Maternal contributions to pregnancy success: from gamete quality to uterine environment

The establishment and maintenance of a pregnancy that goes to term is sine qua non for the long-term sustainability of dairy and beef cattle operations. The oocyte plays a critical role in providing the factors necessary for preimplantation embryonic development. Furthermore, the female, or maternal, environment where oocytes and embryos develop is crucial for the establishment and maintenance of a pregnancy to term. During folliculogenesis, the oocyte must sequentially acquire meiotic and developmental competence, which are the results of a series of molecular events preparing the highly specialized gamete to return to totipotency after fertilization. Given that folliculogenesis is a lengthy process in the cow, the occurrence of disease, metabolic imbalances, heat stress, or other adverse events can make it challenging to maintain oocyte quality. Following fertilization, the newly formed embryo must execute a tightly planned program that includes global DNA remodeling, activation of the embryonic genome, and cell fate decisions to form a blastocyst within a few days and cell divisions. The increasing use of assisted reproductive technologies creates an additional layer of complexity to ensure the highest oocyte and embryo quality given that in vitro systems do not faithfully recreate the physiological maternal environment. In this review, we discuss cellular and molecular factors and events known to be crucial for proper oocyte development and maturation, as well as adverse events that may negatively affect the oocyte; and the importance of the uterine environment, including signaling proteins in the maternal-embryonic interactions that ensure proper embryo development. We also discuss the impact of assisted reproductive technologies in oocyte and embryo quality and developmental potential, and considerations when looking into the prospects for developing systems that allow for in vitro gametogenesis as a tool for assisted reproduction in cattle.(AU)

Retrospectiva dos principais biomarcadores envolvidos no desenvolvimento folicular e oocitário em mamíferos / Retrospective of the main biomarkers involved in follicular and oocyte development in mammals

A análise da expressão das diversas proteínas relacionadas a foliculogênese e oogênese in vivo e in vitro, através da proteômica, tem demonstrado possíveis biomarcadores celulares. A descoberta desses biomarcadores pode ajudar na elucidação de mecanismos complexos como a foliculogênese (entendimento sobre o crescimento folicular e maturação oocitária), no tratamento de doenças relacionadas a infertilidade feminina, bem como, no aprimoramento de biotécnicas reprodutivas como a manipulação de oócitos inclusos em folículos pré-antrais. Desta forma, a presente revisão abordou as principais proteínas relatadas nos mais novos trabalhos referentes aos estudos proteômicos visando melhores esclarecimentos referentes ao desenvolvimento folicular e oocitário in vivo e in vitro. A escolha dos artigos foi realizada com base nas descobertas mais atuais e do impacto que determinadas proteínas poderiam trazer para melhorar o entendimento da foliculogênese e oogênese nas diferentes espécies de animais mamíferos.(AU)

The analysis of the expression of several proteins related to folliculogenesis and oogenesis in vivo and in vitro, through proteomics, has demonstrated possible cellular biomarkers. The discovery of these biomarkers may help in the elucidation of complex mechanisms such as folliculogenesis (understanding of follicular growth and oocyte maturation), in the treatment of diseases related to female infertility, as well as in the improvement of reproductive biotechniques such as the manipulation of oocytes enclosed in preantral follicles. Thus, the present review addressed the main proteins reported in the newest works related to proteomic studies aiming at better clarifications regarding follicular and oocyte development in vivo and in vitro. The choice of articles was based on the most current discoveries and the impact that certain proteins could bring to improve the understanding of folliculogenesis and oogenesis in different species of mammalian animals.(AU)

Local regulation of antral follicle development and ovulation in monovulatory species

The identification of mutations in the genes encoding bone morphogenetic protein 15 (BMP15) and growth and differentiation factor 9 (GDF9) associated with phenotypes of sterility or increased ovulation rate in sheep aroused interest in the study of the role of local factors in preantral and antral folliculogenesis in different species. An additive mutation in the BMP15 receptor, BMPR1b, which determines an increase in the ovulatory rate, has been introduced in several sheep breeds to increase the number of lambs born. Although these mutations indicate extremely relevant functions of these factors, the literature data on the regulation of the expression and function of these proteins and their receptors are very controversial, possibly due to differences in experimental models. The present review discusses the published data and preliminary results obtained by our group on the participation of local factors in the selection of the dominant follicle, ovulation, and follicular atresia in cattle, focusing on transforming growth factors beta and their receptors. The study of the expression pattern and the functionality of proteins produced by follicular cells and their receptors will allow increasing the knowledge about this local system, known to be involved in ovarian physiopathology and with the potential to promote contraception or increase the ovulation rate in mammals.(AU)

