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Accumulating evidence suggests that a low pluripotency of donor nuclei might lead to abnormal development of cloned embryos and underlie the inefficiency of mammalian somatic cell nuclear transfer (SCNT). To improve the pluripotency of SCNT embryo, RepSox, a defined small-molecule compound that functions in inhibiting the transforming growth factor β signaling pathway, was used to treat nuclear-transferred porcine oocytes after activation. We found that the developmental ability of porcine SCNT embryos (defined as the blastocyst rate) was significantly increased (13.5% vs. 21.8%) when 25 μm RepSox was added to the porcine embryo culturing system for 14-16 hours after activation. Of note, RepSox treatment significantly increased the transcriptional expression of the pluripotency gene NANOG at the four- and eight-cell stages. Furthermore, according to the TUNEL (TdT-mediated dUTP nick end labeling) staining and expression levels of the apoptosis-regulated gene Caspase 3 and proapoptotic gene Bax, the percentage of apoptotic cells in blastocyst cells was not affected after RepSox treatment. These results indicated that treatment with RepSox enhanced the developmental competence of porcine SCNT embryos through improvements in nuclear pluripotency.

Porcine-derived xenogeneic sources for transplantation are a promising alternative strategy for providing organs for treatment of end-stage organ failure in human patients because of the shortage of human donor organs. The recently developed blastocyst or pluripotent stem cell (PSC) complementation strategy opens a new route for regenerating allogenic organs in miniature pigs. Since the eye is a complicated organ with highly specialized constituent tissues derived from different primordial cell lineages, the development of an intact eye from allogenic cells is a challenging task. Here, combining somatic cell nuclear transfer technology (SCNT) and an anophthalmic pig model ( MITF L 247S/L247S ), allogenic retinal pigmented epithelium cells (RPEs) were retrieved from an E60 chimeric fetus using blastocyst complementation. Furthermore, all structures were successfully regenerated in the intact eye from the injected donor blastomeres. These results clearly demonstrate that not only differentiated functional somatic cells but also a disabled organ with highly specialized constituent tissues can be generated from exogenous blastomeres when delivered to pig embryos with an empty organ niche. This system may also provide novel insights into ocular organogenesis., (© 2018 The Authors. Published under the terms of the CC BY 4.0 license.)

Accumulating evidence suggests that faulty epigenetic reprogramming leads to the abnormal development of cloned embryos and results in the low success rates observed in all mammals produced through somatic cell nuclear transfer (SCNT). The aberrant methylation status of H3K9me and H3K9me2 has been reported in cloned mouse embryos. To explore the role of H3K9me2 and H3K9me in the porcine somatic cell nuclear reprogramming, BIX-01294, known as a specific inhibitor of G9A (histone-lysine methyltransferase of H3K9), was used to treat the nuclear-transferred (NT) oocytes for 14-16 h after activation. The results showed that the developmental competence of porcine SCNT embryos was significantly enhanced both in vitro (blastocyst rate 16.4% vs 23.2%, P<0.05) and in vivo (cloning rate 1.59% vs 2.96%) after 50 nm BIX-01294 treatment. BIX-01294 treatment significantly decreased the levels of H3K9me2 and H3K9me at the 2- and 4-cell stages, which are associated with embryo genetic activation, and increased the transcriptional expression of the pluripotency genes SOX2, NANOG and OCT4 in cloned blastocysts. Furthermore, the histone acetylation levels of H3K9, H4K8 and H4K12 in cloned embryos were decreased after BIX-01294 treatment. However, co-treatment of activated NT oocytes with BIX-01294 and Scriptaid rescued donor nuclear chromatin from decreased histone acetylation of H4K8 that resulted from exposure to BIX-01294 only and consequently improved the preimplantation development of SCNT embryos (blastocyst formation rates of 23.7% vs 21.5%). These results indicated that treatment with BIX-01294 enhanced the developmental competence of porcine SCNT embryos through improvements in epigenetic reprogramming and gene expression., (© 2016 Society for Reproduction and Fertility.)