[Follicular fluid in mammals]

Small extracellular vesicles in follicular fluids for predicting reproductive outcomes in assisted reproductive technology

BACKGROUND

Assisted reproductive technology accounts for an increasing proportion of infertility treatments, and assessments to predict clinical pregnancy outcomes are desired. Extracellular vesicles exist in follicular fluid, and small non coding RNAs in extracellular vesicles underline the possibility of reflecting pregnancy potential.

METHODS

Follicular fluid samples are collected from 20 ovarian follicles of 15 infertile patients undergoing assisted reproductive technology. Extracellular vesicles are isolated by serial centrifugation and small RNA sequencing is performed to investigate the profiles of microRNAs and P-element-induced wimpy testis-interacting RNAs.

RESULTS

Small extracellular vesicles with a size range of approximately 100 nm are successfully isolated, and the small non coding RNA profiles of pregnant samples (n = 8) are different from those of non-pregnant samples (n = 12). Fourteen dysregulated small non coding RNAs are selected to identify the independent candidates [mean read count >100, area under the curve >0.8]. Among them, we find that a specific combination of small non coding RNAs (miR-16-2-3p, miR-378a-3p, and miR-483-5p) can predict the pregnant samples more precisely using a receiver operating characteristics curves analysis (area under the curve: 0.96). Furthermore, even in the same patients, the three microRNAs are differentially expressed between pregnant and non-pregnant samples.

CONCLUSIONS

Our results demonstrate that small non coding RNAs derived from small extracellular vesicles in follicular fluid can be potential non-invasive biomarkers for predicting pregnancy, leading to their probable application in assisted reproductive technology. Further large-scale studies are required to validate the clinical usefulness of these small non coding RNAs.

Does the addition of follicular fluid in the in vitro maturation medium increase the oocyte maturation and embryo production in alpacas?

In alpacas (Vicugna pacos), the high cost of in vitro embryo production is also a consequence of the use of several substances in the culture medium. In addition, embryo production rates in this species are still considered low. Thus, in attempt to reduce the cost and to improve the in vitro embryo production rates, this study evaluates the effect of adding follicular fluid (FF) in the in vitro maturation medium on oocyte maturation and subsequent embryo production. After ovary collection at the local slaughterhouse, the oocytes were recovered, selected, and allocated in experimental groups: standard maturation medium (G1) and simplified medium added by 10% FF (G2). The FF was acquired from follicles between 7- and 12-mm diameter. The cumulus cell expansion and the embryo production rates were analyzed by chi-square with p < 0.05. No differences (p > 0.05) were observed in maturation rate between G1 (66.36%) and G2 (63.12%) groups. Likewise, no significant difference (p > 0.05) was verified between G1 and G2 for morula (40.85 vs 38.45%), blastocyst (7.01 vs 6.93%), and total number of embryos (47.87 vs 45.38%). In conclusion, it was possible to simplify the medium used for in vitro maturation of alpaca oocytes resulting in embryo production rates similar to the standard medium.

Implications of High-Density Cholesterol Metabolism for Oocyte Biology and Female Fertility

