Post-fusion treatment with MG132 increases transcription factor expression in somatic cell nuclear transfer embryos in pigs

Modified Spirulina maxima Pectin Nanoparticles Improve the Developmental Competence of In Vitro Matured Porcine Oocytes

Simple Summary

Poor in vitro embryo development is a major obstacle in porcine assisted reproduction. In the current study, we utilized modified Spirulina maxima pectin nanoparticles as a supplement to improve porcine in vitro maturation medium. Results showed that modified Spirulina maxima pectin nanoparticles at 2.5 µg/mL improved oocyte maturation in form of first polar body extrusion, reduced oxidative stress, and increased the developmental competence of the oocytes after parthenogenetic activation and somatic cell nuclear transfer. Moreover, the relative transcripts quantification showed significant increase in the pluripotency-associated transcripts in the resultant cloned embryos after modified Spirulina maxima pectin nanoparticles supplementation. Therefore, we provide an optimum in vitro maturation condition to improve the in vitro embryo production in porcine.

Abstract

Molecular approaches have been used to determine metabolic substrates involved in the early embryonic processes to provide adequate culture conditions. To investigate the effect of modified Spirulina maxima pectin nanoparticles (MSmPNPs) on oocyte developmental competence, cumulus–oocyte complexes (COCs) retrieved from pig slaughterhouse ovaries were subjected to various concentrations of MSmPNPs (0, 2.5, 5.0, and 10 µg/mL) during in vitro maturation (IVM). In comparison to the control, MSmPNPs-5.0, and MSmPNPs-10 groups, oocytes treated with 2.5 µg/mL MSmPNPs had significantly increased glutathione (GSH) levels and lower levels of reactive oxygen species (ROS). Following parthenogenetic activation, the MSmPNPs-2.5 group had a considerably higher maturation and cleavage rates, blastocyst development, total cell number, and ratio of inner cell mass/trophectoderm (ICM:TE) cells, when compared with those in the control and all other treated groups. Furthermore, similar findings were reported for the developmental competence of somatic cell nuclear transfer (SCNT)-derived embryos. Additionally, the relative quantification of POU5F1, DPPA2, and NDP52 mRNA transcript levels were significantly higher in the MSmPNPs-2.5 group than in the control and other treated groups. Taken together, the current findings suggest that MSmPNP treatment alleviates oxidative stress and enhances the developmental competence of porcine in vitro matured oocytes after parthenogenetic activation and SCNT.

Enhancing Oocyte Competence With Milrinone as a Phosphodiesterase 3A Inhibitor to Improve the Development of Porcine Cloned Embryos

The objective of this study was to investigate the effect of milrinone supplementation as a phosphodiesterase 3A inhibitor during in vitro maturation (IVM) to coordinate the cytoplasmic and nuclear maturation of porcine oocytes and subsequent development of porcine cloned embryos. Brilliant cresyl blue (BCB)-stained (BCB +) oocytes, classified as well-developed, and BCB− oocytes were used in parthenogenesis (PA) and cloning, and their preimplantation development was compared. In PA embryos, BCB + oocytes had significantly higher rates of development than BCB− oocytes in terms of maturation (87.5 vs. 71.3%), cleavage (88.6 vs. 76.3%), and blastocyst development (34.3 vs. 25.3%) and also had higher cell numbers (46.9 vs. 38.9%), respectively (p < 0.05). In cloned embryos, the BCB + group also had a significantly higher blastocyst formation rate than the BCB− group (30.6 vs. 20.1%; p < 0.05). Supplementation with 75 μM milrinone during IVM of BCB− oocytes showed improvement in maturation and blastocyst development rates, which may be due to the coordinated maturation of the cytoplasm with the nucleus as an effect of milrinone. Moreover, the analysis of nuclear reprogramming via the examination of the expression levels of the reprogramming-related genes POU5F1, DPPA2, and NDP52IL in milrinone-supplemented BCB− oocytes showed higher expression levels than that in non-treated BCB− oocytes. These findings demonstrate that milrinone is useful in improving developmental competence in less competent oocytes during IVM and for proper nuclear reprogramming in the production of porcine cloned embryos by coordinating cytoplasmic and nucleus maturation.

