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Oxidative stress during in vitro of ovarian tissues has adverse effects on follicle survival. α-pinene is a monoterpenoid molecule with antioxidant activity that has great potential to maintain cell survival in vitro. This study investigated the effect of α-pinene (1.25, 2.5, 5.0, 10.0, or 20.0 µg/mL) on primordial follicle growth and morphology, as well as on stromal cells and collagen fibers in bovine ovarian slices cultured for six days. The effect of α-pinene on transcripts of catalase (CAT), superoxide dismutase (SOD), peroxiredoxin 6 (PRDX6), glutathione peroxidase (GPX1), and nuclear factor erythroid 2-related factor 2 (NRF2) was investigated by real-time PCR. The tissues were processed for histological analysis to evaluate follicular growth, morphology, stromal cell density, and collagen fibers. The results showed that 2.5, 5.0, or 10.0 µg/mL α-pinene increased the percentages of normal follicles but did not influence follicular growth. The α-pinene (10.0 µg/mL) kept the stromal cell density and collagen levels in cultured bovine ovarian tissue like uncultured tissues. Ovarian tissues cultured in control medium had reduced expression of mRNA for NRF2, SOD, CAT, GPX1, and PRDX6, but α-pinene (10.0 µg/mL) increased mRNA levels for NRF2 and PRDX6. In conclusion, 10.0 µg/mL α-pinene improves the follicular survival, preserves stromal cell density and collagen levels, and increases transcripts of NRF2 and PRDX6 after in vitro culture of bovine ovarian tissue.

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One of the prominent peculiarities of nanoparticles (NPs) is their ability to cross biological barriers. Therefore, the development of NPs with different properties has great therapeutic potential in the area of reproduction because the association of drugs, hormones and other compounds with NPs represents an alternative for delivering substances directly at a specific site and for treatment of reproductive problems. Additionally, lipid-based NPs can be taken up by the tissues of patients with ovarian failure, deep endometriosis, testicular dysfunctions, etc., opening up new perspectives for the treatment of these diseases. The development of nanomaterials with specific size, shape, ligand density and charge certainly will contribute to the next generation of therapies to solve fertility problems in humans. Therefore, this review discusses the potential of NPs to treat reproductive disorders, as well as to regulate the levels of the associated hormones. The possible limitations of the clinical use of NPs are also highlighted.

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RESUMO

In vitro culture of ovarian tissue containing primordial follicles is an important tool to study the initiation of follicular populations and to develop efficient culture systems to support in vitro follicle growth. Considering that in vitro culture favours oxidative stress, it is very important to supplement culture medium with antioxidant substances such as Aloe vera extract. This study aims to evaluate the effects of different concentrations of Aloe vera on the distribution of collagen fibres in the extracellular matrix, follicular activation, development and survival in bovine ovarian cortical tissues cultured in vitro, as well as on expression of mRNAs for antioxidant enzymes [superoxide dismutase (SOD), catalase (CAT), peroxiredoxin 6 (PRDX6) and glutathione peroxidase 1 (GPX1)]. To this end, ovarian cortical tissues were cultured for 6 days in α-MEM alone or supplemented with different concentrations of Aloe vera extract (1.0, 5.0, 10.0 or 50.0%). After culture, fragments were fixed and processed histologically to evaluate follicular morphology and activation, as well as the extracellular matrix by staining with picrosirius red. The levels of mRNA for SOD, CAT, PRDX6 and GPX1 in cultured ovarian tissues were evaluated by real-time polymerase chain reaction (PCR). Ovarian tissues cultured with 10.0 or 50.0% Aloe vera had higher percentages of collagen fibres than tissues cultured in control medium. A significant increase in developing follicles was observed in ovarian tissues cultured in α-MEM alone or supplemented with 10% Aloe vera when compared with fresh control or tissues cultured with 1.0% Aloe vera. Presence of Aloe vera did not influence the percentage of morphologically normal follicles when compared with control medium. Ovarian tissues cultured with 50.0% Aloe vera had higher percentages of morphologically normal follicles than those cultured with 10.0% Aloe vera. Furthermore, 10% Aloe vera significantly increased mRNA levels for PRDX6. In conclusion, 10.0% Aloe vera improves extracellular matrix distribution in cultured tissues and increases the expression of mRNA for PRDX6 after 6 days in vitro.

