Human follicular nitric oxide pathway: relationship to follicular size, oestradiol concentrations and ovarian blood flow

Hemodynamic, endocrine, and gene expression mechanisms regulating equine ovarian follicular and cellular development

Ovulatory follicle development and associated oocyte maturation involve complex coordinated molecular and cellular mechanisms not yet fully understood. This study addresses the relationships among follicle diameter, follicle wall blood flow, follicular-fluid factors, and gene expression for follicle growth, steroidogenesis, angiogenesis, and apoptosis in granulosa/cumulus cells and oocytes during different stages from the beginning of largest/ovulatory follicle to impending ovulation in mares. The most remarkable findings were (i) a positive association between follicle development, follicle blood flow, intrafollicular follicle-stimulating hormone (FSH), luteinizing hormone (LH), estradiol, progesterone, and messenger RNA (mRNA) expression for FSHR and LHCGR in granulosa cells of the largest/ovulatory follicle; (ii) a plateau or decrease in follicle diameter and blood flow and granulosa cell mRNA for FSHR, LHCGR, IGF1R, VEGFR2, CYP19A1, and CASP3 at the preovulatory stage; (iii) higher StAR and BCL2 and lower CASP3 mRNA in granulosa cells at the time of impending ovulation; (iv) greater IGF1R mRNA for granulosa cells at the predeviation stage; and (v) lower FSHR, LHCGR, IGF1R, and VEGFR2 mRNA in cumulus cells and greater LHCGR and IGF1R mRNA in oocytes at the ovulatory stage. This study is a critical advance in the understanding of molecular mechanisms of follicle development and oocyte maturation and is expected to be vital for future studies targeting potential markers.

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.

Hypoxia-inducible factor-1alpha and nitric oxide synthases in bovine follicles close to ovulation and early luteal angiogenesis

The objective of the study was to characterize expression patterns of hypoxia-inducible factor-1alpha (HIF1A), inducible nitric oxide synthase (iNOS) and endothelial (eNOS) isoforms in time-defined follicle classes before and after GnRH application in the cow. Ovaries containing pre-ovulatory follicles or corpora lutea were collected by transvaginal ovariectomy (n = 5 cows/group) as follow: (I) before GnRH administration; (II) 4h after GnRH; (III) 10h after GnRH; (IV) 20h after GnRH; (V) 25h after GnRH; and (VI) 60h after GnRH (early corpus luteum). The mRNA abundance of HIF1A in the follicle group before GnRH was high, followed by a significant down regulation afterwards with a minimum level 25h after GnRH (close to ovulation) and significant increase only after ovulation. The mRNA abundance of iNOS before GnRH was high, decreased significantly during LH surge, with minimum levels afterwards. In contrast, the mRNA of eNOS decreased in the follicle group 20h after GnRH, followed by a rapid and significant upregulation just after ovulation. Immunohistochemically, the granulosa cells of antral follicles and the eosinophils of the theca tissue as well of the early corpus luteum showed a strong staining for HIF1A. The location of the eosinophils could be clearly demonstrated by immunostaining with an eosinophil-specific antibody (EMBP) and transmission electron microscopy. In conclusion, the parallel and acute regulated expression patterns of HIF1A and NOS isoforms, specifically during the interval between the LH surge and ovulation, indicate that these paracrine factors are involved in the local mechanisms, regulating final follicle maturation, ovulation and early luteal angiogenesis.

Ovarian stimulated cycles reduce protection of follicular fluid against free radicals

Controlled ovarian hyperstimulation cycle with exogenous gonadotropins (COH) is associated with clinical complications. The aim of this work was to determine whether COH alters the physiological antioxidant status of follicular fluid in women with no reproductive dysfunction, compared to the natural cycle (NC). In this longitudinal study, forty-one women (oocyte donors) consecutively underwent NC and COH. Follicular fluid was collected at oocyte retrieval and different redox biomarkers were determined: total antioxidant activity (TAA), oxygen radical absorbance capacity (ORAC), nitric oxide, α- and γ-tocopherol, the fatty acid composition, activities of superoxide dismutase, catalase, total and Se-dependent glutathione peroxidases, and the antioxidant paraoxonase (PON) family. Results showed that TAA (1.70 ± 0.03 mM versus 1.86 ± 0.03 mM, p < 0.05), α-tocopherol (4.37 ± 0.26 μM versus 5.74 ± 0.30 μM, p < 0.05), PON1 paraoxonase (245 ± 24 nmol/min/ml versus 272 ± 27 nmol/min/ml, p < 0.05), PON1 arylesterase (87.2 ± 4.6 μmol/min/ml versus 99.3 ± 4.8 μmol/min/ml, p < 0.05), and PON3 simvastatinase (13.48 ± 0.52 nmol/min/ml versus 16.29 ± 0.72 nmol/min/ml, p < 0.001) were significantly lower in COH versus NC. Fatty acids from COH were more saturated, increasing palmitate and decreasing the n-6 and total polyunsaturated fatty acids (PUFAs). Docosahexaenoic acid also increased (p < 0.05). Results suggest that COH could lead to premature ovarian aging and provide new insights into the possible prevention of the adverse effects of ovarian hyperstimulation by directing therapeutic applications to the maintenance of the redox balance and fatty acid status, with special attention to paraoxonase proteins and docosahexaenoic acid.

