Expression of components of the insulin-like growth factor system and gonadotropin receptors in bovine cumulus-oocyte complexes during oocyte maturation

IGF system expression has been largely explored in the bovine follicular wall whereas it remains poorly studied in the COC. Using semi-quantitative RT-PCR and Western blot analysis, we have investigated spatial and temporal expression of IGF-1, IGFR-1, IGFBP-2, IGFBP-4, as well as gonadotropin receptors in bovine COC during oocyte maturation. In addition, we have compared changes in the IGF system and FSHR expression during in vitro maturation in TCM199 alone or in the presence of 10 ng/ml of EGF. The transcripts for IGFR-1 and IGFBP-2 were detected in cumulus and germinal cells whereas IGF-1, IGFBP-4 and FSHR mRNA were restricted to cumulus cells. Topography of the IGF system and gonadotropin receptor expression within COC were unaffected by the maturation step. In contrast, levels of IGFBP-2 and FSHR expression decreased (P < 0.05) in matured COC. Under defined culture conditions, IGFBP-2 and FSHR mRNA expression remained at a high level in TCM199 alone and were significantly reduced (P < 0.05) in the presence of 10 ng/ml EGF after a 24 h period of in vitro maturation. In conclusion, our results demonstrate a cell-specific pattern of IGF system member gene expression within bovine COC suggesting interaction between the somatic and germinal compartments. In addition, synchronized changes in the pattern of COC IGFBP-2 and FSHR expression during oocyte maturation suggest possible synergistic actions between IGF-1 and FSH.

Small nuclear RING finger protein expression during gonad development: regulation by gonadotropins and estrogen in the postnatal ovary

Small nuclear RING finger protein (SNURF/RNF4) is a steroid receptor coregulator that is down-regulated in testicular germ cell cancer. In this work, we examined SNURF expression during murine fetal gonad development and postnatal ovarian folliculogenesis by in situ hybridization and immunohistochemical staining. SNURF mRNA was detectable in gonads of both sexes from embryonic 10.5 days post conception onward. SNURF protein localized to gonocytes and somatic Leydig and Sertoli cells of fetal testis and in oogonia and supporting cells of fetal ovary. In murine postnatal ovary, SNURF mRNA and protein were expressed throughout folliculogenesis, peaking in the oocytes of preantral follicles. Lower amounts of SNURF mRNA and protein were also present in granulosa cells of secondary, antral, and preovulatory follicles and in luteal glands. Exposure of immature female mice and rats to gonadotropin from pregnant mare serum and human chorionic gonadotropin did not change dramatically SNURF mRNA levels in ovary. SNURF mRNA expression was increased in ovaries of immature mice treated with diethylstilbestrol, an effect that was blocked by the pure antiestrogen ICI 182,780. SNURF protein was constitutively expressed in oocytes of hypophysectomized rats, and its content was augmented by estradiol in granulosa cells. In granulosa cell culture, SNURF mRNA accumulation was transiently increased by treatment with the LH agonists phorbol myristate and forskolin at 4 h after treatment and at 48 h in differentiated cells expressing markers of the preovulatory phenotype. These results suggest a role for SNURF in fetal germ cell development as well as in oocyte and granulosa cell maturation in an estrogen- and gonadotropin-regulated fashion.

Estrogen regulation of nitric oxide synthesis in the procine oocyte

The endothelial type (NOS-3) of three isoforms of nitric oxide (NO) synthase occurs in porcine oocytes and granulosa cells, but the regulation of NO synthesis in oocytes remains unknown. The present study was designed to evaluate steroid control in the process of oocyte NO synthesis. Cumulus-oocyte complexes (COCs), obtained from small-sized antral follicles of immature porcine ovaries, were cultured in estrogen-deprived medium, and the effect of steroids or steroid-free porcine follicular fluids on the NO release from oocytes was investigated. Oocytes that were isolated from cultured COCs were incubated with 1 microM ionomycin. The NO metabolites were identified using a NO detector-high-pressure liquid chromatography system. Oocytes from COCs cultured with 10 nM 17beta-estradiol (E2) released NO in response to ionomycin, whereas progesterone and testosterone had little effect on the synthesis of NO. An inhibitor of NOS suppressed the synthesis of NO. The maximal synthesis was observed after a 15 h-culture with E2. However, oocytes freshly obtained from antral follicles did not response to ionomycin, and the E2 action was suppressed by the addition of steroid-free follicular fluids. Analyses of RT-PCR and Western blotting showed that E2 did not increase NOS-3 expression. In addition, estrogen receptor beta was detected in oocytes and cumulus cells, and estrogen receptor alpha was detected only in cumulus cells. These findings suggest that oocyte NOS-3 is promoted for the synthesis of NO by E2 without increases in NOS-3 expression, but the synthesis of NO is suppressed, at least in the oocytes of early antral follicles.

