Role Of Autophagy In Modulating Post-ovulatory Aging Of Mouse Oocytes

Mammalian oocytes are arrested at the meiotic metaphase Ⅱ(M Ⅱ)stage following ovulation,if not promptly completing the fertilization process,the oocyte will undergo time-dependent aging process.The aging of oocytes can not only cause abnormal fertilization,abnormal cleavage,aneuploidy rate of embryos after fertilization,but also can lead to decreased pregnancy rate,abortion rate and birth defects.Meanwhile,the progeny of aged oocytes exhibit mental abnormality,increased hyperactivity,lower fecundity and shortened life span.Thus,alleviating or preventing oocyte aging has become an urgent problem to be solved in the research and application of mammalian reproduction and embryo engineering.Autophagy has become one of the hotspots of current research in the study of alleviating or preventing cell aging.Autophagy is that autophagosomes are formed by encapsulation of cells to be degraded with single or double layer membranes,which are then transported to lysosomes to form autophagolysosomes and undergo digestion and degradation of multiple enzymes to achieve the needs of cellular metabolic and renewal of some organelles.Autophagy can eliminate,degrade,and digest damaged,denatured,senescent and dysfunctional cells,organelles and denatured proteins as well as nucleic acids and other biological macromolecules.The autophagy pathway is considered as a protective pathway.Therefore,our experiment is to explore whether autophagy can alleviate or prevent oocyte aging.To explore the causal relationship between autophagy and oocyte aging,oocyte activation rate,oocyte Caspase-3 expression,oocyte developmental competence,oocyte cytoplasmic calcium level and oocyte oxidative stress level,oocyte mitochondrial membrane potential,oocyte spindle morphology are used to be the indicator of observing the effect of autophagy on oocyte aging when activator RAPA and inhibitor 3-MA of autophagy are added to the medium.Experimental results manifest:(1)Autophagy and mouse oocyte aging are closely related.(2)RAPA significantly increased the number of autophagosomes in oocyte,3-MA significantly reduced the number of autophagosomes in oocyte.(3)RAPA could significantly decrease the activation rate of oocytes in mouse,and 3-MA could significantly increase the activation rate of aged oocytes.(4)RAPA could significantly decrease the expression of Caspase-3 in mouse aged oocytes,3-MA could significantly increase the expression of Caspase-3 in mouse aged oocytes.(5)RAPA could significantly improve the development of aged oocytes in mouse,and3-MA could significantly reduce the development of aged oocytes in mouse.(6)RAPA could significantly decrease the cytosolic calcium concentration in aged oocytes of mouse,and 3-MA could significantly increase the cytosolic calcium concentration in aged oocytes of mouse.(7)RAPA could significantly decrease the oxidative stress of aged oocytes in mouse,and3-MA could significantly increase the oxidative stress of aged oocytes in mouse.(8)RAPA could significantly increase the mitochondrial membrane potential of mouse aged oocytes,and 3-MA could significantly decrease the mitochondrial membrane potential of mouse aged oocytes.(9)RAPA could significantly increase the proportion of oocytes with normal morphology of the spindle,and 3-MA could significantly reduce the proportion of oocytes with normal morphology of the spindle.Conclusion: Autophagy can inhibit mouse oocyte aging.