In Vitro Development of Nuclear Transplantation Bovine Embryos Using In Vitro Fertilized Embryos of Korean Native Heifers

한우 체외수정란을 이용한 핵 이식배의 체외발달에 관한 연구

To improve nuclear transplantation(NT) efficiency and to produce a large scale genetically identical cloned calves, examined the in vitro development capacity after co-culture of bovine oviductal epithelial cells (BOEC) and granulosa cells in TCM-199 supplemented with 10% fetal calf serum (FCS) with early bovine embryos derived from in vitro matured fertilized(IVM-IVF) oocyte. In addition, the age dependence of IVM oocyte on electro-stimulation and the effective electric voltage on in ivtro development of bovine NT embryos were examined. The results obtained were summerized as follows; 1. The cleavage rates of IVM-IVF bovine embryos in co-culture with bovine oviductal epithelial cells and granulosa cells were not significantly different(P<0.05), but the developmental rate into morula and blastocyst stage were different showing 38.3 and 20.2%, respectively. 2. The activation (82.5%) and development in vitro(8.6%) into later embryo stages of the aging oocytes of 32 hours post-maturation (hpm) were significantly higher than those of 24 hpm at direct current (DC) voltage of 1.5kV/cm, 60$\mu$sec pulse duration and 1 pulse time. 3. The fusion rates of NT eggs of 32 hpm following to different DC voltages from range 0.75 to 1.5kV/cm were not differ, but the developmental rate into morula and blastocyst stages at DC voltages of 0.75 and 1.0kV/cm were higher(11.4 and 12.6%, respectively) than those of 1.5kV/cm(0%). From these results, it can be suggested the optimal culture system for in vitro culture of IVM-IVF bovine embryos is a co-culture system with BOEC in TCM-199 supplemented 10% FCS. The effective time and the DC voltage for activation, electrofusion and in vitro development of NT embryos derived from IVM-IVF bovine embryo are 32hpm and 0.75~1.0kV/cm. But to improve NT efficiency, the advanced research (cell cycle synchronization, micromanipulation, culture system, etc.) is needed.