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  • Author: Sheng Zhang x
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Jing Tong, Shile Sheng, Yun Sun, Huihui Li, Wei-Ping Li, Cong Zhang and Zi-Jiang Chen

Good-quality oocytes are critical for the success of in vitro fertilization (IVF), but, to date, there is no marker of ovarian reserve available that can accurately predict oocyte quality. Melatonin exerts its antioxidant actions as a strong radical scavenger that might affect oocyte quality directly as it is the most potent antioxidant in follicular fluid. To investigate the precise role of endogenous melatonin in IVF outcomes, we recruited 61 women undergoing treatment cycles of IVF or intracytoplasmic sperm injection (ICSI) procedures and classified them into three groups according to their response to ovarian stimulation. Follicular fluid was collected to assess melatonin levels using a direct RIA method. We found good correlations between melatonin levels in follicular fluid with age, anti-Müllerian hormone (AMH) and baseline follicle-stimulating hormone (bFSH), all of which have been used to predict ovarian reserve. Furthermore, as melatonin levels correlated to IVF outcomes, higher numbers of oocytes were collected from patients with higher melatonin levels and consequently the number of oocytes fertilized, zygotes cleaved, top quality embryos on D3, blastocysts obtained and embryos suitable for transplantation was higher. The blastocyst rate increased in concert with the melatonin levels across the gradient between the poor response group and the high response group. These results demonstrated that the melatonin levels in follicular fluid is associated with both the quantity and quality of oocytes and can predict IVF outcomes as well making them highly relevant biochemical markers of ovarian reserve.

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Fei Gao, Jiyu Guan, Limei Liu, Sheng Zhang, Peipei An, Anran Fan, Guangqi Song, Peng Zhang, Tianchuang Zhao, Bo Tang, Xueming Zhang and Ziyi Li

The Wilms' tumour 1 (WT1) gene originally identified as a tumour suppressor associated with WTs encodes a zinc finger-containing transcription factor that is expressed in multiple tissues and is an important regulator of cellular and organ growth, proliferation, development, migration and survival. However, there is a deficiency of data regarding the expression and function of WT1 during oocyte maturation and preimplantation embryonic development. Herein, we sought to define the expression characteristics and functions of WT1 during oocyte maturation and preimplantation embryonic development in pigs. We show that WT1 is expressed in porcine oocytes and at all preimplantation stages in embryos generated by ICSI. We then evaluated the effects of down-regulating WT1 expression at germinal vesicle and early ICSI stages using a recombinant plasmid (pGLV3-WT1-shRNA). Down-regulation of WT1 did not affect oocyte maturation but significantly decreased preimplantation embryonic development and increased apoptosis in blastocysts. These results indicate that WT1 plays important roles in the development of porcine preimplantation embryos.

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Anran Fan, Kuiying Ma, Xinglan An, Yu Ding, Peipei An, Guangqi Song, Lina Tang, Sheng Zhang, Peng Zhang, Wentao Tan, Bo Tang, Xueming Zhang and Ziyi Li

TET1 is implicated in maintaining the pluripotency of embryonic stem cells. However, its precise effects on induced pluripotent stem cells (iPSCs), and particularly on porcine iPSCs (piPSCs), are not well defined. To investigate the role of TET1 in the pluripotency and differentiation of piPSCs, piPSCs were induced from porcine embryonic fibroblasts by overexpression of POU5F1 (OCT4), SOX2, KLF4, and MYC (C-MYC). siRNAs targeting to TET1 were used to transiently knockdown the expression of TET1 in piPSCs. Morphological abnormalities and loss of the undifferentiated state of piPSCs were observed in the piPSCs after the downregulation of TET1. The effects of TET1 knockdown on the expression of key stem cell factors and differentiation markers were analyzed to gain insights into the molecular mechanisms underlying the phenomenon. The results revealed that knockdown of TET1 resulted in the downregulated expression of pluripotency-related genes, such as LEFTY2, KLF2, and SOX2, and the upregulated expression of differentiation-related genes including PITX2, HAND1, GATA6, and LEF1. However, POU5F1, M YC, KLF4, and NANOG were actually not downregulated. Further analysis showed that the methylation levels of the promoters for POU5F1 and M YC increased significantly after TET1 downregulation, whereas there were no obvious changes in the promoters of SOX2, KLF4, and NANOG. The methylation of the whole genome increased, while hydroxymethylation slightly declined. Taken together, these results suggest that TET1 may play important roles in the self-renewal of piPSCs and the maintenance of their characteristics by regulating the expression of genes and the DNA methylation.

