Follicular fluid concentration of transforming growth factor-beta1 is negatively correlated with estradiol and follicle size at the early stage of development of the first-wave cohort of bovine ovarian follicles

BMP and activin receptor membrane bound inhibitor: BAMBI has multiple roles in gene expression and diseases (Review)

BMP and activin membrane-bound inhibitor (BAMBI) is a transmembrane glycoprotein, known as a pseudo-receptor for TGFβ, as, while its extracellular domain is similar to that of type I TGFβ receptors, its intracellular structure is shorter and lacks a serine/threonine phosphokinase signaling motif. BAMBI can regulate numerous biological phenomena, including glucose and lipid metabolism, inflammatory responses, and cell proliferation and differentiation. Furthermore, abnormal expression of BAMBI at the mRNA and protein levels contributes to various human pathologies, including obesity and cancer. In the present review, the structure of BAMBI is briefly introduced and its associated signaling pathways and physiological functions are described. Understanding of BAMBI structure and function may contribute to knowledge regarding the occurrence of diseases, including obesity and diabetes, among others. The present review provides a theoretical foundation for the development of BAMBI as a potential biomarker or therapeutic target.

Molecular characterization and effects of the TGIF1 gene on proliferation and steroidogenesis in yak (Bos grunniens) granulosa cells

TG interaction factor 1 (TGIF1) plays a major role in transcriptional inhibition and suppression of TGF-β signaling, but its functional roles in granulosa cells (GCs) have not been elucidated; in particular, there is no information about the yak (Bos grunniens) TGIF1 gene. Therefore, the objectives of this study were to clone yak TGIF1 and investigate TGIF1 functions in yak GCs. RT‒PCR results showed that the coding region of yak TGIF1 is 759 bp and encodes 252 amino acids. Its nucleotide sequence showed 85.24-99.74% similarity to mouse, human, pig, goat and cattle homologous genes. To explore the functional roles of TGIF1, we studied proliferation, apoptosis, cell cycle progression, steroidogenesis and the expression levels of related genes in yak GCs transfected with small interfering RNA specific to TGIF1. The results showed that TGIF1 knockdown promoted proliferation and cell cycle progression and inhibited apoptosis and estradiol (E2) and progesterone (P4) production in cultured yak GCs. Conversely, TGIF1 overexpression inhibited proliferation and cell cycle progression and stimulated apoptosis and E2 and P4 production. In addition, these functional changes in yak GCs were observed parallel to the expression changes in genes involved in the cell cycle (PCNA, CDK2, CCND1, CCNE1, CDK4 and P53), apoptosis (BCL2, BAX and CASPASE3), and steroidogenesis (CYP11A1, 3β-HSD and StAR). In conclusion, TGIF1 was relatively conserved in the course of animal evolution. TGIF1 inhibited GC viability and stimulated apoptosis and the secretion of E2 and P4 by yak GCs. Our results will help to reveal the mechanism underlying yak follicular development and improve the reproductive efficiency of female yaks.

Expression and Clinical Significance of HIF-1α in Follicular Fluid and Granulosa Cells in Infertile PCOS Patients

The present study aimed to determine the clinical predictive significance of HIF-1α in follicular development and assisted reproductive technology (ART). We collected follicular fluid (FF) and granulosa cells (GCs) from PCOS (polycystic ovary syndrome) patients (experimental group) and other patients who were infertile due to tubal factors or male factors (control group) with IVF/ICSI-ET. The localization and expression of HIF-1α in GCs were determined by immunofluorescence staining. HIF-1α protein and mRNA expression were detected by enzyme-linked immunosorbent assay and quantitative real-time PCR, respectively. To clarify the regulation of HIF-1α by TGF-β1, we added the HIF-1α-specific blocker YC-1 to GCs. The serum AMH, LH, LH/FSH, testosterone, BMI and the number of oocytes retrieved in the PCOS group were significantly higher, while the cleavage rate was significantly lower, than those in the control group. HIF-1α protein was expressed in the cytoplasm of GCs. The expression of HIF-1α protein in the FF of the PCOS group was significantly lower than that in the control group. However, the expression of HIF-1α protein in GCs between the two groups was not significantly different. HIF-1α protein was highly expressed in large FF (follicular diameter ≥ 14 mm). Compared with the control group, the expression of HIF-1α mRNA in GCs of the PCOS group was significantly lower. The results showed a significant positive correlation between HIF-1α and TGF-β1 expression. We found that both HIF-1α and TGF-β1 were involved in the development of PCOS follicular development. The mutual regulation of HIF-1α and TGF-β1 may be one of the important mechanisms of the occurrence and development of PCOS.

