Cell-secreted vesicles in equine ovarian follicular fluid contain miRNAs and proteins: a possible new form of cell communication within the ovarian follicle

Allogenic Follicular Fosterage Technology: Problems, Progress and Potential

The allogeneic follicular fosterage (AFF) technique transfers cumulus-oocyte complexes (COCs) from pubertal female animals to the dominant follicles of adult female animals for further development, allowing the COCs to further develop in a completely in vivo environment. This article reviews the history of AFF and JIVET and their effects on oocyte and embryo development as well as freezing resistance. Improving the efficiency and reproducibility of AFF technology is crucial to its clinical application. This article discusses factors that affect the success rate of AFF, including differences in specific technical procedures and differences between pubertal and adult follicles. Designing standardized procedures and details to improve the synchronization of donor COCs and recipient follicle maturity and reducing the damage to COCs caused by follicular aspiration may be the direction for improving the success rate of AFF in the future.

Oocyte Maturation and miRNAs: Studying a Complicate Interaction to Reveal Possible Biomarkers for Female Infertility

Cellular metabolism, apoptosis, fertilization, and proliferation of granulosa cells belong to a battery of processes where microRNAs can be detected and associated with infertility. The aim of the present review is to focus on mammalian oocyte maturation events and the association between oocyte growth and miRNA expression. PubMed/Medline, Google Scholar and Scopus databases were searched, and 33 studies were included. Regarding the correlation among miRNA expression and the regulation of granulosa cells and cumulus cells, the most important miRNAs were let-7b, let-7c and miR-21. Additionally, the loss of Dicer, an enzyme involved in miRNA biogenesis, is probably a crucial factor in oogenesis, oocyte maturation and embryogenesis. Furthermore, miRNAs interfere with different cellular mechanisms like apoptosis, steroidogenesis, genome integrity, angiogenesis, antioxidative response and, consequently, oocyte maturation. Hence, it is of major importance to clarify the role and mechanism of each miRNA as understanding its action may develop new tools and establish new diagnostic and treatment approaches for infertility and ovarian disorders.

Bubbling beyond the barrier: exosomal RNA as a vehicle for soma-germline communication

'Weismann's barrier' has restricted theories of heredity to the transmission of genomic variation for the better part of a century. However, the discovery and elucidation of epigenetic mechanisms of gene regulation such as DNA methylation and histone modifications has renewed interest in studies on the inheritance of acquired traits and given them mechanistic plausibility. Although it is now clear that these mechanisms allow many environmentally acquired traits to be transmitted to the offspring, how phenotypic information is communicated from the body to its gametes has remained a mystery. Here, we discuss recent evidence that such communication is mediated by somatic RNAs that travel inside extracellular vesicles to the gametes where they reprogram the offspring epigenome and phenotype. How gametes learn about bodily changes has implications not only for the clinic, but also for evolutionary theory by bringing together intra- and intergenerational mechanisms of phenotypic plasticity and adaptation.

Extracellular vesicles secreted by cumulus cells contain microRNAs that are potential regulatory factors of mouse oocyte developmental competence

The role of cumulus cells (CCs) in the acquisition of oocyte developmental competence is not yet fully understood. In a previous study, we matured cumulus-denuded fully-grown mouse oocytes to metaphase II (MII) on a feeder layer of CCs (FL-CCs) isolated from developmentally competent (FL-SN-CCs) or incompetent (FL-NSN-CCs) SN (surrounded nucleolus) or NSN (not surrounding nucleolus) oocytes, respectively. We observed that oocytes cultured on the former could develop into blastocysts, while those matured on the latter arrested at the 2-cell stage. To investigate the CC factors contributing to oocyte developmental competence, here we focused on the CCs' release into the medium of extracellular vesicles (EVs) and on their miRNA content. We found that, during the 15-h transition to MII, both FL-SN-CCs and FL-NSN-CCs release EVs that can be detected, by confocal microscopy, inside the zona pellucida (ZP) or the ooplasm. The majority of EVs are <200 nm in size, which is compatible with their ability to cross the ZP. Next-generation sequencing of the miRNome of FL-SN-CC versus FL-NSN-CC EVs highlighted 74 differentially expressed miRNAs, with 43 up- and 31 down-regulated. Although most of these miRNAs do not have known roles in the ovary, in silico functional analysis showed that seven of these miRNAs regulate 71 target genes with specific roles in meiosis resumption (N = 24), follicle growth (N = 23), fertilization (N = 1), and the acquisition of oocyte developmental competence (N = 23). Overall, our results indicate CC EVs as emerging candidates of the CC-to-oocyte communication axis and uncover a group of miRNAs as potential regulatory factors.

Corpus luteum presence in the bovine ovary increase intrafollicular progesterone concentration: consequences in follicular cells gene expression and follicular fluid small extracellular vesicles miRNA contents

BACKGROUND

It is well described that circulating progesterone (P4) plays a key role in several reproductive events such as oocyte maturation. However, during diestrus, when circulating P4 is at the highest concentrations, little is known about its local impact on the follicular cells such as intrafollicular P4 concentration due to corpus luteum (CL) presence within the same ovary. Based on that, our hypothesis is that the CL presence in the ovary during diestrus alters intrafollicular P4 concentrations, oocyte competence acquisition, follicular cells gene expression, and small extracellular vesicles (sEVs) miRNAs contents.

RESULTS

P4 hormonal analysis revealed that ipsilateral to the CL follicular fluid (iFF) presented higher P4 concentration compared to contralateral follicular fluid (cFF). Furthermore, oocyte maturation and miRNA biogenesis pathways transcripts (ADAMTS-1 and AGO2, respectively) were increased in cumulus and granulosa cells of iFF, respectively. Nevertheless, a RT-PCR screening of 382 miRNAs showed that three miRNAs were upregulated and two exclusively expressed in sEVs from iFF and are predicted to regulate cell communication pathways. Similarly, seven miRNAs were higher and two exclusively expressed from cFF sEVs and are predicted to modulate proliferation signaling pathways.

CONCLUSION

In conclusion, intrafollicular P4 concentration is influenced by the presence of the CL and modulates biological processes related to follicular cell development and oocyte competence, which may influence the oocyte quality. Altogether, these results are crucial to improve our knowledge about the follicular microenvironment involved in oocyte competence acquisition.

Follicular Fluid-Derived Extracellular Vesicles Influence on In Vitro Maturation of Equine Oocyte: Impact on Cumulus Cell Viability, Expansion and Transcriptome

Cumulus cell (CC) expansion is pivotal for oocyte maturation, during which CCs release factors that initiate paracrine signaling within the follicular fluid (FF). The FF is abundant in extracellular vesicles (EVs) that facilitate intercellular communication. Although bovine and murine EVs can control cumulus expansion, these effects have not been observed in equines. This study aimed to assess the impact of FF-derived EVs (ffEVs) on equine CC expansion, viability, and transcriptome. Cumulus-oocyte complexes (COCs) that underwent in vitro maturation (IVM) in the presence (200 µg protein/mL) or absence (control) of ffEVs were assessed for cumulus expansion and viability. CCs were isolated after 12 h of IVM, followed by RNA extraction, cDNA library generation, and subsequent transcriptome analysis using next-generation sequencing. Confocal microscopy images illustrated the internalization of labeled ffEVs by CCs. Supplementation with ffEVs significantly enhanced cumulus expansion in both compacted (Cp, p < 0.0001) and expanded (Ex, p < 0.05) COCs, while viability increased in Cp groups (p < 0.01), but decreased in Ex groups (p < 0.05), compared to the controls. Although transcriptome analysis revealed a subtle effect on CC RNA profiles, differentially expressed genes encompassed processes (e.g., MAPK and Wnt signaling) potentially crucial for cumulus properties and, consequently, oocyte maturation.