Cholesterol is an essential component of animal cells. Different regulatory mechanisms converge to maintain adequate levels of this lipid because both its deficiency and excess are unfavorable. Low cell cholesterol content promotes its synthesis and uptake from circulating lipoproteins. In contrast, its excess induces the efflux to high-density lipoproteins (HDL) and their transport to the liver for excretion, a process known as reverse cholesterol transport. Different studies suggest that an abnormal HDL metabolism hinders female fertility. HDL are the only lipoproteins detected in substantial amounts in follicular fluid (FF), and their size and composition correlate with embryo quality. Oocytes obtain cholesterol from cumulus cells via gap junctions because they cannot synthesize cholesterol de novo and lack HDL receptors. Recent evidence has supported the possibility that FF HDL play a major role in taking up excess unesterified cholesterol (UC) from the oocyte. Indeed, genetically modified mouse models with disruptions in reverse cholesterol transport, some of which show excessive circulating UC levels, exhibit female infertility. Cholesterol accumulation can affect the egg´s viability, as reported in other cell types, and activate the plasma membrane structure and activity of membrane proteins. Indeed, in mice deficient for the HDL receptor Scavenger Class B Type I (SR-B1), excess circulating HDL cholesterol and UC accumulation in oocytes impairs meiosis arrest and hinders the developmental capacity of the egg. In other cells, the addition of cholesterol activates calcium channels and dysregulates cell death/survival signaling pathways, suggesting that these mechanisms may link altered HDL cholesterol metabolism and infertility. Although cholesterol, and lipids in general, are usually not evaluated in infertile patients, one study reported high circulating UC levels in women showing longer time to pregnancy as an outcome of fertility. Based on the evidence described above, we propose the existence of a well-regulated and largely unexplored system of cholesterol homeostasis controlling traffic between FF HDL and oocytes, with significant implications for female fertility.

Spatiotemporal expression of aquaporin 9 is critical for the antral growth of mouse ovarian follicles†

Although a few aquaporins (AQPs) expressed in granulosa cells have been postulated to mediate fluid passage into the antrum, the specific expression of AQPs in different follicle cell types and stages and their roles have not been evaluated extensively. The spatiotemporal expression of aquaporin (Aqp) 7, 8, and 9 and the functional roles of Aqp9 in antral growth and ovulation were examined using a superovulation model and 3-dimensional follicle culture. Aqp9 was expressed at a high level in the rapid growth phase (24-48 h post equine chorionic gonadotropin (eCG) for superovulation induction) compared to Aqp7 (after human chorionic gonadotropin (hCG)) and Aqp8 (8-24 h post eCG and 24 h post hCG). A dramatic increase in the expression and localization of Aqp9 mRNA in theca cells was observed, as evaluated using quantitative reverse transcription-polymerase (RT-PCR) coupled with laser capture microdissection and immunohistochemistry. AQP9 was located primarily on the theca cells of the tertiary and preovulatory follicles but not on the ovulated follicles. In phloretin-treated mice, the diameter of the preovulatory follicles and the number of ovulated oocytes decreased. Consistent with these findings, knocking down Aqp9 expression with an Aqp9 siRNA inhibited follicle growth (0.28:1 = siRNA:control) and decreased the number of ovulated follicles (0.36:1 = siRNA:control) during in vitro growth and ovulation induction. Based on these results, the expression of AQPs is under the control of the physiological status, and AQP9 expression in theca during folliculogenesis is required for antral growth and ovulation in a tissue-specific and stage-dependent manner.

Correlation between Pre-Ovulatory Follicle Diameter and Follicular Fluid Metabolome Profiles in Lactating Beef Cows

Induced ovulation of small pre-ovulatory follicles reduced pregnancy rates, embryo survival, day seven embryo quality, and successful embryo cleavage in beef cows undergoing fixed-time artificial insemination. RNA-sequencing of oocytes and associated cumulus cells collected from pre-ovulatory follicles 23 h after gonadotropin-releasing hormone (GnRH) administration to induce the pre-ovulatory gonadotropin surge suggested reduced capacity for glucose metabolism in cumulus cells of follicles ≤11.7 mm. We hypothesized that the follicular fluid metabolome influences metabolic capacity of the cumulus-oocyte complex and contributes to reduced embryo cleavage and quality grade observed following induced ovulation of small follicles. Therefore, we performed a study to determine the correlation between pre-ovulatory follicle diameter and follicular fluid metabolome profiles in lactating beef cows (Angus, n = 130). We synchronized the development of a pre-ovulatory follicle and collected the follicular contents approximately 20 h after GnRH administration. We then performed ultra-high performance liquid chromatography-high resolution mass spectrometry (UHPLC-HRMS) metabolomic studies on 43 follicular fluid samples and identified 38 metabolites within pre-ovulatory follicles of increasing size. We detected 18 metabolites with a significant, positive correlation to follicle diameter. Individual and pathway enrichment analysis of significantly correlated metabolites suggest that altered glucose and amino acid metabolism likely contribute to reduced developmental competence of oocytes when small pre-ovulatory follicles undergo induced ovulation.

