Meiotic state of bovine oocytes is regulated by interactions between cAMP, cumulus, and granulosa

Abstract

Bovine oocytes are arrested at the prophase of first meiotic cell cycle. Meiosis resumes in oocytes of pre-ovulatory follicles upon LH surge. However, oocytes from secondary follicles spontaneously resume meiosis in the absence of hormones if removed from the follicle and cultured in vitro. The nature of meiotic arrestor in bovine follicles is poorly understood. In this study we investigated the role of cell-cell interactions between granulosa and cumulus cells and the oocyte in mediating maintenance of meiotic arrest by cAMP. We sorted oocytes as granulosa-cumulus oocyte complexes (GCOC) if surrounded with cumulus cells attached to a large granulosa investment or cumulus oocytes complexes (COC) if surrounded with cumulus cells only and investigated the role cAMP in maintenance of meiotic arrest in these oocytes under various conditions. In hormone- and serum-free medium both GCOC and COC enclosed oocytes resumed meiosis. When [cAMP](i) was elevated with addition of invasive adenylate cyclase (iAC) GCOC enclosed oocytes were maintained in the prophase with intact germinal vesicle (GV) while COC enclosed oocytes underwent GV breakdown (GVBD). iAC elevated [cAMP](i) in both types of oocytes to the same level. If oocytes were liberated from the cumulus and granulosa cells, they re-initiated meiosis in serum and hormone free medium, but remained in the GV stage if iAC was added to the medium. Untreated GCOC and COC enclosed oocytes extruded first polar body at the same frequency in hormone-supplemented media. GCOC and COC enclosed oocytes but not denuded oocytes (DO) cultured without somatic cells acquired developmental competence if cultured in hormone-containing medium. It is concluded that maintenance of meiotic arrest is regulated by the interplay of [cAMP](i), and cumulus and granulosa cells.

The effect of pre-maturation culture using phosphodiesterase type 3 inhibitor and insulin, transferrin and selenium on nuclear and cytoplasmic maturation of bovine oocytes

“…Physiological methods, such as culture in follicular fluid (Carolan et al , 1996) and in hemi-sections of follicles (Sirard & Coenen, 1993; Oliveira e Silva et al , 2011), generally are of shorter duration and are less efficient than pharmacological methods. Substances that increase the levels of cAMP, such as inhibitors of phosphodiesterase (PDE) and activators of adenylate cyclase (AC), have been shown to be efficient in inhibiting resumption of spontaneous meiosis in mice (Nogueira et al , 2005), cattle (Aktas et al , 2003; Luciano et al , 2011) and humans (Nogueira et al , 2005). Other drugs, such as 6-dimethylaminopurine (6-DMAP) that acts on meiosis-promoting factor (MPF) and specific inhibitors of cyclin-dependent kinases (CDKs), such as butyrolactone-I and roscovitine, have also been used successfully to maintain oocytes in the GV stage (Dode & Adona, 2001; Adona & Leal, 2004, 2006; Barretto et al , 2011).…”

Gene expression profile of cumulus cells derived from cumulus - oocyte complexes matured either in vivo or in vitro

“…This notion is supported by previous studies in cattle (Fukui and Sakuma 1980;Zhang et al 1995;Fatehi et al 2002) and pigs (Wongsrikeao et al 2005;Maedomari et al 2007) showing that removal of cumulus cells at the beginning of IVM adversely reduced oocyte developmental potential. The cumulus cells not only contribute to cytoplasmic maturation, but may also be involved in the maintenance of meiotic arrest (Aktas et al 2003). It has also been proposed that cumulus cells contribute to oocyte maturation by protecting the oocyte against oxidative stress through enhancement of cytoplasmic glutathione (GSH) synthesis (Yoshida 1993;de Matos et al 1997;Tatemoto et al 2000;Luciano et al 2005) and protein synthesis capability of the oocyte in addition to providing thermoprotection (Edwards and Hansen 1997).…”

Cyclic nucleotide phosphodiesterase 3A–deficient mice as a model of female infertility

“…The interplay of signals arising in both follicle cells and oocytes themselves (1,2,4,6,7) regulates synthesis and degradation of oocyte cAMP via adenylyl cyclases and cyclic nucleotide phosphodiesterases (PDEs), respectively. Cyclic AMP may enter oocytes from adjacent cumulus cells via gap junctions (2,6).…”