Influence of bovine serum albumin and fetal bovine serum supplementation during in vitro maturation on lipid and mitochondrial behaviour in oocytes and lipid accumulation in bovine embryos

Procyanidin B2 improves developmental capacity of bovine oocytes via promoting PPARγ/UCP1-mediated uncoupling lipid catabolism during in vitro maturation

Metabolic balance is essential for oocyte maturation and acquisition of developmental capacity. Suboptimal conditions of in vitro cultures would lead to lipid accumulation and finally result in disrupted oocyte metabolism. However, the effect and mechanism underlying lipid catabolism in oocyte development remain elusive currently. In the present study, we observed enhanced developmental capacity in Procyanidin B2 (PCB2) treated oocytes during in vitro maturation. Meanwhile, reduced oxidative stress and declined apoptosis were found in oocytes after PCB2 treatment. Further studies confirmed that oocytes treated with PCB2 preferred to lipids catabolism, leading to a notable decrease in lipid accumulation. Subsequent analyses revealed that mitochondrial uncoupling was involved in lipid catabolism, and suppression of uncoupling protein 1 (UCP1) would abrogate the elevated lipid consumption mediated by PCB2. Notably, we identified peroxisome proliferator-activated receptor gamma (PPARγ) as a potential target of PCB2 by docking analysis. Subsequent mechanistic studies revealed that PCB2 improved oocyte development capacity and attenuated oxidative stress by activating PPARγ mediated mitochondrial uncoupling. Our findings identify that PCB2 intricately improves oocyte development capacity through targeted activation of the PPARγ/UCP1 pathway, fostering uncoupling lipid catabolism while concurrently mitigating oxidative stress.

Use of platelet-rich plasma on in vitro maturation during bovine embryo production

One of the crucial aspects to be considered for successful in vitro production (IVP) of embryos is the composition of the various media used throughout the stages of this reproductive biotechnology. The cell culture media employed should fulfill the metabolic requirements of both gametes during oocyte maturation and sperm development, as well as the embryo during its initial cell divisions. Most IVP protocols incorporate blood serum into the media composition as a source of hormones, proteins, growth factors, and nutrients. Numerous studies have suggested Platelet-Rich Plasma (PRP) as a substitute for fetal sera in cell culture, particularly for stem cells. Therefore, the objective of this study is to assess the potential use of PRP as a replacement for fetal bovine serum (FBS) during oocyte maturation for in vitro production of bovine embryos. During in vitro maturation (IVM), cumulus-oocyte complexes (COCs) were allocated into the following experimental groups: Group G1 (IVM medium with 5% PRP); Group G2 (MIV medium with 5% PRP and 5% SFB); Group G3 (MIV medium with 5% SFB); and Group G4 (MIV medium without either PRP or SFB). Subsequently, the cumulus-oocyte complexes were fertilized with semen from a single bull, and the resulting zygotes were cultured for seven days. Cleavage and blastocyst formation rates were assessed on days 2 and 7 of embryonic development, respectively. The quality of matured COCs was also evaluated by analyzing the gene expression of HSP70, an important protein associated with cellular stress. The results demonstrated that there were no significant differences among the experimental groups in terms of embryo production rates, both in the initial cleavage stages and blastocyst formation (except for the G4 group, which exhibited a lower blastocyst formation rate on D7, as expected). This indicates that PRP could be a cost-effective alternative to SFB in the IVP of embryos.

In vitro maturation in synthetic oviductal fluid increases gene expression associated with quality and lipid metabolism in bovine oocytes

Traditionally, in vitro oocyte and embryo culture progresses through a series of varying culture medium. To investigate simplifying the in vitro production of bovine cumulus-oocyte complexes (COCs), this study used synthetic oviductal fluid (SOF) supplemented with conjugated linoleic acid (CLA). Special interest was placed on gene expression linked to lipid metabolism and oocyte maturation. COCs were matured in different media: Medium 199 (M199 group), M199 with 100 μM CLA (M199 + CLA group), SOF (SOF group), and SOF with 100 μM CLA (SOF + CLA group). COCs matured with SOF showed a higher relative abundance of mRNA of quality indicators gremlin 1 (GREM1) and prostaglandin-endoperoxide synthase 2 (PTGS2) in oocytes, and GREM1 in cumulus cells compared with in the M199 group. SOF medium COCs had a higher relative abundance of fatty acid desaturase 2 (FADS2) compared with the M199 group, which is essential for lipid metabolism in oocytes. Furthermore, the abundance of stearoyl-coenzyme A desaturase 1 (SCD1) in oocytes matured with SOF was not influenced by the addition of CLA, whereas the relative abundance of SCD1 was reduced in M199 medium with CLA. We concluded that maturation in SOF medium results in a greater abundance of genes linked to quality and lipidic metabolism in oocytes, regardless of the addition of CLA.

Developmental, cytogenetic and epigenetic consequences of removing complex proteins and adding melatonin during in vitro maturation of bovine oocytes

Background

In vitro maturation (IVM) of germinal vesicle intact oocytes prior to in vitro fertilization (IVF) is practiced widely in animals. In human assisted reproduction it is generally reserved for fertility preservation or where ovarian stimulation is contraindicated. Standard practice incorporates complex proteins (CP), in the form of serum and/or albumin, into IVM media to mimic the ovarian follicle environment. However, the undefined nature of CP, together with batch variation and ethical concerns regarding their origin, necessitate the development of more defined formulations. A known component of follicular fluid, melatonin, has multifaceted roles including that of a metabolic regulator and antioxidant. In certain circumstances it can enhance oocyte maturation. At this stage in development, the germinal-vesicle intact oocyte is prone to aneuploidy and epigenetic dysregulation.

Objectives

To determine the developmental, cytogenetic and epigenetic consequences of removing CP and including melatonin during bovine IVM.

Materials and methods

The study comprised a 2 x 2 factorial arrangement comparing (i) the inclusion or exclusion of CP, and (ii) the addition (100 nM) or omission of melatonin, during IVM. Cumulus-oocyte complexes (COCs) were retrieved from stimulated cycles. Following IVM and IVF, putative zygotes were cultured to Day 8 in standard media. RNAseq was performed on isolated cumulus cells, cytogenetic analyses (SNP-based algorithms) on isolated trophectoderm cells, and DNA methylation analysis (reduced representation bisulfite sequencing) on isolated cells of the inner-cell mass.

Results

Removal of CP during IVM led to modest reductions in blastocyst development, whilst added melatonin was beneficial in the presence but detrimental in the absence of CP. The composition of IVM media did not affect the nature or incidence of chromosomal abnormalities but cumulus-cell transcript expression indicated altered metabolism (primarily lipid) in COCs. These effects preceded the establishment of distinct metabolic and epigenetic signatures several days later in expanded and hatching blastocysts.

Conclusions

These findings highlight the importance of lipid, particularly sterol, metabolism by the COC during IVM. They lay the foundation for future studies that seek to develop chemically defined systems of IVM for the generation of transferrable embryos that are both cytogenetically and epigenetically normal.

Molecular phenotypes of bovine blastocyst derived from in vitro-matured oocyte supplemented with PAPP-A

Insulin-like growth factor-1 (IGF-1) regulates cellular lipid content, whereas pregnancy-associated plasma protein-A (PAPP-A) increases IGF-1 bioavailability. Using in vitro-matured cumulus-oocyte complexes, we aimed to evaluate the impact of PAPP-A on the blastocyst lipid content, embryo cryotolerance and embryonic transcriptional profile. We determined that PAPP-A did not affect the lipid content of oocytes, blastocysts, or blastocyst yield (P > 0.05). However, PAPP-A modulated the embryo transcriptional profiles by downregulating PPARGC1A and AKR1B1, which are related to lipid metabolism; CASP9, a pro-apoptotic gene; and IFN-τ, a marker of embryo quality (P < 0.05). Furthermore, the use of PAPP-A improved blastocyst re-expansion in the first 3 h of culture after vitrification (P < 0.05). Although PAPP-A did not affect the blastocyst lipid content or embryo production, we suggest that embryonic transcriptional modulation could contribute to maintain the balance in embryo lipid metabolism. Furthermore, PAPP-A's approach seems to control key intracellular pathways that improve post-cryopreservation development of blastocysts.

Beyond energy provider: multifunction of lipid droplets in embryonic development

Since the discovery, lipid droplets (LDs) have been recognized to be sites of cellular energy reserves, providing energy when necessary to sustain cellular life activities. Many studies have reported large numbers of LDs in eggs and early embryos from insects to mammals. The questions of how LDs are formed, what role they play, and what their significance is for embryonic development have been attracting the attention of researchers. Studies in recent years have revealed that in addition to providing energy for embryonic development, LDs in eggs and embryos also function to resist lipotoxicity, resist oxidative stress, inhibit bacterial infection, and provide lipid and membrane components for embryonic development. Removal of LDs from fertilized eggs or early embryos artificially leads to embryonic developmental arrest and defects. This paper reviews recent studies to explain the role and effect mechanisms of LDs in the embryonic development of several species and the genes involved in the regulation. The review contributes to understanding the embryonic development mechanism and provides new insight for the diagnosis and treatment of diseases related to embryonic developmental abnormalities.

