Assessment Of Porcine Oocyte Competence For In Vitro Embryo Production

Natriuretic peptide (NPs) system, brain and C type NPs (BNP and CNP), were involved in the maintenance of porcine oocyte meiotic arrest in porcine. The present study investigated the effects of NPs on developmental competence of immature porcine oocytes in follicles of different sizes.Follicular fluid NP levels were examined by radioimmunoassay. The developmental competence of porcine oocytes was evaluated by cleavage and blastocyst developmental rates after in vitro fertilization(IVF) or parthenogenetic activation (PA) of cumulus oocyte complexes (COCs) recovered from different follicle sizes. NP levels were examined and classified according to the cleavage potential after IVF with COCs coming from such follicles.The BNP and CNP concentrations were increased with follicular size in follicular fluid and were sustained at the set ranges in 3.0-6.0 mm follicles compared to 6.1-8.0 mm follicles. The oocytes developed from 3.0-6.0 mm follicles demonstrated increase in the embryo cleavage and blastocyst ratios after IVF, with an increased follicle size (P<0.05). Moreover, BNP and CNP significantly promoted the blastocyst developmental rates of 3.0-6.0 mm follicles, but could not improve the developmental competence of oocytes from 6.1-8.0 mm follicles due to low NP levels. The COCs from 3.0-4.0 mm follicles pre-incubated in 100 ng/ml of BNP and CNP media for 20h before regular in vitro maturation demonstrated 2 to 3 folds higher developmental competencies in both PA and IVF groups compared to control (P<0.01).The effects of BNP and CNP supplementation in the pre-maturation (PMC) culture media on porcine developmental competence from COCs in follicles of different sizes were different and improved the developmental competence of porcine oocytes from small antral follicle in vitro.We identified GHR gene expression in granulosa cells of different size of follicles, and the expression of GHR was related to the competitiveness of oocytes. We confirmed that GHR can reflect on the developmental competence of porcine oocyte as markers.