Effects of fetal bovine serum, FSH and 17β-estradiol on the culture of bovine preantral follicles

Addition of synthetic polymers to a conventional cryoprotectant solution in the vitrification of bovine ovarian tissue

Some synthetic polymers can be used at low concentrations to reduce the toxicity of conventional cryoprotectant agents. In this study we investigated whether the addition of synthetic polymers to a conventional cryoprotectant solution would improve the cryopreservation of bovine ovarian tissue. Freshly collected ovaries from ten adult crossbred cows were incised using a scalpel in the frontal section. From each cow, ovarian cortical slices of 1 mm thickness were divided into 30 fragments of 3 × 3 mm, of which 10 served as fresh controls, 10 were vitrified with conventional cryoprotectant agents (2.93 M glycerol, 27 % w/v; 4.35 M ethylene glycol, 27 % w/v), and 10 were vitrified using the same cryoprotectant agents in addition to synthetic polymers (0.2 % PVP K-12, 0.2 % SuperCool X-1000 ™ w/v and 0.4 % SuperCool Z-1000 ™ w/v). After warming, histology was used to assess follicular quantity and integrity, while in vitro culture of mechanically isolated follicles encapsulated in an alginate matrix was performed for 15 days to assess their growth and hormonal production. Vitrified ovarian tissues presented abnormal morphology, a higher percentage of atretic follicles, and their isolated follicles had lower survival rates and lower frequency of antrum formation during in vitro culture compared to those from fresh tissue. At the end of culture, the follicles that had been cryopreserved produced less estradiol and progesterone than the fresh ones. The addition of synthetic polymers during tissue vitrification did not modify any of these parameters. We conclude that, under the conditions of this study, the use of this combination of synthetic polymers for tissue vitrification did not enhance the preservation of the morphological or functional integrity of bovine ovarian follicles.

The association of serum phthalate metabolites with biomarkers of ovarian reserve in women of childbearing age

Phthalates (PAEs) are widely used plasticizers drawing increasing concern due to reproductive toxicity. However, studies on serum PAEs metabolites (mPAEs) and their associations with human ovarian function remain very scarce. In this study, from April 2019 to August 2020, a total of 297 women of childbearing age were recruited in Tianjin, China. Eleven mPAEs were analyzed in serum samples and eight mPAEs were detected at frequencies > 65% with median concentrations of 0.43-15.3 ng/mL. In multinomial logistic analysis, an increase in serum mono (2-isobutyl) phthalate (miBP) was associated with decline in antral follicle count (AFC) (OR=1.26, 95% CI: 0.99, 1.61) and 5-mono-(2-ethyl-5-hydroxyhexyl) phthalate (mEHHP) was significantly associated with AFC increase (OR=1.43, 95% CI: 1.06, 1.92), which were aligned with the associations found between mPAEs and AMH through generalized linear regression. In multiple linear regression models, per 10% increase in serum mono (2-ethylhexyl) phthalate (mEHP), mono (2-ethyl-5-oxohexyl) phthalate (mEOHP) (oxo-mEHP), and principal component 1 featured for high concentrations of mono-n-butyl phthalate (mBP), miBP and mEHP were associated with 0.15 (95% CI: -0.29, -0.02), 0.01 (95% CI: -0.01, 0.00) and 0.01 (95% CI: -0.02, 0.00) ln-unit decrease in estradiol (E2) levels, respectively, while mono-[(2-carboxymethyl) hexyl] phthalate (mCMHP) (carboxymethyl-mEHP) was positively associated with 0.05 ln-unit increase of E2 (95% CI: 0.02, 0.08). The observed negative associations between mPAEs and the Anti-Müllerian hormone (AMH) also aligned with the change in AFC. Generalized linear regression also revealed nonlinear associations between mono-ethyl phthalate (mEP), mCMHP and follicle-stimulating hormone (FSH). Overall, serum mEHP and its metabolites were negatively associated with E2. miBP was negatively associated with AFC. The nonlinear associations between mPAEs and FSH, and AMH need further study.

Resurrecting biodiversity: advanced assisted reproductive technologies and biobanking

Biodiversity is defined as the presence of a variety of living organisms on the Earth that is essential for human survival. However, anthropogenic activities are causing the sixth mass extinction, threatening even our own species. For many animals, dwindling numbers are becoming fragmented populations with low genetic diversity, threatening long-term species viability. With extinction rates 1000–10,000 times greater than natural, ex situ and in situ conservation programmes need additional support to save species. The indefinite storage of cryopreserved (−196°C) viable cells and tissues (cryobanking), followed by assisted or advanced assisted reproductive technology (ART: utilisation of oocytes and spermatozoa to generate offspring; aART: utilisation of somatic cell genetic material to generate offspring), may be the only hope for species’ long-term survival. As such, cryobanking should be considered a necessity for all future conservation strategies. Following cryopreservation, ART/aART can be used to reinstate lost genetics back into a population, resurrecting biodiversity. However, for this to be successful, species-specific protocol optimisation and increased knowledge of basic biology for many taxa are required. Current ART/aART is primarily focused on mammalian taxa; however, this needs to be extended to all, including to some of the most endangered species: amphibians. Gamete, reproductive tissue and somatic cell cryobanking can fill the gap between losing genetic diversity today and future technological developments. This review explores species prioritisation for cryobanking and the successes and challenges of cryopreservation and multiple ARTs/aARTs. We here discuss the value of cryobanking before more species are lost and the potential of advanced reproductive technologies not only to halt but also to reverse biodiversity loss.

Follicle-stimulating hormone mediates the consumption of serum-derived glycogen by bovine cumulus-oocyte complexes during in vitro maturation

Background and Aim:

Oocyte in vitro maturation (IVM) is an appealing approach for several assisted reproductive technologies and dissecting oocyte maturation. Nonetheless, IVM leads to lower developmental competence and usually relies on undefined, serum-containing media. Therefore, biochemical profiling aimed to explore fluctuations in IVM media content during the acquisition of oocyte developmental competence.

Materials and Methods:

Bovine cumulus-oocyte complexes (COCs) underwent IVM in TCM199 medium with Earle’s salts, supplemented with 2.0 mM L-glutamine, 10% fetal bovine serum, antibiotics, and 0.05 IU/mL porcine follicle-stimulating hormone (FSH+) or vehicle control (CTL) medium for 22 h.

Results:

FSH withdrawal (CTL) diminished several processes associated with the acquisition of oocyte developmental competence, such as reduced cumulus cell expansion, diminished estradiol synthesis (FSH+: 116.0±0.0 pg/mL vs. CTL: 97.6±18.0 pg/mL), and lower oocyte nuclear maturation rate (FSH+: 96.47% vs. CTL: 88.76%). Fresh media formulations (i.e., TCM199 with FSH or vehicle) were indistinguishable under biochemical profiling threshold conditions. Biochemical profiling showed similar total protein and lipid concentrations between groups. Further, total sugar concentrations diminished from fresh media to their post-IVM counterparts, albeit in an FSH-independent manner. Glycogen concentrations remained unaltered after IVM within CTL media, albeit were substantially lower after IVM under FSH+ conditions.

Conclusion:

FSH mediates the consumption of serum-derived glycogen by bovine COCs during IVM and implies that serum-free media should contain increased glucose concentrations to facilitate the acquisition of oocyte developmental competence.

