Role of granulosa cell mitogen-activated protein kinase 3/1 in gonadotropin-mediated meiotic resumption from diplotene arrest of mammalian oocytes

Oct-4 activating compound 1 (OAC1) could improve the quality of somatic cell nuclear transfer embryos in the bovine

Previous studies described aberrant nuclear reprogramming in somatic cell nuclear transfer (SCNT) embryos that is distinctly different from fertilized embryos. This abnormal nuclear reprogramming hampers the proper pre- and/or post-implantation development. It has been demonstrated that SCNT blastocysts aberrantly expressed POU5F1 and POU5F1-related genes. With regard to this, it has been postulated that promoting the expression of POU5F1 in SCNT embryos may enhance reprogramming in SCNT embryos. In this study, we treated either fibroblast donor cells or SCNT embryos with OAC1 as a novel small molecule that has been reported to induce POU5F1 expression. Quantitative results from the MTS assay revealed that lower concentrations of OAC1 (1, 1.5, and 3 μM) are non-toxic after 2, 4, and 6 days, but higher concentrations (6, 8, 10, and 12 μM) are toxic and reduced the proliferation of cells after 6 days. No enhancement in the expression of endogenous POU5F1 was observed when both mouse and bovine fibroblast cells were treated with 1.5 and 3 μM OAC1 for up to 6 consecutive days. Subsequently, we treated either fibroblast as donor cells in the SCNT procedure (BFF-OAC1 group) or SCNT embryos [for 4 days (IVC-OAC1: D4-D7 group) or 7 days (IVC-OAC1: D0-D7 group)] with 1.5 μM OAC1. We observed that neither treatment of fibroblast donor cells nor SCNT embryos improved the cleavage and blastocyst rates. Interestingly, we observed that treatment of SCNT embryos all throughout the in vitro culture (IVC) (IVC-OAC1: D0-D7) with 1.5 μM OAC1 improves the quality of derived blastocyst which was indexed by morphological grading, blastomere allocation, epigenetic marks and mRNA expression of target genes. In conclusion, our results showed that supplementation of IVC medium with 1.5 μM OAC1 (D0-D7) accelerates SCNT reprogramming in bovine species.

Granulosa secreted factors improve the developmental competence of cumulus oocyte complexes from small antral follicles in sheep

Oocyte in vitro maturation can be improved by mimicking the intra-follicular environment. Oocyte, cumulus cells, granulosa cells, and circulating factors act as meiotic regulators in follicles and maintain oocyte in the meiotic phase until oocyte becomes competent and ready to be ovulated. In a randomized experimental design, an ovine model was used to optimize the standard in vitro maturation media by Granulosa secreted factors. At first, the development capacity of oocyte derived from medium (>4 to 6 mm) and small (2 to ≤4 mm) size follicles was determined. Differential gene expression of granulosa secreted factors and their receptors were compared between the cumulus cells of the two groups. Then, the best time and concentration for arresting oocytes at the germinal vesicle stage by natriuretic peptide type C (CNP) were determined by nuclear staining in both groups. Oocyte quality was further confirmed by calcein uptake and gene expression. The developmental competence of cumulus oocyte complexes derived from small size follicles that were cultured in the presence of CNP in combination with amphiregulin (AREG) and prostaglandin E2 (PGE2) for 24 h was determined. Finally, embryo quality was specified by assessing expressions of NANOG, SOX2, CDX2, OCT4, and TET1. The cumulus oocyte complexes derived from small size follicles had a lower capacity to form blastocyst in comparison with cumulus oocyte complexes derived from medium size follicles. Prostaglandin E receptor 2 and prostaglandin-endoperoxide synthase 2 had significantly lower expression in cumulus cells derived from small size follicles in comparison with cumulus cells derived from medium size follicles. Natriuretic peptide type C increased the percentage of cumulus oocyte complexes arresting at the germinal vesicle stage in both oocytes derived from medium and small follicles. Gap junction communication was also improved in the presence of natriuretic peptide type C. In oocytes derived from small size follicles; best blastocyst rates were achieved by sequential exposure of cumulus oocyte complexes in [TCM+CNP (6 h), then cultured in TCM+AREG+PGE2 (18h)] and [TCM+CNP (6 h), then cultured in conventional IVM supplements+AREG+PGE2 (18h)]. Increased SOX2 expression was observed in [TCM+CNP (6 h), then cultured in TCM+AREG+PGE2 (18h)], while decreased OCT4 expression was observed in [TCM+CNP (6 h), then cultured in conventional IVM supplements+AREG+PGE2 (18h)]. It seems that the natriuretic peptide type C modulates meiotic progression, and oocyte development is probably mediated by amphiregulin and prostaglandin E2. These results may provide an alternative IVM method to optimize in vitro embryo production in sheep and subsequently for humans.