Dynamics of extracellular vesicle uptake by mural granulosa cells in mice

Extracellular vesicles (EVs) play an important role in the development and function of mammalian ovarian follicles. However, the mechanisms by which they are taken up by the follicular granulosa cells remain unclear. In addition, while oocytes play a pivotal role in follicular development, the possible interactions between oocyte-derived paracrine factors (ODPFs) and EV signals are unknown. Therefore, this study aimed to elucidate the mechanism of EV uptake and the effects of ODPFs on EV uptake by follicular somatic mural granulosa cells in mice. Fluorescence-labeled transferrin (TRF) and cholera toxin B (CTB), substrates for clathrin- and caveolae-mediated endocytosis, respectively, were taken up by mural granulosa cells in vitro. Their uptake was inhibited by Pitstop 2 and genistein, inhibitors of clathrin and caveolae pathways, respectively. Mural granulosa cells took up EVs, and this uptake was suppressed by Pitstop 2 and genistein. Moreover, ODPFs promoted the uptake of EVs and CTB, but not TRF, by mural granulosa cells. These results suggest that mural granulosa cells take up EVs through both clathrin- and caveolae-mediated endocytosis and that oocytes may promote caveolae-mediated endocytosis to facilitate the uptake of EVs.

Exosomes as Theranostic Agents in Reproduction System

Exosomes (Exos), belonging to extracellular vesicles, are cell-derived nano-sized vesicles with the potential to carry different kinds of biological molecules. Many studies have proved the impacts of exosomal cargo on several biological processes in female and male reproductive systems. It is also hypothesized that changes in exosomal cargo are integral to the promotion of certain pathological conditions, thus Exos can be used as valid biomarkers for the diagnosis of infertility and other abnormal conditions. Here, efforts are made to collect some recent data related to the physiological significance of Exos in the reproductive system, and their potential therapeutic effects. It is anticipated that the current review article will lay the groundwork for elucidating the source and mechanisms by which Exos control the reproductive system additionally supplying fresh methods and concepts for the detection and treatment of disorders associated with fertility for future studies.

lnc RNA LOC102163816 Promotes Proliferation of Porcine Follicular Granulosa Cells Via miR-455-3p/PTK2B/PI3K/AKT Pathway

The proliferation and differentiation of granulosa cells (GCs) is a crucial process in follicular development. However, the molecular regulatory mechanism of follicular proliferation and differentiation of GCs needs further research. Studies have reported that follicular fluid exosomes are involved in regulation of proliferation of GCs, but the specific mechanism is unclear. This study demonstrated that LOC102163816 is upregulated in porcine GCs treated with follicular fluid exosomes. Further study defined LOC102163816 to be a novel long noncoding RNA that is highly homologous to human metastasis-associated lung adenocarcinoma transcript 1 (MALAT1) and enriched in porcine follicular fluid exosomes. We have speculated that LOC102163816 might have a cell-proliferative effect similar to that of MALAT1. We found that overexpression of LOC102163816 promoted transition from the G1 phase to the S phase of the cell cycle, thereby promoting proliferation of GCs. To explore the specific mechanism underlying this promotion of proliferation, miRNA sequencing was performed after overexpression of LOC102163816. Our results showed that LOC102163816 sponged miR-455-3p, promoting expression of protein tyrosine kinase 2 beta (PTK2B), thereby activating the PI3K/AKT signaling pathway to regulate proliferation of porcine follicular GCs. These findings provide useful insights into follicular development.

Metabolomic profiling of exosomes reveals age-related changes in ovarian follicular fluid

BACKGROUND

Female fertility declines with increased maternal age, and this decline is even more rapid after the age of 35 years. Follicular fluid (FF) is a crucial microenvironment that plays a significant role in the development of oocytes, permits intercellular communication, and provides the oocytes with nutrition. Exosomes have emerged as being important cell communication mediators that are linked to age-related physiological and pathological conditions. However, the metabolomic profiling of FF derived exosomes from advanced age females are still lacking.

METHODS

The individuals who were involved in this study were separated into two different groups: young age with a normal ovarian reserve and advanced age. The samples were analysed by using gas chromatography-time of flight mass spectrometry (GC-TOFMS) analysis. The altered metabolites were analysed by using Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis to identify the functions and pathways that were involved.

RESULTS

Our data showed that metabolites in exosomes from FF were different between women of young age and women of advanced age. The set of 17 FF exosomal metabolites (P ≤ 0.05) may be biomarkers to differentiate between the two groups. Most of these differentially expressed metabolites in FF were closely involved in the regulation of oocyte number and hormone levels.

CONCLUSIONS

In this study, we identified differences in the metabolites of exosomes from FF between women of young age and women of advanced age. These different metabolites were tightly related to oocyte count and hormone levels. Importantly, these findings elucidate the metabolites of the FF exosomes and provide a better understanding of the nutritional profiles of the follicles with age.

miRNA profiling of granulosa cell-derived exosomes reveals their role in promoting follicle development

To explore whether granulosa cell (GC)-derived exosomes (GC-Exos) and follicular fluid-derived exosomes (FF-Exos) have functional similarities in follicle development and to establish relevant experiments to validate whether GC-Exos could serve as a potential substitute for follicular fluid-derived exosomes to improve folliculogenesis. GC-Exos were characterized. MicroRNA (miRNA) profiles of exosomes from human GCs and follicular fluid were analyzed in depth. The signature was associated with folliculogenesis, such as phosphatidylinositol 3 kinases-protein kinase B signal pathway, mammalian target of rapamycin signal pathway, mitogen-activated protein kinase signal pathway, Wnt signal pathway, and cyclic adenosine monophosphate signal pathway. A total of five prominent miRNAs were found to regulate the above five signaling pathways. These miRNAs include miRNA-486-5p, miRNA-10b-5p, miRNA-100-5p, miRNA-99a-5p, and miRNA-21-5p. The exosomes from GCs and follicular fluid were investigated to explore the effect on folliculogenesis by injecting exosomes into older mice. The proportion of follicles at each stage is counted to help us understand folliculogenesis. Exosomes derived from GCs were isolated successfully. miRNA profiles demonstrated a remarkable overlap between the miRNA profiles of FF-Exos and GC-Exos. The shared miRNA signature exhibited a positive influence on follicle development and activation. Furthermore, exosomes derived from GCs and follicular fluid promoted folliculogenesis in older female mice. Exosomes derived from GCs had similar miRNA profiles and follicle-promoting functions as follicular fluid exosomes. Consequently, GC-Exos are promising for replacing FF-Exos and developing new commercial reagents to improve female fertility.

Extracellular Vesicles in Domestic Animals: Cellular Communication in Health and Disease

Apoptotic and healthy cells of domestic animals release membrane-enclosed particles from their plasma membrane. These special structures, called extracellular vesicles, play an important role in intercellular communication. In the past, it was believed that their function was mainly to dispose unwanted cell contents and to help maintain cell homeostasis. However, we now know that they have important roles in health and disease and have diagnostic value as well as great potential for therapy in veterinary medicine. Extracellular vesicles facilitate cellular exchanges by delivering functional cargo molecules to nearby or distant tissues. They are produced by various cell types and are found in all body fluids. Their cargo reflects the state of the releasing parent cell, and despite their small size, this cargo is extraordinarily complex. Numerous different types of molecules contained in vesicles make them an extremely promising tool in the field of regenerative veterinary medicine. To further increase research interest and discover their full potential, some of the basic biological mechanisms behind their function need to be better understood. Only then will we be able to maximize the clinical relevance for targeted diagnostic and therapeutic purposes in various domestic animal species.

