IN VITRO MATURATION OF SHEEP OOCYTES AS AFFECTED BY HORMONES, SERUM AND EPIDERMAL GROWTH FACTOR

ABSTRACT
The present study was designed to evaluate the effects of hormonal additives (FSH 10
IU/ ml, LH 10 IU/ ml and 17 β Estradiol 1 μg/ ml) and serum additives (10% Estrous ewes
serum (EES) or 10% Fetal calf serum (FCS)) on oocyte cumulus cells expansion and the
percentage of nuclear maturation of sheep oocytes. The effects of adding different
concentrations of epidermal growth factor (EGF) (10, 20 and 40 ng/ml) to the tissue culture
medium (TCM-199) with hormonal and serum additives on oocyte cumulus cells expansion and
percentage of nuclear maturation of sheep oocytes was also examined. The obtained results
showed that the highest percentage of oocytes with complete cumulus cells expansion was
obtained with adding EES to the medium alone or with hormones additives (83.33% and
74.36%, respectively for class A oocytes). Whereas, TCM-199 supplemented with hormones
and EES achieved the highest percentage (51.85 %) of class B oocytes with complete cumulus
cells expansion. Significant differences between the treatment groups of class A and B oocytes
were found (P<0.001). The highest percentage of mature oocytes (MII stage) was achieved from
oocytes cultured in TCM-199 + (FSH, LH and 17 β Estradiol) + EES, (53.85 % and 42.59 % for
class A and B oocytes, respectively).
EGF supplementation increased the percentage of class A oocytes with complete
cumulus cells expansion for the different concentrations, 10, 20, 40 ng/ml (75.68 %, 75.68 %
and 73.68 %, respectively). These values reduced considerably for class B oocytes. The
differences between concentrations of EGF were not significant for oocytes class A and B.
Incubation of oocytes cultured in TCM-199 + 40 ng EGF achieved the highest percentage of
oocytes that reached MII (70.27% and 58.46% for class A and B oocytes, respectively).
Furthermore, the presence of hormonal additives and 10% EES in TCM-199 that
contain 40 ng/ml EGF during IVM, had the highest percentage of sheep oocytes maturation. It
could be deduced that EES alone or with hormonal additives in TCM-199 increased the
percentage of oocytes with complete cumulus cells expansion. Similar results achieved by using
EGF in in vitro maturation medium only for class A oocytes.