L-carnitine enhances developmental potential of bovine oocytes matured under high lipid concentrations in vitro

Maternal obesity elevates non-esterified fatty acids (NEFA) follicular concentrations. Bovine cumulus-oocyte complexes (COCs) matured in vitro under high NEFA have altered metabolism and reduced quality. Systemically, obesity promotes altered mitochondrial metabolism linked to L-carnitine insufficiency. We hypothesized that L-carnitine supplementation during IVM of bovine COCs in the presence of high NEFA would lessen the negative effects of exposure to excessive lipids on embryonic development and oxidative stress. COCs were collected from abattoir ovaries and matured in four groups: CON (control), LC (3 mM L-carnitine), HN (high NEFA: 200uM oleic, 150uM palmitic and 75uM stearic acid), and HNLC (HN and LC). Mature oocytes were assayed for aerobic and anaerobic metabolism utilizing oxygen and pH microsensors or fertilized in vitro (D0). Cleavage (D3) and blastocyst (D7, D8) rates were assessed. D3 embryos with ≥ 4 cells were stained for cytosolic and mitochondrial ROS. D8 blastocysts were assayed for gene transcript abundance of metabolic enzymes. Oocyte metabolism was not affected by IVM treatment. D3 formation of embryos with ≥ 4 cells were lower in LC or HN than CON or HNLC; blastocyst rates were greater for CON and lower for HN than LC and HNLC. D3 embryo mitochondrial and cytosolic ROS were reduced in HNLC when compared to other groups. IVM in HN altered blastocyst gene transcript abundance when compared to CON, but not LC or HNLC. In conclusion, supplementation with L-carnitine protects oocytes exposed to high NEFA during IVM and improves their developmental competence, suggesting that high lipid exposure may lead to L-carnitine insufficiency in bovine oocytes.

Leonurine improves bovine oocyte maturation and subsequent embryonic development by reducing oxidative stress and improving mitochondrial function

It is acknowledged that excessive reactive oxygen species (ROS) level attributes greatly to the compromised developmental potential of oocytes matured in vitro. Although agents were applied to alleviate ROS levels, results were varied because of the distinct antioxidative activity and cell toxicity. Leonurine (LEO), extracted from the natural Chinese herb motherwort, is considered to be a potent free radical scavenger. Yet, it is undetermined whether LEO is benefit for oocyte development during in vitro maturation (IVM). In the present study, the effect of LEO on the quality of bovine oocyte as well as the underlying mechanism was investigated. We found that maturation rate (P < 0.01), subsequent blastocyst formation rate (P < 0.05), and the total blastocyst cell number (P < 0.05) after parthenogenetic activation were significantly increased in the group treated with 20 μM LEO. Moreover, a dramatic decline in ROS (P < 0.01), decreased lipid content (P < 0.01), elevated MMP level (P < 0.05), increased ATP content (P < 0.05), and reduced mitochondrial temperature (P < 0.01) were observed in oocytes treated with LEO. Furthermore, the expression level of anti-apoptotic protein BCL2 was significantly higher in LEO treated oocytes (P < 0.01), and the ratio of BAX/BCL2 was obvious decreased (P < 0.01). Finally, we found that LC3B intensity was significantly reduced (P < 0.05) while the rate of EdU positive nuclei was markedly increased (P < 0.05) in embryos derived from LEO-treated oocytes. Our results demonstrate that LEO exhibits a potent protective role in the acquisition of oocyte development capacity against oxidative stress during IVM, and provides a new solution for optimizing the in vitro culture system of bovine embryos.

Expression profile of key genes involved in DNA repair mechanisms in bovine cumulus cells cultured with bovine serum albumin or fetal calf serum

Cumulus cells from cumulus-oocyte complexes (COC) matured in vitro in serum-free medium show high incidence of apoptosis and DNA double-strand breaks (DSB). This study aimed to characterize the transcript expression profile of selected genes involved in DNA repair mechanisms in bovine cumulus cells cultured with bovine serum albumin (BSA) or fetal calf serum (FCS). Briefly, bovine cumulus-oocyte complexes were in vitro matured with either, 0.4% BSA or 10% FCS for 3, 6, 12 or 24 h. The total RNA of cumulus cells was used for real-time PCR analysis. Transcript abundance of XRCC6, XRCC5, DNAPK, GAAD45B, TP53BP1, RAD50, RAD52, ATM and BRCA2 target genes changed as the IVM proceeded (P < 0.05). However, an interaction between protein source (FCS or BSA) and time was not detected (P ≥ 0.05). Cumulus cells from COCs matured with BSA presented higher mRNA expression of two genes compared to FCS group: TP53BP1 at 6 h and BRCA1 at 3, 6, 12 and 24 h (P < 0.05). In summary, our results showed for the first time the expression profile of the key genes involved in DSB repair mechanisms in cumulus cells obtained from bovine COCs matured with FCS or BSA. The higher mRNA expression of BRCA1 and TP53BP1 and lower mRNA expression of TNFAIP6 suggests an increase in apoptosis rate and DNA damage in cumulus cells cultured in BSA-supplemented medium and may explain, at least to some extent, the reduced developmental potential of bovine oocytes matured in serum-free medium.

Effect of ovarian growth factors on ultra-structural maturation in frozen human immature oocytes after in vitro maturation: a comparative study

BACKGROUND

In artificial reproductive technique (ART), nearly 20% of human oocytes are immature in the germinal vesicle (GV) phase. Consequently, the best method for reserving them is cryopreserving GV oocytes, and in vitro maturation (IVM) is recommended. The aim of this study was to determine the ultrastructure characteristics of fresh and vitrified immature human oocytes after in vitro maturation in conditioned mediums.

METHODS

This study was a comparative laboratory study carried out in 2018 at Afzalipur Infertility Center in Kerman. 170 fresh and 198 vitrified GV oocytes were cultured within three IVM mediums; α-mem as control medium, α-mem supplemented with human bone marrow mesenchymal stem cells (BM-MSCs) and α-mem supplemented with ovarian growth factors (O.F). After 48 h, the maturation rate and morphological feature of IVM oocytes [132 fresh IVM (fIVM) and 134 vitrified IVM (vIVM)] were evaluated. For the ultrastructure study, 10 IVM oocytes from each medium were compared with 10 fresh in vivo oocytes cancelled from ART.

RESULTS

The survival rate of vitrified GV oocyte after thawing was 88.88%. The oocyte maturation rate was reduced in vIVM compared to the fIVM group (76.33% vs. 77.95%); the highest oocyte maturation rate in the O.F fIVM and lowest in α-mem vIVM (82.35% vs. 71.42%). The lowest number of cortical granules was observed in α-mem vIVM, but the greatest presence of M-SER aggregates was in O.F fIVM. In vIVM oocytes, the oolemma contained irregular little microvillus organization.

CONCLUSIONS

The O.F mediums have shown the highest maturation which defends the oocyte ultra-structural conservation.

Extracellular vesicles from oviductal and uterine fluids supplementation in sequential in vitro culture improves bovine embryo quality

Background

In vitro production of bovine embryos is a well-established technology, but the in vitro culture (IVC) system still warrants improvements, especially regarding embryo quality. This study aimed to evaluate the effect of extracellular vesicles (EVs) isolated from oviductal (OF) and uterine fluid (UF) in sequential IVC on the development and quality of bovine embryos. Zygotes were cultured in SOF supplemented with either BSA or EVs-depleted fetal calf serum (dFCS) in the presence (BSA-EV and dFCS-EV) or absence of EVs from OF (D1 to D4) and UF (D5 to D8), mimicking in vivo conditions. EVs from oviducts (early luteal phase) and uterine horns (mid-luteal phase) from slaughtered heifers were isolated by size exclusion chromatography. Blastocyst rate was recorded on days 7–8 and their quality was assessed based on lipid contents, mitochondrial activity and total cell numbers, as well as survival rate after vitrification. Relative mRNA abundance for lipid metabolism-related transcripts and levels of phosphorylated hormone-sensitive lipase (pHSL) proteins were also determined. Additionally, the expression levels of 383 miRNA in OF- and UF-EVs were assessed by qRT-PCR.

Results

Blastocyst yield was lower (P < 0.05) in BSA treatments compared with dFCS treatments. Survival rates after vitrification/warming were improved in dFCS-EVs (P < 0.05). EVs increased (P < 0.05) blastocysts total cell number in dFCS-EV and BSA-EV compared with respective controls (dFCS and BSA), while lipid content was decreased in dFCS-EV (P < 0.05) and mitochondrial activity did not change (P > 0.05). Lipid metabolism transcripts were affected by EVs and showed interaction with type of protein source in medium (PPARGC1B, LDLR, CD36, FASN and PNPLA2, P < 0.05). Levels of pHSL were lower in dFCS (P < 0.05). Twenty miRNA were differentially expressed between OF- and UF-EVs and only bta-miR-148b was increased in OF-EVs (P < 0.05).

