48 DEVELOPMENTAL COMPETENCE OF CLONED OR PARTHENOGENETICALLY ACTIVATED PORCINE EMBRYOS: EFFECT OF DIAMETER OF PREPUBERTAL GILT OOCYTES

2011 ◽  
Vol 23 (1) ◽  
pp. 130
Author(s):  
J. Li ◽  
J. Adamsen ◽  
R. Li ◽  
H. Pedersen ◽  
Y. Liu ◽  
...  

One of the primary factors influencing the developmental ability of cloned embryos is the oocyte′s diameter (Hirao et al. 1994 J. Reprod. Fertil. 100, 333–339). However, the oocyte donor's age (i.e. its sexual maturity) is also important to consider, because a high proportion of immature oocytes can be expected (Ikeda and Takahashi 2003 Reprod. Fertil. Dev. 15, 215–221). The present study was to investigate the effect of diameter of oocytes collected from prepubertal gilts weighing 100 to 120 kg on the developmental ability of cloned and parthenogenetically activated (PA) embryos. Cumulus–oocyte complexes collected from ovaries of prepubertal gilts were in vitro matured for 42 to 44 h as described for sow oocytes (Li et al. 2008 Theriog 70, 800–808). After removal of the cumulus cells, the matured oocytes were sorted into 2 groups based on visual inspection: large (L) and small (S) oocytes, whereas non-sorted oocytes were used as control (C). In addition, 1 batch from each of the 3 groups of oocytes had their mean size measured. Subsequently, all 3 groups were used for handmade cloning (HMC; Li et al. 2009 Reprod. Domest. Anim. 44, 122–127) or parthenogenetic activation (PA; Kragh et al. 2005 Theriogenology 64, 1536–1545). Then a chemical activation with 5 μg mL–1 cytochalasin B and 10 μg mL–1 cycloheximide in PZM-3 medium was applied for 4 h on both HMC and PA embryos. Finally, the activated embryos were washed and cultured in PZM-3 medium using the WOW system. The embryo development was evaluated by cleavage rate (Day 2), blastocyst rate (Day 6), and total cell number in blastocysts. Data were analysed by ANOVA with single factor in Excel (Microsoft Excel 2007, Redmond, WA, USA). The results showed (Table 1) that by simple visual observation, oocytes could be easily sorted into the following groups: L group (mean diameter 110 μm, from 105 to 116 μm), S group (mean diameter 101 μm, from 93 to 106 μm) and C group (mean diameter 107 μm, from 93 to 116 μm). Cleavage rates and total cell number were similar in the 3 groups. However, the blastocyst rate in L group either for HMC or PA was higher than S group. The data confirm that prepubertal gilt oocytes are useful for cloning and PA, but developmental rates can be increased by selection of large oocytes by simple visual observation. Table 1.Data analysis results

2009 ◽  
Vol 21 (1) ◽  
pp. 224
Author(s):  
M. M. Pereira ◽  
F. Q. Costa ◽  
P. H. A. Campos ◽  
R. V. Serapiao ◽  
J. Polisseni ◽  
...  