Meiotic Development of Canine Oocytes from Poly-Ovular and Mono-Ovular Follicles after In Vitro Maturation

Poly-ovular follicles are defined as those with more than one oocyte present in single follicles. The occurrence frequency of this follicle type is higher in canines than that in other species. This study aimed to evaluate the in vitro meiotic maturation of dog oocytes from this follicle type in comparison to those from mono-ovular follicles of various sizes (small antral, medium antral, and large antral) considering different phases of the estrus cycle (anestrus, proestrus, estrus, and diestrus). Canine oocytes were obtained separately from the poly-ovular and mono-ovular antral follicles from the ovaries of adult females. In each experimental replicate, cumulus-oocyte complexes (COCs) from poly-ovular and mono-ovular follicles were incubated in supplemented TCM-199 at 38.5 °C and 5% CO₂ for 72 h. After culturing, the meiotic development of each oocyte was evaluated using epifluorescence microscopy. Meiotic stages were classified into germinal vesicle (GV), germinal vesicle breakdown (GVBD), first metaphase (MI), and second metaphase (MII). Data were evaluated using an analysis of variance. Oocytes from poly-ovular follicles at all phases exhibited a higher (p < 0.05) percentage of oocytes arrested at the GV stage than those from mono-ovular follicles, showing the highest rate of GV in small antral follicles during anestrus. In contrast, there were no differences in MII rates (p < 0.05) in oocytes from mono-ovular and poly-ovular follicles during the estrus and diestrus phases in all sizes evaluated, with the highest MII rate in estrus. These results suggest that oocytes from poly-ovular follicles can resume meiosis at a slower rate than those from mono-ovular follicles; however, the maturation in vitro of such oocytes is possible. Furthermore, the relationship between the maturation capacity of oocytes from both poly-ovular and mono-ovular follicles depends on the ovarian cycle and follicular development.

TGFβ1 induces in-vitro and ex-vivo angiogenesis through VEGF production in human ovarian follicular fluid-derived granulosa cells during in-vitro fertilization cycle

A growing body of evidence indicates that angiogenesis in folliculogenesis contributes to oocyte developmental competence in natural and in-vitro fertilization (IVF) cycle of animals. Among the known angiogenic factors, vascular endothelial growth factor (VEGF) has an important role involved in angiogenesis. However, its expression level and regulatory mechanism in ovarian follicular fluid (FF) in patients undergoing IVF with controlled ovarian stimulation (COS) remains to be explored. In this study, the primary cultured human ovarian follicular granulosa cells (GCs) were prepared from FF and their identity was characterized by the presence of the GC specific markers. The transforming growth factor β1 (TGFβ1) was found to induce a significant increase in VEGF mRNA level and protein expression/secretion in GCs. In line with these observations, TGFβ1 could be detected in the ovarian FF, ranging from about 400 to 2000 pg/mL among three IVF patient groups with different patient's serum Anti-Müllerian hormone level. The cellular signaling analysis revealed that TGFβ1 induced VEGF production through TGFβ receptor (TGFβR), Smad2/3, PI3 K/AKT, and JNK1/2-related signaling pathways. Finally, in a functional study, the TGFβ1-primed GC VEGF secretion promoted in-vitro angiogenesis in vascular endothelial cells and ex-vivo vessel sprouting in aortic ring. Taken together, we demonstrated here that TGFβ1 expressed in ovarian FF is an inducer for promoting VEGF production in follicular GCs through TGFβR-mediated signaling pathways and the released VEGF subsequently leads to angiogenesis. This possibly contributes to oocyte developmental competence in folliculogenesis of IVF patients with a COS protocol.

miR-130a/TGF-β1 axis is involved in sow fertility by controlling granulosa cell apoptosis

