Improving the meiotic competence of small antral follicle-derived porcine oocytes by using dibutyryl-cAMP and melatonin

OBJECTIVE

We increased the nuclear maturation rate of antral follicle derived oocytes by using a pre-in vitro maturation (IVM) culture system and improved the developmental potential of these porcine pathenotes by supplementing with melatonin. Furthermore, we investigated the expression patterns of genes involved in cumulus expansion (HAS2, PTGS2, TNFAIP6, and PTX3) derived from small and medium antral follicles before and after oocyte maturation.

METHODS

Only the cumulus oocyte-complexes (COCs) derived from small antral follicles were induced with [Pre-SF(+)hCG] or without [Pre-SF(-)hCG] the addition of human chorionic gonadotropin (hCG) during the last 7 h of the pre-IVM period before undergoing the regular culture system. The mature oocytes were investigated on embryonic development after parthenogenetic activation (PA). Melatonin (10-7 M) was supplemented during in vitro culture (IVC) to improve the developmental potential of these porcine pathenotes.

RESULTS

A pre-IVM culture system with hCG added during the last 7 h of the pre-IVM period [Pre-SF(+)hCG] effectively supported small antral follicle-derived oocytes and increased their nuclear maturation rate. The oocytes derived from medium antral follicles exhibited the highest nuclear maturation rate in a regular culture system. Compared with oocytes cultured in a regular culture system, those cultured in the pre-IVM culture system exhibited considerable overexpression of HAS2, PTGS2, and TNFAIP6. Porcine embryos treated with melatonin during IVC exhibited markedly improved quality and developmental competence after PA. Notably, melatonin supplementation during the IVM period can reduce and increase the levels of intracellular reactive oxygen species (ROS) and glutathione (GSH), respectively.

CONCLUSION

Our findings indicate that the Pre-SF(+)hCG culture system increases the nuclear maturation rate of small antral follicle-derived oocytes and the expression of genes involved in cumulus expansion. Melatonin supplementation during IVC may improve the quality and increase the blastocyst formation rate of porcine embryos. In addition, it can reduce and increase the levels of ROS and GSH, respectively, in mature oocytes, thus affecting subsequent embryos.

Comparative Embryo Development Outcomes following Extending Embryo Culture to Day 6: A Retrospective Cohort Study

BACKGROUND

Past studies have shown that culturing slow-growing embryos from day 5 to day 6 may increase vitrification yield. This study aims to evaluate if the proportion of embryos eligible for vitrification increases by growing embryos not vitrified by day 5 to day 6.

MATERIALS AND METHODS

In this retrospective cohort study, a Canadian tertiary-care clinic-based cohort was identified between August 2019 and December 2020. In vitro fertilization (IVF) cycles involving autologous oocytes with at least one viable day 5 embryo were selected for inclusion. We compared embryo developmental outcomes of IVF cycles performed before and after an embryo cryopreservation policy change. Prior to March 2020, good-quality day 5 blastocysts of any stage were eligible for vitrification, and after that date, good-quality expanded blastocysts on either day 5 or day 6 were eligible. The primary outcome is the comparative proportion of embryos eligible for vitrification. The secondary outcome is to identify embryo, maternal and cycle factors that are predictive of day 6 vitrification.

RESULTS

A total of 3,438 viable embryos across 679 consecutive IVF cycles were included in this study. After the policy change, we found similar mean proportions of blastocysts eligible for cryopreservation (46.9% per IVF cycle in group 2 vs. 44.4% in group 1, mean difference 0.025, 95% confidence interval -0.021 to 0.071, P=0.28). The mean number of cryopreserved embryos were significantly higher in group 2 (mean 2.2 vs. 1.7 embryos, P=0.007). Factors that predicated an embryo's progression to day 6 included: younger age of egg provider, presence of an early blastocyst on day 5, and cycles involving surgically-retrieved sperm.

