Effects of trichostatin A on in vitro development and transgene function in somatic cell nuclear transfer embryos derived from transgenic Clawn miniature pig cells

Epigenetic reprogramming in cloned mouse embryos following treatment with DNA methyltransferase and histone deacetylase inhibitors

We examined the effects of DNA methyltransferase inhibitor - RG108, and histone deacetylase inhibitor - SAHA, on the reprogramming parameters of cloned mouse embryos produced by somatic cell nuclear transfer into oocytes. The programming parameters studied included dynamics of histone reacetylation, developmental rate, DNA methylation, and transcript levels of genes, all of which are pivotal to lineage specification and blastocyst formation. At the pronuclear stage, somatic nucleus-transplanted oocytes treated with 5 µM SAHA presented higher histone acetylation at H3K9, H3K14, H4K16 and H4K12, compared to untreated clones (p < 0.05). At the morula stage, cloned embryos treated with 5 μM RG108 or 5 μM SAHA presented lower DNA methylation intensity compared to untreated clones (p < 0.05), resembling the intensity levels of fertilized embryos. However, these effects were not observed when RG108 and SAHA were used in combination. The rate of morula formation was significantly higher in cloned embryos treated with 5 µM SAHA than in untreated clones, whereas treatment with RG108 resulted in no obvious effects on morula formation rates. On the other hand, the combined treatment with RG108 and SAHA resulted in inferior rates of cloned morula formation, compared to untreated clones. At the blastocyst stage, the aberrant expression levels of key developmental genes Oct4 and Cdx2, but not Nanog, were corrected in cloned embryos by the treatment with RG108. This is similar to the intensity levels seen in fertilized embryos. The expression of Rpl7l1 gene was significantly higher in embryos treated with both RG108 and SAHA than in untreated and in control groups. In summary, the present study showed that SAHA and RG108, when applied separately, improve the rate and quality of cloned mouse embryos.

Combined Chaetocin/Trichostatin A Treatment Improves the Epigenetic Modification and Developmental Competence of Porcine Somatic Cell Nuclear Transfer Embryos

Developmental defects in somatic cell nuclear transfer (SCNT) embryos are principally attributable to incomplete epigenetic reprogramming. Small-molecule inhibitors such as histone methyltransferase inhibitors (HMTi) and histone deacetylase inhibitors (HDACi) have been used to improve reprogramming efficiency of SCNT embryos. However, their possible synergistic effect on epigenetic reprogramming has not been studied. In this study, we explored whether combined treatment with an HMTi (chaetocin) and an HDACi (trichostatin A; TSA) synergistically enhanced epigenetic reprogramming and the developmental competence of porcine SCNT embryos. Chaetocin, TSA, and the combination significantly increased the cleavage and blastocyst formation rate, hatching/hatched blastocyst rate, and cell numbers and survival rate compared to control embryos. In particular, the combined treatment improved the rate of development to blastocysts more so than chaetocin or TSA alone. TSA and combined chaetocin/TSA significantly reduced the H3K9me3 levels and increased the H3K9ac levels in SCNT embryos, although chaetocin alone significantly reduced only the H3K9me3 levels. Moreover, these inhibitors also decreased global DNA methylation in SCNT embryos. In addition, the expression of zygotic genome activation- and imprinting-related genes was increased by chaetocin or TSA, and more so by the combination, to levels similar to those of in vitro-fertilized embryos. These results suggest that combined chaetocin/TSA have synergistic effects on improving the developmental competences by regulating epigenetic reprogramming and correcting developmental potential-related gene expression in porcine SCNT embryos. Therefore, these strategies may contribute to the generation of transgenic pigs for biomedical research.

Identifying Biomarkers of Autophagy and Apoptosis in Transfected Nuclear Donor Cells and Transgenic Cloned Pig Embryos

In this study, we first investigated the effects of 3-methyladenine (3-MA), an autophagy inhibitor, and the inducer – rapamycin (RAPA) on the incidence of programmed cell death (PCD) symptoms during in vitro development of porcine somatic cell nuclear transfer (SCNT)-derived embryos. The expression of autophagy inhibitor mTOR protein was decreased in porcine SCNT blastocysts treated with 3MA. The abundance of the autophagy marker LC3 increased in blastocysts following RAPA treatment. Exposure of porcine SCNT-derived embryos to 3-MA suppressed their developmental abilities to reach the blastocyst stage. No significant difference in the expression pattern of PCD-related proteins was found between non-transfected dermal cell and transfected dermal cell groups. Additionally, the pattern of PCD in SCNT-derived blastocysts generated using SC and TSC was not significantly different, and in terms of porcine SCNT-derived embryo development rates and total blastocyst cell numbers, there was no significant difference between non-transfected cells and transfected cells. In conclusion, regulation of autophagy affected the development of porcine SCNT embryos. Regardless of the type of nuclear donor cells (transfected or non-transfected dermal cells) used for SCNT, there was no difference in the developmental potential and quantitative profiles of autophagy/apoptosis biomarkers between porcine transgenic and non-transgenic cloned embryos. These results led us to conclude that PCD is important for controlling porcine SCNT-derived embryo development, and that transfected dermal cells can be utilized as a source of nuclear donors for the production of transgenic cloned progeny in pigs.