Effects of follicular fluid exosomes on in vitro maturation of porcine oocytes

Exosomes are related to effective communication between cells. In this study we aimed to investigate the effect of porcine follicular fluid exosomes (FF-Exo) on cumulus expansion, oocyte mitochondrial membrane potential, and maturation in in vitro culture. We used different concentrations of FF-Exo (Exo-0, Exo-1, Exo-10, Exo-20, and Exo-40) and added them to an oocyte maturation medium. Transmission electron microscopy (TEM), nanoparticle tracking analysis (NTA) and western blot (WB) showed that the isolated samples were exosomes. Immunofluorescence showed that exosomes could be taken up by cumulus cells. Compared with the Exo-0 group, there was no significant difference in oocyte maturation rate in the Exo-1 group (p > 0.05), while the Exo-10 group (p < 0.05), Exo-20 group (p < 0.01) and Exo-40 group (p < 0.01) significantly increased. The maturation rate of the Exo-20 and Exo-40 groups was the highest, and there was no significant difference between the two groups (p > 0.05). However, different concentrations of treatment could not effectively induce cumulus expansion and the results of JC1 showed that it had no significant effect on mitochondrial membrane potential (p > 0.05). In conclusion, the results suggest that porcine FF-Exo are involved in oocyte nuclear maturation.

Differential expression of plasma‑derived exosomal miRNAs in polycystic ovary syndrome as a circulating biomarker

Identifying biomarkers with high sensitivity and stability is helpful for the timely and accurate diagnosis, and effective management of polycystic ovary syndrome (PCOS), a long-term, progressive endocrine disorder. Circulating microRNAs (miRNAs/miRs) are being increasingly recognized as promising biomarkers given the stability and enrichment of miRNAs in exosomes. The high sensitivity of the reverse transcription-quantitative PCR (RT-qPCR) has enabled accurate quantification of miRNAs and small fragments, present in a low abundance, in the circulation. In the present study, the potential of miRNAs in the diagnosis of PCOS was evaluated. Exosomal miRNAs were extracted and screened, and three miRNAs (miR-4488, miR-151a-5p, and miR-223-3p) were found to be differentially expressed between the PCOS group and age-matched controls by sequencing analysis. RT-qPCR was performed on a clinically confirmed PCOS cohort (n=107) and a non-PCOS control cohort (n=101) from South China to validate the PCOS-related RNA sequencing results. miR-151a-5p and miR-4488 expression levels were significantly upregulated, and miR-223-3p expression was downregulated in the PCOS cohort compared with the control cohort (P<0.05). The areas under the receiver operating characteristic curve were 0.889, 0.871, and 0.664 for miR-4488, miR-151a-5p, and miR-223-3p, respectively. Combining anti-Müllerian hormone levels with the three miRNAs resulted in an AUC of 0.967, and higher sensitivity and specificity. These results suggest that miRNAs may prove useful in the early diagnosis and effective management of PCOS, and that these three miRNAs may be involved in the pathogenesis of PCOS. In addition, bioinformatics analysis showed that these three exosomal miRNAs were involved in key signaling pathways related to cancer.

Specific expression profile of follicular fluid-derived exosomal microRNAs in patients with diminished ovarian reserve

BACKGROUND

Diminished ovarian reserve (DOR) is defined as a reduction in ovarian reserve and oocyte quality. The pathophysiology of DOR has not been completely explained as of yet. Scholars have uncovered a large number of exosomes that have been detected in follicular fluid, and exosomal miRNAs have been proven to play a critical role in controlling ovarian disorders and follicle formation. We focused on the expression profile of follicular fluid-derived exosomal microRNAs (miRNAs) and attempted to understand if their role is connected to the pathomechanism of DOR.

METHODS

The follicular fluid-derived differentially expressed exosomal miRNAs (DEmiRs) between patients with DOR and those with normal ovarian function were investigated using the next-generation sequencing (NGS) method. The main metabolic and signaling pathways of DEmiRs were identified using the KEGG pathway database, disease ontology (DO) analysis, and gene ontology (GO) analysis. In the end, a Protein-Protein Interaction (PPI) network was built to search for exosomal miRNAs and their target genes that were potentially strongly connected with DOR.

RESULTS

In comparison to normal controls, 52 DEmiRs were discovered in follicular fluid-derived exosomes of DOR patients, of which 19 were up-regulated and 33 were down-regulated (|log2(fold change) |>2, P < 0.05). GO, DO analysis, and the KEGG pathway database revealed that many of these DEmiRs have broad biological roles that are connected to ovarian function and disorders. The top ten DEmiRs in terms of expression were then chosen for miRNA-mRNA interaction analysis. Totally, 8 experimentally supported miRNAs (hsa-miR-1246, hsa-miR-483-3p, hsa-miR-122-5p, hsa-miR-130b-3p, hsa-miR-342-3p, hsa-miR-625-3p, hsa-miR-675-3p, and hsa-miR-134-5p) and 126 target genes were filtrated by utilizing Cytoscape software. The module analysis findings of the PPI network showed that the main module cluster with a score > 6.0 (MCODE score = 15) had six hub genes, including IGFR, VEGFA, KRAS, ERBB2, RHOA, and PTEN (MCODE score = 11.472).

CONCLUSION

Our data suggested a special expression profile of follicular fluid-derived exosomal miRNAs in patients with DOR, which was probably correlated to ovarian dysfunction and follicle formation. These results may give a unique insight into a better understanding of the molecular process in the pathogenesis of DOR or other ovarian diseases.

Essential Role of Granulosa Cell Glucose and Lipid Metabolism on Oocytes and the Potential Metabolic Imbalance in Polycystic Ovary Syndrome

Granulosa cells are crucial for the establishment and maintenance of bidirectional communication among oocytes. Various intercellular material exchange modes, including paracrine and gap junction, are used between them to achieve the efficient delivery of granulosa cell structural components, energy substrates, and signaling molecules to oocytes. Glucose metabolism and lipid metabolism are two basic energy metabolism pathways in granulosa cells; these are involved in the normal development of oocytes. Pyruvate, produced by granulosa cell glycolysis, is an important energy substrate for oocyte development. Granulosa cells regulate changes in intrafollicular hormone levels through the processing of steroid hormones to control the development process of oocytes. This article reviews the material exchange between oocytes and granulosa cells and expounds the significance of granulosa cells in the development of oocytes through both glucose metabolism and lipid metabolism. In addition, we discuss the effects of glucose and lipid metabolism on oocytes under pathological conditions and explore its relationship to polycystic ovary syndrome (PCOS). A series of changes were found in the endogenous molecules and ncRNAs that are related to glucose and lipid metabolism in granulosa cells under PCOS conditions. These findings provide a new therapeutic target for patients with PCOS; additionally, there is potential for improving the fertility of patients with PCOS and the clinical outcomes of assisted reproduction.