In vitro growth of bovine oocytes in oocyte-cumulus cell complexes and the effect of follicle stimulating hormone on the growth of oocytes

Several successful in vitro culture experiments have used oocyte-cumulus cell-mural granulosa cell complexes (OCGCs) from early antral follicles (0.5-0.7 mm) for the growth of bovine oocytes. However, in studies related to in vitro oocyte maturation and in vitro embryo production, oocyte-cumulus cell complexes (OCCs) that have no mural granulosa cells have been widely used instead of OCGCs. The purpose of this study was to determine whether cumulus cells alone support oocyte growth. First, OCCs and OCGCs were cultured in vitro for 14 days to compare the integrity of the complexes as well as antrum formation. After 14 days, the diameter and meiotic competence of oocytes in OCCs and OCGCs were examined. Oocytes in OCCs grew fully and acquired meiotic competence similar to OCGCs, whereas antrum formation occurred later in OCCs as compared to OCGCs. Subsequently, the effects of follicle stimulating hormone (FSH) on in vitro growth of OCCs were examined for 14 days. When FSH was added to the culture medium, OCCs formed antrum-like structures one day earlier than those cultured without FSH. Oocytes cultured with 1 mIU/ml FSH grew fully and acquired meiotic competence. In contrast, when oocytes were cultured in media containing high concentrations of FSH, some of the OCCs collapsed and the number of degenerated oocytes increased. In conclusion, bovine oocytes in OCCs grow and acquire meiotic competence similar to OCGCs and, 1 mIU/ml FSH supports the development of OCCs and oocyte growth as observed in our culture system.

Supplementation of culture medium with knockout serum replacement improves the survival of bovine secondary follicles when compared with other protein sources during in vitro culture

The present study evaluated the effect of knockout serum replacement (KSR), fetal bovine serum (FBS) and bovine serum albumin (BSA) on the viability and growth of bovine secondary follicles cultured in vitro for 12 days. To this end, secondary follicles were isolated (185-202 μm) and cultured in vitro in TCM-199+ medium supplemented with KSR (5% and 10%), FBS (5% and 10%) or BSA (3 mg/ml) at 38.5°C with 5% CO2 in air. Follicular diameters were evaluated on days 0, 4, 8 and 12. After 12 days of culture, follicular survival analysis was performing by using calcein-AM and ethidium homodimer. Before and after culture, follicles were fixed in paraformaldehyde for histological evaluation. Follicular diameter at different days of culture were compared using the Kruskal-Wallis test, while the percentages of viable follicles were analyzed by chi-squared test (P < 0.05). Results showed that follicles cultured in the presence of KSR at both concentrations presented higher follicular survival rates than those cultured in control medium alone or supplemented with FBS or BSA. Conversely, the presence of KSR, BSA or FBS did not increase follicular diameter after 12 days of culture. Histology analysis showed that, among the tested treatments, follicles cultured in the presence of KSR had preserved rounded oocytes, juxtaposed granulosa cells and intact basal membrane. In conclusion, supplementation of culture medium with KSR increases the follicular survival of bovine secondary follicles cultured in vitro.

Influence of follicle-stimulating hormone concentrations on the integrity and development of bovine follicles cultured in vitro

This study investigated the in vitro culture of bovine follicles included in ovarian tissue for 2 or 6 days (D2 or D6), with the addition of different concentrations of follicle-stimulating hormone (FSH) (0, 10, 50, 100 or 200 ng/ml). Data were compared for follicular development, morphological integrity and diameter of follicles and oocytes. Ovaries (n = 10) from Nelore cows (n = 5) were divided into fragments (n = 11 per ovary) and were immediately fixed in Bouin’s solution (D0) or were individually cultured for 2 or 6 days in one of the described concentrations of FSH and then processed for histology. Compared with the rates of follicular development at D2 for minimal essential medium (MEM) (75.0%) and 50 ng/ml of FSH (71.1%), the best rates of follicular development at D2 were obtained with 10 (84.7%), 100 (87.5%) and 200 ng/ml of FSH (85.0%; P<0.05). After 6 days of cultivation, there were no differences among treatments regarding follicular growth. The morphological integrity of preantral follicles was better maintained by 100 ng/ml FSH for 2 and 6 days of cultivation (51.2 and 40.4%, respectively; P<0.05) than that for MEM (D2: 30.9%, D6: 20.8%), 10 (D2: 39.2%, D6: 22.8%), 50 (D2: 30.4%, D6: 28.8%) and 200 ng/ml FSH (D2: 45.2%, D6: 36.8%). FSH at 100 ng/ml provided the highest mean diameter averages: 34.5±10.8 µm at D2 and 33.2±12.5 µm at D6 (P<0.05). We concluded that the medium supplemented with 100 ng/ml FSH during in vitro culture provided appropriate conditions for the development and morphological integrity of preantral follicles in cattle.

Hormonal changes and folliculogenesis in female offspring of rats exposed to cadmium during gestation and lactation

It has been suggested that the toxic effects of cadmium (Cd) may disrupt ovarian and uterine functions in adults. However, Cd exposure during gestation and lactation and its effects on the reproductive development in female offspring is still not clear, and the mechanisms underlying exposure toxicology remain mostly unexplored. To investigate how Cd exposure of female rats (F0) during gestation and lactation affects the reproductive development of their female offspring, we studied the steroidogenesis, folliculogenesis, puberty onset, and litter size of the first (F1) and second (F2) filial generations following F0 female rats which had been exposed to CdCl₂. The mechanisms related to the early onset of puberty induced by such exposure in female offspring were explored. Maternal exposure to Cd dramatically increased the biosynthesis of steroid hormones in F1 female offspring by the activation of cAMP/PKA pathway and up-regulated expression of steroidogenesis related proteins such as StAR, CYP11A1, 3β-HSD and CYP19A1. The high levels of steroid hormones contributed to an early puberty onset, promoted the differentiation and maturation of follicles, and led to the proliferation of endometrium that resulted in a uterus weight gain. The increased number of antral follicles eventually caused a big litter size. Despite of being free from additional Cd exposure, the levels of CYP11A1 and CYP19A1 in the ovaries of F2 female rats were also high, which resulted in a high concentration of serum progesterone. These results suggested that hormonal changes induced by exposure to Cd in utero might have a lasting effect beyond the first generation. These findings may help to better understand the origin of female sexual dysfunction in the developmental stages in general.

The Growth of Preantral Follicles and the Impact of Different Supplementations and Circumstances: A Review Study with Focus on Bovine and Human Preantral Follicles

One of the most important concerns cancer survivors face is fertility. Current treatment modalities often result in damage to the reproductive system. Different options have been proposed to preserve the fertility of affected women, and many attempts have been made to improve their chance of childbearing after therapy. Cryopreservation of ovarian tissue and follicles before the onset of cancer treatment and then either transplantation of ovarian tissue or culture of ovarian tissue and individual follicles in vitro is a commonly cited approach. Extensive research is being done to design an optimal condition for the culture of ovarian follicles. Improving follicle culture systems by understanding their actual growth needs might be a crucial step toward fertility preservation in cancer patients. This review article will try to provide a summary of the role of different factors and conditions on growth of human and bovine preantral follicles in vitro.

