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.

Cellular and apoptotic status monitoring according to the ability and speed to resume post-cryopreservation embryonic development.

Embryonic morphofunctional competence features regulating post-cryopreservation resumption of development are still poorly understood. In this study, we investigated the correlation between embryonic viability and the speed and ability to resume post-cryopreservation development. Thus, in vitro produced blastocysts were vitrified by the Cryotop method using standard protocols. Subsequently, the embryos were warmed, re-cultured, and classified into groups according to their speed and ability to resume post-cryopreservation development: embryos not re-expanded at 12h (NE12); embryos re-expanded at 12h and hatched at 24h (E12H24); embryos re-expanded at 12h and hatched at 48h (E12H48); embryos re-expanded at 12h and not hatched at 48h (E12NH48). Subsequently, the embryos were subjected to monitoring of total cell number and apoptosis. We identified that the blastocoel's ability to re-expand was negatively affected by the significant higher percentage of apoptotic cells observed in the NE12 group than in the other groups. A greater (P < 0.05) number of total cells, found in groups E12H24 and E12H48, seems to have a positive influence on the hatching capacity of blastocysts after cryopreservation. In conclusion, the total number of cells and apoptotic index correlated with the speed and ability to resume post-cryopreservation development. Apoptosis was a determinant for embryonic re-expansion, and the total cell number was crucial for blastocyst hatching.

Effects of the addition of oocyte meiosis-inhibiting drugs on the expression of maturation-promoting factor components and organization of cytoplasmic organelles.

The present study evaluated the effects of the blockade of meiosis in bovine oocytes by the cyclin-dependent kinase inhibitors roscovitine (ROS) and butyrolactone-I (BL-I) on nuclear maturation and extracellular signal-regulated kinase 1/2 (ERK1/2), cyclin B1 and p34cdc2 protein expression and localization. We also evaluated ultrastructural changes in oocytes. Immature oocytes were obtained from slaughtered bovines and divided into: (1) control (oocytes for in vitro maturation only in tissue culture medium-199 for 24 h), (2) oocytes that were treated with 12.5µMROS for 6 h, (3) oocytes that were treated with 50µMBL-I for 6 h and (4) oocytes that were treated with 6.25 µMROS+25 µMBL-I for 6 h. Incubation with inhibitors was followed by the reversal of blockade for 18 h. Oocytes then underwent immunohistochemical analysis to visualize chromatin and assess ERK1/2, cyclin B1 and p34cdc2 localization/expression, followed by preparation of the cells for ultrastructure analysis by electron microscopy. The groups at 6 h of maturation and before IVM exhibited the lowest number of oocytes in metaphase I. ROS group had the highest number of degenerating oocytes (p < 0.05). After maturation, majority of oocytes were in metaphaseII with no differences among groups (p> 0.05). ERK1/2, cyclin B1 and p34cdc2 expression differed throughout inhibition and oocyte maturation (p < 0.05). No difference was observed in the localization of these proteins in the ooplasm. No ultrastructural changes in oocytes were observed between treatments, with the exception of treatment with drugs that augmented lipid metabolism (p < 0.05). Results indicate that the effects of CDK1 inhibitors are reversible in bovine oocytes, indicated by nuclear, cytoplasmic, and molecular maturation parameters.

Treatment with roscovitine and butyrolactone I prior to in vitro maturation alters blastocyst production.

