Maternal metabolic health and fertility: we should not only care about but also for the oocyte!

Metabolic disorders due to obesity and unhealthy lifestyle directly alter the oocyte's microenvironment and impact oocyte quality. Oxidative stress and mitochondrial dysfunction play key roles in the pathogenesis. Acute effects on the fully grown oocytes are evident, but early follicular stages are also sensitive to metabolic stress leading to a long-term impact on follicular cells and oocytes. Improving the preconception health is therefore of capital importance but research in animal models has demonstrated that oocyte quality is not fully recovered. In the in vitro fertilisation clinic, maternal metabolic disorders are linked with disappointing assisted reproductive technology results. Embryos derived from metabolically compromised oocytes exhibit persistently high intracellular stress levels due to weak cellular homeostatic mechanisms. The assisted reproductive technology procedures themselves form an extra burden for these defective embryos. Minimising cellular stress during culture using mitochondrial-targeted therapy could rescue compromised embryos in a bovine model. However, translating such applications to human in vitro fertilisation clinics is not simple. It is crucial to consider the sensitive epigenetic programming during early development. Research in humans and relevant animal models should result in preconception care interventions and in vitro strategies not only aiming at improving fertility but also safeguarding offspring health.

Obese outbred mice only partially benefit from diet normalization or calorie restriction as preconception care interventions to improve metabolic health and oocyte quality

STUDY QUESTION

Can diet normalization or a calorie-restricted diet for 2 or 4 weeks be used as a preconception care intervention (PCCI) in Western-type diet-induced obese Swiss mice to restore metabolic health and oocyte quality?

SUMMARY ANSWER

Metabolic health and oocyte developmental competence was already significantly improved in the calorie-restricted group after 2 weeks, while obese mice that underwent diet normalization showed improved metabolic health after 2 weeks and improved oocyte quality after 4 weeks.

WHAT IS KNOWN ALREADY

Maternal obesity is linked with reduced metabolic health and oocyte quality; therefore, infertile obese women are advised to lose weight before conception to increase pregnancy chances. However, as there are no univocal guidelines and the specific impact on oocyte quality is not known, strategically designed studies are needed to provide fundamental insights in the importance of the type and duration of the dietary weight loss strategy for preconception metabolic health and oocyte quality.

STUDY DESIGN, SIZE, DURATION

Outbred female Swiss mice were fed a control (CTRL) or high-fat/high-sugar (HF/HS) diet. After 7 weeks, some of the HF mice were put on two different PCCIs, resulting in four treatment groups: (i) only control diet for up to 11 weeks (CTRL_CTRL), (ii) only HF diet for up to 11 weeks (HF_HF), (iii) switch at 7 weeks from an HF to an ad libitum control diet (HF_CTRL) and (iv) switch at 7 weeks from an HF to a 30% calorie-restricted control diet (HF_CR) for 2 or 4 weeks. Metabolic health and oocyte quality were assessed at 2 and 4 weeks after the start of the intervention (n = 8 mice/treatment/time point).

PARTICIPANTS/MATERIALS, SETTING, METHODS

Changes in body weight were recorded. To study the impact on metabolic health, serum insulin, glucose, triglycerides, total cholesterol and alanine aminotransferase concentrations were measured, and glucose tolerance and insulin sensitivity were analyzed at PCCI Weeks 2 and 4. The quality of in vivo matured oocytes was evaluated by assessing intracellular lipid droplet content, mitochondrial activity and localization of active mitochondria, mitochondrial ultrastructure, cumulus cell targeted gene expression and oocyte in vitro developmental competence.