Mouse preantral follicle growth in 3D co-culture system using human menstrual blood mesenchymal stem cell

Follicle culture provides a condition which can help investigators to evaluate various aspects of ovarian follicle growth and development and impact of different components and supplementations as well as presumably application of follicle culture approach in fertility preservation procedures. Mesenchymal Stem Cells (MSCs), particularly those isolated from menstrual blood has the potential to be used as a tool for improvement of fertility. In the current study, a 3D co-culture system with mice preantral follicles and human Menstrual Blood Mesenchymal Stem Cells (MenSCs) using either collagen or alginate beads was designed to investigate whether this system allows better preantral follicles growth and development. Results showed that MenSCs increase the indices of follicular growth including survival rate, diameter, and antrum formation as well as the rate of in vitro maturation (IVM) in both collagen and alginates beads. Although statistically not significant, alginate was found to be superior in terms of supporting survival rate and antrum formation. Hormone assay demonstrated that the amount of secreted 17 β-estradiol and progesterone in both 3D systems increased dramatically after 12 days, with the highest levels in system employing MenSCs. Data also demonstrated that relative expression of studied genes increased for Bmp15 and Gdf9 and decreased for Mater when follicles were cultured in the presence of MenSCs. Collectively, results of the present study showed that MenSCs could improve indices of follicular growth and maturation in vitro. Further studies are needed before a clinical application of MenSCs-induced IVM is considered.

Hormonal behavior correlates with follicular recruitment at mid-gestation in the South American plains vizcacha, Lagostomus maximus (Rodentia, Caviomorpha)

In mammals, hormonal regulation during gestation is crucial for embryo implantation and pregnancy success. This regulation is controlled through the level of progesterone (P4) that blocks the activity of the hypothalamic-hypophyseal-gonadal (HHG) axis. Previous studies in the pregnant South American plains vizcacha, Lagostomus maximus, have shown that the HHG axis activates around mid-gestation, promoting pre-ovulatory follicle formation. However, the characterization of the hormonal dynamics throughout gestation and its ovarian correlation has not been studied in depth. We studied the ovarian dynamics of L. maximus and its correlation with the hormonal profile during gestation, analyzing serum levels of P4, 17β-estradiol (E2), 4Δ-androstenedione (A4), luteinizing hormone (LH) and follicle stimulating hormone (FSH) as well as the ovarian distribution and expression of their receptors. Additionally, we have analyzed the folliculogenesis and accessory corpora lutea (ACL) formation. P4 showed two concentration peaks reaching its highest level at mid-gestation decreasing at 91-100days post-coitum. P4 decrease is followed by an increase of circulating levels of A4, E2, FSH and LH and with an elevated number of antral/pre-ovulatory follicles which express PGR, ESR1, ESR2, AR, LHR and FSHR. In addition, ACL with oocyte retention and cytoplasmic lipid droplets in luteal cells were detected at this time point. These results show that in L. maximus the decrease of P4 level from mid-gestation enables follicular recruitment until pre-ovulatory stage and the development of functional ACL.

Expression of kit ligand and insulin-like growth factor binding protein 3 during in vivo or in vitro development of ovarian follicles in sheep

Expression of Kit ligand (KL) and insulin-like growth factor binding protein (IGFBP3) genes was studied at different in vivo and corresponding in vitro stages of development of the ovarian follicles in sheep. The expression of both KL and IGFBP3 was significantly higher in the primordial follicles relative to any other stage of development. Compared to the other stages, the KL expression in the cumulus cells from in vivo grown large antral follicles and that of IGFBP3 in COCs' isolated from large antral follicles matured in vitro for 24 hr were significantly higher. In the oocytes from in vivo grown ovarian follicles, the expression of KL was the same at all the stages of development. Insulin-like growth factor binding protein 3 expression was also the same in the oocytes at all the stages of the development except for a significantly lower expression in those from antral follicles. The expression of KL in the cumulus cells decreased significantly in the in vitro grown early antral follicles but did not change further as the development progressed. The expression of IGFBP3 in the cumulus cells from in vitro grown ovarian follicles appeared to increase as the development progressed although the increase was not significant between any two consecutive stages of development. In the oocytes in in vitro grown ovarian follicles, the expression levels of KL and IGFBP3 genes did not change with development. It is concluded that (i) KL and IGFBP3 genes follow specific patterns of expression during ovarian folliculogenesis and (ii) in vitro culture of preantral follicles compromises the development potential through alterations in the stage-specific patterns of expression of these and other developmentally important genes.

New approaches to increasing oocyte yield from ruminants

Artificial insemination, superovulation and embryo transfer have had beneficial impacts on animal production but a limiting factor to realizing the full potential of these techniques and of other reproductive technologies is the availability of fertile oocytes. To overcome this problem, methods for maturing oocytes in vitro (IVM) have been developed. The production of bovine embryos by IVM is in commercial use but the rate of success and quality of embryos is low. The lack of success may be due to the quality of oocytes that are being matured and it would be preferable to utilize the abundant source of immature oocytes from preantral and primordial follicles by developing systems for in vitro growth (IVG). Several culture systems that utilize early growing follicles as a source of oocytes have been developed for laboratory species and these have been successful in producing live young. IVG in association with IVM and cryopreservation have the potential to maximize the genetic potential of high genetic merit females and shorten generation intervals. This paper presents the current status of technology for the in vitro growth and development of immature oocytes, in vitro maturation and cryopreservation of germ cells in domestic ruminants.

Ovarian follicle development in vitro and oocyte competence: advances and challenges for farm animals

During the last 2 decades, research on in vitro preantral follicle growth and oocyte maturation has delivered fascinating advances concerning the knowledge of processes regulating follicle growth and the developmental competence of oocytes. These advances include (1) information about the role of several hormones and growth factors on in vitro activation of primordial follicles; (2) increased understanding of the intracellular pathway involved in the initiation of primordial follicle growth; (3) the growth of primary and secondary follicles up to antral stages; and (4) production of embryos from oocytes from in vitro grown preantral follicles. This review article describes these advances, especially in regard farm animals, and discusses the reasons that limit embryo production from oocytes derived from preantral follicles cultured in vitro.

What Ethics for Bioart?

Living artworks created with biotechnology raise a range of ethical questions, some of which are unprecedented, others well known from other contexts. These questions are often discussed within the framework of bioethics, the ethics of the life sciences. The basic concern of institutionalised bioethics is to develop and implement ethical guidelines for ethically responsible handling of living material in technological and scientific contexts. Notably, discussions of ethical issues in bioart do not refer to existing discourses on art and morality from the field of aesthetics. The latter framework is primarily concerned with how the moral value of an artwork affects its artistic value. The author argues that a successful integration of these two frameworks will make possible an ethics of bioart that is adequate to its subject matter and relevant for practice. Such an integrated approach can give increased depth to understandings of ethical issues in bioart, inspire new ways of thinking about ethics in relation to art in general and give novel impulses to bioethics and technology assessment. Artworks by the Tissue Culture and Art Project and their reception serve as the empirical starting point for connecting perspectives in art with those of bioethics, developing an ethics for bioart. The author suggests that consideration of the effect of these artworks is vital in validating ethically problematical applications of biotechnology for art. It is argued that the affective, visceral qualities of living artworks may spur the audience to adjust, revise or develop their personal ethical framework.