This study evaluated the effects of oocyte meiosis inhibitors roscovitine (ROS) and butyrolactone I (BL-I) on in vitro production of bovine embryos. Bovine oocytes were maintained in pre in vitro maturation (pre-IVM) with 25 µM ROS or 100 µM BL-I for 24 h to delay meiosis and for 24 h in in vitro maturation (IVM). Following this treatment, the nuclear maturation index was evaluated. All embryos degenerated following this procedure. In the second set of experiments, oocytes were maintained for 6 or 12 h in pre-IVM with the following three treatments: ROS (25 µM or 12.5 µM), BL-I (100 µM or 50 µM) or a combination of both drugs (6.25 µM ROS and 12.5 µM BL-I). Oocytes were cultivated for 18 or 12 h in IVM. When a meiosis-inducing agent was used during pre-IVM for 24 h, more degenerated oocytes were observed at the end of the IVM period. This effect decreased when the meiotic blocking period was reduced to 6 or 12 h. No significant differences were observed in the blastocyst production rate of oocytes in pre-IVM for 6 h with ROS, BL-I, or ROS + BL-I compared with that of the control group (P > 0.05). However, inhibition of oocytes for 12 h resulted in decreased embryo production compared with that in the controls (P < 0.05). There was no difference in the post-vitrification embryo re-expansion rate between the study groups, showing that the meiotic inhibition for 6 or 12 h did not alter the embryo cryopreservation process.

Cell apoptosis and lipid content of in vitro-produced, vitrified bovine embryos treated with forskolin.

The presence of fetal calf serum in culture medium influences embryo quality, causing a reduction in postcryopreservation survival. Forskolin has been used to induce lipolysis and increase cryotolerance, functioning as an activator of adenylate cyclase and elevating cAMP levels. In the present experiment, bovine zygotes were cultured in synthetic oviduct fluid with amino acid plus 2.5% fetal calf serum for 6 days, when forskolin was added in three concentrations: 2.5, 5, and 10 µM. Treatment with forskolin lasted for 24 hours. Blastocyst formation rate, quantification of lipid granules, total cell numbers, and apoptosis rate were evaluated. In a second assessment, embryos were vitrified, and warming, re-expansion rate, total cell numbers, and apoptosis rate were also evaluated. There was no difference due to forskolin in blastocyst formation or re-expansion rates after vitrification. However, lipid measurements were lower (control: 136.8 and F 2.5 µM: 128.5; P < 0.05), and number of cells per embryo higher (control: 140.1 and F 2.5 µM: 173.5; P < 0.05) than controls for 2.5 µM forskolin but not for higher forskolin concentrations. The number of intact cells per embryo was higher, and the rate of apoptosis was lower in fresh than in vitrified embryos (number of cells of warmed embryos, control: 104.1, F 2.5 µM: 101.3, F 5 µM: 115.4, F 10 µM: 95.1; apoptotic of fresh cells, control: 12.1%, F 2.5 µM: 16.7%, F 5 µM: 11.1%, F 10 µM: 14.2%; and apoptotic warmed embryos, control: 22.3%, F 2.5 µM: 37.3%, F 5 µM: 33.2%, F 10 µM: 30.3%; P < 0.05). It was concluded that forskolin is an effective lipolytic agent even at low concentrations, leading to formation of blastocysts with a comparatively larger number of cells.

In vitro embryos production after oocytes treatment with forskolin.

The inhibition of nuclear maturation allows time for the oocyte to accumulate molecules that are important for embryonic development. Thus, the objective of this work was to evaluate the effect of blocking oocyte meiosis with the addition of forskolin, an efficient inhibitor of nuclear maturation, in in vitro maturation (IVM) medium. Forskolin was added to the IVM medium for 6 h at concentrations of 0.1 mM, 0.05 mM or 0.025 mM, then the oocytes were allowed to mature in drug-free medium for 18 h. The oocytes were assessed for the stage of nuclear maturation, the activity and distribution of mitochondria, oocyte ultrastructure, the number of viable cells and the apoptosis rate. After forskolin treatment, the oocytes were fertilized in vitro and cultured for 7 days. On day 7, the blastocyst rate, the ultrastructure, the number of intact cells and the apoptosis rate of the blastocysts were measured. No differences were observed for the stage of nuclear maturation of the oocyte, the mitochondrial activity and distribution, the blastocyst rate or total number of intact cells. However, a higher rate of apoptosis was observed in the blastocysts produced from oocytes blocked for 6 h with the higher concentration of forskolin (P < 0.05). We conclude that all the experimental groups reached the MII stage after the addition of forskolin and that the highest concentration of forskolin caused cellular degeneration without harming embryo production on the 7th day.

