Treatment of Donor Cells and Reconstructed Embryos with a Combination of Trichostatin-A and 5-aza-2′-Deoxycytidine Improves the Developmental Competence and Quality of Buffalo Embryos Produced by Handmade Cloning and Alters Their Epigenetic Status and Gene Expression

The application of cloning technology on a large scale is limited by very low offspring rate primarily due to aberrant or incomplete epigenetic reprogramming. Trichostatin A (TSA), a histone deacetylase inhibitor, and 5-aza-2'-deoxycytidine (5-aza-dC), an inhibitor of DNA methyltransferases, are widely used for altering the epigenetic status of cloned embryos. We optimized the doses of these epigenetic modifiers for production of buffalo embryos by handmade cloning and examined whether combined treatment with these epigenetic modifiers offered any advantage over treatment with the individual epigenetic modifier. Irrespective of whether donor cells or reconstructed embryos or both were treated with 50nM TSA + 7.5nM 5-aza-dC, (1) the blastocyst rate was significantly higher (71.6 +/- 3.5, 68.3 +/- 2.6, and 71.8 +/- 2.4, respectively, vs. 43.1 +/- 3.4 for controls, p < 0.05); (2) the apoptotic index was lower (5.4 +/- 1.1, 9.5 +/- 1.0, and 7.4 +/- 1.3, respectively, vs. 19.5 +/- 2.1 for controls, p < 0.05) and was similar to that of in vitro fertilization blastocysts (6.0 +/- 0.8); (3) the global level of H3K18ac was higher (p < 0.01) and that of H3K27me3 lower (p < 0.05) than in controls and was similar among all treatment groups; and (4) the expression level of epigenetic-(HDAC1, DNMT1, and DNMT3a), pluripotency(OCT4 and NANOG), and development-related (FGF4) genes, but not that of SOX2 and CDX2, was similar among all treatment groups. These results demonstrate that similar levels of beneficial effects can be obtained following treatment of either donor cells or reconstructed embryos or both with the combination of TSA +5-aza-dC. Therefore, there is no advantage in treating both donor cells and reconstructed embryos when the combination of TSA and 5-aza-dC is used.