Submitted June 25, 2007
Returned for revision July 25, 2007
Accepted October 31, 2007
Ovary
Intrabursal Administration of the Antiangiopoietin 1 Antibody Produces a Delay in Rat Follicular Development Associated with an Increase in Ovarian Apoptosis Mediated by Changes in the Expression of BCL2 Related Genes
Fernanda Parborell ,
Dalhia Abramovich ,
and
Marta Tesone *
* To whom correspondence should be addressed. E-mail: mtesone{at}dna.uba.ar.
Abstract
The angiopoietin (ANGPT)-receptor (TEK) system plays a crucial role in blood vessel development and regression. To date, no reports have addressed the actions of the anti-ANGPT1 antibody on gonadotropin-stimulated follicular development and atresia in the ovary. Therefore, in this study, we specifically investigated whether ANGPT1 plays a critical intraovarian survival role for gonadotropin-dependent folliculogenesis. In particular, we examined the effect of local administration of anti-ANGPT1 antibody on follicular development, apoptosis and expression of BCL2 protein family members (BAX, BCL2 and BCL2L1), TNFRSF6 and FASLG in ovarian follicles from prepubertal eCG-treated rats. The inhibition of ANGPT1 caused an increase in the number of atretic follicles and a decrease in the number of both antral follicles (AF) and preovulatory follicles (POF) in gonadotropin-treated rat ovaries. Taking into account that follicular atresia is mediated by apoptosis, we analyzed the effect of the antibody against ANGPT1 on programmed cell death. The inhibition of the action of ANGPT1 caused an increase both in the number of apoptotic granulosa cells in AF and in the spontaneous DNA fragmentation of AF cultured in serum-free medium. Besides, AF obtained from rats treated with intraovarian antibodies against ANGPT1 showed both a decrease in BCL2 and an increase in BAX protein levels. Moreover, a reduction in the BCL2L1L:BCL2L1S ratio was observed in this group, with a reduction of BCL2L1L greater than that of BCL2L1S, thus showing that the expression of these antiapoptotic proteins is lower in follicles from treated rats than in those from untreated ones. Our findings suggest that the inhibition of ANGPT1 activity causes an increase in the number of atretic follicles mediated by ovarian apoptosis through an imbalance in the ratio of antiapoptotic:proapoptotic proteins. This could take place through a paracrine effect on granulosa cells mediated by the TEK receptor in theca cells. Therefore, these data clearly indicate that ANGPT1 is necessary for follicular development induced by gonadotropins.
Key words:
Ovary •
Apoptosis •
Follicle •
angiogenesis •
angiopoietin 1