Pig Cloning Using Somatic Cell Nuclear Transfer

Porcine cloning technology can be used to produce progenies genetically identical to the donor cells from high-quality breeding pigs. In addition, genetically modified pigs have been produced by somatic cell nuclear transfer using genetically modified porcine fetal fibroblasts. The method of preparing genetically modified pigs is critical for establishing pig models for human diseases, and for generating donor animals for future xenotransplantation. This chapter describes detailed procedures for generating cloned pigs using fetal fibroblasts as nuclear donors.

The neglected part of early embryonic development: maternal protein degradation

The degradation of maternally provided molecules is a very important process during early embryogenesis. However, the vast majority of studies deals with mRNA degradation and protein degradation is only a very little explored process yet. The aim of this article was to summarize current knowledge about the protein degradation during embryogenesis of mammals. In addition to resuming of known data concerning mammalian embryogenesis, we tried to fill the gaps in knowledge by comparison with facts known about protein degradation in early embryos of non-mammalian species. Maternal protein degradation seems to be driven by very strict rules in terms of specificity and timing. The degradation of some maternal proteins is certainly necessary for the normal course of embryonic genome activation (EGA) and several concrete proteins that need to be degraded before major EGA have been already found. Nevertheless, the most important period seems to take place even before preimplantation development-during oocyte maturation. The defects arisen during this period seems to be later irreparable.

Improved preimplantation development of porcine somatic cell nuclear transfer embryos by caffeine treatment

This study examined the effects of a caffeine treatment to improve nuclear reprogramming in porcine cloned embryos. Embryonic development and the expression of genes related to pluripotency (POU5F1, SOX2, NANOG, and CDX2) were compared after caffeine supplementation during manipulation at different concentrations (0, 1.25, 2.5, and 5.0 mM) and after varying the delayed activation time (control, 1, 2, and 4 h) after fusion. Caffeine added to media during manipulation produced a higher rate of development to blastocysts in the 1.25 mM group than in the other concentration groups (22.8% vs. 16.1%, 16.2%, and 19.2%; p < 0.05). When caffeine was added during the 4 h delayed activation, the 1.25 mM caffeine concentration produced a significantly higher rate of development than those in the other 4 h-activation-delayed caffeine concentration groups (22.4% vs. 9.4%, 14.0%, and 11.1%; p < 0.05). On the other hand, no significant improvement over that in the control group was observed when caffeine was supplemented during both the manipulation period and delayed activation period (16.0% vs. 15.2%), respectively. The levels of POU5F1, SOX2, and NANOG expression in blastocysts were significantly higher in the delayed activation caffeine group (4 h, 1.25 mM) than in the control group (1 h, 0 mM; p < 0.05). In conclusion, a caffeine treatment at 1.25 mM during delayed activation for 4 h can improve the preimplantation development of porcine somatic cell nuclear transfer embryos by activating nuclear reprogramming.

Cytoplasmic volume of recipient oocytes affects the nucleus reprogramming and the developmental competence of HMC buffalo (Bubalus bubalis) embryos

