Transcriptomic analysis of ovarian signaling at the emergence of the embryo from obligate diapause in the American mink (Neovison vison).

Mink embryonic diapause occurs when embryos, at the blastocyst stage, enter a state of a reversible arrest in development and metabolism. Some ovarian factors are required because ovariectomy leads to prevention of implantation in mink. Mechanisms regulating this process, however, remain largely unknown. To explore ovarian modifications associated with emergence of embryonic diapause in mink, there was comparison of transcriptomes after embryonic activation to when there was embryonic diapause using RNA-sequencing. A library of 655 differentially expressed genes (DEGs) of all assembled 33,656 genes was generated. Among these, 558 genes were annotated with 106 genes being expressed to a greater extent in ovaries during embryonic diapause, whereas 452 genes were more abundantly expressed in ovaries after embryonic activation. The major categories of genes with differential transcript abundances include metabolic pathways, metabolism of tryptophan, tyrosine and vitamin B6, oxidoreductase activity, calcium signaling pathway, steroid biosynthesis and lysosome. The APOE and APOA1 hub genes identified through the protein-protein interaction (PPI) analysis have important functions in cholesterol transport and steroidogenesis. Transcript abundances associated with 39 genes were investigated using RT-qPCR procedures to confirm RNA-sequencing data. Of 29 mRNA transcripts, 26 were validated using RNA-sequencing, whereas three of ten indistinguishable genes determined using RNA-sequencing were confirmed. Most of these verified DEGs are involved in the prolactin signaling pathway, formation of functional corpora lutea, and steroid synthesis, suggesting these biological processes are implicated in embryonic reactivation. Overall, results provide new insights into ovarian signaling at the time of emergence of the blastocyst from diapause in mink.

Supplementation with asiatic acid during in vitro maturation improves porcine oocyte developmental competence by regulating oxidative stress.

Asiatic acid is a natural triterpene found in Centella asiatica that acts as an effective free radical scavenger. Our previous research showed that asiatic acid delayed porcine oocyte ageing in vitro and improved preimplantation embryo development competence in vitro; however, the protective effects of asiatic acid against oxidative stress in porcine oocyte maturation are still unclear. Here, we investigated the effects of asiatic acid on porcine oocyte in vitro maturation (IVM) and subsequent embryonic development competence after parthenogenetic activation (PA) and in vitro fertilization (IVF). The results of the present research showed that 10 µM asiatic acid supplementation did not affect the expansion of cumulus cells or polar body extrusion of porcine oocytes, while asiatic acid application significantly increased the subsequent blastocyst formation rate and quality of porcine PA and IVF embryos. Hydrogen peroxide (H2O2) is a reactive oxygen species (ROS) that induces oxidative stress in porcine oocytes. As expected, asiatic acid supplementation not only decreased intracellular ROS levels but also attenuated H2O2-induced intracellular ROS generation. Further analysis revealed that asiatic acid supplementation enhanced intracellular glutathione production, mitochondrial membrane potential, and ATP generation at the end of IVM. In summary, our results reveal that asiatic acid supplementation exerts beneficial effects on porcine oocytes by regulating oxidative stress during the IVM process and could act as a potential antioxidant in porcine oocytes matured in vitro production systems.

Histone deacetylase inhibitor stimulates E2 and P4 secretion in sika deer ovarian granulosa cells at a moderate dose.

The histone deacetylase inhibitor (HDACi) and tumor suppressor play an important role in genome reorganization and epigenetic regulation. In this study, granulosa cells (GCs) isolated from sika deer ovaries were cultured and treated with different concentrations of trichostatin A (TSA) for 48 h. It was found that TSA inhibited GCs proliferation and induced GCs apoptosis by upregulating expression of BAX, meanwhile, downregulating expression of GLUT3, GLUT8, BCL-XL. In addition, TSA caused cell cycle arrest at the G1 and G2/M phase accompanied by reducing expression of Cyclin D2 and CDK4. TSA pretreatment increased DNMT3a, DNMT1, HDAC1, and HAT1 expression, and attenuated them when TAS higher than 50 nM. The protein levels of H3K9ac and H4K8ac in GCs were increased at 48 h after TSA treatment. TSA stimulated the secretion of estradiol and progesterone at a moderate dose. Our data suggest that TSA is important as a regulator of steroid hormone synthesis in granulosa cells during follicular development in the sika deer ovary.

Tauroursodeoxycholic acid enhances the development of porcine embryos derived from in vitro-matured oocytes and evaporatively dried spermatozoa.

Evaporative drying (ED) is an alternative technique for long-term preservation of mammalian sperm, which does not require liquid nitrogen or freeze-drying equipment, but offers advantages for storage and shipping at ambient temperature and low cost. However, the development of zygotes generated from these sperms was poor. Here, we demonstrated that the supplementation of tauroursodeoxycholic acid (TUDCA), an endogenous bile acid, during embryo culture improved the developmental competency of embryos derived from in vitro matured pig oocytes injected intracytoplasmically with boar ED spermatozoa by reducing the production of reactive oxygen species, the DNA degradation and fragmentation, and the expression of apoptosis-related gene Bax and Bak, and by increasing the transcription of anti-apoptosis gene Bcl-XL and Bcl-2. Furthermore, TUDCA treatment promoted the blastocyst quality manifested by the total cell numbers and the ratio of inner cell mass. Taken together, our data suggest that evaporative drying would be a potentially useful method for the routine preservation of boar sperm in combination with further optimization of subsequently embryo culture conditions.