In vitro maturation (IVM) is a critical step in in vitro bovine embryo production. A number of factors can influence the IVM environment, such as media composition and protein supplementation. Serum and higher O2 tension have been shown to reduce embryo quality; however, little is known about the effects of serum and O2 tension during IVM on embryo quality and development. This study aimed to evaluate the effect of serum and O2 tension on IVM of bovine oocytes. Immature oocytes obtained from slaughterhouse ovaries were randomly distributed in 4 groups of IVM: G1 (n = 253), 0.1% polyvinyl alcohol (PVA) in air; G2 (n = 248), 10% inactivated estrous cow serum (ECS) in air; G3 (n = 270), 0.1% PVA under 5% O2; and G4 (n = 236), 10% ECS under 5% O2. In vitro maturation was performed with TCM-199 culture medium supplemented with 20 μg mL–1 FSH, under 5% CO2 at 38.5°C for 24 h. After maturation, oocytes were in vitro fertilized with 2.0 × 106 sperm mL–1 in Fert TALP medium, supplemented with heparin, for 20 h. Presumptive zygotes were denuded by vortexing and cultured in CR2aa medium with 2.5% fetal calf serum under 5% CO2 and 5% O2 at 38.5°C. Cleavage rate was evaluated 72 h postfertilization, and blastocyst rate and total cell number were evaluated 8 days postfertilization. Morphological classification of embryos was performed at Day 8 according to the International Embryo Transfer Society manual (1998). Cleavage, blastocyst, and grade 1 embryo rates were analyzed by chi-square, and total cell number was analyzed by ANOVA, with means compared by LSD. Results are presented as mean ± SEM. There was no difference (P > 0.05) in cleavage rates among G1, G2, and G4 (61.6, 65.3, and 57.6%, respectively), but cleavage rate was lower (P < 0.05) in G3 (52.5%). Blastocyst rates among G1, G3, and G4 (15.8, 17.7, and 20.3%, respectively) were similar (P > 0.05). However, blastocyst rate in G2 (25.0%) was higher (P < 0.05) than in G1 and G3, but was similar to G4 (P > 0.05). Total cell number was similar (P > 0.05) among G2 (194.1 ± 13.1), G3 (173.3 ± 9.0), and G4 (163.8 ± 8.7), but was lower (P < 0.05) in G1 (124.5 ± 11.4). The grade 1 embryo rate was lower (P < 0.05) in G1 (70.3%) than in G2 (89.5%), but was similar (P > 0.05) to G3 (77.0%) and G4 (83.9%). The results suggest that IVM with PVA in TCM-199 medium under 5% O2 can be performed without reducing embryo development and quality, when compared with ECS. On the other hand, oocyte developmental competence seems to be affected when IVM is performed with PVA under air conditions. Financial support: CNPq, FAPEMIG.


2019 ◽  
Vol 31 (1) ◽  
pp. 210
Author(s):  
G. Singina ◽  
E. Shedova ◽  
T. Taradajnic ◽  
V. Konnova ◽  
E. Tsyndrina

To date, considerable progress has been achieved in in vitro production (IVP) technologies in cattle; however, developmental potentials of oocytes matured in vitro remain low compared with in vivo-matured oocytes. Thus, a better understanding of different aspects of oocyte maturation may allow us to increase the embryo development rate. Our study was aimed to assess the effects of progesterone (P4) and prolactin (PRL) on the bovine oocyte developmental competence. Bovine cumulus-enclosed oocytes (CEO) were matured using either one-step or two-step maturation conditions. For the one-step protocol, CEO were cultured for 24h in TCM-199 supplemented with 10% fetal calf serum (FCS), 10μg mL−1 porcine FSH, and 10μg mL−1 ovine LH (standard medium). For the two-step procedure, CEO were first cultured for 16h in the standard medium (n=1263) and then transferred to 1 of 3 experimental media and cultured for additional 8h in either absence or presence of either P4 (50 ng mL−1) or bovine PRL (50ng mL−1). The 3 media tested in the two-step maturation were (1) TCM-199 containing 10% FCS (group 1), (2) TCM-199 containing 3mg mL−1 BSA (group 2), or (3) Fert-TALP medium supplemented with 6mg mL−1 BSA (group 3). Fert-TALP was selected because it can potentially be used throughout maturation and fertilization. Following in vitro maturation, all oocytes underwent an IVF/in vitro culture procedure as described previously (Singina et al. 2014 Reprod. Fertil. Devel. 26, 154). The embryo development was evaluated at Days 2 and 7 for cleavage and blastocyst rates. In addition, obtained blastocysts were fixed, and the total cell number and the level of apoptosis were determined using 4′,6-diamidino-2-phenylindole (DAPI) and TUNEL staining. The data from 4 to 5 replicates (113-159 oocytes per treatment) were analysed by ANOVA. For oocytes matured for 24h in the one-step culture, the cleavage rate, blastocyst rate, total cell number, and apoptotic nuclei per blastocyst were 66.1±1.1, 23.7±2.0, 71.4±9.1, and 4.8±1.2%, respectively. For the two-step culture, the cleavage rate did not differ from that of the one-step culture system, ranging from 64.8 to 76.5%. Also, no effects of the two-step systems were observed on total cell number (63.0-78.8) or the proportion of apoptotic nuclei (3.3-5.3%) at the blastocyst stage. The culture of CEO in group 1 (without the supplements) had a reduced blastocyst rate (17.4±0.4%; P&lt;0.05) compared with the standard one-step maturation group, and the addition of P4 (but not PRL) improved the blastocyst yield (P&lt;0.05). Furthermore, when P4 (but not PRL) was added to group 2 and group 3 media, blastocyst rates increased significantly (32.9±3.1 and 32.8±2.7%, respectively) compared with those of the one-step group (P&lt;0.05), but did not differ from those of untreated groups 2 and 3 (26.2±2.7 and 30.0±3.0%, respectively). Our data indicate that P4 supplementation during the terminal phase of two-step IVM can enhance the developmental competence of bovine oocytes and that the nature of this effect depends on the composition of IVM medium, whereas no effect of PRL supplementation was observed. The study was supported by RFBR (No. 17-29-08035).