Hypoxia limits mouse follicle growth in vitro

Ovarian follicle culture is useful for elucidation of factors involved in the regulation of follicular function. We examined the effects of gas phase oxygen concentration, an oil overlay, serum type and medium supplementation with FSH, insulin-transferrin-selenium (ITS) and l-ascorbic acid on cultured preantral mouse follicle growth in a spherical, non-attached follicle culture system. Follicle growth in 5% oxygen was significantly (P < 0.01) inferior to growth in 20% oxygen in terms of follicle diameter. This was likely due to hypoxia, as evidenced by significantly (P < 0.05) increased follicle secretion of vascular endothelial growth factor (VEGF), a marker of cell hypoxia. Follicular growth was not (P > 0.05) affected by an oil overlay, ITS supplementation or serum type. Culture in medium with 5% mouse serum, 1 IU mL-1 FSH, 25 μg mL-1 l-ascorbic acid and 20% oxygen without an oil overlay supported the growth of follicles to a maximum diameter of 380 μm in 6 days. Compared with mature preovulatory mouse follicles in vivo that often have diameters >500 μm within the same time frame, in vitro-grown follicles clearly exhibit limited growth. Thus, adequate oxygenation is an essential factor in the process of optimising follicle growth.

In vitro culture of bovine preantral follicles: a review

Preantral follicles are the majority of the ovarian follicle population and their use as a source of homogeneous oocytes for bovine reproductive biotechnologies could result in a substantial advance in this field. However, while in other species embryos and offspring have been produced, in bovine species the results have been limited to the follicular activation of small (primordial) preantral follicles and formation of early antral follicles from large (secondary) preantral follicles after in vitro culture. Therefore, this review will highlight the basic aspects of bovine folliculogenesis by focusing on preantral follicles, the methods of harvesting preantral follicles, the main results from in vitro follicular culture during the last 20 years, and the potential candidate substances (basic supplements, growth factors, and hormones) for improving the efficiency of in vitro follicle growth.

Integration of physiological mechanisms that influence fertility in dairy cows

Fertility in dairy cows has been declining for the past three decades. Genetic selection for increased milk production has been associated with changes in key metabolic hormones (growth hormone, insulin, IGF and leptin) that regulate metabolism by homoeostasis and homeorhesis. These metabolic hormones, particularly insulin, provide signals to the reproductive system so that regulation of ovarian function is coordinated with changes in metabolic status. Studies have shown, for example, that increasing circulating insulin concentrations during the early post partum period can advance the resumption of oestrous cycles by enhancing follicular growth. However, high concentrations of insulin can be detrimental to the developmental competence of oocytes, which is also influenced by the supply of fatty acids at the systemic level and at the ovarian level. Insulin status is also associated with the incidence and characteristics of abnormal ovarian cycles. These changes can occur without significant variation in circulating gonadotrophin concentrations. This suggests that additional factors, such as peripheral metabolites, metabolic hormones and locally produced growth factors, may have a modulating role. Recent evidence has demonstrated that ovarian responses to metabolic signals and nutrient profile vary according to the stage of the reproductive cycle. Improved understanding of this multifactorial process enables nutrition to be matched to genotype and milk production, with a positive impact on pregnancy rate.

Isolation and culture of preantral follicles for retrieving oocytes for the embryo production: present status in domestic animals

The development of efficient ovarian preantral follicle (PF) isolation and culture systems provide a large number of oocytes for the manipulation and embryo production. It also helps for understanding the mechanisms of follicle and oocyte development. Isolation and culture protocols for PFs were developed for many domestic species like cattle, buffalo, sheep, goat, pig, horse, camel, dog and cats; however, embryo production from oocytes derived from in vitro grown PFs was reported only in pigs, buffalo, sheep and goat. The rate of oocyte maturation from PFs grown in vitro is low and requires considerable research. This paper presents an overview of isolation and culture systems of PFs that have been developed for domestic species (cattle, buffalo, sheep, goat, pigs, horse, camel, dog and cat) along with the current status of progress achieved in the direction of producing embryos using PFs as the source of oocyte in these species.

Follicle growth and oocyte developmental competence in cows with liver damage

Follicle growth, oocyte quality or oocyte growing environment (follicular fluid) were evaluated in cows with severe liver damage (haemorrhage, telangiectasis, cholangitis and abscess) that were visually diagnosed at the slaughterhouse. Holstein cows aged 40-90 months with either a healthy liver (HL cow) or damaged liver (DL cow) were selected as donors. Follicle development kinetics was evaluated by counting the follicles at various developmental stages. In addition, the biochemical characteristics of the follicular fluids, developmental competence of preantral follicles cultured for 16 days in vitro and the ability of oocytes to develop to the blastocyst stage 8 days after fertilization were examined. DL cows had fewer secondary follicles than HL cows, and the correlation between the number of secondary follicles and the number of primary follicles differed among DL and HL cows. The follicular fluid of DL cows contained significantly lower levels of albumin and a higher total protein content than that of HL cows. Oocyte nuclear maturation assessed at 5, 16 and 21 h after beginning of culture was slower in DL cows than in HL cows, although the final maturation rates did not differ. The rate of polyspermic fertilization was significantly higher and the proportion of cleavage at 48 h after insemination and blastulation lower in DL cows compared with HL cows. When preantral follicles were cultured in vitro, the rate of follicles with normal morphology was lower in DL cows than in HL cows. These findings suggest that the kinetics of folliculogenesis differ among DL and HL cows and the developmental ability of preantral follicles and oocytes is lower in DL cows than in HL cows.

Meiosis in a bottle: new approaches to overcome Mammalian meiocyte study limitations

The study of meiosis is limited because of the intrinsic nature of gametogenesis in mammals. One way to overcome these limitations would be the use of culture systems that would allow meiotic progression in vitro. There have been some attempts to culture mammalian meiocytes in recent years. In this review we will summarize all the efforts to-date in order to culture mammalian sperm and oocyte precursor cells.

Stability of housekeeping genes and expression of locally produced growth factors and hormone receptors in goat preantral follicles

The aim of the present study was to investigate the stability of six housekeeping genes, and the relative expression of growth factors (EGF, GDF-9, BMP-15, VEGF, FGF-2, BMP-6, IGF-1 and KL) and hormone receptors (FSH, LH and GH) in goat preantral follicles. To evaluate to stability of housekeeping genes micro-dissected fresh follicles (150–200 μm) as well as follicles that have been in vitro cultured for 12 days were used. In addition, isolated fresh follicles were used to compare expression of various growth factors and hormone receptors before culture. Both fresh and cultured follicles were subjected to total RNA extraction and synthesis of cDNA. After amplification of cDNA by real-time PCR, the geNorm software program was used to evaluate the stability of glyceraldehyde-2-phosphate dehydrogenase (GAPDH), β-tubulin, β-actin, phosphoglycerokinase (PGK), 18S rRNA, ubiquitin (UBQ) and ribosomal protein 19 (RPL-19). In addition, follicular steady-state levels of mRNA from the various growth factors under study were compared. Results demonstrated that, in goat preantral follicles, UBQ and β-actin were the most suitable reference genes and thus could be used as parameters to normalize data from future in vitro studies. In contrast, 18S RNA appeared the least stable gene among the tested housekeeping genes. Analysis of mRNA for several hypophyseal hormone receptors in fresh preantral follicles showed significantly higher FSH-R mRNA levels than those of LH-R and GH-R, and no difference between GH-R and LH-R mRNA levels. In regard growth factor mRNA expression in goat preantral follicles, EGF mRNA levels appeared significantly lower than those of the other studied growth factors. Increasingly higher relative mRNA levels were observed for GDF-9, BMP-15, BMP-6, FGF-2, VEGF, Kl and IGF-1, successively. In conclusion, UBQ and β-actin are the most stable housekeeping genes in fresh and 12-days cultured caprine preantral follicles. Furthermore, in fresh follicles, high levels of FSH-R mRNA are detected while among eight growth factors, IGF-1 is the most highly expressed and EGF the weakest expressed compound.

