Production of cloned pigs from in vitro systems

Here we describe a procedure for cloning pigs by the use of in vitro cultur e systems. Four healthy male piglets from two litters were born following n uclear transfer of cultured somatic cells and subsequent embryo transfer. T he initiation of five additional pregnancies demonstrates the reproducibili ty of this procedure. Its important features include extended in vitro cult ure of fetal cells preceding nuclear transfer, as well as in vitro maturati on and activation of oocytes and in vitro embryo culture. The cell culture and nuclear transfer techniques described here should allow the use of gene tic modification procedures to produce tissues and organs from cloned pigs with reduced immunogenicity for use in xenotransplantation.