Time course of the meiotic arrest in sheep cumulus-oocyte complexes treated with roscovitine.

Temporary meiosis arrest with cyclin-dependent kinases inhibitors has been proposed in order to improve the quality of in vitro matured oocytes. In sheep, however, this phenomenon has been rarely investigated. Therefore, the present study aimed to evaluate the effect of different incubation times with roscovitine on nuclear maturation and cumulus cell expansion of sheep cumulus-oocyte complexes (COCs). For this, COCs were cultured for 0, 6, 12 or 20 h in basic maturation medium (Control) containing 75 µM roscovitine (Rosco). After, they were in vitro matured (IVM) for 18 h in the presence of luteinizing hormone (LH) and follicle-stimulating hormone (FSH). At the end of each treatment, cumulus cell expansion and nuclear maturation were assessed under a stereomicroscope and by Hoechst 33342 staining, respectively. In the Control and Rosco groups, the absence of cumulus cell expansion prevailed at 0, 6, 12 and 20 h. After IVM for 18 h, total cumulus cell expansion in the Rosco treatments was dependent on the exposure time to roscovitine. A significantly high percentage of oocytes treated with roscovitine for 6 h (87%), 12 h or 20 h (65%) were arrested at the germinal vesicle (GV) stage. In contrast, 23% GVBD, 54% metaphase I (MI) and 61% MII oocytes were observed in the Control groups at 6, 12 and 20 h, respectively. In all treatments, a significant percentage of oocytes reached MII after IVM for 18 h. Therefore, roscovitine reversibly arrested the meiosis of sheep oocytes during different culture times with the maximal efficiency of meiotic inhibition reached at 6 h. In addition, reversibility of its inhibitory action on cumulus cells was exposure-time dependent.

Crucial surviving aspects for vitrified in vitro-produced bovine embryos.

The objective of the present study was to correlate some parameters (cleavage, blastocyst production, quality degree score, total cell number, fresh apoptosis and lipid content) with embryo survival after cryopreservation. A total of 1727 in vitro-produced bovine blastocysts were used to establish the parameters (mean ± standard error of the mean (SEM)) for cleavage (85.6 ± 0.8), blastocyst production (39.9 ± 1.4), quality degree score (1.6 ± 0.1), total cell number (140.1 ± 2.9), fresh apoptosis (20.8 ± 1.1) and lipid content (21.3 ± 0.8 droplets). On the same way 1316 blastocysts were vitrified for the determination of post-cryopreservation embryo survival (49.4 ± 1.9). Fresh apoptosis rate and total lipid droplets value were correlated (P < 0.05) with embryo survival after cryopreservation (r = 0.91 and r = 0.59; respectively). However, cleavage, blastocyst production, quality degree score and total cell number were not correlated (P > 0.05) with embryo cryotolerance (r = 0.23, r = 0.38, r = 0.22 and r = 0.28; respectively). Therefore, the increased lipid content was moderately correlated with apoptosis in vitrified blastocysts. On the other hand, increased apoptosis in fresh blastocysts was strongly correlated with apoptosis in vitrified blastocysts, which indicated that the apoptosis rate in fresh embryos was a better parameter than the lipid content to predict post-vitrification embryo survival.

Forskolin effect on the cryosurvival of in vitro-produced bovine embryos in the presence or absence of fetal calf serum.

The objective of this study was to assess the viability and cryotolerance of zebu embryos produced in vitro with or without the addition of fetal calf serum (FCS) and forskolin (F). Embryos produced in vivo were used as a control. Presumptive zygotes were cultured in modified synthetic oviductal fluid supplemented with amino acids (SOFaa), bovine serum albumin (BSA) and with (2.5%) or without (0%) FCS. On day 6 of growth, the embryos from each group were divided into treatments with or without 10 µM F to induce embryonic lipolysis, comprising a total of four experimental groups: 2.5% FCS, 0% FCS, 2.5% + F and 0% + F. For vitrification, embryos were exposed to vitrification solution 1 (5 M EG (ethylene glycol)) for 3 min and then transferred to vitrification solution 2 (7 M EG, 0.5 M galactose solution and 18% (w/v) Ficoll 70) before being introduced to liquid nitrogen. The presence of FCS in the culture medium resulted in the production of embryos with a similar rate of damaged cells compared with in vivo-produced embryos. After vitrification, the 2.5% FCS group had a significantly higher rate of damaged cells when compared with the other groups (P < 0.05). The results of this experiment indicated that the omission of FCS and the addition of forskolin do not have deleterious effect on embryo production rates. In addition, embryos produced in the presence of FCS had greater sensitivity to cryopreservation, but this effect was reversed when forskolin was added to the medium, which improved embryo survival without affecting embryo development and quality after vitrification.