Spermatozoa, acts as an external cue and alters the cargo and production of the extracellular vesicles derived from oviductal epithelial cells in vitro

The oviduct provides optimum physiological and biochemical milieu essential for successful fertilization, early embryo development and facilitates functional maturation of spermatozoa. A study has revealed that spermatozoa alters the gene expression in bovine oviductal epithelial cells (BOECs) remotely via bio-active particles, thus acting as a cue to the oviduct prior to their arrival. However, very little attention has been paid to the question of whether spermatozoa could alter the cargo of extracellular vesicles (EVs) derived from BOECs. Therefore, the aim of this study was to investigate the alterations in small non-coding RNAs in EVs cargo derived from BOECs when incubated with spermatozoa in contact and non-contact co-culture models. After 4 h of incubation the EVs were isolated from the conditioned media, followed by small non-coding sequencing of the BOEC derived EVs. Our results revealed that EVs from both co-culture models contained distinct cargo in form of miRNA, fragmented mRNA versus control. The pathway enrichment analysis revealed that EV miRNA from direct co-culture were involved in the biological processes associated with phagocytosis, macroautophagy, placenta development, cellular responses to TNF and FGF. The mRNA fragments also varied within the different groups and mapped to the exonic regions of the transcriptome providing vital insights regarding the changes in cellular transcriptome on the arrival of spermatozoa. The findings of this study suggest that spermatozoa, in contact as well as remotely, alter the EV cargo of female reproductive tract epithelial cells which might be playing an essential role in pre and post-fertilization events.

Therapeutic Potential of Extracellular Vesicles from Different Stem Cells in Chronic Wound Healing

Wound healing has long been a complex problem, especially in chronic wounds. Although debridement, skin grafting, and antimicrobial dressings have been used to treat chronic wounds, their treatment period is long, expensive, and has specific rejection reactions. The poor treatment results of traditional methods have caused psychological stress to patients and a substantial economic burden to society. Extracellular vesicles (EVs) are nanoscale vesicles secreted by cells. They play an essential role in intercellular communication. Numerous studies have confirmed that stem cell-derived extracellular vesicles (SC-EVs) can inhibit overactive inflammation, induce angiogenesis, promote re-epithelization, and reduce scar formation. Therefore, SC-EVs are expected to be a novel cell-free strategy for chronic wound treatment. We first summarize the pathological factors that hinder wound healing and discuss how SC-EVs accelerate chronic wound repair. And then, we also compare the advantages and disadvantages of different SC-EVs for chronic wound treatment. Finally, we discuss the limitations of SC-EVs usage and provide new thoughts for future SC-EVs research in chronic wound treatment.

Review: Environment of the ovulatory follicle: modifications and use of biotechnologies to enhance oocyte competence and increase fertility in cattle

The oocyte is the basis of life, supporting development from a fertilized cell to an independent multicellular organism. The oocyte's competence to drive the first cell cycles postfertilization are critical to embryonic survival and subsequent successful pregnancy. Coupled with the complex processes of follicle assembly, activation, differentiation, growth, and terminal maturation, oocyte developmental competence is gradually acquired during oocyte growth and meiotic maturation. Most reproduction management technologies and interventions are centered around these highly coordinated processes, targeting the ovarian follicle and the oocyte within. Thus, our objective was to highlight key aspects of oocyte and follicle development in cattle, and to discuss recent advances in oocyte and follicle-centered reproductive biotechnologies.

Oocyte-cumulus cells crosstalk: New comparative insights

Mammalian follicles are constituted of a complex structure composed of several layers of granulosa cells surrounding the oocyte and of theca cells that reside beneath its basement membrane. During folliculogenesis, granulosa cells separate into two anatomically and functionally distinct sub-types; the mural cells lining the follicle wall and the oocyte-surrounding cumulus cells, i.e. those in intimate metabolic contact with the oocyte. The cumulus cells connecting with the oocyte have trans-zonal cytoplasmic projections which, penetrating the zona pellucida, form the cumulus-oocyte complex. The connections through gap junctions allow the transfer of small molecules between oocyte and cumulus cells, such as ions, metabolites, and amino acids necessary for oocyte growth, as well as small regulatory molecules that control oocyte development. The bi-directional communication between the oocyte and cumulus cells is crucial for the development and functions of both cell types. Our current knowledge of the relationship between the oocyte and its surrounding cumulus cells continues to change as we gain a greater understanding of factors regulating oocyte development and folliculogenesis. This review will mainly focus on the reciprocal interaction between oocytes and cumulus cells during the latter stages of follicle development i.e. through antral development to periovulatory events including oocyte maturation, expansion, and degradation of the cumulus matrix.

Granulosa cell-derived extracellular vesicles mitigate the detrimental impact of thermal stress on bovine oocytes and embryos

Climate change-induced global warming results in rises in body temperatures above normal physiological levels (hyperthermia) with negative impacts on reproductive function in dairy and beef animals. Extracellular vesicles (EVs), commonly described as nano-sized, lipid-enclosed complexes, harnessed with a plethora of bioactive cargoes (RNAs, proteins, and lipids), are crucial to regulating processes like folliculogenesis and the initiation of different signaling pathways. The beneficial role of follicular fluid-derived EVs in inducing thermotolerance to oocytes during in vitro maturation (IVM) has been evidenced. Here we aimed to determine the capacity of in vitro cultured granulosa cell-derived EVs (GC-EVs) to modulate bovine oocytes’ thermotolerance to heat stress (HS) during IVM. Moreover, this study tested the hypothesis that EVs released from thermally stressed GCs (S-EVs) shuttle protective messages to provide protection against subsequent HS in bovine oocytes. For this, sub-populations of GC-EVs were generated from GCs subjected to 38.5°C (N-EVs) or 42°C (S-EVs) and supplemented to cumulus-oocyte complexes (COCs) matured in vitro at the normal physiological body temperature of the cow (38.5°C) or HS (41°C) conditions. Results indicate that S-EVs improve the survival of oocytes by reducing ROS accumulation, improving mitochondrial function, and suppressing the expression of stress-associated genes thereby reducing the severity of HS on oocytes. Moreover, our findings indicate a carryover impact from the addition of GC-EVs during oocyte maturation in the development to the blastocyst stage with enhanced viability.

MicroRNAs, small regulatory elements with significant effects on human implantation: a review

Embryo implantation is a critical process for achieving a successful pregnancy and live birth. The proper implantation must have a synchronized interaction between blastocyst and a receptive endometrium. Many genes are involved in the modulation of precise molecular events during implantation. MicroRNAs (miRNAs) have been extensively reported as gene regulatory molecules on post-transcriptional levels involved in various biological processes such as gametogenesis, embryogenesis, and the quality of sperm, oocyte, and embryos. A plethora of evidence has demonstrated critical roles for miRNAs in regulating genes involved in the implantation process; hence, dysregulation of miRNAs could be associated with significant impairments in implantation, such as recurrent implantation failure. In addition to the indispensable role of miRNAs in the intracellular control of gene expression, they can also be secreted into extracellular fluid and circulation. Therefore, miRNAs in body fluids and blood may be exploited as non-invasive diagnostic biomarkers for different pathological and physiological conditions. Recently, several studies have focused on the discovery of miRNAs function in the implantation process by appraising miRNAs and their target genes in human embryos, endometrial tissue, and cell culture models. Moreover, it was revealed that there could be a significant association between endometrial receptivity or implantation status and the expression of miRNAs in human body fluids, reinforcing their role as non-invasive biomarkers. In the current work, we reviewed the studies concerning the role of intracellular and extracellular miRNAs in human implantation and the influence of their dysregulation on implantation disorders.