TGF-β1 is a ligand of the TGF-β superfamily and an important cytokine that regulates ovarian functions including follicular development, steroid production, ovulation, luteinization, and female fertility. However, little is known about the regulation of TGF-β1 expression in ovary. Here, we identified that TGF-β1 is a functional target of miR-130a in porcine ovarian granulosa cells (GCs). The 3'-UTR sequence of TGF-β1 gene (1137 bp in length) in Large White (LW) pig was isolated, and multiple RNA regulatory elements (RREs), including several binding motifs of different miRNAs, were identified in this region. Luciferase activity assay showed that miR-130a dramatically suppresses the 3'-UTR luciferase activity of TGF-β1 gene, and further inhibits the expression of TGF-β1 in porcine GCs. FACS revealed that miR-130a acts as a pro-apoptotic factor and promotes GC apoptosis by inhibiting TGF-β1. Two novel linked mutations (-573G > A and -540T  >  C) were identified in the promoter region of ssc-miR-130a, but their polymorphisms are not associated with sow reproductive traits. Importantly, combined genotype analysis with a known mutation (c.1583 A  >  G) in the 3'-UTR of porcine TGF-β1 gene showed a significant association with reproductive performance in LW sow population. Overall, our findings defined a novel regulatory axis, miR-130a/TGF-β1 axis, which is involved in regulating sow fertility.

Candidate Gene Expression in Bos indicus Ovarian Tissues: Prepubertal and Postpubertal Heifers in Diestrus

Growth factors such as bone morphogenetic proteins 6, 7, 15, and two isoforms of transforming growth factor-beta (BMP6, BMP7, BMP15, TGFB1, and TGFB2), and insulin-like growth factor system act as local regulators of ovarian follicular development. To elucidate if these factors as well as others candidate genes, such as estrogen receptor 1 (ESR1), growth differentiation factor 9 (GDF9), follicle-stimulating hormone receptor (FSHR), luteinizing hormone receptor (LHR), bone morphogenetic protein receptor, type 2 (BMPR2), type 1 insulin-like growth factor receptor (IGFR1), and key steroidogenic enzymes cytochrome P450 aromatase and 3-β-hydroxysteroid dehydrogenase (CYP19A1 and HSD3B1) could modulate or influence diestrus on the onset of puberty in Brahman heifers, their ovarian mRNA expression was measured before and after puberty (luteal phase). Six postpubertal (POST) heifers were euthanized on the luteal phase of their second cycle, confirmed by corpus luteum observation, and six prepubertal (PRE) heifers were euthanized in the same day. Quantitative real-time PCR analysis showed that the expression of FSHR, BMP7, CYP19A1, IGF1, and IGFR1 mRNA was greater in PRE heifers, when contrasted to POST heifers. The expression of LHR and HSD3B1 was lower in PRE heifers. Differential expression of ovarian genes could be associated with changes in follicular dynamics and different cell populations that have emerged as consequence of puberty and the luteal phase. The emerging hypothesis is that BMP7 and IGF1 are co-expressed and may modulate the expression of FSHR, LHR and IGFR1, and CYP19A1. BMP7 could influence the downregulation of LHR and upregulation of FSHR and CYP19A1, which mediates the follicular dynamics in heifer ovaries. Upregulation of IGF1 expression prepuberty, compared to postpuberty diestrus, correlates with increased levels FSHR and CYP19A1. Thus, BMP7 and IGF1 may play synergic roles and were predicted to interact, from the expression data (P = 0.07, r = 0.84). The role of these co-expressed genes in puberty and heifers luteal phase merits further research.

Alterations in bone morphogenetic protein 15, growth differentiation factor 9, and gene expression in granulosa cells in preovulatory follicles of dairy cows given porcine LH

In a previous work, using porcine LH (pLH) in lieu of GnRH for synchronizing ovulation in dairy cows improved pregnancy rates without increasing plasma progesterone concentrations after ovulation. The LH profile is known to remain elevated above basal concentrations (≥1 ng/mL) for up to 20 hours in pLH-treated cows compared to less than 6 hours in GnRH-treated cows. Because LH triggers a cascade of signaling networks in the preovulatory follicle to promote final maturation and support oocyte competence, we hypothesized that dissimilar LH profiles will differentially regulate the intrafollicular factors and expression of downstream genes associated with improved oocyte competence. Specific objectives were to determine differences in the abundance of oocyte-secreted factors in the preovulatory follicular fluid and target genes in granulosa cells associated with oocyte competence, in response to exogenous porcine LH or GnRH-induced endogenous bovine LH exposure, in dairy cows. Follicular contents were aspirated by a transvaginal ultrasound-guided procedure from the preovulatory follicle of cyclic, nonlactating Holstein cows 21 ± 1 hour after administration of either pLH (25-mg) or GnRH (100-μg). Mature forms of bone morphogenetic protein 15, growth differentiation factor 9, and transforming growth factorβ1 were approximately 2-fold more abundant in pLH-treated cows which were exposed to an extended, low LH profile, than in GnRH-treated cows that had a short, high LH profile. The relative abundance of messenger RNA for cyclooxygenase-2, LH receptor, and progesterone receptor in granulosa cells, was about two-, eight-, and two-fold higher, respectively, in cows subjected to pLH than GnRH treatment. We infer that the improved pregnancy rate after pLH-induced ovulation reported previously, occurred through greater activation of intrafollicular transforming growth factor-β1 superfamily members, as these proteins promote cumulus expansion and oocyte competence.