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Jin Yu Zhang, Huan Sheng Dong, Reza K Oqani, Tao Lin, Jung Won Kang and Dong Il Jin

Cell-to-cell contact mediated by cell adhesion is fundamental to the compaction process that ensures blastocyst quality during embryonic development. In this study, we first showed that Rho-associated coiled-coil protein kinases (ROCK1 and ROCK2) were expressed both in porcine oocytes and IVF preimplantation embryos, playing different roles in oocytes maturation and embryo development. The amount of mRNA encoding ROCK1 and the protein concentration clearly increased between the eight-cell and morula stages, but decreased significantly when blastocysts were formed. Conversely, ROCK2 was more abundant in the blastocyst compared with other embryonic stages. Moreover, immunostaining showed that ROCK1 protein distribution changed as the embryo progressed through cleavage and compaction to the morula stage. Initially, the protein was predominantly associated with the plasma membrane but later became cytoplasmic. By contrast, ROCK2 protein was localized in both the cytoplasm and the spindle rotation region during oocyte meiosis, but in the cytoplasm and nucleus as the embryo developed. In addition, ROCK2 was present in the trophectoderm cells of the blastocyst. Treatment with 15 μM Y27632, a specific inhibitor of ROCKs, completely blocked further development of early four-cell stage embryos. Moreover, we did not detect the expression of ROCK1 but did detect ROCK2 expression in blastocysts. Moreover, lysophosphatidic acid an activator of ROCKs significantly improved the rates of blastocyst formation. These data demonstrate that ROCKs are required for embryo development to the blastocyst stage. Together, our results indicate that ROCK1 and ROCK2 may exert different biological functions during the regulation of compaction and in ensuring development of porcine preimplantation embryos to the blastocyst stage.

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Jian Zhang, Linlin Hao, Qian Wei, Sheng Zhang, Hui Cheng, Yanhui Zhai, Yu Jiang, Xinglan An, Ziyi Li, Xueming Zhang and Bo Tang

Somatic cell nuclear transfer (SCNT) has been successfully used for cloning in a variety of mammalian species. However, SCNT reprogramming efficiency is relatively low, in part, due to incomplete DNA methylation reprogramming of donor cell nuclei. We previously showed that ten-eleven translocation 3 (TET3) is responsible for active DNA demethylation during preimplantation embryonic development in bovines. In this study, we constructed TET3-overexpressing cell lines in vitro and observed that the use of these fibroblasts as donor cells increased the blastocyst rate by approximately 18 percentage points compared to SCNT. The overexpression of TET3 in bovine SCNT embryos caused a decrease in the global DNA methylation level of the pluripotency genes Nanog and Oct-4, ultimately resulting in an increase in the transcriptional activity of these pluripotency genes. Moreover, the quality of bovine TET3-NT embryos at the blastocyst stage was significantly improved, and bovine TET3-NT blastocysts possessed more total number of cells and fewer apoptotic cells than the SCNT blastocysts, similar to in vitro fertilization (IVF) embryos. Nevertheless, DNA methylation of the imprinting control region (ICR) for the imprinted genes H19-IGF2 in SCNT embryos remained unaffected by TET3 overexpression, maintaining parent-specific activity for further development. Thus, the results of our study provide a promising approach to rectify incomplete epigenetic reprogramming and achieve higher cloning efficiency.

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Liu Shi-fan, Wang Zhong-xing, Yuan Yao-e, Bing Sheng-min, Zhang Bei-zhu, Wu Jin-zhi, Wu Yi-e and Peng Xin-ying

Summary. The concentrations of LH, FSH, prolactin, oestradiol and progesterone in serum were measured daily during the menstrual cycle of 100 normal Chinese women. The cyclic changes in LH, FSH, oestradiol and progesterone were typical of ovulatory cycles in women of other ethnic groups as reported in the literature. The geometric mean of the LH midcycle peak value was 51·64 i.u./l, the FSH mid-cycle peak value was 11 ·52 i.u./l, the preovulatory oestradiol peak was 1229·12 pmol/1, and the progesterone luteal maximum was 53·27 nmol/1. The cyclic changes of prolactin concentrations were irregular: the value at mid-cycle was significantly higher than that at the follicular or luteal phases.

A correlation between the length of the cycle and mean concentrations of LH and oestradiol at different stages throughout the cycle was shown.