2014 ◽  
Vol 26 (1) ◽  
pp. 156 ◽  
Author(s):  
E. R. Lliteras ◽  
M. Chong ◽  
S. Andries ◽  
E. Merckx ◽  
E. P. A. Jorssen ◽  
...  

The production of excessive levels of reactive oxygen species can be a major problem during in vitro embryo culture. Although studies have shown that supplementation with exogenous antioxidants can improve embryo quality, the results are controversial among researchers. In this study, we examined the effects of different concentrations of β-mercaptoethanol (β-ME) added to the culture media, on cleavage rates, the quality and developmental competence of in vitro-produced bovine embryos. The embryos were produced in vitro as described previously (Van Hoeck et al., 2013). Briefly, in total, 753 grade I cumulus–oocyte complexes (COC) from 2- to 6-mm-diameter follicles were matured in groups of 50 in 500 μL of TCM with 20 ng mL–1 EGF for 24 h, fertilized in groups of 100 in 500 μL of fertilization medium for 20 h (5% CO2, 38.5°C). Presumptive zygotes were denuded and randomly assigned to 4 treatments with different concentrations of β-ME: 0 μM (control), 50 μM, 100 μM, and 150 μM. They were cultured in groups of  ±25 in 50 μL of SOF supplemented with ITS (10 μg mL–1 insulin; 5.5 μg mL–1 transferrin; 6.7 ng mL–1 selenium) and 2% BSA and covered with mineral oil (5% O2, 5% CO2, 38.5°C). At 48 h post-insemination (p.i.), cleavage rate was evaluated and expressed as the number of cleaved embryos on total number of oocytes. At Day 7 p.i., blastocyst rate was determined (number of blastocysts on total number of oocytes), blastocysts were fixed in 4% paraformaldehyde, and total cell number was determined by DAPI staining. Data were analysed by ANOVA and post hoc test. Comparable cleavage rates were obtained in treated groups: control (80.8%), 50 μM (77.7%), 100 μM (77.9%), and 150 μM (73.6%; P > 0.05). Also, no significant effect of treatment could be found on blastocyst rates: control (36%), 50 μM (36.5%), 100 μM (38.4%), and 150 μM (30.4%). The total cell number per blastocyst increased significantly (P < 0.05) using 100 μM of β-ME compared with the controls (158.0 ± 24.3 v. 123.2 ± 9.72, respectively). These results suggest that the inclusion of 100 μM β-ME during in vitro embryo culture could be used for production of high quality bovine blastocysts.


