Importance of preovulatory estradiol on uterine receptivity and luteal function

Animals that exhibited estrus had greater pregnancy success compared to animals that did not exhibit estrus before fixed-time AI (FTAI). Estradiol is synthesized in bovine ovarian follicles under gonadotropin regulation and can directly and indirectly regulate the uterine receptivity and luteal function. Estradiol concentrations at FTAI impacted oviductal gene expression and has been reported to play an important role in establishing the timing of uterine receptivity. These changes have been reported to impact uterine pH and sperm transport to the site of fertilization. After fertilization, preovulatory estradiol has been reported to improve embryo survival likely by mediating changes in uterine blood flow, endometrial thickness and changes in histotroph. Cows with greater estradiol concentrations at the time of GnRH-induced ovulation also had a larger dominant follicle size and greater circulating progesterone concentrations on day 7. Therefore, it is impossible to accurately determine the individual benefit of greater estradiol concentrations prior to ovulation and greater progesterone concentrations following ovulation to pregnancy establishment, as these two measurements are confounded. Research has indicated an importance in the occurrence and timing of increasing preovulatory concentrations of estradiol, but increasing estradiol concentrations by supplementation may not be sufficient to increase fertility. Increased production of estradiol by the preovulatory follicle may be required to enhance fertility through the regulation of sperm transport, fertilization, oviductal secretions, the uterine environment, and embryo survival.(AU)

Supplemented powdered coconut water (ACP-406®) promotes growth of goat secondary follicles and oocyte meiotic resumption

The objective of this study was to test the efficiency of powdered coconut water (ACP-406®) base-medium without or with the addition of supplements on in vitro culture of isolated goat secondary follicles. Follicles were cultured for 18 days in α-MEM or in ACP-406®, both without supplements (referred to as α-MEM and ACP, respectively), or both supplemented with BSA, insulin, transferrin, selenium, glutamine, hypoxanthine, and ascorbic acid (referred to as α-MEM+ and ACP+). Follicular morphology, antrum formation, follicular and oocyte diameter, levels of glutathione (GSH), and chromatin configuration after in vitro maturation were evaluated. At the end of culture, ACP-406® base-medium (without or with supplements) showed a higher (P < 0.05) percentage of normal follicles than α-MEM (without or with supplements). Antrum formation was similar among α-MEM+, ACP and ACP+, and significantly higher than α-MEM without supplements. The follicular diameter was greater in ACP+ than α-MEM, and similar to other treatments. Moreover, fully and daily grown rates were higher (P < 0.05) in ACP-406® base-medium (without or with supplements) than α-MEM (without or with supplements). Levels of GSH were similar between ACP+ and α-MEM+ treatments. Both ACP+ and α-MEM+ allowed meiotic resumption without a significant difference between the two groups. In conclusion, supplemented ACP-406® base-medium maintained follicular survival and promoted the development as well as meiotic resumption of isolated goat secondary follicles cultured in vitro for 18 days.(AU)

Supplemented powdered coconut water (ACP-406®) promotes growth of goat secondary follicles and oocyte meiotic resumption

The objective of this study was to test the efficiency of powdered coconut water (ACP-406®) base-medium without or with the addition of supplements on in vitro culture of isolated goat secondary follicles. Follicles were cultured for 18 days in α-MEM or in ACP-406®, both without supplements (referred to as α-MEM and ACP, respectively), or both supplemented with BSA, insulin, transferrin, selenium, glutamine, hypoxanthine, and ascorbic acid (referred to as α-MEM+ and ACP+). Follicular morphology, antrum formation, follicular and oocyte diameter, levels of glutathione (GSH), and chromatin configuration after in vitro maturation were evaluated. At the end of culture, ACP-406® base-medium (without or with supplements) showed a higher (P < 0.05) percentage of normal follicles than α-MEM (without or with supplements). Antrum formation was similar among α-MEM+, ACP and ACP+, and significantly higher than α-MEM without supplements. The follicular diameter was greater in ACP+ than α-MEM, and similar to other treatments. Moreover, fully and daily grown rates were higher (P < 0.05) in ACP-406® base-medium (without or with supplements) than α-MEM (without or with supplements). Levels of GSH were similar between ACP+ and α-MEM+ treatments. Both ACP+ and α-MEM+ allowed meiotic resumption without a significant difference between the two groups. In conclusion, supplemented ACP-406® base-medium maintained follicular survival and promoted the development as well as meiotic resumption of isolated goat secondary follicles cultured in vitro for 18 days.