Prolonged use of letrozole causes morphological changes on gonads in Galea spixii

Abstract Letrozole is used as a therapeutic agent in reproductive disorders caused by high estrogen levels. Letrozole inhibits cytochrome P450 aromatase and reduces estrogen levels. However, the effects of long-term use on reproductive traits are unknown. The aim of this study was to evaluate the prolonged use of letrozole in the gonads of rodents (Spix's yellow-toothed cavy; Galea spixii). Forty-eight rodents (24 males and 24 females) were randomly divided into the treated and control groups. Letrozole administration started at 15 days of age and continued weekly until 30, 45, 90, and 120 days of age. The body, testis, and ovary weights were analyzed, as well as the morphological progression of spermatogenesis and folliculogenesis. Macroscopically, body weight gain and gonads weight were increased in the letrozole group. Microscopically, the ovaries of treated females showed stratified epithelium and a cellular disorder of the tunica albuginea. In the testes of treated males, the development of seminiferous tubules was delayed and sperm was absent. The collective findings indicate that the prolonged use of letrozole alters secondary sexual characteristics, and causes weight gain, reproductive changes, and male infertility.

Changes in ovarian morphology and hormone concentrations associated with reproductive seasonality in wild large Japanese field mice (Apodemus speciosus)

Abstract Wild large Japanese field mice (Apodemus speciosus) responses to cyclic seasonal changes are associated with physiological and behavioral changes. However, the detailed regulation of oogenesis in the ovary during the seasonal reproductive cycle in wild large Japanese field mice has not been studied. We assessed the dynamics and changes in ovarian morphology and hormone concentrations associated with reproductive seasonality throughout the year. The stages of the ovarian morphological breeding cycle of wild large Japanese field mice were classified as breeding, transition, and non-breeding periods during the annual reproductive cycle. Measurement of blood estradiol concentrations throughout the year showed that the levels in September and October were higher than those in other months. It is presumed that follicle development starts from a blood estradiol concentration of 38.4 ± 27.1 pg/mL, which marks a shift from the transitional season to the breeding season, followed by the transition to the non-breeding season at 26.1 ± 11.6 pg/mL. These results suggest that seasonal follicle development in wild rodents is correlated with estradiol regulation. We consider this species to be an alternative animal model for studying seasonal reproductive changes and the effects of environmental changes.

Cultivo in vitro de folículos pré-antrais bovinos: revisão, desafios, conquistas e perspectivas futuras / In vitro culture of bovine preantral follicles: review, challenges, achievements and future perspectives

A reprodução animal incide diretamente na eficiência e rentabilidade econômica de um rebanho, sendo considerada um dos fatores de maior importância para os sistemas de produção. Consequentemente, o desenvolvimento e a utilização de biotecnologia são indispensáveis para o aumento da eficiência reprodutiva, do melhoramento genético, da produção de alimentos e geração de riquezas. Nas últimas décadas várias foram as biotécnicas associadas à reprodução animal que apresentaram um grande potencial para a geração de genética, especialmente, ao que se referem aos avanços da reprodução assistida. Estes progressos possibilitaram a utilização de folículos pré-antrais como fonte de oócitos para biotecnologias reprodutivas. Deste modo, a técnica de cultivo in vitro proporciona a retomada do desenvolvimento dos folículos presente na reserva ovariana pela ativação in vitro forçada simulando a ocorrência de distúrbios na foliculogênesse. Até então, apenas a especie murina obteve descendentes vivos através dos folículos primordiais cultivados in vitro. Infelizmente, não há relatos de sucesso em outras espécies, tornando o desenvolvimento de sistemas ideias de cultivo in vitro um desafio. Portanto, o objetivo desta revisão é descrever e discutir os principais avanços da situação atual da pesquisa com folículos pré-antrais inclusos em folículos ovarianos.(AU)