Fecal progestin concentrations as an indicator of reproductive success in American Mink.

Efforts to increase mink reproductive success (live births and litter sizes) can be partly assessed by measurement of blood progesterone levels. However, the stress of blood sampling increases the incidence of failed matings, aborted fetuses and death of the dam. We have therefore non-invasively measured fecal progesterone metabolite (progestin) concentrations during the reproductive cycle of mink. We tested the hypothesis that fecal progestin concentrations during the window of implantation (late March-early April) will, (1): be higher for whelping than non-whelping mink, and (2): be higher for mink mated multiple times, compared to single matings. Mink were mated once (March 3), twice (March 3 and 10) or three times (March 3, 10 and 11) and fecal progestin concentrations determined from March 1 to April 30. The percent mink in each group giving birth to live offspring was 42.8%, 80.8% and 92.3% for mink mated once, twice or three times, respectively (P<0.05). Litter sizes did not differ among mink mated once (5.22±0.55), twice (6.29±0.35) or three times (6.08±0.32; P>0.05). Mean fecal progestin concentrations from mating to diapause (March 19) did not differ between mink that whelped or not, nor in response to the number of times mated. However, mean fecal progestin concentrations for mink that whelped were higher on March 25 (peri-implantation) than March 19 after being mated once (51.96±2.96 vs 23.53±1.89nM/g dry wt; P<0.05), twice (66.00±1.60 vs 25.57±1.28nM/g dry wt; P<0.05) or three times (66.48±1.42/g vs 19.16±1.09nM/g dry wt; P<0.05). During implantation (April 5), mean fecal progestin concentrations for mink that whelped after being mated once (146.60±10.02nM/g dry wt), twice (162.10±5.64nM/g dry wt) or three times (188.50±3.92nM/g dry wt) were significantly higher than for those that failed to whelp; 119.30±8.87nM/g dry wt, 77.84±5.86nM/g dry wt. and 118.9±6.55nM/g dry wt., respectively (P<0.05). Our findings suggest that measurement of fecal progestin concentrations during blastocyst reactivation and implantation may be a useful indicator of successful pregnancies in mink.

Treatment of fetal fibroblasts with DNA methylation inhibitors and/or histone deacetylase inhibitors improves the development of porcine nuclear transfer-derived embryos.

This study investigated whether treating fetal fibroblast cells (donor cells) with epigenetic modification-inducing drugs could improve the development of porcine cloned embryos. Donor cells were treated with different DNA methylation inhibitors (5-aza-dC, zebularine or RG108; 5nM) or histone deacetylase inhibitors (TSA, NaBu or SCR; 50nM) for 1h, and then subjected to SCNT. All of the treated groups showed significantly higher blastocyst formation rates compared to the control group. We chose 5-aza-dC and TSA as a combined treatment, and found that donor cells co-treated with 2.5nM 5-aza-dC for 1h and subsequently treated with 50nM TSA for another 1h before SCNT showed significantly improved blastocyst rates compared to the control, 5-aza-dC-treated, and TSA-treated groups. The levels of DNA methylation were decreased (though not to a significant degree) in donor cells treated with 5-aza-dC, TSA or both. The histone H3 acetylation levels were significantly increased in donor cells treated with TSA or co-treated with 5-aza-dC and TSA. Donor cells simultaneously co-treated with 5nM 5-aza-dC and 50nM TSA for 1h showed increased apoptosis of SCNT blastocysts. However, when we decreased the concentration of 5-aza-dC to 2.5nM, the co-treatment induced less apoptosis among SCNT blastocysts and the blastocyst development rate improved. Together, these results indicate that treatment of donor cells with 5-aza-dC, TSA, or TSA plus a low dose of 5-aza-dC could improve the blastocyst development of porcine cloned embryos.

Epigenetic characterization of the PBEF and TIMP-2 genes in the developing placentae of normal mice.

Reprogramming errors, which appear frequently in cloned animals, are reflected by aberrant gene expression. We previously reported the aberrant expression of TIMP-2 and PBEF in cloned placenta and differential expression of PBEF genes during pregnancy. To examine the epigenetic modifications that regulate dynamic gene expression in developing placentae, we herein analyzed the mRNA and protein expression levels of PBEF and TIMP-2 in the placentae of normal mice during pregnancy and then examined potential correlations with epigenetic modifications. DNA methylation pattern analysis revealed no difference, but ChIP assays using antibodies against H3-K9/K14 and H4-K5 histone acetylation revealed that the H3-K9/K14 acetylation levels, but not the H4-K5 acetylation levels, of the TIMP-2 and PBEF loci were significantly correlated with their gene expression levels during placentation in normal mice. These results suggest that epigenetic changes may regulate gene expression level in the developing placentae of normal mice and that inappropriate epigenetic reprogramming might be one cause of the abnormal placentae seen in cloned animals.