Oocyte activation and preimplantation development of bovine embryos obtained by specific inhibition of cyclin-dependent kinases

F Perecin,S.C Méo,J.M Garcia,C.L.V Leal

doi:10.1590/s0102-09352007000200002

Abstract

The efficiency of bohemine and roscovitine in combination with ionomycin on parthenogenetic activation and initial embryonic development of bovine oocytes was studied. Two experiments were performed: in the first, different concentrations (0, 50, 75 or 100µM) and different exposure periods (2, 4 or 6 hours) to bohemine or roscovitine were tested for activation rates of in vitro matured (IVM) bovine oocytes, which were pre-exposed to ionomycin. The best treatments, 75µM bohemine and 50µM roscovitine, both for 6h, were used in the second experiment, in which IVM bovine oocytes were exposed to ionomycin, followed or not by bohemine or roscovitine treatment, and evaluated for nuclear status, activation rate and blastocyst development were assessed. The combined treatments (ionomycin + cyclin-dependent kinases inhibitors - CDKIs) showed better results for activation rates (77.3%) and initial embryonic development (35.2%) than the single ionomycin treatment (69.4% for activation and 21.9% for development); and also lead to a more uniform activation (nearly 90% single pronucleus development). The results showed that CDKIs improve the effects of ionomycin on parthenogenetic activation and blastocyst development in bovine oocytes and could help to achieve more efficient activation protocols, increasing the developmental competence of embryos obtained by reproductive biotechniques.

Highlights

Bovine oocytes are ovulated in the metaphase II (MII) stage
The control of bovine oocyte parthenogenetic activation leads to a better understanding of technical and biological factors involved in parthenogenesis and embryonic development
In order to evaluate the efficiency of bohemine and roscovitine in combination with ionomycin on parthenogenetic activation and initial embryonic development of bovine oocytes, two experiments were performed

Summary

Introduction

Bovine oocytes are ovulated in the metaphase II (MII) stage At this moment, they are unable to start development if not fertilized by a spermatozoon or parthenogenetically activated. The interest in studying parthenogenetic activation mechanisms has increased due to the development of embryo biotechnologies, such as cloning by nuclear transfer (Cibelli et al, 1998; Wells et al, 1999) and intracytoplasmic sperm injection (ICSI) experiments (Suttner et al, 2000). These procedures require simple and efficient systems to promote oocyte activation. It generates an adequate model to study some aspects of early embryonic development, such as, the influence of ploidy and imprinted genes on animal development (Solter, 1988)

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