamental resource for better understanding of the genetic network that leads to successful embryo implantation. We demonstrate the first systems biology approach into the complex molecular network of the implantation process in humans.