Influence of culture medium and age of bovine blastocysts in established colonies of embryonic stem cells.

The objective of this study was to evaluate the potential of bovine IVF blastocysts at different stages of embryonic development in establishing ESC-like. Furthermore, blastocysts cultured in medium containing (10%) and (2.5%) fetal calf serum (FCS) were compared to determine if the serum concentration during in vitro culture alters the blastocyst's potential to establish ESC-like culture. It was observed that only ICM's from expanded blastocysts adhered to the monolayer (n=160) independent of the concentration of serum used during IVF culture. There were no observable differences in potential to establish ESC-like in embryos cultured with 2,5% or 10% FCS . The bFGF didn´t seems to be required for maintenance of bovine ESC-like regardless of culture conditions. Blastocysts and colonies in primary culture and after the first passage were positive for Oct4, Nanog, SSEA-3 and TRA-1-81. Expanded blastocysts gave rise to ESC-like colonies, and the addition of LIF was sufficient to maintain cells undifferentiated in culture.

Lipid content and apoptosis of in vitro-produced bovine embryos as determinants of susceptibility to vitrification.

UNLABELLED: The objective was to evaluate supplementation of fetal calf serum (FCS) and phenazine ethosulfate (PES), a metabolic regulator that inhibits fatty acid synthesis, in culture media during in vitro production (IVP) of bovine embryos. Taking oocyte fertilization (n = 4,320) as Day 0, four concentrations of FCS (0, 2.5, 5, and 10%) and three periods of exposure to PES (without addition-CONTROL; after 60 h-PES Day 2.5 of embryo culture; and after 96 h-PES Day 4) were evaluated. Increasing FCS concentration in the culture media enhanced lipid accumulation (P < 0.05), increased apoptosis in fresh (2.5%: 19.1 ± 1.8 vs 10%: 28.4 ± 2.3, P < 0.05; mean ± SEM) and vitrified (2.5%: 42.8 ± 2.7 vs 10%: 69.2 ± 3.4, P < 0.05) blastocysts, and reduced blastocoele re-expansion after vitrification (2.5%: 81.6 ± 2.5 vs 10%: 67.3 ± 3.5, P < 0.05). The addition of PES in culture media, either from Days 2.5 or 4, reduced lipid accumulation (P < 0.05) and increased blastocoele re-expansion after vitrification ( CONTROL: 72.0 ± 3.0 vs PES Day 2.5: 79.9 ± 2.8 or PES Day 4: 86.2 ± 2.4, P < 0.05). However, just the use of PES from D4 reduced apoptosis in vitrified blastocysts ( CONTROL: 52.0 ± 3.0 vs PES Day 4: 39.2 ± 2.4, P < 0.05). Independent of FCS withdrawal or PES addition to culture media, the in vivo control group had lesser lipid accumulation, a lower apoptosis rate, and greater cryotolerance (P < 0.05). The increased lipid content was moderately correlated with apoptosis in vitrified blastocysts (r = 0.64, P = 0.01). In contrast, the increased apoptosis in fresh blastocysts was strongly correlated with apoptosis in vitrified blastocysts (r = 0.94, P < 0.0001). Therefore, using only 2.5% FCS and the addition of PES from Day 4, increased the survival of IVP embryos after vitrification. Moreover, embryo quality, represented by the fresh apoptosis rate, was better than lipid content for predicting embryo survival after vitrification.