Use of NPPC, folicular fluid and BMP15 to modulate oocyte meiotic arrest on in vitro maturation: effects on cumulus-oocyte complexes and bovine embryo production

Abstract

Studies in mice demonstrated that C-type natriuretic peptide precursor (NPPC) and its receptor type 2 (NPR2) are essential for the maintenance of meiotic arrest in the oocyte. Paracrine factors secreted by the oocyte (such as bone morphogenetic protein or BMP15), seem to modulate the system stimulating NPR2 gene expression in cumulus cells. Consequently, the NPPC, NPR2 and BMP15 system arises as a critical mechanism controlling oocyte meiosis resumption in vitro, potentially applicable in the bovine species. Recently, in bovine model, oocyte nuclear maturation was delayed when maturation media was supplemented with bovine follicular fluid (bFF) and, consequently, embryo production in vitro was improved. However, the causative factors present in the bFF responsible for the delay are not known. Estradiol (a component of bFF) directly stimulates NPR2 in the cumulus cells. Therefore, the objective of this project is to characterize bovine oocyte meiosis in vitro through modulation of NPPC NPR2, BMP15, bFF and estradiol. Specifically, we aim to: 1) detect NPPC and its receptor NPR2 in bovine ovarian follicle, 2) assess the effects of bFF, estradiol and NPPC on nuclear maturation and in vitro production of embryos, and 3) evaluate the effects of BMP15 on the oocyte meiotic arrest. (AU)