CONCLUSION

A cryopreservation policy change to include good-quality full and expanded day 6 blastocysts while avoiding to vitrify early blastocysts on day 5 yielded comparable proportions of embryos eligible for vitrification per IVF cycle.

The Impact of Two Embryo Culture Media, Synthetic Oviduct Fluid and Commercial BO, on pre-and post-Implantation Development of Cloned SAANEN Goat Embryos

BACKGROUND

Somatic cell nuclear transfer (SCNT) is an approach for the propagation of elite animals. In vitro condition, especially the composition of culture media has a profound effect on the developmental competency of in vitro derived e mbryos. There are limited studies evaluating the effect of culture media on SCNT outcomes. To address this gap, we compare the effect of two culture media synthetic oviduct fluid (SOF) vs. commercial bracket-oliphant (BO) on developmental comptenecy.

MATERIALS AND METHODS

In this experimental study, embryos derived from in vitro fertilized (IVF) and SCNT were cultured in both BO and SOF media for 7 days. In addition to the assessment of cleavage and blastocyst on day 3, and 7, the quantitative expression of 16 genes in theresultant blastocysts were assessed. The resultant SCNT blastocysts from SOF and BO groups were also transferred to the synchronized recipient for developmental competency to term.

RESULTS

The blastocyst rate in the BO medium was significantly higher than that of the SOF medium in the SCNT group (P<0.05). All of the examined genes showed increased expression levels in SCNT blastocyst in both media compared to IVF Blastocyst. In the IVF group, Oct4, Bmpr1, and Gcn5 showed significantly higher expression in the SOF medium compared to the BO medium while Akt, Fgfr4, Sox2 showed significantly lower expression in the SOF medium compared to the BO medium. In the SCNT group, Fgfr4, Gcn5, Fzd, Ctnnb, Bmpr1, and Fgfr4 showed significantly higher expression in SOF compared to BO derived blastocyst.

CONCLUSION

It appears that in SCNT blastocysts, gene regulation is less controlled compared to IVF ones, irrespective of the type of medium. In addition, there are differences regarding certain genes expressions between IVF and SCNT derived blastocysts between SOF and BO, reiterating that culture composition affects developmental competency and gene expression.

Development and pregnancy rates of Camelus dromedarius-cloned embryos derived from in vivo- and in vitro-matured oocytes

Objective

The present study evaluated the efficiency of embryo development and pregnancy of somatic cell nuclear transfer (SCNT) embryos using different source-matured oocytes in Camelus dromedarius.

Methods

Camelus dromedarius embryos were produced by SCNT using in vivo- and in vitro- matured oocytes. In vitro embryo developmental capacity of reconstructed embryos was evaluated. To confirm the efficiency of pregnancy and live birth rates, a total of 72 blastocysts using in vitro- matured oocytes transferred into 45 surrogates and 95 blastocysts using in vivo- matured oocytes were transferred into 62 surrogates by transvaginal method.

Results

The collected oocytes derived from ovum pick up showed higher maturation potential into metaphase II oocytes than oocytes from the slaughterhouse. The competence of cleavage, and blastocyst were also significantly higher in in vivo- matured oocytes than in vitro- matured oocytes. After embryo transfer, 11 pregnant and 10 live births were confirmed in in vivo- matured oocytes group, and 2 pregnant and 1 live birth were confirmed in in vitro- matured oocytes group. Furthermore, blastocysts produced by in vivo-matured oocytes resulted in significantly higher early pregnancy and live birth rates than in vitro-matured oocytes.

Conclusion

In this study, SCNT embryos using in vivo- and in vitro-matured camel oocytes were successfully developed, and pregnancy was established in recipient camels. We also confirmed that in vivo-matured oocytes improved the development of embryos and the pregnancy capacity using the blastocyst embryo transfer method.