Oocyte maturation in the toad Rhinella arenarum (Amphibia, Anura): Evidence of cAMP involvement in steroid production and action.

In this work, we describe the participation of the adenylate cyclase/3'-5'-cyclic adenonsine monophosphate (cAMP) pathway in the seasonal follicular secretion of progesterone (P4 ) and testosterone (T), and its relationship with the maturation of Rhinella arenarum oocytes. Under gonadotropin stimulation, P4 secretion was the dominant steroid produced during the reproductive period, resulting in 100% germinal vesicle breakdown (GVBD) in oocytes in vitro; in contrast, T and estradiol (E2 ) secretion increased (∼16 nM/20 follicles and ∼80 pM/20 follicles, respectively) during the non-reproductive period, but only yielded 50% GVBD. Treatment of the follicles with dibutyryl-cAMP or forskolin induced a significant increase in T secretion during both periods, but P4 secretion did not significantly change and GVBD did not occur. These results suggest that high cAMP levels in the oocyte maintain meiotic arrest and prevent the induction effect of follicular steroids. An increase in cAMP levels in denuded oocytes, however, negatively regulated T-induced maturation since treatment with increasing db-cAMP or forskolin inhibited their maturation. Therefore, we hypothesize that an elevation in T during the non-reproductive period favors its aromatization to E2 , leading to follicle growth. During the reproductive period, P4 production might promote oocyte maturation when environmental conditions are favorable for reproduction. Together, the results indicate that steroidogenesis is seasonal and depends on gonadotropic activity in R. arenarum.

In search of the transcriptional blueprints of a competent oocyte

The oocyte undergoes a remarkably long andelaborated journey within the follicle before becomingfully equipped to sustain embryonic development. Itsability to support early embryonic development relieslargely on the maternal transcripts accumulated duringits growth and maturation. However, it is still not clearwhat transcriptome blueprint composes a competentoocyte. A number of extensive studies provided adetailed characterization of the mRNA molecules thatare gradually accumulated in the oocyte cytoplasm. Thedetail of our knowledge has gradually increased throughthe years also thanks to the development andimprovement of the analytical techniques. From realtimePCR analysis of single transcripts, to the wholetranscriptome approach of gene arrays and newgenereation sequencing, scientists accumulated anexponentially growing amount of new information.More recently, the discovery of non-coding RNAsrevealed a new layer of complexity in the mechanismsthat modulate gene expression at the mRNA level, infolliculogenesis and oogenesis. In particular, data areemerging on the potential role of microRNAs incontrolling ovarian function, oocyte maturation and theoocyte-somatic cell cross talk. This review will try tosummarize the vast amount of data currently available onthe mRNAs and microRNAs associated with the ovarianfunction and to find their biological significance.(AU)

In search of the transcriptional blueprints of a competent oocyte

The oocyte undergoes a remarkably long andelaborated journey within the follicle before becomingfully equipped to sustain embryonic development. Itsability to support early embryonic development relieslargely on the maternal transcripts accumulated duringits growth and maturation. However, it is still not clearwhat transcriptome blueprint composes a competentoocyte. A number of extensive studies provided adetailed characterization of the mRNA molecules thatare gradually accumulated in the oocyte cytoplasm. Thedetail of our knowledge has gradually increased throughthe years also thanks to the development andimprovement of the analytical techniques. From realtimePCR analysis of single transcripts, to the wholetranscriptome approach of gene arrays and newgenereation sequencing, scientists accumulated anexponentially growing amount of new information.More recently, the discovery of non-coding RNAsrevealed a new layer of complexity in the mechanismsthat modulate gene expression at the mRNA level, infolliculogenesis and oogenesis. In particular, data areemerging on the potential role of microRNAs incontrolling ovarian function, oocyte maturation and theoocyte-somatic cell cross talk. This review will try tosummarize the vast amount of data currently available onthe mRNAs and microRNAs associated with the ovarianfunction and to find their biological significance.