Ovulation: Parallels With Inflammatory Processes

The midcycle surge of LH sets in motion interconnected networks of signaling cascades to bring about rupture of the follicle and release of the oocyte during ovulation. Many mediators of these LH-induced signaling cascades are associated with inflammation, leading to the postulate that ovulation is similar to an inflammatory response. First responders to the LH surge are granulosa and theca cells, which produce steroids, prostaglandins, chemokines, and cytokines, which are also mediators of inflammatory processes. These mediators, in turn, activate both nonimmune ovarian cells as well as resident immune cells within the ovary; additional immune cells are also attracted to the ovary. Collectively, these cells regulate proteolytic pathways to reorganize the follicular stroma, disrupt the granulosa cell basal lamina, and facilitate invasion of vascular endothelial cells. LH-induced mediators initiate cumulus expansion and cumulus oocyte complex detachment, whereas the follicular apex undergoes extensive extracellular matrix remodeling and a loss of the surface epithelium. The remainder of the follicle undergoes rapid angiogenesis and functional differentiation of granulosa and theca cells. Ultimately, these functional and structural changes culminate in follicular rupture and oocyte release. Throughout the ovulatory process, the importance of inflammatory responses is highlighted by the commonalities and similarities between many of these events associated with ovulation and inflammation. However, ovulation includes processes that are distinct from inflammation, such as regulation of steroid action, oocyte maturation, and the eventual release of the oocyte. This review focuses on the commonalities between inflammatory responses and the process of ovulation.

Reproductive endocrinology of environmental nitrate

Nitrate is a widespread contaminant of aquatic ecosystems and drinking water. It is also broadly active in organismal physiology, and as such, has the potential to both enhance and disrupt normal physiological function. In animals, nitrate is a proposed endocrine disrupter that is converted in vivo to nitrite and nitric oxide. Nitric oxide, in particular, is a potent cell signaling molecule that participates in diverse biological pathways and events. Here, we review in vivo nitrate cycling and downstream mechanistic physiology, with an emphasis on reproductive outcomes. However, in many cases, the research produces contradictory results, in part because there is good evidence that nitrate follows a non-monotonic dose-response curve. This conundrum highlights an array of opportunities for scientists from different fields to collaborate for a full understanding of nitrate physiology. Opposing conclusions are especially likely when in vivo/in vitro, long term/short term, high dose/low dose, or hypoxia/normoxia studies are compared. We conclude that in vivo studies are most appropriate for testing an organism's integrated endocrine response to nitrate. Based on the limited available studies, there is a generalized trend that shorter term studies (less than 1 month) or studies involving low doses (≤5 mg/L NO₃-N) cause steroid hormone levels to decline. Studies that last more than a month and/or involve higher, but still environmentally relevant, exposures (>50-100 mg/L NO₃-N) cause steroid hormone levels to increase. Very high nitrate doses (>500 mg/L NO₃-N) are cytotoxic in many species. Hypoxia and acidity are likely to intensify the effects of nitrate. For study design, degree of study animal reproductive maturity or activity is important, with immature/reproductively quiescent animals responding to nitrate differently, compared with reproductively active animals. A detailed table of studies is presented.

Clomiphene citrate increases nitric oxide, interleukin-10 and reduces matrix metalloproteinase-9 in women with polycystic ovary syndrome

OBJECTIVES

Matrix metalloproteinase-9, Nitric oxide and inflammation plays a role in the pathogenesis of poly cystic ovary syndrome (PCOS). Even though these parameters are altered in PCOS, the effect of clomiphene citrate on them has not been studied till date. The present study was done to assess the effect of clomiphene citrate on matrix metalloproteinase-9, nitric oxide and interleukin-10 levels in women with PCOS.

STUDY DESIGN

72 women diagnosed with PCOS were enrolled in the study. Matrix metalloproteinase-9, nitric oxide and interleukin-10 levels were compared at baseline and after three weeks following Clomiphene citrate treatment.

RESULTS

Clomiphene citrate increases both nitric oxide (p = 0.03) and interleukin-10 (p < 0.001) levels and reduces matrix metalloproteinase-9 levels (p < 0.001) in women with PCOS. It also improves the ovulation rate (52.8%) and clinical pregnancy rate (19.4%) in PCOS. Also there was a significant reduction in matrix metalloproteinase-9 levels in both the ovulatory (p < 0.001) and conceived groups (p = 0.024) compared to non ovulatory and non conceived group. There was no difference in nitric oxide and interleukin-10 levels in ovulatory and conceived groups compared to non ovulatory and non conceived group.

CONCLUSION

We conclude that clomiphene citrate increases the levels of nitric oxide and interleukin-10 and decreases the matrix metalloproteinase - 9 levels and improves the ovulation rate and clinical pregnancy rate in PCOS.

Protein pathways working in human follicular fluid: the future for tailored IVF?

The human follicular fluid (HFF) contains molecules and proteins that may affect follicle growth, oocyte maturation and competence acquiring. Despite the numerous studies, an integrated broad overview on biomolecular and patho/physiological processes that are proved or supposed to take place in HFF during folliculogenesis and oocyte development is still missing. In this review we report, for the first time, all the proteins unambiguously detected in HFF and, applying DAVID (Database for Annotation, Visualization and Integrated Discovery) and MetaCore bioinformatic resources, we shed new lights on their functional correlation, delineating protein patterns and pathways with reasonable potentialities for oocyte quality estimation in in vitro fertilisation (IVF) programs. Performing a rigorous PubMed search, we redacted a list of 617 unique proteins unambiguously-annotated as HFF components. Their functional processing suggested the occurrence in HFF of a tight and highly dynamic functional-network, which is balanced by specific effectors, primarily involved in extracellular matrix degradation and remodelling, inflammation and coagulation. Metalloproteinases, thrombin and vitamin-D-receptor/retinoid-X-receptor-alpha resulted as the main key factors in the nets and their differential activity may be indicative of ovarian health and oocyte quality. Despite future accurate clinical investigations are absolutely needed, the present analysis may provide a starting point for more accurate oocyte quality estimation and for defining personalised therapies in reproductive medicine.

