Comparison of potency between histone deacetylase inhibitors trichostatin A and valproic acid on enhancing in vitro development of porcine somatic cell nuclear transfer embryos.

Epigenetic modification influences reprogramming and subsequent development of somatic cell nuclear transfer (SCNT) embryos. Such modification includes an increase in histone acetylation. Histone deacetylase inhibitors (HDACi), such as trichostatin A (TSA) and valproic acid (VPA), have been known to maintain a high cellular level of histone acetylation. Hence, treatment of nuclear transfer embryos with HDACi may increase the efficiency of cloning. The present study attempted direct comparison of TSA and VPA with regard to the potency of enhancement of in vitro development in porcine SCNT embryos. Reconstructed oocytes using fetal fibroblasts were cultured in PZM-3 containing no HDACi (control), 5 mM VPA, or 50 nM TSA for 24 h, and another 5 d thereafter without HDACi. The frequency of blastocyst formation was significantly higher (P<0.05) in embryos treated with VPA than the frequencies with TSA and without HDACi (125/306, 40.8% vs. 94/313, 30.2% vs. 80/329, 23.4%). In addition, VPA treatment significantly increased (P<0.05) the number of inner cell mass (ICM) cells compared with the control (15.6 ± 1.7 vs. 10.8 ± 2.6), whereas no differences were observed between the TSA treatment and control groups (12.9 ± 3.0 vs. 10.8 ± 2.6). The present study demonstrates that VPA enhances in vitro development of porcine SCNT embryos, particularly by an increase in blastocyst formation and in the number of ICM cells, suggesting that VPA may be more potent than TSA in supporting developmental competence of cloned embryos.