Avaliação da temperatura de transporte de folículos ovarianos bovinos coletados nos períodos chuvoso e seco da região norte do Tocantins / Follicles transport temperature evaluation ovarian collected cattle in the rainy and dry seasons of the northern Tocantins

The objective of this study was to evaluate the effect of temperature and transport time on the CumulusComplex - oophorus (COC). We evaluated 181 cattle COCs obtained from 15 pairs of ovaries, and 743 ovarianfollicles obtained from 30 pairs of ovaries subjected to histological processing. They evaluated the transport at4°C and 37°C in the period of 6:18 hours. After aspiration, the COCs obtained were stained with Trypan Blue toverify the integrity of the cell membrane and / or oocyte, and made the counting of follicles. The ovariestransported at lower temperatures and in shorter time showed better viability, suggesting maintaining theintegrity of the plasma membrane of cells COCs. As the temperature rises, the viability of COCs decreases as thenumber of follicles, suggesting damage to the membranes of such cells. Thus, it was concluded that COCs andovarian follicles undergo with temperature and transport time.(AU)

Avaliação da temperatura de transporte de folículos ovarianos bovinos coletados nos períodos chuvoso e seco da região norte do Tocantins / Follicles transport temperature evaluation ovarian collected cattle in the rainy and dry seasons of the northern Tocantins

The objective of this study was to evaluate the effect of temperature and transport time on the CumulusComplex - oophorus (COC). We evaluated 181 cattle COCs obtained from 15 pairs of ovaries, and 743 ovarianfollicles obtained from 30 pairs of ovaries subjected to histological processing. They evaluated the transport at4°C and 37°C in the period of 6:18 hours. After aspiration, the COCs obtained were stained with Trypan Blue toverify the integrity of the cell membrane and / or oocyte, and made the counting of follicles. The ovariestransported at lower temperatures and in shorter time showed better viability, suggesting maintaining theintegrity of the plasma membrane of cells COCs. As the temperature rises, the viability of COCs decreases as thenumber of follicles, suggesting damage to the membranes of such cells. Thus, it was concluded that COCs andovarian follicles undergo with temperature and transport time.

Protein and messenger RNA expression of interleukin 1 system members in bovine ovarian follicles and effects of interleukin 1ß on primordial follicle activation and survival in vitro.

This study aimed to investigate the expression of interleukin 1 (IL-1) system members (proteins and messenger RNA of ligands and receptors) and its distribution in ovarian follicles of cyclic cows and to evaluate the effects of IL-1ß on the survival and activation of primordial follicles in vitro. The ovaries were processed for localization of IL-1 system in preantral and antral follicles by immunohistochemical, real-time polymerase chain reaction, and Western blot analysis. For in vitro studies, ovarian fragments were cultured in α-MEM(+) supplemented with IL-1ß (0, 1, 10, 50, or 100 ng/mL), and after 6 d, the cultured tissues were processed for histologic analysis. Immunohistochemical results showed that the IL-1 system proteins IL-1ß, IL-1RA, IL-1RI, and IL-1RII were detected in the cytoplasm of oocytes and granulosa cells from all follicular categories and theca cells of antral follicles. Variable levels of messenger RNA for the IL-1 system members were observed at different stages of development. After 6 d of culture, the presence of IL-1ß (10 or 50 ng/mL) was effective in maintaining the percentage of normal follicles and in promoting primordial follicle activation. In conclusion, IL-1 system members are differentially expressed in ovarian follicles according to their stage of development. Moreover, IL-1ß promotes the development of primordial follicles. These results indicate an important role of the IL-1 system in the regulation of bovine folliculogenesis.