Functional histology of the ovarian follicles as determined by follicular fluid concentrations of steroids and IGF-1 in Camelus dromedarius

Ovaries were collected from sexually mature non-pregnant dromedary she-camels. Follicles 6 to 19 mm in diameter per pair of ovaries were randomly selected and classified into clear (n = 30), or opaque (n = 14) based on macroscopic examination of the follicle surface, and then were divided into four classes: clear follicles with 6- 9.9 and 10-19 mm diameter; opaque follicles with 6- 9.9 and 10-19 mm diameter. Follicular fluid (FF) was aspirated for measurement of estradiol-17β, progesterone and IGF-I concentrations, and then a section of tissue through the exposed surface of the follicle wall was removed and fixed in and processed for histological examination. Mean (±SE) number of clear follicles observed on the ovaries that contained a large dominant follicle was less than that on the ovaries which contained a large atretic follicle (p < 0.05; 2.6 ± 1 vs 8.6 ± 0.6). In conclusion, the estrogenic large follicles have suppressive effects on the growth of other follicles.

Seminal plasma did not influence the presence of transforming growth factor-β1, interleukine-10 and interleukin-6 in porcine follicles shortly after insemination

Background

The effects of seminal plasma on the presence of the cytokines transforming growth factor (TGF)-β1, interleukin (IL)-10 and IL-6 in ovarian follicles and follicular fluid were studied shortly after insemination in gilts.

Ovaries from gilts were sampled 5–6 h after insemination with either seminal plasma (SP), fresh semen in extender (Beltsville thawing solution, BTS), spermatozoa in extender (Spz), or only BTS (control).

Results

Immunohistochemical (IHC) labeling of TGF-β1, IL-10 and IL-6 was evident in the ovarian oocytes and granulosa cells independent of stage of follicular development (antral follicles). Theca interna cells were labeled to a high degree in mature follicles. No consistent differences between treatment groups could be observed for any of the cytokines.

In follicular fluid, high concentrations of TGF-β1 were found while the levels of IL-10 and IL-6 were low. There were no differences between treatment groups.

Conclusions

Our results show a presence of the cytokines TGF-β1, IL-6 and IL-10 in oocytes, granulosa and theca cells, as well as in the fluid of mature follicles suggesting a role of these cytokines in intra-ovarian cell communication. However, treatment (SP, fresh semen in BTS, spermatozoa in BTS or BTS) did not influence the IHC-labeling pattern or the levels of these cytokines in follicular fluid shortly after insemination.

Estradiol supports in vitro development of bovine early antral follicles

Antrum formation and estradiol (E2) secretion are specific features of oocyte and granulosa cell complexes (OGCs). This study investigates the effect of E2 on the in vitro development of bovine OGCs derived from early antral follicles as well as on the expression of genes in granulosa cells (GCs). The supplementation of culture medium with either E2 or androstenedione (A4) improved the in vitro development of OGCs and the nuclear maturation of enclosed oocytes. When OGCs were cultured in medium containing A4, developmentally competent OGCs secreted more E2 than OGCs that were not competent. In addition, fulvestrant inhibited the effect of both E2 and A4 on OGCs development. Comprehensive gene expression analysis using next-generation sequence technology was conducted for the following three types of GCs: i) GCs of OGCs cultured for 4 days with E2 (1 μg/ml; E2(+)), ii) GCs of OGCs cultured for 4 days without E2 (E2(−)) or iii) OGCs that formed clear antrum after 8 days of in vitro culture in medium containing E2 (1 μg/ml; AF group). GCs of the E2(+) group had a similar gene expression profile to the profile reported previously for the in vivo development of large follicles. This genetic profile included factors implicated in the up-regulation of E2 biosynthesis and down-regulation of cytoskeleton and extracellular matrices. In addition, a novel gene expression profile was found in the AF group. In conclusion, E2 impacts the gene expression profile of GCs to support the in vitro development of OGCs.