The present study was undertaken to examine the effects of cytoplasmic volume on nucleus reprogramming and developmental competence of buffalo handmade cloning (HMC) embryos. We found that both HMC embryos derived from ~150% cytoplasm or ~225% cytoplasm resulted in a higher blastocyst rate and total cell number of blastocyst in comparison with those from ~75% cytoplasm (25.4 ± 2.0, 27.9 ± 1.6% vs. 17.9 ± 3.1%; 150 ± 10, 169 ± 12 vs. 85 ± 6, P<0.05). Meanwhile, the proportions of nuclear envelope breakdown (NEBD) and premature chromosome condensation (PCC) were also increased in the embryos derived from ~150 or ~225% enucleated cytoplasm compared to those from ~75% cytoplasm. Moreover, HMC embryos derived from ~225% cytoplasm showed a decrease of global DNA methylation from the 2-cell to the 4-cell stage in comparison with those of ~75% cytoplasm (P<0.05). Furthermore, the expression of embryonic genome activation (EGA) relative genes (eIF1A and U2AF) in HMC embryos derived from ~225% cytoplasm at the 8-cell stages was also found to be enhanced compared with that of the ~75% cytoplasm. Two of seven recipients were confirmed to be pregnant following transfer of blastocysts derived from ~225% cytoplasm, and one healthy cloned calf was delivered at the end of the gestation period, whereas no recipients were pregnant after the transfer of blastocysts derived from ~75% cytoplasm. These results indicate that the cytoplasmic volume of recipient oocytes affects donor nucleus reprogramming, and then further accounted for the developmental ability of the reconstructed embryos.

Dog cloning with in vivo matured oocytes obtained using electric chemiluminescence immunoassay-predicted ovulation method

Radioactive immunoassay (RIA) is a traditional serum hormone assay method, but the application of the method in reproductive studies is limited by the associated radioactivity. The aim of present study was to evaluate the reliability of RIA and to compare its canine serum progesterone concentration determination accuracy to that of the electric chemiluminescence immunoassay (ECLI). In vivo matured oocytes were utilized for canine somatic cell nuclear transfer (SCNT), and serum progesterone levels were assessed to accurately determine ovulation and oocyte maturation. Canine serum progesterone concentrations during both proestrus and estrus were analyzed by RIA and ECLI to determine the ovulation day. Although both methods detected similar progesterone levels before ovulation, the mean progesterone concentration determined using ECLI was significantly higher than of RIA three days before ovulation. Following ovulation, oocytes were collected by surgery, and a lower percentage of mature oocytes were observed using ECLI (39%) as compared to RIA (67%) if 4-8ng/ml of progesterone were used for determination of ovulation. A high percentage of mature oocytes was observed using ECLI when 6-15 ng/mL of progesterone was used for ovulation determination. To determine whether ECLI could be used for canine cloning, six canines were selected as oocyte donors, and two puppies were obtained after SCNT and embryo transfer. In conclusion, compared to the traditional RIA method, the ECLI method is a safe and reliable method for canine cloning.

Prolonged proteasome inhibition cyclically upregulates Oct3/4 and Nanog gene expression, but reduces induced pluripotent stem cell colony formation

There is ample evidence that the ubiquitin-proteasome system is an important regulator of transcription and its activity is necessary for maintaining pluripotency and promoting cellular reprogramming. Moreover, proteasome activity contributes to maintaining the open chromatin structure found in pluripotent stem cells, acting as a transcriptional inhibitor at specific gene loci generally associated with differentiation. The current study was designed to understand further the role of proteasome inhibition in reprogramming and its ability to modulate endogenous expression of pluripotency-related genes and induced pluripotent stem cells (iPSCs) colony formation. Herein, we demonstrate that acute combinatorial treatment with the proteasome inhibitors MG101 or MG132 and the histone deacetylase (HDAC) inhibitor valproic acid (VPA) increases gene expression of the pluripotency marker Oct3/4, and that MG101 alone is as effective as VPA in the induction of Oct3/4 mRNA expression in fibroblasts. Prolonged proteasome inhibition cyclically upregulates gene expression of Oct3/4 and Nanog, but reduces colony formation in the presence of the iPSC induction cocktail. In conclusion, our results demonstrate that the 26S proteasome is an essential modulator in the reprogramming process. Its inhibition enhances expression of pluripotency-related genes; however, efficient colony formation requires proteasome activity. Therefore, discovery of small molecules that increase proteasome activity might lead to more efficient cell reprogramming and generation of pluripotent cells.

