Desensitization to follicle-stimulating hormone in cumulus cells is coincident with hormone induction of oocyte maturation in the rat follicle

Administration of low-dose LH induces ovulation and prevents vascular hyperpermeability and vascular endothelial growth factor expression in superovulated rats

The administration, to rats, of a combination of pregnant mares serum gonadotrophin (PMSG) and human chorionic gonadotrophin (hCG) in high doses induces the ovarian hyperstimulation syndrome (OHSS) which is characterized by increased vascular permeability (VP) and simultaneous overexpression of vascular endothelial growth factor (VEGF) in ovarian cells. hCG has a longer half-life than LH and a greater biological activity, expressed in a higher incidence of complications such as OHSS. Similarly, FSH may also be related to the ovulatory changes within the follicle as there is a simultaneous surge in spontaneous cycles. The aim of this study was to compare the capacity of hCG, FSH and LH to induce ovulation and simultaneously prevent OHSS in the animal model. Immature female rats were treated with 10 IU PMSG for 4 days, and ovulation was triggered with saline, 10 IU hCG, 10 IU FSH, 10 IU LH or 60 IU LH. The number of oocytes ovulated into the tubes, VP and mRNA VEGF expression were evaluated and compared.

All the hormones employed were as effective at triggering ovulation, with similar significant P values when compared with the control for which saline was used. The use of 10 IU LH resulted in significantly lower VP and VEGF expression than that seen in the groups treated with 10 IU hCG, 10 IU FSH or 60 IU LH. In conclusion, FSH and hCG, as well as a sixfold increase in LH, displayed similar biological activities, including increased VP due to excessive VEGF expression. The use of lower doses of LH produced similar rates of ovulation, while preventing the undesired changes in permeability. These experiments should therefore encourage clinicians to determine the optimal dose of LH to be employed in women in order to trigger ovulation and, at the same time, avoid the risk of OHSS.

Luteinizing hormone depletes ascorbic acid in preovulatory follicles

OBJECTIVE

The objective of the present studies was to determine whether luteinizing hormone (LH) depletes ascorbic acid in the preovulatory follicle.

DESIGN

Controlled, prospective experimental study.

SETTING

University-based research center.

ANIMAL(S)

Sprague-Dawley female rats.

INTERVENTION(S)

Follicular growth and ovulation were induced in immature rats by gonadotropin treatment.

MAIN OUTCOME MEASURE(S)

Analysis of ovary, follicle, and oocyte levels of ascorbic acid by colorimetric analysis and high-pressure liquid chromatography.

RESULT(S)

Ovarian ascorbic acid was maximally depleted (50%) within 2 h of LH treatment and was sustained for 8 h. Follicle ascorbic acid levels were unchanged 1 h after LH injection but were significantly reduced within 2 h (40%). Incubation of isolated preovulatory follicles for 3 h with hCG or with menadione (a generator of oxygen radicals) reduced ascorbic acid levels. Isolation of cumulus-enclosed or denuded oocytes depleted ascorbic acid to undetectable levels, but follicular ascorbic acid levels were only moderately depleted by isolation and incubation. Accumulation of ascorbic acid by oocytes was significantly enhanced by the presence of intact cumulus cells.

CONCLUSION(S)

Elevation of LH and the production of oxygen radicals deplete ascorbic acid in the preovulatory follicle.

Eicosatetraynoic and eicosatriynoic acids, lipoxygenase inhibitors, block meiosis via antioxidant action

We previously showed that nordihydroguaiaretic acid (NDGA) and other antioxidants inhibit the resumption of meiosis in oocyte-cumulus complexes (OCC) and denuded oocytes (DO). Because NDGA is well known to be an inhibitor of lipoxygenases (LOX), we assessed whether other LOX inhibitors influence spontaneous germinal vesicle breakdown (GVBD) in OCC and DO. Spontaneous GVBD in rat OCC obtained from preovulatory follicles was significantly and reversibly inhibited by the minimum effective doses of 80 and 100 microM 5,8,11, 14-eicosatetraynoic acid (ETYA) and 5,8,11-eicosatriynoic acid (ETI), respectively. In DO, GVBD was significantly inhibited by 100 microM ETYA or ETI. The minimum effective concentrations of ETYA and ETI for inhibition of GVBD in either OCC or DO are approximately 30- to 50-fold higher than the concentrations necessary to inhibit LOX activity by 50% in intact cells. Because we previously showed that NDGA and other antioxidants inhibit the spontaneous resumption of meiosis, we assessed whether ETYA and ETI may act similarly as scavengers of reactive oxygen species (ROS). Luminol-amplified chemiluminescence showed that 50 microM of either ETYA or ETI markedly and significantly reduced ROS generated with 10 mM 2, 2'-azobis(2-amidinopropane)dihydrochloride (AAPH). Moreover, incubation of DO with 30 mM AAPH reversed the inhibition of GVBD produced by 100 microM ETYA or ETI. These findings support the conclusion that ETYA and ETI inhibit oocyte maturation by acting as antioxidants rather than by inhibiting LOX.

