Artificial Meiotic Arrest and Parthenogenetic Activation of Buffalo Oocytes Using Cycloheximide

Abstract

Summary Maintaining oocytes at germinal vesicle (GV) stage without damaging their quality would allow synchronization of maturation and homogenization of the oocyte population. Activation of the oocyte is very important for a number of oocyte or embryo related technologies including intracytoplasmic sperm injection and cloning by nuclear transfer. This work will focus on induction of meiotic inhibition and oocyte activation by cycloheximide (CHX), in buffalo. For this purpose 2 experiments were conducted. In experiment I, buffalo cumulus-oocyte complexes (COCs) were cultured in 100 ml droplets of tissue culture medium 199 enriched with 10% v/v fetal calf serum, FSH and LH (0, 05 iu/ml, PERGOVET 75, Serono, Rome, Italy) and 50 mg/ml gentamycin for 24-26 h at 38.5°C in 5% CO 2 and humidified air for 24 h in the presence of 2 mg/ml CHX. COCs were significantly blocked at the GV stage (20.85% vs. 82.72% in control). Reversibility of the CHX effect was assessed by culturing COCs an additional 24 h in CHX-free culture medium. About 65.0% of treated oocytes (control 80.1%) resumed meiosis and progressed to the MII stage. In experiment II, buffalo oocytes were activated by 10 mM calcium ionophore A23187 for 5 min followed by 10 mg/ml CHX for 3 h. Control oocytes were exposed to conventional in vitro fertilization (IVF) in BO medium. After 48 h of culture, significantly more oocytes (pϽ0.05) were cleaved in the IVF group than in treated group and spontaneous activated one. In conclusion, CHX can be used to block spontaneous resumption of meiosis in buffalo oocytes and its effect is reversible. Also, CHX in combination with calcium ionophore have the ability to induce parthenogenetic activation in buffalo oocytes.