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Sistemas de cultivo in vitro de folículos pré-antrais e de complexos cumulus-oócitos (CCOs) se tornaram uma poderosa ferramenta capaz de subsidiar diversas biotécnicas reprodutivas, bem como possibilitar estudos do efeito de substâncias sobre a dinâmica folicular. No entanto, esses sistemas podem resultar em estresse oxidativo e na diminuição da proteção antioxidante das células, distúrbio associado a altas taxas de morte celular durante o cultivo in vitro. Para contornar esses efeitos adversos, a adição de substâncias antioxidantes aos meios de cultivo tem sido proposta. Abrangendo diferentes classes e mecanismos de ação, compostos antioxidantes têm por função interferir no processo de oxidação para inibir ou retardar o dano oxidativo causado pelos radicais livres às biomoléculas. Além de antioxidantes que têm sido rotineiramente utilizados com esse propósito, recentemente, substâncias alternativas de origem natural como extratos vegetais e óleos essenciais têm ganhado destaque. Dessa forma, diante da influência do estresse oxidativo e da importância do uso de antioxidantes no cultivo celular, a presente revisão objetiva abordar os principais mecanismos de síntese e atuação dos radicais livres bem como o papel dos antioxidantes em protocolos de cultivo in vitro de folículos ovarianos e de CCOs de animais domésticos.(AU)

In vitro culture systems for preantral follicles and cumulus-oocyte complexes (COCs) have become a powerful tool capable of subsidizing several reproductive biotechniques, as well as enabling studies of the effect of substances on follicular dynamics. However, these systems can favor oxidative stress and decrease the antioxidant protection of cells, a disorder associated with high rates of cell death during in vitro culture. To overcome these adverse effects, the addition of antioxidant substances to the culture media has been proposed. Covering different classes and mechanisms of action, these antioxidant compounds have the function of interfering in the oxidation process to inhibit or delay the oxidative damage caused by free radicals to biomolecules. In addition to antioxidants that have been commonly used for this purpose, recently, alternative substances of natural origin such as plant extracts and essential oils have gained prominence. Thus, given the influence of oxidative stress and the importance of using antioxidants in cell culture, this review aims to address the main mechanisms of synthesis and action of free radicals as well as the role of antioxidants in in vitro protocols for ovarian follicles and COCs in domestic animals.(AU)

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Assisted reproductive technology (ART) have contributed to preserve fertility in humans and to increase multiplication of genetically superior animals. Despite being highly practiced worldwide, ART presents some challenges, especially because gametes and embryos are kept in vitro for a variable period of time, and the oxidative stress in vitro can have negative impact on oocyte competence and embryo development. Nanotechnology needs to be considered to help overcome some of those impairments, since it can provide strategies to deliver antioxidants and hormones to gametes and embryos in vitro. The application of nanotechnology to ART can allow the development of new protocols using nanomaterials to improve in vitro oocyte competence and embryo production. This review discusses the applicability of nanomaterials to improve sperm selection, to deliver antioxidants and hormones to preantral follicles, oocytes, and embryos in vitro, as well as the concerns about using nanotechnology in ART.

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This study aimed to evaluate the relationship between antral follicular count (AFC) and ovarian volume (OV), preantral follicular population and survival, meiotic progression and ultrastructure of cumulus-oocyte complexes (COCs) after in vitro maturation. In experiment 1, the relationship between AFC and preantral follicle population and survival was evaluated by classical histology. In experiment 2, the relationship among AFC, OV, ability of oocytes to resume meiosis and ultrastructure of in vitro matured bovine COCs was studied. A positive correlation (P < 0.05) between AFC and the numbers of healthy primordial, degenerate and total follicles was observed, as well as with healthy secondary follicles and total follicles. The numbers of grades I and II oocytes in ovaries of high AFC class were higher compared with those with intermediate or lower AFC. After in vitro maturation, COCs from ovaries of high AFC had a higher percentage of oocytes in metaphase II compared with those of intermediate and low AFC (P < 0.0001). Ovaries of intermediate AFC had a higher percentage of oocytes in metaphase II compared with ovaries with low AFC (P < 0.0001). The proportion of oocytes in metaphase I, telophase I and anaphase I in COCs from ovaries of intermediate AFC (26.04%) was higher (P < 0.05) compared with that seen in COCs of ovaries with high (8.55%) and low (14.15%) AFC. No differences in the ultrastructure of oocytes were seen. In conclusion, after in vitro maturation, cow ovaries with high AFC have higher numbers of oocytes that reach in metaphase II (MII), but they also have higher numbers of degenerated primordial and primary follicles.

