Presence of cumulus cells during in vitro fertilization protects the bovine oocyte against oxidative stress and improves first cleavage but does not affect further development

A. Nader Fatehi a1, Bernard A.J. Roelen a1c1, Ben Colenbrander a1, Eric J. Schoevers a1, Bart M. Gadella a1a2, Mart M. Bevers a1 1 and Rob van den Hurk a1
a1 Department of Farm Animal Health, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands.
a2 Department of Biochemistry and Cell Biology, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands.

Article author query
fatehi an   [PubMed][Google Scholar] 
roelen ba   [PubMed][Google Scholar] 
colenbrander b   [PubMed][Google Scholar] 
schoevers ej   [PubMed][Google Scholar] 
gadella bm   [PubMed][Google Scholar] 
bevers mm   [PubMed][Google Scholar] 
van den hurk r   [PubMed][Google Scholar] 


The present study was conducted to evaluate the function of cumulus cells during bovine IVF. Oocytes within cumulus–oocyte complexes (COCs) or denuded oocytes (DOs) were inseminated in control medium, or DOs were inseminated in cumulus cell conditioned medium (CCCM). DOs exhibited reduced cleavage and blastocyst formation rates when compared with intact COCs. The reduced blastocyst formation rate of DOs resulted from reduced first cleavage but subsequent embryo development was not changed. Live-dead staining and staining for apoptotic cells revealed no differences in blastocysts from oocytes fertilized as COC or DO. Fertilization of DOs in CCCM partially restored the cleavage rate, suggesting that factors secreted by cumulus cells are important for fertilization but that physical contact between oocytes and cumulus cells is required for optimal fertilization and first cleavage. Exposure of COCs to hydrogen peroxide shortly before fertilization reduced the cleavage rate, but did not lead to enhanced death of cumulus cells or oocyte death. Exposure of DOs to hydrogen peroxide, however, resulted in oocyte death and a complete block of first cleavage, suggesting that cumulus cells protect the oocyte against oxidative stress during fertilization.

(Received December 15 2004)
(Accepted January 25 2005)

Key Words: Blastocyst; Bovine; IVF; Oxidative stress.

c1 All correspondence to: B.A.J. Roelen, Department of Farm Animal Health, Yalelaan 7, 3584 CL, Utrecht, The Netherlands Tel: +31 30 2533352. Fax: +31 30 2534811. e-mail: b.a.j.roelen@vet.uu.nl


1 Deceased.