Transforming growth factor Beta 1 stimulates profibrotic activities of luteal fibroblasts in cows

Luteolysis is characterized by angioregression, luteal cell apoptosis, and remodeling of the extracellular matrix characterized by deposition of collagen 1. Transforming growth factor beta 1 (TGFB1) is a potent mediator of wound healing and fibrotic processes through stimulation of the synthesis of extracellular matrix components. We hypothesized that TGFB1 stimulates profibrotic activities of luteal fibroblasts. We examined the actions of TGFB1 on luteal fibroblast proliferation, extracellular matrix production, floating gel contraction, and chemotaxis. Fibroblasts were isolated from the bovine corpus luteum. Western blot analysis showed that luteal fibroblasts expressed collagen 1 and prolyl 4-hydroxylase but did not express markers of endothelial or steroidogenic cells. Treatment of fibroblasts with TGFB1 stimulated the phosphorylation of SMAD2 and SMAD3. [³H]thymidine incorporation studies showed that TGFB1 caused concentration-dependent reductions in DNA synthesis in luteal fibroblasts and significantly (P < 0.05) reduced the proliferative effect of FGF2 and fetal calf serum. However, TGFB1 did not reduce the viability of luteal fibroblasts. Treatment of luteal fibroblasts with TGFB1 induced the expression of laminin, collagen 1, and matrix metalloproteinase 1 as determined by Western blot analysis and gelatin zymography of conditioned medium. TGFB1 increased the chemotaxis of luteal fibroblasts toward fibronectin in a transwell system. Furthermore, TGFB1 increased the fibroblast-mediated contraction of floating bovine collagen 1 gels. These results suggest that TGFB1 contributes to the structural regression of the corpus luteum by stimulating luteal fibroblasts to remodel and contract the extracellular matrix.

The mouse ovarian surface epithelium contains a population of LY6A (SCA-1) expressing progenitor cells that are regulated by ovulation-associated factors

The ovarian surface epithelium, a single layer of poorly differentiated epithelial cells, covers the surface of the ovary and is ruptured during ovulation. Little is known about the changes that occur in this layer before or during ovulation, and even less is known about the regenerative processes that occur after the surface is ruptured to release a mature oocyte. Recently, a population of mouse ovarian surface epithelial (MOSE) cells that exhibit progenitor/stem cell characteristics has been identified, though neither a genetic marker nor how these cells are regulated has been determined. We have identified a defined population of MOSE cells with progenitor cell characteristics that express the stem cell marker lymphocyte antigen 6 complex, locus A (LY6A; also known as stem cell antigen-1 [SCA-1]). By testing the effect of factors found in the follicular fluid at ovulation on proliferation, sphere formation, and LY6A expression, we have determined that the size of the LY6A-expressing (LY6A+) progenitor cell population is regulated by at least two ovulation-associated factors present in the follicular fluid: transforming growth factor beta 1 and leukemia-inhibitory factor. Our work has identified a population of LY6A+ MOSE progenitor cells on the surface of the ovary that may play a role in ovulatory wound healing.

TGFB1 disrupts the angiogenic potential of microvascular endothelial cells of the corpus luteum

Cyclical formation and regression of the ovarian corpus luteum is required for reproduction. During luteal regression, the microvasculature of the corpus luteum is extensively disrupted. Prostaglandin F2α, a primary signal for luteal regression, induces the expression of transforming growth factor β1 (TGFB1) in the corpus luteum. This study determined the actions of TGFB1 on microvascular endothelial cells isolated from the bovine corpus luteum (CLENDO cells). We hypothesized that TGFB1 participates in the disruption of the microvasculature during luteal regression. TGFB1 activated the canonical SMAD signaling pathway in CLENDO cells. TGFB1 (1 ng/ml) significantly reduced both basal and fetal-calf-serum-stimulated DNA synthesis, without reducing cell viability. TGFB1 also significantly reduced CLENDO cell transwell migration and disrupted the formation of capillary-like structures when CLENDO cells were plated on Matrigel. By contrast, CLENDO cells plated on fibrillar collagen I gels did not form capillary-like structures and TGFB1 induced cell death. Additionally, TGFB1 caused loss of VE-cadherin from cellular junctions and loss of cell-cell contacts, and increased the permeability of confluent CLENDO cell monolayers. These studies demonstrate that TGFB1 acts directly on CLENDO cells to limit endothelial cell function and suggest that TGFB1 might act in the disassembly of capillaries observed during luteal regression.