Organizational actions of postnatal estradiol in female sheep treated prenatally with testosterone: programming of prepubertal neuroendocrine function and the onset of puberty

Prenatal testosterone (T) exposure defeminizes reproductive neuroendocrine function in female sheep, although the LH surge dysfunctions are initially less severe in gonadally intact females than in females subject to neonatal ovariectomy and estradiol (E) replacement. Because prepubertal ovarian production of E differs quantitatively and qualitatively from chronic E replacement, we tested the hypothesis that postnatal E exacerbates the consequences of prenatal T on the positive, but not the negative, steroid feedback controls of GnRH secretion. Our approach was to characterize prepubertal sensitivity to E negative feedback, the onset and maintenance of progestagenic cycles, and the LH surge response in ovary intact, prenatally untreated (control), and T-treated (T) sheep that were exposed postnatally to only endogenous E, or exposed to excess E by s.c. implant. Sensitivity to E negative feedback was reduced in T females, but excess postnatal E did not further increase LH pulse frequency. Excess E prevented ovarian cycles in several control females, and increased cycle irregularity in T females. However, the LH surge mechanism was functional in all control females (regardless of postnatal E exposure) and in some T females without excess E, but nonfunctional in T females with excess E. These findings suggest that postnatal E does not program increased resistance to E negative feedback, but excess postnatal E does disrupt other mechanisms required for ovarian cyclicity. We conclude that in this precocial species, prenatal steroids are sufficient to program controls of tonic LH secretion, but the LH surge mechanism is susceptible to further programming by postnatal E.

J, Báo S, Nobre Junior H, Maia F, Pessoa C, Moraes M, Silva J, Figueiredo J, Rodrigues A. Característica histológica, ultra-estrutural e produção de nitrito de folículos pré-antrais caprinos cultivados in vitro na ausência ou presença de soro

Avaliou-se o efeito da adição de diferentes tipos e concentrações de soro sobre o desenvolvimento e a sobrevivência de folículos ovarianos pré-antrais (FOPA) caprinos in vitro. Além disso, verificou-se a relação entre as concentrações de nitrito presentes no meio de cultivo e a viabilidade folicular. Cada par ovariano foi dividido em 29 fragmentos, sendo um destinado ao controle. Os fragmentos foram cultivados por um ou sete dias em meio essencial mínimo suplementado (MEM+) ou MEM+ com diferentes concentrações (10 ou 20%) de soro fetal bovino (SFB), soro de cabra em estro (SCE) ou soro de cabra em diestro (SCD). Na análise morfológica após sete dias, apenas o tratamento com 10% de SFB apresentou percentual de FOPA normais similar ao MEM+ (P>0,05). A análise ultra-estrutural dos folículos cultivados por sete dias com MEM+ ou MEM+ com 10% de SFB mostrou danos oocitários, porém células da granulosa normais. A análise do meio de cultivo revelou correlação positiva entre a viabilidade folicular e a produção de nitrito. A suplementação com soro não melhorou a viabilidade de FOPA e a concentração de nitrito no meio de cultivo funcionou como um indicador da viabilidade das células da granulosa de FOPA caprinos cultivados in vitro.

Recovery of large preantral follicles from buffalo ovary: Effect of season and corpus luteum

Preantral follicle can be considered as an alternative source of oocyte for in vitro production of embryos. The objective of the present study was to standardize a procedure for the isolation of large preantral follicles (>150-500 microm) from buffalo ovaries and to determine the effect of season and the presence of corpus luteum on the recovery rate of the large preantral follicles. A combined enzymatic cum mechanical approach was adopted to recover the large preantral follicles. In the first experiment, the ovarian cortical pieces were suspended in trypsin (1000-1500 BAEE units for milligrams of solid) and incubated at various temperatures for different periods, i.e. (1) trypsin (1%), 37 degrees C for 10 min; (2) trypsin (1%), 37 degrees C for 10 min + 4 degrees C for 3 h; (3) trypsin (0.5%), 37 degrees C for 20 min; (4) trypsin (0.25%), 37 degrees C for 20 min. Although there was no significant difference (P>0.05) among the different protocols, the first protocol yielded more follicles (3.2, 2.6, 1.8 and 1.5 per ovary, respectively). Hence, the first protocol was selected and used in the second and third experiments. In the second experiment, the effect of season, i.e. peak breeding season (October-March) versus low breeding season (April-September) was evaluated on the recovery rate of the large preantral follicles. The recovery rate of large preantral follicles from the ovaries during the peak breeding season was significantly (P<0.05) greater (9.92+/-0.85 per ovary) than that of the low breeding season (4.95+/-0.27 per ovary). In the third experiment, effect of the presence of corpus luteum on the recovery rate of large preantral follicles was studied. There was a significantly (P<0.05) higher yield of large preantral follicles from the ovaries with corpus luteum (8.05+/-0.88 per ovary) than for the ovaries without corpus luteum (4.57+/-0.43 per ovary). This study confirms that the large preantral follicles can be isolated from buffalo ovaries using a combination of enzymatic cum mechanical methods and that more large preantral follicles can be recovered during the peak breeding season and from the ovaries having corpus luteum.

Influence of organochlorine pesticides on physiological potency of cultured granulosa cells from bovine preovulatory follicles

In the present study the direct effect of Dichlorodiphenyltrichloroethane (DDT), Methoxychlor (MXC) and Hexachlorocyclohexane (gammaHCH) was investigated on the DNA synthesis (measured by [3H]thymidine incorporation); proliferation (determined by colorimetric MTT[3-[4,5-dimethylthiazol-2yl]-2,5-diphenyl tetrazolium bromide] assay); and steroidogenesis (estradiol 17beta, progesterone determination) of granulosa cells during in vitro culture. The cells were aspirated from preovulatory follicles in PMSG-treated heifers. They were cultivated in phenol red and serum (0.1% FCS) RPMI 1640 medium without or with the 3 pesticides in different concentrations. In summary, the results showed differential inhibition of parameters named above by these pesticides (gammaHCH < MXC < DDT) in comparison with vehicle-treated control. Progesterone synthesis was more inhibited than estradiol 17beta production by 3 chemicals, which resulted from the loss of viability of cells indicated by estimation of cell-shape-factor and viability of cells. Besides the inhibitory effect, there was a stimulatory effect of low concentrations of DDT and MXC on [3H]thymidine incorporation and proliferation.