RUS6, a DUF647-containing protein, is essential for early embryonic development in Arabidopsis thaliana

BACKGROUND

The Arabidopsis RUS (ROOT UV-B SENSITIVE) gene family contains six members, each of which encodes a protein containing a DUF647 (domain of unknown function 647) that is commonly found in eukaryotes. Previous studies have demonstrated that RUS1 and RUS2 play critical roles in early seedling development. All six RUS genes are expressed throughout the plant, but little is known about the functional roles of RUS3, RUS4, RUS5 and RUS6.

RESULTS

We used a reverse-genetic approach to identify knockout mutants for RUS3, RUS4, RUS5 and RUS6. Each mutant was confirmed by direct DNA sequencing and genetic segregation analysis. No visible phenotypic differences were observed in rus3, rus4, or rus5 knockout mutants under standard growth conditions, but rus6 knockout mutants displayed a strong embryo-lethal phenotype. Two independent knockout lines for RUS6 were characterized. The rus6 mutations could only be maintained through a heterozygote, because rus6 homozygous mutants did not survive. Closer examinations of homozygous rus6 embryos from rus6/ + parent plants revealed that RUS6 is required for early embryo development. Loss of RUS6 resulted in embryo lethality, specifically at the mid-globular stage. The embryo-lethality phenotype was complemented by a RUS6::RUS6-GFP transgene, and GFP signal was detected throughout the embryo. Histological analyses with the β-glucuronidase reporter gene driven by the RUS6 promoter showed tissue- and development-specific expression of RUS6, which was highest in floral tissues.

CONCLUSION

Our data revealed that RUS6 is essential for early embryo development in Arabidopsis, and that the RUS gene family functions in multiple stages of plant development.

The use of pituitary adenylate cyclase-activating polypeptide in the pre-maturation system improves in vitro developmental competence from small follicles of porcine oocytes

OBJECTIVE

We investigated how pituitary adenylate cyclase-activating polypeptide (PACAP) affects embryonic development during pre-in vitro maturation (pre-IVM) using porcine oocytes isolated from small follicles.

METHODS

We divided the follicles into the experimental groups by size (SF, small follicles; MF, medium follicles) and treated with and without PACAP and cultured for 18 hours (Pre-SF[-]PACAP; without PACAP, Pre-SF[+]PACAP; with PACAP) before undergoing IVM. The gene expression related to extracellular matrix formation (amphiregulin, epiregulin, and hyaluronan synthase 2 [HAS2]) and apoptosis (Bcl-2-associated X [BAX], B-cell lymphoma 2, and cysteine-aspartic acid protease 3) was investigated after maturation. The impact on developmental competence was assessed by the cleavage and blastocyst rate and total cell number of blastocysts in embryos generated from parthenogenesis (PA) and in vitro fertilization (IVF).

RESULTS

Cleavage rates in the Pre-SF(+)PACAP after PA were significantly higher than SF and Pre-SF(-)PACAP (p<0.05). The cleavage rates between MF and Pre- SF(+)PACAP groups yielded no notable differences after IVF. Pre-SF(+)PACAP displayed the higher rate of blastocyst formation and greater total cell number than SF and Pre-SF(-)PACAP (p<0.05). Cumulus cells showed significant upregulation of HAS2 mRNA in the Pre-SF(+)PACAP compared to the SF (p<0.05). In comparison to other groups, the Pre-SF(+)PACAP group displayed a downregulation in mRNA expression of BAX in matured oocytes (p<0.05).

CONCLUSION

The PACAP treatment during pre-IVM improved the developmental potential of porcine oocytes derived from SF by regulating cumulus expansion and apoptosis of oocytes.

Effect of oocyte chromatin status in porcine follicles on the embryo development in vitro

Objective

The main goal of this study was to provide a morphological indicator that could be used to select high-quality oocytes of appropriate meiotic and developmental capabilities in pig. The higher quality of immature oocytes, the higher success rates of in vitro maturation (IVM) and in vitro fertilization (IVF). Thus, prior to the IVM culture, it is important to characterize oocytes morphologically and biochemically in order to assess their quality. Two of the largest indicators of oocyte quality are the presence of cumulus cells and status of chromatin. To investigate the effects of porcine oocyte chromatin configurations on the developmental capacity of blastocysts, we assessed oocyte chromatin status according to follicle size and measured the developmental potency of blastocysts.