Effect of estrogens on boar sperm capacitation in vitro

BACKGROUND

Mammalian sperm must undergo a series of controlled molecular processes in the female reproductive tract called capacitation before they are capable of penetrating and fertilizing the egg. Capacitation, as a complex biological process, is influenced by many molecular factors, among which steroidal hormone estrogens play their role. Estrogens, present in a high concentration in the female reproductive tract are generally considered as primarily female hormones. However, there is increasing evidence of their important impact on male reproductive parameters. The purpose of this study is to investigate the effect of three natural estrogens such as estrone (E1), 17beta-estradiol (E2) and estriol (E3) as well as the synthetical one, 17 alpha-ethynylestradiol (EE2) on boar sperm capacitation in vitro.

METHODS

Boar sperm were capacitated in vitro in presence of estrogens. Capacitation progress in control and experimental samples was analyzed by flow cytometry with the anti-acrosin monoclonal antibody (ACR.2) at selected times of incubation. Sperm samples were analyzed at 120 min of capacitation by CTC (chlortetracycline) assay, immunocytochemistry and flow cytometry with anti-acrosin ACR.2 antibody. Furthermore, sperm samples and capacitating media were analyzed by immunocytochemistry, ELISA with the ACR.2 antibody, and the acrosin activity assay after induced acrosomal reaction (AR).

RESULTS

Estrogens stimulate sperm capacitation of boar sperm collected from different individuals. The stimulatory effect depends on capacitation time and is highly influenced by differences in the response to estrogens such as E2 by individual animals. Individual estrogens have relatively same effect on capacitation progress. In the boar samples with high estrogen responsiveness, estrogens stimulate the capacitation progress in a concentration-dependent manner. Furthermore, estrogens significantly increase the number of acrosome-reacted sperm after zona pellucida- induced acrosomal reaction.

CONCLUSIONS

We demonstrate here the stimulatory effect of four different estrogens on boar sperm capacitation in vitro. According to our results, there is significant difference in the response to tested estrogens at different capacitation time and among individual animals. In animals with a high response to estrogens, there is a concentration-dependent stimulation of capacitation and individual estrogens have relatively the same effect. Effects of individual estrogens, differences in the response to them by individual animals, their time and concentration-dependent outcomes further contribute to our knowledge about steroidal action in sperm.

Differential expression of focimatrix and steroidogenic enzymes before size deviation during waves of follicular development in bovine ovarian follicles

During the growth of bovine follicles, one emerges from a wave as the largest and dominant follicle. What regulates dominance is not known but candidates include oestradiol, transforming growth factor beta beta1 (TGFB1), and recently CYP11AI (cholesterol side-chain cleavage) and focal intra-epithelial matrix (focimatrix). To examine this, pairs of bovine ovaries with 2 or more follicles of equal size (>5mm) and hence in a wave before deviation, were collected at an abattoir (6.7+/-SEM 0.1mm diameter; n=14 animals, 35 follicles in total). These follicles were dissected and follicular fluid collected to measure progesterone and oestradiol concentrations. A portion of the follicle wall was processed for histological classification of health or atresia and granulosa cells were harvested for quantitative RT-PCR of focimatrix components [COL4A1 (collagen type IV alpha1), LAMB2 (laminin beta2) and HSPG2 (perlecan)], steroidogenic enzymes [CYP11A1 and CYP19A1] and TGFB1. For statistical analyses follicles within each animal were grouped into either the highest (oestradiol, CYP11A1) or lowest (TGFB1) expression (n=14) for comparison with the remaining follicles (n=21). When grouped on oestradiol no other parameters differed significantly, and when grouped on TGFB1 some parameters were different however the levels were also lower, and not higher as expected. When grouped on CYP11A1 other parameters were significantly elevated in the high CYP11A1 group (COL4A1P<0.05; LAMB2P<0.01; HSPG2P<0.01 and CYP19A1P<0.001). This suggests that steroidogenesis and focimatrix might be important in a follicle attaining dominance.

