101. ISOLATION OF PUTATIVE EMBRYONIC STEM CELLS FROM CLONED PIG EMBRYOS

Abstract

The isolation of embryonic stem cells from cloned embryos (NT-ESC) from domestic animals would have a number of biomedical and agricultural applications. Putative ESC lines from in vivo derived and in vitro produced pig embryos were recently established using a new isolation method¹. The aim of the current study was to determine whether NT-ESC lines could be isolated from cloned pig embryos using this method. To do this we determined initially whether the treatment of embryos with Trichostatin A (TSA), a histone deacetylase inhibitor, could increase the number of cloned embryos that develop to the blastocyst stage because TSA has been shown to increase blastocyst development and NT-ESC isolation efficiencies in mice². Cloned embryos were produced as described previously³. Briefly, in vitro matured sow oocytes were enucleated, fused with adult fibroblasts using an electrical pulse and activated about 1.5 hrs later with a second electrical pulse. Reconstructed embryos were then cultured in modified NCSU23 with or without 50nM TSA treatment for the initial 24 hours of culture. Embryo development was assessed on day 6. Treatment with TSA increased the number of cloned embryos that developed to the blastocyst stage (143/471; 30%) compared with control (54/353; 15%; P < 0.0001). Blastocysts were then plated by mechanical depression onto mitotically inactivated mouse embryonic fibroblast feeder layers in a serum-free culture system on day 7. There was no significant difference in the efficiencies of establishment of homogeneous primary outgrowths between TSA treated (17/96; 18%) and control blastocysts (8/43; 19%). Thirteen homogenous outgrowths from the TSA treated group were vitrified at passage 2 or 3. Sublines are currently being characterised to determine their pluripotency.