Effects of trichostatin A on histone acetylation and methylation characteristics in early porcine embryos after somatic cell nuclear transfer

Enhancement of Chromatin and Epigenetic Reprogramming in Porcine SCNT Embryos—Progresses and Perspectives

Over the last 25 years, cloned animals have been produced by transferring somatic cell nuclei into enucleated oocytes (SCNT) in more than 20 mammalian species. Among domestic animals, pigs are likely the leading species in the number of clones produced by SCNT. The greater interest in pig cloning has two main reasons, its relevance for food production and as its use as a suitable model in biomedical applications. Recognized progress in animal cloning has been attained over time, but the overall efficiency of SCNT in pigs remains very low, based on the rate of healthy, live born piglets following embryo transfer. Accumulating evidence from studies in mice and other species indicate that new strategies for promoting chromatin and epigenetic reprogramming may represent the beginning of a new era for pig cloning.

TSA Activates Pluripotency Factors in Porcine Recloned Embryos

Animal cloning is of great importance to the production of transgenic and genome-edited livestock. Especially for multiple gene-editing operations, recloning is one of the most feasible methods for livestock. In addition, a multiple-round cloning method is practically necessary for animal molecular breeding. However, cloning efficiency remains extremely low, especially for serial cloning, which seriously impedes the development of livestock breeding based on genome editing technology. The incomplete reprogramming and failure in oocyte activation of some pluripotent factors were deemed to be the main reason for the low efficiency of animal recloning. Here, to overcome this issue, which occurred frequently in the process of animal recloning, we established a reporter system in which fluorescent proteins were driven by pig OCT4 or SOX2 promoter to monitor the reprogramming process in cloned and recloned pig embryos. We studied the effect of different histone deacetylase (HDAC) inhibitors on incomplete reprogramming. Our results showed that Trichostatin A (TSA) could activate pluripotent factors and significantly enhance the development competence of recloned pig embryos, while the other two inhibitors, valproic acid (VPA) and Scriptaid, had little effect on that. Furthermore, we found no difference in OCT4 mRNA abundance between TSA-treated and untreated embryos. These findings suggest that TSA remarkably improves the reprogramming state of pig recloned embryos by restoring the expression of incompletely activated pluripotent genes OCT4 and SOX2.

Effects of PXD101 and Embryo Aggregation on the In Vitro Development of Mouse Parthenogenetic Embryos

To improve the isolation efficiency of parthenogenetic embryonic stem cells (pESCs) in mice, it is necessary to optimize the method to increase in vitro developmental competence of mice parthenogenetic blastocysts. Therefore, this study aims to investigate an optimal method for the production of mouse parthenogenetic blastocysts and isolation of pESC colonies by comparing the effects of two methods: (1) the treatment of histone deacetylase inhibitor PXD101 before, during, or after parthenogenetic activation; (2) parthenogenetic embryo aggregation; and (3) their combination treatment. The results suggest that application of PXD101 treatment and embryo aggregation could both improve the development of mouse parthenogenetic blastocysts (50 nM PXD101 treated 4 hours during activation and further 4 hours after activation: 40.0% vs. 20.0%; p < 0.05; two-cell embryo aggregation: 38.3% vs. 20.0%; p < 0.05) and also enhance the isolation rate of pESC colonies (PXD101: 33.3% vs. 11.8%; p < 0.05; two-cell embryo aggregation: 36.4% vs. 11.8%; p < 0.05). The combination of their treatments had the higher rate of parthenogenetic blastocyst development (41.7%) and significantly higher rate of pESC colony isolation from parthenogenetic blastocysts (45.0%); therefore, we concluded that the combination of these two methods (50 nM PXD101 treated for 8 hours and then aggregated at two-cell stage with 0.25% pronase for 10 minutes in our self-made concave) is considered the optimal way for the in vitro development of parthenogenetic blastocysts and subsequent pESC colony isolation in mice, opening new opportunities for application of this combination method to improve the parthenogenetic embryo development in other species.