Maturation in vitro of human oocytes from unstimulated cycles: selection of the optimal day for ovum retrieval based on follicular size

The potential use of immature oocytes for in-vitro fertilization (IVF) requires the conditions for successful maturation to be defined. This study focused on the day of oocyte retrieval. The selection of a dominant follicle may induce endocrine changes in the remaining cohort that may be detrimental to their subsequent fertilization and embryonic development. Natural cycles in volunteer donors were followed by measurement of serum oestradiol and by vaginal ultrasound, starting on day 3 of the cycle. Cycles were randomly allocated to one of two groups: group 1 (n = 10), in which follicles were aspirated before the leading follicle was 10 mm in diameter; and group 2 (n = 9), in which follicles were aspirated when a dominant follicle was clearly visible with diameter >10 mm. Oocytes were cultured in vitro to metaphase II (MII) stage, donated, and inseminated by intracytoplasmic sperm injection (ICSI) with husband's spermatozoa. Those that became fertilized within 24 h were further co-cultured in autologous endometrial epithelial cells up to the blastocyst stage, and cryopreserved. There was a significantly (P < 0.05) increased rate of oocyte retrieval in group 1 (70.8% of aspirated follicles) compared with group 2 (50.5%). Maturation to MII and fertilization were similar between the groups. However, development to blastocyst stage was significantly (P < 0.05) higher in group 1 embryos (56.5%) compared with group 2 (35.7%). There was a positive correlation (r2 = 0.1978) between the appearance of the cumulus cells and the ability to develop to blastocyst stage when both parameters were analysed in group 1, whereas no such correlation was found in group 2. In conclusion, our data suggest the importance of retrieving immature oocytes before follicular selection, and define the conditions for the first stage in the use of immature oocytes. Further stages must be defined before this technique can be used clinically.

Segregation of retinoic acid effects on fetal ovarian germ cell mitosis versus apoptosis by requirement for new macromolecular synthesis

Retinoic acid (RA), a naturally occurring metabolite of vitamin A, plays an essential role in regulating cellular growth, differentiation, and death in a variety of tissues, particularly during fetal development. However, essentially nothing is known of the effects of RA on fetal gametogenesis. Using a recently validated system of culturing murine fetal ovaries, herein we sought to characterize the actions of RA on female germ cell proliferation and apoptosis during oogenesis. In the absence of trophic hormone support, approximately 90% of the oogonia and oocytes present in fetal ovaries at the start of culture underwent apoptosis over a 72 h culture period (P < 0.05), whereas provision of 0.01-1 microM RA dose dependently maintained germ cell numbers. In fact, ovaries cultured with 0.1 microM RA for 72 h possessed approximately 30% more oogonia and oocytes as compared with the preculture mean number (P < 0.05). Additional experiments, using in situ DNA 3'-end-labeling and cellular morphology to assess apoptosis coupled with 5-bromo-2'-deoxyuridine incorporation to assess proliferation, revealed that RA acts as both a mitogen and a survival factor for female germ cells. Furthermore, the ability of RA to stimulate germ cell proliferation in cultured fetal ovaries was completely suppressed (P < 0.05) by cotreatment with inhibitors of transcription (alpha-amanitin, 0.1 microg/ml) or protein synthesis (cycloheximide, 1.0 microg/ml), whereas RA-mediated suppression of germ cell apoptosis was not affected by cotreatment with either macromolecular synthesis inhibitor (P > 0.05). Moreover, cotreatment of fetal ovaries with 5 microM LY294002, an inhibitor of phosphatidylinositol 3'-kinase, had no effect on RA-promoted germ cell maintenance (P > 0.05). By comparison, the antiapoptotic effects of insulin-like growth factor I on germ cells in cultured fetal ovaries were significantly attenuated by cotreating ovaries with LY294002 (P < 0.05) but not with alpha-amanitin or cycloheximide (P > 0.05). Importantly, the effect of RA on the female germ line was also observed in vivo because a single oral administration of 100 mg/kg RA to timed-pregnant female mice resulted in a significantly (P < 0.05) larger endowment of primordial oocytes in female offspring. That these actions were mediated, at least in part, by specific retinoid receptors was demonstrated by the finding of retinoic acid receptor protein in fetal female gonocytes, as assessed by immunohistochemical localization experiments. Collectively, these data indicate that RA can function, in vitro and in vivo, as a potent germ cell survival factor and mitogen during fetal oogenesis in the mouse.