Involvement of PAPP-A and IGFR1 in Cystic Ovarian Disease in Cattle.

Cystic ovarian disease (COD) is one of the main causes of infertility in dairy cattle. It has been shown that intra-ovarian factors, such as members of the insulin-like growth factor (IGF) system, may contribute to follicular persistence. The bioavailability of IGF to initiate its response by binding to specific receptors (IGFRs) depends on interactions with related compounds, such as pregnancy-associated plasma protein A (PAPP-A). The aim of this study was to determine IGFR1 and PAPP-A expression both in follicles at different stages of development and in cysts, to evaluate the roles in the etiopathogenesis of COD in cattle. The mRNA expression of PAPP-A was higher in granulosa cells of large tertiary follicles than in cysts, whereas the protein PAPP-A present in the follicular fluid from these follicles showed no differences. Although no PAPP-A mRNA expression was detected in smaller tertiary follicles, in their follicular fluid, this protease was detected in lesser concentration than in cysts. The mRNA expression of IGFR1 was lower in granulosa cells from cystic follicles than in those from tertiary ones. However, the protein expression of this receptor presented the highest levels in cystic structures, probably to increase the possibility of IGF response. The data obtained would indicate that animals with COD have an altered regulation of the IGF system in the ovary, which could be involved in the pathogenesis of this disease in cattle.

Immunolocalization of growth, inhibitory, and proliferative factors involved in initial ovarian folliculogenesis from adult common squirrel monkey (Saimiri collinsi).

We performed an immunohistochemical (IHC) study to determine the follicular expression of growth differentiation factor 9 (GDF-9), anti-Müllerian hormone (AMH), Kit Ligand (KL), and c-Kit in squirrel monkey ovary. Ovarian tissue fragments from 4 squirrel monkeys were collected by laparotomy and processed for classical histology and IHC. Additionally, follicle development was assessed by Ki67 immunostaining to evaluate proliferative status of granulosa cells. A total of 4025 follicles were examined (1475 for classical histology and 2550 for immunohistochemistry). More than 80% of the evaluated follicles were morphologically normal. The GDF-9 protein was detectable in oocyte cytoplasm from primordial (100%), primary (99.1%), and secondary (100%) follicles. The AMH was not expressed in primordial follicles but just in few primary follicles (13.8%). On the other hand, it was highly expressed in granulosa cells from secondary follicles (67.9%). c-Kit, KL receptor, was found in the oolemma of primordial (100%), primary (100%), and secondary (100%) follicles. The KL expression was observed in oocytes and granulosa cells from primordial (94.9%), primary (91.6%) and secondary follicles (100%). Ki67 immunostaining was observed in granulosa cells from primary (5.7%) and secondary (54.8%) follicles but not in primordial follicles. In conclusion, we described the localization of GDF-9, KL, c-Kit, and Ki67 proteins and confirmed the presence of AMH protein in preantral follicles from squirrel monkey. Our results offer contribution for understanding of folliculogenesis in neotropical nonhuman primates. Moreover, these markers can be used to assess follicular viability and functionality after cryopreservation, transplantation, or in vitro culture of ovarian tissue.

The effects of epidermal growth factor (EGF) on the in vitro development of isolated goat secondary follicles and the relative mRNA expression of EGF, EGF-R, FSH-R and P450 aromatase in cultured follicles.

The effects of varying concentrations of EGF were evaluated in terms of in vitro follicular development and the mRNA expression levels of EGF, EGF-R, FSH-R and P450 aromatase. After 6 days, the addition of 50 ng/mL of EGF to the culture medium increased the antrum formation rates in comparison to cultured control and after 18 days of culture produced oocytes with higher rates of meiosis resumption when compared to the other treatments (P<0.05). The daily follicular growth rates in presence of EGF (50 or 100) were increased in comparison to the cultured control (P<0.05). Treatment with EGF 50 stimulated the expression of EGF mRNA but reduced EGF-R mRNA expression and estradiol secretion as compared to the cultured control (P<0.05). After 18 days of culture, the mRNA levels for FSH-R and P450 aromatase were greater than those of the non-cultured controls (P<0.05). In conclusion, the effects of EGF treatment on the mRNA levels for EGF, EGF-R, FSH-R, and P450 aromatase varied according to the stage of follicle development.

