Protection of porcine oocytes against cell damage caused by oxidative stress during in vitro maturation: role of superoxide dismutase activity in porcine follicular fluid

The evolution of porcine embryo in vitro production

The in vitro production of porcine embryos has presented numerous challenges to researchers over the past four decades. Some of the problems encountered were specific to porcine gametes and embryos and needed the concerted efforts of many to overcome. Gradually, porcine embryo in vitro production systems became more reliable and acceptable rates of blastocyst formation were achieved. Despite the significant improvements, the problem of polyspermic fertilization has still not been adequately resolved and the embryo in vitro culture conditions are still considered to be suboptimal. Whereas early studies focused on increasing our understanding of the reproductive processes involved, the technology evolved to the point where in vitro-matured oocytes and in vitro-produced embryos could be used as research material for developing associated reproductive technologies, such as SCNT and embryo cryopreservation. Today, the in vitro procedures used to mature oocytes and culture embryos are integral to the production of transgenic pigs by SCNT. This review discusses the major achievements, advances, and knowledge gained from porcine embryo in vitro production studies and highlights the future research perspectives of this important technology.

Oral antioxidants supplementation for women with unexplained infertility undergoing ICSI/IVF: randomized controlled trial

OBJECTIVE

Good oocyte quality and maturity are important prerequisites for high fertilization and implantation rates in IVF/ICSI treatment cycles. Reactive oxygen species (ROS) are produced within ovarian follicles, especially during the ovulation process, and increased ROS activity may be a cause of impaired oocyte maturation and higher rate of failure of IVF/ICSI cycles.

STUDY DESIGN

RCT evaluating the effect of antioxidant supplementation on ICSI/IVF outcomes. Two hundred and eighteen women with unexplained subfertility undergoing IVF/ICSI were randomized into two groups. The study group (n = 112) received daily oral antioxidants in the form of multivitamins and minerals (amino acid chelated) while the control group (n = 106) did not. Main outcomes were number of mature metaphase II (MII) oocytes and clinical pregnancy rate.

RESULTS

There were no significant changes between the groups as regards age, BMI, basal FSH, number of mature (MII) oocytes (12.7 ± 9.4 vs. 13.2 ± 8.6, P = 0.7) and clinical pregnancy rate per woman randomized (38% vs. 34%; [OR = 1.2; 95% CI, 0.70-2.11].

CONCLUSION

Oral antioxidants in the form of a combination of multivitamins and minerals (amino acid chelated) did not improve oocyte quality and pregnancy rates in women with unexplained infertility undergoing IVF/ICSI treatment.

Effect of bovine follicular fluid on reactive oxygen species and glutathione in oocytes, apoptosis and apoptosis-related gene expression of in vitro-produced blastocysts

The reactive oxygen species (ROS) generated during the in vitro maturation of oocytes affect oocyte maturation and subsequent embryonic development. Bovine follicular fluid (bFF) has an effective antioxidant capacity. This study was conducted to investigate the effects of supplementing oocyte maturation media with bFF from different size classes (3-8 and 9-13 mm) on the glutathione (GSH) and ROS levels of oocytes. Embryonic development and apoptosis, as well as the relative abundance of INFτ, BAX, BCL2 and HSP70 transcripts in blastocysts, were also monitored. Oocytes collected from ovaries were matured in TCM-199 with FBS (control) and 10% 3-8 mm (M), 9-13 mm (L) or a mixture of 3-8 mm and 9-13 mm (M + L) bFF. Glutathione and ROS levels in oocytes after 24 h were assessed by Cell Tracker Blue CMF2HC and DCHFDA staining, respectively. Apoptosis in day-8 blastocysts was assessed by TUNEL staining. The relative abundance of BAX, BCL2, HSP70 and INFτ transcripts was assessed using quantitative real-time polymerase chain reaction (PCR). The GSH level was significantly higher in the L group compared to the other groups (p < 0.05), while the ROS levels in the M group were significantly higher than in the other groups (p < 0.05). The apoptosis levels of blastocysts in the FBS group were significantly higher than those in the M + L group (p < 0.05), although the embryonic development did not differ between the groups. The HSP70 and INFτ expression levels in group M were significantly greater than in the controls (p < 0.05). There was no significant difference in BAX expression between the groups. Supplementation with bFF from various sizes of follicles into the maturation medium was capable of supporting oocyte cytoplasmic maturation by decreasing the ROS. Moreover, bFF subsequently affected antioxidative gene expression, increasing HSP70 and INFτ expressions.

Clinical relevance of melatonin in ovarian and placental physiology: a review

Within the last decade, the synthesis of melatonin in and its functions at the level of the peripheral reproductive organs has come into better focus. Melatonin is produced at several reproductive organ sites, e.g., the oocyte, ovarian follicular cells and the placental cytotrophoblasts. Moreover, these cells also contain membrane receptors for this indoleamine. In addition, via the free radical scavenging activity of melatonin and its metabolites, oxidative stress is reduced in all reproductive organ cells ensuring their optimal function. Enhancement of oocyte maturation and preservation of oocyte quality may be major functions of melatonin. Oocyte damage reduces successful fertilization and the development of a healthy fetus. The findings that melatonin protects the oocyte from toxic oxygen species have implications for improving the outcome of in vitro fertilization-embryo transfer procedures, as already shown in two published reports. Some actions of melatonin in the placenta may be context specific. Thus, melatonin is believed to function in the maintenance of optimal placental homeostasis by deferring apoptosis of villous cytotrophoblasts, while protecting syncytiotrophoblasts from oxidative damage. Melatonin reduces oxidative damage in the placenta and may improve hemodynamics and nutrient transfer at the placental-uterine interface. The use of melatonin to treat preeclampsia should also be considered.

Supplementation of culture medium with L-carnitine improves development and cryotolerance of bovine embryos produced in vitro

High lipid content in embryos is associated with low freezing tolerance. This study assessed the effects of exogenous L-carnitine, an enhancer of lipid metabolism, on the in vitro development and freezing survival of bovine embryos. Also, effects on metabolic activity, reactive oxygen species (ROS) and apoptosis were investigated. Supplementation of embryo culture medium with 1.518 mM or 3.030 mM L-carnitine significantly increased the rates of zygote development to the blastocyst stage and blastocyst cell numbers whereas 6.072 mM of this compound did not improve embryo development. Survival rates after slow freezing of blastocysts were significantly higher when embryos were cultured in the presence of 1.518 mM or 3.030 mM L-carnitine compared with the control. A lower density of lipid droplets was detected in L-carnitine-treated blastocysts compared with the control. L-carnitine significantly reduced ROS levels in 2-cell embryos but did not reduce ROS levels at later stages. The apoptotic cell rate was not different between control and L-carnitine-treated blastocysts. L-carnitine significantly increased ATP levels in 2-cell embryos but not at the 8-cell or blastocyst stages. L-carnitine increased the expression of metabolism-related ATP6 and COX1 genes in blastocysts. In conclusion, L-carnitine supplementation enhanced lipid metabolism in embryos resulting in improved development and cryotolerance of bovine blastocysts produced in vitro.