Expression of Hox cofactor genes during mouse ovarian follicular development and oocyte maturation

Very little is known about the expression and function of the HOX and HOX-cofactors genes in mammalian oogenesis. The aim of the present study was to determine the expression of PBX and PREP-1 gene products in the mouse ovary and their localization to particular ovarian compartment, specifically the oocyte-containing ovarian follicle. Immunocytochemical analysis demonstrated that PREP-1 was present in both granulosa cells and oocytes. PREP-1 was found in the nucleus in primary oocytes, but in the cytoplasm of fully-grown oocytes; in granulosa cells, however, PREP-1 was always localized to the nuclei. No PREP-1 immunoreactivity was found in corpus luteum, theca or stroma. PBX-1 was found in the cytosol of the oocyte, while PBX-2 expression was mostly restricted to the nuclei of granulosa cells. In addition, PBX-2 was also found in the nucleus of primary oocytes. Since PREP-PBX complexes act in vivo in conjunction with HOX transcription factors, we have used RT-PCR to identify HOX genes expressed in the ovary. This analysis identified transcripts for six HOX genes (A5, A9, B6, B7, C6 and C8) and two more TALE cofactors (PREP2 and Meis2). Thus, a number of HOX and HOX cofactor genes are expressed in the mammalian ovary. The restricted expression pattern for PBX-1 and PBX-2 and the changes in expression and localization of PREP-1 in the oocyte and granulosa cells suggest a previously unsuspected involvement of these transcription factors in oocyte maturation and development, as well as in granulosa cell differentiation.

Colocalization of DNA Fragmentation and Caspase-3 Activation During Atresia in Pig Antral Follicles

Apoptosis is the cellular mechanism of ovarian follicular atresia. The major downstream effector of this phenomenon in many tissues is caspase-3 but little is known about its role in pig ovarian apoptosis. In the present study, we detected the localization of caspase-3 in parallel with nuclear fragmentation (TUNEL) on healthy and early atretic antral follicles. In healthy antral follicles caspase-3 and TUNEL positivity were occasionally recorded within theca layer. The incidence of DNA fragmentation, as indicated also by the biochemical detection, increased mainly in the granulosa layer of early atretic follicles. Quantitative analysis revealed, besides, that atresia was accompanied by a higher incidence of caspase-3 (57.20 +/- 20.05 versus 3.64 +/- 0.61 positive cells in atretic versus healthy follicles, respectively; P < 0.05), of TUNEL positivity (20.13 +/- 9.33 versus 0.42 +/- 0.12; P < 0.05) and simultaneous immunostaining for caspase-3 and TUNEL (15.02 +/- 6.95 versus 0.31 +/- 0.05; P < 0.05) in the granulosa layer. In detached granulosa cells isolated from the follicular fluid of early atretic follicles a further significantly increase was recorded in the percentage of TUNEL positivity and in the incidence of cells that showed colocalization of caspase-3 activity and DNA fragmentation. Granulosa cells of early atretic follicles exhibited a higher positivity for caspase-3 localized in the cytoplasm and occasionally in the nucleus area of granulosa cells. These results indicate that capsase-3 was involved and precociously activated during the process of atresia. Finally, the progressively higher incidence of TUNEL positivity and of double immunostaining in atretic cells collected within the follicular fluid seems to indicate that proteases activity leads only tardily in a detectable DNA fragmentation.

Bone morphogenetic protein (BMP) ligands and receptors in bovine ovarian follicle cells: actions of BMP-4, -6 and -7 on granulosa cells and differential modulation of Smad-1 phosphorylation by follistatin

Given the paucity of information on the potential roles of bone morphogenetic proteins (BMPs) in the ruminant ovary we conducted immunolocalization and functional studies on cells isolated from bovine antral follicles. Immunocytochemistry revealed expression of BMP-4 and -7 in isolated theca cells whereas granulosa cells and oocytes selectively expressed BMP-6. All three cell types expressed a range of BMP-responsive type-I (BMPRIB, ActRI) and type-II (BMPRII, ActRII, ActRIIB) receptors supporting autocrine/paracrine roles within the follicle. This was reinforced by functional experiments on granulosa cells which showed that BMP-4, -6 and -7 promoted cellular accumulation of phosphorylated Smad-1 but not Smad-2 and enhanced ‘basal’ and IGF-stimulated secretion of oestradiol (E2), inhibin-A, activin-A and follistatin (FS). Concomitantly, each BMP suppressed ‘basal’ and IGF-stimulated progesterone secretion, consistent with an action to prevent or delay atresia and/or luteinization. BMPs also increased viable cell number under ‘basal’ (BMP-4 and -7) and IGF-stimulated (BMP-4, -6 and -7) conditions. Since FS, a product of bovine granulosa cells, has been shown to bind several BMPs, we used the Biacore technique to compare its binding affinities for activin-A (prototype FS ligand) and BMP-4, -6 and -7. Compared with activin-A (Kd0.28 ± 0.02 nM; 100%), the relative affinities of FS for BMP-4, -6 and -7 were 10, 5 and 1% respectively. Moreover, studies on granulosa cells showed that preincubation of ligand with excess FS abolished activin-A-induced phosphorylation of Smad-2 and BMP-4-induced phosphorylation of Smad-1. However, FS only partially reversed BMP-6-induced Smad-1 phosphorylation and had no inhibitory effect on BMP-7-induced Smad-1 phosphorylation. These findings support functional roles for BMP-4, -6 and -7 as paracrine/autocrine modulators of granulosa cell steroidogenesis, peptide secretion and proliferation in bovine antral follicles. The finding that FS can differentially modulate BMP-induced receptor activation and that this correlates with the relative binding affinity of FS for each BMP type implicates FS as a potential modulator of BMP action in the ovary.

