Role of protein supplements in the culture of mouse embryos

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.

Lambing rate using vitrified blastocysts is improved by culture with BSA and hyaluronan

Fatty acid-free bovine serum albumin (BSA(FAF)) can be added to supplement medium used in the culture of sheep embryos. BSA(FAF) was able to support blastocyst and subsequent embryo development at rates equivalent to that of fetal calf serum (FCS)-supplemented medium when fresh embryos were transferred. Furthermore, culture with BSA(FAF) significantly increased development of vitrified blastocysts transferred into synchronized sheep. The addition of the glycosaminoglycan, hyaluronan (HA) to the culture medium in the third and fifth day also increased cryo-tolerance of blastocysts and in turn lambing rate was improved.

Effect of the absence or presence of various protein supplements on further development of bovine oocytes during in vitro maturation

The evaluation of culture medium for bovine oocytes has progressed toward more defined conditions during the last few years. The main objective of this study was to evaluate different sources of albumin as a protein supplement during in vitro maturation (IVM) of bovine oocytes in synthetic oviduct fluid medium (SOF). The replacement of protein with polyvinyl pyrrolidone (PVP) or polyvinyl alcohol (PVA) was also evaluated. The effect of recombinant human FSH on cumulus expansion and nuclear maturation in SOF containing BSA (BSA-V) or PVP-40 was also studied. Addition of BSA-V during IVM retarded nuclear maturation when compared with addition of PVP-40 or use of SOF alone. The inclusion of different concentrations of BSA-V, fetal calf serum (FCS), or PVA during IVM had no positive effect on the developmental capacity of the oocytes compared with the use of SOF alone with no supplement but significantly decreased the percentage of embryos reaching the morula and blastocyst stages. However, when BSA-V was replaced with purified BSA, BSA that was essentially free of fatty acids, or chicken egg albumin, embryonic development rates were restored. The presence of PVP-40 but not PVP-360 during IVM significantly increased morula and blastocyst production. These results indicate that although SOF alone can support bovine oocyte maturation, a high proportion of morulae and blastocysts can be produced from IVM oocytes cultured in medium containing PVP-40. These studies are the first to show that the effect of FSH on nuclear maturation and cumulus expansion is dependent on substrates present in IVM medium.

Potent and stage-specific action of glutathione on the development of goat early embryos in vitro

The effect of glutathione (GSH) addition on the development of 1- or 2-cell goat early embryos in vitro was examined. Embryos were collected from superovulated Korean black goat (Capra hircus aegagrus) and cultured for 6 days in synthetic oviduct fluid medium supplemented with either bovine serum albumin (BSA) or serum. Without GSH addition, almost all embryos could not develop beyond 8- to 16-cell block. However, GSH addition greatly improved in vitro development of early embryos to blastocyst stage, and its action was highly dependent on the presence and source of proteins supplemented into the culture medium. Among the protein-supplemented cultures, GSH effect was most prominent in 10% FBS-supplemented culture, in which the proportion (91%) of blastocysts developed from early embryos was much higher than that of BSA- (42-64% depending on its content) or goat serum (GS)-supplemented cultures (21%), or even than that of somatic cell-supported co-culture (60%). As well as in terms of the morphological development, mean cell number of blastocysts (185 +/- 12) developed from FBS condition was significantly higher than that of blastocysts developed from any other culture conditions and moreover comparable to that of blastocysts developed in vivo (190 +/- 9). The viability of these blastocysts was finally confirmed by their term development (6/12) from embryo transfer. To delineate action time of GSH during embryo development, GSH was treated at 1-day intervals through 6-days culture periods excepting the last day. In the GSH-treated embryos at day 3 of culture, which corresponds to the time of in vitro 8- to 16-cell block stage, the proportion of blastocyst was markedly increased up to 77% of cultured embryos and conversely that of the arrested embryos was decreased to 7%. In the embryos treated later, however, their developmental potency decreased abruptly. Therefore, these results clearly demonstrated that GSH could greatly improve the in vitro development of goat early embryos by specifically acting on the 8- to 16-cell block stage during in vitro development, suggesting that GSH may be one of the important regulators on the development of goat embryos in vivo.

