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Zhenzhen Zhang, Changjiu He, Lu Zhang, Tianqi Zhu, Dongying Lv, Guangdong Li, Yukun Song, Jing Wang, Hao Wu, Pengyun Ji and Guoshi Liu

α-Ketoglutarate (α-KG) is an intermediary metabolite in the tricarboxylic acid (TCA) cycle and functions to inhibit ATPase and maintain the pluripotency of embryonic stem cells (ESCs); however, little is known regarding the effects of α-KG on the development of preimplantation embryos. Herein, we report that α-KG (150 μM) treatment significantly promoted the blastocyst rate, the number of inner cell mass (ICM) cells and foetal growth after embryo transfer. Mechanistic studies revealed two important pathways involved in the α-KG effects on embryo development. First, α-KG modulates mitochondria function by inducing relatively low ATP production without modification of mitochondrial copy number. The relatively low energy metabolism preserves the pluripotency and competence of the ICM. Second, α-KG modifies epigenetics in embryos cultured in vitro by affecting the activity of the DNA demethylation enzyme TET and the DNA methylation gene Dnmt3a to increase the ratio of 5hmC/5mC ratio. Elevation of the 5hmC/5mC ratio not only promotes the pluripotency of the ICM but also leads to a methylation level in an in vitro embryo close to that in an in vivo embryo. All these functions of α-KG collectively contribute to an increase in the number of ICM cells, leading to greater adaptation of cultured embryos to in vitro conditions and promoting foetal growth after embryo transfer. Our findings provide basic knowledge regarding the mechanisms by which α-KG affects embryo development and cell differentiation.

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Shu-Fang Wang, Xi-Hua Chen, Bin He, De-Dong Yin, Hai-Jun Gao, Hao-Qi Zhao, Nan Nan, Shi-Ge Guo, Jian-Bing Liu, Bin Wu and Xiang-Bo Xu

Stress impacts the reproductive axis at the level of the hypothalamus and the pituitary gland, which exert an effect on the ovary. Menstruation is regulated by the hypothalamic–pituitary–ovary (HPO) axis. However, the role of stress in menstruation remains unclear. The objective of this study was to explore the role of stress in endometrial breakdown and shedding, using the pseudopregnant mouse menstrual-like model. Female mice were mated with vasectomized males and labeled day 0.5, upon observation of a vaginal seminal plug. On day 3.5, decidualization was induced in pseudopregnant mice using arachis oil. On day 5.5, pseudopregnant mice with artificial decidualization were placed in restraint tubes for 3 h. The findings indicated that acute restraint stress resulted in the disintegration of the endometrium. While corticosterone concentration in the serum increased significantly due to restraint stress, follicle-stimulating hormone (FSH), luteinizing hormone (LH) and progesterone (P4) levels in the serum decreased significantly. An endometrial histology examination indicated that progesterone implants may rescue P4 decline caused by acute stress and block endometrium breakdown and shedding. In addition, mice were treated with metyrapone, an inhibitor of corticosterone synthesis, 1 h prior to being subjected to restraint stress. Interestingly, metyrapone not only inhibited stress-induced endometrium breakdown and shedding, but also prevented stress-induced reduction of P4, LH and FSH. Furthermore, real-time PCR and western blot showed that mRNA and protein expression of CYP11A1 (cytochrome P450, family 11, subfamily A, polypeptide 1) and steroidogenic acute regulatory protein (StAR), the two rate-limiting enzymes for progesterone synthesis in the ovary, decreased following acute stress. But metyrapone prevented the reduction of StAR expression induced by restraint stress. Overall, this study revealed that acute stress results in an increase in corticosterone, which may inhibit LH and FSH release in the serum and CYP11A1 and StAR expression in the ovary, which finally leads to the breakdown and shedding of the endometrium. These experimental findings, based on the mouse model, may enable further understanding of the effects of stress on menstruation regulation and determine the potential factors affecting stress-associated menstrual disorders.