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.

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.

Effects of histone acetylation status on the early development of in vitro porcine transgenic cloned embryos

The purpose of this study was to investigate the effects of the histone deacetylase (HDAC) inhibitor trichostatin A (TSA) on transgene expression and development of porcine transgenic cloned embryos, specifically focusing on effects derived from TSA-treated donor cells or TSA-treated reconstructed embryos. The results showed that TSA treatment on reconstructed embryos modified the acetylation status, which significantly improved the development of porcine somatic cell nuclear transfer (SCNT) embryos in vitro, but not donor cells. Furthermore, the treatment of reconstructed embryos with TSA enhanced expression of the pluripotency-related gene POU5F1 and stimulated expression of the anti-apoptotic gene BCL-2. Enhanced green fluorescent protein (EGFP) mRNA expression of every group dropped drastically from donor cells to blastocysts. Interestingly, TSA is likely to prevent a decline in EGFP expression in nuclear reprogramming of porcine SCNT embryos. However DNA hypomethylation induced by modified histone acetylation of donor cells treated with TSA was significantly more effective in increasing EGFP expression in SCNT blastocysts. In conclusion, the acetylation status of both donor cells and reconstructed embryos modified by TSA treatment increased transgene expression and improved nuclear reprogramming and the developmental potential of porcine transgenic SCNT embryos.

Embryonic development and gene expression of porcine SCNT embryos treated with sodium butyrate

Incomplete epigenetic modification is one of important reasons of inefficient reprogramming of the donor cell nuclei in ooplasm after somatic cell nuclear transfer (SCNT). It may also underlie the observed reduced viability of cloned embryos. Sodium butyrate (NaBu) is a natural histone deacetylase inhibitor that is produced in the intestine. In the current study, we evaluated the effects of NaBu on preimplantation development, histone acetylation, and gene expression in porcine SCNT embryos. Our results showed that the blastocyst rate (24.88 ± 2.09) of cloned embryos treated with 1.0 mM NaBu for 12 hr after activation was significantly higher (P < 0.05) than that of untreated cloned embryos (13.15 ± 3.07). In addition, treated embryos displayed a global acetylated histone H3 at lysine 14 profile similar to that of in vitro fertilized (IVF) embryos during preimplantation development. Lower levels of Oct4 and Bcl-2, but higher levels of Hdac1, in SCNT embryos at the two-cell and blastocyst stages were observed, compared with those in the IVF counterparts. The four-cell embryos showed no differences in the levels of these genes among IVF embryos or SCNT embryos treated with or without NaBu; however, the levels of Dnmt3b were significantly different. NaBu-treated SCNT embryos showed similar levels of Oct4, Bcl-2, and Dnmt3b as in IVF blastocysts. These results indicated that NaBu treatment in SCNT embryos alters their histone acetylation pattern to provide beneficial effects on in vitro developmental competence and gene expression.

Full-term development of gaur-bovine interspecies somatic cell nuclear transfer embryos: effect of trichostatin A treatment

Trichostatin A (TSA) has previously been used in somatic cell nuclear transfer (SCNT) to improve the cloning efficiency in several species, which led our team to investigate the effects of TSA on the full-term development of bovine SCNT and gaur-bovine interspecies SCNT (gaur iSCNT; gaur somatic cells as donors and bovine oocytes as recipients) embryos. Treatment with 50 nM TSA for 10 h after fusion had no positive effects on the rates of fusion, cleavage, or the development to eight-cell or morula stages in both bovine SCNT and gaur iSCNT embryos. However, TSA treatment significantly enhanced the blastocyst formation rate in bovine SCNT embryos (44 vs. 32-34% in the TSA-treated and TSA-untreated groups, respectively), but had no effects on gaur iSCNT embryos. The fresh blastocysts derived from bovine SCNT and gaur iSCNT embryos (fresh groups), as well as vitrified bovine SCNT blastocysts (vitrified group), were transferred to bovine recipients. We found that TSA treatment increased the pregnancy rates only in recipients receiving fresh bovine SCNT embryos. In recipients receiving TSA-treated bovine SCNT embryos, three cloned calves from the fresh group and twin cloned calves from the vitrified group were delivered; however, no calf was born from the TSA-untreated bovine SCNT embryos. In contrast, one gaur iSCNT calf was born from a recipient receiving blastocysts from the TSA-untreated group. In summary, TSA improved the preimplantation development and pregnancy rates of bovine SCNT embryos, but did not have any beneficial effect on gaur iSCNT embryos. However, one gaur iSCNT calf reached full-term development.