Treatment with the proteasome inhibitor MG132 during the end of oocyte maturation improves oocyte competence for development after fertilization in cattle

Maturation of the oocyte involves nuclear and cytoplasmic changes that include post-translational processing of proteins. The objective was to investigate whether inhibition of proteasomes during maturation would alter competence of the bovine oocyte for fertilization and subsequent development. Cumulus-oocyte complexes were cultured in the presence or absence of the proteasomal inhibitor MG132 from either 0-6 h or 16-22 h after initiation of maturation. Treatment with MG132 early in maturation prevented progression to meiosis II and reduced fertilization rate and the proportion of oocytes and cleaved embryos that became blastocysts. Conversely, treatment with MG132 late in maturation improved the percentage of oocytes and cleaved embryos that became blastocysts without affecting nuclear maturation or fertilization rate. Optimal results with MG132 were achieved at a concentration of 10 µM - effects were generally not observed at lower or higher concentrations. Using proteomic analysis, it was found that MG132 at the end of maturation increased relative expression of 6 proteins and decreased relative expression of 23. Among those increased by MG132 that are potentially important for oocyte competence are GAPDH, involved in glycolysis, TUBA1C, needed for organellar movement, and two proteins involved in protein folding (P4HB and HYOU1). MG132 decreased amounts of several proteins that exert anti-apoptotic actions including ASNS, HSP90B1, PDIA3 and VCP. Another protein decreased by MG132, CDK5, can lead to apoptosis if aberrantly activated and one protein increased by MG132, P4HB, is anti-apoptotic. Finally, the pregnancy rate of cows receiving embryos produced from oocytes treated with MG132 from 16-22 h of maturation was similar to that for control embryos, suggesting that use of MG132 for production of embryos in vitro does not cause a substantial decrease in embryo quality.

Effects of combined treatment of MG132 and scriptaid on early and term development of porcine somatic cell nuclear transfer embryos

Although improving, the efficiency of producing offspring by somatic cell nuclear transfer (SCNT) is still low (<1.5%). Our laboratory has demonstrated that histone deacetylase inhibitor (Scriptaid) treatment of reconstructed embryos enhances blastocyst formation and cloning efficiency in pigs. It has also been shown that proteasomal inhibitor MG132 treatment for 2 h after activation of oocytes increases blastocyst rate and pregnancy rate. The current experiment was carried out to determine the effects of combined MG132 and Scriptaid treatment on early embryo development in vitro and on term development in vivo. Immediately after electrofusion and activation, SCNT oocytes were treated with 0, 1, or 10 μM MG132 for 2 h in the presence of 500 nM Scriptaid, washed and treated with Scriptaid for an additional 14 to 15 h, then cultured in porcine zygote medium 3 (PZM3) until day 6. There was no difference in percent cleavage (58.1 ± 7.2%, 62.7 ± 7.2%, and 62.5 ± 7.2%) on day 2, or total cell number (23.1 ± 2.2, 24.0 ± 2.0, and 24.5 ± 2.3 for the 0, 1, and 10 μM MG132 groups, respectively) on day 6 among the three groups. Interestingly, there was no difference in percentage of blastocysts between the 0 (18.5±4.7%) and 1 (25.1 ± 4.7%) μM MG132 treatment groups; however, compared with the 10 μM MG132 group (14.0 ± 4.7%), more embryos from the 1 μM MG132 group developed into blastocysts (p<0.05). To determine the effects on term development in vivo, two MG132 groups were included (0 and 1 μM MG132), and embryos were treated as above and transferred into synchronized surrogates after treatment. There was no difference in the oocyte-donor cell fusion rate, number of embryos transferred, pregnancy rate at days 28, 60, and at term, pigs delivered per embryo transfer, litter size, body weight at birth, nor cloning efficiency between the Scriptaid-alone control and MG132+Scriptaid combined groups. In summary, the combined treatment of MG132 and Scriptaid did not improve term development compared to Scriptaid treatment alone.