Conclusions

Mimicking physiological conditions using EVs from OF and UF in sequential IVC does not affect embryo development but improves blastocyst quality regarding survival rate after vitrification/warming, total cell number, lipid content, and relative changes in expression of lipid metabolism transcripts and lipase activation. Finally, EVs miRNA contents may contribute to the observed effects.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40104-022-00763-7.

Macromolecules Influence Cellular Competence and Expression Level of IGFs Genes in Bovine Oocytes In Vitro

In vitro maturation (IVM) of mammalian oocytes, which influences subsequent in vitro development of embryos, is affected by the macromolecule content in culture media for the success of oocyte maturation competence, in which the cytoplasmic and nuclear reprogramming events occur. The insulin-like growth factor family (IGFs) promotes the maturation of bovine oocytes and the expansion of cumulus cells and also inhibits apoptosis. This study was, therefore, designed to examine the effects of macromolecules (bovine serum albumin, BSA; fetal calf serum, FCS; and polyvinyl alcohol, PVA) on in vitro nuclear maturation, total cellular protein, glutathione peroxidase (GPx) enzyme activity, and the gene expression level of IGF1, IGF2, and their receptor in bovine oocytes. Oocytes obtained from bovine ovaries were cultured in bicarbonate-buffered medium 199 supplemented with 4 mg/mL BSA, 10% FCS, 1 mg/mL PVA, and without macromolecule supplement (control) during 22 h in the air with a humidified atmosphere and 5% CO2 at 38.5 °C temperature. Supplementation of BSA and FCS increased (χ2 = 9.84; p < 0.05) the percentages of oocytes that reached metaphase II compared to the control and PVA. The amount of protein per ml of cell extracts of oocytes matured in FCS supplemented culture media was higher (p < 0.05) than the oocytes in the PVA and control. The levels of GPx enzyme activity in cell extracts isolated from oocytes in each experimental group did not change over time, but the GPx enzyme activity in oocytes matured in PVA-supplemented culture media was lower (p < 0.05) than in oocytes in the other experimental groups. Transcript for the IGF1 gene was not detected in all experimental groups, but the supplementation of BSA and FCS significantly elevated the transcript level of the IGF2 gene. In addition, the maturation of oocytes with BSA-supplemented media increased the transcript level of the IGF1R gene, whereas the transcript level of the IGF2R gene was similar among macromolecule supplementation groups. The current study concluded that BSA and FCS could improve in vitro bovine oocyte development due to supporting nuclear maturation and increasing the total cellular protein content, GPx enzyme, and transcript activity.

Effects of different stimulators of cGMP synthesis on lipid content in bovine oocytes matured in vitro

Bovine oocytes and blastocysts produced in vitro are frequently of lower quality and less cryotolerant than those produced in vivo, and greater accumulation of lipids in the cytoplasm has been pointed out as one of the reasons. In human adipocytes cGMP signaling through the activation of PKG appears to be involved in lipid metabolism, and components of this pathway have been detected in bovine cumulus-oocyte complexes (COCs). The aim of this study was to investigate the influence of this pathway on the lipid content in oocytes and expression of PLIN2 (a lipid metabolism-related gene) in cumulus cells. COCs were matured in vitro for 24 h with different stimulators of cGMP synthesis. The activation of soluble guanylyl cyclase (sGC) by Protoporphyrin IX reduced lipid content (22.7 FI) compared to control oocytes (36.45 FI; P <0.05). Stimulation of membrane guanylyl cyclase (mGC) with natriuretic peptides precursors A and C (NPPA and NPPC) had no effect (36.5 FI; P>0.05). When the PKG inhibitor KT5823 was associated with Protoporphyrin IX, its effect was reversed and lipid contents increased (52.71 FI; P<0.05). None of the stimulators of cGMP synthesis affected the expression of PLIN2 in cumulus cells. In conclusion, stimulation of sGC for cGMP synthesis promotes lipolytic activities in bovine oocytes matured in vitro and such effect is mediated by PKG. However, such effect may vary depending on the stimulus received and/or which synthesis enzyme was activated, as stimulation of mGC had no effects.

Modulation of lipid metabolism through multiple pathways during oocyte maturation and embryo culture in bovine

Lipid accumulation occurs in cultured embryos and is associated with reduced cryotolerance. Here we report the use of a multiple pathway lipid modulator cocktail (l-carnitine, linoleic acid and forskolin) to improve cryosurvival. First, we stained oocytes and embryos with Oil Red to examine the time course of lipid accumulation during in vitro fertilization (IVF) and embryo culture. Then we evaluated the effects of the lipid modulators cocktail on lipid content, developmental rates and survival after vitrification. In our conditions, lipid accumulation was detected (P < 0.05) at the end of in vitro maturation (IVM) and after 4 days of embryo culture (D4-D5). In experiment 1, we used lipid modulator cocktail during IVM. Reduced (P < 0.05) lipid accumulation was detected in oocytes (Control: 49.9 ± 1.6, Lip. Mod. IVM: 45.0 ± 1.8) but no changes were present at blastocyst stage (Control: 62.4 ± 2.6, Lip. Mod. IVM: 66.8 ± 2.7). Treated oocytes presented decreased (P < 0.05) blastocyst rates and lower (P < 0.05) re-expansion after vitrification. In experiment 2, lipid modulators cocktail was used during embryo culture (from D4-D7 or D6-D7). Treatment had an effect on lipid metabolism, as lipid content was increased (P < 0.05) in D7 blastocysts in treated groups (Control: 52.7 ± 3.1a, D4: 65.9 ± 2.6b, D6: 78.1 ± 2.7b). However, no effect was present for cleavage, blastocyst and cryosurvival rates. No difference was detected in mean cell number comparing the three groups (Control: 78.9 ± 9.6, D4: 82.6 ± 16.5, D6: 68.3 ± 7.8), but apoptosis rate was increased (P < 0.05) in vitrified-warmed blastocysts from treated groups (Control: 14.77*, D4: 22.28, D6: 22.22). We concluded that the combined use of lipid modulators was efficient to promote changes in lipid content of oocytes and embryos in bovine, but those changes did not reflect positively on embryo development or cryosurvival.

Effect of supplementation of medium with Bauhinia forficata recombinant lectins on expression of oxidative stress genes during in vitro maturation of bovine oocytes

The lectin of Bauhinia forficata (nBfL) is a protein able to bind reversibly to N-acetylgalactosamine, performing several functions and one of them is the antiproliferative activity in tumor cells, but its effects have not yet been evaluated in female gametes. The objective of the present study was to determine the additional effect of B. forficata recombinants lectins in the medium of maturation in vitro of bovine oocytes in expression of genes related to oxidative stress pathways. To get the proteins, the gene for this recombinant lectin (rBfL) and its truncated isoform (rtBfL) were cloned and expressed in Escherichia coli (E.coli). The oocytes obtained through follicular puncture were incubated in IVM medium for 24 h containing concentrations of 10 μg/mL, 50 μg/mL and 100 μg/mL of nBfL, rBfL and rtBfL, and a no treated group as a control. In the groups treated with the concentration of 100 μg / mL, the gene expression of genes involved in oxidative stress SOD2, CAT, GPX-1, GSR, NOS2 and apoptosis BAX, CASP3 were evaluated. The rtBfL increased the expression of the SOD2, GSR and NOS2 genes and all the tested lectins increased the expression of the CASP3 gene compared to the control group. These findings indicate that the tested concentrations of the B. forficata recombinants lectins probably influence the expression of oxidative stress genes and increase the expression of the apoptotic gene CASP3 during in vitro maturation of bovine oocytes.

Nobiletin enhances the development and quality of bovine embryos in vitro during two key periods of embryonic genome activation

In vitro culture can alter the development and quality of bovine embryos. Therefore, we aimed to evaluate whether nobiletin supplementation during EGA improves embryonic development and blastocyst quality and if it affects PI3K/AKT signaling pathway. In vitro zygotes were cultured in SOF + 5% FCS (Control) or supplemented with 5, 10 or 25 µM nobiletin (Nob5, Nob10, Nob25) or with 0.03% dimethyl-sulfoxide (C_DMSO) during minor (2 to 8-cell stage; MN_EGA) or major (8 to 16-cell stage; MJ_EGA) EGA phase. Blastocyst yield on Day 8 was higher in Nob5 (42.7 ± 1.0%) and Nob10 (44.4 ± 1.3%) for MN_EGA phase and in Nob10 (61.0 ± 0.8%) for MJ_EGA phase compared to other groups. Mitochondrial activity was higher and lipid content was reduced in blastocysts produced with nobiletin, irrespective of EGA phase. The mRNA abundance of CDK2, H3-3B, H3-3A, GPX1, NFE2L2 and PPARα transcripts was increased in 8-cells, 16-cells and blastocysts from nobiletin groups. Immunofluorescence analysis revealed immunoreactive proteins for p-AKT forms (Thr308 and Ser473) in bovine blastocysts produced with nobiletin. In conclusion, nobiletin supplementation during EGA has a positive effect on preimplantation bovine embryonic development in vitro and corroborates on the quality improvement of the produced blastocysts which could be modulated by the activation of AKT signaling pathway.