Effects of resveratrol on vitrified porcine oocytes

Vitrified MII porcine oocytes are characterized by reduced developmental competence, associated with the activation of the apoptotic pathway. Resveratrol (R), a polyphenolic compound present in several vegetal sources, has been reported to exert, among all its other biological effects, an antiapoptotic one. The aim of this study was to determine the effects of R (2  µM) on the apoptotic status of porcine oocytes vitrified by Cryotop method, evaluating phosphatidylserine (PS) exteriorization and caspases activation. R was added during IVM (A); 2 h postwarming incubation (B); vitrification/warming and 2 h postwarming incubation (C); all previous phases (D). Data on PS exteriorization showed, in each treated group, a significantly higher (P < 0.05) percentage of live nonapoptotic oocytes as compared with CTR; moreover, the percentage of live apoptotic oocytes was significantly (P < 0.05) lower in all R-treated groups relative to CTR. The results on caspase activation showed a tendency to an increase of viable oocytes with inactive caspases in B, C, and D, while a significant (P < 0.05) increase in A compared to CTR was recorded. These data demonstrate that R supplementation in various phases of IVM and vitrification/warming procedure can modulate the apoptotic process, improving the resistance of porcine oocytes to cryopreservation-induced damage.

Melatonin as a free radical scavenger in the ovarian follicle

This review summarizes new findings related to beneficial effects of melatonin (N-acetyl-5-methoxytryptamine) on reproductive physiology. Recently many researchers have begun to study the local role of melatonin as an antioxidant. We focused on intra-follicular role of melatonin in the ovary. Melatonin, secreted by the pineal gland, is taken up into the follicular fluid from the blood. Reactive oxygen species (ROS) are produced within the follicles, during the ovulatory process. Melatonin reduces oxidative stress as an antioxidant, and contribute to oocyte maturation, embryo development and luteinization of granulosa cells. Our clinical study demonstrated that melatonin treatment for infertile women increases intra-follicular melatonin concentrations, reduces intra-follicular oxidative damage, and elevates fertilization and pregnancy rates. Melatonin treatment also improves progesterone production by corpus luteum in infertile women with luteal phase defect. Melatonin treatment could become a new cure for improving oocyte quality and luteal function in infertile women.

Effect of dibutyryl cyclic adenosine monophosphate on reactive oxygen species and glutathione of porcine oocytes, apoptosis of cumulus cells, and embryonic development

The present study was conducted to investigate the effect of dibutyryl cyclic adenosine monophosphate (dbcAMP) supplemented into porcine maturation medium on reactive oxygen species (ROS) and glutathione (GSH) levels of oocytes, and apoptosis of cumulus cells (CC). In addition, the effect of dbcAMP on embryonic development following in vitro fertilization (IVF) or parthenogenetic activation (PA) was determined. Cumulus-oocyte complexes (COCs) were cultured in 0 mM (control), 0.5 mM, 1 mM, 5 mM, or 10 mM dbcAMP-supplemented medium for 22 h, then for another 22 h without dbcAMP. GSH and ROS levels of oocytes were assessed at 44 h of culture by dichlorohydrofluorescein diacetate or 4-chloromethyl-6,8-difluoro-7-hydroxycoumarin staining, respectively. Additionally, COCs were cultured in 0.5 mM or 1 mM dbcAMP and then fertilized in vitro or activated parthenogenetically. Embryonic development and blastocyst cell numbers and apoptosis levels on day 8 of culture were investigated. CC apoptosis at 44 h of culture and blastocyst apoptosis were assessed by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay. GSH levels in the 0.5 mM dbcAMP and control groups were increased (P < 0.05), while levels of oocyte ROS and CC apoptosis in the control, 0.5 mM, and 1 mM dbcAMP groups were significantly lower than the levels in other groups. Cleavage and blastocyst rates, cell numbers, and apoptosis levels were not significantly different in embryos derived by either IVF or PA among the groups, with the exception of significantly increased apoptotic levels in IVF blastocysts produced from oocytes treated with 1 mM dbcAMP. In conclusion, dbcAMP treatment during in vitro maturation (IVM) did not improve embryonic development under our study's parameters compared with control conditions, although 0.5 mM dbcAMP showed significantly higher GSH levels and lower blastocyst apoptotic levels compared with 1 mM dbcAMP.

Developmental competence and embryo quality of small oocytes from pre-pubertal goats cultured in IVM medium supplemented with low level of hormones, insulin-transferrin-selenium and ascorbic acid

The aim of this study was to test the effect of insulin-transferrin-selenium (ITS) and L-ascorbic acid (AA) supplementation and the hormonal level during in vitro maturation (IVM) of small oocytes from pre-pubertal goat on the blastocyst yield and quality. Concretely, we used four maturation media: conventional IVM medium (CM), growth medium (GM: CM+ITS+AA and low level of hormones), modified CM (mCM: CM with low level of hormones) and modified GM (mGM: CM+ITS+AA and normal level of hormones). Cumulus-oocyte complexes (COCs) were classified into two categories according to oocyte diameter: <125 μm and ≥ 125 μm. Large oocytes were matured 24 h in CM (Treatment A). Small oocytes were matured randomly in six experimental groups: Treatment B: 24 h in CM; Treatment C: 12 h in GM and 12 h in CM; Treatment D: 24 h in mGM; Treatment E: 12 h in mGM and 12 h in CM; Treatment F: 12 h in mCM and 12 h in CM; and Treatment G: 12 h in GM and 12 h in mGM. After IVM, oocytes were fertilized and cultured for 8 days. The blastocyst quality was assessed by the survival following vitrification/warming and the mean cell number. When different maturation media were combined, the blastocyst rate did not improve. The large oocytes produced the highest blastocysts yield. However, the culture of small oocytes in GM (53.3%) enhanced the post-warming survival of blastocysts compared to large oocytes matured in CM (35.7%). In conclusion, IVM of pre-pubertal goat small oocytes in GM would be useful to improve the quality of in vitro-produced blastocysts.

Bovine dominant follicular fluid promotes the in vitro development of goat preantral follicles

The aim of this study was to evaluate the effect of follicular fluid collected from bovine dominant follicles (bFF) on the in vitro development of goat preantral follicles and determine the best time to add this supplement to the culture medium. The preantral follicles were isolated and randomly distributed into four treatments in absence (control) or presence of 10% of bFF added on Days 0 (FF0-18), 6 (FF6-18) or 12 (FF12-18) of culture onwards. After 18 days, follicular development was assessed based on follicular survival, antral cavity formation, increased follicular diameter as well as fully grown oocyte (>110 μm) viability and meiosis resumption. The oocytes from the cultured follicles were in vitro-matured and processed for fluorescence or ultrastructural analysis. The results showed that on Day 18 the treatment FF0-18 had a significantly higher (P<0.05) survival than control and FF12-18, but not FF6-18. The addition of bFF at the beginning of culture (FF0-18 and FF6-18) promoted a high percentage of follicular growth, meiosis resumption and early antrum formation. Moreover, this study described for the first time the ultrastructural analysis of caprine oocytes grown in vitro. This evaluation revealed that in the presence of bFF on (FF0-18) the in vitro-grown oocytes presented normal organelle distribution and well-defined, intact plasma and nuclear membranes. In conclusion, bFF originating from dominant follicles maintain the survival and promote the in vitro growth of goat preantral follicles when added at the beginning of culture.

Advances on in vitro production and cryopreservation of porcine embryos

There have been intensive attempts to establish reliable in vitro production (IVP) and cryopreservation methods of embryos in pigs. Although a great deal of progress has been made, current IVP systems and cryopreservation still suffer from insufficient cytoplasmic abilities of in vitro matured oocytes, polyspermic fertilization, poor quality of in vitro produced embryos and low efficiency of embryo cryopreservation. Compared to other mammalian species, pig oocytes and embryos are characterized by large amounts of lipid content stored mainly in the form of lipid droplets in the cytoplasm. This fact has a negative influence on biotechnological applications on porcine oocytes and embryos. In this review, we will discuss recent studies about methods and techniques for modifying porcine embryo IVP system and embryo cryopreservation that produces high quality of pig blastocysts using in vitro maturation, in vitro fertilization, in vitro culture, microsurgical manipulation, addition of protein, the use of cytoskeleton stabilizing agents and various physical methods. The presented methods and techniques make it possible to modify the characteristics of oocytes and embryos and thus may become major tools in mammalian gamete and embryo agricultural or biotechnological applications in the future.

