Parthenogenetic development of in vitro matured porcine oocytes treated with chemical agents

Parthenogenetic activation is a possible way to produce homogeneous embryos with the same ploidy. These embryos could develop to the blastocyst stage during the cultivation. Probably such embryos could be used in other areas of biotechnology. The objectives of the present study were first to assess the ability of strontium-chloride to induce activation and parthenogenetic development in porcine oocytes in comparison with cycloheximide and 6-dimethylaminopurine; second to verify whether the combination of the two treatments improved activation and parthenogenetic development rates. At first, the effects of cycloheximide, 6-dimethylaminopurine and strontium-chloride on oocyte activation and embryonic development were compared. Oocytes from slaughterhouse ovaries were matured for 42h in tissue culture medium (TCM) 199 at 38.5 degrees C, 5% CO(2) in air. Matured oocytes were activated with 10mM strontium-chloride (S), 0.04mM cycloheximide (CX), 2mM 6-dimethylaminopurine (D) for 5h. The activation rate was judged by pronuclear formation of oocytes. Following the activation, oocytes were incubated in NCSU 37 medium for 6 days and in all groups more than 45% of oocytes activated. The activation rate for CX treatment was significantly higher (P<0.05) than for D (57.37+/-4.21% and 48.09+/-3.43%, respectively). In a second experiment in vitro matured porcine oocytes were activated using a combined treatment of strontium-chloride with cycloheximide (SCX) and strontium-chloride combined with 6-dimethylaminopurine (SD). In S and SCX groups more than 50% of oocytes were activated (53.29+/-5.39% and 54.3+/-7.29%, respectively). However a large portion of embryos stopped their development at the two- or four-cell stage. Significantly higher numbers of embryos could reach the eight-cell stage in SD and SCX than for S (7.8+/-1.0%, 7.2+/-4.0% and 3.9+/-3.1%, respectively). Blastocyst formation was only observed in S, CX and SCX. These results show that porcine in vitro matured oocytes can be artificially activated by cycloheximide, 6-dimethylaminopurine and strontium-chloride.