The presence of corpus luteum may have a negative impact on in vitro developmental competency of bovine oocytes

Abstract

The aim of the current study was to investigate the effects of the presence or absence of corpus luteum (CL) on in vitro developmental competence of bovine oocytes. In experiment 1, cumulus oocyte complexes (COCs) were collected from slaughterhouse ovaries and divided according to the presence (CL(+) oocytes) or absence (CL(-) oocytes) of a CL in the ovary. Control oocytes (C group) were obtained from ovaries which were not selected toward the presence or absence of CL. All oocytes were submitted to in vitro maturation, fertilization and culture. In experiment 2, the oocytes from the CL(+) and CL(-) ovaries were divided into grown (BCB(+)) and growing (BCB(-)) categories by means of the brilliant cresyl blue (BCB) test. The oocytes from all groups (CL(+)/BCB(+), CL(-)/BCB(+), CL(+)/BCB(-), CL(-)/BCB(-) and control oocytes) were subjected to in vitro embryo production. In experiment 1, the cleavage and blastocyst rates of CL(-) oocytes were higher than those of CL(+) oocytes (83.9% and 43% vs. 69.3% and 22.5%, respectively). In experiment 2, there was less BCB(+) oocytes (more competent oocytes) in the group of CL(+) oocytes than in the group of CL(-) oocytes. Furthermore, developmental competence of all CL(+) oocytes (CL(+)/BCB(+) and CL(+)/BCB(-)) was lower than that of all CL(-) oocytes (CL(-)/BCB(+) and CL(-)/BCB(-)). Thus, the presence of a corpus luteum in the ovary may have negative effects on developmental competence of ipsilateral oocytes.

Keywords: Blastocyst; Brilliant cresyl blue; Cleavage; Corpus luteum; Cumulus oocyte complexes.