Zygote ◽  
2016 ◽  
Vol 24 (6) ◽  
pp. 890-899 ◽  
Author(s):  
A.L.S. Guimarães ◽  
S.A. Pereira ◽  
M. N. Diógenes ◽  
M.A.N. Dode

SummaryThe aim of this study was to evaluate the effect of adding a combination of insulin, transferrin and selenium (ITS) and l-ascorbic acid (AA) during in vitro maturation (IVM) and in vitro culture (IVC) on in vitro embryo production. To verify the effect of the supplements, cleavage and blastocyst rates, embryo size and total cell number were performed. Embryonic development data, embryo size categorization and kinetics of maturation were analyzed by chi-squared test, while the total cell number was analyzed by a Kruskal–Wallis test (P < 0.05). When ITS was present during IVM, IVC or the entire culture, all treatments had a cleavage and blastocyst rates and embryo quality, similar to those of the control group (P < 0.05). Supplementation of IVM medium with ITS and AA for 12 h or 24 h showed that the last 12 h increased embryo production (51.6%; n = 220) on D7 compared with the control (39.5%; n = 213). However, no improvement was observed in blastocyst rate when less competent oocytes, obtained from 1–3 mm follicles, were exposed to ITS + AA for the last 12 h of IVM, with a blastocyst rate of 14.9% (n = 47) compared with 61.0% (n = 141) in the control group. The results suggest that the addition of ITS alone did not affect embryo production; however, when combined with AA in the last 12 h of maturation, there was improvement in the quantity and quality of embryos produced. Furthermore, the use of ITS and AA during IVM did not improve the competence of oocytes obtained from small follicles.


2014 ◽  
Vol 26 (1) ◽  
pp. 123
Author(s):  
Y. Liu ◽  
A. Lucas-Hahn ◽  
B. Petersen ◽  
R. Li ◽  
P. Hassel ◽  
...  

Two nuclear transfer (NT) techniques are routinely used to produce cloned animals, traditional cloning (TC) and handmade cloning (HMC). The TC embryos keep their zona and can be transferred at early stages, whereas HMC embryos are zona-free and must be cultured to the morula/blastocyst stage before transfer. Some studies have shown that in vitro culture reduces embryo development and quality, but it is not known whether embryos produced by TC or HMC differ because of the NT method or the in vitro culture. Therefore, we investigated the developmental competence and histone acetylation (H3K18ac) of porcine NT embryos produced by TC and HMC with (Day 5 and 6) or without (Day 0) in vitro culture. Nuclear transfer experiments were performed on same day (Day 0), using same batch of porcine oocytes and donor cells and same in vitro culture conditions. Cloning procedures were previously described (TC : Cloning Stem Cells 10 : 355; HMC : Zygote 20 : 61). Parthenogenetically activated embryos (PA) were used as control of activation and culture conditions. Embryos from all groups were collected for immunostaining of H3K18ac on Days 0, 5, and 6. The normalized H3K18ac level was calculated as previously described (Epigenetics 6 : 177). Cell numbers per blastocyst in each group were counted on Days 5 and 6. The cleavage rate (Day 2) and blastocyst rates (Days 5 and 6) between groups were analysed by Chi-squared test, whereas cell number per blastocysts and H3K18ac level between groups and days were analysed by ANOVA (SAS version 9.2; SAS Institute Inc., Cary, NC, USA). Cleavage rate of HMC embryos was lower than that of TC embryos, but blastocyst rate and cell number per blastocyst were higher in the HMC group compared with TC (Table 1). Differences of H3K18ac level between HMC, TC, and PA groups were only observed on Day 6 but not on Day 0 or Day 5. Within HMC and TC groups, there was no difference in H3K18ac level between Day 0 and Day 5, but the level was lower on Day 6 compared with Day 5 in the HMC group, whereas the TC group displayed the opposite pattern. In conclusion, NT embryos produced by HMC show higher blastocyst rate and cell number per blastocyst compared with TC embryos. Both in vitro culture and the NT method result in differences of the normalized H3K18ac levels. Further study is needed to investigate putative differences between NT embryos produced by HMC and TC compared to in vivo embryos also after transfer to recipients. Table 1.Cleavage and blastocyst rate, cell numbers, and normalized H3K18ac level for handmade cloning (HMC), traditional cloning (TC), and parthenogenetically activated (PA) embryos1


2013 ◽  
Vol 25 (1) ◽  
pp. 260 ◽  
Author(s):  
I. Grad-Mandryk ◽  
J. Kosenyuk ◽  
B. Gajda