Immunolocalization of nitric oxide synthase (NOS) isoforms in ovarian follicles of the catfish, Clarias batrachus and its relation with ovarian activity

Nitric oxide, a gaseous molecule, is produced during the conversion of arginine to citrulline by the action of NOS isoforms (eNOS, iNOS or nNOS). Role of NO in regulation of mammalian reproduction is well established; however, practically no report is available on fishes. Hence, in the present study, expression of all three isoforms of NOS was worked out in the ovary of Clarias batrachus immunohistochemically during different phases of its reproductive cycle and its relation with ovarian activities. No immunoreactivity of eNOS was observed in the ovary of C. batrachus during the late-quiescence and early-recrudescence phases. While during the recrudescence phase (April and May) it expressed intensely in thecal and granulosa cells of the oocyte-II and III, but immune-intensity decreased in the late-recrudescence and spawning phases (June and July). Similar pattern of immunoprecipitation was also observed in case of iNOS. However, the immunoreactivity pattern of nNOS was quite varied, it expressed moderately only in the nucleus and cytoplasm of perinuclear and oocyte-I stages during late-quiescence phase. While during the early recrudescence phase, the expression of nNOS disappeared completely from the nucleus and cytoplasm, rather it expressed intensely in the thecal and granulosa cells, which declined in the late-recrudescence and spawning phases. Moderate immunoreactivity of iNOS could also be localized in the zona radiata of ovulated oocyte. The intense NOS immunoreactivity in the thecal and granulosa cells coincided with increased levels of ovarian NO and 17β-estradiol content. They exhibited statistically significant positive correlation amongst themselves, suggesting the involvement of ovarian NOS/NO system in oogenesis and steroidogenesis in the catfish.

Effect of follicular fluid NO, MDA and GSH levels on in vitro fertilization outcomes

OBJECTIVE

To investigate the biochemical markers such as nitric oxide (NO), malondialdehyde (MDA) and reduced glutathione (GSH), indicators of the oxidative status of the follicle, to predict the outcome of in vitro fertilization.

MATERIAL AND METHODS

Follicular aspirates of dominant follicles were collected during oocyte retrieval. Biochemical analyses of NO, MDA and GSH were performed on all aspirates.

RESULTS

When the successful and unsuccessful pregnancy groups were compared in terms of NO, MDA and GSH, follicular fluid MDA was significantly higher (p=0.001) and follicular fluid NO level was significantly lower (p=0.039) in the pregnant group. Correlation analysis between oxidative stress and IVF parameters showed that MDA had a positive weak correlation with the number of grade 1 embryos (r=0.271, p=0.033) and fertilization rate (r=0.263, p=0.039). ROC curve analysis found that malondialdehyde has an area under the curve of 0.74 and can predict pregnancy with high sensitivity.

CONCLUSION

As malondialdehyde was significantly different in pregnant and non-pregnant women and had a good sensitivity profile in predicting pregnancy, it may be considered a marker for predicting IVF success.

A comparative study on oxidative and antioxidative markers of serum and follicular fluid in GnRH agonist and antagonist cycles

OBJECTIVE

To determine whether concentrations of oxidative stress markers of follicular fluid and serum are different in GnRH agonist protocol from GnRH antagonist protocol.

MATERIAL AND METHOD

This was a cross-sectional study. Eighty-four women undergoing controlled ovarian stimulation with either GnRH agonist (n = 39) or GnRH antagonist protocols (n = 45) for IVF/ICSI treatment were assigned by a physician. Blood was obtained at the time of oocyte retrieval, and follicular fluid (FF) from the mature follicles of each ovary was centrifuged and frozen until analysis. Malondialdehyde (MDA), nitric oxide (NO), protein carbonyl (PC), hydroxyl proline (OH-P), sodium oxide dismutase (SOD), reduced glutathione (GSH), glutathione peroxidase (GSH-Px), adenosine deaminase (ADA) and xanthine oxidase (XO) were assessed in the serum and follicular fluid of each participants.

RESULTS

The mean serum concentrations of GSH-Px, GSH and MDA were lower in the GnRH antagonist group compared to GnRH agonist group, but mean serum SOD was higher in the GnRH antagonist group. The mean follicular SOD, ADA and NO were higher in GnRH antagonist group than GnRH agonist group. The IVF/ICSI outcomes were similar in both groups.

CONCLUSION(S)

GnRH antagonist protocol is associated with increased oxidative stress. The relation of GnRH analogues with oxidative stress and its implication in follicular growth needs to be addressed in further studies.

PPAR Gamma: Coordinating Metabolic and Immune Contributions to Female Fertility

Peroxisome proliferator-activated receptor gamma (PPARG) regulates cellular functions such as adipogenesis and immune cell activation. However, new information has indicated additional roles of PPARG directing the cyclic changes that occur within ovarian tissue of female mammals, including those that facilitate the release of oocytes each estrous cycle. In addition to ovarian PPARG expression and function, many PPARG actions within adipocytes and macrophages have additional direct and indirect implications for ovarian function and female fertility. This encompasses the regulation of lipid uptake and transport, insulin sensitivity, glucose metabolism, and the regulation of inflammatory mediator synthesis and release. This review discusses the developing links between PPARG activity and female reproductive function, and highlights several mechanisms that may facilitate such a relationship.

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

The objective of this study was to investigate the correlation between the concentrations of vascular endothelial cell growth factor (VEGF), nitric oxide (NO), or endothelin-1 (ET-1) in follicular fluid with antral follicle counts (AFCs) or ovarian volume in order to predict the outcome of in vitro fertilization (IVF). One hundred and thirty-one patients were enrolled in this study, and the pregnancy rate was 37.4%. The concentration of VEGF or NO was significantly increased, while the concentration of ET-1 in follicular fluid was decreased in the group who became pregnant (P&#x00A0;&lt;&#x00A0;0.05). The ovarian volume or AFC was significantly higher in groups that became pregnant (P&#x00A0;&lt;&#x00A0;0.05). In addition, the ovarian volume or AFC was positively correlated with the concentration of VEGF or NO and negatively correlated with the concentration of ET-1 in follicular fluid. Our data suggest that these correlations may be associated with the successful pregnancies through IVF.