Free access

Wen-Min Cheng, Lei An, Zhong-Hong Wu, Yu-Bo Zhu, Jing-Hao Liu, Hong-Mei Gao, Xi-He Li, Shi-Jun Zheng, Dong-Bao Chen and Jian-Hui Tian

We recently reported that electrical activation followed by secondary chemical activation greatly enhanced the developmental competence of in vitro matured porcine oocytes fertilized by intracytoplasmic sperm injection (ICSI). We hypothesized that sperm treatment with disulfide bond reducing agents will enhance the development competence of porcine embryos produced by this ICSI procedure. We examined the effects of glutathione (GSH), dithiothreitol (DTT), GSH or DTT in combination with heparin on sperm DNA structure, paternal chromosomal integrity, pronuclear formation, and developmental competence of in vitro matured porcine oocytes after ICSI. Acridine orange staining and flow cytometry based sperm chromatin structure assay were used to determine sperm DNA integrity by calculating the cells outside the main population (COMP αT). No differences were observed in COMP αT values among GSH-treated and control groups. COMP αT values in GSH-treated groups were significantly lower than that in DTT-treated groups. Following ICSI, GSH treatments did not significantly alter paternal chromosomal integrity. Paternal chromosomal integrity in sperm treated with DTT plus or minus heparin was also the lowest among all groups. GSH-treated sperm yielded the highest rates of normal fertilization and blastocyst formation, which were significantly higher than that of control and DTT-treated groups. The majority of blastocysts derived from control and GSH-treated spermatozoa were diploid, whereas blastocysts derived from DTT-treated spermatozoa were haploid. In conclusion, sperm treatment with GSH enhanced the developmental capacity of porcine embryos produced by our optimized ICSI procedure.

Open access

Guangdong Li, Xiuzhi Tian, Dongying Lv, Lu Zhang, Zhenzhen Zhang, Jing Wang, Minghui Yang, Jingli Tao, Teng Ma, Hao Wu, Pengyun Ji, Yingjie Wu, Zhengxing Lian, Wei Cui and Guoshi Liu

NLRP (NACHT, LRR and PYD domain-containing proteins) family plays pivotal roles in mammalian reproduction. Mutation of NLRP7 is often associated with human recurrent hydatidiform moles. Few studies regarding the functions of NLRP7 have been performed in other mammalian species rather than humans. In the current study, for the first time, the function of NLRP7 has been explored in ovine ovary. NLRP7 protein was mainly located in ovarian follicles and in in vitro pre-implantation embryos. To identify its origin, 763 bp partial CDS of NLRP7 deriving from sheep cumulus oocyte complexes (COCs) was cloned, it showed a great homology with Homo sapiens. The high levels of mRNA and protein of NLRP7 were steadily expressed in oocytes, parthenogenetic embryos or IVF embryos. NLRP7 knockdown by the combination of siRNA and shRNA jeopardized both the parthenogenetic and IVF embryo development. These results strongly suggest that NLRP7 plays an important role in ovine reproduction. The potential mechanisms of NLRP7 will be fully investigated in the future.

Free access

Hung-Fu Liao, Chu-Fan Mo, Shinn-Chih Wu, Dai-Han Cheng, Chih-Yun Yu, Kai-Wei Chang, Tzu-Hao Kao, Chia-Wei Lu, Marina Pinskaya, Antonin Morillon, Shih-Shun Lin, Winston T K Cheng, Déborah Bourc'his, Timothy Bestor, Li-Ying Sung and Shau-Ping Lin

Nuclear transfer (NT) is a technique used to investigate the development and reprogramming potential of a single cell. DNA methyltransferase-3-like, which has been characterized as a repressive transcriptional regulator, is expressed in naturally fertilized egg and morula/blastocyst at pre-implantation stages. In this study, we demonstrate that the use of Dnmt3l-knockout (Dnmt3l-KO) donor cells in combination with Trichostatin A treatment improved the developmental efficiency and quality of the cloned embryos. Compared with the WT group, Dnmt3l-KO donor cell-derived cloned embryos exhibited increased cell numbers as well as restricted OCT4 expression in the inner cell mass (ICM) and silencing of transposable elements at the blastocyst stage. In addition, our results indicate that zygotic Dnmt3l is dispensable for cloned embryo development at pre-implantation stages. In Dnmt3l-KO mouse embryonic fibroblasts, we observed reduced nuclear localization of HDAC1, increased levels of the active histone mark H3K27ac and decreased accumulation of the repressive histone marks H3K27me3 and H3K9me3, suggesting that Dnmt3l-KO donor cells may offer a more permissive epigenetic state that is beneficial for NT reprogramming.