Effect of FH535 on in vitro maturation of porcine oocytes by inhibiting WNT signaling pathway

Treatment of porcine ovarian follicles with tert-butyl hydroperoxide as an ovarian senescence model in vitro

Ovarian aging is the main reason of female reproductive problems. Excessive oxidative stress can induce ovarian senescence and follicular atresia, thereby reducing the reproductive performance. Follicles were divided into five groups for in vitro culture based on the duration of stimulation with tert-butyl hydroperoxide (t-BHP)-control group and groups 1 h, 2 h, 6 h, and 12 h. The results revealed that the ratio of progesterone (P4) to estradiol (E2) was increased after 24 and 36 h of follicle culture, shifting follicles toward atresia (P < 0.05). Stimulated by 200 μM t-BHP, follicles showed progressive aging phenotype. Senescence-associated β-galactosidase staining (SA-β-Gal) showed a significant increase in the number of positive cells (P < 0.05). Reactive oxygen species were also significantly upregulated (P < 0.05). t-BHP treatment for 6 h induced significant increases in Caspase 3, P53, and Foxo1 mRNA and protein levels (P < 0.05) and significant decreases in SOD mRNA and protein levels (P < 0.05). Transcriptome sequencing analysis of the follicles showed that the aged and treatment groups were clustered together in hierarchical clustering. Correlation analysis indicated significant changes at the transcriptome level in the treatment groups versus the control group. The common differentially expressed genes in the treatment groups were enriched in three growth-factor signaling pathways associated with cell proliferation and apoptosis (P53, mTOR, and MAPK). In conclusion, induction of follicular senescence by treatment with 200 μM t-BHP for 6 h is an effective in vitro model to simulate ovarian senescence in sows.

Vitrification of bovine germinal vesicle oocytes significantly decreased the methylation level of their in vitro derived MII oocytes

CONTEXT

The vitrification of oocytes is important for the conservation of animals, and the effect of vitrification on methylation patterns of bovine oocytes remains unclear.

AIMS

This article aims to investigate the effect of vitrification on the DNA methylation patterns on vitrified GV oocytes and their in vitro derived MII oocytes.

METHODS

5-MeC staining and single-cell whole genome bisulphite sequencing (SC-WGBS) were utilised to analyse fresh GV oocytes (F_GV group), MII oocytes (F_MII group), vitrified GV oocytes (V_GV group) and their in vitro derived MII oocytes (V_MII group).

KEY RESULTS

Results of both 5-MeC staining and SC-WGBS showed that no significant difference was found between the F_GV group and the V_GV group, while the methylation level of the V_MII group was significantly lower than that of the F_MII group. Moreover, supplementation of 2μM resveratrol (Res) in IVM medium significantly improved maturation and development ability of vitrified GV oocytes by restoring their DNA methylation levels.

CONCLUSION

In conclusion, vitrification of bovine GV oocytes significantly decreased the DNA methylation level of their in vitro derived MII oocytes, and 2μM Res improved their development ability by restoring DNA methylation level.

IMPLICATIONS

Our results provide an efficient approach to improve the maturation and fertilisation ability of vitrified GV oocytes.

Integrated lncRNA and mRNA Transcriptome Analyses in the Ovary of Cynoglossus semilaevis Reveal Genes and Pathways Potentially Involved in Reproduction

Long non-coding RNAs (lncRNAs) have been reported to be involved in multiple biological processes. However, the roles of lncRNAs in the reproduction of half-smooth tongue sole (Cynoglossus semilaevis) are unclear, especially in the molecular regulatory mechanism driving ovarian development and ovulation. Thus, to explore the mRNA and lncRNA mechanisms regulating reproduction, we collected tongue sole ovaries in three stages for RNA sequencing. In stage IV vs. V, we identified 312 differentially expressed (DE) mRNAs and 58 DE lncRNAs. In stage V vs. VI, we identified 1,059 DE mRNAs and 187 DE lncRNAs. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analyses showed that DE mRNAs were enriched in ECM-receptor interaction, oocyte meiosis and steroid hormone biosynthesis pathways. Furthermore, we carried out gene set enrichment analysis (GSEA) to identify potential reproduction related-pathways additionally, such as fatty metabolism and retinol metabolism. Based on enrichment analysis, DE mRNAs with a potential role in reproduction were selected and classified into six categories, including signal transduction, cell growth and death, immune response, metabolism, transport and catabolism, and cell junction. The interactions of DE lncRNAs and mRNAs were predicted according to antisense, cis-, and trans-regulatory mechanisms. We constructed a competing endogenous RNA (ceRNA) network. Several lncRNAs were predicted to regulate genes related to reproduction including cyp17a1, cyp19a1, mmp14, pgr, and hsd17b1. The functional enrichment analysis of these target genes of lncRNAs revealed that they were involved in several signaling pathways, such as the TGF-beta, Wnt signaling, and MAPK signaling pathways and reproduction related-pathways such as the progesterone-mediated oocyte maturation, oocyte meiosis, and GnRH signaling pathway. RT-qPCR analysis showed that two lncRNAs (XR_522278.2 and XR_522171.2) were mainly expressed in the ovary. Dual-fluorescence in situ hybridization experiments showed that both XR_522278.2 and XR_522171.2 colocalized with their target genes cyp17a1 and cyp19a1, respectively, in the follicular cell layer. The results further demonstrated that lncRNAs might be involved in the biological processes by modulating gene expression. Taken together, this study provides lncRNA profiles in the ovary of tongue sole and further insight into the role of lncRNA involvement in regulating reproduction in tongue sole.