MAIN RESULTS AND THE ROLE OF CHANCE

Significant negative effects of an HF/HS diet on metabolic health and oocyte quality were confirmed (P < 0.05). HF_CTRL mice already showed restored body weight, serum lipid profile and glucose tolerance, similar to the CTRL_CTRL group after only 2 weeks of PCCI (P < 0.05 compared with HF_HF) while insulin sensitivity was not improved. Oocyte lipid droplet volume was reduced at PCCI Week 2 (P < 0.05 compared with HF_HF), while mitochondrial localization and activity were still aberrant. At PCCI Week 4, oocytes from HF_CTRL mice displayed significantly fewer mitochondrial ultrastructural abnormalities and improved mitochondrial activity (P < 0.05), while lipid content was again elevated. The in vitro developmental capacity of the oocytes was improved but did not reach the levels of the CTRL_CTRL mice. HF_CR mice completely restored cholesterol concentrations and insulin sensitivity already after 2 weeks. Other metabolic health parameters were only restored after 4 weeks of intervention with clear signs of fasting hypoglycemia. Although all mitochondrial parameters in HF_CR oocytes stayed aberrant, oocyte developmental competence in vitro was completely restored already after 2 weeks of intervention.

LARGE SCALE DATA

N/A.

LIMITATIONS, REASONS FOR CAUTION

In this study, we applied a relevant HF/HS Western-type diet to induce obesity in an outbred mouse model. Nevertheless, physiological differences should be considered when translating these results to the human setting. However, the in-depth study and follow-up of the metabolic health changes together with the strategic implementation of specific PCCI intervals (2 and 4 weeks) related to the duration of the mouse folliculogenesis (3 weeks), should aid in the extrapolation of our findings to the human setting.

WIDER IMPLICATIONS OF THE FINDINGS

Our study results with a specific focus on oocyte quality provide important fundamental insights to be considered when developing preconception care guidelines for obese metabolically compromised women wishing to become pregnant.

STUDY FUNDING/COMPETING INTEREST(S)

This study was supported by the Flemish Research Fund (FWO-SB grant 1S25020N and FWO project G038619N). The authors declare there are no conflicts of interest.

O-155 Dietary caloric normalization or restriction as preconception care strategies: impact on oocyte developmental competence and quality in high fat/high sugar-induced obese outbred mice

Study question

Can diet normalization or caloric restriction (CR) for two weeks be used as a preconception care intervention in obese Swiss mice to restore oocyte development and quality

Summary answer

Diet normalization or CR as short-term preconception care interventions in obese mice only partially restored oocyte quality but did improve overall developmental competence.

What is known already

Maternal metabolic disorders like obesity and metabolic syndrome may result in decreased oocyte and embryo quality, and thus reproductive failure. Overweight and obese patients are advised to lose weight before conception to increase the chance of a healthy pregnancy. However, as human studies show no univocal guidelines, more fundamental research might provide additional answers. In order to avoid interference with increased maternal age, the question remains if oocyte quality can be restored after only a short preconception care intervention (PCCI).

Study design, size, duration

Outbred mice were fed a control (CTRL) or high-fat/high-sugar (HF) diet for seven weeks. Afterwards, HF-mice were put on different PCCIs for two weeks, resulting in four treatment groups: control diet (9w; CTRL_CTRL), HF diet (9w; HF_HF), switch from HF (7w) to an ad libitum control diet for 2w (HF_CTRL) or to a 30% CR diet for 2w (HF_CR). Oocyte developmental competence (n = 357) and quality (12-16 oocytes /treatment, scored blinded) were determined, using 6-8 mice/treatment.

Participants/materials, setting, methods

Body weight changes were recorded. In vivo matured oocytes were collected after superovulation and analysed for quality or in vitro fertilized and cultured. Oocyte quality was determined by staining for lipid content (Bodipy) and mitochondrial inner membrane potential and active mitochondria localization (JC-1). Oocyte developmental competence [cleavage (24h p.i.) and blastocyst rates (5 days p.i.)] was scored. Categorical and numerical data were analysed using binary logistic regression and ANOVA, respectively and corrected for multiple testing.

