Cloned pigs derived from somatic cell nuclear transfer embryos cultured in vitro at low oxygen tension

Pig cloning has great potential to human xenotransplantation. The present study was designed to establish a more efficient system for producing cloned pigs by somatic cell nuclear transfer (SCNT). Our approach was as follows: SCNT embryos were reconstructed by using fetal fibroblasts of Chinese miniature pig as donors and in vitro matured oocytes of prepubertal gilts as recipients. Reconstructed embryos were induced by electrical fusion/activation and cultured in BSA-containing North Carolina State University 23 medium (NCSU-23) or Porcine Zygote Medium (PZM-3) at the gas condition of 5% CO2, 7% O2, 88% N2. A total of 230 cloned embryos were transferred to three surrogate sows, producing three piglets. One of them is apparently healthy. The clonal provenance of the piglet was indicated by its coat color and confirmed by DNA microsatellite analysis. These results indicate that the use of in vitro matured oocytes from prepubertal gilts as recipient, combined with cloned embryos cultured at low oxygen tension is an effective way to produce cloned pigs.