Effect of cyclic adenosine monophosphate on In Vitro maturation and cumulus expansion of pig oocytes

Abstract

In other to synchronize the pool of collected porcine oocytes for in vitro maturation (IVM) to produce good mature oocyte supporting for in vitro fertilization (IVF) and enhance the developmental competence of embryo, dibutyryl cAMP (dbcAMP) was added to the IVM medium. This study investigated the effect of dbcAMP on two parameters, meiotic competence, and cumulus expansion rate. Fully grown porcine oocytes were matured in standard IVM, bicarbonate-buffered TCM-199 supplemented with 10% (v/v) fetal bovine serum, 0.1 IU/ml human chorionic gonadotropin, 0.1 mg/ml sodium pyruvate, and 10% (v/v) porcine follicular fluid as the control group. Two concentrations of dbcAMP, 0.5mM, and 1mM were added to the standard IVM during the first 20-22 hours of culturing for transient blocking of meiosis as +dbcAMP 0.5mM and +dbcAMP 1mM group respectively. We also established an IVF system using three kinds of medium Fert-TALP, Pig-FM, and mTBM. The group of +dbcAMP 1mM showed the best effect on the cumulus expansion rate (68.43%) compared with control group without dbcAMP and +dbcAMP 0.5 mM (42.01% and 50.49%, respectively). However, there was no significant difference in the meiotic competence between groups (P>0.05). After the establishment of IVF, we can obtain normal pronucleus (monospermy) in some embryo with decondensed chromatin at 6-10 hours after IVF, condensed chromatin at 14-16 hours after IVF and metaphase at 18-20 hours after IVF. The abnormal fertilization, polyspermy and sperm arrested, was also observed. These findings make a contribution to a better understanding of the effect of dbcAMP to pig oocyte maturation which is essential to develop an in vitro fertilization system with the higher normal embryo rate. Keywords: porcine, oocyte, in vitro maturation, in vitro fertilization, cAMP, cumulus expansion