EFFECT OF IGF-I ON PIG OOCYTE MATURATION, FERTILIZATION, AND EARLY EMBRYONIC-DEVELOPMENT IN-VITRO, AND ON GRANULOSA AND CUMULUS CELL BIOSYNTHETIC ACTIVITY
P. Xia et al., EFFECT OF IGF-I ON PIG OOCYTE MATURATION, FERTILIZATION, AND EARLY EMBRYONIC-DEVELOPMENT IN-VITRO, AND ON GRANULOSA AND CUMULUS CELL BIOSYNTHETIC ACTIVITY, Molecular reproduction and development, 38(4), 1994, pp. 373-379
Porcine granulosa cells have been shown previously to both secrete and
respond to insulin-like growth factor-I (IGF-I), suggesting an autocr
ine function of this peptide in the follicle. The present work was und
ertaken to determine possible effects of IGF-I on in vitro maturation,
in vitro fertilization, and early embryonic development in culture. G
ranulosa and cumulus cell proliferation and differentiation based on H
-3-thymidine uptake and progesterone production, respectively, were al
so assessed. The results showed that the cleavage rate of oocytes was
markedly stimulated in a dose-dependent manner by the addition of IGF-
I to the oocyte maturation medium (P < 0.05). Embryo development beyon
d the 8-cell stage was improved by IGF-I, reaching a maximum of 22% at
200 ng/ml IGF-I. Treatment with IGF-I after fertilization increased t
he percentage of total oocyte cleavage (P < 0.05) to approximately 52%
, 43%, and 57% at, respectively, 25, 50, and 100 ng/ml IGF-I. H-3-thym
idine incorporation by granulosa cells was significantly increased in
cultures treated with FSH (3-fold) or IGF-I (6-fold) compared to the c
ontrol. For the cumulus cells, FSH caused a similar increase (3-fold)
in H-3-thymidine incorporation while IGF-I stimulated a 15-fold increa
se. Progesterone production by the granulosa cells was increased to th
e same extent by treatment with FSH or IGF-I (4.7 and 5.1-fold, respec
tively). However, for the cumulus cells, while FSH caused a marked 16-
fold increase in progesterone production, IGF-I caused only a marginal
increase of 2.5-fold. These results indicate a beneficial effect of I
GF-I on in vitro porcine oocyte maturation and pre-implantation embryo
development, suggesting a physiological role for IGF-I in vivo. The i
n vivo effect of IGF-I may be indirect via autocrine stimulation of cu
mulus and/or granulosa cells resulting in enhanced oocyte maturation a
nd fertilization. (C) 1994 Wiley-Liss, Inc.