Avaliação de diferentes pressões negativas na aspiração folicular transvaginal guiada por ultrassom sobre a recuperação oocitária em éguas

O presente experimento visou investigar se diferentes pressões negativas da bomba de vácuo (150, 280 e 400mmHg) podem influenciar a taxa de recuperação oocitária por folículo preovulatório aspirado. Para tanto, foram submetidos a ovum pick up 21 ciclos estrais de éguas ciclando regularmente, distribuídos em três grupos (G150= 150 mmHg; G280= 280 mmHg; G400= 400 mmHg), na seguinte ordem: G150= 150 mmHg (n=6); G280= 280 mmHg (n=7); G400= 400 mmHg (n=6), definida por meio de sorteio. Durante o estro, a atividade ovariana das éguas foi monitorada diariamente através da técnica ultrassonográfica transretal até que o maior folículos atingisse pelo menos 35mm de diâmetro e edema endometrial grau 2,5 durante a avaliação ultrassonográfica, quando então administrou-se 1000UI de hCG, por via endovenosa. Aproximadamente 24 horas após a administração de hCG as éguas foram submetidas a exame ultrassonográfico a cada seis horas para avaliação folicular. Caso houvesse indicação iminente de ovulação ou formação de folículo hemorrágico¬, o mesmo seria imediatamente aspirado. As aspirações ocorreram em 32,45±1,92h após a aplicação do hCG fazendo uso de ultrassom equipado com um transdutor convexo de 5,0mHz com guia de polietileno contendo uma agulha de duplo lúmen de 12G. O fluido folicular coletado de cada folículo foi congelado e o conteúdo aspirado transferido para uma Placa de Petri e examinado minuciosamente ao estereomicroscópio para localização dos oócitos. Para avaliar estatisticamente o efeito das diferentes pressões sobre a recuperação oocitária, foi utilizado o teste Qui-Quadrado (a 5% de significância) e Fisher Exato, quando recomendado. A taxa de recuperação foi de 31,57% (6/19), sendo 16,66 % (1/6) no G150, 42,85 % (3/7) no G280 e 33,33 % (2/6) no G400. Não houve diferença entre os grupos (p>0,05). Através dos resultados obtidos no presente estudo é possível concluir que a pressão negativa da bomba de vácuo utilizada não é o determinante para elevar a recuperação oocitária, possivelmente havendo outros fatores atuando de modo mais importante.

Expression levels of mRNA-encoding PDGF receptors in goat ovaries and the influence of PDGF on the in vitro development of caprine pre-antral follicles.

The aims of this study were to investigate the expression levels of mRNA for platelet-derived growth factor (PDGF) receptors (PDGFR-α and -ß) in caprine follicles at different developmental stages and to evaluate the influence of PDGF on the in vitro development of pre-antral follicles. For this, goat primordial, primary and secondary follicles, as well as small (1-3 mm) and large (3-6 mm) antral follicles, were obtained, and PDGFR-α and -ß mRNA levels were quantified by real-time PCR. Furthermore, pre-antral follicles (≥ 200 µm) were isolated from goat ovaries and cultured for 18 days in α- minimum essential medium supplemented with PDGF at 50 or 100 ng/ml, containing or not FSH. Real-time PCR showed highest PDGFR-α mRNA levels in secondary follicles, while PDGFR-ß mRNA levels were highest in primary follicles onwards. Both receptors showed higher mRNA levels in granulosa/theca cells from small and large antral follicles than in their corresponding cumulus-oocyte complexes. In culture, the percentage of antrum formation was significantly higher in 100 ng/ml PDGF compared with the same PDGF concentration associated with FSH. After 18 days, PDGF in both concentrations associated with FSH promoted follicular growth significantly higher than the control. Moreover, the addition of FSH to 50 ng/ml PDGF positively influenced the follicular growth when compared with the same PDGF concentration in the absence of FSH. In conclusion, PDGF is important for early goat folliculogenesis, because the presence of PDGFR-α and -ß mRNA was detected in all follicular categories, and PDGF associated with FSH stimulated the growth of goat pre-antral follicles isolated and cultured in vitro.