Animal reproduction directly affects the efficiency and economic profitability of a herd, being considered one of the most important factors for production systems. Consequently, the development and use of biotechnology are indispensable for increasing reproductive efficiency, genetic improvement, food production and wealth generation. In the last few decades, biotechnologies associated with animal reproduction have shown great potential for the generation of genetics, especially with regard to advances in assisted reproduction. These advances have enabled the use of pre-antral follicles as a source of oocytes for reproductive biotechnologies. Thus, the in vitro culture technique provides the resumption of the development of follicles present in the ovarian reserve by forced in vitro activation, simulating the occurrence of disturbances in folliculogenesis. Until then, only the murine species obtained living descendants through primordial follicles cultivated in vitro. Unfortunately, there are no reports of success in other species, making the development of ideal in vitro culture systems a challenge.Therefore, the purpose of this review is to describe and discuss the main advances in the current research situation with preantral follicles included in ovarian follicles.(AU)

Cultivo in vitro de folículos pré-antrais bovinos: revisão, desafios, conquistas e perspectivas futuras / In vitro culture of bovine preantral follicles: review, challenges, achievements and future perspectives

A reprodução animal incide diretamente na eficiência e rentabilidade econômica de um rebanho, sendo considerada um dos fatores de maior importância para os sistemas de produção. Consequentemente, o desenvolvimento e a utilização de biotecnologia são indispensáveis para o aumento da eficiência reprodutiva, do melhoramento genético, da produção de alimentos e geração de riquezas. Nas últimas décadas várias foram as biotécnicas associadas à reprodução animal que apresentaram um grande potencial para a geração de genética, especialmente, ao que se referem aos avanços da reprodução assistida. Estes progressos possibilitaram a utilização de folículos pré-antrais como fonte de oócitos para biotecnologias reprodutivas. Deste modo, a técnica de cultivo in vitro proporciona a retomada do desenvolvimento dos folículos presente na reserva ovariana pela ativação in vitro forçada simulando a ocorrência de distúrbios na foliculogênesse. Até então, apenas a especie murina obteve descendentes vivos através dos folículos primordiais cultivados in vitro. Infelizmente, não há relatos de sucesso em outras espécies, tornando o desenvolvimento de sistemas ideias de cultivo in vitro um desafio. Portanto, o objetivo desta revisão é descrever e discutir os principais avanços da situação atual da pesquisa com folículos pré-antrais inclusos em folículos ovarianos.

Animal reproduction directly affects the efficiency and economic profitability of a herd, being considered one of the most important factors for production systems. Consequently, the development and use of biotechnology are indispensable for increasing reproductive efficiency, genetic improvement, food production and wealth generation. In the last few decades, biotechnologies associated with animal reproduction have shown great potential for the generation of genetics, especially with regard to advances in assisted reproduction. These advances have enabled the use of pre-antral follicles as a source of oocytes for reproductive biotechnologies. Thus, the in vitro culture technique provides the resumption of the development of follicles present in the ovarian reserve by forced in vitro activation, simulating the occurrence of disturbances in folliculogenesis. Until then, only the murine species obtained living descendants through primordial follicles cultivated in vitro. Unfortunately, there are no reports of success in other species, making the development of ideal in vitro culture systems a challenge.Therefore, the purpose of this review is to describe and discuss the main advances in the current research situation with preantral follicles included in ovarian follicles.

Oogênese e Foliculogênese em Bovinos / Oogenesis and Folliculogenesis in Cattle

Os ovários desempenham papéis relevantes para o sistema reprodutivo, no qual a função exócrina (ou gametogênica) realiza a maturação e liberação do oócito para a fecundação e a função endócrina (ou esteroidogênica) afeta a síntese, secreção de hormônios e fatores de crescimento. Além disso, existe uma interação entre os fatores endócrinos, autócrinos e parácrinos, atuando em associação com o processo de desenvolvimento folicular e oocitário durante a vida reprodutiva da fêmea. O córtex, porção mais externa do ovário, representa a região funcional onde se localizam os folículos ovarianos e as estruturas lúteas, em diferentes estágios de desenvolvimento e/ou atresia. A região medular localiza-se mais internamente, na maioria das espécies, e sua principal função é nutrir e sustentar o ovário. Apesar da numerosa população folicular presente nos ovários, estabelecida durante a vida fetal, quase todos os folículos encontrados no pool de reserva ovariana, ou seja, 99,9%, não atingem a ovulação. Esses folículos passam por um processo de morte celular conhecido como atresia folicular, tornando o ovário um órgão de baixa produtividade. A elucidação dos mecanismos que regulam a foliculogênese, incluindo o processo de atresia, é importante para o melhor aproveitamento dos folículos na melhoria da eficiência reprodutiva de animais de produção.