In vitro production of porcine embryos is still relatively inefficient. The main reasons for this limited performance are polyspermy after IVF and the poor developmental ability of obtained zygotes. Intracytoplasmic sperm injection (ICSI) is one possible solution to eliminate polyspermy. The aim of this study was to compare the developmental competence of pig zygotes, total cell number, and DNA fragmentation of pig blastocysts derived from IVF or ICSI. Cumulus–oocyte complexes were obtained by aspiration from antral follicles of ovaries collected from slaughtered gilts. The oocytes were then cultured in modified TC-199 medium to metaphase II for 42 h. Semen for IVF was incubated in modified capacitation medium (M199) for 1 h. The sperm fraction (1 × 106 cells mL–1) was introduced into droplets containing oocytes, and then gametes were co-incubated for 4 h in modified TC-199 medium. Intracytoplasmic sperm injection was performed using a mechanical micromanipulator (Research Instruments Limited, Cornwall, UK). Micromanipulation was carried out in modified NCSU-37 medium. The tails of spermatozoa were broken, and then single spermatozoa were aspirated into the injection pipette. The oocyte was fixed by a holding pipette, and the sperm head was then introduced into the oocyte cytoplasm. Presumptive zygotes were cultured in vitro for 144 h in NCSU-23 medium. The embryo quality criteria were developmental competence (morula and blastocyst rates), total cell number per blastocyst, and degree of apoptosis assessed by TUNEL staining. Data were analysed by chi-squared test. The experiment was performed on 136 zygotes (6 replicates) obtained after IVF and 83 zygotes (4 replicates) obtained after ICSI. Percentages of embryos developed to the morula and blastocyst stages were 42.3 ± 6.1 and 28.8 ± 4.7 after IVF, respectively, and 51.7 ± 15.4 and 34.5 ± 18.9 after ICSI, respectively (no differences were observed). Significant differences were noticed in total number of cells per blastocyst between embryos after IVF and ICSI (33.7 ± 5.39 v. 22.8 ± 3.22; P < 0.01). However, there was no difference in the degree of apoptosis between IVF and ICSI embryos (5.14 ± 3.49 and 6.14 ± 4.88, respectively). Our preliminary studies demonstrated a higher proportion of cell numbers in IVF-derived embryos compared with those produced by ICSI, but the developmental competence and degree of apoptosis, as evaluated by the TUNEL method, in both groups were comparable. This study was funded by project N N311 516140 by the NCN, Poland.


2010 ◽  
Vol 22 (7) ◽  
pp. 1074 ◽  
Author(s):  
Michele M. Pereira ◽  
Marco A. Machado ◽  
Fernanda Q. Costa ◽  
Raquel V. Serapiao ◽  
Joao H. M. Viana ◽  
...  

With an aim to improve the in vitro production of bovine embryos, the present study investigated the effect of serum and oxygen tension during IVM on oocyte developmental competence. Four experimental groups were evaluated: G1, 10% oestrus cow serum (OCS) with 20% O2; G2, 0.1% polyvinyl alcohol (PVA) with 20% O2; G3, 10% OCS with 5% O2; and G4, 0.1% PVA with 5% O2. The proportion of MII oocytes, blastocyst rates and total cell number were not affected (P > 0.05) when the OCS was replaced with PVA under 5% O2, whereas a higher (P < 0.05) blastocyst rate and total cell number were found with OCS compared with PVA under 20% O2. The apoptosis index was lower in blastocysts from oocytes matured with PVA under 5% O2 (G4) compared with other groups (G1, G2 and G3), but no differences (P > 0.05) were found in maturation and blastocyst rates. Significant differences were found in the amount of specific transcripts in oocytes matured under different conditions. In conclusion maturation with PVA and 5% O2 provides an efficient in vitro culture condition for the maturation of bovine oocytes.


2013 ◽  
Vol 25 (6) ◽  
pp. 860 ◽  
Author(s):  
Ambikaprasanna Saha ◽  
Sudeepta K. Panda ◽  
Manmohan S. Chauhan ◽  
Radhey S. Manik ◽  
Prabhat Palta ◽  
...  