Bovine oocytes from early antral follicles grow to meiotic competence in vitro: effect of FSH and hypoxanthine

A large number of oocytes are contained in the mammalian ovary. A very small number of these oocytes grow to the final size, mature, and are ovulated. In the ovary there are more early antral follicles than late antral or preovulatory follicles, offering a large pool of oocytes for IVM and IVF if appropriate culture conditions could be devised. In the present study, early antral follicles containing oocytes 90 to 99 microm in diameter were isolated from bovine ovaries. Cumulus-oocyte complexes (COC) with pieces of parietal granulosa (COCG) were then dissected from the follicles. The COCGs were embedded in collagen gels and cultured in Medium 199 with 10% fetal calf serum (FCS) for 8 d. In Experiment 1, the effect of hypoxanthine and FSH on the growth of bovine oocytes was examined. When hypoxanthine (2 and 4 mM) and FSH (10 ng/ml) were added to the culture medium, the number of granulosa cell-enclosed oocytes increased significantly (P < 0.05). All of the oocytes surrounded by granulosa cells showed a normal morphology and were at the germinal vesicle stage, while 75 to 94% of the denuded oocytes were degenerated and had resumed meiosis. The mean diameter of the oocytes showing normal morphology was significantly higher than that measured before culture (P < 0.05). In Experiment 2, the maturational competence of in vitro-grown bovine oocytes was examined. Oocytes which were 90 to 99 microm in diameter before culture did not have meiotic competence. After being in a growth culture of 4 mM hypoxanthine- and 10 ng/ml FSH-supplemented medium for 7 or 11 d, granulosa cell-enclosed oocytes were recovered from the COCGs. No significant difference (P < 0.05) in the diameters of the oocytes was observed between 7 and 11 d of culture (7 d: 107.5 +/- 6.1 microm, n = 30; 11 d: 108.0 +/- 5.3 microm, n = 35). After a subsequent 24 h in a maturation free of hypoxanthine and FSH medium, only 17% of the oocytes cultured for 7 d underwent germinal vesicle breakdown. On the other hand, 89% of the oocytes cultured for 11 d underwent germinal vesicle breakdown, and 11% of the oocytes emitted the first polar body and reached metaphase II. These results demonstrate for the first time that bovine oocytes harvested from early antral follicles can grow, and acquire meiotic competence in vitro.

Bovine preantral follicles and activin: immunohistochemistry for activin and activin receptor and the effect of bovine activin A in vitro

Activin was originally isolated from follicular fluid as a factor stimulating FSH from the pituitary. Recent studies also suggest a local role for activin in the development of preantral and early antral follicles. In the present study, activin and activin receptor immunoreactivity are shown in oocyte and granulosa cells of bovine preantral follicles. In addition, activin immunoreactivity was observed in the theca of secondary follicles. During culture of isolated preantral follicles, activin increased follicular growth and granulosa cell proliferation in a dose-dependent manner. This increase was further stimulated by addition of FSH. In conclusion, activin and its receptor are present on bovine preantral follicles, and additional activin stimulates development of those follicles.

Localization of Oestrogen Receptors Within Various Bovine Ovarian Cell Types at Different Stages of the Oestrous Cycle

In the present study oestrogen receptor alpha(ERalpha) and oestrogen receptor beta (ERbeta) mRNA were localized in various ovarian cell types of 23 cows at different stages of the oestrous cycle. ERalpha was detected by immunohistochemistry and the localization of ERbeta mRNA was examined using in situ hybridization. The immunostaining of ERalpha was low in the ovarian follicles, tunica albuginea and surface epithelium, but high in cells of the deep stroma and superficial stroma, which indicates a functional role of ERalpha in the cells surrounding the follicles. In contrast, ERbeta mRNA scores were low to moderate in primordial and primary follicles, and increased with the development of the follicle. ERbeta mRNA scores were higher in cystic follicles than in obliterative follicles. In the corpora lutea and corpora albicantia the scores for ERbeta mRNA were moderate. Furthermore, in the corpora lutea, ERbeta mRNA levels showed cyclic variations and were low during early dioestrus. The correlation between plasma progesterone levels and the score for ER was low and negative in all ovarian cell types. This study demonstrates the predominant role of ERbeta over ERalpha in bovine ovarian structures. Furthermore, the colocalization of both ERbeta mRNA and ERalpha in most cell types suggests possible interactions between both ER subtypes.

Isolation, follicular density, and culture of preantral follicles of buffalo fetuses of different ages

The aim of the present study was to determine the most desirable ovarian tissue section thickness to isolate preantral follicles (Experiment I), determine follicular density (follicles/mm(2) of cortex) of ovaries of fetal buffalo of different ages (Experiment II), and cultivate preantral follicles of buffalo fetuses (Experiment III). In Experiment I, ovary sections with different thicknesses (25, 50, 75, and 100 microm) had 415.0+/-285.2, 457.5+/-341.9, 585.0+/-309.3, and 685.0+/-278.8 isolated preantral follicles, respectively. In Experiment II, the follicular density of 46 buffalo fetuses with ages between 3 and 8 months was estimated to be between 0 and 7220, with means of 0.0, 2070.7+/-2190.3, 2570.8+/-1796.6, 2298.1+/-2286.5, 1277.5+/-1074.9, and 643.6+/-543.9 throughout the age range studied. The follicular density of 5-month-old fetuses was greatest, coinciding with the largest number of follicles isolated at this age. In Experiment III, preantral follicles isolated from the ovaries of buffalo fetuses aged from 5 to 9 months old were cultivated individually for 7 days in four different media: basic medium (Minimal Essential Medium (MEM), 10% SFB, kanamycin, pyruvate, glutamine, hypoxanthine) with additional ITS and FSH 0.5mg/ml (treatment 1); basic medium with FSH and EGF 100 ng/ml (treatment 2); basic medium with additional ITS, FSH, and EGF (treatment 3); basic medium supplemented with ITS and EGF (treatment 4). Integrity and morphological features, viability, and increase in diameter of follicles cultured in vitro were evaluated individually with an inverted microscope and an ocular micrometer. The results showed that follicle structure and form were maintained during culture. Growth and survival rates of treatments 1, 2, and 3 over 7 day culture were 23.25+/-17.06, 33.75+/-26.19, and 43.75+/-31.73 microm, and 31.3+/-22.7, 22.06+/-8.13, and 28.92+/-21.32%, respectively. However, neither growth nor survival was observed in treatment 4. In conclusion, this study showed that preantral follicles of buffalo fetuses can be cultured in vitro, and that FSH is essential for follicle survival.

Preservation of caprine preantral follicle viability after cryopreservation in sucrose and ethylene glycol

Caprine preantral follicles within ovarian fragments were cryopreserved in the absence or presence of 0.5 M sucrose with or without 1 M dimethyl sulfoxide and/or 1 M ethylene glycol (EG). After being thawed, they were washed in minimum essential medium with or without 0.3 M sucrose. Histological analysis of follicle integrity immediately after cryopreservation showed consistent beneficial effects of including sucrose in the three cryoprotectant solutions analyzed when tissue was thawed without sucrose (53.9+/-14.8-82.4+/-3.2% normal vs 27.6+/-1.6-36.6+/-6.5%, P<0.05). However, in further studies, the addition of sucrose to the thaw solutions proved detrimental or of no benefit. An analysis of the cryopreserved material with calcein-AM and ethidium homodimer (markers for living and dead cells, respectively) gave comparable results to those obtained by histology. Follicles cryopreserved in EG, EG plus sucrose, or sucrose alone were cultured in vitro for 24 h following warming. During this culture period, viability fell most rapidly in material cryopreserved in sucrose alone and was no longer correlated with either the viability or integrity estimates made immediately after warming. By contrast, the viability of follicles cryopreserved in EG with sucrose and then cultured for 24 h was not significantly different from the cultured non-frozen controls. These results indicate that cryopreservation in 1 M EG plus 0.5 M sucrose combined with thawing without sucrose is effective for caprine ovarian tissue.