17β-estradiol improves the developmental ability, inhibits reactive oxygen species levels and apoptosis of porcine oocytes by regulating autophagy events

OBJECTIVES

Estrogen plays a critical role in the development and apoptosis of oocytes. Autophagy is an evolutionarily conserved and exquisitely regulated self-eating cellular process with important biological functions including the regulation of reproduction. This study aimed to determine the effect of autophagy regulated by the biologically active form of estrogen (17β-estradiol) in porcine oocyte maturation in vitro.

MATERIALS AND METHODS

We measured the effects of oocyte developmental competencies and autophagic activity in the porcine oocyte regulated by 17β-estradiol using autophagic inhibitor (Autophinib). In addition, we studied the role of autophagy in reactive oxygen species (ROS) levels, mitochondrial distribution, Ca²⁺ production, mitochondrial membrane potential (ΔΨm), and early apoptosis by caspase-3, -8 activity in the mature oocytes.

RESULTS

The results showed that the oocyte meiotic progression and early embryonic development were gradually decreased with Autophinib treatment, which was improved by 17β-estradiol. Immunofluorescence experiments revealed that 17β-estradiol primarily could promote the autophagy in the mature oocytes, and block the reduced-autophagic events by Autophinib. Moreover, 17β-estradiol improved the Autophinib induced high ROS levels, abnormal mitochondrial distribution and low Ca²⁺ production in mature oocytes. Analyses of early apoptosis and ΔΨm showed that autophagy inhibition was accompanied by increased cellular apoptosis, and 17β-estradiol reduced apoptosis rates of mature oocytes. Importantly, autophagy was downregulated by treatment with Autophinib, an activation of caspase-8 and cleaved caspase-3 increased. Those effects were abolished by 17β-estradiol, which could upregulate autophagy.

CONCLUSIONS

Our study have showed important implications that 17β-estradiol could promote efficacy of the development of porcine oocytes, enhance the autophagy, reduce ROS levels and apoptosis activity in vitro maturation.

Oocyte IVM or vitrification significantly impairs DNA methylation patterns in blastocysts as analysed by single-cell whole-genome methylation sequencing

To explore the mechanisms leading to the poor quality of IVF blastocysts, the single-cell whole-genome methylation sequencing technique was used in this study to analyse the methylation patterns of bovine blastocysts derived from invivo, fresh (IVF) or vitrified (V_IVF) oocytes. Genome methylation levels of blastocysts in the IVF and V_IVF groups were significantly lower than those of the invivo group (P<0.05). In all, 1149 differentially methylated regions (DMRs) were identified between the IVF and invivo groups, 1578 DMRs were identified between the V_IVF and invivo groups and 151 DMRs were identified between the V_IVF and IVF groups. For imprinted genes, methylation levels of insulin-like growth factor 2 receptor (IGF2R) and protein phosphatase 1 regulatory subunit 9A (PPP1R9A) were lower in the IVF and V_IVF groups than in the invivo group, and the methylation level of paternally expressed 3 (PEG3) was lower in the V_IVF group than in the IVF and invivo groups. Genes with DMRs between the IVF and invivo and the V_IVF and IVF groups were primarily enriched in oocyte maturation pathways, whereas DMRs between the V_IVF and invivo groups were enriched in fertilisation and vitrification-vulnerable pathways. The results of this study indicate that differences in the methylation of critical DMRs may contribute to the differences in quality between invitro- and invivo-derived embryos.