Main results and the role of chance

Compared to the CTRL group, HF diet increased body weight after 7 weeks by 24.19% (P &lt; 0.001). After the start of the PCCI, both HF_CTRL and HF_CR mice progressively lost weight and reached values similar to control mice after two weeks. HF_HF diet increased the intracellular lipid content in oocytes with 54.3% compared to the CTRL_CTRL group (P &lt; 0.05). This increased content was (partially) normalized in both preconception care intervention groups, even similar to the control levels in the HF_CTRL group. Both HF_HF and HF_CR oocytes showed a tendency to an increased ratio of active/total mitochondria when compared to the CTRL_CTRL group (P = 0.081, P = 0.083 respectively). In addition, active oocyte mitochondria in the HF_HF group were less pericortically distributed compared to controls. This was also the case in both preconception care intervention groups (P &lt; 0.05). After two weeks of PCCI, oocytes from HF_HF mice displayed lower cleavage rates than those from CTRL_CTRL mice (36.26% vs. 64.52%, P &lt; 0.05) but blastocyst rates (26.37% vs. 35.48%, P &gt; 0.1) were not different. HF_CR, but not HF_CTRL, oocytes showed higher cleavage rates (68.48%, P &lt; 0.001) compared with HF_HF oocytes. Moreover, both HF_CTRL (44.64%, P &lt; 0.05) and HF_CR (59.78%, P &lt; 0.001) oocytes showed improved blastocyst rates when compared to the HF_HF group (26.37%).

Limitations, reasons for caution

Although using a mouse model has several advantages, translating these results to the human setting is a limitation of this study. However, to improve this translatability, an outbred mouse model was used. Additional data will be collected to gain more information regarding the best preconception care intervention advice.

Wider implications of the findings

This research aims to provide fundamental insights in order to be able to formulate clear preconception guidelines to obese women planning for pregnancy. In addition, we aim to find the shortest possible intervention period to improve fertility.

Trial registration number

Not applicable

Altered embryotrophic capacities of the bovine oviduct under elevated free fatty acid conditions: an in vitro embryo--oviduct co-culture model

Maternal metabolic stress conditions are of growing importance in both human and dairy cattle settings as they can have significant repercussions on fertility. Upregulated lipolysis is a common trait associated with metabolic disorders and results in systemically elevated concentrations of non-esterified fatty acids (NEFAs). The effects of high NEFA concentrations on the follicular environment, oocyte and embryo development is well documented. However, knowledge on the effects of NEFAs within the oviduct, representing the initial embryonic growth environment, is currently lacking. Therefore, the experiments outlined here were designed to obtain fundamental insights into both the direct and indirect interactions between NEFAs, bovine oviductal cells and developing zygotes. Hence, zygotes were co-cultured with NEFA-pre-exposed bovine oviductal cells or subjected to simultaneous NEFA exposure during the co-culture period. The outcome parameters assessed were embryo development with cleavage (48h post insemination (pi)), morula (120-126h pi) and blastocyst (192h pi) rates, as well as morula intracellular lipid content and blastocyst quality using Bodipy and differential staining respectively. Our data suggest a direct embryotoxicity of NEFAs as well as impaired embryo development through a reduced oviductal ability to support and protect early embryo development.

Capacity of Trolox to improve the development and quality of metabolically compromised bovine oocytes and embryos invitro during different windows of development

Trials to improve oocyte developmental competence under metabolic stress by using antioxidants may start before or after oocyte maturation. In the present conceptual study, we aimed to identify the most efficient timing of antioxidant application in relation to a metabolic insult using a bovine invitro embryo production model. Pathophysiological concentrations of palmitic acid (PA) were used to induce metabolic stress during oocyte maturation or embryo development. Trolox (TR; antioxidant) treatment prior to, during or after the PA insult was tested to evaluate the protective, neutralising and rescuing capacity of TR respectively. Changes in embryo developmental competence, mitochondrial activity, reactive oxygen species (ROS) concentrations, blastocyst cell allocation and apoptosis and cell stress-related gene expression were monitored. The improvement in developmental capacity was most obvious when oocytes were preloaded with TR before the PA insult. This protective effect could be explained by the observed combination of increased mitochondrial activity with reduced ROS production. This resulted in blastocysts with normal cell counts and apoptosis, as well as increased nuclear factor erythroid 2-related factor 2 (NRF2) expression (a marker for redox regulatory processes) and normalised the expression of the mitochondrial transcription factor A (TFAM), a marker of mitochondrial biogenesis. These results indicate that 'pretreatment' of oocytes with antioxidants produces embryos that seem to be more resilient to a metabolic stress insult.