Low-density small extracellular vesicles in bovine follicular fluid carrying let-7i target FASLG to inhibit granulosa cells apoptosis

Apoptosis of granulosa cells is a key factor in mammalian follicular atresia. It has a significant impact on oocyte development and maturation. Extracellular vesicles (EVs) are a group of highly heterogeneous population. Previous studies have found that ovarian follicular fluid is rich in EVs. In the present study, the follicular fluid of 3-5 mm follicles from bovine ovaries without corpus luteum was collected, and a subtype of small EVs (sEVs), low-density small EVs (LD-sEVs), was successfully isolated by differential ultracentrifugation combined with iodixanol density gradient centrifugation. LD-sEVs were identified using transmission electron microscope, nanoparticle tracking analysis and Western blot. Flow cytometry, Quantitative reverse transcription PCR (RT-qPCR), Western blot, and other methods were used to detect the effect of LD-sEVs on follicular granulosa cell apoptosis. After that, let-7i, a highly expressed miRNA component in LD-sEVs, was screened and target validation was carried out in granulosa cells. The results showed that LD-sEVs could be taken up by granulosa cells and inhibited the apoptosis. Further research found that let-7i inhibits the apoptosis of granulosa cells by targeting FASLG. It plays an important role in regulating the apoptosis of follicular granulosa cells, which may affect follicular development.

Exosomes: New regulators of reproductive development

Exosomes are a subtype of extracellular vesicles (EVs) with a size range between 30 and 150 ​nm, which can be released by the majority of cell types and circulate in body fluid. They function as a long-distance cell-to-cell communication mechanism that modulates the gene expression profile and fate of target cells. Increasing evidence has indicated exosomes' central role in regulating various complex reproductive processes. However, to our knowledge, a review that focally and vividly describes the role of exosomes in reproductive development is still lacking. This review highlights our knowledge about the contribution of exosomes to early mammalian reproduction, such as gametogenesis, fertilization, early embryonic development, implantation, placentation and pregnancy. The discussion is primarily drawn from literature pertaining to the mammalian lineage with emphasis on the roles of exosomes in human reproduction and laboratory and livestock models.

Molecular characterization of extracellular vesicles derived from follicular fluid of women with and without PCOS: integrating analysis of differential miRNAs and proteins reveals vital molecules involving in PCOS

PURPOSE

To elucidate the characterization of extracellular vesicles (EVs) in the follicular fluid-derived extracellular vesicles (FF-EVs) and discover critical molecules and signaling pathways associating with the etiology and pathobiology of PCOS, the differentially expressed miRNAs (DEmiRNAs) and differentially expressed proteins profiles (DEPs) were initially explored and combinedly analyzed.

METHODS

First, the miRNA and protein expression profiles of FF-EVs in PCOS patients and control patients were compared by RNA-sequencing and tandem mass tagging (TMT) proteomic methods. Subsequently, Gene Ontology and the Kyoto Encyclopedia of Genes and Genomes were used to analyze the biological function of target genes of DEmiRNAs and DEPs. Finally, to discover the functional miRNA-target gene-protein interaction pairs involved in PCOS, DEmiRs target gene datasets and DEPs datasets were used integratedly.

RESULTS

A total of 6 DEmiRNAs and 32 DEPs were identified in FF-EVs in patients with PCOS. Bioinformatics analysis revealed that DEmiRNAs target genes are mainly involved in thiamine metabolism, insulin secretion, GnRH, and Apelin signaling pathway, which are closely related to the occurrence of PCOS. DEPs also closely related to hormone metabolism processes such as steroid hormone biosynthesis. In the analysis integrating DEmiRNAs target genes and DEPs, two molecules, GRAMD1B and STPLC2, attracted our attention that are closely associated with cholesterol transport and ceramide biosynthesis, respectively.

CONCLUSION

Dysregulated miRNAs and proteins in FF-EVs, mainly involving in hormone metabolism, insulin secretion, neurotransmitters regulation, adipokine expression, and secretion, may be closely related to PCOS. The effects of GRAMD1B and STPLC2 on PCOS deserve further study.

Intercellular communication in the cumulus-oocyte complex during folliculogenesis: A review

During folliculogenesis, the oocyte and surrounding cumulus cells form an ensemble called the cumulus-oocyte complex (COC). Due to their interdependence, research on the COC has been a hot issue in the past few decades. A growing body of literature has revealed that intercellular communication is critical in determining oocyte quality and ovulation. This review provides an update on the current knowledge of COC intercellular communication, morphology, and functions. Transzonal projections (TZPs) and gap junctions are the most described structures of the COC. They provide basic metabolic and nutrient support, and abundant molecules for signaling pathways and regulations. Oocyte-secreted factors (OSFs) such as growth differentiation factor 9 and bone morphogenetic protein 15 have been linked with follicular homeostasis, suggesting that the communications are bidirectional. Using advanced techniques, new evidence has highlighted the existence of other structures that participate in intercellular communication. Extracellular vesicles can carry transcripts and signaling molecules. Microvilli on the oocyte can induce the formation of TZPs and secrete OSFs. Cell membrane fusion between the oocyte and cumulus cells can lead to sharing of cytoplasm, in a way making the COC a true whole. These findings give us new insights into related reproductive diseases like polycystic ovary syndrome and primary ovarian insufficiency and how to improve the outcomes of assisted reproduction.

Messenger roles of extracellular vesicles during fertilization of gametes, development and implantation: Recent advances

Extracellular vesicles (EVs) have become a research hotspot in recent years because they act as messengers between cells in the physiological and pathological processes of the human body. It can be produced by the follicle, prostate, embryo, uterus, and oviduct in the reproductive field and exists in the extracellular environment as follicular fluid, semen, uterine cavity fluid, and oviduct fluid. Because extracellular vesicles are more stable at transmitting information, it allows all cells involved in the physiological processes of embryo formation, development, and implantation to communicate with one another. Extracellular vesicles carried miRNAs and proteins as mail, and when the messenger delivers the mail to the recipient cell, the recipient cell undergoes a series of changes. Current research begins with intercepting and decoding the information carried by extracellular vesicles. This information may help us gain a better understanding of the secrets of reproduction, as well as assist reproductive technology as an emerging marker and treatment.

MicroRNA Profiling Using a PCR-Based Method

MicroRNAs (miRNAs) are small non-coding RNA molecules involved in the post-transcriptional regulation of specific mRNA targets, thus possibly controlling many biological processes. The miRNA profiling analysis can contribute to understanding several signaling pathways, as biomarkers for molecular diagnostic, as well as potential to be used as therapeutic targets. The miRNAs expression can be analyzed by quantitative reverse transcription PCR (RT-qPCR), microarrays, and RNA sequencing. The RT-qPCR method is sensitive and specific and has a lower cost when compared to other techniques as microarrays and RNA sequencing. Therefore, the protocol presented in this chapter describes step by step all the details to perform miRNA analysis using primer-based RT-qPCR.

Follicular fluid extracellular vesicle miRNAs and ovarian aging

The decrease in the reproductive potential due to aging occurs as a gradual decline in the quantity and quality of the ovarian reserve, a phenomenon associated with risk of miscarriage, pregnancy loss, low ovarian stimulation, and oocyte abnormalities, such as chromosomal aneuploidies. Numerous studies have shown that the fertility potential of older women is decreased by changes to the cellular composition of the follicles. Additionally, a unique method of cellular communication has been identified which involves the release of extracellular vesicles (EVs) in various body fluids including follicular fluid (FF). The changing composition of EVs especially non-coding RNAs, such as miRNAs has been documented across a broad range of cell types during aging. Accordingly, alterations of miRNA cargo within FF-derived EVs due to increased age may serve as a potential predictor of oocyte quality. In this review we examine the relationship between FF EV miRNAs and ovarian aging.

