Animal Reproduction最新文献

This review provides an up-to-date overview of the roles of the oviduct during the periconception period and underlying mechanisms. The functions of the oviduct before, during, and after fertilization are highlighted, with special focus on the effects of epithelial cell contact and luminal secretions on sperm selection mechanisms and acquisition of fertilization ability. The current knowledge on how the oviduct contributes to support fertilization and embryo development via the overall physical milieu (oxygen tension, fluid current, ciliated epithelial cells) and the role of its secretions is also provided. Altogether, the review underlines the unique role of the oviduct during gamete selection and early embryo development, which so far has not been completely possible to mirror when assisted reproductive technologies (ART) are used. Unveiling the most important functional components of oviductal secretions that contribute to better sperm selection, and boost sperm fertilizing ability and early embryo development, can indeed be useful to improve the outcomes of current in vitro systems used in ART.

Embryo development is a complex process that requires several physiological and molecular events to happen harmoniously, and all of this begins with the interaction of the oocyte and sperm. The ability of an oocyte to become a healthy blastocyst is the result of several critical events that are determinants for the successful development of the embryo. Among these events are the sperm's ability to interact with and penetrate the oocyte, carry out syngamy, the developmental competence of the oocyte to support mitotic divisions, and the proper activation of the molecular machinery to regulate the embryo's developmental competence during the early stages of embryonic development. Some of these events originate from either the paternal or maternal side. The focus of this review is to explore the contributions of the paternal side to reproduction in general, with greater emphasis on early embryo development. A deeper understanding of these paternal factors and their influence on embryo development and overall fertility will support the development of new strategies for selecting sires to improve reproductive efficiency in cattle.

Understanding the molecular mechanisms regulating the development of bovine pre-implantation embryos and formation of embryo-like structures (blastoids) is essential to uncover the causes of infertility and develop promising novel assisted reproductive technologies (ARTs). This review presents an updated view of functional genome characterization of bovine pre-implantation development. The use of genomic phenotyping and candidate gene perturbation approaches to uncover molecular factors governing bovine early embryonic development are discussed. This review also delves into the latest breakthroughs in the development of bovine blastoids and highlights key molecular signaling for the creation of bovine blastoids.

The productivity in livestock systems is related to the reproductive efficiency of herds. Over the years, strategies have been developed to improve the reproductive rates of female cattle. Initially, estrus synchronization protocols were developed, however, difficulties related to prolonged postpartum anestrus and estrus observation resulted in low conception rates in these programs. Subsequently, hormonal associations were used to synchronize ovulation and inseminate female cattle at a predetermined time, eliminating the need for estrus observation and improving the fertility rates of cows in postpartum anestrus. Several adjustments were made to improve the response to a timed-artificial insemination (TAI) protocol in different production systems and animal categories. Finally, the development of recombinant drugs and nanotechnology may optimize production systems. Thus, the objective of this review is to detail the research carried out over the years related to the evolution of TAI protocols.

The ability to develop oocytes from the earliest follicular stages through maturation and fertilization in vitro would revolutionize fertility preservation in human medicine and animal breeding. Instead, current assisted reproductive technologies rely only on a limited portion of the female gamete reserve, corresponding to the antral population, while the preantral follicle reserve remains unexploited, mainly due to a lack of knowledge regarding the mechanisms that guide preantral follicle differentiation and folliculogenesis in vitro. This review highlights the efforts made thus far and suggests an approach to studying the mechanisms and ovarian environment to enhance preantral follicle culture systems.

Embryo-maternal communication is a critical process that influences early embryonic development, implantation success, and pregnancy outcomes across mammalian species. This review examines the diverse in vitro systems developed to study this complex dialogue, highlighting their applications, advantages, and limitations. We explore conventional approaches such as two-dimensional (2D) cell cultures, which despite their simplicity, face challenges in replicating the three-dimensional (3D) architecture and cellular functions present in vivo. The review progresses through increasingly sophisticated models, including fluid co-culture systems that incorporate bioactive molecules, explant cultures that maintain tissue architecture, air-liquid interface systems that promote epithelial polarization and differentiation, 3D organoid systems that recapitulate complex structural organization, and organ-on-a-chip platforms that recreate mechanical forces and dynamic conditions. Special attention is given to the emerging role of extracellular vesicles (EVs) as mediators of embryo-maternal communication, transporting crucial molecular signals between the embryo and reproductive tract. By comparing these systems across species and developmental stages, we provide a comprehensive framework for selecting appropriate models based on specific research questions. The integration of these in vitro approaches with advanced analytical techniques offers promising avenues for understanding embryo-maternal cross-talk, potentially leading to improved assisted reproductive technologies and strategies to mitigate early pregnancy loss. As technology advances, the continued refinement of these systems will further illuminate the intricate molecular and cellular mechanisms underlying successful embryo development and implantation.