Effects of estradiol on bovine thecal cell function in vitro: dependence on insulin and gonadotropins

The objective of this study was to evaluate the influence of estradiol (E2) on proliferation and steroid production by thecal cells obtained from large (> or =8 mm) follicles of cattle. Five experiments evaluated the effect of various doses of E2 during a 2-d exposure in serum-free medium on hormone-induced steroidogenesis and cell proliferation. In LH-treated thecal cells of experiment 1, 300 ng/mL of E2 decreased progesterone production by 30% and increased androstenedione production to 5.8-fold of controls. In the absence of LH, both 3 and 300 ng/mL of E2 increased progesterone production. In experiment 2, in the presence of insulin and LH, 3, 30, and 300 ng/mL of E2 decreased progesterone production (by 17 to 36%), whereas 3 ng/mL of E2 decreased and 300 ng/mL of E2 increased androstenedione production. Doses of LH (3 to 30 ng/mL) tested in experiment 3 increased (to as much as 3.7-fold) progesterone production by thecal cells and E2 attenuated this stimulatory effect by 40%. In contrast, E2 amplified the stimulatory effect of LH on androstenedione production in experiment 3. In experiment 4, E2 (300 ng/mL) decreased IGF-I- and insulin-induced thecal cell progesterone production by 70 to 77%, whereas E2 increased basal, IGF-I, and insulin-induced androstenedione production. In experiment 5, in the presence of insulin, 10 to 1000 ng/mL of E2 had no effect on [(125)I]-IGF-I binding to thecal cells, whereas 10 and 100 ng/mL of E2 increased and 1000 ng/mL of E2 decreased progesterone production by thecal cells. Estradiol had no consistent effect on thecal cell numbers among the 5 experiments. These results support the hypothesis that E2 may act as a paracrine factor to directly regulate hormone-induced steroid production by thecal cells without affecting cell numbers or numbers of insulin-like growth factor type I receptors.

Histological and ultrastructural analysis of cryopreserved sheep preantral follicles

The aim of this study was to verify the histological and ultrastructural characteristics of sheep preantral follicles after exposure of ovarian tissue to cryopreservation in glycerol (GLY), ethylene glycol (EG), propanediol (PROH) or dimethyl sulfoxide (DMSO) in order to determine the optimum method to store sheep ovarian tissue for later experimental or clinical use. Each ovarian pair from five mixed-breed ewes was divided into 17 fragments. One (control) fragment was immediately fixed for routine histological and ultrastructural studies and the remaining (test) fragments were randomly distributed in cryotubes, equilibrated at 20 degrees C/20 min in 1.8 mL of minimal essential medium (MEM) containing 1.5 or 3 M GLY, EG, PROH or DMSO and then either fixed for morphological studies to determine their possible toxic effect or frozen/thawed and then fixed to test the effect of cryopreservation on preantral follicles. Histological analysis showed that, compared to control fragments, all cryoprotectants at both concentrations significantly reduced the percentage of normal preantral follicles in ovarian fragments prior to or after cryopreservation. PROH 3.0 M appeared to exert a more toxic effect (P<0.05) than the other cryoprotectants in noncryopreserved tissues. After freezing/thawing, the highest (P<0.05) percentages of lightmicroscopical normal preantral follicles were observed in ovarian fragments cryopreserved in EG (1.5 and 3 M) or DMSO (1.5 M). However, transmission electronic microscopical (TEM) examination showed that only the DMSO-cryopreserved preantral follicles had normal ultrastructure. The data suggest that sheep preantral follicles should be cryopreserved with 1.5 M DMSO for later clinical or experimental application.

In vitro effects of diethylstilbestrol, genistein, 4-tert-butylphenol, and 4-tert-octylphenol on steroidogenic activity of isolated immature rat ovarian follicles

Isolated rat ovarian follicles grow and produce steroid hormones in vitro and so provide a good model for studying the effects of hormonally active compounds on follicular steroidogenesis. We have evaluated the effects of diethylstilbestrol (DES), genistein (GEN) and two alkylphenols, 4-tert-butylphenol (BP) and 4-tert-octylphenol (OP) on the growth, survival, and steroid hormone and cAMP production by isolated 14-day-old rat (Sprague-Dawley) ovarian follicles. During a 5-day culture, FSH was obligatory for follicle growth and increased estradiol and testosterone secretion in a dose-dependent manner. DES (10(-6) M) caused the strongest decline in estradiol and testosterone levels but did not have detectable effects on either cAMP production or aromatase enzyme activity. GEN caused a prominent decrease in cAMP and testosterone levels without significant changes in secreted estradiol. The latter, apparently, was due to a dose-dependent stimulation of aromatase enzyme activity in the presence of genistein. Both BP and OP decreased estradiol and testosterone secretion in a dose-dependent manner while no effect on aromatase activity was observed. OP, unlike BP, decreased forskolin-induced cAMP levels. Xenoestrogens at the used concentrations did not interfere with the growth and survival of the follicles. The results indicate that isolated ovarian follicles representing intact morphological and functional units offer a sensitive model system for elucidating the female-specific reproductive effects of environmental chemicals.

Influences of FSH and EGF on primordial follicles during in vitro culture of caprine ovarian cortical tissue

Factors that control the onset of folliculogenesis are critical to female gamete production, but poorly understood. The aim of the present study was to investigate the effects of FSH and EGF on the activation and growth of goat primordial follicles in vitro. To this end, pieces of goat ovarian cortex were cultured in vitro for 1, 3 or 5 days, at 39 degrees C in an atmosphere containing 5% CO(2), in minimum essential medium supplemented with insulin, transferrin, selenium, pyruvate, glutamine, hypoxanthine, BSA, penicillin, streptomycin and fungizone and with or without FSH (100 ng/ml) and/or EGF (100 ng/ml). At the end of the culture periods, the relative proportions of primordial, intermediate, primary and secondary follicles were calculated and compared with those in non-cultured tissue. In addition, mitotic activity of granulosa cells was studied by immunohistochemistry for proliferating cell nuclear antigen (PCNA). In brief, it was found that goat primordial follicles activate spontaneously during culture in vitro and, while neither FSH nor EGF affected the proportion of primordial follicles that entered the growth phase, both stimulated an increase in oocyte and follicle diameter, especially in intermediate and primary follicles cultured for 5 days. On the other hand, there was no significant effect of culture or either growth factor on the proportion of PCNA-stained growing follicles. Contrary to expectations, neither FSH nor EGF affected follicle viability or integrity during culture, since the percentages of intact follicles did not differ between control, FSH and/or EGF containing medium. In conclusion, this study demonstrated that goat primordial follicles activate spontaneously in vitro, and that both FSH and EGF stimulate an increase in follicle size by promoting oocyte growth.