Gene expression and immunolocalization of fibroblast growth factor 2 in the ovary and its effect on the in vitro culture of caprine preantral ovarian follicles.

This study quantified Fibroblast growth factor 2 (FGF-2) mRNA and localized FGF-2 protein in different categories of follicles isolated from goat ovaries. In addition, we verified the effects of this factor on the in vitro culture of preantral follicles isolated from goats. For mRNA quantification, we performed real-time PCR using primordial, primary and secondary follicles, as well as cumulus-oocyte complexes (COCs) and mural granulosa and theca cells of small and large antral follicles. For FGF-2 protein localization, the ovaries were subjected to conventional immunohistochemical procedures. Preantral follicles were isolated and cultured in vitro for 12 days in either control (basic) or supplemented with FGF-2 medium. The expression of FGF-2 mRNA was detected in all categories of follicles and there was no difference in preantral follicles and COCs or granulosa/theca cells from small and large antral follicles. However, in large antral follicles, COCs showed expression levels significantly lower than in granulosa/theca cells (p < 0.05). We observed moderate expression of FGF-2 protein in preantral follicles but not in granulosa cells of primordial follicles and theca cells of secondary follicles. In both small and large antral follicles, strong, moderate and weak staining was observed in oocytes, granulosa and theca cells, respectively. The addition of FGF-2 caused a significant increase in the daily follicular growth rate compared to the control group. We conclude that FGF-2 mRNA is expressed throughout follicular development and that its protein can be found in different patterns in preantral and antral follicles. Furthermore, FGF-2 increases the follicular growth rate in vitro.

Cytoskeletal organization of bee ovarian follicles during oogenesis.

The germ cells in the germarium of the bee meroistic polytrophic ovarian cysts remain interconnected by cytoplasmic bridges as a result of incomplete cell division. These intercellular bridges form a distribution pathway for the substances that initially determine which of the cystocytes will become oocyte and later conduct the products synthesized by the nurse cells to the oocyte. In the present work, the presence and distribution of cytoskeleton components, actin and tubulin were studied in ovaries of queens of Apis mellifera and Scaptotrigona postica, two eusocial species, using antibody against α- and ß-tubulin and FITC-phalloidin, aiming to shed light on the role of these cytoskeleton elements in oogenesis. The immunofluorescent preparations were analyzed by laser scanning confocal microscopy. F-actin was detected in the intercellular bridges of both species. The tubulin distribution in cell cytoplasm of A. mellifera and S. postica also displayed similar pattern. The role of these elements in the oogenetic events responsible for both cell support and motility is discussed.

Papel dos antioxidantes no cultivo in vitro de células ovarianas / The role of antioxidants in the in vitro culture of ovarian cells

Radicais livres são moléculas que contêm elétrons desemparelhados na camada de valência atuando na defesa do organismo contra agentes estranhos, podendo ser importantes marcadores da remodelação dos tecidos. Entretanto, um desequilíbrio entre sua produção e neutralização pode levar a danos celulares, denominados estresse oxidativo. Os agentes neutralizantes dessas moléculas são conhecidos como antioxidantes e podem ser de natureza enzimática ou não. Tendo em vista que o metabolismo oxidativo é essencial para a produção de energia em gametas e embriões, a produção de radicais livres é inevitável. Alguns agentes antioxidantes têm sido adicionados aos meios de cultivo de células ovarianas a fim de reduzir o estresse oxidativo. Sendo assim, a presente revisão objetiva descrever os principais antioxidantes e suas funções em compartimentos celulares com ênfase nas células ovarianas.