Antioxidants reversibly inhibit the spontaneous resumption of meiosis

We previously showed that the cell-permeant antioxidant 2(3)-tert-butyl-4-hydroxyanisole (BHA) inhibited germinal vesicle breakdown (GVBD) in oocyte-cumulus complexes (OCC) of the rat. The objective of the present studies was to assess other antioxidants and whether such inhibition was reversible. Spontaneous GVBD in OCC incubated for 2 h was significantly inhibited (P < 0.005) by nordihydroguaiaretic acid (NDGA; GVBD = 19.4%), BHA (GVBD = 25.7%), octyl gallate (OG; GVBD = 52.2%), ethoxyquin (EQ; GVBD = 58.8%), 2, 6-di-tert-butyl-hydroxymethyl phenol (TBHMP; GVBD = 59%), butylated hydroxytoluene (BHT; GVBD = 59.5%), and tert-butyl hydroperoxide (TBHP; GVBD = 60.0%). Other antioxidants that produced lower but significant (P < 0.05) inhibition of oocyte maturation included propyl gallate (PG; GVBD = 70.3%), 2,4,5-trihydroxybutrophenone (THBP; GVBD = 71.4%), and lauryl gallate (LG; GVBD = 71.4%). Antioxidants that had no effect on oocyte maturation at the same concentration (100 microM) included ascorbic acid, vitamin E, and Trolox. Inhibition of GVBD was evident for up to 8 h of incubation of OCC and denuded oocytes (DO) with BHA or NDGA and was reversed by washing. NDGA was less potent than BHA for inhibition of GVBD in DO, unlike that seen with OCC. Oocyte maturation was induced by incubation of follicles for 3 h with human chorionic gonadotropin (hCG), and this response was inhibited by BHA or NDGA. These findings support the conclusion that cell-permeant antioxidants inhibit spontaneous resumption of meiosis, which may implicate a role of oxygen radicals in oocyte maturation.

FSH bioactivity is strongly enhanced by kinetic incubation of pre-antral hamster follicles

Isolation of meiotic arrested oocytes from mammalian ovaries involves a resumption of the meiosis. Studying the effect of FSH on this process it was found that doses up to of 0.1 IU/ml did not maintain the meiotic arrest in hamster oocytes in pre-antral follicles during static incubation conditions. However, when the FSH medium was replaced at 120, 60 and 30 min the resumption of the meiosis gradually decreased. Using a replacement frequency of 30 min a complete log dose-curve was constructed (ED50: 0.5 mU/ml; minimum effective dose: 0.1 mU/ml). The lack of a FSH response during static incubation was not caused by exhaustion of its bioactivity: mixing of the FSH containing medium, obtained from a 4 hours' static incubation, resulted in an inhibition similar to the inhibition that occurred during the replacement procedure.

IN CONCLUSION

FSH is able to maintain the meiotic arrest in pre-antral follicle enclosed oocytes at low doses only when the medium is in circulation.

Aldose reductase inhibition prevents galactose-induced ovarian dysfunction in the Sprague-Dawley rat

OBJECTIVE

Our objective was to determine whether impaired ovarian function induced by short-term creation of a galactosemic state in the rat might be prevented by the coadministration of an aldose reductase inhibitor.

STUDY DESIGN

Prepubertal Sprague-Dawley rats were fed four different diets including (1) control, (2) 40% galactose, (3) 40% galactose and an aldose reductase inhibitor, and (4) an aldose reductase inhibitor with the control diet. Percentage germinal vesicle breakdown, postovulatory oocyte quantities, hormonal parameters, ovarian histologic evaluation, and ovarian galactitol concentrations were determined.