Regulation of oocyte mitochondrial DNA copy number by follicular fluid, EGF, and neuregulin 1 during in vitro maturation affects embryo development in pigs

Little is known about mitochondrial DNA (mtDNA) replication during oocyte maturation and its regulation by extracellular factors. The present study determined the effects of supplementation of maturation medium with porcine follicular fluid (pFF; 0, 10%, 20%, and 30%) on mtDNA copy number and oocyte maturation in experiment 1; the effects on epidermal growth factor (EGF; 10 ng/mL), neuregulin 1 (NRG1; 20 ng/mL), and NRG1 + insulin-like growth factor 1 (IGF1; 100 ng/mL + NRG1 20 ng/mL), on mtDNA copy number, oocyte maturation, and embryo development after parthenogenic activation in experiment 2; and effects on embryo development after in vitro fertilization in experiment 3. Overall, mtDNA copy number increased from germinal vesicle (GV) to metaphase II (MII) stage oocytes after in vitro maturation (GV: 167 634.6 ± 20 740.4 vs. MII: 275 131.9 ± 9 758.4 in experiment 1; P < 0.05; GV: 185 004.7 ± 20 089.3 vs. MII: 239 392.8 ± 10 345.3 in experiment 2; P < 0.05; Least Squares Means ± SEM). Supplementation of IVM medium with pFF inhibited mtDNA replication (266 789.9 ± 11 790.4 vs. 318 510.1 ± 20 377.4; P < 0.05) and oocyte meiotic maturation (67.3 ± 0.7% vs. 73.2 ± 1.2%, for the pFF supplemented and zero pFF control, respectively; P < 0.01). Compared with the control, addition of growth factors enhanced oocyte maturation. Furthermore, supplementation of NRG1 stimulated mitochondrial replication, increased mtDNA copies in MII oocytes than in GV oocytes, and increased percentage of blastocysts in both parthenogenetic and in vitro fertilized embryos. In this study, mitochondrial biogenesis in oocytes was stimulated during in vitro maturation. Oocyte mtDNA copy number was associated with developmental competence. Supplementation of maturation medium with NRG1 increased mtDNA copy number, and thus provides a means to improve oocyte quality and developmental competence in pigs.

The role of melatonin as an antioxidant in the follicle

Melatonin (N-acetyl-5-methoxytryptamine) is secreted during the dark hours at night by pineal gland, and it regulates a variety of important central and peripheral actions related to circadian rhythms and reproduction. It has been believed that melatonin regulates ovarian function by the regulation of gonadotropin release in the hypothalamus-pituitary gland axis via its specific receptors. In addition to the receptor mediated action, the discovery of melatonin as a direct free radical scavenger has greatly broadened the understanding of melatonin's mechanisms which benefit reproductive physiology. Higher concentrations of melatonin have been found in human preovulatory follicular fluid compared to serum, and there is growing evidence of the direct effects of melatonin on ovarian function especially oocyte maturation and embryo development. Many scientists have focused on the direct role of melatonin on oocyte maturation and embryo development as an anti-oxidant to reduce oxidative stress induced by reactive oxygen species, which are produced during ovulation process. The beneficial effects of melatonin administration on oocyte maturation and embryo development have been confirmed by in vitro and in vivo experiments in animals. This review also discusses the first application of melatonin to the clinical treatment of infertile women and confirms that melatonin administration reduces intrafollicular oxidative damage and increase fertilization rates. This review summarizes our recent works and new findings related to the reported beneficial effects of melatonin on reproductive physiology in its role as a reducer of oxidative stress, especially on oocyte maturation and embryo development.

The effects of N-acetyl-L-cysteine supplementation on in vitro porcine oocyte maturation and subsequent fertilisation and embryonic development

The effects of supplementation with 1.5 mM n-acetyl-l-cysteine (NAC) during in vitro oocyte maturation were studied. Oocytes were supplemented with 1.5 mM NAC during maturation for 0 to 24 h, 24 to 48 h, or 0 to 48 h then subjected to IVF and embryo development. Oocytes were evaluated after maturation for intracellular glutathione concentration, superoxide dismutase and glutathione peroxidase activities and DNA fragmentation. Fertilisation and embryonic development success were also evaluated. There was no effect of treatment on intracellular glutathione concentrations, enzyme activities or fertilisation success rates. Supplementing NAC during maturation significantly decreased (P < 0.05) the percentage of oocytes with fragmented DNA compared with no NAC supplementation. Supplementing NAC from 24 to 48 h or 0 to 48 h resulted in a significantly higher (P < 0.05) percentage of oocytes with male pronuclei than for oocytes from the other treatment groups. There was no difference in the percentage of embryos cleaved by 48 h after IVF between treatment groups. Supplementing NAC from 24 to 48 h or 0 to 48 h resulted in a significantly higher (P < 0.05) percentage of embryos reaching the blastocyst stage by 144 h after IVF compared with the other treatment groups. These results indicate that supplementation of the oocyte maturation medium with 1.5 mM NAC, specifically during the last 24 h, improves male pronucleus formation and blastocyst development in pigs.

Synergistic effect of porcine follicular fluid and dibutyryl cyclic adenosine monophosphate on development of parthenogenetically activated oocytes from pre-pubertal gilts

This study investigated the effect of porcine follicular fluid (PFF) and dibutyryl cyclic adenosine monophosphate (dbcAMP) during in vitro maturation (IVM) of porcine oocytes on meiotic maturation, fertilization and embryo development, and compared the effect of supplementing the embryo culture media with PFF or foetal bovine serum (FBS) on embryo development. Oocytes from pre-pubertal gilts were IVM for 44 h, and parthenogenetically activated or in vitro-fertilized. Embryos were cultured in porcine zygote medium (PZM3) for 7 days. Cleavage and blastocyst rates were evaluated at 48 h and 7 days of culture. The supplementation of the IVM medium with 25% PFF and 1 mm dbcAMP for the first 22 h resulted in more (p < 0.05) embryos developing to the blastocyst stage as compared with the inclusion of dbcAMP alone. The dbcAMP + PFF combination increased (p < 0.05) the average number of nuclei per blastocyst as compared with either of these components alone or in its absence. A synergistic effect of dbcAMP + PFF during IVM was also reflected in the capacity of oocytes to regulate sperm penetration and prevent polyspermy, as twice as many oocytes from the control group were penetrated by more than one sperm as compared with those matured in the presence of both dbcAMP and PFF. The supplementation of PZM3 with 10% FBS from days 5 to 7 of culture significantly improved the total cell quantity in embryos derived either from control or dbcAMP + PFF matured oocytes. There was no effect on the total cell quantity when FBS was replaced by the same concentration of PFF. These studies showed that dbcAMP, PFF and FBS can improve both the quantity (57.3% vs 41.5%) and quality (74.8 vs 33.3 nuclei) of porcine blastocysts derived from oocytes recovered of pre-pubertal gilts.

