Efeito do FSH, Ativina-A e GDF-9 sobre o desenvolvimento in vitro de folículos pré-antrais caprinos

Abstract

The aim of this study was to investigate the levels of messenger RNA (mRNA) for activin-A on goat preantral and antral follicles and the effects of follicle stimulating hormone (FSH), activin-A and growth and differentiation factor - 9 (GDF-9) on growth and mRNA expression for activin-A, GDF-9, bone morphogenetic protein (BMP) -2, -4, -6, -7, -15 and FSH receptor (FSH-R) in goat preantral follicles cultured in vitro. Initially, primordial, primary and secondary follicles, as well as cumulus-oocyte complexes (COCs) and mural granulosa/theca cells of small and large antral follicles were isolated mechanically from goat ovaries and the expression of mRNA for activin-A was evaluated by real-time PCR. For in vitro studies, goat secondary follicles were isolated and cultured for 6 days in the presence of FSH alone (50 ng/mL) or in combination with activin-A (100 ng/mL) or GDF-9 (200 ng/mL). Alone or in combination with FSH, the influence of activin-A on expression of activin-A and FSH-R, and the effect of GDF-9 on the levels of mRNA for GDF-9, FSH-R and BMP -2, -4, -6, -7 and -15 in secondary follicles after 6 days of culture were tested. For this, after extraction of total RNA and cDNA synthesis, the levels of mRNA for activin-A, GDF-9, FSH-R and BMP -2, -4, -6, -7 and -15 were quantified by real time PCR. The results showed that secondary follicles had lower levels of mRNA for activin-A, than compared to primary follicles (p<0.05). There was no difference in levels of mRNA for activin-A between primordial and primary or secondary (p>0.05). Allied to this, there was no difference between COCs of small and large antral follicles (p>0.05). Moreover, granulosa and theca cells of large antral follicles showed higher levels of mRNA for activin-A than in small antral follicles (p<0.05). When comparing mRNA expression for activin-A between COCs from small and large antral follicles and their granulosa and theca cells, no difference in expression levels was observed (p>0.05). After in vitro culture of secondary follicles, the presence of FSH either alone or associated with activin-A or GDF-9 increased survival, follicular growth and antrum formation (p<0.05). The FSH increased mRNA for activin-A, while the follicles cultured with activin-A showed increased levels of mRNA for FSH-R (p<0.05). In addition, GDF-9 decreased mRNA expression for BMP -2 and -15 (p<0.05), but had no effect on expression of BMP -4, -6, and -7 (p>0.05). In conclusion, during the transition from primary to secondary follicles there is a reduction of mRNA for activin-A, whereas there is an increased expression of this factor during the growth of antral follicles. FSH, activin-A and GDF-9 stimulate growth of goat secondary follicles after 6-day culture. After follicle culture FSH controls the expression of activin-A, and the expression of FSH-R is regulated by activin-A. Furthermore, GDF-9 reduces the mRNA expression for BMP-2 and -15