Localization of angiotensin II in pig ovary and its effects on oocyte maturation in vitro

The renin-angiotensin system (RAS) has been found in mammalian ovarian tissue; however, its physiological role is unclear. This study examined the content of angiotensin II (Ang II) in porcine follicular fluid (pFF), Ang II localization and its receptors in ovary, and the effects of Ang II on porcine oocyte maturation. The concentrations of Ang II were 6951.82 +/- 1295.83, 3502.99 +/- 679.10, 3147.89 +/- 690.60, and 2545.92 +/- 407.01 pg/ml in pFF from small, medium, large, and extra-large follicles, respectively. In addition, Ang II was found on zona pellucidae (ZP) and granulosa cells by immunoreactive staining. The distribution of AT1, an Ang II receptor subtype, was in accordance with that of Ang II. However, AT2, another Ang II receptor, was mainly distributed in the stroma and thecal layers of follicles. When oocytes were cultured in media containing various concentrations of Ang II, a higher (P<0.05) proportion of oocytes reached metaphase II (MII) in the medium with 100 ng/ml (87.0%) than without Ang II (61%). When oocytes from different sizes of follicles were separately cultured in media containing 100 ng/ml Ang II, maturation rates were significantly higher in oocytes from small (61.5%) and medium (85.1%) follicles than that of their controls (45.1 and 72.6%, respectively). However, addition of Ang II inhibited nuclear maturation in oocytes from large follicles (77.8% versus 87.3%). Fertilization and male pronuclear (MPN) formation rates of oocytes matured in medium containing 100 or 1000 ng/ml of Ang II were higher (P<0.05) than that of oocytes matured in medium containing 0 or 10 ng/ml Ang II. Glutathione content in oocytes cultured for 44 h in medium containing 100 or 1000 ng/ml of Ang II was also higher (P<0.01) than that of oocytes cultured in medium containing 0 or 10 ng/ml Ang II. In conclusion, Ang II was present in porcine ovaries and may regulate follicle growth and oocyte maturation.

Anti-apoptotic action of stem cell factor on oocytes in primordial follicles and its signal transduction

Stem cell factor (SCF) is essential for the development of primordial follicles. One of its functions is to prevent oocytes from apoptosis. However, the underlying mechanism remains largely unknown. By using cultured ovaries that are rich in primordial follicles, the anti-apoptotic action of SCF and the potential signal transduction pathways were investigated. The apoptosis was evaluated by means of in situ 3'-end labeling. The expressions of proteins were analyzed with immunohistochemistry and Western blot. The data showed that SCF significantly prevented oocytes from apoptosis in the cultured organs. Addition of a specific pharmacological inhibitor of PI3K abolished the anti-apoptotic action of SCF while that of a MEK inhibitor did not. The phosphorylation of two mitogen activated protein kinases (MAPKs) (p42 and p44) and AKT, the respective substrates of MEK and PI3K, were enhanced by SCF treatment. Not surprisingly, the MAPK activation occurred only in theca cells. The expressions of apoptosis-related gene products, the Bcl-2 family proteins, in response to SCF treatment were also investigated. While SCF up-regulated the expression of the anti-apoptotic proteins Bcl-2 and Bcl-xL, it did the opposite to the pro-apoptotic factor Bax. The PI3K inhibitor reversed the regulation of SCF on Bcl-xL and Bax but not on Bcl-2. Therefore, it seemed that SCF initiated an anti-apoptotic signal starting from its membrane receptor c-kit to Bcl-2 family members through PI3K/AKT and other signaling cascades in the oocytes of primordial follicles.

Expression of growth differentiation factor 9 (GDF9), bone morphogenetic protein 15 (BMP15), and BMP receptors in the ovaries of goats