Assisted Reproductive Technology in Neotropical Deer: A Model Approach to Preserving Genetic Diversity

Simple Summary

Deer species in the Neotropical region have undergone a decline of their populations. Although conservation of their natural habitat is considered the best way to assist the species, the speed of occupation of these areas and the anthropic actions are so fast that the efforts are, at times, insufficient. As free-living populations decrease, there is a descent in the genetic diversity and an increase in crossbreeding between related individuals (inbreeding). Genetic diversity is essential for survival, since it enables natural selection to occur, providing adaptation and maintenance of the species. To protect the genetic diversity, it is possible to use reproductive techniques and conserve different types of cells, which can be used in the future to reestablish any alleles that have been lost by the populations.

Abstract

One of the most significant challenges in deer is the ability to maintain genetic diversity, avoiding inbreeding and sustaining population health and reproduction. Although our general knowledge of reproductive physiology is improving, it appears that the application of assisted reproductive technology (ART) will more efficiently advance wildlife conservation efforts and preserve genetic diversity. The purpose of this review is to present the most important results obtained with the use of ART in Neotropical deer. Thus, the state-of-the-art for estrus synchronization, semen technology, artificial insemination, and in vivo embryo production will be presented. In vitro embryo production (IVP) is also a biotechnology that is taking initial steps in deer. In this aspect, the approach with the proteomics of ovarian follicular fluid is being used as a tool for a better understanding of oocyte maturation. Finally, cell banks and the use of interspecific somatic cell nuclear transfer (iSCNT) as well as the use of stem cells for gametes differentiation are promising techniques.

Wharton's jelly derived mesenchymal stem cells differentiate into oocyte like cells in vitro by follicular fluid and cumulus cells conditioned medium

Wharton's jelly derived-mesenchymal stem cells (WJ-MSCs) have a same developmental origin with primordial germ cells. WJ-MSCs perhaps differentiate into oocyte and germ like-cells (OLCs/GLCs) in the presence of appropriate inducers. Human follicular fluid (FF) and cumulus cells conditioned medium (CCM) are naturally rich sources for oocyte development. The aim of this study was to evaluate WJ-MSCs potential for differentiating into OLCs and GLCs exposed to FF and CCM. WJ-MSCs were cultured in two different induction media (10% FF, 10% CCM) for 21 days. Morphological changes and expression of developmental genes were evaluated on days 0, 7, 14 and 21 of culture. Also, on 21^st day of culture, the expression of oocyte and germ cell proteins investigated using immunofluorescence staining. Appearance of round shaped cells from 7^th day onwards indicated that WJ-MSCs can differentiate into OLCs when exposed to FF and CCM. The size of produced OLCs and expression of oocyte specific genes and proteins were increased more positively in FF group rather than CCM group. Although, WJ-MSCs could differentiate into OLCs by FF and CCM, however, the induction potential of FF for producing OLCs was better than CCM.

Protein profile of the ovarian follicular fluid of brown brocket deer (Mazama gouazoubira; Fisher, 1814)

The aim of this study was to characterize the protein profile of ovarian follicular fluid (FF) of brown brocket deer (Mazama gouazoubira). Five adult females received an ovarian stimulation treatment and the FF was collected by laparoscopy from small/medium (≤3.5 mm) and large (>3.5 mm) follicles. Concentrations of soluble proteins in FF samples were measured and proteins were analyzed by 1-D SDS-PAGE followed by tryptic digestion and tandem mass spectrometry. Data from protein list defined after a Mascot database search were analyzed using the STRAP software tool. For the protein concentration, no significant difference (P > 0.05) was observed between small/medium and large follicles: 49.2 ± 22.8 and 56.7 ± 27.4 μg/μl, respectively. Mass spectrometry analysis identified 13 major proteins, but with no significant difference (P > 0.05) between follicle size class. This study provides insight into elucidating folliculogenesis in brown brocket deer.