Nitric oxide synthases and tubal ectopic pregnancies induced by Chlamydia infection: basic and clinical insights

Human ectopic pregnancy (EP) remains a common cause of pregnancy-related first trimester death. Nitric oxide (NO) is synthesized from L-arginine by three NO synthases (NOS) in different tissues, including the Fallopian tube. Studies of knockout mouse models have improved our understanding of the function of NOS isoforms in reproduction, but their roles and specific mechanisms in infection-induced tubal dysfunction have not been fully elucidated. Here, we provide an overview of the expression, regulation and possible function of NOS isoforms in the Fallopian tube, highlighting the effects of infection-induced changes in the tubal cellular microenvironment (imbalance of NO production) on tubal dysfunction and the potential involvement of NOS isoforms in tubal EP after Chlamydia trachomatis genital infection. The non-equivalent regulation of tubal NOS isoforms during the menstrual cycle suggests that endogenous ovarian steroid hormones regulate NOS in an isoform-specific manner. The current literature suggests that infection with C. trachomatis induces an inflammatory response that eventually leads to tubal epithelial destruction and functional impairment, caused by a high NO output mediated by inducible NOS (iNOS). Therefore, tissue-specific therapeutic approaches to suppress iNOS expression may help to prevent ectopic implantation in patients with prior C. trachomatis infection of the Fallopian tube.

How to improve the probability of pregnancy in poor responders undergoing in vitro fertilization: a systematic review and meta-analysis

OBJECTIVE

To systematically review the literature to identify randomized controlled trials, which evaluate interventions aiming to improve the probability of pregnancy in poor responders undergoing in vitro fertilization (IVF).

DESIGN

Systematic review and meta-analysis.

SETTING

University-based hospital.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Pregnancy rate.

RESULT(S)

Twenty-two eligible randomized controlled trials were identified that evaluated in total 15 interventions to increase pregnancy rates in poor responders. Based on limited evidence, the only interventions that appear to increase the probability of pregnancy were the addition of GH to ovarian stimulation (odds ratio for live birth: 5.22, confidence interval: 95% 1.09-24.99) and the performance of embryo transfer on day 2 compared with day 3 (ongoing pregnancy rate: 27.7% vs. 16.3%, respectively; difference: +11.4, 95% confidence interval: +1.6 to +21.0).

CONCLUSION(S)

Insufficient evidence exists to recommend most of the treatments proposed to improve pregnancy rates in poor responders. Currently, there is some evidence to suggest that addition of GH, as well as performing embryo transfer on day 2 versus day 3, appear to improve the probability of pregnancy.

Nitric oxide regulates steroid synthesis by bovine antral granulosa cells in a chemically defined medium

Nitric oxide (NO) in bovine ovary has been characterized as one of the controllers of granulosa cells' (GC) steroidogenesis and apoptosis. One of the pathways used by NO to have these effects is cGMP. The objectives of the present study were to verify the effect of sodium nitroprusside (SNP), a NO donor, on steroidogenesis, cell viability (mitochondrial activity) and GC cell cycle distribution and if this effect occurs by the NO-cGMP signaling pathway with the addition of SNP with or without 1H-[1,2,3] oxadiaziolo[4,3a]quinoxaline-1-one (ODQ), a selective soluble guanylate cyclase inhibitor. The antral GC from 3 to 5mm diameter cattle follicles was cultured without treatment (control), with ODQ (10(-4)M) and 10(-5), 10(-3) and 10(-1)M SNP with or without ODQ for 24h. Nitrate/nitrite (NO(3)(-)/N0(2)(-)) concentrations were evaluated by Griess method, progesterone (P(4)) and 17beta-estradiol (E(2)) concentrations by chemiluminescence, viability and cell cycle stage by MTT method (3-[4,5-dimethylthiazol-2yl]-2,3 dipheniltetrazolium bromide) and flow cytometry, respectively. Nitrate/nitrite concentration in culture medium increased (P<0.05) in a dose-dependent manner according to SNP concentration added to the culture medium. The GC cultured without treatment, with ODQ and with 10(-5)M SNP in the presence or absence of ODQ developed into cell aggregates and did not vary in cell viability (P>0.05), while GC cultured with 10(-3) and 10(-1)M SNP with or without ODQ presented disorganized GC aggregates or did not develop into cell aggregates and also had substantially decreased cell viability (mitochondrial activity inhibition) and steroids synthesis (P<0.05), and effects were not reversed with us of ODQ. Most GC cultured without treatment (control) or with ODQ, 10(-5) and 10(-3)M SNP with or without ODQ were in the G0/G1 (80-75%) stage and in a lesser proportion (20-25%) in the S+G2/M stage of the cell cycle, while the 10(-1)M SNP treatment resulted in GC in G1 phase arrest. The treatment with 10(-5)M SNP increased (P<0.05) E(2) synthesis and inhibited (P<0.05) progesterone synthesis. The addition of ODQ reversed (P<0.05) the stimulatory effect of 10(-5)M SNP treatment on E(2), but not on P(4) synthesis (P>0.05). These results demonstrated that E(2) synthesis by antral GC from small follicles is modulated by lesser NO concentrations via the cGMP pathway, but not P(4) while steroids inhibition cGMP pathway independent, mitochondrial damage and the interference on cell cycle progression caused by greater NO concentration can lead to cell death.

Follicular fluid nitric oxide (NO) concentrations in stimulated cycles: the relationship to embryo grading

OBJECTIVE

The microenvironment of the ovarian follicle is vital for normal oocyte development, folliculogenesis, and timely ovulation. We investigated the concentration of nitric oxide (NO) in follicular fluid, collected during oocyte retrieval after in-vitro fertilization and embryo transfer (IVF-ET) and its relationship to oocyte and embryo grading.

METHODS

A total of 53 follicular fluid samples were obtained from 15 patients undergoing IVF-ET program, oocyte retrieval by transvaginal guidance was per formed approximately 34-35 h after the hCG administration in stimulated cycles. Using a modified grading system the samples were divided in Group 1 with very few fragments in the cytoplasm with equal size blastomeres (best embryos) and Group 2 with significant or severe fragmentation or blastomeres of distinctively unequal size. Follicular NO was measured as nitrite/nitrate.

RESULTS

The mean concentration of NO follicular fluid is significantly higher in Group 2 than in Group 1 (57.54 +/- 12.67 nmol/mg vs. 42.43 +/- 16.32 nmol/mg). Using the correlation analysis, we observed a direct correlation between follicular NO and embryo grading (r = 0.61; P < 0.001) and an inverse correlation between follicular NO and serum 17beta-estradiol (r = -0.28; P < 0.05).