Strategies for improvement of cloning by somatic cell nuclear transfer

Somatic cell nuclear transfer (SCNT) is a powerful tool that is being applied in a variety of fields as diverse as the cloning and production of transgenic animals, rescue of endangered species and regenerative medicine. However, cloning efficiency is still very low and SCNT embryos generally show poor developmental competency and many abnormalities. The low efficiency is probably due to incomplete reprogramming of the donor nucleus and most of the developmental problems are thought to be caused by epigenetic defects. Applications of SCNT will, therefore, depend on improvements in the efficiency of production of healthy clones. This review has summarised the progress and strategies that have been used to make improvements in various animal species, especially over the period 2010–2017, including strategies based on histone modification, embryo aggregation and mitochondrial function. There has been considerable investiagation into the mechanisms that underpin each strategy, helping us better understand the nature of genomic reprogramming and nucleus–cytoplasm interactions.

Improved early development of porcine cloned embryos by treatment with quisinostat, a potent histone deacetylase inhibitor

Recently, the modification of the epigenetic status of somatic cell nuclear transfer (SCNT) embryos by treatment with histone deacetylase inhibitors (HDACis) has made it possible to alter epigenetic traits and improve the developmental competence of these embryos. In the current study, we examined the effects of an HDACi, quisinostat (JNJ), on the in vitro development of porcine cloned embryos and their epigenetic nuclear reprogramming status. SCNT embryos were cultured under various conditions, and we found that treatment with 100 nM JNJ for 24 h post activation could improve blastocyst formation rates compared to the control (P < 0.05). Therefore, this was chosen as the optimal condition and used for further investigations. To explore the effects of JNJ on the nuclear reprogramming of early stage embryos and how it improved cloning efficiency, immunofluorescence staining and quantitative real-time PCR were performed. From the pseudo-pronuclear to 2-cell stages, the levels of acetylation of histone 3 at lysine 9 (AcH3K9) and acetylation of histone 4 at lysine 12 (AcH4K12) increased, and global DNA methylation levels revealed by anti-5-methylcytosine (5-mC) antibody staining were decreased in the JNJ-treated group compared to the control (P < 0.05). However, JNJ treatment failed to alter AcH3K9, AcH4K12, or 5-mC levels at the 4-cell embryo stage. Moreover, JNJ treatment significantly upregulated the expression of the development-related genes OCT4, SOX2, and NANOG, and reduced the expression of genes related to DNA methylation (DNMT1, DNMT3a, and DNMT3b) and histone acetylation (HDAC1, HDAC2, and HDAC3). Together, these results suggest that treatment of SCNT embryos with JNJ could promote their developmental competence by altering epigenetic nuclear reprogramming events.

Effects of trichostatin A on pig SCNT blastocyst formation rate and cell number: A meta-analysis

Although somatic cell nuclear transfer (SCNT) can be used to create transgenic pigs for human xenotransplantation, low efficiency limits its use. Trichostatin A (TSA) promotes SCNT embryo development, but whether TSA modifies SCNT blastocyst numbers is unclear. Thus, there is an urgent need to understand whether TSA modifies the rate and number of embryos that grow from oocytes to blastocysts in culture and what types of cell signaling pathways may be involved. Thus, we identified 63 reports, of which 13 are included in this meta-analysis. Data show that TSA significantly increased the SCNT blastocyst formation rate, but did not change blastocyst cell number. Due to study heterogeneity (I²>50%), we hypothesized that donor cells were of different backgrounds so we analyzed two donor cell subgroups: fetal and adult fibroblasts. Analysis of the fetal fibroblast subgroups showed no heterogeneity, but the adult fibroblast subgroups were heterogeneous, suggesting epigenetic reprogramming of fetal fibroblasts by TSA. Adult fibroblast heterogeneity may be complex and reprogramming by TSA is more difficult. Thus, TSA fibroblasts reprogramming is the source of heterogeneity in this meta-analysis. More work is needed to better understand how TSA influences SCNT pig embryonic development, and histone deacetylase inhibitors can be assessed with respect to SCNT pig embryos. Finally, efforts in epigenetic research may improve SCNT pig embryo outcomes.

Histone deacetylases inhibitors (HDACis) as novel therapeutic application in various clinical diseases

Accumulating evidence suggests that histone hypoacetylation which is partly mediated by histone deacetylase (HDAC), plays a causative role in the etiology of various clinical disorders such as cancer and central nervous diseases. HDAC inhibitors (HDACis) are natural or synthetic small molecules that can inhibit the activities of HDACs and restore or increase the level of histone acetylation, thus may represent the potential approach to treating a number of clinical disorders. This manuscript reviewed the progress of the most recent experimental application of HDACis as novel potential drugs or agents in a large number of clinical disorders including various brain disorders including neurodegenerative and neurodevelopmental cognitive disorders and psychiatric diseases like depression, anxiety, fear and schizophrenia, and cancer, endometriosis and cell reprogramming in somatic cell nuclear transfer in human and animal models of disease, and concluded that HDACis as potential novel therapeutic agents could be used alone or in adjunct to other pharmacological agents in various clinical diseases.

