Effects of oocyte source, cell origin, and embryo reconstruction procedures on in vitro and in vivo embryo survival after goat cloning

ABSTRACT

The birth of cloned goats has been well documented, but the overall goat cloning efficiency by somatic cell nuclear transfer procedures is still low, which may be further intensified in extreme environments. The aim of this study was to produce cloned goats under the conditions of the Brazilian Semi Arid region, in a transgenic program for the expression of human lysozyme in the milk to target childhood diarrhea and malnutrition, comparing the effects of oocyte source, cell type, and embryo reconstruction procedures on in vitro and in vivo embryo survival after cloning by micromanipulation or by handmade cloning. The use of in vitro-matured oocytes resulted in more viable embryos after cloning than in vivo-matured cytoplasts, but no differences in pregnancy rates on day 23 were seen between oocyte sources (77.5 vs. 77.8%, respectively). The presence or absence of the zona pellucida for embryo reconstruction (78.8 vs. 76.0%, respectively) did not affect pregnancy outcome after transfer. However, pregnancy rate on day 23 was higher for embryos chemically activated by a conventional than a modified protocol (88.1 vs. 50.0%), and for embryos reconstructed with mesenchymal stem cells and fetal fibroblasts (100.0 and 93.3%) than with adult fibroblasts (64.7%). Although most pregnancies were lost, the birth of a cloned female was obtained from embryos reconstructed by micromanipulation using non-transgenic control cells and in vitro-matured oocytes with intact zona pellucida, after conventional activation and transfer at the 1-cell stage.