Effects of N-acetyl-cysteine and N-acetyl-cysteine-amide supplementation on in vitro matured porcine oocytes

This study was conducted to evaluate the effects of different concentrations of the antioxidant N-acetyl-cysteine (NAC) supplemented to the maturation medium on porcine embryo development. Concentrations of NAC and its synthetic derivative, NAC-amide (NACA) were evaluated for effects on nuclear maturation, fertilization success and embryo development. Concentrations of NAC (0, 0.5, 1.0, 1.5, 2.0, 2.5 and 5.0 mm) were supplemented to maturing oocytes, and embryo development was analysed at 48 and 144 h post-fertilization. There were no differences among cleavage rates for any of the treatment groups. Blastocyst formation for 1.5 mm NAC (56.5 ± 9.2%) was higher (p < 0.05) than all other supplementations. There were no differences in nuclear maturation or fertilization or in cleavage rates when comparing 1.5 mm NAC and 1.5 mm NACA supplementation to the control. Blastocyst formation for 1.5 mm NAC (44.4 ± 4.7%) and 1.5 mm NACA (46.2 ± 3.4%) supplementation were higher (p < 0.05) than the control (32.1 ± 6.2%) oocytes. These results indicate that supplementing 1.5 mm of NAC or NACA to the oocyte maturation medium increased the percentage of viable embryos reaching the blastocyst stage of development.

Insulin-transferrin-selenium (ITS) improves maturation of porcine oocytes in vitro

The objective of this study was to determine if insulin-transferrin-selenium (ITS) promoted a nuclear and cytoplasmic maturation of porcine oocytes that better supports subsequent embryonic development. The rate of oocyte in vitro maturation (IVM) in an experimental group treated with hormones for 42 h was significantly increased compared with that in a control group without hormone treatment (47.8% vs. 11.7%, respectively, p < 0.05). Following reduction of the hormone treatment period from 42 h to 21 h, which included both the first 21 h period of hormones treatment (45.4%) and the second 21 h period of hormone treatment (44.8%), the rate of oocyte IVM was still higher than that of the control group (p < 0.05). To improve porcine oocyte nuclear maturation, 1% ITS was added to medium supplemented with hormones. The rate of nuclear maturation in the ITS-treated group was significantly higher than in the ITS-untreated group (78.6% vs. 54.4%, respectively, p < 0.05). ITS treatment also significantly reduced the per cent of oocytes with type I and type III cortical granule (CG) distribution, respectively, and significantly increased the per cent of oocytes with type II CG distribution (85.3%). These observations indicated that the synchronization rates of nuclear and ooplasmic maturation reached 67.04% (78.56 × 85.33%). In conclusion, the combination of modified Tissue Culture Medium-199 (mM199) + 10 ng/ml epidermal growth factor (EGF) + 10 IU/ml pregnant mare serum gonadotrophin (PMSG) + 10 IU/ml human chorion gonadotrophin (hCG) + 2.5 IU/ml follicle stimulating hormone (FSH) + 1% ITS is suitable for culturing porcine oocytes in vitro, and effectively enhances porcine oocyte nuclear and cytoplasmic maturation.

The early embryo response to intracellular reactive oxygen species is developmentally regulated

In vitro embryo production (IVP) suffers from excessive developmental failure. Its inefficiency is linked, in part, to reactive oxygen species (ROS) brought on by high ex vivo oxygen (O2) tensions. To further delineate the effects of ROS on IVP, the intracellular ROS levels of early bovine embryos were modulated by: (1) varying O2 tension; (2) exogenous H2O2 treatment; and (3) antioxidant supplementation. Although O2 tension did not significantly affect blastocyst frequencies (P > 0.05), 20% O2 accelerated the rate of first cleavage division and significantly decreased and increased the proportion of permanently arrested 2- to 4-cell embryos and apoptotic 9- to 16-cell embryos, respectively, compared with embryos cultured in 5% O2 tension. Treatment with H2O2, when applied separately to oocytes, zygotes, 2- to 4-cell embryos or 9- to 16-cell embryos, resulted in a significant (P < 0.05) dose-dependent decrease in blastocyst development in conjunction with a corresponding increase in the induction of either permanent embryo arrest or apoptosis in a stage-dependent manner. Polyethylene glycol–catalase supplementation reduced ROS-induced embryo arrest and/or death, resulting in a significant (P < 0.05) increase in blastocyst frequencies under high O2 culture conditions. Together, these results indicate that intracellular ROS may be signalling molecules that, outside an optimal range, result in various developmentally regulated modes of embryo demise.

Effects of vitamin E supplementation on and the association of body condition score with changes in peroxidative biomarkers and antioxidants around calving in dairy heifers

The objective of this study was to investigate the effect of vitamin E supplementation on oxidative status in blood, liver, milk, and ovarian follicular fluid in periparturient heifers. Vitamin E supplementation started 8 wk before calving and continued until 8 wk postpartum. Grass silage was the main forage fed during the experiment. In addition, supplemented heifers (n=9) received 3,000I U of vitamin E daily on a carrier food; control heifers (n=9) consumed only the carrier food. Blood samples and liver biopsies were taken frequently throughout the study and ovarian follicular fluid was sampled at 8 wk postpartum. Body condition score was scored weekly and milk yield was measured daily. A marker of oxidative damage, determinable reactive oxygen metabolites (d-ROM), and a set of antioxidants were measured in blood, liver, milk, and ovarian follicular fluid. Control heifers had a low vitamin E status, and selenium status was marginal in control and supplemented heifers. Vitamin E supplementation increased vitamin E concentrations in blood, liver, and ovarian follicular fluid and increased triacylglycerol in liver. Serum d-ROM were not reduced by vitamin E supplementation. Superoxide dismutase and glutathione peroxidase activity in red blood cells and liver and glutathione peroxidase activity in ovarian follicular fluid were not affected by vitamin E supplementation and they were not increased around calving. Protein thiol groups and ratio of reduced glutathione to oxidized glutathione were also not increased around calving. These results suggest that heifers around calving experience a low level of oxidative processes. This might be caused by lower than expected milk production attributed to a low forage intake. Serum d-ROM were negatively correlated with protein thiol groups and positively correlated with the activity of glutathione peroxidase in red blood cells, oxidized glutathione, and the ratio of reduced glutathione and oxidized glutathione in serum. The lack of treatment effects allowed estimation of the effects of body condition 4 wk before calving and the loss of body condition on markers of lipid peroxidation and antioxidants. A trend that a body condition of >or=3 might result in more oxidative damage measured by serum d-ROM was observed, but fatter heifers had a significantly higher ratio of reduced glutathione to oxidized glutathione.

Serum levels of reactive oxygen species (ROS) in the bitch

The aim of this study was to determine the serum concentrations of reactive oxygen species (ROS) during the different phases of the estrous cycle in the bitch, in order to establish their physiological values. 56 healthy mixed-breed bitches were enrolled at this purpose and divided into 4 groups, standing on the different phases of the estrus cycle. Blood samples were collected in all groups and serum ROS concentrations were determined. Proestral concentrations were statistically higher than anestral ones, and statistically lower than those found in estrus (p<0.001). The highest concentrations of ROS were detected at estrus, that is, in the peri-ovulatory period. This sharp increase in ROS concentrations is related to the acute inflammatory process underlying ovulation and to the increase in immune and metabolic activities, cytological changes and myometrial contractility promoted by the high levels of estrogens. In diestrus, the mean concentration of ROS decreases. This reduction did not show any statistically significant difference with the mean value observed in proestrus. In this phase, in fact, the high concentrations of progesterone, exerting an antioxidant and immunodepressive effect, justify the lower mean concentration of ROS detected. In anestrus, the lowest concentrations of ROS were observed, for the reduced metabolic and endocrine activity occurring in this phase of the estrous cycle. In conclusion our results establish the physiologic levels of ROS during the estrous cycle in the bitch and reflect the endocrine morphologic and metabolic changes occurring during it.