The ovaries play roles relevant to the reproductive system, in which the exocrine (or gametogenic) function carries out the maturation and release of the oocyte for fertilization and the endocrine (or steroidogenic) function effects the synthesis and secretion of hormones and growth factors. In addition, there is an interaction between endocrine, autocrine and paracrine factors, acting in association with the follicular and oocyte development process during the female's reproductive life. The cortex, the outermost portion of the ovary, represents the functional region where the ovarian follicles and luteal structures are located, at different stages of development and/or atresia. The medullary region is located more internally, in most species, and its main function is to nourish and support the ovary. Despite the numerous follicular population present in the ovaries, established during fetal life, almost all follicles found in the ovarian reserve pool, i.e., 99.9%, do not reach ovulation. These follicles undergo a process of cell death known as follicular atresia, making the ovary a low-productivity organ. The elucidation of the mechanisms that regulate folliculogenesis, including the atresia process, is important for the better use of follicles in improving the reproductive efficiency of production animals.

Abordagens genéticas e de bioengenharia para o estudo da foliculogênese / Genetic and bioengineering approaches to the study of folliculogenesis

O desenvolvimento de estudos genéticos e de microdispositivos biológicos tem proporcionado a ampliação do conhecimento sobre os complexos eventos que envolvem a reprodução animal. O desafio ainda é imensurável, mas a criação e surgimentos de novas perspectivas para a pesquisa básica tem-se feito presente. Neste trabalho revisamos de maneira suscinta algumas abordagens recentes, utilizadas pela pesquisa básica, sobretudo com o objetivo de lançar luz sobre o desenvolvimento folicular e oocitário. Dessa forma, essa revisão pretende fornecer uma visão geral do uso das tecnologias ômicas e sistema de microfluídica como auxiliadores na compreensão da foliculogênese. Adicionalmente serão apresentadas particularidades inerentes à fisiologia da gametogênese, que incluem ação de microorganismos e mitocôndrias, além do importante papel da comunicação intercelular através das vesículas extracelulares.

The development of genetic studies and biological microdevices has expanded knowledge about the complex events involving animal reproduction. The challenge is still immeasurable, but the creation and emergence of new perspectives for basic research have been present. This paper briefly reviews some recent approaches used in basic research, mainly to shed light on follicular and oocyte development. Thus, this review intends to provide an overview of the use of omics technologies and microfluidics systems as aids in understanding folliculogenesis. Also, it will present particulars inherent in the physiology of gametogenesis, which include microorganisms and mitochondria, in addition to the important role of intercellular communication through extracellular vesicles.

Qualitative and quantitative aspects of atresia during mammalian folliculogenesis / Aspectos qualitativos e quantitativos da atresia durante a foliculogênese em mamíferos

Durante a foliculogênese ovariana, cerca de 99,9% dos folículos morrem pelo processo de atresia folicular. O processo de atresia pode ocorrer pelas vias degenerativa ou apoptótica. Este processo compromete todos os estágios de desenvolvimento folicular, sendo os folículos antrais os mais afetados. Por outro lado, os folículos préantrais são mais resistentes, em função de sua menor taxa metabólica, bem como do número reduzido de células e camadas de células somáticas, células da granulosa e/ou da teca. Embora folículos pré-antrais sejam menos afetados pelo processo de atresia, quando este evento ocorre, pode-se classificá-lo de duas formas, degeneração do tipo I e degeneração do tipo II. Na degeneração do tipo I, o oócito é o compartimento mais comprometido, apresentando núcleo picnótico, embora suas células da granulosa apresentem-se bem organizadas e sem picnose nuclear. Já na degeneração do tipo II, os folículos apresentam oócito retraído e células da granulosa edemaciadas, desorganizadas e sem aderência à membrana basal e ao oócito. É importante destacar que a degeneração do tipo I é mais comum em folículos primordiais e primários, enquanto folículos secundários apresentam mais degeneração do tipo II, ou seja, a medida que os folículos evoluem, a degeneração do tipo II é mais frequente. Considerando todos os aspectos aqui relacionados, essa revisão de literatura abordará aspectos relacionados aos processos de foliculogênese e atresia folicular, bem como as substâncias que induzem a atresia durante a foliculogenese in vitro e in vivo e, ainda, os métodos e parâmetros para análise da atresia em folículos ovarianos. Isto se deve a necessidade de desenvolvimento de protocolos mais eficientes de recuperação dos folículos ovarianos, prevenindo essa grande perda folicular e otimizando as possibilidades de utilização desses materiais biológicos no futuro.