Metabolic Profile Comparison between Follicular Fluid and Serum in Normal Cows and Those Affected by Ovarian Cysts

The aim of this study was to carry out the metabolic profile comparison between follicular fluid and serum in normal cows and those affected by ovarian cysts (OC). After slaughtering, blood samples and follicular fluids from normal and cystic animals were collected and assayed using commercial kits to determine the concentrations of metabolites (glucose, total protein, total cholesterol, cortisol, triglycerides, urea, creatinine and insulin) and the liver enzymes activity. Data showed that OC were characterized by low levels of glucose, total protein, cholesterol and cortisol in cystic fluid, while urea concentrations were high compared to normal follicular fluid (P<0.001). On the other hand, serum assays of cystic animals revealed very low values of insulin and urea, whereas cortisol levels were relatively high in comparison with the serum of normal cows (P<0.001). Significant correlations between the serum and follicular fluid concentrations of normal cows were found for glucose (r=0.49), total cholesterol (r=0.31), cortisol (r=0.38) and total protein (r=0.63). The highest correlation was found for urea (r=0.86). On contrary, weak correlations were observed between metabolites concentrations in cystic fluid and in serum for normal and cystic cows. In conclusion, OC grow and persist in a metabolic environment, which differs from follicular fluid to blood. These changes may act together and/or separately to ensure the continuous development of OC. To understand a part of the mechanism, the authors propose a deep study about blood-follicle-barrier.

Seasonal variation in equine follicular fluid proteome

BACKGROUND

Proteomic studies of follicular fluid (FF) exist for several species, including the horse; however, the seasonal influence on FF proteome has not been explored in livestock. The application of high-throughput proteomics of FF in horse has the potential to identify seasonal variations of proteins involved in follicle and oocyte growth.

METHODS

This study (i) profiles the proteomes of equine FF collected from dominant growing follicles during the spring anovulatory season (SAN), and spring (SOV), summer (SUM), and fall (FOV) ovulatory seasons; and (ii) identifies season-dependent regulatory networks and associated key proteins.

RESULTS

Regardless of season, a total of 90 proteins were identified in FF, corresponding to 63, 72, 69, and 78 proteins detected in the SAN, SOV, SUM, and FOV seasons, respectively. Fifty-two proteins were common to all seasons, a total of 13 were unique to either season, and 25 were shared between two seasons or more. Protein-to-protein interaction (PPI) analysis indicated the likely critical roles of plasminogen in the SAN season, the prothrombin/plasminogen combination in SUM, and plasminogen/complement C3 in both SOV and FOV seasons. The apolipoprotein A1 appeared crucial in all seasons. The present findings show that FF proteome of SUM differs from other seasons, with FF having high fluidity (low viscosity).

CONCLUSIONS

The balance between the FF contents in prothrombin, plasminogen, and coagulation factor XII proteins favoring FF fluidity may be crucial at the peak of the ovulatory season (SUM) and may explain the reported lower incidence of hemorrhagic anovulatory follicles during the SUM season.

NMR metabolic profiling of follicular fluid for investigating the different causes of female infertility: a pilot study

INTRODUCTION

Several metabolomics studies have correlated follicular fluid (FF) metabolite composition with oocyte competence to fertilization, embryo development and pregnancy but there is a scarcity of research examining the metabolic effects of various gynaecological diseases.

OBJECTIVES

In this study we aimed to analyze and correlate the metabolic profile of FF from women who were following in vitro fertilization (IVF) treatments with their different infertility pathologies.

