March 2013 (No. 1)
Apoptotic index within cumulus cells is a questionable marker of meiotic competence of bovine oocytes matured in vitro
Ewelina Warzych a,*, Emilia Pers-Kamczyc b, Anna Krzywak a, Stanisława Dudzińska a, Dorota Lechniak a
a Department of Genetics and Animal Breeding, Poznan University of Life Sciences, Poznan, Poland;
b Institute of Dendrology, Polish Academy of Sciences, Kórnik, Poland
Information gained from most human studies indicate a negative correlation between the apoptotic index (AI) in cumulus cells (CC) and the quality of the corresponding oocytes. However, results obtained in other species are not so consistent. The rate of apoptosis-free COCs (cumulus oocytes complexes) subjected to IVM (in vitro maturation) also varies among studies. The aim of the present study was to investigate whether the AI in cumulus cells of post-IVM COCs is related to the morphology of pre-IVM COCs and to meiotic competence of bovine oocytes. COCs of known morphology (four grade scale) obtained from individual follicles were matured in a well-in-drop system. After IVM, the external layers of CC of each COC were analyzed by TUNEL. In order to determine the meiotic stage, oocytes were stained with DAPI. It was found that 25.6% of bovine COCs contained apoptosis-free cumulus cells. Moreover, the majority of COCs with apoptotic cells were characterized by apoptotic index lower than 15%. The level of apoptosis in CC was related neither to COC morphology nor to the oocyte meiotic stage. It is suggested that the extent of apoptosis in cumulus cells is not a reliable quality marker of the corresponding oocyte after IVM.
Reproductive Biology 2013 13 1: 82–87.
* Corresponding author: Department of Genetics and Animal Breeding, Poznan University of Life Sciences, Wolynska 33, 60-637 Poznan, Poland; E-mail address: firstname.lastname@example.org