Survival and growth of goat primordial follicles after in vitro culture of ovarian cortical slices in media containing coconut water

The development of culture systems to support the initiation of growth of primordial follicles is important to the study of the factors that control the earliest stages of folliculogenesis. We investigated the effectiveness of five culture media, two supplements and three culture periods on the survival and growth of goat primordial follicles after culturing ovarian cortex. The media were based on minimal essential minimum (MEM) and coconut water solution (CWS) added in the proportion of 0, 25, 50, 75 or 100%. The two supplements were none versus supplemented with insulin-transferrin-selenium, pyruvate, glutamine, hypoxanthine, and BSA. Pieces of goat ovarian cortex were cultured in the media for 1, 3 or 5 days and representative samples were evaluated at day 0 as non-cultured controls. The replicates were the two ovaries of five mixed breed goats. The number of primordial, intermediate, primary and secondary follicles at each period of culture and the number of degenerated follicles were evaluated. Mitotic activity of granulosa cells was studied by immunolocalization of proliferating cell nuclear antigen (PCNA). The number of follicles in each stage and degenerated follicles were statistically analyzed by ANOVA using a factorial design and the significance of differences assessed using Tukey test. Chi-square test was used to compare the percentage of follicles with PCNA positive granulosa cells. As the culture period progressed, the number of primordial follicles fell and there was a significant increase in the number of primary follicles. The fall in the number of primordial follicles was particularly marked after 1 day culture. No effect of media on the number of primordial and primary follicles was observed after culture, but MEM as well as supplements increased the number of intermediate follicles. Follicular degeneration was kept at the same level after culture in the media tested, except for pure CWS that increased the number of degenerated follicles. In contrast, addition of supplements to culture media reduced follicular degeneration. In non-cultured tissue, PCNA was expressed in granulosa cells of 31.6% of the growing follicles. This percentage had not significantly changed after 5 days culture in the various media, indicating the maintenance of proliferation activity of granulosa cells during culture. In conclusion, it is shown that goat primordial follicles may be successfully activated after in vitro culture in all media tested. However, when pure CWS is used the follicular degeneration is enhanced, but the addition of supplements to culture media decrease follicular degeneration.

Survival of frozen-thawed human ovarian fetal follicles in long-term organ culture

Ovarian follicles obtained from second and third-trimester human fetuses survived 4 weeks in organ culture and secreted 17-beta estradiol (E(2)).

The early stages of follicular development: activation of primordial follicles and growth of preantral follicles

Although enormous progress has been made in understanding the events and regulation of the later stages of ovarian follicular development, the early stages of development, to a large extent and particularly in large mammals, remain a mystery. Mechanisms that regulate the initiation of follicular growth (follicle activation) and the ensuing growth and differentiation of preantral follicles are of considerable interest, since their elucidation is a prerequisite to use of the primordial pool to enhance reproductive efficiency in domestic animals, humans, and endangered species. This review is an attempt to summarize the approaches that have been taken to further this goal and the results thus far of these efforts. Preantral follicular development can be divided into three stages: activation of primordial follicles, the primary to secondary follicle transition, and the development of secondary follicles to the periantral stage. The activation of primordial follicles in vitro has been achieved thus far in rodents, cattle, and primates, where it occurs spontaneously without the addition of growth factors or hormones. The ovaries of rodents are small enough to be cultured intact and, in that experimental situation, some follicles activate, while many remain in the resting pool, and the addition of specific factors can increase or decrease the number of follicles that leave the resting pool in vitro. In contrast, follicular activation in cattle and primates has been studied by culturing small pieces of the ovarian cortex, rich in primordial follicles, and the great majority of the primordial follicles activate in that situation, suggesting the importance of inhibitory factors to the normal, gradual exit of follicles from the resting pool. In cultured rodent ovaries, follicles appear to pass easily and spontaneously from the primary to the secondary stage, whereas few of the activated follicles in cultured cortical pieces from cattle or primates progress from the primary to the secondary stage. Understanding the requirements for the primary to secondary transition is critical for growing follicles activated in vitro to the late preantral and antral stages. In contrast, the requirements for the continued growth of larger preantral follicles, which can be isolated for in vitro studies, have been extensively explored in rodents and to a lesser extent in domestic species. A number of hormones and factors have been implicated and will be discussed. Taken together, the results highlight the need for a better understanding of the earliest stages of follicular development in domestic ruminants, particularly follicle activation and the primary to secondary follicle transition.

From the germinal cells to the newborn animal: the transmission of genes and life through the generations

The technology of reproduction progressed considerably during the last decade, leading to a certain availability of in vitro methods for fertilisation, oocyte maturation and embryo culture. The most spectacular manipulations are cloning and transgenesis. This review focuses on the early appearance of germinal cell precursors and the long-standing fate of gametes in mammals. The evident complexity and long-term programming of events in gametes and early embryos explain part of the difficulties encountered during the development of in vitro and in vivo methods such as multiple ovulation and embryo transfer (MOET), oestrus synchronisation, ovulation induction, superovulation, in vitro maturation and fertilisation, cryopreservation, transgenesis, nuclear transfer and cloning) and the occurrence of unexpected alterations of development, e.g. embryonic or fetal mortality, large-weight newborn syndrome and other dysregulations in imprinting or DNA transmission.

Interactions between the Oocyte and Surrounding Somatic Cells in Follicular Development: Lessons from In Vitro Culture

Mammalian oogenesis occurs concomitantly with folliculogenesis in a coordinated manner in the ovaries. In vitro growth (IVG) culture systems of the oocytes have been developed as a new technology for utilizing incompetent oocytes in the ovary as a source of mature oocytes as well as for studying oogenesis, folliculogenesis, and oocyte-somatic cell interactions. The results of IVG experiments have suggested that direct association of oocytes and surrounding granulosa cells supports oocyte viability and growth through the gap junctions, which are efficient conduits for low molecular weight substances. It has been revealed that granulosa cells metabolize some molecules which are in turn transported into the oocytes. IVG systems have also provided evidence that FSH promotes the development of follicles at secondary or later stages by its stimulation of proliferation and differentiation of granulosa cells, and perhaps by its anti-apoptotic effects. In addition, interactions between granulosa cell-derived KIT ligands and oocyte KIT receptors have been suggested as initiating oocyte growth and follicular development. Furthermore, recent findings suggest there are growth factors derived from oocytes such as GDF-9 and BMP-15. With such factors, oocytes participate in follicular development by regulating the differentiation of surrounding somatic cells. These bidirectional communications between oocytes and somatic cells are important for oocyte growth and follicular development. IVG systems should provide further information regarding oogenesis and folliculogenesis in the ovary.

Growth, Antrum Formation, and Estradiol Production of Bovine Preantral Follicles Cultured in a Serum-Free Medium1

The objective of this study was to identify factors that would allow the establishment of a serum-free culture system that could support follicular and oocyte growth, antrum formation, and estradiol-17beta (E(2)) production in preantral follicles of bovine ovaries. Large preantral follicles (145-170 micro m in diameter) were microsurgically dissected from ovaries, embedded in 0.15% type I collagen gels, and maintained in a serum-free medium for up to 13 days at 38.5 degrees C in 5% CO(2) in air. This culture environment allowed most preantral follicles to maintain a three-dimensional structure with the presence of a thecal layer and basement membrane surrounding the granulosa cells throughout the entire culture period. The effects of insulin, insulin-like growth factor (IGF)-I, IGF-II, FSH, and LH on preantral follicle growth were investigated in serum-free medium. Follicular diameters were significantly larger in the presence of insulin, IGF-I, IGF-II, or FSH after 13 days in culture. Oocyte diameters were also significantly larger in the presence of all hormones tested. The single addition of insulin, IGF-I, or FSH induced antrum formation between Days 7 and 13 of culture. Insulin progressively induced E(2) secretion by follicles after antrum formation, but IGF-I and FSH had no apparent effect. FSH and LH caused an increase in oocyte diameter in the presence of insulin. The addition of three hormones (insulin, FSH, and LH) initiated antrum formation and E(2) production earlier than insulin-containing medium alone. Furthermore, maximal E(2) secretion was maintained steadily between 7 and 13 days in this culture condition. From these results, we have demonstrated that insulin, FSH, and LH play substantial roles in the growth and development of bovine large preantral follicles in a serum-free medium.