Transcriptional Profiling of Porcine Blastocysts Produced In Vitro in a Chemically Defined Culture Medium

The development of chemically defined media is a growing trend in in vitro embryo production (IVP). Recently, traditional undefined culture medium with bovine serum albumin (BSA) has been successfully replaced by a chemically defined medium using substances with embryotrophic properties such as platelet factor 4 (PF4). Although the use of this medium sustains IVP, the impact of defined media on the embryonic transcriptome has not been fully elucidated. This study analyzed the transcriptome of porcine IVP blastocysts, cultured in defined (PF4 group) and undefined media (BSA group) by microarrays. In vivo-derived blastocysts (IVV group) were used as a standard of maximum embryo quality. The results showed no differentially expressed genes (DEG) between the PF4 and BSA groups. However, a total of 2780 and 2577 DEGs were detected when comparing the PF4 or the BSA group with the IVV group, respectively. Most of these genes were common in both in vitro groups (2132) and present in some enriched pathways, such as cell cycle, lysosome and/or metabolic pathways. These results show that IVP conditions strongly affect embryo transcriptome and that the defined culture medium with PF4 is a guaranteed replacement for traditional culture with BSA.

Lipid Metabolism in Bovine Oocytes and Early Embryos under In Vivo, In Vitro, and Stress Conditions

Lipids are a potential reservoir of energy for initial embryonic development before activation of the embryonic genome and are involved in plasma membrane biosynthesis. Excessive lipid droplet formation is detrimental to cryotolerance and is related to alterations in mitochondrial function, which likely affects lipid metabolism. Increased lipid accumulation in in vitro produced embryos is a consequence of the stress during in vitro embryonic development process. There are several open questions concerning embryo lipid metabolism and developmental potential. Oocyte maturation and embryo development in vivo and in vitro may vary if the donors are subjected to any type of stress before follicle puncture because crucial changes in oocyte/embryonic metabolism occur in response to stress. However, little is known about lipid metabolism under additional stress (such as heat stress). Therefore, in this review, we aimed to update the information regarding the energy metabolism of oocytes and early bovine embryos exhibiting developmental competence, focusing on lipid metabolic pathways observed under in vivo, in vitro, and stress conditions.

Maturation system affects lipid accumulation in bovine oocytes

This study evaluated the effects of three maturation systems, namely invitro (MatV) and invivo (MatS) systems, as well as intrafollicular transfer of immature oocytes (IFIOT; MatT), on the accumulation of lipid droplets in bovine oocytes. Lipids were evaluated using confocal microscopy and transmission electron microscopy. The expression of genes related to lipid metabolism, namely acyl-CoA synthetase short chain family member 2 (ACSS2), ELOVL fatty acid elongase 1 (ELOVL1) and fatty acid binding protein 3 (FABP3), was quantified by quantitative polymerase chain reaction. The mean (±s.d.) area occupied by lipids in immature oocytes (13±2%) was similar to those matured invivo (MatS, 16±2%; MatT, 12±2%). However, there was a significant increase in lipids in oocytes in the MatV group (24±2%) compared with all other groups (P<0.001). In the ultrastructural evaluations, MatV oocytes also showed the highest lipid content. The expression of ELOVL1 and FABP3 was similar in the MatS and IFIOT groups. However, transcript levels of ACSS2 were lower in IFIOT than MatV oocytes. These results indicate, for the first time, that oocytes matured by IFIOT are similar to those matured invivo with regard to lipid accumulation, which indicates better quality than those matured invitro.

Molecular and cellular effects of insulin-like growth factor-1 and LongR3-IGF-1 on in vitro maturation of bovine oocytes: comparative study

Addition effects of insulin-like growth factor-1 (IGF-1) and its synthetic analogue insulin-like growth factor-1 recombinant-3 (LongR3-IGF-1) after in vitro maturation (IVM) of cattle cumulus-oocyte complexes (COCs) were compared and evaluated on meiotic progression, apoptosis and profile genes of oocyte competence (GDF9, BMP15, BAX, BCL2, OOSP1, IGFBP2, IGBFP4 and IGFBP5), and their respective cumulus cells (AREG, EGFR, FSHR, COX2, BAX, BCL2, IGFBP2, IGFBP4 and IGFBP5). The 739 COCs (n = 10 pools) of bovine ovaries were collected, selected and matured with IGF-1 (100 ng/mL), LongR3-IGF-1 (100 ng/mL), and in two control groups with 0.1% polyvinyl alcohol (PVA) or 10% fetal bovine serum (FBS), for 22-24 h. The statistical analysis was performed by a linear mixed effects model, ANOVA and Tukey tests. There was no statistical difference between experimental groups taken into account the meiotic progression and apoptosis (P > 0.05). Nevertheless, there were statistical differences (P ≤ 0.05) among FBS, IGF-1 and LongR3-IGF-1 groups for IGFBP4 gene expression, and among PVA, IGF-1 and LongR3-IGF-1 for COX2 gene expression in cumulus cells. Moreover, statistical difference was found for BCL2 gene expression between IGF-1, FBS and PVA groups and for IGFBP4 gene expression between LongR3-IGF-1, PVA and FBS in oocytes. There was no statistical difference between experimental groups for other genes evaluated. These results showed a good performance of IVM of bovine oocytes in the presence of LongR3-IGF-1 and the possibility of replacement of IGF-1 and FBS.

Influence of l-carnitine on lipid metabolism of buffalo cumulus-oocyte complexes matured in either fetal bovine serum or fatty acid-free bovine serum albumin

Consequences of oocyte supplementation with l-carnitine may vary depending on species-specific cellular lipid profile, level of mitochondrial activity, or even on ipid availability in culture medium. This study aimed to evaluate l-carnitine supplementation on competence and gene expression of enzymes related to lipid metabolism in oocytes and cumulus cells from buffalo COCs matured in the presence or absence of fetal bovine serum (FBS). COCs were matured in vitro in FBS (10%) or bovine serum albumin fatty acid-free (BSA-FAF) (0.4%) and with or without supplementation with l-carnitine (3.03 mM). COCs matured in the presence of FBS or BSA-FAF were fertilized and cultured, then supplemented with l-carnitine during in vitro maturation or in vitro embryo culture. Finally, in vivo mature and immature COCs were included for gene expression analysis. COCs matured in culture medium with FBS in the presence of l-carnitine produced a lower blastocyst rate (p ≤ 0.05) compared to controls. In turn, the blastocyst rate from COCs matured with BSA-FAF in the presence of l-carnitine was similar to controls (p > 0.05), and higher than FBS + L-carnitine treated COCs (p ≤ 0.05). Addition of l-carnitine during embryo culture showed no differences in blastocyst production between experimental groups and controls (p > 0.05). In cumulus cells, gene expression of ACACA, SCD and FASN was upregulated in COCs matured in the presence of BSA-FAF + L-carnitine, while all genes in oocytes were significantly expressed upregulated by COCs matured in vivo, and only BSA-FAF + L-carnitine group showed similar expression of the FASN gene. In conclusion, the consequences of l-carnitine supplementation during in vitro maturation of buffalo COCs on oocyte competence vary depending on presence or absence of FBS in culture. With FBS, l-carnitine impairs oocyte competence, while in its absence, gene expression suggests adequate lipid metabolism and increased oocyte competence.