During ovarian foliculogenesis, about 99.9% of follicles die by the follicle atresia process. The atresia process can occur via degeneration or apoptosis. This process compromises all the follicle development stages, with antral follicles being those most affected. On the other hand, the preantral follicles are more residents, since their slow metabolic rate, as well as the reduced number and layers of somatic cells, granulosa and/or thecal cells. Although preantral follicles are less affected by the atresia process, when the event occurs, we can classify it in two ways, type I or type II degenerated follicles. In the type I degeneration the oocyte is the most compromised compartment, showing the picnotic nuclei, although its granulosa cells presented well organized and no picnosis. Already in the type II degeneration, the follicles presented shrunken in the oocyte, and swollen, disorganization and no adhered granulosa cells from the basal membrane and oocyte. It is important to highlight that type I degeneration is the most common in primordial and primary follicles, while in secondary follicles present more type II degeneration, which means that the as follicle evolve, type II degeneration is more frequent. Considering all the aspects related here, this literature review will address aspects related to the folliculogenesis and the process of follicle atresia, as well as substances that induce atresia during in vitro and in vivo folliculogenesis and methods and parameters for analyzing atresia in ovarian follicles. This is due to the need to develop more efficient ovarian follicle recovery protocols, which can prevent this great follicular loss and optimizing the possibilities of use of these biological materials in the future.

Changes in ovarian morphology and hormone concentrations associated with reproductive seasonality in wild large Japanese field mice (Apodemus speciosus)

Wild large Japanese field mice (Apodemus speciosus) responses to cyclic seasonal changes are associated with physiological and behavioral changes. However, the detailed regulation of oogenesis in the ovary during the seasonal reproductive cycle in wild large Japanese field mice has not been studied. We assessed the dynamics and changes in ovarian morphology and hormone concentrations associated with reproductive seasonality throughout the year. The stages of the ovarian morphological breeding cycle of wild large Japanese field mice were classified as breeding, transition, and non-breeding periods during the annual reproductive cycle. Measurement of blood estradiol concentrations throughout the year showed that the levels in September and October were higher than those in other months. It is presumed that follicle development starts from a blood estradiol concentration of 38.4 ± 27.1 pg/mL, which marks a shift from the transitional season to the breeding season, followed by the transition to the non-breeding season at 26.1 ± 11.6 pg/mL. These results suggest that seasonal follicle development in wild rodents is correlated with estradiol regulation. We consider this species to be an alternative animal model for studying seasonal reproductive changes and the effects of environmental changes.(AU)

Prolonged use of letrozole causes morphological changes on gonads in Galea spixii

Letrozole is used as a therapeutic agent in reproductive disorders caused by high estrogen levels. Letrozole inhibits cytochrome P450 aromatase and reduces estrogen levels. However, the effects of longterm use on reproductive traits are unknown. The aim of this study was to evaluate the prolonged use of letrozole in the gonads of rodents (Spix's yellow-toothed cavy; Galea spixii). Forty-eight rodents (24 males and 24 females) were randomly divided into the treated and control groups. Letrozole administration started at 15 days of age and continued weekly until 30, 45, 90, and 120 days of age. The body, testis, and ovary weights were analyzed, as well as the morphological progression of spermatogenesis and folliculogenesis. Macroscopically, body weight gain and gonads weight were increased in the letrozole group. Microscopically, the ovaries of treated females showed stratified epithelium and a cellular disorder of the tunica albuginea. In the testes of treated males, the development of seminiferous tubules was delayed and sperm was absent. The collective findings indicate that the prolonged use of letrozole alters secondary sexual characteristics, and causes weight gain, reproductive changes, and male infertility.(AU)

Hormônio antimülleriano como marcador de fertilidade em fêmeas suínas / Anti-Müllerian hormone as a fertility marker in swine females

