Oxidative stress is known as a major contributing factor involved in oocyte aging, which negatively affects oocyte quality and development after fertilization. Melatonin is an effective free radical scavenger and its metabolites AFMK and AMK are powerful detoxifiers that eliminate free radicals. In this study, we used porcine oocytes to test the hypothesis that melatonin could scavenge free radicals produced during oocyte aging, thereby maintaining oocyte quality. We compared reactive oxygen species levels, apoptosis levels, mitochondrial membrane potential ratios, total glutathione contents and expression levels in fresh, aged and melatonin-treated aged porcine oocytes and observed the percentage of blastocyst formation following parthenogenetic activation. We found that melatonin could effectively maintain the morphology of oocytes observed in control oocytes, alleviate oxidative stress, markedly decrease early apoptosis levels, retard the decline of mitochondrial membrane potential and significantly promote subsequent embryonic development in oocytes aged for 24 hr in vitro. These results strongly suggest that melatonin can prevent postovulatory oocyte aging and promote subsequent embryonic development in the pig, which might find practical applications to control oocyte aging in other mammalian species including humans to maintain the quality of human oocytes when performing clinical assisted reproductive technology.

Melatonin, a major hormone of the pineal gland, exerts many beneficial effects on mitochondria. Several studies have shown that melatonin can protect against toxin‐induced oocyte quality impairment during maturation. However, there is little information regarding the beneficial effects of melatonin on toxin‐exposed early embryos, and the mechanisms underlying such effects have not been determined. Rotenone, a chemical widely used in agriculture, induces mitochondrial toxicity, therefore, damaging the reproductive system, impairing oocyte maturation, ovulation, and fertilization. We investigated whether melatonin attenuated rotenone exposure‐induced impairment of embryo development by its mitochondrial protection effect. Activated oocytes were randomly assigned to four groups: the control, melatonin treatment, rotenone‐exposed, and “rotenone + melatonin” groups. Treatment with melatonin abrogated rotenone‐induced impairment of embryo development, mitochondrial dysfunction, and ATP deficiency, and significantly decreased oxidative stress and apoptosis. Melatonin also increased SIRT1 and PGC‐1α expression, which promoted mitochondrial biogenesis. SIRT1 knockdown or pharmacological inhibition abolished melatonin's ability to revert rotenone‐induced impairment. Thus, melatonin rescued rotenone‐induced impairment of embryo development by reducing ROS production and promoting mitochondrial biogenesis. This study shows that melatonin rescues toxin‐induced impairment of early porcine embryo development by promoting mitochondrial biogenesis.

Ubiquinol-10, the reduced form of coenzyme Q10, protects mammalian cells from oxidative damage and enhances mitochondrial activity. However, the protective effect of ubiquinol-10 on mammalian oocytes is not well understood. In this study, we investigated the effect of ubiquinol-10 on porcine oocytes during postovulatory aging. Metaphase II oocytes were selected as fresh oocytes and further cultured for 48 h with different concentrations of ubiquinol-10 (0-400 μM) in vitro as a postovulatory aging model. After choosing the optimal concentration of ubiquinol-10 (100 μM) that maintained oocyte morphology and developmental competence during the progression of aging, the oocytes were randomly divided into five groups: fresh, control-24 h, ubiquinol-24 h, control-48 h, and ubiquinol-48 h. The results revealed that ubiquinol-10 significantly prevented aging-induced oxidative stress, GSH reduction, cytoskeleton impairment, apoptosis, and autophagy. Mitochondrial biogenesis (SIRT1 and PGC-1α) and mitophagy (PINK1 and PARKIN)-related proteins were decreased during aging. Addition of ubiquinol-10 prevented the aging-induced reduction of these proteins. Consequently, although mitochondrial content was decreased, the number of active mitochondria and ATP level were significantly increased upon treatment with ubiquinol-10. Thus, ubiquinol-10 has beneficial effects on porcine postovulatory aging oocytes owing to its antioxidant properties and ability to promote mitochondrial renewal.

Phosphatase and tensin homolog–induced kinase 1 (PINK1) on the outer membranes of impaired mitochondria promotes mitophagy and regulates mitochondrial morphology. Mammalian oocytes and early embryos are mitochondria rich, but mitochondrial dynamics during preimplantation embryo development is not well‐studied. To investigate whether PINK1 is required for mitochondrial dynamics in porcine preimplantation embryos, gene knockdown and inhibitors were used, and mitochondrial dynamics were observed by transmission electron microscopy. PINK1 knockdown significantly impaired blastocyst formation and quality, induced mitochondrial elongation and swelling, and reduced mitochondrial DNA copy number. PINK1 knockdown–induced mitochondrial elongation caused mitochondrial dysfunction, oxidative stress, and ATP deficiency, significantly increasing autophagy and apoptosis. Profission dynamin‐related protein 1 overexpression prevented PINK1 knockdown–induced impairment of embryo development, mitochondrial elongation, and dysfunction. Thus, PINK1 promotes mitochondrial fission in porcine preimplantation embryos.—Niu, Y.‐J., Nie, Z.‐W., Shin, K.‐T., Zhou, W., Cui, X.‐S. PINK1 regulates mitochondrial morphology via promoting mitochondrial fission in porcine preimplantation embryos. FASEB J. 33, 7882–7895 (2019). http://www.fasebj.org

Excessive long-term fluoride intake is associated with several health problems, including infertility. However, limited information is available on the toxic effects of fluoride exposure on the female reproductive system, especially oocyte maturation. In this study, we investigated the toxic effect of sodium fluoride (NaF) exposure on porcine oocyte maturation and its possible underlying mechanisms. Our results showed that NaF exposure during porcine oocyte maturation inhibited cumulus cell expansion and impaired polar body extrusion. Cell cycle analysis showed that NaF exposure blocked meiotic resumption, disturbed spindle dynamics, disrupted chromosome separation, and increased aneuploidy in porcine oocytes. Moreover, NaF exposure disturbed mitochondrial function, triggered DNA damage response, and induced early apoptosis in porcine oocytes. NaF exposure also induced oxidative stress, decreased GSH level, and increased cathepsin B activity in and impaired the further development potential of porcine oocytes, as indicated by a decrease in blastocyst formation rate, increase in apoptosis, and inhibition of cell proliferation. Together, these results indicate that NaF exposure impairs the maturation capacity of porcine oocytes by inhibiting cumulus cell expansion, disturbing cytoskeletal dynamics, and blocking nuclear and cytoplasmic maturation, thus decreasing the quality and affecting the subsequent embryonic development potential of porcine oocytes.