Inhibiting diacylglycerol acyltransferase-1 reduces lipid biosynthesis in bovine blastocysts produced in vitro

Diacylglycerol acyltransferase-1 (DGAT1) is one of the DGAT enzymes that catalyzes the final step in the synthesis of triacylglycerol, which is a major component of the lipid droplets in embryos. Intracellular lipids accumulated in embryos produced in vitro have been associated with reduced cryotolerance and quality. The objective of the present study was to investigate the influence of DGAT1 inhibition on embryo development, quality, and post-vitrification survival, in addition to expression profiles of selected lipid metabolism-regulating and oxidative stress genes. Bovine cumulus-oocyte complexes were matured and fertilized in vitro and were cultured in synthetic oviduct fluid (SOF) supplemented with 5% fetal calf serum (FCS) alone (Control) or with 1, 5, 10 or 50 μM DGAT1 inhibitor (A922500®; D1, D5, D10, and D50, respectively) or 0.1% dimethyl sulfoxide (CDMSO: vehicle for DGAT1 inhibitor dilution) from 54 h post-insemination until Day 8 post insemination. No differences were found in blastocyst yield on days 7 and 8 in Control, CDMSO, D10, and D50 groups. Embryos cultured with 10 or 50 μM DGAT1 inhibitor had greater mitochondrial activity (P < 0.01), and increased number of cells (P < 0.05), while the cytoplasmic lipid content was reduced (P < 0.01), the latter associated with altered expression profiles of selected genes regulating lipid metabolism or genes related with oxidative stress (transcript abundance increased for SLC2A1 and SLC2A5 and decreased for DGAT1 and GPX1). Importantly, the survival rate of blastocysts produced with 10 μM DGAT1 was higher than that of Control, CDMSO and D50 groups at 72 h after vitrification and warming (73.8 vs 57.1, 55.9 and 56.1%, respectively, P < 0.001). In conclusion, inhibition of DGAT1 synthesis in bovine embryos produced in vitro abrogates the negative effect of FCS by decreasing their lipid content, increasing mitochondria activity and improving embryo cryotolerance, as well as favoring the expression of lipid metabolism regulating and oxidative stress-related transcripts.

l-Carnitine Supplementation during In Vitro Maturation and In Vitro Culture Does not Affect the Survival Rates after Vitrification and Warming but Alters Inf-T and ptgs2 Gene Expression

l-carnitine is a potent antioxidant used for in vitro culture systems. Controversial results have been reported using l-carnitine in culture medium at different stages of in vitro bovine embryo production. Cumulus-oocyte complexes (n = 843) were in vitro-fertilized and cultured and added (treatment group) or not added (control group) with l-carnitine. At day three of culture, each group was subdivided into two subgroups receiving no l-carnitine (group 1), 3.8 mM l-carnitine added during in vitro maturation (group 2), 1.5 mM added during the in vitro culture (group 3), and 3.8 mM and 1.5 mM added during the maturation and culture, respectively (group 4). At day 8, blastocyst embryos were examined for mitochondrial activity, the presence of lipid droplets, total cell number, gene expression, and cryotolerance by vitrification. The data were analyzed with a one-way analysis of variance. l-carnitine added in the late in vitro culture significantly reduced mitochondrial activity and lipid content, and upregulated ifn-τ and ptgs2 gene expression compared to controls (p < 0.05). l-carnitine supplementation did not significantly affect the embryo rate production or survival rate after vitrification and warming (p > 0.05). l-carnitine supplementation significantly improved embryo potential to develop viable pregnancies in agreement with a study reporting improved pregnancy rates.

Platelet rich plasma efficiently substitutes the beneficial effects of serum during in vitro oocyte maturation and helps maintain the mitochondrial activity of maturing oocytes

Platelets contain most of the potent mitogenic factors present in serum and follicular fluid and intraovarian injection of autologous platelet rich plasma (PRP) was shown to improve ovarian function and development of preantral follicles. This study evaluated the effect of PRP on caprine oocyte maturation in vitro and subsequent fertilization and embryonic development. Cumulus oocyte complexes were cultured in a maturation medium supplemented with (1) fetal bovine serum (FBS, control), (2) PRP, extracted from healthy female goats, (3) polyvinyl alcohol (PVA), and (4) PVA plus PRP (PVA-PRP). The degree of cumulus expansion was scored, and denuded oocytes were used for assessment of nuclear maturation, mitochondrial activity, lipid content, redox status, yield and quality of in vitro embryo development, and cryosurvival of the resulting blastocysts. PRP supported the same beneficial effects of FBS on cumulus expansion, nuclear maturation, in vitro developmental competence of oocytes, and survival of vitrified-warmed blastocysts. Moreover, PRP protected oocytes from undesirable effects FBS exerted on the mitochondrial activity and intracytoplasmic lipid content of maturing oocyte. Although PVA could support the same beneficial effects of neither FBS nor PRP on oocyte maturation, its combined addition with PRP improved the yield and quality of oocyte maturation at rates closely similar to PRP. PRP efficiently substitutes beneficial effects of serum during in vitro oocyte maturation and helps maintain the mitochondrial activity of maturing oocytes.

Is it possible to alter the embryo lipid accumulation with reduction of fetal bovine serum and use of l-carnitine for in vitro maturation of bubaline oocytes?

In vitro embryo production (IVEP) is a procedure that can promote genetic improvement in a short time frame. However, the success rates obtained with this biotechnology in water buffaloes are still inconsistent, and can be associated with the high concentration of lipids in the cytoplasm of oocytes and embryos. The objective of this study was to evaluate the effects of reduced concentration of fetal bovine serum (FBS) and/or use of l-carnitine during in vitro maturation (IVM) on the preimplantation development and lipid accumulation in bubaline embryos. In a first experiment, the lowest concentration of FBS in the IVM medium (0%, 2.5%, 5% or 10%) was determined, and the lowest concentration that maintained good embryo development rates was 5%. In a second experiment, the addition of 5 mM of l-carnitine into the maturation medium was evaluated. The blastocysts produced were submitted to lipid evaluation involving staining followed by observation using optical (Oil Red O) and confocal (BODIPY 493/503) microscopy. No difference was observed between the 5% and 10% FBS groups, which were superior to the 0% and 2.5% groups. Furthermore, the performance of the groups treated with 5% and 10% FBS was better than the groups supplemented with l-carnitine. There was no difference regarding embryo lipid accumulation. The results indicated that it is possible to reduce the FBS concentration to 5% in in vitro maturation medium for production of bubaline embryos, and supplementation with 5 mM l-carnitine does not increase embryo production.

Developmental potential of buffalo embryos cultured in serum free culture system

The presence of serum in embryo culture medium has been implicated for increased embryo's sensitivity to cryopreservation, compromised viability, abnormal embryo and fetal development. Hence, designing a serum free culture system is indispensable. The present study aims to compare the efficiency of the serum and granulosa cells monolayer free commercial culture system (SFCS) with the conventional serum supplemented co-culture system (SSCS) and optimized culture system (OCS). Generally, SFCS is designed explicitly for bovine oocyte maturation and embryo culture (SF-IVM and SF-IVC), and SSCS (based on M199, SS-IVM, and SS-IVC) is utilized for buffalo in vitro embryo production. However, OCS is a newly designed culture system in which oocyte maturation is performed in serum supplemented maturation medium, and the subsequent embryos are co-cultured with granulosa cells in serum free culture medium. To evaluate the effect of serum on buffalo embryo production, buffalo oocytes, and their subsequent embryos were cultured in SSCS, SFCS, and OCS, simultaneously. The percentage of cleaved embryos cultured in SSCS and OCS was approximately 4% higher as compared to SFCS. However, OCS significantly showed the maximum proportion of embryos that developed to the blastocyst stage (7d) and hatched (6d) as compared to the SFCS and SSCS. Additionally, OCS promoted the expression of developmentally important genes (BCL2-L1 and VEGF-A), cell number, and cryo-survival ability of blastocysts in comparison with SSCS. Taken together, OCS is more suitable for the oocyte maturation and culture of buffalo embryos. However, to design the serum free culture system, it is recommended to find suitable serum alternatives for in vitro oocyte maturation.

The Replacement of Fetal Bovine Serum with Bovine Serum Albumin During Oocyte Maturation and Embryo Culture Does Not Improve Blastocyst Quality After Slow Freezing Cryopreservation

In the present study, four experimental groups were used: fresh embryos, cultured during in vitro maturation and in vitro culture in media supplemented with bovine serum albumin (BSA) (fresh BSA) or fetal bovine serum (FBS) (fresh FBS); and two groups of cryopreserved and thawed embryos, produced under the same conditions (frozen BSA and frozen FBS). Experiment 1 evaluated the protein source effect on embryo development and response to cryopreservation. At day 7, half of the expanded blastocysts (Bx) from each group were cryopreserved and warmed and the other half were used as controls. After warming, embryos were incubated under the same conditions for 48 hours, and the hatching rate was measured at 24 and 48 hours. The total and the apoptotic cell numbers were measured in a subset of Bx after 24 hours. Experiment 2 used the Bx of experiment 1 to compare the expression of KRT8, PLAC8, FOSL1, HSP1A1, and HSPA5 genes in hatched blastocysts at 24 and 48 hours for all groups. The FBS group showed a higher percentage (p < 0.05) of embryos (42.8% vs. 27.9%) and higher rates of Bx (75.0% vs. 63.8%) on day 7, compared with the BSA group. At 24 hours postwarming, the fresh FBS group showed the highest hatching rate (p < 0.05) in comparison with other treatments. However, at 48 hours, the hatching rate was similar (p > 0.05) among groups: fresh FBS (68.1% ± 23.3%), fresh BSA (70.0% ± 31.0%), frozen FBS (39.2 ± 27.1), and frozen BSA (38.2 ± 23.9). After 24 hours, frozen BSA showed a higher number of cells compared with frozen FBS (p < 0.05). The expression of the PLAC8 gene was higher (p < 0.05) in fresh BSA embryos compared with frozen FBS embryos at 24 hours. In the present study, BSA replacement reduced embryo development, but did not affect the response to cryopreservation. However, upregulation of the PLAC8 gene suggests that embryos cultured in BSA might have better quality to support further development.