O hormônio antimülleriano é conhecido por seu papel na regressão dos ductos de Müller durante a fase de diferenciação sexual dos machos. Ainda assim, esse hormônio atua de forma ainda mais ampla no desenvolvimento de ambos os sexos. O hormônio antimülleriano é diferencialmente expresso em machos e fêmeas durante toda a vida. Nas fêmeas esse hormônio é produzido pelas células da granulosa dos folículos ovarianos e atua modulando os processos de secreção de gonadotrofinas, foliculogênese e esteroidogênese, sendo considerado um biomarcador confiável para fertilidade em diferentes espécies. Apesar de pouquíssimo estudado na espécie suína, alguns trabalhos vêm demonstrando a existência de associações entre os níveis séricos do hormônio antimülleriano e os fenótipos de maior fertilidade. De forma que, o objetivo desta revisão é fazer um levantamento do conhecimento já acumulado acerca da temática, demostrando a importância do desenvolvimento de novos estudos; tendo em vista que o aprofundamento do conhecimento sobre as funções do hormônio antimülleriano nas fêmeas da espécie suína pode contribuir para o melhor entendimento da fisiologia da espécie(AU)

The anti-Müllerian hormone (AMH) is known for its role in the regression of Muller ducts during the phase of sexual differentiation in males. Notwithstanding, this hormone acts more broadly on the development of both sexes. The AMH is differentially expressed both in males and females throughout life. In females, this hormone is produced by granulosa cells of ovarian follicles and modulates the gonadotropin secretion, folliculogenesis, and steroidogenesis, and is considered a reliable fertility biomarker in different species. Despite the lack of studies in the swine species, some reports demonstrated the association between serum levels of AMH and more fertile phenotypes. Therefore, this review aims to survey the current knowledge about this theme, demonstrating the importance of the development of new research, since the strengthening of the knowledge on the functions of the AMH in swine females may contribute to understanding the physiology of the species.(AU)

Hormônio antimülleriano como marcador de fertilidade em fêmeas suínas / Anti-Müllerian hormone as a fertility marker in swine females

O hormônio antimülleriano é conhecido por seu papel na regressão dos ductos de Müller durante a fase de diferenciação sexual dos machos. Ainda assim, esse hormônio atua de forma ainda mais ampla no desenvolvimento de ambos os sexos. O hormônio antimülleriano é diferencialmente expresso em machos e fêmeas durante toda a vida. Nas fêmeas esse hormônio é produzido pelas células da granulosa dos folículos ovarianos e atua modulando os processos de secreção de gonadotrofinas, foliculogênese e esteroidogênese, sendo considerado um biomarcador confiável para fertilidade em diferentes espécies. Apesar de pouquíssimo estudado na espécie suína, alguns trabalhos vêm demonstrando a existência de associações entre os níveis séricos do hormônio antimülleriano e os fenótipos de maior fertilidade. De forma que, o objetivo desta revisão é fazer um levantamento do conhecimento já acumulado acerca da temática, demostrando a importância do desenvolvimento de novos estudos; tendo em vista que o aprofundamento do conhecimento sobre as funções do hormônio antimülleriano nas fêmeas da espécie suína pode contribuir para o melhor entendimento da fisiologia da espécie

The anti-Müllerian hormone (AMH) is known for its role in the regression of Muller ducts during the phase of sexual differentiation in males. Notwithstanding, this hormone acts more broadly on the development of both sexes. The AMH is differentially expressed both in males and females throughout life. In females, this hormone is produced by granulosa cells of ovarian follicles and modulates the gonadotropin secretion, folliculogenesis, and steroidogenesis, and is considered a reliable fertility biomarker in different species. Despite the lack of studies in the swine species, some reports demonstrated the association between serum levels of AMH and more fertile phenotypes. Therefore, this review aims to survey the current knowledge about this theme, demonstrating the importance of the development of new research, since the strengthening of the knowledge on the functions of the AMH in swine females may contribute to understanding the physiology of the species.

Avanços na tecnologia do ovário artificial em ruminantes / Advances in artificial ovary technology in ruminants

O cultivo in vitro de folículos (CIVF), também conhecido como Ovário Artificial, representa uma excelente ferramenta para aumentar nossa compreensão a respeito do controle da foliculogênese inicial, que é crucial para otimizar o uso futuro de um grande número de oócitos imaturos inclusos em folículos pré-antrais (FPs) (principalreserva ovariana) em técnicas de reprodução assistida em humanos, bem como em outras espécies de mamíferos, incluindo os ruminantes. Até o momento, os melhores resultados de CIVF foram relatados em camundongos com a produção de crias vivas a partir de folículos primordiais cultivados in vitro. No entanto, em outras espécies como os ruminantes, esses resultados têm se limitado à produção de um número variável de oócitos maturos e baixas porcentagens de embriões após o cultivo in vitro de folículos pré-antrais secundários tardios isolados de ovários de cabras, búfalas e ovelhas. A presente revisão apresenta e discute os principais achados, limitações e perspectivas da foliculogênese in vitro em ruminantes com foco nas espécies bovinas, caprinas e ovinas.