Morphological classification of bovine ovarian follicles

Follicle classification is an important aid to the understanding of follicular development and atresia. Some bovine primordial follicles have the classical primordial shape, but ellipsoidal shaped follicles with some cuboidal granulosa cells at the poles are far more common. Preantral follicles have one of two basal lamina phenotypes, either a single aligned layer or one with additional layers. In antral follicles <5 mm diameter, half of the healthy follicles have columnar shaped basal granulosa cells and additional layers of basal lamina, which appear as loops in cross section ('loopy'). The remainder have aligned single-layered follicular basal laminas with rounded basal cells, and contain better quality oocytes than the loopy/columnar follicles. In sizes >5 mm, only aligned/rounded phenotypes are present. Dominant and subordinate follicles can be identified by ultrasound and/or histological examination of pairs of ovaries. Atretic follicles <5 mm are either basal atretic or antral atretic, named on the basis of the location in the membrana granulosa where cells die first. Basal atretic follicles have considerable biological differences to antral atretic follicles. In follicles >5 mm, only antral atresia is observed. The concentrations of follicular fluid steroid hormones can be used to classify atresia and distinguish some of the different types of atresia; however, this method is unlikely to identify follicles early in atresia, and hence misclassify them as healthy. Other biochemical and histological methods can be used, but since cell death is a part of normal homoeostatis, deciding when a follicle has entered atresia remains somewhat subjective.

Transforming growth factor-β1 inhibits luteinization and promotes apoptosis in bovine granulosa cells

We have previously shown that TGFB1 inhibits estradiol (E2) and progesterone (P4) biosynthesis in FSH-stimulated bovine granulosa cells by selective inhibition of steroidogenic enzymes. The objective of this study was to assess the effects of TGFB1 on E2and P4steroidogenesis in bovine granulosa cells cultured in the absence of FSH and to measure the effects of TGFB1 on cell proliferation and apoptosis in the presence and absence of FSH. Bovine granulosa cells from 2 to 5 mm follicles were cultured in serum-free medium for 2–6 days. In the absence of FSH, the secretion of P4increased with time in culture (P<0.05). Addition of TGFB1 for 6 days decreased P4secretion and mRNA levels of the P4synthesis-associated genesSTAR,CYP11A1,HSD3B1, andGSTA(P<0.05). In the absence of FSH, the secretion of E2decreased and addition of TGFB1 for 6 days partially reversed this decline and stimulated E2biosynthesis,CYP19A1andHSD17B1mRNA levels and CYP19A1 activity (P<0.05). Conversely, TGFB1 did not affectHSD17B7expression and HSD17B-reducing activity. TGFB1 decreased the proportion of cells in the G0/G1 and S+G2/M phases in FSH-stimulated and unstimulated granulosa cells (P<0.05). Furthermore, in the presence or absence of FSH, TGFB1 increased the proportion of cells in apoptosis measured by propidium iodide staining and flow cytometry and confirmed by increased levels of cleaved caspase-3 (P<0.05). Our results therefore indicate that TGFB1 inhibits luteinization in cultured bovine granulosa cells while maintaining an estrogenic phenotype, and this effect was associated with increased apoptosis.

Role of transforming growth factor-β1 in gene expression and activity of estradiol and progesterone-generating enzymes in FSH-stimulated bovine granulosa cells

Survival and inhibitory factors regulate steroidogenesis and determine the fate of developing follicles. The objective of this study was to determine the role of transforming growth factor-β1 (TGFB1) in the regulation of estradiol-17β (E2) and progesterone (P4) secretion in FSH-stimulated bovine granulosa cells. Granulosa cells were obtained from 2 to 5 mm follicles and cultured in serum-free medium. FSH dose (1 and 10 ng/ml for 6 days) and time in culture (2, 4, and 6 days with 1 ng/ml FSH) increased E2secretion and mRNA expression of E2-related enzymes cytochrome P450 aromatase (CYP19A1) and 17β-hydroxysteroid dehydrogenase type 1 (HSD17B1), but notHSD17B7. TGFB1 in the presence of FSH (1 ng/ml) inhibited E2secretion, and decreased mRNA expression of FSH receptor(FSHR),CYP19A1, andHSD17B1, but notHSD17B7. FSH dose did not affect P4secretion and mRNA expression of 3β-hydroxysteroid dehydrogenase (HSD3B) and α-glutathioneS-transferase (GSTA), but inhibited the amount of steroidogenic acute regulatory protein(STAR)mRNA. Conversely, P4and mRNA expression ofSTAR, cytochrome P450 side-chain cleavage(CYP11A1),HSD3B, andGSTAincreased with time in culture. TGFB1 inhibited P4secretion and decreased mRNA expression ofSTAR,CYP11A1,HSD3B, andGSTA. TGFB1 modified the formation of granulosa cell clumps and reduced total cell protein. Finally, TGFB1 decreased conversion of androgens to E2, but did not decrease the conversion of estrone (E1) to E2and pregnenolone to P4. Overall, these results indicate that TGFB1 counteracts stimulation of E2and P4synthesis in granulosa cells by inhibiting key enzymes involved in the conversion of androgens to E2and cholesterol to P4without shutting down HSD17B reducing activity and HSD3B activity.