65 Improvement of bovine early embryo development in vitro by coculture with endometrial epithelial cells

We optimized a bovine endometrial epithelial cell (BEEC) line as a valuable research model for the study of very early embryo-maternal interactions in vitro. In this study, we aimed to (1) characterise the BEEC monolayers along the primary culture and first passages with respect to the expression of epithelial and mesenchymal cell markers and abundance of functional key transcripts; (2) to test whether direct or indirect contact with endometrial cells alter the quality of the embryos in vitro; and (3) to test the specificity of the effect. In Exp. 1, after isolation from slaughterhouse uteri at the early luteal phase, BEEC were cultured in DMEM/F12 phenol red-free medium supplemented with 10% fetal bovine serum (FBS) from primary culture until subculture 3. Fixed samples were immunostained for cytokeratin and vimentin. Transcript abundances for cellular lineage markers (KRT18 and VIM), oestrogen receptor (ESR1), interferon α/beta receptor 1 (IFNAR1), and prostaglandin G/H synthase 1 (PTGS1) and 2 (PTGS2) were evaluated by real-time quantitative PCR. Statistical analyses were carried out by ANOVA and Tukey test. Immunofluorescence data revealed that the BEEC line co-expresses cytokeratin together with a mesenchymal marker (Vimentin). This indicates that these epithelial cells underwent an epithelial-mesenchymal transition in vitro. Gene expression data showed a 6-fold increased (P&lt;0.001) abundance of VIM mRNA from the primary culture to the subculture 1, which remained constant until subculture 3; however, KRT18, ESR1, IFNAR1, PTGS1, and PTGS2 were similar between the passages, suggesting that the cells conserved their functional characteristics. In Exp. 2, groups of 15 morulas (Day 5.5) were cultured in SOF medium supplemented with 5% FBS in the absence (control) or in the presence (co-culture) of BEEC at passage 2, for 48h. Embryos were placed on direct or indirect contact with a BEEC monolayer using a 96-well insert containing 8μm pores. Developmental rates were compared by chi-square test and P-values were adjusted by Tukey’s test. The percentage of embryos that had developed from morula into blastocyst stage on Day 7.5 was significantly higher in the direct and indirect contact co-culture (65%; P&lt;0.05) groups compared with the control (53%) group. Moreover, 63% of the blastocysts were expanded, hatching, or hatched in the co-culture groups, whereas a rate of 46% was found in the control counterparts (P&lt;0.05). In Exp. 3, the same experimental conditions from Exp. 2 were used, but groups of 15 Day 5.5 morulas were cultured in control, or conditioned medium from BEEC (CondBEEC) or bovine fibroblasts (CondFib). Blastocyst development rate on Day 7.5 was higher in the CondBEEC group (71%; P&lt;0.001) compared with the control (54%) and CondFib (50%) groups. In conclusion, based on the markers studied, BEEC monolayers undergo epithelial-mesenchymal transition in vitro but preserve functional characteristics after few passages. The co-culture system improves bovine embryonic development from morula into blastocyst stage. This support is BEEC specific and does not rely on a direct cell-to-embryo contact.