The in vitro follicle culture (IVFC), also known as artificial ovary, represents an outstanding tool to increase our understanding of the control of early folliculogenesis which is crucial to optimize the future use of a large, number of immature oocytes enclosed in preantral follicles (PFs) (main ovarian reserve) in assisted reproductive techniques in humans as well as in others mammalian species including the ruminants. To date, the best results of IVFC were reported from mice with the production of live offspring from primordial follicles cultured in vitro. However, in other ruminant species, these results have been limited to the production of a variable number of mature oocytes and low percentages of embryos after in vitro culture of goat, buffalo and sheep isolated late secondary preantral follicles. The present review presents and discusses the main findings, limitations, and prospects of in vitro folliculogenesis in ruminants focusing on bovine, caprine, and ovine species.

Avanços na tecnologia do ovário artificial em ruminantes / Advances in artificial ovary technology in ruminants

O cultivo in vitro de folículos (CIVF), também conhecido como Ovário Artificial, representa uma excelente ferramenta para aumentar nossa compreensão a respeito do controle da foliculogênese inicial, que é crucial para otimizar o uso futuro de um grande número de oócitos imaturos inclusos em folículos pré-antrais (FPs) (principalreserva ovariana) em técnicas de reprodução assistida em humanos, bem como em outras espécies de mamíferos, incluindo os ruminantes. Até o momento, os melhores resultados de CIVF foram relatados em camundongos com a produção de crias vivas a partir de folículos primordiais cultivados in vitro. No entanto, em outras espécies como os ruminantes, esses resultados têm se limitado à produção de um número variável de oócitos maturos e baixas porcentagens de embriões após o cultivo in vitro de folículos pré-antrais secundários tardios isolados de ovários de cabras, búfalas e ovelhas. A presente revisão apresenta e discute os principais achados, limitações e perspectivas da foliculogênese in vitro em ruminantes com foco nas espécies bovinas, caprinas e ovinas.(AU)

The in vitro follicle culture (IVFC), also known as artificial ovary, represents an outstanding tool to increase our understanding of the control of early folliculogenesis which is crucial to optimize the future use of a large, number of immature oocytes enclosed in preantral follicles (PFs) (main ovarian reserve) in assisted reproductive techniques in humans as well as in others mammalian species including the ruminants. To date, the best results of IVFC were reported from mice with the production of live offspring from primordial follicles cultured in vitro. However, in other ruminant species, these results have been limited to the production of a variable number of mature oocytes and low percentages of embryos after in vitro culture of goat, buffalo and sheep isolated late secondary preantral follicles. The present review presents and discusses the main findings, limitations, and prospects of in vitro folliculogenesis in ruminants focusing on bovine, caprine, and ovine species.(AU)

Impact of hypotensive action of angiotensin converting enzyme inhibitor on ovarian-intraovarian blood flow and follicles development in goats hormonally stimulated with repeated FSH-ECG treatment

Background: Recent evidence shows that the renin-angiotensin system (RAS) participates in important reproductiveprocesses, such as steroidogenesis, folliculogenesis, oocyte maturation and ovulation. Several studies have proposed touse an angiotensin-converting enzyme (ACE) as a RAS modulator, aiming to improve reproductive efficiency, however,the presence of the main components of this system in reproductive tissues still need to be further investigated, since thephysiological functions seem to be species-specific. The aim of this study was to assess the impact of enalapril-maleate,an ACE inhibitor, during repeated gonadotropins treatment on ovarian blood flow and follicular development in goats.Materials, Methods & Results: Twenty Anglo-Nubian cross-bred goats were equally grouped according to parity (n= 10/group): nulliparous and multiparous parity. In each group, five animals were randomly selected to receive 0.4 mg.kg-1 ofenalapril-maleate during 11 days of estrus synchronization and gonadotropins treatments. The other animals received thesame volume of saline solution. Estrus synchronization of all goats was made by intramuscular ad-ministration of PGF2αanalog, followed 48 h later by intravaginal insertion of a controlled internal drug release device. Forty-eight h after devicewithdrawal, a single dose of 60 mg of FSH plus 300 UI of eCG was administered and repeated every 4 days to complete 3treatments. Transrectal ultrasonography was performed using pulsed and color Doppler to evaluate Doppler velocimetricsparameters of the ovarian artery and intraovarian blood flow, respec-tively, and B-mode real-time ultrasound scanner toevaluate the follicular development. In the females treated with enalapril-maleate was observed a significant reduction ofsystolic and diastolic peak, without difference according to parity. In addition, in the third session of hor-monal stimulation,only the groups (nulliparous and multiparous) not treated with...(AU)