RESULTS

The galactose-fed animals (group 2) had decreased germinal vesicle breakdown (47%) versus control (69%, p < 0.05). Galactose-exposed animals had significantly decreased quantities of postovulatory eggs (6.4 per animal) after menotropin ovarian stimulation in comparison with controls (14.1, p < 0.01). In rats exposed to high dietary levels of galactose (group 2) ovarian galactitol concentrations were significantly higher (protein 42.12 mumol/gm versus 0.0 for controls, p < 0.005). When galactose-fed animals received the aldose reductase inhibitor, ovarian accumulation of galactitol was significantly reduced and the observed detrimental effects on the oocyte were prevented.

CONCLUSION

Galactitol accumulation or metabolic flux through aldose reductase in galactosemic rodents may be involved in the demonstrated ovarian dysfunction.

Xanthine oxidase and dehydrogenase activities in rat ovarian tissues

The production of reactive oxygen species in the ovary is rapidly inducible, but the nature of the generator is unknown. One possibility is xanthine oxidase (XO), an enzyme that produces superoxide in the presence of hypoxanthine (or xanthine) and oxygen. The objective of the present studies was to measure levels of XO in follicular and luteal tissue to determine whether XO may be a source of reactive oxygen species in the rat ovary. Ovarian levels of XO were about one-fifth of that seen in the liver and adrenal, and XO levels were about one-third of xanthine dehydrogenase (XDH). Preovulatory ovarian levels of XO activity were unchanged after induction of ovulation with gonadotropin and in follicles incubated with gonadotropin. Luteal XO activity was not changed during natural or prostaglandin F2 alpha (PGF2 alpha)-induced luteolysis. Allopurinol, an inhibitor of XO, did not inhibit ovulation or PGF2 alpha-induced luteal regression. Finally, neither catalase and superoxide dismutase nor oxypurinol altered luteal cell function in the presence of hypoxanthine. Thus, while XO is present in the ovary, it does not appear that it is a major source of reactive oxygen species in this organ.

Fertilizability and subsequent developmental ability of bovine oocytes matured in medium containing epidermal growth factor (EGF)

We have previously shown that epidermal growth factor (EGF) is capable of promoting maturation of bovine cumulus-oocyte complexes in chemically defined serum-free medium. In this study, fertilizability and subsequent developmental capacity of bovine oocytes matured in EGF-containing medium were evaluated. Fetal bovine serum (FBS, 10%) and EGF at 10 ng/ml in Dulbecco's modified Eagles medium with Ham's nutrient mixture F-12 (DME/F12) significantly increased the rate of formation of two pronuclei compared with the rate obtained from DME-F12 alone (P<0.05). Early embryonic development was assessed during 48 h in culture. Data were evaluated in terms of cleavage and four- to eight-cell formation. Oocytes matured in 10 ng/ml EGF showed significantly higher rates of cleavage (P<0.01) and four- to eight-cell formation than did oocytes matured in control medium (P<0.05). Bovine oocytes matured in the presence of EGF can be normally fertilized and can cleave and develop in vitro up to the eight-cell stage.

In vitro fertilization as a diagnostic and therapeutic tool in a patient with partial 17,20-desmolase deficiency

OBJECTIVE

To present a case with 17,20-desmolase activity deficiency in which in vitro fertilization (IVF) served not only as a therapeutic approach but also as a diagnostic tool for the specificity of the enzymatic deficiency.

DESIGN

IVF in the patient under study compared with a control group. All women treated with pure follicle-stimulating hormone (FSH).

SETTING

IVF program at the Instituto Valenciano de Infertilidad.

PATIENTS, PARTICIPANTS

A patient with primary amenorrhea, who was the subject under study, and seven normally cycling control patients undergoing IVF in the same series.

INTERVENTIONS

IVF, steroidogenesis in vitro of granulosa-luteal cell obtained at ovum pick-up.

MAIN OUTCOME MEASURE(S)

Oocyte fertilization and embryo cleavage. Serum and follicular fluid (FF) levels of estradiol (E2), progesterone (P), testosterone (T), androstendione (A), 17 alpha-hydroxyprogesterone (17-OHP). In vitro accumulation of E2 and P.

RESULTS

Ovulation induction with FSH was successful in achieving follicular development despite low circulating E2. Fertilization and cleavage rates were similar to the control subjects. The patient developed ovarian hyperstimulation. The lack of 17,20-desmolase activity was detected by normal P levels in serum and FF, high 17-OHP, and low T, A, and E2 levels in serum and FF. Granulosaluteal cell cultures in the presence of T restored normal E2 and P production in response to gonadotropins.

CONCLUSIONS

In patients with 17,20-desmolase deficiency, follicular development, oocyte maturation, and fertilization can take place in a low estrogenic environment.