Tannin (TA) improves porcine oocyte cytoplasmic maturation and subsequent embryonic development after in vitro fertilization (IVF). However, the mechanism through which TA blocks polyspermy after IVF remains unclear. Hence, the biological function of organelles (cortical granule [CG], Golgi apparatus, endoplasmic reticulum [ER], and mitochondria) and the incidence of polyspermic penetration were examined. We found no significant difference in oocyte nuclear maturation among the 1 µg/mL, 10 µg/mL TA, and control groups. Moreover, 100 μg/mL TA significantly reduced 1st polar body formation rate compared to the other groups. Additionally, 1 and 10 μg/mL TA significantly increased the protein levels of GDF9, BMP15, and CDK1 compared to the control and 100 μg/mL TA groups. Interestingly, 1 and 10 μg/mL TA improved the normal distribution of CGs, Golgi, ER, and mitochondria by upregulating organelle-related gene expression and downregulating ER stress (CHOP) gene expression. Simultaneously, 1 and 10 μg/mL TA significantly increased the proportion of normal fertilized oocytes (2 pronuclei; 2 PN) and blastocyst formation rate compared to the control, as well as that of 100 μg/mL TA after IVF by upregulating polyspermy-related genes. In conclusion, TA during IVM enhances 2PN and blastocyst formation rates by regulating organelles’ functions and activities.

This study aimed to determine the underlying mechanism of ramelteon on the competence of oocyte and subsequent embryo development in pigs during in vitro maturation (IVM). Our results showed that the cumulus expansion index was significantly lower in the control group compared to the ramelteon groups (p < 0.05). Moreover, supplementation of 10−11 and 10−9 M ramelteon significantly increased the cumulus expansion and development-related genes expression, and reduced apoptosis in cumulus cells (p < 0.05). In oocytes, the nuclear maturation rate was significantly improved in 10−11, 10−9, and 10−7 M ramelteon groups compared to the control (p < 0.05). Additionally, the level of intracellular GSH was significantly increased and ROS was significantly decreased in ramelteon-supplemented groups, and the gene expression of oocyte development and apoptosis were significantly up- and down-regulated by 10−11 and 10−9 M ramelteon (p < 0.05), respectively. The immunofluorescence results showed that the protein levels of GDF9, BMP15, SOD1, CDK1, and PGC1α were significantly increased by 10−11 M ramelteon compared to the control (p < 0.05). Although there was no significant difference in cleavage rate, the blastocyst formation rate, total cell numbers, and hatching/-ed rate were significantly improved in 10−11 M ramelteon group compared to the control (p < 0.05). Furthermore, embryo development, hatching, and mitochondrial biogenesis-related genes were dramatically up-regulated by 10−11 M ramelteon (p < 0.05). In addition, the activities of lipogenesis and lipolysis in oocytes were dramatically increased by 10−11 M ramelteon compared to the control (p < 0.05). In conclusion, supplementation of 10−11 M ramelteon during IVM improved the oocyte maturation and subsequent embryo development by reducing oxidative stress and maintenance of lipid homeostasis.

Background: The importance of the processes of lipogenesis and lipolysis in providing an essential energy source during oocyte maturation is increasingly being recognized. Recent our studies have demonstrated that melatonin up-regulated lipid metabolism during oocyte maturation. Nevertheless, there is still limited information regarding the underlying molecular mechanisms of action of melatonin on lipid metabolism in porcine cumulus-oocyte complexes (COCs). Here, our aim was to investigate the effect of melatonin on COCs, and the melatonin receptor-mediated lipid metabolism signaling pathway.Materials/methods: To determine the melatonin-mediated lipolysis pathway in cumulus cells, COCs were treated with melatonin and the correlated metabolic responses were assessed using melatonin receptor-mediated signaling.Results: The results showed that exposure of COCs to melatonin during in vitro maturation significantly increased cumulus expansion index, blastocyst formation rate and total cell numbers/blastocyst, although nuclear maturation was no significant difference. The levels of proteins MT1, MT2, Gsα, PKA, and lipolysis-related factors (AGTL, HSL, PLIN A+B) were significantly increased by melatonin supplementation, and this effect was inhibited by simultaneous treatment with melatonin antagonists (luzindole or 4P-PDOT), although 4P-PDOT treatment did not completely block the effect of melatonin on MT1. Further, the gene expression patterns reflected their relevant protein levels in cumulus cells. Melatonin-mediated lipolysis could significantly reduce lipid droplets (LDs) numbers and increase fatty acid (FA) production and ATP levels by increasing the β-oxidation-related gene expression in cumulus cells. Simultaneously, melatonin significantly increased the amount of LDs, FAs, ATP, and enhanced the lipid metabolism-related gene expression in oocytes. Finally, the oocyte quality was improved by increasing GDF9, BMP15 and GSH and decreasing ROS levels.Conclusion: These findings revealed that the MT2-mediated cAMP/PKA signaling pathway promotes intracellular lipolysis and FA production in cumulus cells, which provided an essential energy source for COCs development.