Roles Of α-lipoic Acid During Postovulatory Aging Of Mouse Oocyte

Mammalian reproductive capacity is disturbed by many factors. Individual aging and germ cell aging seriously affect the efficiency of animal reproduction. While the most important factor is the oocyte aging which seriously reduces the female’s reproductive capacity. Oocytes will suffer aging with different degree resulting from a variety of ressons. This will result in the decreased fertility rate in vivo and in vitro, low quality of embryo, the rising abortion in early pregnancy, abnormal development of offspring. And this will also limit the development and application of the in vitro fertilization (IVF). somatic cell nuclear transfer (SCNT) and intracytoplasmic sperm injection technology(ICSI). It is necessary and important to discover the mechanism of oocyte aging and its’regulation mechanism. Alpha lipoic acid (LA) which distributes in the mitochondria is a kind of biological antioxidants and can clear almost all free radicals. In this study, the mouse model of oocyte in vitro aging was used to investigate role of LA in the process of aging through IVF, parthenogenetic activation and immunofluorescence technique. Meanwhile the relationship between LA and autophagy in the oocyte aging will be discussed.1. LA delays the aging process of oocyte in vitroThe results showed that during the in vitro aging of oocyte, fertilization rate significantly was decreased (from 87.71% ± 6.35% to 67.55% ± 6.44%), the rate of morphologic abnormity after IVF was increased (from 2.05% ± 2.12% to 12.85% ± 4.20%), cell polarity was lost (actin cap lost), spindle shape was unconventional changed and histone H4K8 and H4K12 acetylation levels were increased. When LA was added into the culture media with 10 μM concentration, fertilization rate was increased to 83.19% ± 8.00%, the rate of morphologic abnormity after IVF was decreased to 4.46% ± 2.07%, spindle shape resumed, cell polarity remained, the level of histone H4K8 and H4K12 acetylation were low, comparing with the control group (normal aging). These results indicated that LA can delay the aging process of oocyte in vitro.2. LA prevent the increase of autophagy in the oocyte aging in vitroFirst of all, the level of autophagy in the oocyte aging in vitro was determined. Results showed that autophagy was increased during the oocyte aging. Next, rapamycin (autophagy enhancer) or 3-MA (autophagy inhibitor) were used to interfere the autophagy level and the process of oocyte aging were investigated.Results showed that Rapamycin significantly decreased fertilization rate (p<0.01) and significantly increased the rate of morphologic abnormity after IVF. However the 3-MA exhibited the contrary results. Finally, LA was added into the culture media and the autophagy level was determined. Results showed that LA decreased autophagy level. This suggested that autophagy level was increased in the process of in vitro aging and LA prevented the increase of autophagy. It may be through inhibiting the autophagy that LA delayed the aging of oocytes.Based on all the results, LA can delay the process of oocytes aging in vitro through increasing the vitro fertilization rate, preventing cell polarity loss, decreasing histone acetylation and autophagy.