In the bovine dairy sector, the pursuit of rapid genetic advancement has prompted the adoption of increasingly younger parental figures for both males and females. While physiological limitations and access to gametes impose certain restrictions, the impact of age on gamete quality remains crucial yet poorly understood. We propose that the age effect encompasses environmental factors, which include the metabolic state of the parents and the conditions surrounding gametes and embryos within the reproductive tracts of both sexes. Emerging evidence indicates that this environment significantly influences not only the functionality of gametes and early embryos but also the future phenotype of the offspring. Recent research utilizing transcriptomic and epigenetic molecular analyses in bovine models has demonstrated that the age of both females and males gamete donors, can alter gene expression and programming within the embryo in a similar way that metabolic post partum conditions can. This embryo adaptation to parent's age is similarly noted in variations related to different culture conditions and the in vitro fertilization (IVF) process. A common outcome from these circumstances is the development of embryos operating in "economy" mode, where translation, cell division, and ATP production are diminished, seemingly as an anticipated adaptation to environmental conditions. Furthermore, new epidemiological studies have shown that these alterations can lead to distinct phenotypes, particularly in animals conceived through IVF, underscoring the long-term consequences that may unfold later in their lives.

In vitro embryo production (IVEP) offers an alternative approach for fertility preservation, genetic improvement, and reproductive research. However, in vivo, the female reproductive tract constitutes a dynamic microenvironment that undergoes critical changes crucial to support oocyte maturation, fertilization and embryo development. During IVEP, the absence of maternal-gamete and later maternal-embryo cross-talk can compromises both fertility and embryo development as well as quality. Extracellular vesicles (EVs) derived from the maternal reproductive tract, such as those from follicular fluid, oviductal fluid and uterine fluid, have attracted increasing attention due to their ability to carry bioactive biomolecules and partially restore this bidirectional communication when supplemented during IVEP. Moreover, EVs hold the potential to serve as indicator of the physiological or pathological state of reproductive structures as well as serving as real-time biomarkers. In addition, several studies suggest that EVs offer multiples advantages over conventional synthetics carries, opening new frontiers for modern drug or nucleotide delivery systems. Therefore, this review aims to provide a comprehensive overview of EVs derived from female reproductive tract, exploring their potential applications and challenges in enhancing IVEP outcomes and fertility treatments.

Pregnancy loss (PL) in cattle significantly impacts reproductive efficiency and economic viability of herds. Of particular interest, PL in in vitro embryo production (IVP) systems, represents a major challenge to the success of this technique. Establishment and maintenance of pregnancy is influenced by factors such as fertilization, maternal environment, and embryonic signaling issues. Data on dairy cattle have shown that embryo transfer (ET) may lead to greater initial pregnancy, but greater PL compared to artificial insemination (AI), and the impact of environmental conditions on reproductive outcomes seems to be manageable with proper heat stress mitigation strategies, for example. Data on beef cattle submitted to IVP and ET have shown that recipient cows had greater pregnancy per ET (P/ET) and lower PL compared to recipient heifers, with sex-sorted sperm yielding similar or even greater P/ET than conventional semen. Distinct synchronization protocols for recipients yield different reproductive outcomes, and recipient breed also affects P/ET and PL. Moreover, embryo recipients that express estrus after synchronization, as well as recipients in which better quality embryos are transferred, tend to have greater P/ET and lower PL. These findings highlight the importance of management strategies to improve fertility and reduce PL in embryo recipients.

The collection of early embryonic stages from the donor animal and their in vitro development through to transfer back into a recipient animal has gained enormous importance both in understanding embryo physiology and in its application for breeding purposes. Whereas not so long ago the focus was on embryo retrieval after superovulation from the donor animal, oocyte collection by follicular puncture followed by in vitro production (IVP) is now the main source of bovine embryos. However, as recent years of intensive research have shown, it appears to be very difficult to reproduce the extreme complex in vivo processes under laboratory conditions. Consequently, the quality/developmental capacity of embryos available for cryopreservation/storage/transport and transfer still lags behind that of embryos derived directly from animals. Embryo collection in bovine MOET programs is limited to the success of the animal's hormone treatment, embryo collection itself, and transfer on Day 7. IVP largely bypasses these developmental steps in the animal and focuses primarily on the presence of healthy follicular waves. It uses follicular puncture (ovum pick-up: OPU) to obtain immature oocytes, which undergo a three-stage in vitro process to produce embryos that are transferred to the uterus on Day 7. However, it is now known that important processes take place in the oviduct that have a lasting effect on the further development of the embryo. In animals, however, the development of embryos in the oviduct has not yet received sufficient attention. This review will present some highlights of the use of early embryonic stages from the oviduct in different species, but the scientific work mentioned is also largely based on the recent presentation at the AETE 2023 conference in Heraklion, Greece.