The process of ovarian folliculogenesis is composed of proliferation and differentiation of the constitutive cells in developing follicles. In goats, relatively little information is available on the local factors that regulate this process. We studied the presence and distribution of growth differentiation factor 9 (GDF9), bone morphogenetic protein 15 (BMP15), and BMP receptors types 2 (BMPR2), 1A (BMPR1A), and 1B (BMPR1B) in goat ovaries to find evidence for their possible roles in folliculogenesis. Ovaries of cyclic goats were collected and fixed in paraformaldehyde for immunohistochemical localization of GDF9 and BMP15 proteins or used to collect follicles and luteal tissue to study the mRNA expression of GDF9, BMP15, and BMP receptors using reverse transcriptase polymerase chain reaction (RT-PCR). GDF9 and BMP15 proteins were found in oocytes of all types of follicles and granulosa cells of primary, secondary, and antral but not primordial follicles. The mRNAs for GDF9, BMP15, BMPR2, BMPR1A, and BMPR1B were detected in primordial, primary, and secondary follicles as well as in oocyte and granulosa cells of antral follicles. Transcripts for BMPR2, BMPR1A, BMPR1B, and GDF9, and GDF9 protein were furthermore found in corpora lutea. It is concluded that the mRNAs and proteins of GDF9 and BMP15 and the mRNAs of BMP receptors are expressed in goat ovarian follicles at all stages of their development, and that they form a complex intrafollicular regulatory system during folliculogenesis. Expression of all BMP receptor mRNAs and GDF9 mRNA and protein in luteal tissue additionally points to a role of GDF9 in corpus luteum function.

Development of antral follicles in cryopreserved cat ovarian tissue transplanted to immunodeficient mice

Ovarian cortex cryopreservation and xenotransplantation into immunodeficient mice represents a potential means for female germplasm conservation and an immediate model for investigation of folliculogenesis. The objectives of this study were to: (1) assess follicle survival after cryopreservation and transplantation of cat ovarian tissue into non-obese diabetic severely combined immunodeficient (NOD SCID) mice; and (2) evaluate the effects of gonadotropin treatments on follicular development in the transplanted tissue. Slices from the cat ovarian cortex were frozen and after thawing, transplanted under each kidney capsule of castrated male NOD SCID mice (eight xenografts in four mice). Sixty-two days after surgery, mice were randomly assigned (two per group) to gonadotropin-treated (eCG and hCG 88 h later) or control (saline-treated) groups. Twenty-four hours after the last injection, ovarian tissue was recovered and processed for histology. Fresh ovarian tissue from the same original source was similarly processed. Follicles were counted, measured, and classified as primordial, primary, secondary, or antral. Immunoreactive proliferating cell nuclear antigen (PCNA) stain was used to assess follicle viability. Microscopic examination revealed no evidence of necrosis or fibrosis. The grafts were well-vascularized, with follicles at all stages of development. Numbers of follicles in the transplanted tissue were markedly reduced compared to fresh tissue, with approximately 10% of follicles surviving freezing and transplantation procedures. Growing follicles positive for PCNA were found in all xenografts. Gonadotropin treatment did not alter the proportion of resting to growing follicles or mean follicle diameter by comparison with controls from untreated mice. By contrast, luteinization, but not ovulation, of antral follicles was observed only in grafts from treated mice. In summary, frozen-thawed cat ovarian cortex tissue not only survived xenotransplantation, it also contained follicles able to grow to antral stages. Exogenous gonadotropin treatment in this model resulted in luteinization of antral follicles but enhancement of follicular growth and ovulation did not occur.

Fas and Fas ligand protein and mRNA in normal and atretic mouse ovarian follicles

Apoptosis is the underlying mechanism of follicular atresia in the mammalian ovary. However, the apoptotic pathways governing this ovarian process are not completely elucidated. In the present study, expression of Fas and Fas ligand, the proximal members of the death receptor pathway, was evaluated in mouse ovarian follicles using immunofluorescence and in situ hybridization. Normal or atretic follicles were obtained from immature female Swiss mice after administration of 10 iu equine chorionic gonadotrophin for 48 or 72 h, respectively. Expression of both Fas and Fas ligand mRNA and protein was observed in granulosa cells of normal and atretic follicles. Although the oocytes of normal follicles failed to show any staining, those of atretic follicles stained intensely for Fas, indicating that the presence of Fas in the oocyte determines the fate of the follicle.

Attenuation by leptin of the effects of fasting on ovarian function in hens (Gallus domesticus)

Thirty-four-week-old laying hens received injections of recombinant chicken leptin to assess the role of leptin in avian ovarian function. In the first experiment, the hens (n=60) were divided into three groups: (i). fed ad libitum; (ii). fasted; and (iii). fasted + leptin. Hens were fasted for 5 days and those treated with leptin received 250 microg leptin kg-1 body weight twice a day, i.p. In the second experiment, the hens (n=72) were divided into four groups: (i). fed ad libitum; (ii). fasted; (iii). fasted + leptin given only during fasting (5 days); or (iv). fasted and leptin given during both fasting and 5 days of re-feeding (10 days). LH was measured in blood plasma, and progesterone and oestradiol were measured in blood plasma and the ovary by radioimmunoassay. Apoptosis was examined in the walls of the three largest yellow hierarchical follicles (F3-F1; F3<F2<F1; 25-35 mm) by the TdT-mediated dUTP nick-end labelling method. Results showed that the injections of leptin during fasting: (i). delayed cessation of egg laying; (ii). attenuated regression of yellow hierarchical follicles; (iii). altered ovarian steroidogenesis; and (iv). abolished the fasting-induced apoptosis in the wall of F3-F1 follicles during the first 2 days of fasting and partially attenuated apoptosis after 5 days of fasting. Prolongation of leptin injections into the re-feeding period considerably delayed the restoration of the ovary. Expression of leptin receptor in laying hens was determined by RT-PCR. The highest expression of leptin receptor was observed in the hypothalamus. Lower receptor mRNA expression was found in the hypophysis, whereas the lowest expression was observed in the ovary. Within the ovary, a relatively high expression of leptin receptor was found in the stroma with cortical follicles <1 mm, the wall of white (1-8 mm) and small yellow follicles (>8-12 mm), and the granulosa layer of F3 follicles. The expression of leptin receptor in the granulosa layer of F2 and F1 follicles was barely detectable. This was in contrast to a much higher expression of leptin receptor maintained in the theca layer of F3-F1 follicles. The present results indicate that in chickens leptin might be involved in the adaptation to starvation due to attenuation of follicular apoptosis. The presence of leptin receptors in the ovary indicates the possibility of a peripheral effect of the hormone.