Evaluation of oocyte quality: morphological, cellular and molecular predictors

Mounting evidence that oocyte quality profoundly affects fertilisation an d subsequent embryo development drives the continued search for reliable predictors of oocyte developmental competence. In the present review, we provide an overall summary and analysis of potential criteria that can be used to evaluate oocyte quality. These criteria are specifically classified as morphological and cellular/molecular predictors. Traditional methods for the evaluation of oocyte quality are based on morphological classification of thefollicle, cumulus-oocytecomplex, polar body and/or meiotic spindle. Although the use of morphological characteristics as predictors of oocyte quality is controversial, such a grading system can provide valuable information for the preselection of oocytes with higher developmental competence and, therefore, may maximise embryo developmental outcome. Several intrinsic markers (such as mitochondrial status and glucose-6-phosphate dehydrogenase 1 activity) and extrinsic markers (such as apoptosis of follicular cells and levels of the transforming growth factor-beta superfamily in follicular fluid or serum) have also been reported as useful indicators of oocyte competence and embryo quality. Compared with the morphological parameters, these cellular and molecular predictors of oocyte quality may prove to be more precise and objective, although further studies and refinement of techniques are needed.

Evidence of a local negative role for cocaine and amphetamine regulated transcript (CART), inhibins and low molecular weight insulin like growth factor binding proteins in regulation of granulosa cell estradiol production during follicular waves in cattle

The ability of ovarian follicles to produce large amounts of estradiol is a hallmark of follicle health status. Estradiol producing capacity is lost in ovarian follicles before morphological signs of atresia. A prominent wave like pattern of growth of antral follicles is characteristic of monotocous species such as cattle, horses and humans. While our knowledge of the role of pituitary gonadotropins in support of antral follicle growth and development is well established, the intrinsic factors that suppress estradiol production and may help promote atresia during follicular waves are not well understood. Numerous growth factors and cytokines have been reported to suppress granulosa cell estradiol production in vitro, but the association of expression of many such factors in vivo with follicle health status and their physiological significance are not clear. The purpose of this review is to discuss the in vivo and in vitro evidence supporting a local physiological role for cocaine and amphetamine regulated transcript, inhibins and low molecular weight insulin like growth factor binding proteins in negative regulation of granulosa cell estradiol production, with emphasis on evidence from the bovine model system.

Expression of protease nexin-1 and plasminogen activators during follicular growth and the periovulatory period in cattle

Extracellular matrix remodeling occurs during ovarian follicular development, mediated by plasminogen activators (PAs) and PA inhibitors including protease nexin-1 (PN-1). In the present study we measured expression/activity of the PA system in bovine follicles at different stages of development by timed collection of ovaries during the first follicular wave and during the periovulatory period, and in follicles collected from an abattoir. The abundance of mRNA encoding PN-1, tissue-type PA (tPA), urokinase (uPA) and PA inhibitor-1 (PAI-1) were initially upregulated by human chorionic gonadotropin (hCG) in bovine preovulatory follicular wall homogenates. PN-1, PAI-1 and tPA mRNA expression then decreased near the expected time of ovulation, whereas uPA mRNA levels remained high. PN-1 concentration in follicular fluid (FF) decreased and reached the lowest level at the time of ovulation, whereas plasmin activity in FF increased significantly after hCG. Follicles collected from the abattoir were classified as non-atretic, early-atretic or atretic based on FF estradiol and progesterone content: PN-1 protein levels in FF were significantly higher in non-atretic than in atretic follicles, and plasmin activity was correspondingly higher in the atretic follicles. No changes in PN-1 levels in FF were observed during the growth of pre-deviation follicles early in a follicular wave. These results indicate that PN-1 may be involved in the process of atresia in non-ovulatory dominant follicles and the prevention of precocious proteolysis in periovulatory follicles.