The availability of techniques for the vitrification of cloned blastocysts can improve their effective use. The present study compared the developmental competence of buffalo cloned embryos derived from adult (BAF), newborn (BNF) and fetal fibroblast (BFF) before and after vitrification. Despite similar cleavage rates among the three groups, the blastocyst rate was lower for BAF- than BNF- and BFF-derived embryos (30.2 ± 2.2% vs 41.7 ± 1.7% and 39.1 ± 2.1%, respectively; P < 0.01). The total cell number of BNF-derived blastocysts was significantly higher (P < 0.01) than that of BFF-derived blastocysts, which, in turn, was higher (P < 0.01) than that of BAF-derived blastocysts. Following transfer of vitrified–warmed blastocysts to recipients, no pregnancy was obtained with fresh (n = 8) or vitrified–warmed (n = 18) BAF-derived blastocysts, whereas transfer of fresh BNF- (n = 53) and BFF-derived (n = 32) blastocysts resulted in four and three pregnancies, respectively, which aborted within 90 days of gestation. The transfer of vitrified–warmed BNF-derived blastocysts (n = 39) resulted in the live birth of a calf weighing 41 kg, which is now 23 months old and has no apparent abnormality, whereas the transfer of vitrified–warmed BFF-derived blastocysts (n = 18) resulted in one live birth of a calf that died within 6 h. These results demonstrate that cloned buffalo embryos cryopreserved by vitrification can be used to obtain live offspring.


2012 ◽  
Vol 24 (1) ◽  
pp. 207
Author(s):  
Y. Jeon ◽  
S.-S. Kwak ◽  
S.-A. Jeong ◽  
R. Salehi ◽  
Y. H. Seong ◽  
...  

Trans-ε-viniferin is a naturally occurring polyphenol belonging to the stilbenoids family. Trans-ε-viniferin is isolated from Vitis amurensis, 1 of the most common wild grapes in Korea, Japan and China. We investigated the effects of trans-ε-viniferin on in vitro maturation (IVM) and developmental competence after IVF or parthenogenesis (PA). At the laboratory of Veterinary Pharmacology, College of Veterinary Medicine, Chungbuk National University, trans-ε-viniferin was purified from the leaves and stems of Vitis amurensis. Data were analyzed with SPSS 17.0 using Duncan's multiple range test. First, in total, 594 cumulus–oocyte complexes (COC) were used for the evaluation of nuclear maturation. The COC were matured in TCM-199 medium supplemented with various concentrations of trans-ε-viniferin (0, 0.1, 0.5, 1.0 and 5.0 μM) with 10% porcine follicular fluid, 10 IU mL–1 of eCG and 10 IU mL–1 of hCG. After 22 h in maturation culture, the COC were cultured in hormone-free medium supplemented with various concentrations of trans-ε-viniferin for an additional 22 h and then nuclear maturation was evaluated. Second, in total, 300 matured oocytes were used to examine the effects of different trans-ε-viniferin concentrations (0, 0.5 and 5.0 μM) on porcine oocyte intracellular glutathione (GSH) and reactive oxygen species (ROS) levels. Lastly, the developmental competence of oocytes matured with different concentrations of trans-ε-viniferin (0, 0.5 and 5.0 μM) was evaluated after IVF or PA. In total, 711 embryos were evaluated. As results, we observed that trans-ε-viniferin treatment during IVM did not improve the nuclear maturation of oocytes in any group (84.2, 86.6, 85.5, 83.3 and 79.2%, respectively), but significantly increased (P < 0.05) intracellular GSH levels in the 0.5 μM group (0 μM vs 0.5 μM; 14.6 vs 16.8 pmol oocyte–1) and reduced ROS levels (0 μM vs 0.5 μM and 50 μM; 174.6 vs 25.7 and 23.8 pixel oocyte–1). Oocytes treated with trans-ε-viniferin during IVM did not have significantly different cleavage rates or blastocyst formation rates after IVF, but total cell numbers were significantly higher (P < 0.05) in the 0.5 and 5.0 μM treatment groups (53.6 ± 4.0 and 47.9 ± 3.1) compared to the control group (36.4 ± 2.2). The PA embryos showed similar results; there were no significant differences in cleavage rates and blastocyst formation rates, but the total cell number significantly increased in the 0.5 and 5.0 μM treatment groups (59.6 ± 4.2 and 60.8 ± 4.6) compared to the control group (43.1 ± 2.1). In conclusion, these results indicate that trans-ε-viniferin treatment during porcine IVM increased total cell number of blastocysts, possibly through increasing intracellular GSH synthesis and reducing ROS levels. This work was supported by a grant from the Korea institute of Planning & Evaluation for Technology in Food, Agriculture, Forestry & Fisheries, Republic of Korea.