High body energy reserve influences extracellular vesicles miRNA contents within the ovarian follicle

Aiming to evaluate the effects of increased body energy reserve (BER) in Nellore cows' reproductive efficiency, cows were fed with different nutritional plans to obtain animals with high BER (HBER; Ad libitum diet) and moderate BER (MBER: cows fed 70% of HBER group ingestion). To evaluate the BER, cows were weekly weighted and evaluated for subcutaneous fat thickness and insulin serum concentration along the experimental period. At the end of the experimental period, animals were submitted to estrous synchronization and artificial insemination. Animals were slaughtered approximately 120 h after ovulation induction and the reproductive tracts were collected for embryo recovery and samples collection. Cumulus-oocyte-complexes (COC) and follicular fluid were collected from 3-6 mm in diameter ovarian follicles to perform miRNA analysis of cumulus cells (CC) and extracellular vesicles from follicular fluid (EV FF). As expected, differences were observed among MBER and HBER groups for body weight, fat thickness, and insulin serum concentration. HBER animals showed lower ovulation and embryo recovery rates compared to MBER animals. Different miRNAs were found among CC and EV FF within groups, suggesting that the BER may influence follicular communication. This suggests that small follicles (3-6 mm diameter) are already under BER effects, which may be greater on later stages of follicular development.

Immune-related mechanisms and immunotherapy in extragonadal germ cell tumors

Purpose of review

Extragonadal germ cell tumors (EGCTs) are relatively rare tumors, accounting for 1%-5% of all GCTs. In this review, we summarize the current research progress regarding the pathogenesis, diagnosis, and treatment of EGCTs from an immunology perspective.

Recent findings

The histological origin of EGCTs is related to a gonadal origin, but they are located outside the gonad. They show great variation in morphology and can occur in the cranium, mediastinum, sacrococcygeal bone, and other areas. The pathogenesis of EGCTs is poorly understood, and their differential diagnosis is extensive and challenging. EGCT behavior varies greatly according to patient age, histological subtype, and clinical stage.

Summary

This review provides ideas for the future application of immunology in the fight against such diseases, which is a hot topic currently.

Distribution of tetraspanins in bovine ovarian tissue and fresh/vitrified oocytes

Tetraspanin proteins are mostly known as organizers of molecular complexes on cell membranes, widely expressed on the surface of most nucleated cells. Although tetraspanins participate in many physiological processes of mammals, including reproduction, their relevance to the processes of folliculogenesis and oogenesis has not yet been fully elucidated. We bring new information regarding the distribution of tetraspanins CD9, CD81, CD151, CD82, and CD63 at different stages of follicular development in cattle. The found distribution of tetraspanin CD9, CD63, and integrin alpha V in similar areas of ovarian tissue outlined their possible cooperation. We also describe yet-unknown distribution patterns of CD151, CD82, and CD63 on immature and mature bovine oocytes. The unique localization of tetraspanins CD63 and CD82 in the zona pellucida of bovine oocytes suggested their involvement in transzonal projections. Furthermore, we present an unchanged distribution pattern of the studied tetraspanins in vitrified mature bovine oocytes. The immunofluorescent analysis was supplemented by in silico data addressing tetraspanins expression in the ovarian cells and oocytes across several species. The obtained results suggest that in the study of the oocyte development and potentially the fertilization process of cattle, the role of tetraspanins and integrins should also be taken into account.

The potential of sertoli cells (SCs) derived exosomes and its therapeutic efficacy in male reproductive disorders

In the male reproductive system, seminiferous tubules in testis are lined by a complex stratified epithelium containing two distinct populations of cells, spermatogenic cells that develop into spermatozoa, and sertoli cells (SCs) that mainly support and nourish spermatogenic cell lineage as well as exerting powerful effect on men reproductive capacity. Different varieties of proteins, hormones, exosomes and growth factors are secreted by SCs. There are different kinds of junctions found between SCs called BTB. It was elucidated that complete absence of BTB or its dysfunction leads to infertility. To promote spermatogenesis, crosstalk of SCs with spermatogenic cells plays an important role. The ability of SCs to support germ cell productivity and development is related to its various products carrying out several functions. Exosomes (EXOs) are one of the main EVs with 30-100 nm size generating from endocytic pathway. They are produced in different parts of male reproductive system including epididymis, prostate and SCs. The most prominent characteristics of SC-based exosomes is considered mutual interaction of sertoli cells with spermatogonial stem cells and Leydig cells mainly through establishment of intercellular communication. Exosomes have gotten a lot of interest because of their role in pathobiological processes and as a cell free therapy which led to developing multiple exosome isolation methods based on different principles. Transmission of nucleic acids, proteins, and growth factors via SC-based exosomes and exosomal miRNAs are proved to have potential to be valuable biomarkers in male reproductive disease. Among testicular abnormalities, non-obstructive azoospermia and testicular cancer have been more contributed with SCs performance. The identification of key proteins and miRNAs involved in the signaling pathways related with spermatogenesis, can serve as diagnostic and regenerative targets in male infertility.

Circulatory microRNAs in helminthiases: Potent as diagnostics biomarker, its potential role and limitations

Infections caused by helminths are responsible for severe public health problems and economic burden on continental scale. Well-timed and precise diagnosis of helminth infections is critical for taking by appropriate approaches for pathogen control. Circulating miRNAs are stable diagnostic tool for different diseases found in a variety of body fluid. As diagnostic biomarkers in infectious diseases, miRNAs detection in body fluids of helminth infected hosts is growing promptly. Uncovering miRNAs is a relatively new tool, used for early-stage detection of helminth infection from experimental or non-invasive clinical samples. miRNAs can be detected in body fluids such as serum, saliva, urine, and tissues of helminth infected host, mainly blood offering important benefits for diagnosis accurately. In this review, we discuss different characteristics of helminth parasite-derived circulating and EV miRNAs, supporting its potential uses in for helminth diagnosis and treatment efficiency.

Diversity of Extracellular Vesicles in Human Follicular Fluid: Morphological Analysis and Quantification

The oocyte microenvironment constituted by the follicular fluid (FF) is a key for the optimal development of female gametes. Its composition reflects the physiological state of the ovarian follicle. The particularity of FF is to contain a huge diversity of extracellular vesicles specific to women, in the same way as seminal plasma in men. Here, we described and compared morphological aspects of broad subcategories of human FF-related Extracellular Vesicles (EVs). EVs participate in physiological and pathological processes and have potential applications in diagnostics or therapeutics. EVs isolated from FF are involved in different biological functions related to follicular growth, oocyte maturation, and embryo development. However, knowledge on the morphology of FF-derived EVs is limited, mainly due to their sub-micrometer size and to intrinsic limitations in methods applied for their characterization. The aim of this study was to provide a comprehensive morphological description of EVs from FF of healthy subjects and quantification. EVs separation was realized by centrifugation, with comparison of the EV yield obtained from differential centrifugation and one-step ultracentrifugation. Cryo-Transmission Electron Microscopy was used to reveal the morphology, size, and phenotype of EVs. Dynamic Light Scattering (DLS) and Nanoparticle Tracking Analysis (NTA) were used to quantify and analyze the size distribution for each centrifugation step. We performed a comprehensive inventory of human follicular fluid EVs. We show that human FF contains a huge diversity of EVs. This study brings novel insights on EVs from normal FF and provides a reference for further studies of EVs in ovarian diseases.