Methods

To sort by follicle size, we divided the oocytes into three groups (less than 1 mm, 1 to 3 mm, and more than 3 mm in diameter). To assess chromatin configuration, the oocytes were assessed for their stages (surrounded nucleolus [SN] germinal vesicle [GV], non-surrounded nucleolus [NSN] GV, GV breakdown, metaphase I [MI], pro-metaphase II [proMII], and metaphase II [MII]) at different maturation times (22, 44, and 66 h). To assess the development rate, oocytes of each follicle size were subjected to parthenogenetic activation for further development. Finally, GV oocytes were grouped by their chromatin configuration (SN, SN/NSN, and NSN) and their global transcriptional levels were measured.

Results

SN GV oocytes were more suitable for IVF than NSN GV oocytes. Moreover, oocytes collected from the larger follicles had a greater distribution of SN GV oocytes and a higher developmental capacity during IVM, reaching MII more quickly and developing more often to blastocysts.

Conclusion

Porcine oocytes with high-level meiotic and developmental capacity were identified by analyzing the relationship between follicle size and chromatin configuration. The porcine oocytes from large follicles had a significantly higher SN status in which the transcription level was low and could be better in the degree of meiotic progression and developmental capacity.

Low incubation temperature successfully supports the in vitro bovine oocyte maturation and subsequent development of embryos

OBJECTIVE

The aim of this study was to compare the effects of 36.5°C and 38.5°C incubation temperatures on the maturation of bovine oocytes and developmental competence of embryos.

METHODS

In experiment 1, oocytes were maturated in bicarbonate-buffered TCM-199 for 22 hours in a humidified atmosphere of 5% CO₂ in the air at either 36.5°C or 38.5°C and nuclear maturation status were determined. In experiment 2, in vitro fertilized oocytes were allocated randomly into synthetic oviductal fluid medium with or without a mixture of 1 mM L-glutathione reduced and 1,500 IU superoxide dismutase and cultured in a humidified atmosphere of 5% CO₂, 5% O₂, and 90% N₂ in the air at 38.5°C for 8 days.

RESULTS

There were no significant differences between incubation temperatures in terms of oocyte maturation parameters such as cumulus expansion, first polar body extrusion and nuclear maturation. Incubation temperatures during in vitro maturation had no effects on developmental competence of embryos, but supplementation of antioxidants increased (p< 0.05) developmental competence of the embryos. Blastocysts from oocytes matured at 38.5°C had comparatively higher inner cell mass, but low overall and trophectoderm cell numbers (p<0.05).

CONCLUSION

The results of present study showed that maturation of bovine oocytes at 36.5°C may provide a suitable thermal environment for nuclear maturation and subsequent embryo development.

Effect of Glycosaminoglycans on In vitro Fertilizing Ability and In vitro Developmental Potential of Bovine Embryos

The glycosaminoglycans (GAGs) present in the female reproductive tract promote sperm capacitation. When bovine sperm were exposed to 10 μg/ml of one of four GAGs (Chondroitin sulfate, CS; Dermatan sulfate, DS; Hyaluronic acid, HA; Heparin, HP) for 5 h, the total motility (TM), straight-line velocity (VSL), and curvilinear velocity (VCL) were higher in the HP- or HA-treated sperm, relative to control and CS- or DS-treated sperm. HP and HA treatments increased the levels of capacitated and acrosome-reacted sperm over time, compared to other treatment groups (p<0.05). In addition, sperm exposed to HP or HA for 1 h before IVF exhibited significantly improved fertilizing ability, as assessed by 2 pronucleus (PN) formation and cleavage rates at d 2. Exposure to these GAGs also enhanced in vitro embryo development rates and embryo quality, and increased the ICM and total blastocyst cell numbers at d 8 after IVF (p<0.05). A real-time PCR analysis showed that the expression levels of pluripotency (Oct 4), cell growth (Glut 5), and anti-apoptosis (Bax inhibitor) genes were significantly higher in embryos derived from HA- or HP-treated sperm than in control or other treatment groups, while pro-apoptotic gene expression (caspase-3) was significantly lower in all GAG treatment groups (p<0.05). These results demonstrated that exposure of bovine sperm to HP or HA positively correlates with in vitro fertilizing ability, in vitro embryo developmental potential, and embryonic gene expression.