47 Effect of a long-term, high-fat diet on metabolic health and oocyte quality of an outbred (Swiss) versus inbred (C57BL/6N) mouse strain

Maternal metabolic disorders like obesity and diabetes type II are known to affect reproductive physiology, ultimately leading to poor fertility. The oocyte and embryo are extremely vulnerable during the periconceptional period to metabolic stressors, leading to disappointing fertility results. Most mouse model research regarding obesity and Western type diets has been performed on the inbred C57BL/6 strain. However, inbred strains are often linked with decreased fertility. Relying only on inbred strains might also limit translation to human (outbred) physiology. To further explore this, we compared the inbred C57BL/6N to an outbred Swiss strain. Five-week-old Swiss (N=30) and C57BL/6N (B6) (N=29) mice were fed a control (CTRL) or a high-fat (HF) diet for 13 weeks. Diets differed in percentage of fat (10% v. 60%). Body weight gain, serum profile (nonesterified fatty acids, cholesterol, and triglycerides), and oocyte quality were studied. Mature oocytes were collected after hormonal stimulation (IP injection of 10IU of pregnant mare serum gonadotropin followed by 10IU of hCG 48h later). To study oocyte quality, Bodipy (lipid droplets), JC-1 (mitochondrial membrane potential), and Cell-Rox Deep Red stainings were performed, as well as transmission electron microscopy to examine mitochondrial structures. All data were analysed using the t-test. In comparison with the CTRL group, the HF diet increased body weight by 18.09 and 27.87% in Swiss and B6, respectively. The HF significantly increased blood cholesterol levels (103.5v. 143.1 mg/dL in Swiss mice, 141.8v. 185.4 mg/dL in B6 mice) in both strains, and tended to increase blood nonesterified fatty acids (P=0.053) and triglycerides (P=0.075) only in Swiss but not in B6 mice. Oocytes collected from the HF diet group contained a larger total volume of lipid droplets (P&lt;0.05) in both strains compared with controls. The mitochondrial membrane potential and Cell-Rox Deep Red were significantly increased (P&lt;0.05) in oocytes of Swiss mice, but not B6 mice, fed a HF diet. Transmission electron microscopy images from HF oocytes showed mitochondria with abnormal morphology, low electron density, and rose petal appearance, resulting in significantly increased mitochondrial abnormalities in Swiss mice on the HF diet (P&lt;0.05). In B6 mice, both CTRL and HF oocytes contained high proportions of abnormal mitochondria compared with the CTRL group of the Swiss mice, explaining the lack of HF diet effects in B6 oocyte ultrastructure. We conclude that a HF diet has a significant effect on both metabolic health and oocyte quality. However, the Swiss model seems more sensitive to a Western type diet insult, making it more suitable for research focusing on metabolic health and oocyte quality than the B6 strain. The HF diet-exposed Swiss mice showed differences (compared with CTRL) in their serum profile. Alterations in mitochondrial activity, structures, and oxidative stress were induced by HF diet in the Swiss mice and not the B6, although B6 oocytes also showed higher lipid droplet accumulation. Furthermore, even the B6 mice that were fed a normal control diet showed deviant oocyte quality, clearly shown by morphological signs of lower quality and mitochondrial abnormalities.

166 Mitochondrial stress responses in bovine cumulus cells and oocytes matured under lipotoxic conditions: a proteomic insight

