Regulation of folliculogenesis and apoptosis by intrabursa injection of angiopoietin-1 (ANPT-1) Ab to gonadotropin- treated prepuberal rats

TESONE MARTA; ABRAMOVICH DALHIA; RODRIGUEZ CELIN ALEJANDRA; PARBORELL FERNANDA

Texas, USA.

Congreso; Society for Studies of Reproduction; 2007

Angiogenesis is a process of vascular growth that is mainly limited to the reproductive system in healthy adult mammals. While VEGF is the main initiator of angiogenesis, the formation and differentiation of a structurally and functionally mature vascular network requires the coordinated action of various factors, including ANPT-1 and ANPT-2, which act via the tyrosine kinase receptor, Tie-2. The objective of this study was to determine the role of ANPT-1 on the folliculogenesis and ovarian apoptosis. Female immature rats superovulated with eCG were injected with an ANPT-1 Ab (1-10 ng/ovary) under the bursa of one ovary and the contralateral with con IgG (C). The ovaries were removed at different times for histological studies. Follicle growth was determined 12, 24 and 48 hours after surgery. The number of atretic follicles/ovary significantly increased after 48 h of ANPT-1 Ab (10 ng) treatment (C: 24.5±2.4; ANPT-1 Ab : 40.7±4.8 %,  p<0.05) whereas the number of antral follicles/ovary significantly decreased (C: 62.4±2.4; ANPT-1 Ab : 46.0±4.7 %, p <0.05). Immunohistochemical studies show the expression of ANPT-1 and Tie-2 in theca cell layers of the different growth follicular stages. No staining was present in granulosa cells. ANPT-1 Ab treatment significantly increased the number of apoptotic cells in antral follicles detected by TUNEL 48 h after surgery (C: 2.3±0.3; ANPT-1 Ab: 6.1±0.8 apoptotic cells/field, p<0.05). Antral follicles were dissected under a stereoscopic microscope and used for Western blots. ANPT-1 Ab injection reduced the ratio Bcl-xL/Bcl-xS and Bcl-2/Bax whereas the levels of Fas and Fas-L proteins did not change. In conclusion, intraovarian neutralizing antibody against ANPT-1 appears to induce an increase in ovarian apoptosis through an imbalance in the ratio of antiapoptotic:proapoptotic proteins, leading a larger number of follicles to atresia. ANPT-1 could act on follicular growth by an angiogenesis increase or through a direct effect mediated by an ovarian ANPT-1 receptor in theca cells. Supported by: UBA (EX237), CONICET (PIP 5471), ANPCYT (PICT 5-26047) and Roemmers Foundation.