Cytoplasm lipids can be modulated through hormone-sensitive lipase and are related to mitochondrial function in porcine IVM oocytes

Intracellular lipids provide energy for oocyte maturation and development. Triglycerides are the main components of cytoplasm lipid droplets, and hydrolysis of triglycerides requires several lipase-mediated steps. The aim of this study was to determine the effects of the β-adrenoceptor agonist isoproterenol (ISO) and the hormone-sensitive lipase (HSL) inhibitor CAY10499 on the IVM of porcine oocytes. ISO (5mg L−1) and CAY10499 (20mg L−1) had positive and negative effects respectively on invitro oocyte maturation and subsequent embryo development. The rates of polar body extrusion, cleavage and blastocyst formation were significantly higher in the ISO-treated group than the control and CAY10499-treated groups. ISO treatment also upregulated intracellular cAMP levels in comparison with the control group, while CAY10499 significantly increased the triglyceride content of matured oocytes when compared with other groups, consistent with the observed decrease in LIPE (HSL) mRNA levels. Furthermore, the inhibitory effects of CAY10499 included decreases in mitochondrial membrane potential and mitochondrial temperature. These results indicate that ISO has a positive effect on the IVM of porcine oocytes, and that intracellular lipid metabolism can be modulated by CAY10499 through inhibition of HSL and is closely related to mitochondrial function.

Screening high-quality fetal bovine serum for porcine oocyte maturation in vitro

Fetal bovine serum (FBS) is widely used in cell cultures due to its high stability and easy access. It was also used as a substitute for porcine follicular fluid (PFF) in previous studies. However, FBS components are unclear, and the presence of FBS in culture media may introduce a variation from batch to batch. This study aimed to establish an effective method to screen FBS in place of PFF in the culture media for porcine oocytes in vitro. We screened FBS from different sources by using porcine fetal fibroblast cells. The effects of six FBS samples on porcine fetal fibroblast cell growth were tested via frozen cell survival assay, cell clone formation assay, cell growth curve, and cell passage activity assay. The best serum that we called GFBS (heat-inactivated FBS, cat. no. 10500-64; Gibco) showed a similar effect on the maturation and development of porcine oocytes to that of PFF and can be used as a good substitute for PFF. These results suggested that the porcine fetal fibroblast cell culture test can be used as a valuable method to screen FBS for porcine oocyte maturation and embryonic development in vitro.

Effects of EPA on bovine oocytes matured in vitro with antioxidants: Impact on the lipid content of oocytes and early embryo development

The eicosapentaenoic acid (EPA) is an n-3 polyunsaturated fatty acid (PUFA) present in the lipid composition of bovine oocytes. Little is known about the importance of EPA in bovine oocyte maturation and embryo development in vitro. Although previous work suggest that n-3 PUFAs may inhibit oocyte maturation, the available data are inconsistent. In this study, we evaluated the effect of EPA (1, 10, 100 nM) during in vitro maturation (IVM) of bovine oocytes, alone and in combination with vitamin E (VE) or cysteamine (CYS). EPA treatment in IVM decreased oocyte lipid content and affected lipid droplets pattern (P < 0.05). EPA 100 nM reduced oocytes maturation rate (P < 0.05), without affecting cumulus expansion. At the concentrations tested, EPA did not modify embryo development. However, the addition of antioxidants during IVM reduced the levels of reactive oxygen species in the culture system by increasing intracellular glutathione content (P < 0.05). Besides, the combination of EPA with VE or CYS reduced the percentages of MI oocytes after 24 h of IVM (P < 0.05). EPA reduced oocyte lipid content without any detrimental for embryo development.

Lipopolysaccharide and tumor necrosis factor-alpha alter gene expression of oocytes and cumulus cells during bovine in vitro maturation

Communication between the oocyte and cumulus facilitates oocyte growth, cell cycle regulation, and metabolism. This communication is mediated by direct contact between oocytes and cumulus cells, and soluble secreted molecules. Secreted molecules involved in this process are known inflammatory mediators. Lipopolysaccharide (LPS) is detected in follicular fluid and is associated with reduced fertility, whereas accumulation of inflammatory mediators in follicular fluid, including tumor necrosis factor-α (TNF-α), is associated with female infertility. Maturation of oocytes in the presence of LPS or TNF-α reduces meiotic maturation and the capacity to develop to the blastocyst. Here we evaluated the abundance of 92 candidate genes involved immune function, epigenetic modifications, embryo development, oocyte secreted factors, apoptosis, cell cycle, and cell signaling in bovine cumulus cells or zona-free oocytes after exposure to LPS or TNF-α during in vitro maturation. We hypothesize that LPS or TNF-α will alter the abundance of transcripts in oocytes and cumulus cell in a cell type dependent manner. Exposure to LPS altered abundance of 31 transcripts in oocytes (including ACVR1V, BMP15, DNMT3A) and 12 transcripts in cumulus cells (including AREG, FGF4, PIK3IP1). Exposure to TNF-α altered 1 transcript in oocytes (IGF2) and 4 transcripts in cumulus cells (GJA1, PLD2, PTGER4, STAT1). Cumulus expansion was reduced after exposure to LPS or TNF-α. Exposing COCs to LPS had a marked effect on expression of targeted transcripts in oocytes. We propose that altered oocyte transcript abundance is associated with reduced meiotic maturation and embryo development observed in oocytes cultured in LPS or TNF-α.

Importance of lipid metabolism on oocyte maturation and early embryo development: Can we apply what we know to buffalo?

The knowledge about the biological events that regulate lipid metabolism in oocytes and embryos in buffalo is scarce. Lipogenesis, lipolysis, transport and oxidation of fatty acids (FAs) occur in gametes and embryonic cells of all mammalian species, as an intrinsic component of energy metabolism. In oocytes and cumulus cells, degradation of lipids is responsible for the production of ATP that is essential for the metabolic processes that lead to oocyte maturation in in vivo and in vitro culture conditions. Similarly, throughout embryo development, blastomeres have the capacity to use exogenous and/or endogenous lipid reserves to serve as an energy source necessary for early embryonic development. In addition, supplementation of culture media with L-carnitine to promote lipid metabolism during in vitro oocyte maturation and early embryonic development leads to an improved embryo quality. The limited scientific evidence available in buffalo indicates there is relatively greater oocyte lipid content as compared with many other species that undergoes a dynamic distribution during folliculogenesis and follicle maturation and that has a positive effect on oocyte maturation and embryo development when there is L-carnitine supplementation of the media. Advances in the understanding of the biological peculiarities of lipid metabolism, and the consequences of its alteration on the quality of buffalo gametes and embryos, therefore, are necessary to design specific culture media and laboratory procedures as a strategy to increase in vitro-derived embryo production rates.

Toxicological evaluation of 3-(4-Chlorophenylselanyl)-1-methyl-1H-indole through the bovine oocyte in vitro maturation model

The development of new bioactive molecules based on the molecular hybridization has been widely explored. In line with this, reliable tests should be employed to give information about the toxicology of these new molecules. In this sense, the use of in vitro tests is a valuable tool, especially the in vitro maturation of oocytes (IVM), which is an efficient resource to discover the potential toxicity of synthetic molecules. Thus, the aim of the present study was to evaluate the toxicological effects of the selenium-containing indolyl compound 3-(4-Chlorophenylselanyl)-1-methyl-1H-indole (CMI), on different quality parameters of bovine oocytes through the IVM. Different concentrations of the CMI compound (0, 25, 50, 100, 200 μM) were supplemented during the in vitro maturation process. After, the oocyte maturation rate, glutathione (GSH) levels, reactive oxygen species (ROS) levels, membrane, and mitochondrial integrity were evaluated. The results showed that the lowest concentration of CMI induced the highest GSH production (P < 0.05), an important marker of cytoplasmic quality and maturation. All treatments increased ROS production in relation to non-supplementation (P < 0.05). In addition, oocyte maturation was reduced only with the highest concentration of CMI (P < 0.05). Supplementation with CMI did not impact mitochondrial activity, integrity and cell membrane. To our knowledge, this is the first study that evaluates CMI on the oocyte in vitro maturation process. Importantly, our results did not find any toxic effect of CMI on bovine oocytes. CMI was efficient for cytoplasmic maturation by promoting an increase in the intracellular levels of glutathione.

The effect of adding Rosmarinic and Ascorbic acids to vitrification media on fertilization rate of the mice oocyte: An experimental study

Background

Oocytes vitrification is a pivotal step for the widespread and safekeeping of animal genetic resources. Oocytes endure notable morphological and functional damage during cryopreservation. Oxidative stress is one of the adverse effects that vitrification imparts on oocytes.

