Characterization of EGF and IGF-1 system in the ovary and its role in in vitro maturation of guinea pig oocytes

Resumo

Among non-primate species, guinea pig (Cavia porcellus) is used as a laboratory animal since the late 18th century and remains an essential species in many areas of research. It is an excellent animal model for the study of reproduction in humans and domestic animals because of spontaneous ovulation and active corpora lutea, long gestation period and type of placenta. As in woman, guinea pigs have small to medium-sized litters, low ovulation rate and only few preimplantation embryos can be obtained from one female. Similarly, the immature resting oocytes in the guinea pig ovary are on the true diplotene stage as in women and they are more sensitive to ionic radiation than mice oocytes. Therefore, some studies have suggested that guinea pig may represent an alternative animal model than mice for investigations on ovarian infertility in women that show premature ovarian failure as a consequence of radiotherapy. In this sense, it is widely known that the insulin like growth factor (IGF-1) and epidermal growth factor (EGF) are implied in the regulation of many ovarian processes throgouth their receptors. EGF and its receptor (EGF-R) are involved in the ovulation process, oocyte maturation, steroidogenesis of follicle and luteinization of corpus luteum in humans and animal species. In addition, Insulin-like growth factor-1 (IGF-1) system plays an important role in the regulation of ovarian folliculogenesis, steroidogenesis and apoptosis prevention and is luteotropic in corpus luteum and promotes early embryo development. Firthermore, the gene expression of IGFs and their binding proteins (IGFBPs) differ from women with normal ovaries and those with polycystic ovary syndrome (PCOS)...