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Yun-Kao Cao, Zhi-Sheng Zhong, Da-Yuan Chen, Gui-Xue Zhang, Heide Schatten and Qing-Yuan Sun

The small GTPase Ran controls numerous cellular processes of the mitotic cell cycle. In this experiment, we investigated the localization and possible roles of Ran during mouse oocyte meiotic maturation, fertilization and early cleavage by using confocal laser scanning microscopy, antibody microinjection and microtubule disturbance. The results showed that Ran was localized mainly in the nucleus (except for the nucleolus) in the oocyte, zygote and early embryo. At pro-metaphase of meiosis I, Ran distributed throughout the cell, but predominantly concentrated around the condensed chromosomes. During the completion of meiosis I and meiosis II, it concentrated to the meiotic spindle microtubules except for the midbody region. After sperm penetration, Ran dispersed with the extrusion of the second polar body and gradually concentrated in the male and female pronuclei thereafter. Ran was also observed to exist diffusely in the cytoplasm in prophase; it concentrated at the mitotic spindle, and migrated to the nucleus during early cleavage. Ran’s concentration around the spindle disappeared when microtubule assembly was inhibited by colchicine, while it was concentrated around the chromosomes after microtubule stabilization with taxol treatment. Ran did not display any role in cytokinesis during division when pseudo-cleavage of germinal vesicle-intact oocytes was induced. Anti-Ran antibody microinjection decreased the germinal vesicle breakdown and the first polar body extrusion, and distorted spindle organization and chromosome alignment. Our results indicate that Ran has a cell cycle-dependent localization and may have regulatory roles in cell cycle progression and microtubule organization in mouse oocytes, fertilized eggs and early embryos.

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Shu-Zhen Liu, Li-Juan Yao, Man-Xi Jiang, Zi-Li Lei, Li-Sheng Zhang, Yan-Ling Zhang, Qing-Yuan Sun, Yue-Liang Zheng, Xiang-Fen Song and Da-Yuan Chen

In this study, we investigated the development, the cell number of the blastocyst, and apoptosis in rabbit nuclear transfer (NT) embryos derived from adult fibroblasts and cumulus cells as compared with embryos derived from in vivo fertilization and in vitro culture. The developmental rate and the total cell number of the blastocyst were significantly lower in NT embryos than in fertilized embryos (FEs). The type of donor cells did not affect the embryonic developmental rate and the total cell number of blastocysts in NT groups. The present study investigated the onset and the frequency of apoptosis in NT embryos and FEs by using a terminal deoxynucleotidyl transferase-mediated dUTP nick and labeling (TUNEL) assay. The earliest positive TUNEL signals were detected at the eight-cell stage in NT embryos and at the morula stage in FEs. The apoptotic index of the total blastocysts, the inner cell mass and the trophoderm was greatly higher in the NT embryos than in FEs. Moreover, the apoptotic index of the blastocyst from fibroblasts was significantly higher than that of the blastocyst from cumulus cells.

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Xue-Ying Zhang, Yi-Meng Xiong, Ya-Jing Tan, Li Wang, Rong Li, Yong Zhang, Xin-Mei Liu, Xian-Hua Lin, Li Jin, Yu-Ting Hu, Zhen-Hua Tang, Zheng-Mu Wu, Feng-Hua Yin, Zheng-Quan Wang, Ye Xiao, Jian-Zhong Sheng and He-Feng Huang

Fertilization failure often occurs during in vitro fertilization (IVF) cycles despite apparently normal sperm and oocytes. Accumulating evidence suggests that mitochondria play crucial roles in the regulation of sperm function and male fertility. 3-Nitrophthalic acid (3-NPA) can induce oxidative stress in mitochondria, and melatonin, as an antioxidant, can improve mitochondrial function by reducing mitochondrial oxidative stress. The role of sperm mitochondrial dysfunction in fertilization failure during IVF is unclear. The present study revealed that spermatozoa with low, or poor, fertilization rates had swollen mitochondria, increased mitochondria-derived ROS, and attenuated mitochondrial respiratory capacity. 3-NPA treatment enhanced mitochondrial dysfunction in sperm. Spermatozoa with poor fertilization rates, and spermatozoa treated with 3-NPA, had reduced penetration ability. The concentration of melatonin was decreased in semen samples with low and poor fertilization rates. Melatonin, not only decreased excessive mitochondria-derived ROS, but also ‘rescued’ the reduced penetration capacity of spermatozoa treated with 3-NPA. Taken together, the study suggested that mitochondria-derived ROS and mitochondrial respiratory capacity are independent bio-markers for sperm dysfunction, and melatonin may be useful in improving sperm quality and overall male fertility.