CONCLUSIONS

High levels of NO in human follicles may be detrimental. The inverse correlation found between NO and serum concentrations of 17beta-estradiol may be explained as a regulation of estradiol on maturation process of the oocytes and embryos in stimulated cycles through NO mediation.

Role of vasoactive substances on endometrial and ovarian function

In this review, it is proposed that the vasoactive agents endothelin (ET), nitric oxide (NO)/NO synthase (NOS) and carbon monoxide(CO)/heme oxygenase(HO) act directly on human endometrial functions and on ovarian functions in the normal menstrual cycle and in implantation periods. These vasoactive substances are likely to be important autocrine/paracrine factors that regulate a variety of physiological and pathological processes. The main actions of these agents are differentiation and implantation in the endometrial functions, and follicular growth, luteinization and atresia in the ovarian functions, in the tight connection between endometrial and ovarian systems during normal menstrual periods and during implantation (Reprod Med Biol 2007; 6: 157-164).

Uterine vascularization and pregnancy outcome in patients undergoing intracytoplasmatic sperm injection: the role of nitric oxide

PURPOSE

To evaluate whether, after pituitary desensitisation, the impedance to flow in the uterine vessels may be an indicator of an ICSI programme outcome, and to test the relationship between intrafollicular nitric oxide and oocyte/embryo quality.

METHODS

Thirty-eight women, on the basis of impedance to flow at the level of uterine artery, evaluated on the first day of COH, were divided in patients with normal (Pulsatility Index--PI, 2.5; Group II, n=27) PI values. The patients were submitted to hormonal, ultrasonographic and Doppler evaluations. Plasma and follicular fluid concentrations of nitrites/nitrate (NO(2) (-)/NO(3) (-)) were assayed.

RESULTS

In the Group I, the impedance to flow remained lower than in Group II and was associated to good quality embryos and to a higher pregnancy rate. Follicular fluid NO(2) (-)/NO(3) (-) levels were inversely correlated with the embryo quality. The uterine artery PI and the pregnancy rate were inversely correlated. The PIs analysed on the day 1 of stimulation, were positively correlated with those registered on day 8 and on the day of ovum pick-up.

CONCLUSIONS

A Doppler analysis done on day 1 of controlled ovarian hyperstimulation may be an useful indicator of ART outcome.

The regulators of VEGF expression in mouse ovaries

The objectives of this study were to explore whether ovarian vascular endothelial growth factor (VEGF) expression in mice can be regulated by IL-6 (interleukin-6), angiotensin II, FSH, and hCG; and to test whether the mouse ovarian VEGF expression can result in angiogenesis. The ICR mice were sacrificed, and their ovaries were recovered. Recovered ovaries were treated with IL-6, angiotensin II, FSH, and hCG separately and incubated for 24 hours in alpha-MEM. Expression of mRNA and protein of VEGF were assessed by RT-PCR and immunohistochemistry. The resulting angiogenesis was evaluated through immunohistochemical analysis for CD34. Treatment of mice ovaries with IL-6, FSH, and hCG resulted in a significant increase of VEGF mRNA, and IL-6 was the most potent inducer of VEGF. IL-6 and FSH resulted in increased neovascularization in the follicular phase of mouse ovaries. In contrast, angiotensin II could not increase VEGF expression or neovascularization. We documented an in vitro increase in VEGF expression by IL-6, FSH, and hCG; and reaffirmed that the proliferative response of murine ovarian endothelial cells paralleled an increase of VEGF expression.

Role of oxidative stress in female reproduction

In a healthy body, ROS (reactive oxygen species) and antioxidants remain in balance. When the balance is disrupted towards an overabundance of ROS, oxidative stress (OS) occurs. OS influences the entire reproductive lifespan of a woman and even thereafter (i.e. menopause). OS results from an imbalance between prooxidants (free radical species) and the body's scavenging ability (antioxidants). ROS are a double-edged sword - they serve as key signal molecules in physiological processes but also have a role in pathological processes involving the female reproductive tract. ROS affect multiple physiological processes from oocyte maturation to fertilization, embryo development and pregnancy. It has been suggested that OS modulates the age-related decline in fertility. It plays a role during pregnancy and normal parturition and in initiation of preterm labor. Most ovarian cancers appear in the surface epithelium, and repetitive ovulation has been thought to be a causative factor. Ovulation-induced oxidative base damage and damage to DNA of the ovarian epithelium can be prevented by antioxidants. There is growing literature on the effects of OS in female reproduction with involvement in the pathophysiology of preeclampsia, hydatidiform mole, free radical-induced birth defects and other situations such as abortions. Numerous studies have shown that OS plays a role in the pathophysiology of infertility and assisted fertility. There is some evidence of its role in endometriosis, tubal and peritoneal factor infertility and unexplained infertility. This article reviews the role OS plays in normal cycling ovaries, follicular development and cyclical endometrial changes. It also discusses OS-related female infertility and how it influences the outcomes of assisted reproductive techniques. The review comprehensively explores the literature for evidence of the role of oxidative stress in conditions such as abortions, preeclampsia, hydatidiform mole, fetal embryopathies, preterm labour and preeclampsia and gestational diabetes. The review also addresses the growing literature on the role of nitric oxide species in female reproduction. The involvement of nitric oxide species in regulation of endometrial and ovarian function, etiopathogenesis of endometriosis, and maintenance of uterine quiescence, initiation of labour and ripening of cervix at parturition is discussed. Complex interplay between cytokines and oxidative stress in the etiology of female reproductive disorders is discussed. Oxidant status of the cell modulates angiogenesis, which is critical for follicular growth, corpus luteum formation endometrial differentiation and embryonic growth is also highlighted in the review. Strategies to overcome oxidative stress and enhance fertility, both natural and assisted are delineated. Early interventions being investigated for prevention of preeclampsia are enumerated. Trials investigating combination intervention strategy of vitamin E and vitamin C supplementation in preventing preeclampsia are highlighted. Antioxidants are powerful and there are few trials investigating antioxidant supplementation in female reproduction. However, before clinicians recommend antioxidants, randomized controlled trials with sufficient power are necessary to prove the efficacy of antioxidant supplementation in disorders of female reproduction. Serial measurement of oxidative stress biomarkers in longitudinal studies may help delineate the etiology of some of the diosorders in female reproduction such as preeclampsia.