Evidence of apoptosis in human primordial and primary follicles

BACKGROUND

Apoptosis may operate the 'selection' between follicles destined for atresia and follicles that will remain available for ovulation. The aim of this study is to assess the expression of apoptosis in quiescent follicles.

METHODS

Ovarian cortex samples from women of reproductive age, fixed in formalin, were used for immunohistochemical and terminal deoxynucleotidyl transferase-mediated deoxy-UTP nick end labelling (TUNEL) methods. In histological sections the follicles were classified as primordial, primary, secondary and antral. Follicle density was defined as the total number of follicles/0.5 cm(2) of ovarian cortical tissue. Mab DO-7 (anti-p53) and Mab 124 (anti-bcl-2) were used in the immunohistochemical study.

RESULTS

TUNEL was positive in 23.4% of the primordial follicles, and in 23.2% of the primary follicles, both in oocytes and granulosa cells, whereas all secondary follicles were negative. Bcl-2 activity was expressed in 75% of secondary follicles. p53 was negative in all samples.

CONCLUSIONS

Apoptosis could be the process responsible for atresia of quiescent follicles and hence depletion of the ovarian germ stockpile. Follicular cells expressing Bcl-2 may therefore be the viable cells that escape the apoptotic process. Negative p53 patterns may be a favourable prognostic finding showing genome integrity in the replicating follicular cells of women of reproductive age.

BMPs and BMPRs in chicken ovary and effects of BMP-4 and -7 on granulosa cell proliferation and progesterone production in vitro

Bone morphogenetic proteins (BMPs) and their receptors (BMPRs) are now known to have important roles in mammalian ovarian folliculogenesis. This study determined the expression of the mRNA encoding for BMPs and their receptors in the chicken ovary and explored possible roles for them. The expression of the mRNA for BMP-2, -4, -6, -7, and BMPR-IA, -IB, and -II was determined and quantified by a semiquantitative RT-PCR. The mRNAs for all the BMPs and receptors determined were present in both the granulosa (G) and theca (T) cells of the F1, F2, and F3 follicles. All BMP mRNAs increased in G cells with follicular development, whereas only BMP-7 mRNA had this trend in the T cells. BMP-2, -4, and -6 mRNAs in T were similar between follicles. BMPR-IA mRNA was similar in F2G and F3G but lower in F1G. BMPR-IB mRNA was similar in G of all follicles, and BMPR-II mRNA increased with development. In the T, each receptor subtype showed equal distribution between follicles. mRNA levels for BMPR-IB and -II were higher in G than in T, suggesting that the G is a major target for BMPs. BMP-4 and -7 stimulated basal, IGF-I-, and gonadotropin-stimulated progesterone production by cultured G cells, with differential responses between cells from the F1 and F3/4. This suggests involvement in follicular differentiation. BMP-4 and -7 reversed the inhibitory effects of transforming growth factor (TGF)-alpha on basal and gonadotropin-stimulated G cell progesterone production, with greater effect in the F1 than in the F3/4. This effect suggests an important role for BMPs interacting with TGF-alpha in modulating the effects of gonadotropins and IGF-I on follicular differentiation. Finally, BMP-7 stimulated G cell proliferation, but BMP-4 inhibited TGF-alpha+ IGF-I- and/or FSH-stimulated G cell proliferation, suggesting a role in the control of follicular growth during development. These effects of BMP-4 and -7 on the G cell function showed relationships with the expression levels of the BMPs and the BMPR-II.

