330 ROLE OF STAT3 PATHWAY IN THE LEPTIN-INDUCED SIGNALING DURING OOCYTE IN VITRO MATURATION AND STEROIDOGENIC RESPONSE IN RABBIT MODELM. Arias-Alvarez A , R. M. Garcia-Garcia A , L. Torres-Rovira B , A. Gonzalez-Bulnes B , P. G. Rebollar C and P. L. Lorenzo A
A Universidad Complutense de Madrid, Madrid, Spain;
B INIA, Madrid, Spain;
C Universidad Politecnica de Madrid, Madrid, Spain
Reproduction, Fertility and Development 22(1) 321-321 http://dx.doi.org/10.1071/RDv22n1Ab330
Published: 8 December 2009
The effect of leptin on oocyte maturation and steroidogenic response could be mediated by activation of specific transcription factors. The aim of this work was to establish if the Signal Transducer and Activator of Transcription 3 (STAT3) pathway mediates leptin’s influence on oocyte maturation and steroid secretion of COC by using a rabbit oocyte model. A total of 522 COC from follicles >1 mm were IVM for 16 h (38°C, 5% CO2) in TCM-199 serum free medium plus: 0 or 10 ng mL-1 leptin. Each group was further treated with 10 and 100 μM of specific inhibitor for STAT3 pathway (AG490, Sigma, St. Louis, MO, USA). COC were treated progressively with hyaluronidase (2 mM), 0.5% pronase, 4% paraformaldehyde, 0.02% Triton X-100, and 7.5% BSA after IVM. Oocytes examined under a confocal laser-scanning microscope were previously incubated with 100 mg mL-1 fluorescein isothiocyanate of Lens culinaris (FITC-LCA) and then with 10 mg mL-1 propidium iodide, for cortical granule (CG) and nuclear staining, respectively. Spent maturation media were analyzed for oestradiol and progesterone secretion using Enzimoinmunoassay. Statistical analysis was performed by Chi-square and ANOVA tests. COC supplemented with 10 ng mL-1 leptin had significantly higher metaphase IIrate than those IVM without leptin (P < 0.05); but it did not enhance the percentage of oocytes with peripheral migration of CG (Table 1). Leptin-stimulated nuclear oocyte maturation was significantly impaired when the STAT3-inhibitor was added to the media (P < 0.005). CG migration index was not modified when inhibitors were included in IVM media compared to control groups. Estradiol and progesterone secretion by COC were similar in all groups tested; these concentrations were not affected when STAT3-pathway inhibitor was added. The results confirmed that 10 ng mL-1 leptin enhances meiotic oocyte maturation but not CG migration, through the STAT3 pathway. In the present rabbit model, this effect is not mediated by an increase of steroid secretion by COC.
We acknowledge CM, FSE, and MICINN for funding.