Uterine extracellular vesicles as multi-signal messengers during maternal recognition of pregnancy in the mare

In contrast to other domestic mammals, the embryo-derived signal(s) leading to maternal recognition of pregnancy (MRP) are still unknow in the mare. We hypothesize that these embryonic signals could be packed into uterine extracellular vesicles (uEVs), acting as multi-signal messengers between the conceptus and the maternal tract, and contributing to MRP. To unveil these signals, the RNA and protein cargos of uEVs isolated from uterine lavages collected from pregnant mares (P; day 10, 11, 12 and 13 after ovulation) and cyclic control mares (C; day 10 and 13 after ovulation) were analyzed. Our results showed a fine-tuned regulation of the uEV cargo (RNAs and proteins), by the day of pregnancy, the estrous cycle, and even the size of the embryo. A particular RNA pattern was identified with specific increase on P12 related to immune system and hormonal response. Besides, a set of proteins as well as RNAs was highly enriched in EVs on P12 and P13. Differential abundance of miRNAs was also identified in P13-derived uEVs. Their target genes were linked to down- or upregulated genes in the embryo and the endometrium, exposing their potential origin. Our study identified for first time specific molecules packed in uEVs, which were previously associated to MRP in the mare, and thus bringing added value to the current knowledge. Further integrative and functional analyses will help to confirm the role of these molecules in uEVs during MRP in the mare.

Variations of follicular fluid extracellular vesicles miRNAs content in relation to development stage and season in buffalo

In buffalo (Bubalus bubalis) reproductive seasonality, causing cycles of milk production, is one of the major factors affecting farming profitability. Follicular fluid (FF) contains extracellular vesicles (EVs) playing an important role in modulating oocyte developmental competence and carrying microRNAs (miRNAs) essential for in vitro fertilization outcomes. The aim of this work was to characterize the FF-EVs-miRNA cargo of antral (An) and preovulatory (pO) follicles collected in the breeding (BS) and non-breeding (NBS) seasons, to unravel the molecular causes of the reduced oocyte competence recorded in buffalo during the NBS. In total, 1335 miRNAs (538 known Bos taurus miRNAs, 324 homologous to known miRNAs from other species and 473 new candidate miRNAs) were found. We identified 413 differentially expressed miRNAs (DE-miRNAs) (FDR < 0.05) between An and pO groups. A subset of the most significant DE-miRNAs between An and pO groups targets genes which function is related to the lipid and steroid metabolism, response to glucocorticoid and oestradiol stimulus. Comparison between BS and NBS showed 14 and 12 DE-miRNAs in An-FF-EVs and pO-FF-EVs, which regulate IL6 release and cellular adhesion, respectively. In conclusion, these results demonstrated that the miRNA cargo of buffalo FF-EVs varies in relation to both follicular development and season.

Biomaterials and advanced technologies for the evaluation and treatment of ovarian aging

Ovarian aging is characterized by a progressive decline in ovarian function. With the increase in life expectancy worldwide, ovarian aging has gradually become a key health problem among women. Over the years, various strategies have been developed to preserve fertility in women, while there are currently no clinical treatments to delay ovarian aging. Recently, advances in biomaterials and technologies, such as three-dimensional (3D) printing and microfluidics for the encapsulation of follicles and nanoparticles as delivery systems for drugs, have shown potential to be translational strategies for ovarian aging. This review introduces the research progress on the mechanisms underlying ovarian aging, and summarizes the current state of biomaterials in the evaluation and treatment of ovarian aging, including safety, potential applications, future directions and difficulties in translation.

Follicular-fluid proteomics during equine follicle development

The complex composition of the follicular fluid (FF), the intimate proximity to the oocyte, and the continual changes in their composition have a major effect on folliculogenesis and oogenesis. To date, the profiling of FF proteomes during follicle selection, development, and ovulation has not been comprehensively investigated. Therefore, a shotgun proteomics approach and bioinformatics analyses were used to profile the proteomes of equine FF harvested in vivo from follicles at the following development stages: predeviation (18-20 mm), deviation (22-25 mm), postdeviation (26-29 mm), preovulatory (30-35 mm), and impending ovulation. A total of 294 proteins were detected in FF (FDR <1%), corresponding to 65 common proteins and 124, 142, 167, 132, and 142 proteins in the predeviation, deviation, postdeviation, preovulatory, and impending ovulation groups, respectively. The higher expression of properdin and several other proteins belonging to the complement system during the deviation time and ovulation suggested their contribution in the selection of the future dominant follicle and ovulation. Apolipoprotein A-1 and antithrombin-III appeared to be important throughout folliculogenesis. The "complement and coagulation cascades" was the major KEGG pathway across all stages of follicle development. The significant expression of several proteins belonging to the serine-type endopeptidase indicated their likely contribution to follicle and oocyte development. Our data provide an extensive description and functional analyses of the equine FF proteome during follicle selection, development, and ovulation. This information will help improve understanding of the ovarian function and ovulatory dysfunctions and might serve as a reference for future biomarker discovery for oocyte quality assessment.

The extent of the abundance of exosomal and non-exosomal extracellular miRNAs in the bovine follicular fluid

Follicular fluid (FF) plays an important role during follicular development and it contains several bioactive molecules including extracellular microRNAs (ECmiRNAs) that may mediate cell-cell communication during follicular development. Yet, the distribution patterns of ECmiRNAs in FF is not well characterized. This study aims to investigate the distribution of ECmiRNAs in two major fractions, namely exosomal and non-exosomal, of bovine follicular fluid (bFF). Exosomal and non-exosomal fractions from bFF were separated using Exoquick™ exosomes precipitation kit. miRNA expression was evaluated using the human miRCURY LNA™ Universal RT miRNA PCR array system. Transmission electron microscopy and immunoblotting revealed that the isolated vesicles were exosomes. The real-time PCR-based expression analysis revealed that 516 miRNAs were detected in the exosomal fraction of bFF, while 393 miRNAs were detected in the non-exosomal fraction. Among the detected miRNAs, a total of 370 miRNAs were detected in both fractions, while 145 miRNAs and 23 miRNAs were solely detected in exosomal and non-exosomal fractions, respectively. Exploratory pathway analysis showed that the genes targeted by exosomal and non-exosomal miRNAs to be involved in MAPK, Wnt, FoxO, TGF-beta, Oxytocin, ErbB, PI3K-Akt, Neurotrophin signalling pathways which are believed to be involved in follicular development, cell proliferation, and meiotic resumption. The results of our study demonstrated that besides the exosomal fraction, non-exosomal fractions can carry a significant amount of miRNAs in bFF where the exosomal fraction carries a significantly higher number of detectable miRNAs.

Let-7a mimic transfection reduces chemotherapy-induced damage in a mouse ovarian transplantation model

Pharmacological approaches offer a non-invasive and promising option for fertility preservation in young female cancer patients undergoing gonadotoxic therapy. The GnRH-agonists are the only clinically available drugs in this indication, but their use and mechanisms of protection are still controversial. Recently, we have investigated new targeted drugs based on microRNA (miRNA) replacement therapy, and have identified the let-7a miRNA as candidate for fertility preservation strategies. Here, the effect of let-7a replacement during chemotherapy exposure on follicular growth and oocyte maturation capacity was investigated using a mouse ovarian-kidney transplantation model. Newborn mouse ovaries were cultured under different conditions; control, chemotherapy exposure (4-hydroperoxycyclophosphamide, 4-HC), and co-treatment with 4-HC and let-7a mimic transfection (4-HC + let-7a). The ovaries were then transplanted under the kidney capsule of recipient mice and follicular growth, survival, and oocyte in vitro maturation were assessed after 3 weeks. The results showed that the follicular pool was highest in the control group but higher in the 4-HC + let-7a group than the 4-HC group. DNA-damage/apoptosis ratios were higher in all 4-HC-exposed groups compared to control but were reduced in the 4-HC + let-7a group. In addition, the post-transplantation oocyte in vitro maturation rate was higher in the 4-HC + let-7a group compared to the 4-HC group, suggesting better oocyte quality. These results provide new information regarding the beneficial effects of let-7a replacement against chemotherapy-induced ovarian damage and open new perspectives for future in vivo applications.