Age related changes in mitochondrial function and new approaches to study redox regulation in mammalian oocytes in response to age or maturation conditions

Mammalian oocytes are long-lived cells in the human body. They initiate meiosis already in the embryonic ovary, arrest meiotically for long periods in dictyate stage, and resume meiosis only after extensive growth and a surge of luteinizing hormone which mediates signaling events that overcome meiotic arrest. Few mitochondria are initially present in the primordial germ cells while there are mitogenesis and structural and functional differentiation and stage-specific formation of functionally diverse domains of mitochondria during oogenesis. Mitochondria are most prominent cell organelles in oocytes and their activities appear essential for normal spindle formation and chromosome segregation, and they are one of the most important maternal contributions to early embryogenesis. Dysfunctional mitochondria are discussed as major factor in predisposition to chromosomal nondisjunction during first and second meiotic division and mitotic errors in embryos, and in reduced quality and developmental potential of aged oocytes and embryos. Several lines of evidence suggest that damage by oxidative stress/reactive oxygen species in dependence of age, altered antioxidative defence and/or altered environment and bi-directional signaling between oocyte and the somatic cells in the follicle contribute to reduced quality of oocytes and blocked or aberrant development of embryos after fertilization. The review provides an overview of mitogenesis during oogenesis and some recent data on oxidative defence systems in mammalian oocytes, and on age-related changes as well as novel approaches to study redox regulation in mitochondria and ooplasm. The latter may provide new insights into age-, environment- and cryopreservation-induced stress and mitochondrial dysfunction in oocytes and embryos.

Profiling of superoxide dismutase isoenzymes in compartments of the developing bovine antral follicles

The antral follicle constitutes a complex and regulated ovarian microenvironment that influences oocyte quality. Oxidative stress is a cellular state that may play a role during folliculogenesis and oogenesis, although direct supporting evidence is currently lacking. We thus evaluated the expression of the three isoforms (SOD1, SOD2, and SOD3) of the enzymatic antioxidant superoxide dismutase in all the cellular (granulosa cells, cumulus cells, and oocytes) and extracellular (follicular fluid) compartments of the follicle. Comparisons were made in bovine ovaries across progressive stages of antral follicular development. Follicular fluid possessed increased amounts of SOD1, SOD2, and SOD3 in small antral follicles when compared with large antral follicles; concomitantly, total SOD activity was highest in follicular fluids from smaller diameter follicles. SOD1, SOD2, and SOD3 proteins were expressed in granulosa cells without any fluctuations in follicle sizes. All three SOD isoforms were present, but were distributed differently in oocytes from small, medium, or large antral follicles. Cumulus cells expressed high levels of SOD3, some SOD2, but no detectable SOD1. Our studies provide a temporal and spatial expression profile of the three SOD isoforms in the different compartments of the developing bovine antral follicles. These results lay the ground for future investigations into the potential regulation and roles of antioxidants during folliculogenesis and oogenesis.

Relationship between cumulus cell apoptosis, progesterone production and porcine oocyte developmental competence: temporal effects of follicular fluid during IVM

The objective of the present study was to determine the temporal effects of sow follicular fluid (FF) in vitro on cumulus cell viability and function, as well as oocyte nuclear and cytoplasmic maturation. Cumulus–oocyte complexes (COCs) recovered from the ovaries of prepubertal pigs were matured in medium with (+FF) or without (–FF) follicular fluid for the first 22 h of IVM. At 22 h of IVM, each group of COCs was then transferred to medium with or without FF and matured for another 22 h, forming four treatment groups (–FF/–FF, –FF/+FF, +FF/–FF and +FF/+FF). The concentration of progesterone in spent IVM medium and the incidence of cumulus cell apoptosis in individual COCs were determined at 22 and 44 h of IVM. Cumulus expansion was also recorded at 44 h of IVM. Finally, the ability of oocytes to complete meiosis to the MII stage and form blastocysts after IVF and embryo culture was assessed. Maturation with FF for part or the whole of IVM increased cumulus expansion and progesterone production and decreased the incidence of cumulus cell apoptosis compared with the –FF/–FF group (P < 0.05). The changes were greatest for the +FF/+FF group and intermediate for the –FF/+FF and +FF/–FF groups. Regression analysis revealed a negative association between cumulus cell progesterone production and the incidence of cumulus cell apoptosis (P < 0.001). Meiotic maturation was enhanced when FF was present during the first half of IVM. Oocytes matured in the presence of FF during the first and/or second half of IVM displayed an increased ability to form blastocysts compared with the –FF/–FF group (P < 0.05). The extent of the increase was similar for all FF-supplemented groups. The results show that FF exerts several beneficial effects at different times during IVM and suggest that a major role of FF is to provide protection from oxidative stress. We propose that the incidence of cumulus cell apoptosis in COCs must be kept below a certain threshold to ensure adequate functionality, including steroidogenic activity, is maintained for the acquisition of oocyte developmental competence.

Could oxidative stress influence the in-vitro maturation of oocytes?

In the efforts aimed at improving the quality of in-vitro-matured human oocytes, the dynamic balance and roles of pro-/antioxidants merit further consideration. In-vitro maturation (IVM) is emerging as a popular technology at the forefront of fertility treatment and preservation. However, standard in-vitro culture conditions exert oxidative stress or an imbalance between oxidants and antioxidants. Reactive oxygen species (ROS) are oxygen-derived molecules formed as intermediary products of cellular metabolism. By acting as powerful oxidants, ROS can oxidatively modify any molecule, resulting in structural and functional alterations. ROS are neutralized by an elaborate defence system consisting of enzymatic and nonenzymatic antioxidants. This review captures the inherent and external factors that may modulate the oxidative stress status of oocytes. It discusses the suspected impacts of oxidative stress on the gamut of events associated with IVM, including prematuration arrest, meiotic progression, chromosomal segregation, cytoskeletal architecture and gene expression. In-vivo and in-vitro strategies that may overcome the potential influences of oxidative stress on oocyte IVM are presented. Future studies profiling the oxidative stress status of the oocyte may permit not only the formulation of a superior IVM medium that maintains an adequate pro-/antioxidant balance, but also the identification of predictors of oocyte quality.

The effects of different concentrations of sodium selenite on the in vitro maturation of preantral follicles in serum-free and serum supplemented media

PURPOSE

This study was to investigate the effect of sodium selenite (SS) on in vitro maturation of mouse preantral follicles.

METHODS

The isolated preantral follicles were cultured in TCM 199 medium supplemented with different concentrations (0, 5, 10, 15 ng/ml) of SS and 3 mg/ml bovine serum albumin (BSA) or 5% Fetal Bovine Serum (FBS). The ovulation was induced by addition of 1.5 IU/ml human chorionic gonadotropin. The size and development of follicles and oocytes were assessed by calibrated eyepiece.

RESULTS

The survival rates of follicles in FBS supplemented groups containing 5 and 10 ng/ml SS (88.23%, 90.83%) were higher than other groups (P < 0.05 and P < 0.001 respectively). The mean diameter of follicles (199.84 +/- 15.58 microm) and the percentage of MII oocyte (33.08%) were higher in FBS supplemented group containing 10 ng/ml SS (P < 0.001).

CONCLUSION

The sodium selenite and FBS improve the in vitro growth and maturation of mouse preantral follicles.