Role of estradiol-17beta on nuclear and cytoplasmic maturation of pig oocytes

The role of estradiol-17beta on nuclear and cytoplasmic maturation of pig oocytes was investigated in the present study. To determine the estradiol effect, oocytes were cultured for 42 h in a steroid free medium composed of mTCM-199 supplemented with LH, FSH and 10% charcoal extracted follicular fluid. Estradiol receptor (ER), detected by a binding assay, were present in cumulus cells and oocytes during maturation with higher levels observed at 24 h of culture in the oocytes and at 36 h in the cumulus cells. To block estradiol action an antiestrogen (1-p-dimethylaminoethoxyphenyl-1,2-diphenyl-1-butene (tamoxifen)) was added to the maturation medium at various concentrations. The percentage of treated oocytes that underwent nuclear maturation was similar (P>0.05) to the control group. Cytoplasmic maturation, determined by the ability to form female pronucleus (FPN) and male pronucleus (MPN), was not different (P>0.05) among all groups. The presence of 4-hydroxy-4-androstene-3-17-dione (4-OHA) also did not influence nuclear (P>0.05) or cytoplasmic maturation (P>0.05). The results suggest that estradiol is not involved in maturation of pig oocytes. However, the present experiment used pronuclei formation as the endpoint, no studies were done in regard to estradiol's effects on the embryonic development.

Unaltered development of the initial follicular waves and normal pubertal onset in female rats after neonatal deletion of the follicular reserve

In rats, the pool of primordial follicles is established within the first 3 d postnatally (dpn). Immediately after their differentiation, a subset of follicles begins to grow and constitutes the initial follicular waves. In this study we investigated the development of these early growing follicles after deletion of the primordial follicle pool induced by 1.5 Gy gamma-irradiation at 5 dpn. Within only 24 h, i.e. at 6 dpn, 99% of the primordial follicles disappeared, whereas most of the growing follicles remained unaffected. The study of these surviving follicles throughout the immature period has shown that their subsequent growth proceeded normally, as assessed by proliferating cell nuclear antigen immunostaining and follicular counts. No modification in the process of follicular atresia, studied by terminal deoxynucleotidyltransferase-mediated deoxy-UTP-fluorescein nick end labeling and Southern blot of DNA fragmentation analysis, was observed. Complementary analysis, by either in situ hybridization for inhibin subunits, P450 aromatase, and LH receptor mRNAs or plasma dosages of 17beta-estradiol and inhibin B, further showed that follicular maturation was unaltered. In line with these observations, pubertal onset was normal, regarding both age and ovulation rate. Nevertheless, as a consequence of the nonrenewal of the growing pool, the follicular complement was practically exhausted at puberty, and 90% of the females evidenced sterility by 4 months. Altogether, our results demonstrate that the deletion of the primordial follicle pool has induced no modification in the growth pattern of the early growing follicles that develop as their counterparts in control ovaries. Within the immature period, the initial follicular waves ensure the ovarian functionality and thus play a key role in the initiation of reproductive life.

Immunolocalization of nuclear transcription factors, DAX-1 and COUP-TF II, in the normal human ovary: correlation with adrenal 4 binding protein/steroidogenic factor-1 immunolocalization during the menstrual cycle

Steroid synthesis in the human ovary is regulated by the temporal and spatial expression of enzymes involved in each step of ovarian steroidogenesis. Recent studies have demonstrated that DAX-1 and COUP-TFII negatively regulate adrenal 4 binding protein (Ad4BP)/steroidogenic factor-1 (SF-1)-dependent transcription of steroidogenic enzymes in experimental animals. In this study the expression patterns of these proteins in human normal ovaries were examined using immunohistochemistry and compared with those of steroidogenic enzymes. In the ovarian follicle and corpora lutea, immunoreactive DAX-1 protein was detected predominantly in granulosa cells, whereas COUP-TFII was identified in thecal cells. In granulosa cells, both immunoreactive DAX-1 and Ad4BP/SF-1 protein expression increased after the preantral follicular stage. DAX-1 immunoreactivity was relatively high compared with that of Ad4BP/SF-1 in all follicular stages from premordial to nondominant. The increase in expression of Ad4BP/SF-1 immunoreactivity between follicles in the preantral and dominant stages of follicular development was greater than that in DAX-1 expression. In thecal cells, immunoreactive COUP-TFII was consistently elevated throughout the menstrual cycle, whereas Ad4BP/SF-1 immunoreactivity increased according to the development of the follicle. These results indicated that DAX-1 and COUP-TFII may play a role in the modulation of Ad4BP/SF-1-dependent transcription of steroidogenic enzymes in different cell types and follicular stages in normal cycling human ovaries.

E- and N-cadherin expression and distribution during luteinization in the rat ovary