METHODS

We selected 53 women undergoing IVF who were affected by: tubal diseases, unexplained infertility, endometriosis, polycystic ovary syndrome (PCOS). FF of the study participants was collected at the time of oocytes retrieval. Metabolomic analysis of FF was performed by nuclear magnetic resonance (NMR) spectroscopy.

RESULTS

FF presents some significant differences in various infertility pathologies. Although it was not possible to discriminate between FF of control participants and women with tubal diseases and unexplained infertility, comparison of FF metabolic profile from control women with patients with endometriosis and PCOS revealed significant differences in some metabolites that can be correlated to the causes of infertility.

CONCLUSION

NMR-based metabolic profiling may be successfully applied to find diagnostic biomarkers for PCOS and endometriosis and it might be also used to predict oocyte developmental potential and subsequent outcome.

The role of tight junction proteins in ovarian follicular development and ovarian cancer

Tight junctions (TJ) are protein structures that control the transport of water, ions and macromolecules across cell layers. Functions of the transmembrane TJ protein, occluding (OCLN) and the cytoplasmic TJ proteins, tight junction protein 1 (TJP1; also known as zona occludens protein-1), cingulin (CGN) and claudins (CLDN) are reviewed, and current evidence of their role in the ovarian function is reviewed. Abundance of OCLN, CLDNs and TJP1 mRNA changed during follicular growth. In vitro treatment with various growth factors known to affect ovarian folliculogenesis indicated that CGN, OCLN and TJP1 are hormonally regulated. The summarized studies indicate that expression of TJ proteins (i.e., OCLN, CLDN, TJP1 and CGN) changes with follicle size in a variety of vertebrate species but whether these changes in TJ proteins are increased or decreased depends on species and cell type. Evidence indicates that autocrine, paracrine and endocrine regulators, such as fibroblast growth factor-9, epidermal growth factor, androgens, tumor necrosis factor-α and glucocorticoids may modulate these TJ proteins. Additional evidence presented indicates that TJ proteins may be involved in ovarian cancer development in addition to normal follicular and luteal development. A model is proposed suggesting that hormonal downregulation of TJ proteins during ovarian follicular development could reduce barrier function (i.e., selective permeability of molecules between theca and granulosa cells) and allow for an increase in the volume of follicular fluid as well as allow additional serum factors into the follicle that may directly impact granulosa cell functions.

Metabolic profile of serum and follicular fluid from postpartum dairy cows during summer and winter

This study was designed to monitor the biochemical profiles of serum and follicular fluid (FF) of postpartum dairy cows during the summer (n=30) and winter (n=30). Blood and FF (follicles ≥ 9 mm) were obtained from Girolando cows at 30, 45, 60, 75 and 90 days postpartum. The samples were collected and analysed to determine glucose, total cholesterol (TC), triglyceride (TG), urea, sodium (Na), potassium (K) and calcium (Ca) levels. Throughout the study, the following clinical variables were measured: rectal temperature (RT), respiratory rate (RR) and body condition score (BCS). In addition, the temperature humidity index (THI) was calculated for each season. During the summer season, THI was higher, BCS decreased, there was an increase in RT, and glucose, urea, Na and K serum levels were decreased (P<0.05). The levels of TC, TG, urea, K and Ca in follicular fluid increased (P<0.05). Positive correlations (P<0.05) were observed between the serum and FF levels for glucose (r=0.29), TC (r=0.24) and Ca (r=0.30). Therefore, the biochemical profile of serum and FF of dairy cows under summer heat-stress conditions demonstrates marked changes that may impair fertility during lactation.