Reactive oxygen species and oocyte aging: role of superoxide, hydrogen peroxide, and hypochlorous acid

Aging of the unfertilized oocyte inevitably occurs following ovulation, limiting its fertilizable life span. However, the mechanisms that regulate oocyte aging are still unclear. We hypothesize that reactive oxygen species such as superoxide (O2-), hydrogen peroxide (H2O2), and hypochlorous acid (HOCl) are likely candidates that may initiate these changes in the oocyte. In order to test this hypothesis, we investigated direct effects of O2- [hypoxanthine/xanthine oxidase system generating 0.12 (n=42) and 0.25 (n=45) microM O2-/min], H2O2 (20 or 100 microM, n=60), and HOCl, (1, 10, and 100 microM, n=50) on freshly ovulated or relatively old mouse oocytes, while their sibling oocytes were fixed immediately or cultured under physiological conditions (n=96). The aging process was assessed by the zona pellucida dissolution time (ZPDT), ooplasm microtubule dynamics (OMD), and cortical granule (CG) status. The ZPDT increased 2-fold in relatively old, compared to young, untreated oocytes (P<0.0001). Exposure to O2- increased it even further (P<0.0001). Similarly, more O2- exposed oocytes exhibited increased OMD and major CG loss, with fewer having normal OMD and intact CG compared to untreated controls. Interestingly, young oocytes resisted "aging," when exposed to 20 microM H2O2, while the same enhanced the aging phenomena in relatively old oocytes (P<0.05). Exposure to even very low levels of HOCl induced the aging phenomena in young and relatively old oocytes, and higher concentrations of HOCl compromised oocyte viability. Overall, O2-, H2O2, and HOCl each augment oocyte aging, more so in relatively old oocytes, suggesting compromised antioxidant capacity in aging oocytes.

Mechanisms of oxidative stress in porcine oocytes and the role of anti-oxidants

The mechanisms of oxidative stress in in vitro maturing porcine oocytes and the effects of anti-oxidant supplementation of the medium in ameliorating these effects were investigated in the present study. In addition to intracellular reduced glutathione (GSH) concentrations and DNA fragmentation, the present study focused on superoxide dismutase (SOD), glutathione peroxidase (GPx) and catalase activity. The anti-oxidants used were N-acetylcysteine (NAC) and its derivative NAC-amide (NACA). The results indicate that when SOD is inhibited, supplementation of the maturarion medium with 1.5 mm NAC or NACA compensates for the decrease in SOD activity by reducing the degree of DNA fragmentation (P < 0.05). When GPx is inhibited, supplementation of the maturarion medium with 1.5 mm NAC alleviates the effects of no GPx activity, as indicated by a decrease in the degree of DNA fragmentation (P < 0.05). When the maturarion medium was supplemented with 1.5 mm NACA, intracellular GSH concentrations decreased (P < 0.05) and SOD and catalase activities increased (P < 0.05) along with the degree of DNA fragmentation. These results indicate that the mechanisms of alleviating oxidative stress in porcine oocytes are very complex and supplementing maturing oocytes with anti-oxidants may enhance enzyme activities and eliminate free radicals.

Somatic cell nuclear transfer in pigs: recent achievements and future possibilities

During the past 6 years, considerable advancement has been achieved in experimental embryology of pigs. This process was mainly generated by the rapidly increasing need for transgenic pigs for biomedical research purposes, both for future xenotransplantation to replace damaged human organs or tissues, and for creating authentic animal models for human diseases to study aetiology, pathogenesis and possible therapy. Theoretically, among various possibilities, an established somatic cell nuclear transfer system with genetically engineered donor cells seems to be an efficient and reliable approach to achieve this goal. However, as the result of unfortunate coincidence of known and unknown factors, porcine embryology had been a handicapped branch of reproductive research in domestic animals and a very intensive and focused research was required to eliminate or minimise this handicap. This review summarises recent achievements both in the background technologies (maturation, activation, embryo culture) and the actual performance of the nuclear replacement. Recent simplified methods for in vivo development after embryo transfer are also discussed. Finally, several fields of potential application for human medical purposes are discussed. The authors conclude that although in this early phase of research no direct evidence can be provided about the practical use of transgenic pigs produced by somatic cell nuclear transfer as organ donors or disease models, the future chances even in medium term are good, and at least proportional with the efforts and sums that are invested into this research area worldwide.

Blastocyst production by in vitro maturation and development of porcine oocytes in defined media following intracytoplasmic sperm injection

The present study was carried out to establish porcine defined IVP. In Experiments 1 and 2, we investigated the efficacy of additional 0.6 mM cystine and/or 100 µM cysteamine (Cys) to a defined TCM199 maturation medium with regard to the intracellular glutathione (GSH) concentration and the developmental competence of in vitro matured porcine oocytes following intracytoplasmic sperm injection (ICSI). The control medium was a modified TCM199 containing 0.05% (w/v) polyvinyl alcohol (PVA). Cys and/or cystine were added to the control medium. The control group and immature oocytes (presumptive germinal vesicle oocytes; GV) were prepared for GSH assay. In Experiment 3, the efficacy of epidermal growth factor (EGF) addition to a modified porcine zygote medium (mPZM) for in vitro culture (IVC) medium was investigated on embryonic development and the mean cell number of blastocysts following ICSI. As a positive or negative control, 0.3% BSA (mPZM-3) or 0.3% PVA (mPZM-4), respectively, was added to the base medium. The defined IVC medium was supplemented with 5 or 10 ng/ml EGF. In Experiment 1, no significant difference was found in the rates of cleavage (31.4–64.3%) and blastocyst formation (6.5–22.9%) among the treatment and control groups. The mean cell numbers per blastocyst ranged from 30 to 48 among the groups without significant differences. However, in Experiment 2, the intracellular GSH concentrations in the oocytes cultured in the medium supplemented with 100 µM Cys (9.6 pmol/oocyte) or Cys + cystine (9.9 pmol/oocyte) were significantly (p < 0.05) higher than the control (2.5 pmol/oocyte) and 0.6 mM cystine (6.5 pmol/oocyte) groups, but not different from the GV group (9.0 pmol/oocyte). The GSH concentration in the cystine group was also significantly (p < 0.05) higher than that in the control group, but not different from the GV group. In Experiment 3, the rates of cleavage and blastocyst formation and the mean cell numbers of blastocysts were not significantly different among the groups. However, the addition of 5 ng/ml EGF into the mPZM-4 resulted in a significantly (p < 0.05) higher blastocyst rate per cleaved embryo than the other two defined groups (mPZM-4 + 5 ng/ml: 48.6%, mPZM-4 and mPZM-4 +10 ng/ml: 23.4% and 23.1%, respectively).

The present results indicate that the addition of Cys to a defined medium for in vitro maturation (IVM) of porcine oocytes increases intracellular GSH concentration. Further addition of cystine into the IVM medium containing 100 µM Cys is not necessary and TCM199 plus Cys (100 µM) could be used as a defined IVM medium for porcine oocytes. The addition of 5 ng/ml EGF to a defined IVC medium has enhanced subsequent development after ICSI. This study shows that porcine blastocysts can be produced by defined media throughout the steps of IVP (IVM, ICSI and IVC).