Methylation characteristics and developmental potential of Guangxi Bama minipig (Sus scrofa domestica) cloned embryos from donor cells treated with trichostatin A and 5-aza-2'-deoxycytidine

Summary Reprogramming of DNA methylation in somatic cell nuclear transfer (SCNT) embryos is incomplete, and aberrant DNA methylation patterns are related to the inefficiency of SCNT. To facilitate nuclear reprogramming, this study investigated the effect of treating Guangxi Bama minipig donor cells with trichostatin A (TSA), 5-aza-2'-deoxycytine (5-aza-dC), or combination of TSA and 5-aza-dC prior to nuclear transfer. Analyses showed that there were no major changes in cell-cycle status among all groups. We monitored the transcription of DNMT1, DNMT3a, HDAC1 and IGF2 genes in donor cells. Transcription levels of HDAC1 were decreased significantly after treatment with a combination of TSA and 5-aza-dC, along with a significantly increased level of IGF2 (P < 0.05). Although treatment of donor cells with either TSA or 5-aza-dC alone resulted in non-significant effects in blastocyst formation rate and DNA methylation levels, a combination of TSA and 5-aza-dC significantly improved the development rates of minipig SCNT embryos to blastocyst (25.6% vs. 16.0%, P < 0.05). This change was accompanied by decreased levels of DNA methylation in somatic cells and blastocyst (P < 0.05). Thus in combination with TSA, lower concentrations of 5-aza-dC may produce a potent demethylating activity, and lead to the significantly enhanced blastocyst development percentage of Bama minipig SCNT embryos.

Oxamflatin significantly improves nuclear reprogramming, blastocyst quality, and in vitro development of bovine SCNT embryos

Aberrant epigenetic nuclear reprogramming results in low somatic cloning efficiency. Altering epigenetic status by applying histone deacetylase inhibitors (HDACi) enhances developmental potential of somatic cell nuclear transfer (SCNT) embryos. The present study was carried out to examine the effects of Oxamflatin, a novel HDACi, on the nuclear reprogramming and development of bovine SCNT embryos in vitro. We found that Oxamflatin modified the acetylation status on H3K9 and H3K18, increased total and inner cell mass (ICM) cell numbers and the ratio of ICM∶trophectoderm (TE) cells, reduced the rate of apoptosis in SCNT blastocysts, and significantly enhanced the development of bovine SCNT embryos in vitro. Furthermore, Oxamflatin treatment suppressed expression of the pro-apoptotic gene Bax and stimulated expression of the anti-apoptotic gene Bcl-XL and the pluripotency-related genes OCT4 and SOX2 in SCNT blastocysts. Additionally, the treatment also reduced the DNA methylation level of satellite I in SCNT blastocysts. In conclusion, Oxamflatin modifies epigenetic status and gene expression, increases blastocyst quality, and subsequently enhances the nuclear reprogramming and developmental potential of SCNT embryos.

The effects of 5-aza-2'- deoxycytidine and trichostatin A on gene expression and DNA methylation status in cloned bovine blastocysts

We previously found that treatment of both donor cells and early cloned embryos with combination of 5-aza-2'-deoxycytidine (5-aza-dC) and trichostatin A (TSA) significantly improve the in vitro and full-term development of nuclear transfer (NT) bovine embryos. To investigate how this treatment improved the epigenetic reprogramming of somatic cell nuclei, we compared the expression levels of DNA methylation-, chromatin structure-, and development-related genes in in vitro fertilized (IVF group), NT (C-NT group), and 5-aza-dC and TSA-treated NT (T-NT group) single blastocyst using quantitative real-time PCR. We also compared the DNA methylation status of satellite I among three groups using bisulfite sequencing analysis and combined bisulfite restriction analysis (COBRA). There were significantly lower levels of DNMT1, DNMT3b, HDAC2, and IGF2 transcripts in T-NT blastocysts than in C-NT blastocysts, whereas the relative abundance of OCT4 and SOX2 mRNA was significantly increased in T-NT blastocysts compared to C-NT blastocysts. In addition, the treatment also reduced the DNA methylation levels of NT blastocysts on satellite I sequence. It is likely that TSA may act synergistically with 5-aza-dC to exert such modifications in gene expression and DNA methylation, subsequently enhancing developmental potential (in vitro and full-term) of treated cloned embryos.