Cadherins, a family of Ca(2+)-dependent cell adhesion molecules, play an important role in ovarian tissue remodelling processes. The aim of this study was to examine the expression pattern of E- and N-cadherin in rat preovulatory follicles, luteinizing follicles and corpora lutea. Immature female rats were treated with equine chorionic gonadotrophin (eCG) to promote preovulatory follicle development. At 48 h after eCG treatment, the rats were injected with an ovulatory dose of hCG. Ovaries were analysed by western blot analysis and immunofluorescence for E- and N-cadherin expression at 48 h after eCG injection, and at 24 and 72 h after hCG injection. Ovaries of cyclic adult rats were examined to assess whether the changes in the expression pattern of cadherin were in agreement with those of the gonadotrophin-treated rats. Finally, expression of E-cadherin in luteinizing granulosa cells in vitro was assessed by RT-PCR and western blot analysis. Immunofluorescence results indicate that E-cadherin is expressed in the theca-interstial cells surrounding preovulatory follicles. N-cadherin expression is prominent in the membrana granulosa of these follicles. The initiation of luteinization with hCG leads to a decreased expression of N-cadherin in the membrana granulosa, whereas expression of E-cadherin starts within the luteinizing follicle. Both cadherins are prominently expressed in the fully formed corpus luteum at 72 h after hCG treatment. Immunofluorescence results revealed that the patterns of E- and N-cadherin expression in the gonadotrophin-treated rats were similar to those of the cyclic adult rats. Western blot analysis reflected similar changes for N-cadherin in the ovaries of both the cyclic adults and gonadotrophin-treated rats; however, they were different in E-cadherin expression. The expression of E-cadherin mRNA and protein was induced in vitro in luteinized granulosa cells. These results support the hypothesis that modulation of cadherin expression is an integral component of remodelling processes, including corpus luteum formation, in the ovary. The results also indicate that expression of E- and N-cadherin in granulosa-lutein cells appear to be under hormonal control.

Interleukin-1 (IL-1) system gene expression in granulosa cells: kinetics during terminal preovulatory follicle maturation in the mare

BACKGROUND

A growing body of evidences suggests that the ovary is a site of inflammatory reactions, and thus, ovarian cells could represent sources and targets of the interleukin-1 (IL-1) system. The purpose of this study was to examine the IL-1 system gene expressions in equine granulosa cells, and to study the IL-1beta content in follicular fluid during the follicle maturation. For this purpose, granulosa cells and follicular fluids were collected from the largest follicle at the early dominance stage (diameter 24 +/- 3 mm) or during the preovulatory maturation phase, at T0 h, T6 h, T12 h, T24 h and T34 h after induction of ovulation. Cells were analysed by RT-PCR and follicular fluids were studied by gel electrophoresis and immunoblotting.

RESULTS

We demonstrated that interleukin-1beta (IL-1beta), interleukin-1 receptor 2 (IL-1R2) and interleukin-1 receptor antagonist (IL-1RA) genes are expressed in equine granulosa cells. We observed that the IL-1beta and IL-1RA mRNA content changed in granulosa cells during the terminal follicular maturation whereas IL-1R2 mRNA did not vary. In follicular fluid, IL-1beta content fluctuated few hours after induction of ovulation.

CONCLUSIONS

The expression of IL-1beta gene in granulosa cells and the follicular fluid IL-1beta content seem to be regulated by gonadotropins suggesting that IL-1beta could be an intermediate paracrine factor involved in ovulation.

Expression of anti-Müllerian hormone mRNA during gonadal and follicular development in the brushtail possum (Trichosurus vulpecula)

The ontogeny of anti-Müllerian hormone (AMH) gene expression in the brushtail possum during formation of the ovary and growth of follicles was examined using in situ hybridization. For comparative purposes, the expression pattern of AMH was also examined in the developing testis. In the female, AMH mRNA was observed in the ovary of 50% (3/6) of pouch young collected around the time of sexual differentiation of the gonad (Days 1-5): the signal was predominately localized to the inner-cortical and outer-medullary region of the ovary. Thereafter, AMH mRNA was not observed in the developing ovary until Days 78-113 of postnatal life when follicles first formed at the cortical-medullary boundary. At this time, AMH mRNA was observed in the cuboidal granulosa cells of some early growing (i.e. transitional) follicles and in the granulosa cells of primary follicles. Thereafter, AMH mRNA was present in granulosa cells at all subsequent stages of follicular growth (i.e. primary through antral), but not in preovulatory follicles. In all cases, once follicles had formed, AMH mRNA was limited to the granulosa cells and was not observed in the surface epithelium, stromal cells, oocytes, theca, corpus luteum, medullary cords, rete or interstitial glands. In the possum testis, Sertoli cells strongly expressed AMH around the time of sexual differentiation of the gonad, but expression decreased to very low levels in adults, suggesting that AMH plays a similar role in brushtail possums to that observed in other mammalian species. In conclusion, localization of mRNA for AMH exclusively to granulosa cells of growing follicles in the brushtail possum is consistent with a central role for this hormone in control of granulosa cell function in marsupials. In addition, expression of AMH in the developing ovary around the time of morphological sexual differentiation raises intriguing questions regarding the possible role of AMH at this time.

Relationship between intrafollicular concentrations of parathyroid hormone-related peptide (PTHrP) and steroid hormones in oestrogenic and non-oestrogenic ovarian follicles in the mare

The objective of the present study was to determine whether parathyroid hormone-related peptide (PTHrP) is present in the equine follicular fluid and if so, how it is related to the follicular development in the horse. For this purpose, ovaries were collected from 40 Thoroughbred and Thoroughbred Cross mares at slaughter during the period from February to May. Normal growing follicles were dissected from the ovaries of each mare and their diameters measured. A total of 174 follicles was used in this study. The follicular fluid was aspirated from each follicle and assayed for PTHrP, oestradiol (E), testosterone (T) and progesterone (P). The follicles were classified as either oestrogenic or non-oestrogenic if the follicular fluid content of oestradiol was >40 or <40 ng/ml, respectively. PTHrP concentrations were significantly (P<0.05) higher in oestrogenic follicles, but T and P concentrations did not differ. Furthermore, E:T ratio was significantly (P<0.05) greater in oestrogenic follicles compared to the non-oestrogenic ones. The mean diameter of oestrogenic follicles was significantly (P<0.05) greater than that of non-oestrogenic ones. The higher concentrations of PTHrP observed in the follicular fluid of healthy oestrogenic follicles suggest that it may have a role in the control of ovarian function.