Regulation of aryl hydrocarbon receptor activity in porcine cumulus–oocyte complexes in physiological and toxicological conditions: the role of follicular fluid

The arylhydrocarbon receptor (AhR) mediates the adverse effects of dioxin-like compounds. However, it has also been reported that the AhR may exert a role in ovarian physiology. In the present study, porcine cumulus–oocyte complexes (COCs) were maturedin vitroin the presence of 10% follicular fluid. Expression of AhR and its partner, AhR nuclear translocator occurs in immature COCs. Afterin vitromaturation (IVM), an up-regulation of AhR and cytochrome P450 1A1 (CYP1A1; the main AhR-target gene) was observed. To explore the role of the AhR during IVM, we exposed the COCs to 50 μM β-napthoflavone (βNF). The treatment induced a marked up-regulation of CYP1A1 mRNA, indicating both constitutive and inducible AhR activity. However, in contrast to what was observed in other cell types, no sign of toxicity was observed in COCs. To investigate if components of porcine follicular fluid may exert a protective role against AhR ligands, we exposed porcine COCs to βNF, in the absence of follicular fluid. In these conditions, a marked decrease in the percentage of matured oocytes, concomitant with an increase in oocyte degeneration, was observed. Furthermore, βNF increased apoptosis in cumulus cells in the absence of follicular fluid, whereas βNF has no effects when COCs were treated in the presence of porcine follicular fluid (pFF). In conclusion, these results suggest the presence of unknown endogenous AhR-ligand(s) during porcine IVM and that a dysregulation of this mechanism may result in ovotoxicity by inducing apoptosis in cumulus cells. However, this phenomenon is interrupted by the presence of follicular fluid, indicating a putative protective role for follicular fluid components against exogenous insults.

In vitro maturation of pig oocytes with different media, hormone and meiosis inhibitors

This study evaluated in vitro maturation of pig oocytes in two maturation media (TCM199 and NCSU23) supplemented with 10% porcine follicular fluid (pFF) or 0.1% polyvinyl alcohol (PVA) and four hormonal treatments. The best media was then used to evaluate the effect of reversible meiosis inhibitors cycloheximide (5 microgram/ml) [DOSAGE ERROR CORRECTED]and butyrolactone I (12.5M) on the maturation of pig oocytes was evaluated. After maturation for 44 h, the oocytes were fixed, stained, and examined under epifluorescence microscopy. The comparison of the proportion of oocytes in metaphase II revealed that hormonal treatment 2(incubation for 22 h - 10 ng EGF/ml, 10 IU hCG/ml and 10 IU eCG/ml, followed by incubation for 22 h - 10 ng EGF/ml) presented higher repeatability percentages: TCM+ PVA (54.5% - 61/112); TCM+ pFF (65.0% - 63/97);NCSU23 + PVA (54.6% - 65/119), and NCSU23 + pFF (58.1% - 61/105). The comparison of maturation media showed that TCM199 presented more constant results than NCSU23. Regarding supplementation with pFF or PVA, TCM199 with pFF presented better results. The comparison between butyrolactone I and cycloheximide demonstrated that both drugs effectively inhibited meiosis; however, only cycloheximide presented metaphase II percentages similar to the control (70.29% and 75.49%, respectively). In conclusion, it is recommended the use of TCM199 medium supplemented with pFF and hormonal treatment with 10 ng EGF/ml, 10 UI hCG/mland 10 UI eCG/ml during the first 22 h and more 22 h with 10 ng EGF/ml for the pig oocytes maturation. Butyrolactone I and cycloheximide effectively arrested/resumpted maturation; however, the oocytes percentages in metaphase II was the same for both cycloheximide and the control groups.

Antihyaluronidase Action of Ellagic Acid Effectively Prevents Polyspermy As a Result of Suppression of the Acrosome Reaction Induced by Sperm-Zona Interaction During In Vitro Fertilization of Porcine Oocytes

The present study was conducted to examine the effects of three tannin relatives (tannic acid, TA; gallic acid, GA; and ellagic acid, EA) on antihyaluronidase and reactive oxygen species (ROS) scavenging activity, in vitro fertilization (IVF) parameters, and the acrosome reaction (AR) induced by sperm-zona interaction. Among the three tannin relatives, TA and EA showed the strongest potency for blocking the hyaluronidase activity of boar sperm, with concentration-dependent inhibition over the range of 2-10 microg/ml. In contrast, ROSs were effectively scavenged by TA and GA, but not EA. When cumulus-free oocytes were inseminated in IVF medium containing 5 microg/ml of the tannin relatives, polyspermy was significantly reduced by TA and EA (32 and 29%, respectively) compared with oocytes treated with or without GA (51 and 69%, respectively) under conditions that maintained a high sperm penetration rate (P<0.05). Interestingly, induction of the AR by treatment of preincubated sperm with progesterone was blocked by TA and GA as a result of their higher levels of ROS scavenging activity, while EA, which possessed weak ROS scavenging activity, did not disturb induction of the AR with progesterone. However, the incidence of AR induced by sperm-zona interaction was significantly decreased by the strong antihyaluronidase actions of TA and EA compared with that in the absence of these compounds. Treatment with the compounds caused neither a protective proteolytic modification of the zona pellucida matrix before fertilization nor a reduction in acrosomal proteolytic activity or the number of zona-bound sperm. These findings suggest that the antihyaluronidase action of EA effectively prevents polyspermy by suppression of AR functionality induced by sperm-zona interaction and that hyaluronidase intervention is therefore required during porcine IVF.

Effects of in vitro maturation of monkey oocytes on their developmental capacity

The study of in vitro maturation (IVM) of rhesus monkey oocytes has important implications for biomedical research and human infertility treatment. In vitro-matured rhesus monkey oocytes show much less developmental potential than IVM oocytes of other species. Since about 1980 when rhesus monkey IVM, in vitro fertilization (IVF) and in vitro embryo culture (IVC) systems were established, numerous efforts have been made to improve the developmental competence of oocytes and to understand the mechanisms regulating oocyte maturation. This review describes recent progress in this area, particularly the effects of factors such as steroid hormones, energy substrates, amino acids, ovarian follicle status, maternal age and breeding season on the developmental competence, gene expression patterns and genome integrity of rhesus IVM oocytes.

Inhibition of boar sperm hyaluronidase activity by tannic acid reduces polyspermy during in vitro fertilization of porcine oocytes

The present study was conducted to examine the effects of three polyphenols (tannic acid, apigenin and quercetin) on hyaluronidase activity and in vitro fertilization (IVF) parameters. Among them, tannic acid showed by far the strongest potency for blocking hyaluronidase activity extracted from preincubated boar sperm, causing a dose-dependent inhibition over the range of 2–10 μg/ml. When cumulus-intact and cumulus-free oocytes were inseminated in IVF medium containing tannic acid, the penetration and the polyspermy rates were significantly decreased in the presence of 10 μg/ml tannic acid compared with those in the absence of tannic acid, and the addition of 5 μg/ml tannic acid significantly reduced the polyspermy rate (p < 0.05) compared with that of the control while maintaining the high penetration rate. However, apigenin and quercetin had no effect on the rate of polyspermy. Interestingly, the incidence of polyspermy was significantly reduced in oocytes inseminated with sperm pretreated with 5 μg/ml tannic acid (p < 0.05), although the pretreatment of oocytes had no effect against the polyspermy after insemination with untreated sperm. Treatment with tannic acid caused neither a protective proteolytic modification of the zona pellucida matrix before fertilization, nor a reduction of the proteolytic activity of acrosomal contents or the number of zona-bound spermatozoa. These data suggest that an appropriate concentration of tannic acid prevents polyspermy through the inhibition of sperm hyaluronidase activity during IVF of porcine oocytes.

Effects of oxidative stress on proliferation of rat hepatic stellate cells and antioxidation of reduced glutathione

AIM: To explore the effects of oxidative stress on the proliferation of rat hepatic stellate cells and the antioxidation of reduced glutathione.