Small-extracellular vesicles and their microRNA cargo from porcine follicular fluids: the potential association with oocyte quality

Background

Ovarian follicular fluids (FFs) contain several kinds of regulatory factors that maintain a suitable microenvironment for oocyte development. Extracellular vesicles (EVs) are among the factors that play essential roles in regulating follicle and oocyte development through their cargo molecules that include microRNAs (miRNAs). This study aimed to investigate small-EV (s-EV) miRNAs in porcine FFs and their potential association with oocyte quality.

Methods

Individual aspirated oocytes were stained with lissamine green B stain (LB), a vital stain for oocyte quality, and each oocyte was classified as high-quality (unstained; HQ) or low-quality (stained; LQ). FFs corresponding to oocytes were pooled together into HQ and LQ groups. Small-EVs were isolated from FFs, characterized, and their miRNA cargo was identified using the Illumina NovaSeq sequencing platform. Additionally, s-EVs from the HQ and LQ groups were utilized to investigate their effect on oocyte development after co-incubation during in vitro maturation.

Results

A total of 19 miRNAs (including miR-125b, miR-193a-5p, and miR-320) were significantly upregulated, while 23 (including miR-9, miR-206, and miR-6516) were downregulated in the HQ compared to the LQ group. Apoptosis, p53 signaling, and cAMP signaling were among the top pathways targeted by the elevated miRNAs in the HQ group while oocyte meiosis, gap junction, and TGF-beta signaling were among the top pathways targeted by the elevated miRNAs in the LQ group. The supplementation of small-EVs during maturation does not affect the oocyte developmental rates. However, LQ s-EVs increase the proportion of oocytes with homogeneous mitochondrial distribution and decrease the proportion of heterogeneous distribution.

Conclusion

Our findings indicated that FF-EVs contain different miRNA cargos associated with oocyte quality and could affect the mitochondrial distribution patterns during oocyte maturation.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40104-022-00723-1.

The role of extracellular vesicles in animal reproduction and diseases

Extracellular vesicles (EVs) are nanosized membrane-enclosed compartments that serve as messengers in cell-to-cell communication, both in normal physiology and in pathological conditions. EVs can transfer functional proteins and genetic information to alter the phenotype and function of recipient cells, which undergo different changes that positively affect their structural and functional integrity. Biological fluids are enriched with several subpopulations of EVs, including exosomes, microvesicles (MVs), and apoptotic bodies carrying several cargoes, such as lipids, proteins, and nucleic acids. EVs associated with the reproductive system are actively involved in the regulation of different physiological events, including gamete maturation, fertilization, and embryo and fetal development. EVs can influence follicle development, oocyte maturation, embryo production, and endometrial-conceptus communication. EVs loaded with cargoes are used to diagnose various diseases, including pregnancy disorders; however, these are dependent on the type of cell of origin and pathological characteristics. EV-derived microRNAs (miRNAs) and proteins in the placenta regulate inflammatory responses and trophoblast invasion through intercellular delivery in the placental microenvironment. This review presents evidence regarding the types of extracellular vesicles, and general aspects of isolation, purification, and characterization of EVs, particularly from various types of embryos. Further, we discuss EVs as mediators and messengers in reproductive biology, the effects of EVs on placentation and pregnancy disorders, the role of EVs in animal reproduction, in the male reproductive system, and mother and embryo cross-communication. In addition, we emphasize the role of microRNAs in embryo implantation and the role of EVs in reproductive and therapeutic medicine. Finally, we discuss the future perspectives of EVs in reproductive biology.

Extracellular vesicles in mammalian reproduction: a review

Over the last decades, extracellular vesicles (EVs) have been found to be implicated in a complex universal mechanism of communication between different cell types. EVs are nanostructures of lipid nature that have an exosomal or ectosomal biogenesis, responsible for the intercellular transport of proteins, lipids, carbohydrates, nucleic acids, ions, among other molecules. The content of EVs can vary due to various factors such as hormonal stimuli, non-physiological conditions, metabolic state, etc. Once EVs reach their target cell, they can modulate processes such as gene expression, metabolism, response to external factors, and can even be associated with the delivery of molecules involved in epigenetic inheritance processes in germ cells. In mammalian reproduction, EVs have been shown to play an important role, either in vivo or in vitro, modulating a variety of processes in sperm, oocytes and embryos, and in their respective environments. Moreover, EVs represent a biodegradable, harmless and specific vehicle, which makes them attractive allies to consider when improving assisted reproductive technologies (ARTs). Therefore, the present review aims to describe the content of the main EVs involved in mammalian reproduction and how they can vary due to different factors, as well as to detail how EVs modulate, directly or indirectly, different molecular processes in gametes and embryos. In addition, we will highlight the mechanisms that remain to be elucidated. We will also propose new perspectives according to the characteristics of each particular EV to improve the different ARTs.

The Exploration of miRNAs From Porcine Fallopian Tube Stem Cells on Porcine Oocytes

Fallopian tube is essential to fertilization and embryonic development. Extracellular vesicles (EVs) from Fallopian tube containing biological regulatory factors, such as lipids, proteins and microRNAs (miRNAs) serve as the key role. At present, studies on oocytes from porcine oviduct and components from EVs remain limited. We aim to explore the effect of EVs secreted by porcine fallopian tube stem cells (PFTSCs) on oocyte. When the fifth-generation PFTSCs reached 80–90% of confluency, the pig in vitro maturation medium was utilized, and the conditioned medium collected for oocyte incubations. To realize the functions of EVs, several proteins were used to determine whether extracted EVs were cell-free. Field emission scanning electron microscope and nanoparticle tracking analyzer were used to observe the morphology. By next generation sequencing, 267 miRNAs were identified, and those with higher expression were selected to analyze the Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathway enrichment maps. The selected miR-152-3p, miR-148a-3p, miR-320a-3p, let-7f-5p, and miR-22-3p, were predicted to target Cepb1 gene affecting MAPK pathway. Of the five miRNAs, miR-320a-3p showed significant difference in maturation rate in vitro maturation. The blastocyst rate of pig embryos was also significantly enhanced by adding 50 nM miR-320a-3p. In vitro culture with miR-320a-3p, the blastocyst rate was significantly higher, but the cleavage rate and cell numbers were not. The CM of PFTSCs effectively improves porcine oocyte development. The miRNAs in EVs are sequenced and identified. miR-320a-3p not only helps the maturation, but also increases the blastocyst rates.

Mammalian cumulus-oocyte complex communication: a dialog through long and short distance messaging

Communications are crucial to ovarian follicle development and to ovulation, and while both folliculogenesis and oogenesis are distinct processes, they share highly interdependent signaling pathways. Signals from distant organs such as the brain must be processed and compartments within the follicle have to be synchronized. The hypothalamic–pituitary–gonadal (HPG) axis relies on long-distance signalling analogous to wireless communication by which data is disseminated in the environment and cells equipped with the appropriate receptors receive and interpret the messages. In contrast, direct cell-to-cell transfer of molecules is a very targeted, short distance messaging system. Numerous signalling pathways have been identified and proven to be essential for the production of a developmentally competent egg. The development of the cumulus-oocyte complex relies largely on short distance communications or direct transfer type via extensions of corona radiata cells through the zona pellucida. The type of information transmitted through these transzonal projections is still largely uncharacterized. This review provides an overview of current understanding of the mechanisms by which the gamete receives and transmits information within the follicle. Moreover, it highlights the fact that in addition to the well-known systemic long-distance based communications from the HPG axis, these mechanisms acting more locally should also be considered as important targets for controlling/optimizing oocyte quality.