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Effect of pre-maturation with C-type Natriuretic Peptide and 3-Isobutyl-1-methylxanthine on cumulus-oocyte communication and oocyte developmental competence in cattle

Soto-Heras, Sandra, Paramio, Maria-Teresa, Thompson, Jeremy
Animal reproduction science 2019
blastocyst, cattle, embryogenesis, follicular development, germinal vesicle, meiosis, mitochondria, natriuretic peptides
In vitro embryo production depends on normal oocyte competence, which is acquired during folliculogenesis, involving cytoplasmic and nuclear processes. In vitro maturation (IVM) induces spontaneous resumption of meiosis, preventing full competence acquisition. The incorporation of a pre-IVM phase with supplementation with C-type natriuretic peptide (CNP) and 3-Isobutyl-1-methylxanthine (IBMX) was used with the aim of improving the developmental competence of cattle oocytes. In a preliminary experiment, COCs were cultured with increasing CNP concentrations and nuclear stage assessment was performed. Supplementation with both 100 and 200 nM CNP resulted in greater germinal vesicle (GV) development rates at 6 h of culture than those with the control group (79.3%, 76.4% and 59.2%, respectively). In a second experiment, use of 100 nM CNP plus 500 µM IBMX resulted in retention of more oocytes in the GV stage (92.0%) at 6 h of culture compared to supplementation with either CNP or IBMX alone (74.8% and 86.7%, respectively). There was subsequent assessment of the effect of the pre-IVM system (6-h of culture with CNP plus IBMX), on COC development, followed by 20-h of IVM, with comparison to the control at 24-h of IVM. Blastocyst development rate was greater after the pre-IVM phase (45.1% compared with 34.5%). The inclusion of the pre-IVM phase also resulted in an enhanced mitochondrial activity in matured oocytes and sustained integrity of transzonal projections for longer after IVM. In conclusion, CNP and IBMX function synergistically to arrest meiosis in cattle oocytes during a pre-IVM phase, which improves cumulus-oocyte communication and embryo development.