METHODS: Rat hepatic stellate cells were incubated with different concentrations of ferric nitrilotriacetic acid (Fe-NTa). With 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphennylterazolium bromide (MTT) colorimetric assay, the effects of Fe-NTa on the proliferation of hepatic stellate cells at 6, 12, 24 and 48 h was detected, and malondialdehyde (MDA) contents and superoxide dismutase (SOD) activity were also detected. At the same time, hepatic stellate cells were incubated with different concentrations of reduced glutathione (0.5, 2.5, 10 mmol/L), and MTT assay was used to SOD activity again.

RESULTS: In comparison with that in the blank control group at 12 h, the proliferation of hepatic stellate cells was significantly increased when the ferric nitrilotriacetic acid concentrations were 500 and 1000 mmol/L, respectively (A value: 0.369 ± 0.124, 0.485 ± 0.101 vs 0.285 ± 0.044, both P < 0.01); the proliferation of cells incubated with different concentrations of Fe-NTa was also markedly increased at 24 and 48 h (P < 0.01). The proliferation of hepatic stellate cells without Fe-NTa interference at 12, 24 and 48 h was also increased as compared with that at 6 h (A value: 0.285 ± 0.044, 0.253 ± 0.033, 0.278 ± 0.037 vs 0.111 ± 0.005, all P < 0.01), while with the elevation of Fe-NTa concentration, the proliferation of hepatic stellate cells at 12, 24 and 48 h was markedly increased as compared with that at 6 h (P < 0.01). In comparison with those in the control group, SOD activity significantly reduced (156.95 ± 21.17, 100.92 ± 10.02 mkat/L vs 197.74 ± 17.59 mkat/L, all P < 0.01) and MDA contents significantly increased (1123 ± 217, 1549 ± 182 mmol/L vs 580 ± 332 mmol/L, all P < 0.01) when the concentrations of Fe-NTa were 200 and 500 mmol/L. As compared with the model group (200 mmol/L Fe-NTa), the SOD activities in the cells preincubated with reduced glutathione were significantly increased (5.42 ± 0.58, 6.67 ± 0.18, 8.75 ± 0.58 mkat/L vs 2.25 ± 0.35 mkat/L, all P < 0.01).

CONCLUSION: Oxidative stress can significantly promote the proliferation of rat hepatic stellate cells in time- and concentration-dependent manners. Oxidative stress can also lead to lipid peroxidation, while reduced glutathione may play an anti-oxidative role.

Oxidative stress in an assisted reproductive techniques setting

OBJECTIVE

The manipulation of gametes and embryos in an in vitro environment when performing assisted reproductive techniques (ART) carries the risk of exposure of these cells to supraphysiological levels of reactive oxygen species (ROS). The main objective of this review is to provide ART personnel with all the necessary information regarding the development of oxidative stress in an ART setting, as well as the sources of ROS and the mechanisms of oxidative stress-induced damage during ART procedures. The impact of oxidative stress on ART outcome and the different strategies designed to prevent it are also discussed.

DESIGN

Review of international scientific literature. A question-and-answer format was adopted in an attempt to convey comprehensive information in a simple yet focused manner.

RESULT(S)

The pO(2) to which gametes and the embryo are normally exposed in vivo is significantly lower than in vitro. This results in increased production of ROS. Increase in levels of ROS without a concomitant rise in antioxidant defenses leads to oxidative stress. Lipid, protein, and DNA damage have all been associated with oxidative stress. This may ultimately result in suboptimal ART success rates.

CONCLUSION(S)

Many modifiable conditions exist in an ART setting that may aid in reducing the toxic effects of ROS.

Successful piglet production by IVF of oocytes matured in vitro using NCSU-37 supplemented with fetal bovine serum

Recently, piglets have been obtained from in vitro-produced blastocysts by using in vitro maturation systems in which oocytes have been matured in North Carolina State University (NCSU) solution supplemented with porcine follicular fluid (PFF). However, PFF is not available commercially. To prepare PFF from the ovaries required time and effort and there is substantial variation in quality among batches. Furthermore, PFF is considered a potential source of infectious agents. We evaluated another commercially available potential protein source, fetal bovine serum (FBS), for in vitro maturation, to produce embryos and piglets. Cumulus-oocyte complexes were matured in NCSU-37 with PFF or with one of four batches of FBS. The proportions of oocytes with expanded cumulus cells were lower in all FBS batch groups (P < 0.05, 15-41%) than that in the PFF group (74%). The proportions of oocytes that matured were also lower in all FBS batch groups (P < 0.05, 26-41%) than in the PFF group (73%), irrespective of cumulus expansion. However, the proportions of oocytes that underwent germinal vesicle breakdown were almost the same in all groups (76-96%). After in vitro fertilization, the rate of sperm penetration into matured oocytes was higher in the PFF group (P < 0.05, 63%) than in one batch of FBS (22%) and removal of the compacted cumulus cells after maturation did not affect fertilization status (21%). Subsequent in vitro embryo culture of the PFF and FBS groups for 6 day resulted in similar rates of blastocyst formation (17 and 19%, respectively) and similar numbers of cells per blastocyst (43 and 46 cells, respectively). When blastocysts obtained from oocytes matured with FBS were transferred into two recipients, one became pregnant and farrowed seven piglets. Transfer of blastocysts obtained from oocytes matured with PFF into two other recipients resulted in one pregnancy and production of four piglets. These data suggested that porcine in vitro maturation in NCSU-37 supplemented with FBS reduced the maturational ability of oocytes, but once oocytes have matured, they have the same ability to develop to term after in vitro fertilization and embryo transfer as those matured with PFF.

Novel follicular fluid factors influencing oocyte developmental potential in IVF: a review

The aim of IVF centres today is to obtain high quality, developmentally competent embryos, and thus increase live birth rates. Apoptosis in the patient's follicles in among the factors that will determine IVF outcome. Follicular fluid constitutes an important microenvironment, containing apoptotic factors and others, which influence oocyte growth. The sFas-sFas ligand system is present in the follicular fluid and may play a role in preventing oocyte aresia during folliculogenesis. Levels of the anti-apoptotic molecule sFas may be related positively to oocyte maturation and negatively to fertilization and embryo quality. Reactive oxygen species exert a toxic effect when found in high concentrations in the follicular fluid, whereas in low concentrations they might be indispensable for pregnancy and therefore serve as a potential marker for successful IVF outcome. Nitric oxide plays a dual role; in some cells promoting and in others inhibiting apoptosis. Nitric oxide production is stimulated by TNF-alpha, so the latter is also implicated in the apoptotic process. Hyaluronan, a disaccharide, whose functions have not been fully elucidated, is a valuable predictor of oocyte fertilization. Gelatinases are responsible for remodelling during follicular atresia. In conclusion, a number of factors found in the follicular fluid, some involved in apoptosis, can infulence assisted reproduction.

Fundamental roles of reactive oxygen species and protective mechanisms in the female reproductive system

Controlled oxidation, such as disulfide bond formation in sperm nuclei and during ovulation, plays a fundamental role in mammalian reproduction. Excess oxidation, however, causes oxidative stress, resulting in the dysfunction of the reproductive process. Antioxidation reactions that reduce the levels of reactive oxygen species are of prime importance in reproductive systems in maintaining the quality of gametes and support reproduction. While anti-oxidative enzymes, such as superoxide dismutase and peroxidase, play a central role in eliminating oxidative stress, reduction-oxidation (redox) systems, comprised of mainly glutathione and thioredoxin, function to reduce the levels of oxidized molecules. Aldo-keto reductase, using NADPH as an electron donor, detoxifies carbonyl compounds resulting from the oxidation of lipids and proteins. Thus, many antioxidative and redox enzyme genes are expressed and aggressively protect gametes and embryos in reproductive systems.