Free radical is any molecule containing unpaired electrons in the valence shell, which protects the body against foreign agents and can act as important markers in tissue remodelation. Nevertheless, an imbalance between production and neutralization of these factors can damage cells in a process named oxidative stress. Neutralizing agents for these molecules are known as antioxidants, which can be enzymatic in nature or not. Since oxidative metabolism is essential for energy production in gametes and embryos, free radicals generation is unavoidable. Some antioxidant agents have been employed in culture media for ovarian cells. In this context, the aim of present review is to describe the main antioxidants and their functions within cellular compartments, with focus on ovarian cells.

Influência dos hormônios esteroides na foliculogênese / Influence of steroid hormones on folliculogenesis

Os hormônios esteroides estão diretamente relacionados com o processo de foliculogênese, o qual é bastante complexo e influenciado também por vários fatores de crescimento e por hormônios. Diversos estudos demonstraram a importância dos esteroides no desenvolvimento folicular, na maturação oocitária, bem como na formação do corpo lúteo. Desta forma, o objetivo da presente revisão foi sintetizar o processo de formação e o mecanismo de ação dos hormônios esteroides na foliculogênese, com ênfase no estradiol, na progesterona e nos andrógenos.

Steroid hormones are directly related to the folliculogenesis process, which is very complex and also influenced by several growth factors and hormones. Several studies have demonstrated the importance of steroids in follicular development in mature oocytes as well as corpus luteum formation. The objective of this review is to address the process of synthesis and mechanism of action of steroid hormones in folliculogenesis, with emphasis on estradiol, progesterone and androgens.

Influência dos hormônios esteroides na foliculogênese / Influence of steroid hormones on folliculogenesis

Os hormônios esteroides estão diretamente relacionados com o processo de foliculogênese, o qual é bastante complexo e influenciado também por vários fatores de crescimento e por hormônios. Diversos estudos demonstraram a importância dos esteroides no desenvolvimento folicular, na maturação oocitária, bem como na formação do corpo lúteo. Desta forma, o objetivo da presente revisão foi sintetizar o processo de formação e o mecanismo de ação dos hormônios esteroides na foliculogênese, com ênfase no estradiol, na progesterona e nos andrógenos.(AU)

Steroid hormones are directly related to the folliculogenesis process, which is very complex and also influenced by several growth factors and hormones. Several studies have demonstrated the importance of steroids in follicular development in mature oocytes as well as corpus luteum formation. The objective of this review is to address the process of synthesis and mechanism of action of steroid hormones in folliculogenesis, with emphasis on estradiol, progesterone and androgens.(AU)

Papel dos antioxidantes no cultivo in vitro de células ovarianas / The role of antioxidants in the in vitro culture of ovarian cells

Radicais livres são moléculas que contêm elétrons desemparelhados na camada de valência atuando na defesa do organismo contra agentes estranhos, podendo ser importantes marcadores da remodelação dos tecidos. Entretanto, um desequilíbrio entre sua produção e neutralização pode levar a danos celulares, denominados estresse oxidativo. Os agentes neutralizantes dessas moléculas são conhecidos como antioxidantes e podem ser de natureza enzimática ou não. Tendo em vista que o metabolismo oxidativo é essencial para a produção de energia em gametas e embriões, a produção de radicais livres é inevitável. Alguns agentes antioxidantes têm sido adicionados aos meios de cultivo de células ovarianas a fim de reduzir o estresse oxidativo. Sendo assim, a presente revisão objetiva descrever os principais antioxidantes e suas funções em compartimentos celulares com ênfase nas células ovarianas.(AU)

Free radical is any molecule containing unpaired electrons in the valence shell, which protects the body against foreign agents and can act as important markers in tissue remodelation. Nevertheless, an imbalance between production and neutralization of these factors can damage cells in a process named oxidative stress. Neutralizing agents for these molecules are known as antioxidants, which can be enzymatic in nature or not. Since oxidative metabolism is essential for energy production in gametes and embryos, free radicals generation is unavoidable. Some antioxidant agents have been employed in culture media for ovarian cells. In this context, the aim of present review is to describe the main antioxidants and their functions within cellular compartments, with focus on ovarian cells.(AU)