Successful cloning of an adult breeding boar from the novel Chinese Guike No. 1 swine specialized strain

Somatic cloning, also known as somatic cell nuclear transfer (SCNT), is a promising technology which has been expected to rapidly extend the population of elaborately selected breeding boars with superior production performance. Chinese Guike No. 1 pig breed is a novel swine specialized strain incorporated with the pedigree background of Duroc and Chinese Luchuan pig breeds, thus inherits an excellent production performance. The present study was conducted to establish somatic cloning procedures of adult breeding boars from the Chinese Guike No. 1 specialized strain. Ear skin fibroblasts were first isolated from a three-year-old Chinese Guike No. 1 breeding boar, and following that, used as donor cell to produce nuclear transfer embryos. Such cloned embryos showed full in vitro development and with the blastocyst formation rate of 18.4 % (37/201, three independent replicates). Finally, after transferring of 1187 nuclear transfer derived embryos to four surrogate recipients, six live piglets with normal health and development were produced. The overall cloning efficiency was 0.5 % and the clonal provenance of such SCNT derived piglets was confirmed by DNA microsatellite analysis. All of the cloned piglets were clinically healthy and had a normal weight at 1 month of age. Collectively, the first successful cloning of an adult Chinese Guike No. 1 breeding boar may lay the foundation for future improving the pig production industry.

Generation of CD44 gene-deficient mouse derived induced pluripotent stem cells: CD44 gene-deficient iPSCs

Induced pluripotent stem cells (iPSCs) show good promise for the treatment of defects caused by numerous genetic diseases. Herein, we successfully generated CD44 gene-deficient iPSCs using Oct4, Sox2, Klf4, and vitamin C. The generated iPSCs displayed a characteristic morphology similar to the well-characterized embryonic stem cells. Alkaline phosphatase, cell surface (SSEA1, NANOG, and OCT4), and pluripotency markers were expressed at high levels in these cells. The iPSCs formed teratomas in vivo and supported full-term development of constructed porcine embryos by inter-species nuclear transplantation. Importantly, incubation with trichostatin A increased the efficiency of iPSCs generation by increasing the histone acetylation levels. Moreover, more iPSCs colonies appeared following cell passaging during colony picking, thus increasing the effectiveness of iPSCs selection. Thus, our work provides essential stem cell materials for the treatment of genetic diseases and proposes a novel strategy to enhance the efficiency of induced reprogramming.

Effects of trichostatin A on In vitro development and DNA methylation level of the satellite I region of swamp buffalo (Bubalus bubalis) cloned embryos

Trichostatin A (TSA), a histone deacetylase inhibitor, has been widely used to improve the cloning efficiency in several species. This brings our attention to investigation of the effects of TSA on developmental potential of swamp buffalo cloned embryos. Swamp buffalo cloned embryos were produced by electrical pulse fusion of male swamp buffalo fibroblasts with swamp buffalo enucleated oocytes. After fusion, reconstructed oocytes were treated with 0, 25 or 50 nM TSA for 10 h. The results showed that there was no significant difference in the rates of fusion (82–85%), cleavage (79–84%) and development to the 8-cell stage (59–65%) among treatment groups. The highest developmental rates to the morula and blastocyst stages of embryos were found in the 25 nM TSA-treated group (42.7 and 30.1%, respectively). We also analyzed the DNA methylation level in the satellite I region of donor cells and in in vitro fertilized (IVF) and cloned embryos using the bisulfite DNA sequencing method. The results indicated that the DNA methylation levels in cloned embryos were significantly higher than those of IVF embryos but approximately similar to those of donor cells. Moreover, there was no significant difference in the methylation level among TSA-treated and untreated cloned embryos. Thus, TSA treatments at 25 nM for 10 h could enhance the in vitro developmental potential of swamp buffalo cloned embryos, but no beneficial effect on the DNA methylation level was observed.