Effect of endogenous melatonin and its receptor in mice oocyte maturation

• Grant number: 14/00523-6
• Support Opportunities: Scholarships abroad - Research Internship - Master's degree
• Start date: May 01, 2014
• End date: October 31, 2014
• Field of knowledge: Agronomical Sciences - Veterinary Medicine - Animal Reproduction
• Principal Investigator: Cláudia Lima Verde Leal
• Grantee: Hugo Fernandes
• Supervisor: Margarita L. Dubocovich
• Host Institution: Faculdade de Zootecnia e Engenharia de Alimentos (FZEA). Universidade de São Paulo (USP). Pirassununga , SP, Brazil
• Institution abroad: University at Buffalo (UB), United States
• Associated to the scholarship: 12/13675-3 - Melatonin and its cytoprotector effect on oocyte maturation in mice, BP.MS

Abstract

Advances in the in vitro production (IVP) of embryos in several species, is still below desired levels, especially compared to embryos produced in vivo. Evidence suggest that the developmental rate of IVP of embryos is related to the intrinsic quality of the oocyte and the in vitro maturation (IVM) step appears to play an important role among the various factors that affect these results. Melatonin is a hormone synthesized in the pineal gland and its functions have been shown to be more diverse, including antioxidant and antiapoptotic activity, besides influencing different signaling pathways. Melatonin was found in ovarian follicular fluid and their receptors have been localized in the granulosa cells and oocytes. In vitro studies have shown positive effects of its use for oocyte maturation and embryo development. There are few studies on the effects of melatonin on oocyte maturation in the mouse, due to its relative short reproductive cycle and lower cost for maintenance, is an interesting model, widely used for in vitro studies, but also in vivo, which are much slower and expensive in domestic animals. So, the use of a mouse model is also interesting for providing more physiological results. In mammals, the activation of melatonin receptors MT1 and MT2 is responsible for the modulation of various physiological functions. With the potential of melatonin in promoting better outcomes for IVP of embryos, it is important to further investigate the functional implications of this hormone on oocyte competence. Thus, the availability of mouse strains with identical genetic background which are "melatonin deficient" and "melatonin proficient" provide for the first times models where to test the hypothesis that endogenous melatonin plays a role in oocyte maturation and on the expression of genes related to antioxidant cell protection and apoptosis. Therefore, to better understand the role of melatonin, we propose to study the participation of endogenous melatonin and its receptors on the in vivo maturation of oocytes and on the expression of antioxidant and apoptosis-related genes in murine cumulus-oocyte-complexes (COCs). The effect of endogenous melatonin on in vivo maturation will be studied. Mouse females from C57 strains (melatonin deficient and melatonin proficient) will be superovulated and after 14-16 h of in vivo maturation, the COCs will be collected, and oocytes and cumulus cells will be separated. Oocytes will be first assessed for maturation rate (extrusion of the 1st PB) and then both oocytes and cumulus cells will be separately processed for PCR analyses (Bax, Bcl-2, GPx and SODs). On the second experiment, effect of knockout of melatonin receptors on in vivo maturation will be evaluated. Mouse females from C3H strain knockout for MT1, MT2 or MT1/MT2 and wild-type, will be superovulated and after 14-16 h of in vivo maturation, the COCs will be collected and processed for same evaluations described for the previous experiments. (AU)