Reproduction Abstracts

Introduction: Oocytes acquire developmental competence with progressive folliculogenesis. Cumulus–oocyte complexes (COCs) from small antral follicles are commonly used in IVM but have inherent low competence and are poorly responsive to amphiregulin (AREG) which normally mediates oocyte maturation. Here we examined effects of bone morphogenetic protein 15 (BMP15), growth differentiation factor 9 (GDF9), and dbcAMP on the maturation and subsequent developmental competence of oocytes derived from small follicles in AREG-induced IVM.

Materials and methods: Gilt COCs were aspirated from 2 to 4 mm follicles and cultured in porcine oocyte medium supplemented with 100 ng/ml AREG, ±1 mmol/l dbcAMP, ±100 ng/ml pro-mature human GDF9, ±100 ng/ml pro-mature human BMP15 for 22 h and then in additive-free medium for an additional 22 h. Following IVM, chromosome configurations, developmental competence and mRNA of matrix related genes were determined. Phosphorylation of ERK1/2 (pERK1/2) in COCs was assessed 1 h following AREG-stimulation.

Results and discussion: In AREG-induced IVM, the addition of dbcAMP+BMP15+GDF9 increased the rate of nuclear maturation and blastocyst formation compared to BMP15+GDF9 alone. Furthermore, the combination of BMP15+GDF9 and dbcAMP enabled AREG-stimulated cumulus expansion because of increased matrix related genes such as HAS2, TNFIPA6 and PTGS2. Additionally, the combination enhanced pERK1/2. An EGF receptor phosphorylation inhibitor decreased nuclear maturation and blastocyst formation rates in the IVM combinational treatment. These results indicate that BMP15+GDF9 and dbcAMP may synergistically promote EGF receptor signaling stimulated by AREG in small follicle derived COCs, resulting in enhanced developmental competence of oocytes that are otherwise developmentally compromised.