Reproduction Abstracts

The evolutionarily conserved Wnt/β-catenin signal transduction pathway controls many biological processes. The objective of this study was to determine the role of this signaling pathway in follicular development and luteal function. To this purpose PMSG–eCG gonadotropin-prepubertal treated female rats were injected with a Wnt inhibitor (XAV939, 5 μg/ovary, Wnt-I group) or vehicle (DMSO, control group) into the bursa of both ovaries the day of hCG administration. Two days after hCG and Wnt-I or vehicle injection, blood samples and ovaries were collected. Ovarian function was evaluated by measuring serum progesterone (P₄) (RIA), steroidogenic-regulators protein levels by western blot, apoptotic parameters and ovarian structures at different stages of development. The levels of P₄ significantly decreased after Wnt inhibitor administration. Corpora lutea (CL) were isolated by microdissection and steroidogenic protein regulators were measured. StAR levels significantly decreased in the Wnt-I group in comparison with the control group, whereas the levels of P450scc or 3β-HSD enzymes did not change. IHC studies showed that luteal cells exhibited high staining for active Caspase 3 in the Wnt-I group in comparison with the control. Histological studies showed a tendency to a decrease in the percentage of CL and an increase in antral follicles in the Wnt-I group. In conclusion, the inhibition of Wnt pathway appears to produce a decrease in P₄ serum levels associated to a decrease in StAR levels in CL, an increase in active Caspase 3 expression and a tendency to inhibit luteinization.