Embryonic production of nitric oxide and its role in implantation: a pilot study

PURPOSE

To investigate the ability of human embryos to produce nitric oxide (NO) and correlate its production with embryo quality and pregnancy rate.

METHODS

Twenty-three women participated in the study and were submitted to controlled ovarian stimulation and intracytoplasmic sperm injection. Embryos were singularly cultured in medium microdrops of 50 microL and were replaced, by transcervical transfer, at the 2- to 6-cell stage. In the culture media of each embryo the NO production was assessed by monitoring the levels of its stable oxidation products (nitrites/nitrates).

RESULTS

All the 23 patients underwent embryo transfer. After microinjection 64 embryos were obtained. The mean number of transferred embryos was 2.61 +/- 0.46 and the pregnancy rate was 26%. The mean nitrite/nitrate concentrations of culture medium of each embryo was significantly higher (5.88 +/- 2.34 micromol/L) than in pure P-1 medium (0.81 +/- 0.21 micromol/L; p < 0.001) demonstrating an embryonic secretion of NO. Comparing pregnant (7.34 +/- 2.72 micromol/L) versus nonpregnant patients (5.53 +/- 1.49 micromol/L; p = 0.022), the mean nitrite/nitrate concentrations were significantly higher. Furthermore, the best quality embryos of pregnant women produced significantly higher nitrite/nitrate concentrations than those of not pregnant patients.

CONCLUSIONS

It seems that NO production in nidating embryos is increased and that it may be primarily associated with a better morphology and a better growth potential of developing embryos.

Concentrations of nitric oxide in equine preovulatory follicles before and after administration of human chorionic gonadotropin

In the present study, follicular fluids of estrous mares treated with saline solution (Control) or nitric oxide synthase (NOS) inhibitors were analyzed for nitric oxide (NO), estradiol-17beta (E2) and progesterone (P4) concentrations before and 36h after administration of human chorionic gonadotropin (hCG). Follicular fluids obtained before (0h) hCG administration from control mares had lower concentrations of NO than those obtained 36h after administration of hCG (58.3+/-17.8 micromol versus 340.4+/-57.7 micromol; P<0.05). A similar pattern was also noted for intrafollicular P4 in control mares, which had lower concentrations of intrafollicular P4 before hCG than 36h post-hCG administration (P<0.05). As expected, E2 concentrations of control follicles sampled before hCG administration were higher than those sampled 36h post-hCG administration (P<0.05). However, the E2 concentrations in follicles of mares treated with the NOS inhibitors N(omega)-nitro-L-arginine methyl ester (L-NAME) or aminoguanidine (AG) did not decrease after hCG administration, unlike those in control mares (P>0.10). In addition, mares treated with NOS inhibitors had lower intrafollicular concentrations of NO and P4 than control mares, both before and after hCG administration (P<0.05). Increased intrafollicular concentrations of NO in control, hCG-stimulated mares provide evidence for the presence of an NO-generating system in the equine preovulatory follicle that is likely upregulated following administration of hCG.

Decreased viability of nitric oxide synthase double knockout mice

Nitric oxide acts as an important intracellular messenger in a variety of systems, including reproduction. Previous studies have shown the importance of nitric oxide in embryo development. NO is produced from l-arginine by the enzyme, nitric oxide synthase (NOS), which has three isoforms: endothelial (NOS3), neural (NOS1), and inducible (NOS2). We hypothesize that, because of the importance of NOS in development, at least two NOS isoforms are required in order for normal embryo development to occur. Through the generation of NOS3/NOS2, NOS3/NOS1, and NOS2/NOS1 double knockout mice, we found that while litter size remains unchanged, the expected number of generated double knockout mice varies significantly from what would be predicted by Mendelian genetics. Estrous cycles were similar for both DKO and the wild-type mice, and both groups were deemed fertile by their ability to mate with wild-type (CD-1) mice. Together, these results lead us to conclude that the lack of two NOS isoforms leads to a decreased viability in mice because of a developmental problem in the double knockout embryo.

Involvement of nitric oxide and the ovarian blood follicle barrier in murine follicular cyst development

OBJECTIVE

To test the involvement of nitric oxide in murine ovarian follicular cysts.

DESIGN

Controlled animal study.

SETTING

Academic research environment.

ANIMAL(S)

Immature female B6D2F1 mice at 23 +/- 2 days old. Ovarian cysts were induced by implanting miniosmotic pumps that delivered and maintained constant levels of hCG. Nitric oxide studies included the delivery of nitric oxide synthase (NOS) inhibitors, N(G)-nitro-L-arginine methyl ester (L-NAME), or N(G)-nitro-D-arginine methyl ester, by the same method. Ovulation assays measured cumulus oocyte complexes and blood follicle barrier (BFB) function.

RESULT(S)

Chronic treatment with hCG induced enlarged ovaries containing multiple follicular cysts, which were approximately double the size of follicles in sham-operated mice. These cysts enclosed few, if any granulosa cells, secreted high levels of testosterone, and had impaired ovarian BFB function. Inhibition of NOS by L-NAME during ovarian cyst formation reduced the size of follicular cysts, sustained normal testosterone levels, and maintained hormonal BFB reactivity in cystic follicles.

CONCLUSION(S)

Nitric oxide was found to be involved in the formation of hCG-induced murine follicular cysts and complications associated with these cysts were ameliorated by the NOS inhibitor L-NAME.