Matrix metalloproteinases-2 and -9 activities in bovine follicular fluid of different-sized follicles: relationship to intra-follicular inhibin and steroid concentrations

Matrix metalloproteinases (MMPs) play very important roles in extracellular matrix (ECM) remodeling during ovarian follicular development, ovulation and atresia. The aim of the present study was to determine the content of gelatinases in follicular fluid in various sized bovine follicles. Bovine ovaries were collected from local slaughterhouse and follicular fluid from follicles of 2 to over 25 mm in diameter was collected. Gelatinase activity within the follicular fluid was analyzed by gelatin zymography. The concentration of inhibin in the follicular fluid was also measured by immunoblot analysis. The proMMP-2 and alpha-subunit (alphaN) inhibin was detected in all follicles regardless of their size. The abundance of proMMP-2 varied with follicular size, while alphaN inhibin increased significantly (P<0.01) in follicles of 10-14 and 15-20 mm in size. There was a positive and negative correlation between estradiol (E(2)) and progesterone (P(4)) concentrations with abundance of proMMP-2, respectively. Follicles of diameter over 25 mm had greater proMMP-9 activity than other follicles. These same follicles had significantly (P<0.01) lower inhibin levels than follicles of 10-14 and 15-20 mm in size. In conclusion, these results suggest a significant role of these proteases in growth and development of bovine follicle, particularly proMMP-2 and active MMP-2 activities in the follicular fluid could serve as markers of follicular health while abundance of proMMP-9 may possibly denote a follicular cyst.

Cres2 and Cres3: new members of the cystatin-related epididymal spermatogenic subgroup of family 2 cystatins

The cystatin-related epididymal spermatogenic (CRES) and recently identified testatin and cystatin T proteins define a new subgroup within the family 2 cystatins of cysteine protease inhibitors. Members of the CRES subgroup are predominantly expressed in reproductive tissues and lack critical cystatin active-site sequences implying divergent functions. To determine whether there are additional members of the subgroup, we searched nucleotide databases and identified two novel genes that we designated Cres2 and Cres3. These genes, like other subgroup members, encode proteins with four conserved cysteine residues and predicted molecular weights characteristic of family 2 cystatins but have divergent cystatin inhibitory sequences. Furthermore, the genes exhibited reproductive-specific expression with Cres2 exclusively expressed in the epithelial cells of the proximal and midcaput epididymal regions and Cres3 expressed in the proximal caput epididymal epithelium, Sertoli cells of the testis, and early follicles and corpora lutea in the ovary. Additional studies showed that, like Cres, both Cres2 and Cres3 genes are dependent on testicular factors for epididymal expression. Taken together, CRES2 and CRES3 represent new members of a subgroup of cystatin family 2 proteins that likely carry out tissue-specific functions distinct from that of typical cystatins.

Decreased expression of tumor necrosis factor-alpha-stimulated gene 6 in cumulus cells of the cyclooxygenase-2 and EP2 null mice

Ovulation, the release of fertilizable oocytes from mature follicles, involves tissue remodeling and increased prostaglandin (PG) signaling. Cyclooxygenase (COX)-2 is the rate-limiting enzyme during PG synthesis. Female mice null for either COX-2 or the PGE(2) receptor EP2 are infertile, show decreased ovulation, and exhibit abnormal cumulus expansion. Cumulus expansion is the production of a complex extracellular matrix surrounding the cumulus-oocyte complex (COC). Matrix components consist of hyaluronan, proteoglycans, and proteins with hyaluronan binding domains. One such hyaluronan binding protein is TNFalpha-stimulated gene 6 (TSG-6). By various methods, we show induction of TSG-6 and hyaluronan synthase-2 mRNA in ovaries of mice treated with pregnant mare serum gonadotropin and human chorionic gonadotropin. By in situ hybridization, we show that both genes are expressed in periantral mural granulosa cells and cumulus cells of the mouse ovary. Notably, RT-PCR and in situ hybridization show that TSG-6 mRNA but not hyaluronan synthase-2 mRNA expression is selectively reduced in cumulus cells of COX-2 and EP2 null mice. Western analysis further confirms that TSG-6 protein is reduced in isolated COCs but remains covalently associated with inter alpha-trypsin inhibitor in COX-2 null mice. These observations identify TSG-6 as a target of PG action and show that its production in ovulatory follicles is associated with proper formation of the cumulus-derived extracellular matrix.