Obesity and up-regulated lipolysis are commonly associated with increased free fatty acid (FFA) concentrations, predominantly palmitic acid (PA), in blood and ovarian follicular fluid, which have been strongly linked with reduced oocyte quality. Mitochondria are known to play a central role in regulating cellular stress responses to lipotoxicity, which is well described in somatic cells. Although mitochondrial functions in oocytes are crucial for developmental competence, their stress response capacity has not been clearly described. Networking with endoplasmic reticulum unfolded protein responses (UPR) and protein translation may be different in oocytes than in somatic cells. Understanding these mechanisms is important to develop treatments. The aim of this study was to compare PA-induced stress responses in oocytes to those in cumulus cells (CC). We exposed bovine cumulus-oocyte complexes (COC) to pathophysiological PA concentration (150 µM) or solvent during in vitro maturation (24h) as a model. Then, the CC were separated from the oocytes (from pools of 120 COC per treatment per replicate, 3 replicates), and their proteomic profiles were examined using shotgun proteomic analysis with tandem mass tags. Functional analysis of the differentially regulated proteins (DRP; P&lt;0.05, fold change &gt;10%, false discovery rate &lt;5%) was done using Ingenuity® Pathway Analysis (IPA®; Qiagen, Valencia, CA, USA). A total of 1843 and 1275 proteins were identified in CC and oocytes, respectively, of which 86 and 54 were differentially regulated by PA. In CC, 20/86 proteins were mitochondrial, 16 of which were down-regulated. Canonical pathway analysis in CC showed that pro-apoptotic UPR, mitochondrial dysfunction, and other related redox regulatory, metabolic, and apoptotic pathways were the most affected. In the enclosed oocytes, 12/54 proteins were mitochondrial, 8 of which were up-regulated. Functional analysis of the DRP in oocytes suggests that pro-survival mechanisms were predominant. Mitochondrion-specific H2O2-scavenging enzyme (peroxiredoxin-3), mitochondrial trifunctional protein (HADHB), heat shock protein A8 (HSPA8), as well as the NRF2-mediated oxidative stress response, among others, were key regulatory mechanisms induced by PA in the oocytes. However, an increase in the relative abundance of cytochrome C was evident, which may trigger apoptosis. This was accompanied by up-regulation of SLC24A5, which negatively regulates mitochondrial outer membrane permeabilization and may prevent such apoptotic trigger. These data show that the mitochondria in oocytes, despite being structurally immature, regulate adaptive signalling pathways in response to metabolic stress. Although the proteomic changes in oocytes were predominantly anti-apoptotic, certain defective pro-apoptotic changes were identified. These data provide a unique insight into the mitochondrial adaptive signalling pathways in metabolically compromised oocytes, and indicate specific mitochondrial target pathways through which the developmental capacity of metabolically compromised oocytes can be improved or protected.

Differential effects of high and low glucose concentrations during lipolysis-like conditions on bovine in vitro oocyte quality, metabolism and subsequent embryo development

Lipolytic metabolic conditions are traditionally associated with elevated non-esterified fatty acid (NEFA) concentrations, but may also be accompanied by hyperglycaemia in obesity or by hypoglycaemia during a negative energy balance status. Elevated NEFA concentrations disrupt oocyte and embryo development and quality, but little is known about whether the effects of lipolytic conditions on oocyte developmental competence are modulated by glucose availability. To answer this, bovine cumulus-oocyte complexes (COCs) were matured under different conditions: physiological NEFA (72µM) and normal glucose (5.5mM), pathophysiologically high NEFA (420µM) and normal glucose, high NEFA and high glucose (9.9mM), high NEFA and low glucose (2.8mM). Developmental potential, cumulus expansion and metabolism of COCs exposed to high NEFA and low glucose were affected to a greater extent compared with COCs matured under high NEFA and high glucose conditions. High NEFA and high glucose conditions caused a moderate increase in oocyte reactive oxygen species compared with their high NEFA and low glucose or control counterparts. Blastocyst metabolism and the transcriptome of metabolic and oxidative stress-related genes were not affected. However, both lipolytic conditions associated with hyper- or hypoglycaemia led to surviving embryos of reduced quality with regards to apoptosis and blastomere allocation.

The effect of elevated non-esterified fatty acid concentrations on bovine spermatozoa and on oocyte in vitro fertilisation

Elevated non-esterified fatty acid (NEFA) concentrations, present in follicular and oviductal fluid, have been postulated as a causative link between metabolic disorders and subfertility. High NEFA conditions can directly disrupt oocyte maturation and developmental capacity after fertilisation. However, their influence on sperm function and the fertilisation process is not known. This study investigated the fertilisation process under high NEFA conditions. To differentiate between effects on both spermatozoa and oocytes or on spermatozoa only, different experiments were conducted. In the first experiment both gametes were simultaneously incubated during IVF under different conditions: (1) NEFA-free, solvent-free control conditions, (2) solvent control, (3) physiological concentrations of oleic (OA), palmitic (PA) and stearic (SA) acids or (4) pathophysiological concentrations of OA, PA and SA. In the second experiment spermatozoa were incubated (4 h) under the same treatment conditions prior to routine IVF. Gamete co-incubation resulted in reduced fertilisation and cleavage rates and increased prevalence of polyspermy. In the second experiment embryo developmental capacity and quality were not affected, although sperm motility and plasma membrane integrity were decreased. In conclusion, lipolytic conditions affected the fertilisation process mainly through an effect on the oocyte. Spermatozoa were still able to fertilise even though these conditions reduced sperm function.