Follicular fluid adrenomedullin concentrations in spontaneous and stimulated cycles: relationship to ovarian function and endothelin-1 and nitric oxide

The objective of this study was to determine concentration of adrenomedullin (AM) in follicular fluid and whether a correlation exists between AM and nitric oxide (NO) or endothelin-1 (ET-1) levels in follicular fluid, serum 17beta-estradiol or other parameters of ovarian function in spontaneous and gonadotrophin stimulated ovarian cycles. Follicular fluid samples were obtained at oocyte retrieval from 50 women who underwent an in vitro fertilization (IVF) program: 40 undergoing ovarian hyperstimulation with recombinant FSH and 10 had spontaneous ovarian cycles. AM, ET-1, and NO were detected in all of the follicular fluid samples and their concentrations were similar in spontaneous and stimulated cycles. In patients undergoing ovarian stimulation, follicular fluid AM levels correlated with serum 17beta-estradiol concentration. No correlation was found between follicular AM concentration and parameters of ovarian function. Similarly, no relationship was observed between ET-1, NO, and AM follicular fluid concentrations in either spontaneous or stimulated cycles. This study suggests a possible regulatory effect of the sexual hormones on AM production by the ovary during the ovulatory process. The site of AM secretion and its function (if any), however, remain to be established.

Poor ovarian response to gonadotrophin stimulation the role of adjuvant treatments

Poor ovarian response to gonadotrophin stimulation represents a clinical problem in in vitro fertilization practice. Women showing poor ovarian response are a heterogeneous group, many of whom have a reduced ovarian reserve and consequently a lower pregnancy potential. Various management strategies have been proposed to improve ovarian response to gonadotrophins, but these have met with limited success. Adjuvant treatments aim to potentiate the effect of exogenous follicle-stimulating hormone. In separate, randomized, placebo-controlled trials low-dose dexamethasone and aspirin have been shown to reduce the incidence of poor response in an initial stimulation cycle. Preliminary studies using pyridostigmine and L-arginine in established poor responders are encouraging but require confirmation in adequately powered studies. Evidence from randomized controlled trials does not support the use of adjuvant growth hormone or growth hormone-releasing hormone in poor responders without overt growth hormone deficiency. The mechanisms of action of adjuvant treatments require further investigation.

Intraluteal administration of a nitric oxide synthase blocker stimulates progesterone and oxytocin secretion and prolongs the life span of the bovine corpus luteum

To test the role of nitric oxide (NO) in secretory functions of bovine corpora lutea (CL), two groups of four Holstein heifers each were treated as follows: Group 1, Nomega-Nitro-L-Arginine Methyl Ester (L-NAME), an inhibitor of nitric oxide synthase (NOS), on Day 11 or 12 of the cycle and Group 2, L-NAME on Days 17 and 18 of the cycle. All treatments were administered by an intraluteal microdialysis system (MDS). Drugs were infused for 4-hr periods on the designated days, and the treatment periods were preceded and followed by 4-hr control periods. Perfusate and jugular blood samples were collected at half-hour intervals. Perfusate samples were analyzed for progesterone (P4), oxytocin (OT), prostaglandin F2alpha (PGF2alpha), and leukotriene C4 (LTC4); jugular plasma samples were analyzed for P4, OT, and LH. Perfusion of L-NAME on Day 11 or 12 consistently increased P4 concentration in the perfusate, but had no effect on the life span of the CL. Perfusion of L-NAME on Days 17-18 also elevated P4 levels in the perfusate, and in addition, maintained P4 levels in the plasma of three of the four treated animals through Day 25 of the cycle. L-NAME perfusion also increased OT release concomitant with P4 into the perfusate at both the mid- and late-luteal phase treatments. For the most part, concentrations of LH, OT, and P4 in the jugular plasma samples collected during the perfusions were unaffected by treatments. L-NAME perfusion caused small, but significant (P < 0.05) increases in perfusate PGF2alpha and LTC4 at Days 17 and 18 and in LTC4 on Day 11 or 12. These data indicate that NO plays a direct luteolytic role in regression of the bovine CL.

Nitric oxide is essential for optimal meiotic maturation of murine cumulus-oocyte complexes in vitro

This study was conducted to determine whether endothelial-derived nitric oxide synthase (eNOS) affects meiotic maturation of mouse oocytes in vitro. Cumulus-oocyte complexes (COC) were isolated from ovarian follicles of 27-day-old PMSG-primed wildtype (WT), and eNOS-knockout (eNOS-KO) females, and cultured in drops of medium under oil at 37 degrees C for 16-18 hr. Experiment 1 was carried out to determine effects of eNOS deficiency on the ability of COC to mature in vitro. To determine whether acute synthesis of nitric oxide (NO) was required for oocyte maturation, COC collected from WT mice were cultured in medium without (control) or with different doses of N(omega)-nitro-L-arginine methyl ester (L-NAME), an inhibitor of NOS (exp. 2). To assess effects of NO deficiency on the kinetics of germinal vesicle breakdown (GVBD), COC from WT and eNOS-KO females were observed for 3.5 hr. COC from WT females were also incubated in medium without or with L-NAME (exp. 3 and 4). After the culture period, cumulus cells were removed, and oocytes were counted and classified as metaphase II (M II), metaphase I (M I) or showing atypical (degenerative) morphology. To determine viability and nuclear morphology of oocytes, they were stained with fluorescein diacetate or 4,6-diamidine-2'-phenylindole dihydrochloride, respectively. There were no differences in body weights but ovarian weights were lower in eNOS-KO mice compared with WT mice (P < 0.05). Ovaries from eNOS-KO mice contained fewer COC collected relative to WT mice (P < 0.01). Maturation of COC from eNOS-KO mice or WT oocytes treated with L-NAME resulted in a lower percentage of oocytes at M II stage (P < 0.01 and P < 0.05, respectively) and a higher percentage of oocytes at M I or atypical stages compared with those from WT (P < 0.01 and P < 0.05, respectively). Many oocytes that showed either an arrest in M I stage or abnormal morphology were not viable. Several oocytes in M II stage demonstrated abnormalities in distribution of maternal chromosomes. Our data demonstrate that eNOS-derived NO is a key modulator of oocyte meiotic maturation in vitro. These results support our previous observations in vivo and indicate that eNOS/NO has independent functions in both oocyte maturation and follicular/oocyte development.

