| Abstract |
Most of the human oocytes collected after a controlled ovarian stimulation
treatment (using gonadotropins) are at the metaphase II stage (also called
matured oocytes). Nonetheless, approximately 15-20% of collected oocytes
are classified as metaphase I and germinal vesicle stages. These oocytes
are usually discarded due to their reduced developmental competence.
Nevertheless, in cases where a limited number of mature oocytes are
recovered, in vitro maturation may provide an opportunity to increase the
number of oocytes to be fertilized and, therefore, the embryos for
transfer to the patient. Besides its clinical application, these oocytes
represent a potential source both for oocyte maturation and regenerative
medicine applications.
In spite of its possible clinical and research use, maturation conditions
for these type of oocytes (immature and from ovarian stimulation
treatments) have not been optimized yet. In the present study the oocyte's
competence after in vitro maturation under different maturation conditions
has been evaluated. In particular, the following parameters have been
assessed: in vitro maturation rate, spindle configuration/chromosome
organization, mitochondrial DNA copy number and the expression of hormone
and growth factor receptors. In addition, embryo developmental competence
after parthenogenetic activation was evaluated. In order to improve
germinal vesicle oocyte's cytoplasmic competence two different strategies
were tested. On the one hand, oocytes were culture in the presence of
cilostamide, a nuclear maturation inhibitor. On the other hand, a three-
dimensional matrix was created between the oocyte and cumulus cells that
allowed the reconstruction of the cumulus oocyte complex. Furthermore, the
three-dimensional co-culture was supplemented with cilostamide in order to
strengthen both effects. Finally, oocyte competence was determined by its
ability to generate human parthenogenetic embryonic stem cells.
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