Impact of hypotensive action of angiotensin converting enzyme inhibitor on ovarian-intraovarian blood flow and follicles development in goats hormonally stimulated with repeated FSH-ECG treatment

Background: Recent evidence shows that the renin-angiotensin system (RAS) participates in important reproductiveprocesses, such as steroidogenesis, folliculogenesis, oocyte maturation and ovulation. Several studies have proposed touse an angiotensin-converting enzyme (ACE) as a RAS modulator, aiming to improve reproductive efficiency, however,the presence of the main components of this system in reproductive tissues still need to be further investigated, since thephysiological functions seem to be species-specific. The aim of this study was to assess the impact of enalapril-maleate,an ACE inhibitor, during repeated gonadotropins treatment on ovarian blood flow and follicular development in goats.Materials, Methods & Results: Twenty Anglo-Nubian cross-bred goats were equally grouped according to parity (n= 10/group): nulliparous and multiparous parity. In each group, five animals were randomly selected to receive 0.4 mg.kg-1 ofenalapril-maleate during 11 days of estrus synchronization and gonadotropins treatments. The other animals received thesame volume of saline solution. Estrus synchronization of all goats was made by intramuscular ad-ministration of PGF2αanalog, followed 48 h later by intravaginal insertion of a controlled internal drug release device. Forty-eight h after devicewithdrawal, a single dose of 60 mg of FSH plus 300 UI of eCG was administered and repeated every 4 days to complete 3treatments. Transrectal ultrasonography was performed using pulsed and color Doppler to evaluate Doppler velocimetricsparameters of the ovarian artery and intraovarian blood flow, respec-tively, and B-mode real-time ultrasound scanner toevaluate the follicular development. In the females treated with enalapril-maleate was observed a significant reduction ofsystolic and diastolic peak, without difference according to parity. In addition, in the third session of hor-monal stimulation,only the groups (nulliparous and multiparous) not treated with...

Advances in in vitro folliculogenesis in domestic ruminants

The in vitro follicle culture (IVFC) represents an outstanding tool to enhance our understanding of the control of folliculogenesis and to allow the future use of a large number of immature oocytes enclosed in preantral follicles (PFs) in assisted reproductive techniques in humans as well as in others mammalian species including the ruminants. So far, the best results of IVFC were reported from mice with the production of live offspring from primordial follicles cultured in vitro. Live birth has been obtained after the in vitro culture of bovine early antral follicles. However, in other ruminant species, these results have been limited to the production of a variable number of mature oocytes and low percentages of embryos after in vitro culture of goat, buffalo and sheep isolated secondary preantral follicles. The present review presents and discusses the main findings, limitations, and prospects of in vitro folliculogenesis in ruminants focusing on bovine, caprine, and ovine species.

Advances in in vitro folliculogenesis in domestic ruminants

The in vitro follicle culture (IVFC) represents an outstanding tool to enhance our understanding of the control of folliculogenesis and to allow the future use of a large number of immature oocytes enclosed in preantral follicles (PFs) in assisted reproductive techniques in humans as well as in others mammalian species including the ruminants. So far, the best results of IVFC were reported from mice with the production of live offspring from primordial follicles cultured in vitro. Live birth has been obtained after the in vitro culture of bovine early antral follicles. However, in other ruminant species, these results have been limited to the production of a variable number of mature oocytes and low percentages of embryos after in vitro culture of goat, buffalo and sheep isolated secondary preantral follicles. The present review presents and discusses the main findings, limitations, and prospects of in vitro folliculogenesis in ruminants focusing on bovine, caprine, and ovine species.(AU)