Maternal metabolic stress may affect oviduct gatekeeper function

We hypothesized that elevated non-esterified fatty acids (NEFA) modify in vitro bovine oviduct epithelial cell (BOEC) metabolism and barrier function. Hereto, BOECs were studied in a polarized system with 24-h treatments at Day 9: (1) control (0 µM NEFA + 0% EtOH), (2) solvent control (0 µM NEFA + 0.45% EtOH), (3) basal NEFA (720 µM NEFA + 0.45% EtOH in the basal compartment) and (4) apical NEFA (720 µM NEFA + 0.45% EtOH in the apical compartment). FITC-albumin was used for monolayer permeability assessment and related to transepithelial electric resistance (TER). Fatty acid (FA), glucose, lactate and pyruvate concentrations were measured in spent medium. Intracellular lipid droplets (LD) and FA uptake were studied using Bodipy 493/503 and immunolabelling of FA transporters (FAT/CD36, FABP3 and CAV1). BOEC-mRNA was retrieved for qRT-PCR. Results revealed that apical NEFA reduced relative TER increase (46.85%) during treatment and increased FITC-albumin flux (27.59%) compared to other treatments. In basal NEFA, FAs were transferred to the apical compartment as free FAs: mostly palmitic and oleic acid increased respectively 56.0 and 33.5% of initial FA concentrations. Apical NEFA allowed no FA transfer, but induced LD accumulation and upregulated FA transporter expression (↑CD36, ↑FABP3 and ↑CAV1). Gene expression in apical NEFA indicated increased anti-apoptotic (↑BCL2) and anti-oxidative (↑SOD1) capacity, upregulated lipid metabolism (↑CPT1, ↑ACSL1 and ↓ACACA) and FA uptake (↑CAV1). All treatments had similar carbohydrate metabolism and oviduct function-specific gene expression (OVGP1, ESR1 and FOXJ1). Overall, elevated NEFAs affected BOEC metabolism and barrier function differently depending on NEFA exposure side. Data substantiate the concept of the oviduct as a gatekeeper that may actively alter early embryonic developmental conditions.

Localisation and endocrine control of hyaluronan synthase (HAS) 2, HAS3 and CD44 expression in sheep granulosa cells

The aim of the present study was to investigate the hormonal regulation of hyaluronan (HA) components in sheep granulosa cells. HA components are present in the reproductive tract and have a range of physical and signalling properties related to reproductive function in several species. First, abattoir-derived ovaries of sheep were used to determine the localisation of HA synthase (HAS) 1–3 and CD44 proteins in antral follicles. Staining for HAS1–3 and CD44 proteins was most intense in the granulosa layer. Accordingly, the expression of HAS2, HAS3 and CD44 mRNA was measured in cultured granulosa cells exposed to 0–50 ng mL–1 of 17β-oestradiol and different combinations of oestradiol, gonadotropins, insulin-like growth factor (IGF)-1 and insulin for 48–96 h (1 ng mL–1 FSH, 10 ng mL–1 insulin, 10 ng mL–1 IGF-1, 40 ng mL–1 E2 and 25 ng mL–1 LH.). mRNA expression was quantified by real-time polymerase chain reaction using a fold induction method. The results revealed that the hormones tested generally stimulated mRNA expression of the genes of interest in cultured granulosa cells. Specifically, oestradiol, when combined with IGF-1, insulin and FSH, stimulated HAS2 mRNA expression. Oestradiol and LH had synergistic effects in increasing HAS3 mRNA expression. In conclusion, we suggest that the hormones studied differentially regulate HAS2, HAS3 and CD44 in ovine granulosa cells in vitro. Further work is needed to address the signalling pathways involved.