Recombinant human activin A promotes development of bovine somatic cell nuclear transfer embryos matured in vitro

To improve the culture system of bovine somatic cell nuclear transfer (SCNT) embryos, we studied the effects of activin A on developmental competence of bovine SCNT embryos during the early development stage based on the traditional culture method, and analyzed the expression level of the genes related to blastocyst hatching (Na/K-ATPase, Glut-1) and related to activin A signalling pathway (ActRII and Smad2). We generated the bovine SCNT embryo using a Holstein cow oocyte as recipient cytoplasm and a foetal ear fibroblast (Holstein cow, 120 days) as donor cell. The embryos were cultured as follows: experiment 1, the addition of activin A at the concentrations of 0 (control), 20 (M1-20), 40 (M1-40) or 80 ng/ml (M1-80) to the media during the first three days and no addition during the subsequent 5 days; experiment 2, no addition of activin A to the media during the first 3 days and the addition of activin A at the concentrations of 0 (control), 20 (M2-20), 40 (M2-40) or 80 ng/ml (M2-80) during the subsequent 5 days. The results indicated that the blastocyst formation rate and hatching rate, and total blastomere numbers as well as ICM/TE obtained in experiment 1 were not significantly different from the control group (P > 0.05). In contrast, these values obtained in experiment 2 were significantly higher than in the control group (P < 0.05). In addition, the relative abundance (ratio to GAPDH mRNA) of each gene (Glut-1, ActR II and Smad2) was not significantly different among the treatments in the experiment. The expression levels of 4 genes (Na/K-ATPase, Glut-1, ActR II and Smad2) in blastocysts obtained in experiment 2 were higher than those obtained in experiment 1. In conclusion, the present study suggests that the addition of activin A to the culture media from day 4 to day 8 can enhance the developmental competence of bovine SCNT embryos.