175 ESTABLISHMENT OF PORCINE EMBRYONIC STEM CELL LINE DERIVED FROM IN VIVO BLASTOCYSTS

Abstract

A porcine embryonic stem (ES) cell line was established from an in vivo-flushed blastocyst. The present study evaluated the effectiveness of IVP, parthenotes and in vivo-produced embryos on establishment of an ES cell line. IVP blastocysts were produced from slaughterhouse ovaries based on the previously reported protocols (2000 Theriogenology 54, 787–797) with minor modifications. Parthenote blastocysts were produced by activation of oocytes matured in vitro with electric stimulation of 2 DC pulses at 2.0 kV/cm for 30 μsec in 0.3 M mannitol solution containing 100 μM CaCl₂ and 100 μM MgCl₂ in vivo blastocysts were recovered on Day 7 after AI (Day = 0) by flushing the uterus with D-PBS containing 10% FBS from three females. After removal of zona pellucida with 0.2% pronase, the blastocysts were subjected to immunosurgical treatment with 10% rabbit anti-pig serum to isolate the inner cell mass (ICM) as previously reported (1975 PNAS 72, 5099–5102). The ICM was seeded onto the feeder layer of STO which was inactivated by treatment with 10 μg/mL mitomycin for 2.5 h and cultured in DMEM with 0.1 mM β-mercaptoethanol, 100 IU/mL penicillin, 0.05 mg/mL streptomycin, 0.1 mM MEM non-essential amino-acid, 20 ng/mL rh-bFGF, 40 ng/mL rh-LIF, 0.03 mM adenosine, 0.03 mM guanosine, 0.03 mM cytidine, 0.03 mM uridine, 0.01 mM thymidine, and 15% FBS. The culture was maintained by changing the medium every day after initiation of ICM attachment onto the feeder layer. Any ES-like colonies were individually picked off the feed layer, dissected with 0.25% trypsin-0.02% EDTA for 3–5 min and reseeded on to new STO feed layer. Out of 140 blastocysts (25, in vivo; 55, IVF; 60, parthenotes) used, attaching rates of the ICMs onto the feeder layer were 88% (22/25, in vivo), 56.4% (31/55, IVF), and 58.3% (35/60, parthenotes). A total of 15 primary ES-like colonies was formed in in vivo (3, 12%), IVF (5, 9.1%), and parthenote (7, 11.7%). However, only one ES cell line from in vivo blastocyst was established, which was confirmed as positive by AP activity (Promega, Madison, WI, USA), and was maintained through four passages. In conclusion, for establishment of an ES cell line in pig, the in vivo blastocyst method is superior to currently available methods utilizing IVF or parthenotes.

This work was supported by grant No. 1000520040020000 from Biogreen 21, Republic of Korea.