Submitted February 17, 2004
Returned for revision March 9, 2004
Accepted April 23, 2004
Ovary
Role of Fas-Mediated Apoptosis and Follicle-Stimulating Hormone on the Developmental Capacity of Bovine Cumulus Oocyte Complexes In Vitro
Francisco J Rubio Pomar ,
Bernard A.J. Roelen *,
Karin A Slot ,
Helena T.A. van Tol ,
Ben Colenbrander ,
and
Katja J. Teerds
* To whom correspondence should be addressed. E-mail: b.a.j.roelen{at}vet.uu.nl.
Abstract
Follicular atresia is thought to be largely regulated by apoptosis. To further understand how apoptosis can affect cumulus cells and oocytes we have evaluated the incidence and regulation of apoptosis affecting bovine cumulus oocyte complexes in vitro. Expression of components of the Fas signaling pathway was studied in both oocytes and cumulus cells by polymerase chain reaction after reverse transcription, immunoblotting and indirect immunofluorescence. Furthermore, the Fas signaling pathway was activated in cumulus oocyte complexes with an agonistic anti-Fas antibody during in vitro maturation in the presence or absence of FSH. Viability and incidence of apoptosis in cumulus cells were evaluated by assessing membrane integrity and nuclear morphology. Oocyte nuclear maturation was also analyzed, as well as cleavage rates, blastocyst formation rates and blastocyst quality, following in vitro fertilization. Fas mRNA and protein were expressed both in oocytes and cumulus cells. FasL protein was found in cumulus cells but could not be detected in oocytes, despite its mRNA expression. Both activation of the Fas pathway and presence of FSH during in vitro maturation increased the incidence of apoptosis in cumulus cells, affecting predominantly the middle and peripheral region of the cumulus. The observed increase however had no effect on the developmental competence of the oocytes.
Key words:
Embryo •
Apoptosis •
Cumulus cells •
In vitro fertilization •
Oocyte development