Adjuvant L-arginine treatment for in-vitro fertilization in poor responder patients

The objective of the present study was prospectively and randomly to evaluate the role of L-arginine in improving uterine and follicular Doppler flow and in improving ovarian response to gonadotrophin in poor responder women. A total of 34 patients undergoing assisted reproduction was divided in two groups according to different ovarian stimulation protocols: (i) flare-up gonadotrophin-releasing hormone analogue (GnRHa) plus elevated pure follicle stimulating hormone (pFSH) (n = 17); and (ii) flare-up GnRHa plus elevated pFSH plus oral L-arginine (n = 17). During the ovarian stimulation regimen, the patients were submitted to hormonal (oestradiol and growth hormone), ultrasonographic (follicular number and diameter, endometrial thickness) and Doppler (uterine and perifollicular arteries) evaluations. Furthermore, the plasma and follicular fluid concentrations of arginine, citrulline, nitrite/nitrate (NO2-/NO3-), and insulin-like growth factor-1 (IGF-1) were assayed. All 34 patients completed the study. In the L-arginine treated group a lower cancellation rate, an increased number of oocytes collected, and embryos transferred were observed. In the same group, increased plasma and follicular fluid concentrations of arginine, citrulline, NO2-/NO3-, and IGF-1 was observed. Significant Doppler flow improvement was obtained in the L-arginine supplemented group. Three pregnancies were registered in these patients. No pregnancies were observed in the other group. It was concluded that oral L-arginine supplementation in poor responder patients may improve ovarian response, endometrial receptivity and pregnancy rate.

Abnormal estrous cyclicity after disruption of endothelial and inducible nitric oxide synthase in mice

The roles of nitric oxide (NO) and nitric oxide synthase (NOS) in reproduction were studied by examining the estrous cycle of wild-type (WT) mice, inducible NOS (iNOS)-, and endothelial NOS (eNOS)-knockout mice. We observed an average estrous cycle of 4.8 +/- 0.2 days in WT mice. While we observed no significant influence of iNOS deficiency on cycle length, eNOS-knockout females showed a significantly longer estrous cycle (6.6 +/- 0.6 days; p < 0.03) than WT females, due to an extension of diestrus (p < 0.03). There was no influence of iNOS deficiency on ovulation rate compared with that in WT females; however, eNOS-knockout mice showed a significant reduction (p < 0.05) in ovulatory efficiency relative to WT or iNOS-knockout females. In contrast to WT females, in which the highest level of estradiol (E2) was observed at 1500 h of proestrus, iNOS-knockout females reached a peak of E2 at 1830 h of proestrus. In eNOS-knockout females, the peak of E2 occurred at 1830 h, as in iNOS-knockout mice; however, E2 levels were 5-fold and 3-fold higher (p < 0.05) than levels observed in WT and iNOS-knockout females, respectively. There was no effect of genotype on the plasma LH concentrations at proestrus. On the first day of diestrus, eNOS-knockout females showed significantly higher plasma E2 and progesterone levels (p < 0.05) relative to WT and iNOS-knockout females. The dysfunction in cyclicity, ovulation rate, ovarian morphology, and steroidogenesis in eNOS-knockout female mice strongly supports the concept that eNOS/NO plays critical roles in ovulation and follicular development.

Ovarian ultrasound image analysis: follicle segmentation

Ovarian ultrasound is an effective tool in infertility treatment. Repeated measurements of the size and shape of follicles over several days are the primary means of evaluation by physicians. Currently, follicle wall segmentation is achieved by manual tracing which is time consuming and susceptible to inter-operator variation. An automated method for follicle wall segmentation is reported that uses a four-step process based on watershed segmentation and knowledge-based graph search algorithm which utilizes priori information about follicle structure for inner and outer wall detection. The automated technique was tested on 36 ultrasonographic images of women's ovaries. Validation against manually traced borders has shown good correlation of manually defined and computer-determined area measurements (R2 = 0.85 - 0.96). The border positioning errors were small: 0.63+/-0.36 mm for inner border and 0.67+/-0.41 mm for outer border detection. The use of watershed segmentation and graph search methods facilitates fast, accurate inner and outer border detection with minimal user-interaction.

Effects of nitric oxide on ovulation and ovarian steroidogenesis and prostaglandin production in the rabbit

Evidence supports the involvement of nitric oxide (NO) in ovarian physiology. The present study was undertaken to investigate the role of the NO/NO synthase (NOS) systems in ovulation, oocyte maturation, ovarian steroidogenesis, and PG production using in vitro perfused rabbit ovaries. The addition of the NOS inhibitors, aminoguanidine hemisulfate salt (AG) and N-omega-nitro-L-arginine methyl ester (L-NAME), to the perfusate inhibited the ovulation induced by hCG in a dose-dependent manner, whereas D-NAME had no significant effect. Neither AG nor L-NAME affected the hCG-induced meiotic maturation of the ovulated ova. The exogenous administration of the NO generator, sodium nitroprusside (NP), induced follicle rupture in the absence of gonadotropin, but did not induce oocyte maturation. Inhibition of endogenous NOS by AG and L-NAME resulted in a significant elevation in the production of estradiol (E2), but not of progesterone, stimulated by hCG. The concomitant administration of NP significantly reduced the AG-stimulated production of E2 by ovaries perfused in the presence of hCG, which suggests that NO down-regulates ovarian E2 synthesis. Ovarian production of PGE2 and PGF2alpha in response to hCG was significantly blocked by L-NAME, and exogenous administration of NP stimulated the production of PGs in the absence of gonadotropin. Significant correlations were observed between the ovulatory efficiencies and the production of PGs by rabbit ovaries perfused with or without L-NAME. In conclusion, the ovarian NO/NOS system is involved in follicle rupture during the ovulatory process. NO may induce follicle rupture in rabbit ovaries at least in part by the stimulation of PG production.