Objective

In the present study, we investigated the antioxidant effect of Rosmarinic and Ascorbic acids on the quality and fertilizing ability of frozen-thawed mice oocyte.

Materials and Methods

In this experimental study, germinal vesicle oocytes obtained from two-months-old (30–40gr) NMRI mice were randomly divided into four groups. The basic cryoprotectants were 7.5% (v/v) ethylene glycol+7.5% (v/v) Propanediol as an equilibration media. Vitrification medium contained 15% (v/v) ethylene glycol+15% (v/v) propanediol, and 0.5 M sucrose. In the first group (Control), nothing was added to vitrification mediums, whereas, in the second and third groups, 0.5 mmol/L of Ascorbic acid and 105 µmol/L of Rosmarinic acid were added into vitrification medium, respectively. The cumulative concentration of Rosmarinic and Ascorbic acids were added to group 4. Mouse oocytes were vitrified and preserved for one month. The thawed oocytes were transferred into the α-MEM medium (Alpha Minimum Essential Medium) and maintained in this medium for 24 hr, to be matured and reach the metaphase II stage.

Results

The addition of Rosmarinic and Ascorbic acids to the vitrification solution improved the survival, maturation of Germinal vesicles, fertilization rate, and finally development to 4-cell stage. Maturation rates to 4-cell stage for Ascorbic acid, Rosmarinic acid, and both of them together were 80%, 80.76%, and 86.61%, respectively.

Conclusion

These results indicate that the addition of a cumulative concentration of 0.5 mmol/L Ascorbic acid and 105 µmol/L of Rosmarinic acid to the cryopreservation solution for the mouse immature oocytes would be of significant value (p< 0.01).

Effect of addition of l-carnitine to media for oocyte maturation and embryo culture on development and cryotolerance of bovine embryos produced in vitro

The objective of these experiments was to determine the effect of l-carnitine during oocyte maturation or embryo culture on embryo development and cryosurvival. For Experiments 1-3, embryos were produced in vitro using abattoir-derived cumulus-oocyte complexes (COCs). At d 7 after insemination, embryo development was assessed, and blastocyst and expanded blastocyst stage embryos were harvested and subjected to controlled-rate freezing. Post-thaw cryosurvival was determined by re-expansion and hatching rates at 24, 48 and 72 h post-thaw. In Experiment 1, COCs were matured with or without 3.03 mM l-carnitine. There was no effect of l-carnitine supplementation during maturation on embryo development or post-thaw cryosurvival. In experiment 2, presumptive zygotes were cultured in medium supplemented with or without 5% (v/v) fetal bovine serum and l-carnitine at concentrations of 0.0, 0.75, 1.5 and 3.03 mM. There was no effect of l-carnitine treatment on embryo development, but embryos treated with l-carnitine had increased (P ≤ 0.05) post-thaw re-expansion rates, irrespective of concentration. In experiment 3, presumptive zygotes were cultured with or without 0.75 mM l-carnitine from d 1 to d 4, from d 4 to d 7 or for the entire culture period. There was no effect of l-carnitine during culture on embryo development or post-thaw cryosurvival, regardless of the timing of addition. In Experiment 4, COCs were harvested by ovum pick-up from virgin dairy heifers (n = 24) and subjected to in-vitro embryo production with presumptive zygotes cultured with or without 0.75 mM l-carnitine. At d 7 after insemination, morula and blastocyst stage embryos were harvested and subjected to controlled-rate freezing. Lactating Holstein cows (n = 102) were used as recipients and synchronized for timed embryo transfer. At d 7 after anticipated ovulation, a single embryo was thawed and transferred to the ipsilateral uterine horn of each recipient with a corpus luteum. Pregnancy was diagnosed at d 33, 44 and 72 of gestation. l-carnitine had no effect on the percentage of cows pregnant per embryo transfer (P/ET) after transfer of a frozen-thawed embryo. In conclusion, media supplementation with l-carnitine during in vitro embryo production can improve post-thaw cryotolerance as assessed in vitro but had no effect on P/ET after transfer of frozen-thawed embryos.

In vitro survival, growth, and maturation of sheep oocytes from secondary follicles cultured in serum-free conditions: impact of a constant or a sequential medium containing recombinant human FSH

This study evaluated the in vitro development and maturation of ovine oocytes from secondary follicles cultured in serum-free medium containing fixed or sequential concentrations of recombinant human FSH (rhFSH). Follicles were cultured in α-MEM⁺ alone or with constant (500, 750, or 1,000 ng/mL) or sequential concentrations of rhFSH (seq. 1: day 6 = 500; day 12 = 750; day 18 = 1,000 ng/mL and seq. 2: day 6 = 100; day 12 = 500; day 18 = 1,000 ng/mL). At the end of the experiment, follicular survival was higher (P < 0.05) in 750 ng/mL rhFSH than the control and 1,000 ng/mL rhFSH. As early as day 6 of culture, antral cavity formation was observed in all treatments. Follicular diameter increased progressively and significantly in all treatments throughout 18 d of culture. Furthermore, addition of rhFSH to the medium promoted a significant increase in the percentage of fully grown oocytes in all treatments compared to α-MEM⁺. Mitochondrial activity was higher in rhFSH treatments than in the control, except in rhFSH seq. 2 (P < 0.05). Maturation rates increased in oocytes from intact follicles cultured in 750 ng/mL rhFSH compared to the control (P < 0.05). In conclusion, rhFSH at 750 ng/mL maintained the survival of secondary follicles cultured in serum-free medium, improved oocyte growth, mitochondrial activity, and oocyte maturation.

Contributions from the ovarian follicular environment to oocyte function

The magnitude of oocyte's role for embryo development is categorical. This unique cell contains the machineries and cellular components necessary to remodel male and female chromatin, to sustain early development and to, ultimately, generate a complete and complex individual. However, to gain these competences before fertilization, the oocyte undergoes several morphological, cellular and molecular changes during its lifetime enclosed in the ovarian follicle. This review will briefly revisit how the oocyte orchestrate the follicular cells, and how molecules transit to the oocyte from the innermost (cumulus) and outermost (antrum and granulosa cells) layers surrounding the follicle-enclosed oocyte. Finally, we will discuss the interferences of in vitro culture conditions in the communication of the oocyte with its surrounding cells and the potential strategies to modulate these communication systems to increase oocyte competence.

Steroid-depleted polycystic ovarian syndrome serum promotes in vitro oocyte maturation and embryo development

In vitro maturation (IVM) of immature oocytes obtained from patients with polycystic ovarian syndrome (PCOS) is considered as a novel strategy in order to reduce clinical side effects and cost of in vitro fertilization (IVF) technique. The aim of this study was to evaluate the effects of PCOS whole and steroid-depleted serums on in vitro oocyte maturation indices. Patients with PCOS were selected according to the Rotterdam criteria. Cumulus-oocyte complexes and blood serums were collected and pooled. Cumulus cells and immature oocytes were treated with 10% whole or steroid-depleted serums. Stearoyl-CoA desaturase-1 (SCD1) and cyclooxygenase-2 (COX2) expression levels in cumulus cells were evaluated by quantitative PCR. Fatty acid composition of cumulus cells was analyzed using gas-liquid chromatography. Polar body observation was considered as the oocyte maturation index. Oleate (1.28-fold, p = .006), SCD1 expression (450-fold, p = .001), and COX2 expression (35-fold, p = .02) in cumulus cell, as well as oocyte maturation (p < .001) and in vitro embryo development (p < .05) were significantly higher in treatment with steroid-depleted serum compared to that of whole serum. Steroid depletion of PCOS serum improved its capacity to increase success rate of oocyte maturation, intra-cytoplasmic sperm injection and early embryo development.

Impact of delipidated estrous sheep serum supplementation on in vitro maturation, cryotolerance and endoplasmic reticulum stress gene expression of sheep oocytes

High lipid content of oocytes and embryos in domestic animals is one of the well-known factors associated with poor cryosurvival. Herein, we wanted to determine whether the use of delipidated estrous sheep serum during in vitro maturation (IVM) of ovine oocytes reduces the cytoplasmic lipid droplets content and improves embryo development and cryotolerance after vitrification. Cumulus oocytes complexes (COCs) were matured in vitro for 24 h in medium supplemented with whole or delipidated estrous sheep serum prior to vitrification. Neutral lipid present in lipid droplets of COCs, cleavage rate, embryo development rate on Day 6 and Day 8, and hatching rate on Day 8, were compared among experimental groups. Endoplasmic reticulum stress genes were evaluated in in vitro matured COCs under different lipid conditions prior to vitrification. The lipid droplets’ content (mean fluorescence intensity) of oocytes cultured with IVM media supplemented with delipidated serum was lower than COCs matured with whole serum (7.6 ± 1.7 vs. 22.8 ± 5.0 arbitrary units, respectively; P< 0.05). Despite IVM treatment, oocytes subjected to vitrification showed impaired competence compared with the non-vitrified groups (P<0.05). No significant differences in embryo production were observed in non-vitrified COCs after maturation in delipidated or whole serum (33.4±4.9 vs 31.9 ±4.2). COCs matured in delipidated serum and subjected to vitrification showed increased expression of ATF4, ATF6, GRP78, and CHOP10 genes (ER stress markers). Collectively, our results demonstrate that although supplementation of IVM medium with delipidated estrous sheep serum reduces the presence of cytoplasmic lipid droplets in oocytes after maturation, oocyte cryotolerance is not improved. Notably, the expression of genes associated with the unfolded protein response (UPR) was increased in COCs, with fewer lipid droplets subjected to vitrification, suggesting that oocyte cryopreservation is associated with ER stress and activation of adaptive responses.