Maternal Cytokines CXCL12, VEGFA, and WNT5A Promote Porcine Oocyte Maturation via MAPK Activation and Canonical WNT Inhibition

Maternal regulatory factors endow the oocyte with developmental competence in vivo, which might be absent in current in vitro maturation (IVM) systems, thereby compromising oocyte quality. In the present study, by employing RNA sequencing data analysis, we expect to identify potential contributing factors to support porcine oocyte maturation through binding to their receptors on the oolemma. Here, C-X-C motif chemokine ligand 12 (CXCL12), vascular endothelial growth factor A (VEGFA), and Wingless-type MMTV integration site family member 5A (WNT5A), termed CVW, are selected and confirmed to be important maternal cytokines for porcine oocyte maturation. Combined supplementation of CVW promotes the nuclear maturation percentage from 57.2% in controls to 75.9%. More importantly, these maternal cytokines improve the developmental potential of matured oocytes by parthenogenesis, fertilization, and cloning, as their blastocyst formation efficiencies and total cell numbers are increased. CVW supplementation also enlarges perivitelline space and promotes cumulus expansion, which results in a more complete transzonal projection retraction on the zona pellucida, and a reduced incidence of polyspermy in fertilized oocytes. Meanwhile, inhibiting the CVW receptor-mediated signaling pathways severely impairs oocyte meiotic resumption and cumulus expansion during IVM. We further determine that maturation improvement by CVW is achieved through activating the MAPK pathway in advance and inhibiting the canonical WNT pathway at the end of the IVM period. These findings provide a new combination of three cytokines to promote the porcine IVM process, which also holds potential to be used in human assisted reproduction technologies as well as in other species.

Baicalin improves IVM of pig oocytes and subsequent preimplantation embryo development by inhibiting apoptosis

Baicalin, a monomer of flavonoids extracted from dried roots of Scutellaria baicalensis, is used to treat female infertility. However, the effect of baicalin on oocyte maturation is unknown. In this study we investigated the effects of baicalin on the IVM of pig oocytes and subsequent embryo development following parthenogenetic activation (PA). We found that 0.1µgmL-1 baicalin significantly (P<0.05) increased the IVM rate of oocytes compared with the non-treatment (control) group by reducing levels of reactive oxygen species (ROS). In addition, the mRNA expression of genes related to nuclear maturation and cumulus cell expansion, mitochondrial membrane potential and ATP content was significantly (P<0.05) higher in baicalin-treated than control oocytes. To determine whether baicalin treatment during IVM of pig oocytes improves subsequent development of PA embryos, we measured the cleavage and blastocyst formation rates, as well as the number of cells per blastocyst. All these parameters were significantly (P<0.05) higher in the baicalin-treated than control group. In conclusion, this study demonstrates that baicalin improves pig oocyte maturation and subsequent embryo development invitro by inhibiting production of ROS and reducing apoptosis in oocytes.

Long non-coding RNA colon cancer-associated transcript 2 may promote esophageal cancer growth and metastasis by regulating the Wnt signaling pathway

The aim of this study was to investigate how long non-coding (lnc)RNA colon cancer-associated transcript 2 (CCAT2) regulates the proliferation, invasion and metastasis of esophageal cancer cells via the Wnt signaling pathway. The expression of lncRNA CCAT2 was quantified by reverse transcription-quantitative PCR in four esophageal cancer cell lines (Eca-109, EC9706, KYSE150 and TE-1) and normal human esophageal epithelial cells (HEECs). The effect of silencing CCAT2 (si-CCAT2) and inhibiting Wnt signaling (using the inhibitor FH535) on the proliferation, migration and invasion of Eca-109 cells was measured by MTT, wound-healing and Transwell invasion assays. Flow cytometry was used to evaluate apoptosis in si-CCAT2 Eca-109 cells. The expression of β-catenin and proliferating cell nuclear antigen (PCNA) proteins was detected by immunohistochemistry. The pro-apoptotic protein Bax, cyclin D1 and Wnt target proteins, including c-Myc and adenomatous polyposis coli (APC), were detected by western blotting. LncRNA CCAT2 was highly expressed in the four esophageal cancer cell lines compared with the HEEC cells. The expression of CCAT2 was significantly decreased in si-CCAT2 Eca-109 cells. Treatment with si-CCAT2 and FH535 alone or in combination significantly inhibited the proliferation, migration and invasion of Eca-109 cells. The treatments also promoted apoptosis, upregulated the expression of Bax and APC proteins, and downregulated β-catenin, PCNA, cyclin D1 and c-Myc proteins. In summary, lncRNA CCAT2 is upregulated in esophageal cancer cells and the knockdown of lncRNA CCAT2 inhibits their proliferation, migration and invasion via the Wnt signaling pathway.