MALDI Mass Spectrometry Imaging of Lipids and Gene Expression Reveals Differences in Fatty Acid Metabolism between Follicular Compartments in Porcine Ovaries

In mammals, oocytes develop inside the ovarian follicles; this process is strongly supported by the surrounding follicular environment consisting of cumulus, granulosa and theca cells, and follicular fluid. In the antral follicle, the final stages of oogenesis require large amounts of energy that is produced by follicular cells from substrates including glucose, amino acids and fatty acids (FAs). Since lipid metabolism plays an important role in acquiring oocyte developmental competence, the aim of this study was to investigate site-specificity of lipid metabolism in ovaries by comparing lipid profiles and expression of FA metabolism-related genes in different ovarian compartments. Using MALDI Mass Spectrometry Imaging, images of porcine ovary sections were reconstructed from lipid ion signals for the first time. Cluster analysis of ion spectra revealed differences in spatial distribution of lipid species among ovarian compartments, notably between the follicles and interstitial tissue. Inside the follicles analysis differentiated follicular fluid, granulosa, theca and the oocyte-cumulus complex. Moreover, by transcript quantification using real time PCR, we showed that expression of five key genes in FA metabolism significantly varied between somatic follicular cells (theca, granulosa and cumulus) and the oocyte. In conclusion, lipid metabolism differs between ovarian and follicular compartments.

Effect of porcine follicular fluid proteins and peptides on oocyte maturation and their subsequent effect on in vitro fertilization

The follicular fluid (FF) is a microenvironment that contains molecules involved in oocyte maturation, ovulation, and fertilization. Characterizing the proteins and peptides present in the FF could be useful for determining which proteins and peptides to use as a supplement for culture media. Biologically active peptides produced during the maturation or degradation of functional proteins are called cryptides. The aim of this study was to identify the proteins and cryptides in porcine FF that could stimulate porcine oocyte in vitro maturation (IVM) and in vitro fertilization (IVF) when added to culture maturation medium. Five FF protein fractions (F1-F5) were obtained by ionic exchange chromatography, resolved by SDS-PAGE, and identified by tandem mass spectrometry. These fractions had effects on IVM and/or IVF. The F1 fraction, which was composed of immunoglobulin fragments, cytokeratin, transferrin, and plasminogen precursor increased IVM and IVF. The F2, F3, and F4 fractions reduced the percentage of oocytes in first metaphase. Additionally, the F3 fraction, which was composed of immunoglobulins and transthyretin, interfered with germinal vesicle breakdown. The F5 fraction, which was mainly composed of serum albumin and keratin, favored germinal vesicle breakdown and promoted IVM. Most of the 31 proteins which were associated with the immune response and inflammatory processes could be related to oocyte maturation and fertilization. Some of the identified proteins were present in more than one fraction; this could be explained by a change in their isoelectric points, because of the loss of part of the amino acid sequence or a change in the glycosylation status of the protein. Improved oocyte IVM and IVF will increase embryo production, which in turn will contribute to the efficiency of assisted reproduction in various mammalian species.

Cotinine concentrations in follicular fluid as a measure of secondhand tobacco smoke exposure in women undergoing in vitro fertilization: inter-matrix comparisons with urine and temporal variability

We examined the relationship between cotinine measures in follicular fluid (FF) and urine to inform our exposure assessment strategy for an ongoing epidemiological study of secondhand tobacco smoke (STS) exposure and early pregnancy loss. Among subjects undergoing in vitro fertilization (IVF), we compared cotinine levels in paired urine and FF samples from the same women and examined FF cotinine levels over time. We found a weak rank-order relationship (Spearman r<0.2) and poor agreement for classifying nonsmoking individuals as exposed to STS (sensitivity=0.29-0.71; specificity=0.35-0.72) between cotinine concentrations in FF and urine. We observed fair reliability (ICC=0.42-0.52) in FF cotinine concentrations from women undergoing multiple IVF cycles. If available, FF cotinine concentrations may be desired as a biomarker of low-level tobacco smoke exposure over urinary cotinine in studies of early reproduction. Collection of multiple FF samples for cotinine analysis may be needed to accurately represent long-term STS exposure.