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The regulation of folliculogenesis involves a complex interaction among endocrine, paracrine and autocrine factors. The mechanisms involved in the initiation of the growth of the primordial follicle, i.e., follicular activation and the further growth of primary follicles up to the pre-ovulatory stage, are not well understood at this time. The present review focuses on the regulation and development of early stage (primordial, primary, and secondary) folliculogenesis highlighting the mechanisms of primordial follicle activation, growth of primary and secondary follicles and finally transition from secondary to tertiary follicles. We also discuss the importance of in vitro follicle culture for the understanding of folliculogenesis during the preantral phase. Studies suggest that follicular development from primordial to early antral stages is primarily controlled by intra-ovarian ligands but it can also be influenced by many extra-ovarian factors. The control of early folliculogenesis is, therefore, extremely complex because several ligands act through distinct signaling pathways that form sophisticated information networks responding to multiple, often opposing, stimuli. The balance among different stimuli determines follicular survival or death as well as quiescence or activation (growth). The distribution of the ligands and their corresponding receptors varies among follicular compartments and species, and significant changes in gene expression pattern among follicular categories have been reported. Knowing that follicular requirements during early folliculogenesis can be stage-specific and species-specific, in vitro culture studies offer an alternative to evaluate single and combined factors during a specific period of follicular development. Herewith we summarize the main findings obtained in vitro together with the mechanisms regulating folliculogenesis.

RESUMO

The regulation of folliculogenesis involves a complex interaction among endocrine, paracrine and autocrine factors. The mechanisms involved in the initiation of the growth of the primordial follicle, i.e., follicular activation and the further growth of primary follicles up to the pre-ovulatory stage, are not well understood at this time. The present review focuses on the regulation and development of early stage (primordial, primary, and secondary) folliculogenesis highlighting the mechanisms of primordial follicle activation, growth of primary and secondary follicles and finally transition from secondary to tertiary follicles. We also discuss the importance of in vitro follicle culture for the understanding of folliculogenesis during the preantral phase. Studies suggest that follicular development from primordial to early antral stages is primarily controlled by intra-ovarian ligands but it can also be influenced by many extra-ovarian factors. The control of early folliculogenesis is, therefore, extremely complex because several ligands act through distinct signaling pathways that form sophisticated information networks responding to multiple, often opposing, stimuli. The balance among different stimuli determines follicular survival or death as well as quiescence or activation (growth). The distribution of the ligands and their corresponding receptors varies among follicular compartments and species, and significant changes in gene expression pattern among follicular categories have been reported. Knowing that follicular requirements during early folliculogenesis can be stage-specific and speciesspecific, in vitro culture studies offer an alternative to evaluate single and combined factors during a specific period of follicular development. Herewith we summarize the main findings obtained in vitro together with the mechanisms regulating folliculogenesis.(AU)

Assuntos

RESUMO

The regulation of folliculogenesis involves a complex interaction among endocrine, paracrine and autocrine factors. The mechanisms involved in the initiation of the growth of the primordial follicle, i.e., follicular activation and the further growth of primary follicles up to the pre-ovulatory stage, are not well understood at this time. The present review focuses on the regulation and development of early stage (primordial, primary, and secondary) folliculogenesis highlighting the mechanisms of primordial follicle activation, growth of primary and secondary follicles and finally transition from secondary to tertiary follicles. We also discuss the importance of in vitro follicle culture for the understanding of folliculogenesis during the preantral phase. Studies suggest that follicular development from primordial to early antral stages is primarily controlled by intra-ovarian ligands but it can also be influenced by many extra-ovarian factors. The control of early folliculogenesis is, therefore, extremely complex because several ligands act through distinct signaling pathways that form sophisticated information networks responding to multiple, often opposing, stimuli. The balance among different stimuli determines follicular survival or death as well as quiescence or activation (growth). The distribution of the ligands and their corresponding receptors varies among follicular compartments and species, and significant changes in gene expression pattern among follicular categories have been reported. Knowing that follicular requirements during early folliculogenesis can be stage-specific and speciesspecific, in vitro culture studies offer an alternative to evaluate single and combined factors during a specific period of follicular development. Herewith we summarize the main findings obtained in vitro together with the mechanisms regulating folliculogenesis.

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