Viability of ICSI oocytes after caffeine treatment and sperm membrane removal with Triton X-100 in pigs

Non-adequate decondensation of injected sperm nucleus is one the main problems of intracytoplasmic sperm injection (ICSI) in porcine. With the aim of improving pronuclear formation, the effects on activation and embryo development rates of 0.1% Triton X-100 (TX) sperm pre-treatment for membrane removal and/or 5 mM Caffeine (CAF) addition in oocyte manipulating and culture medium for 2 h after ICSI or artificial activation were studied. The effects of 4 different Ca(2+) concentrations contained in the injection medium on embryo development after sham injection were also analysed. In Experiment 1, no significant effect on cleavage or blastocyst rate was detected independently of Ca(2+) concentration contained in the injection medium. In Experiment 2, oocytes injected with TX pre-treated sperm showed a significant higher rate of male pronuclear formation in comparison with oocytes from control group (2PN; 54.1 vs 36.6%). However, no differences on in vitro embryo development, cleavage or blastocyst rates were observed. In Experiment 3, oocytes treated with CAF during and after micromanipulation and injected with sperm pre-treated with TX had a significantly lower oocyte activation rate than any other experimental groups (25.7 vs 56.3-66.3%). No differences were observed in cleavage rates among different experimental groups. However, the CAF group showed a higher blastocyst rate significantly different from TX+CAF group (12.0 vs 1.9%, respectively). In a second approach, the effect of electric field strengths and CAF treatments on oocyte activation was studied. In Experiment 4, oocytes submitted to 0.6 kV/cm showed significant higher activation rates than 1.2 kV/cm ones regardless of the caffeine treatment (83.7 vs 55.9% and 75.7 vs 44.3%; in control and caffeine groups, respectively). No effect of caffeine treatment was observed in any experimental group. In conclusion, TX sperm treatment before ICSI without an additional activation procedure improved male pronuclear formation, but did not improve embryo development until blastocyst stage. No significant effect of caffeine was found when sperm was not treated with TX, although in membrane absence caffeine avoided oocyte activation and embryo development. Finally, caffeine had no effect on female pronuclear formation regardless of electric field strengths applied to the parthenogenetic activation.

MG132 treatment during oocyte maturation improves embryonic development after somatic cell nuclear transfer and alters oocyte and embryo transcript abundance in pigs

The objective of this study was to examine the effect of treating pig oocytes during in vitro maturation (IVM) with a proteasome inhibitor, MG132, on oocyte maturation and embryonic development. In one series of experiments, oocytes from medium-sized follicles (3-8 mm in diameter) were untreated (MCO) or treated with MG132 during 0-22 hr (M0-22) or 30-42 hr (M30-42) of IVM. There was no significant effect of MG132 on nuclear maturation or cytoplasmic maturation (as assessed by intracellular amounts of glutathione and p34cdc2 kinase activity). Blastocyst formation after parthenogenetic activation (PA) and somatic cell nuclear transfer (SCNT), however, was increased for M30-42 (65.2% and 27.7% for PA and SCNT, respectively) compared to MCO (42.6% and 13.6%, respectively) and M0-22 (45.3% and 19.5%, respectively; P<0.05). Expression of PCNA and ERK2 was increased in M30-42 for IVM oocytes while transcript abundance for POUF51, DNMT1, FGFR2, and PCNA was increased in M30-42 for 4-cell SCNT embryos. When oocytes derived from small follicles (<3 mm in diameter) were untreated (SCO) or treated with MG132 during 0-22 hr (S0-22), 30-42 hr (S30-42) of IVM, or 0-22 and 30-42 hr of IVM (S0-22/30-42), expression of POU5F1, DNMT1, FGFR2, and PCNA and blastocyst formation were increased for SCNT embryos derived from S30 to 42 (16.5%) and S0-22/30-42 oocytes (20.8%) as compared to embryos from SCO (8.7%) or S0-22 oocytes (8.8%; P<0.05). Results demonstrate that treatment of oocytes with MG132 during the later stage of IVM improves embryonic development and alters gene expression in pigs.