Effect of Culture System on Developmental Competence, Cryosurvival and DNA-Fragmentation of In Vitro Bovine Blastocysts

BACKGROUND

This study investigated the effect of two in vitro embryo culture systems (co-culture system versus cell-free sequential-media) on developmental competence, cryosurvival and DNA- fragmentation of in vitro developed bovine blastocysts.

MATERIALS AND METHODS

Bovine presumptive zygotes were cultured in Ménézo's B2 (B2) plus vero-cells or sequential synthetic oviductal fluid (SOF) for eight days. Subsequently, half of the expanded blastocysts developed in both groups were vitrified, warmed within 30 minutes and post- warming embryos along with their corresponding non-vitrified embryos were cultured for two additional days in the same medium used before vitrification. Embryo development, cryosurvival and apoptosis were compared between the groups.

RESULTS

For non-vitrified embryos, culture in SOF significantly promoted the potency of embryos to develop into blastocysts compared with the co-culture system. The difference in post vitrification survival rate of SOF blastocysts (83.3%) was insignificant compared with co-culture (84.3%). However, while total cell number of warmed blastocysts in the co-culture system was significantly higher in the co-culture versus the sequential system (215.4 vs. 170.4), the quality of survived embryos in terms of hatching ability and apoptosis was adversely affected by co-culture compared with SOF (65.0% vs. 74.3%, and 13.5% vs. 10.0%, respectively; p<0.05).

CONCLUSION

Although co-culture system may increase the viability of embryos following cryopreservation, the potency and dynamics of blastocyst formation significantly increased with sequential media compared to the co-culture system which can compensate for the lower efficiency of sequential media for vitrification/warming purposes.

Evaluating the Role of First Polar Body Morphology on Rates of Fertilization and Embryo Development in ICSI Cycles

BACKGROUND

Recent studies have demonstrated that morphology of the first polar body (1(st)PB) is related to oocyte viability, which can be used as a prognostic tool to predict oocyte performance and pregnancy outcomes in an intracytoplasmic sperm injection (ICSI) program. According to some studies, there is a correlation between oocyte performance and 1(st)PB morphology, while others have not reported any correlation. The objective of this study is to evaluate the role of 1(st)PB morphology on rates of fertilization and embryo development in ICSI cases.

MATERIALS AND METHODS

In this prospective study morphological characteristics of 470 metaphase II (MII) oocytes were assessed in 80 ICSI cycles. The women were ages 21-42 years (mean 32.6 ± 0.2). Their oocytes were retrieved after a hyperstimulation protocol. After denudation, all oocytes were evaluated for 1(st)PB morphology. The oocytes were divided into two groups of A (normal 1(st.)

RESULTS

Twenty-seven percent of oocytes had fragmented 1(st)PB, while the remainder was associated with other morphological abnormalities. A total of 46.1% and 26.9% of oocytes showed double and multiple defects, respectively. RF was the most common abnormality observed in group B. No significant differences in women's' ages between groups A and B were noted (p=0.3). A total of 179 and 107 oocytes (61.5% vs. 59.8%) were fertilized in groups A and B, respectively (p=0.7). The rates of good embryo formation for A and B groups were 66.5% and 55.6% (p=0.07), and cleavage rates were 77.7% and 68.5%, respectively (p=0.09).

CONCLUSION

The data demonstrated that 1(st)PB morphology does not appear to be a prognostic factor for rates of fertilization and embryo development in ICSI cycles.