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Yen-Tzu Tseng, Hung-Fu Liao, Chih-Yun Yu, Chu-Fan Mo and Shau-Ping Lin

Appropriate regulation of epigenome within cells is crucial for the determination of cell fate and contributes to the lifelong maintenance of tissue homeostasis. Epigenomic re-establishment during embryonic prospermatogonia development and fine-tune of the epigenetic landscape in postnatal spermatogonial stem cells (SSCs) are two key processes required for functional male germ cell formation. Repression of re-activated transposons and male germline-specific epigenome establishment occur in prospermatogonia, whereas modulations of the epigenetic landscape is important for SSC self-renewal and differentiation to maintain the stem cell pool and support long-term sperm production. Here, we describe the impact of epigenome-related regulators and small non-coding RNAs as well as the influence of epigenome modifications that result from extrinsic signaling for controlling the decision between self-renewal, differentiation and survival in mouse prospermatogonia and SSCs. This article provides a review of epigenome-related molecules involved in cell fate determination in male germ cells and discusses the intriguing questions that arise from these studies.

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Jun Yin, Bing Ni, Yi-dong Yang, Zhong-wei Tang, Zhi-qi Gao, Lan Feng, Wei-gong Liao and Yu-qi Gao

Autophagy and apoptosis are interlocked in an extensive crosstalk. Our previous study demonstrated that hypotonic hypoxia-induced marked apoptosis of a spermatocyte-derived cell line (GC-2). However, whether hypoxia-induced apoptosis is mediated by inhibition of autophagy under hypoxic conditions remains unclear. In this study, GC-2 cells were cultured in 1% O2 and harvested at different time points. Autophagy was determined by acridine orange staining, cyto-ID staining, mCherry-GFP-LC3B adenovirus transfection and Western blotting for various autophagy markers. Apoptosis was detected by TUNEL staining, flow cytometry, JC-1 staining and Western blotting of apoptosis-related proteins. We found that hypoxia-induced apoptosis of GC-2 cells through mitochondrial and death receptor pathways and inhibited autophagic flux in GC-2 cells in a time-dependent manner. However, while marked autolysosome formation was observed in GC-2 cells before 24-h culture in hypoxic conditions, apparent apoptosis was observed only after 24-h culture in hypoxic conditions. Caspase-8 siRNA treatment induced cell survival, accompanied by induction of the mature autophagosome, acidic vesicular organelle formation and autophagic flux. Furthermore, Beclin-1 overexpression markedly attenuated the impairment of spermatogenesis in mice by inhibiting apoptosis of spermatocytes. The results of this study demonstrate that hypoxia inhibits autophagy, which further enhances hypoxia-induced apoptosis of mouse spermatocytes by promoting caspase-8 activation in a time-dependent manner, suggesting that combined application of apoptosis inhibition and autophagy activation might be a therapeutic strategy for treating hypoxia-induced male infertility.

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Shengxian Li, Jia Qi, Yongzhen Tao, Qinling Zhu, Rong Huang, Yu Liao, Jiang Yue, Wei Liu, Hanting Zhao, Huiyong Yin and Yun Sun

Polycystic ovary syndrome (PCOS) is the most common endocrine disorder in reproductive-age women usually accompanied by lipid metabolic disorders. However, it remains unknown whether arachidonic acid (AA) and its metabolites in follicular fluid (FF) were altered in PCOS patients. This study was intended to measure the levels of AA and its metabolites in the FF of non-obese PCOS patients that underwent in vitro fertilization (IVF) and to explore the possible causes of the alterations. Thirty-nine non-obese women with PCOS and 30 non-obese women without PCOS were enrolled. AA and its metabolites were measured by liquid chromatography-mass spectrometry. The levels of AA metabolites generated via cyclooxygenase-2 (COX-2) pathway and cytochrome P450 epoxygenase pathway but not lipoxygenase (LOX) pathway were significantly higher in the FF of PCOS patients. The metabolites generated via COX-2 pathway were significantly correlated with levels of testosterone and fasting insulin in serum. The in vitro study further demonstrated that insulin but not testosterone could promote the IL-1β and hCG-induced COX-2 expression and prostaglandin E2 (PGE2) secretion in primary human granulosa cells. In conclusion, there was an elevation in AA metabolites in FF of PCOS patients. Insulin played a pivotal role in the increased AA metabolites generated via COX-2, which could be interpreted as another novel molecular pathophysiological mechanism of PCOS.

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Mian Liu, Xia Chen, Qing-Xian Chang, Rui Hua, Yan-Xing Wei, Li-Ping Huang, Yi-xin Liao, Xiao-Jing Yue, Hao-Yue Hu, Fei Sun, Si-Jia Jiang, Song Quan and Yan-Hong Yu

Small extracellular vesicles (sEVs) are important mediators of cell-to-cell communication involved in the successful establishment of a pregnancy. Human decidual stromal cells play a key role in regulating trophoblast invasion. Nevertheless, the regulatory functions of decidual stromal cells-derived sEVs in human trophoblast cells are still unclear. In this study, primary human decidual stromal cells were isolated, and immortalized human endometrial stromal cell line (HESCs) were decidualized into human decidual stromal cells (HDSCs) using hormonal cocktail containing medroxy progesterone 17-acetate (MPA), estrogen and cAMP analog. HDSC-sEVs were isolated from both primary human decidual stromal cells and immortal HDSCs, respectively, and identified by transmission electron microscopy and western blotting. EV uptake assay indicated that HDSC-sEVs could be uptaken by trophoblast cells. HDSC-sEVs could increase the invasiveness and the expression level of N-cadherin of trophoblast cells with elevated phosphorylation of SMAD2 and SMAD3 in the cells. Silencing of N-cadherin could block cell invasion induced by HDSC-sEVs, while knockdown of SMAD2 and SMAD3 could inhibit the upregulation of N-cadherin in trophoblast cells. Taken together, our results suggested a regulatory effect of HDSC-sEVs in the invasion of trophoblast cells, and HDSC-sEVs may be important mediators of trophoblasts during embryo implantation and placentation.

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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.