2015 ◽  
Vol 27 (1) ◽  
pp. 106
Author(s):  
J. Tao ◽  
Y. Zhang ◽  
D. Song ◽  
Y. Li ◽  
Y. Zhang

EPZ004777 (EPZ), a specific inhibitor of DOT1L (a methyltransferase of H3K79), can significantly improve the generation and quality of mouse induced pluripotent stem cells [Onder et al. 2012 Nature 483(7391), 598–602), suggesting that H3K79 dimethylation (H3K79me2) is involved in controlling cell pluripotency. To date, however, it is unclear whether H3K79me2 regulates development competency of animal cloned embryos. Thus, we aimed to examine the dynamic changes of H3K79me2 in pre-implantation cloned embryos of pigs, and to explore effect of EPZ treatment of embryos on in vitro development fate in order to lay the foundation for revealing the role of H3K79me2 and mechanisms in controlling cell pluripotency. Porcine cloned embryos were treated immediately when fusion and activation stimuli were conducted, in vitro with porcine zygote medium (PZM)-3, including 0.5, 5, or 50 nM EPZ (S7353, Selleck Chemicals, Houston, TX, USA) and 1‰ DMSO (vol/vol, control group) for 24 h, respectively. Then, they were transferred into fresh PZM-3 without EPZ. We found that there was no significant difference in cleavage rate among groups, whereas the blastocyst rate of 0.5 nM EPZ group was higher than that of control group [28.97 ± 2.65% (28/96) v. 17.13 ± 2.69% (17/96)]. No obvious difference was observed for the total cell number of blastocyst among groups. We further treated the SCNT embryos with 0.5 nM EPZ for 0 (control group), 12, 24, and 36 h, respectively. No significant differences were found for cleavage rate among groups, whereas the blastocyst rates of the 12- and 24-h groups were significantly higher than that of control and 36-h groups [28.56 ± 3.51% (27/97), 28.34 ± 3.00% (25/88) v. 16.32 ± 1.93% (16/97), 17.93 ± 0.64% (18/100)]. Except for the remarkable decrease in the 36-h treatment group, no obvious difference was observed for the total cell number of blastocyst among the other 3 groups. All the above experiments were repeated at least 3 times. These results suggested that treatment of porcine SCNT embryos with 0.5 nM EPZ for 12 to 24 h could improve their development during the early stage. Then, we tested whether the EPZ favoured the in vitro development of porcine SCNT embryos by regulating H3K79me2 reprogramming. Porcine SCNT embryos were treated with 0.5 nM EPZ from the onset of electric activation and fusion stimuli was performed, and then the H3K79me2 signal (by immune-fluorescent staining) and expression of DOT1L (by RT-qPCR) at different development stages was analysed. We found that the H3K79me2 signal in control group (without EPZ treatment) decreased slowly from the time of electric stimulation to 4 hpa, and it disappeared in 8 hpa stage. In the EPZ treatment group, H3K79me2 signal started decreasing from 2 hpa, and disappeared in 8 hpa stage. The mRNA level of DOT1L in EPZ treatment group was lower than that in control group, although the difference was not significant. Taken together, treatment with EPZ at the appropriate concentration and for an appropriate time can improve the early in vitro development of pig SCNT embryos, probably by inhibiting expression of DOT1L and facilitating reprogramming of H3K79me2.Research was supported by NSFC No. 31272442.


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