The effect of melatonin on in vitro fertilization and embryo development in mice

To examine the effect of melatonin on in vitro fertilization and embryonic development, mouse embryos after insemination in vitro were cultured in a physiological medium with or without melatonin. Melatonin increased the fertilization rate significantly at a concentration between 10(-6) and 10(-4) M (27.6 vs. 43.9 or 40.4%, P < 0.01). Furthermore, a significant increase in the rate of embryos reaching the four-cell stage (16.0 vs. 26.7%, P < 0.01), the eight-cell stage (12.1 vs. 25.8 or 23.5%, P < 0.01), and blastulation (8.9 vs. 23.5 or 17.5%, P < 0.01) was observed when the embryos were cultured in a medium containing 10(-8) or 10(-6) M melatonin. These results demonstrate that melatonin supports fertilization and early embryo development after in vitro fertilization.

Promotion of development of bovine embryos produced in vitro by addition of cysteine and beta-mercaptoethanol to a chemically defined culture system

The aim of this research was to determine the effects of L-cysteine and beta-mercaptoethanol on the in vitro development of bovine embryos that had been produced in vitro. A 2 x 3 factorial arrangement of treatments was used to evaluate the effect of 0.63 or 6.9 microM L-cysteine and 0, 10, or 100 microM beta-mercaptoethanol on the development of bovine embryos in a chemically defined medium. Embryos containing 6 to 8 cells were randomly allocated to one of the six treatment combinations and were cultured for 7 d. Both beta-mercaptoethanol and L-cysteine increased the number of embryos that reached the blastocyst stage of development, although no interaction was observed between the compounds. Embryos that were cultured in the presence of beta-mercaptoethanol had more cells at the blastocyst stage than did embryos cultured in medium without beta-mercaptoethanol. These findings provide evidence that beta-mercaptoethanol and L-cysteine promote increased embryonic development and that beta-mercaptoethanol increases the number of cells in bovine embryos produced in vitro and cultured in a cell-free, protein-free culture system.

Improvement in bovine embryo production in vitro by glutathione-containing culture media

Bovine oocytes were matured, fertilized, and cultured (TCM 199 with serum and co-culture) in vitro (IVMFC) with addition, during different phases of the procedure, of antioxidants: superoxide dismutase (SOD) and reduced glutathione (GSH). The addition of SOD (1,500 or 3,000 IU/ml) did not improve proportions of oocytes undergoing cleavage or the development of embryos to morula and blastocyst stages. The cleavage rates were significantly lower than in the control group (CTR 57.5%) when SOD was present during the insemination interval (IVF) or throughout the entire procedure (IVMFC). Thus when the lower concentration was present for IVF and IVMFC, 35.1% and 36.4% of inseminated oocytes cleaved (P < 0.01 compared to CTR) and cleavage results with the higher concentration during IVF and IVMFC were 38.5% and 29.2% (P < 0.025 and P < 0.001 compared to CTR, respectively). Significant improvements in proportions of oocytes undergoing cleavage (84.5% vs. 57.0%, P < 0.001) and morula/blastocyst development (33.3% vs. 13.9%, P < 0.005) were achieved when GSH (1 mM) was added to the culture medium. In a defined medium for culture (mSOF and BSA) the presence of SOD (3,000 IU/ml) was ineffective, but in a defined medium supplemented with GSH (1 mM) at day 6 postinsemination (i.e., when 90% of developing embryos were in 8-16 cell stages), development to the morula and blastocyst stages was supported for 35.5% of cultured oocytes (P < 0.005 compared to 19.2% for CTR). These data suggest that bovine embryos are sensitive to oxidative stress and that medium supplementation with the radical scavenger glutathione can improve embryo development in vitro.