Supplementing in vitro embryo production media by NPPC and sildenafil affect the cytoplasmic lipid content and gene expression of bovine cumulus-oocyte complexes and embryos

In our study, we added natriuretic peptide type C (NPPC) and/or sildenafil during in vitro maturation (IVM) of bovine cumulus-oocyte complexes (COCs) followed by in vitro culture (IVC) of embryos with or without sildenafil. We evaluated the effects on the lipid content (LC) of oocytes and embryos and also verified the expression of 96 transcripts related to competence in matured COCs and 96 transcripts related to embryo quality in blastocysts. After IVM, LC was decreased in oocytes by NPPC while sildenafil did not affect LC in oocytes. The genes involved in lipid metabolism and lipid accumulation (DGAT1, PLIN2and PLIN3) were not affected in COCs after treatment during IVM, although the expression of PTX3 (a cumulus cells expansion biomarker) was increased and the hatched blastocyst rate was increased by NPPC during IVM. During IVM, sildenafil increased the mRNA relative abundance of HSF1 and PAF1 and decreased REST in blastocysts. The use of sildenafil in IVC increased the LC of blastocysts. The mRNA abundance in blastocysts produced during IVC with sildenafil was changed for ATF4, XBP1, DNMT3A, DNMT3B, COX2, and SOX2. Although NPPC reduced the LC of oocytes after IVM and upregulated markers for cumulus expansion, embryo production was not affected and the produced blastocysts were able to regain their LC after IVC. Finally, the use of sildenafil during IVC increased the cytoplasmic LC of embryos but did not affect embryo quality, as measured by analysis of 96 transcripts related to embryo quality.

The role of cGMP as a mediator of lipolysis in bovine oocytes and its effects on embryo development and cryopreservation

This study aimed to determine the influence of cyclic guanosine 3’5’-monophosphate (cGMP) and cGMP-dependent kinase (PKG) during in vitro maturation (IVM) on lipolysis-related parameters in bovine cumulus-oocyte complexes (COCs), and on embryo development and cryosurvival. COCs were matured with cGMP/PKG modulators and assessed for metaphase II rates (MII), cGMP levels, lipid content in oocytes (OO), transcript abundance for genes involved in lipolysis (ATGL) and lipid droplets (PLIN2) in cumulus cells (CC) and OO, and presence of phosphorylated (active) hormone sensitive lipase (HSL^ser563) in OO. Embryo development, lipid contents and survival to vitrification were also assessed. Phosphodiesterase 5 inhibition (PDE5; cGMP-hydrolyzing enzyme) with 10^-5M sildenafil (SDF) during 24 h IVM increased cGMP in COCs (56.9 vs 9.5 fMol/COC in untreated controls, p<0.05) and did not affect on maturation rate (84.3±6.4% MII). Fetal calf serum (FCS) in IVM medium decreased cGMP in COCs compared to bovine serum albumin (BSA) + SDF (19.6 vs 66.5 fMol/COC, respectively, p<0.05). FCS increased lipid content in OO (40.1 FI, p<0.05) compared to BSA (34.6 FI), while SDF decreased (29.8 and 29.6 FI, with BSA or FCS, respectively p<0.05). PKG inhibitor (KT5823) reversed this effect (38.9 FI, p<0.05). ATGL and PLIN2 transcripts were detected in CC and OO, but were affected by cGMP and PKG only in CC. HSL^ser563 was detected in OO matured with or without modulators. Reduced lipid content in embryos were observed only when SDF was added during IVM and IVC (27.6 FI) compared to its use in either or none of the culture periods (34.2 FI, p<0.05). Survival to vitrification was unaffected by SDF. In conclusion, cGMP and PKG are involved in lipolysis in OO and possibly in CC and embryos; serum negatively affects this pathway, contributing to lipid accumulation, and cGMP modulation may reduce lipid contents in oocytes and embryos, but without improving embryo cryotolerance.

Ovine Granulosa Cells Isolation and Culture to Improve Oocyte Quality

The functional cooperation between the oocyte and its surrounding granulosa cells is mandatory to oocyte growth and acquisition of developmental competence in mammalian species. Availability of in vitro methods for culture granulosa cells is important in understanding the biology of these cells and the response of maturing oocyte to in vitro culture and co-culture. Using the ovine as a model the ensuing chapter describes methods for primary culture of ovine granulosa cells and their co-culture with theca cells or oocytes that allow to mimic the molecular interactions between somatic cells and maturing oocyte and improve oocyte quality.

Production of live larvae following in vitro maturation of zebrafish oocytes

This study aimed to assess the effects of carp pituitary extract (CPE), follicle stimulating hormone (FSH) and luteinizing hormone (LH) on zebrafish oocyte maturation and the ability of these mature oocytes to be fertilized and developed until hatching. Stage III follicles were matured in eight treatments: five concentrations of CPE (16, 32, 48, 64 and 80 μg/mL), one of FSH (0.5 μg/mL), one of LH (0.5 μg/mL), or one combination of FSH (0.5 μg/mL) and LH (0.5 μg/mL). Maturation rates in CPE treatments were 12.8% (16 μg/mL), 24.8% (32 μg/mL), 27.0% (48 μg/mL), 22.7% (64 μg/mL) and 9.6% (80 μg/mL); in FSH was 15.7% (0.5 μg/mL), in LH was 31.8% (0.5 μg/mL) and in FSH (0.5 μg/mL) combined with LH (0.5 μg/mL) it was 50.4%. In vitro fertilization was performed in all treatments; however, only the treatment combining FSH and LH resulted in fertilized oocytes. After maturation using FSH combined with LH, the cleavage rate was 33.3% and hatching rate of live larvae was 20.0%. These results showed that FSH combined with LH was effective in IVM of zebrafish oocyte.

Delaying meiotic resumption during transportation of bovine cumulus–oocyte complexes: effects on development, apoptosis and caspases activity of in vitro-produced embryos

This study examined the effects of meiosis inhibition during bovine oocyte transportation on developmental competence and quality of produced embryos. The transportation medium was supplemented with: 100 μM butyrolactone I (BL), 500 μM IBMX + 100 μM forskolin (mSPOM), 100 μM milrinone (MR) or follicular fluid (bFF), and was carried out in a portable incubator for 6 h. Next, oocytes were in vitro matured (IVM) for 18 h, without the meiotic inhibitors, with the exception of mSPOM group, in which was added 20 μM cilostamide. The three control groups were IVM with 10% fetal calf serum (FCS) (Control Lab FCS) or 0.6% bovine serum albumin (BSA) (Control Lab BSA) in a CO2 in air incubator or in the portable incubator with 0.6% BSA (Control Transp BSA). Higher cleavage rates (P < 0.05) were obtained in the Control Lab FCS group (84.5 ± 5.3%) compared with the other groups (59.6 ± 3.4% to 70.9 ± 2.3%). Embryonic development was higher (P < 0.05) in the Control Lab FCS group (39.8 ± 4.7%) than in the Control Transp BSA (22.7 ± 3.4%) and MR (21.6 ± 2.3%) groups. However, they were similar (P > 0.05) to the other groups (23.6 ± 3.3% to 28.8 ± 2.7%). The total number of blastomeres was higher (P < 0.05) in the Control Lab FCS group (85.2 ± 5.6) than in Control Lab BSA (53.6 ± 2.9), Control Transp BSA (55.5 ± 4.4), BL (58.2 ± 3.0), mSPOM (57.9 ± 4.9) and MR (59.2 ± 3.9), but all these treatments did not differ (P > 0.05) from bFF (67.7 ± 4.2). No differences (P > 0.05) were found in apoptosis by the activity of caspases (139.0 ± 3.2 to 152.4 ± 6.5, expressed in fluorescence intensity) as well as the percentage of TUNEL-positive cells (12.3 ± 2.0% to 15.7 ± 1.7%). In conclusion, the transportation of oocytes over 6 h with BL, mSPOM or bFF enabled the acquisition of developmental competence at similar rates to the Control Lab FCS group.