The effect of poly(ADP-ribosyl)ation inhibition on the porcine cumulus-oocyte complex during in vitro maturation.

Poly(ADP-ribosyl)ation (PARylation) plays important roles in DNA repair, apoptosis, transcriptional regulation, and cell death, and occurs via the activity of poly(ADP-ribose) polymerases (PARPs). Previous studies have shown that PARylation affects mouse and porcine pre-implantation development and participates in mechanisms of autophagy. However, there have not yet been reported the role of PARylation during in vitro maturation (IVM) of porcine oocytes. Thus, we investigated the effect of PARylation inhibition on this process; cumulus-oocyte complexes (COCs) were cultured with 3-aminobenzamide (3-ABA, PARP inhibitor) during porcine IVM. Full cumulus expansion was significantly reduced (10.34 ± 1.23 [3-ABA] vs. 48.17 ± 2.03% [control]), but nuclear maturation rates were not changed in the 3-ABA treatment group. Especially, we observed that cumulus cells were little expanded after 22 h in 3-ABA treated COCs. The mRNA expression levels of oocyte maturation- and cumulus expansion-related genes were evaluated at 22 and 44 h. GDF9, BMP15, COX-2, and PTX3 expression were upregulated at 44 h, whereas the levels of HAS2 and TNFAIP6 were downregulated in the 3-ABA treated group. Furthermore, 3-ABA treatment significantly decreased the developmental rate (28.24 ± 1.06 vs. 40.24 ± 3.03%) and total cell number (41.12 ± 2.10 vs. 50.38 ± 2.27), but increased the total apoptotic index (6.44 ± 0.81 vs. 3.08 ± 0.51) in parthenogenetically activated embryos. In conclusion, these results showed that PARylation regulates cumulus expansion through the regulation of gene expression and affects developmental competence and quality in parthenogenetic embryos.

Sirtuin inhibition leads to autophagy and apoptosis in porcine preimplantation blastocysts.

Sirtuins are nicotinamide adenine dinucleotide dependent class III histone deacetylase proteins that play a crucial role in several cellular processes, including DNA repair, apoptosis, and lifespan. Previous studies have shown that sirtuin inhibition leads to embryonic developmental arrest and oxidative stress in porcine and murine. However, sirtuin-mediated mechanisms have not been examined in porcine preimplantation blastocysts. We therefore investigated the relationship between sirtuins and autophagy. Embryos were cultured with 100 µM sirtinol (SIRT1/2 inhibitor) in NCSU-23 media after in vitro fertilization. Treatment with sirtinol significantly reduced the rates of morula (21.34 ± 1.84 vs. 11.89 ± 2.01), blastocyst development (17.18 ± 1.81 vs. 9.00 ± 2.02), and total cell number (50.80 ± 1.47 vs. 37.71 ± 1.79), compared to controls, with an associating decrease the levels of Sirt2 transcript. Sirtinol treatment induced autophagy through an increase in LC3 transcript and LC3 protein. BECLIN1 and ATG5 expression showed a slight increase in treated group. Finally, treatment with sirtinol dramatically increased TUNEL indices (6.55 ± 0.84 vs. 11.44 ± 0.81) and fragmentation indices (0.33 ± 0.05 vs. 1.40 ± 0.30). BCL2L1 expression was lower, while Caspase-3 expression was significantly elevated in the sirtinol-treated group. Therefore, these findings suggest that sirtuins may elicit their effects through modifying autophagy and apoptosis, leading to developmental arrest and reducing the quality of porcine preimplantation embryos.

The regulation of autophagy in porcine blastocysts: Regulation of PARylation-mediated autophagy via mammalian target of rapamycin complex 1 (mTORC1) signaling.

Poly(ADP-ribosyl)ation (PARylation) acts as a modulator of selective autophagic degradation of ubiquitinated aggregates for cellular quality control, functioning in pro-survival role. It was reported previously that the inhibition of PARylation resulted in autophagy defects leading accumulation of ubiquitinated aggregates SQSTM1/p62 and apoptosis in porcine blastocysts. Thus, this study aims to investigate the mechanism between PARylation and autophagy in porcine blastocysts. In vitro produced (IVP) embryos were treated with 3-aminobenzamide (3ABA, poly (ADP-ribose) polymerase inhibitor) and/or rapamycin (RAPA, an mTORC1 inhibitor) during blastocyst formation. Then, these treated blastocysts were analyzed by real-time PCR, immunocytochemistry and TUNEL Assay. We found that the 3ABA treatment increased mTORC1 downstream target, phosphorylation of thr389 p70S6K (p-p70S6K-thr389), suggesting an increase in mTORC1 activity. Co-treatment with rapamycin (RAPA), mTORC1 inhibitor, restored the 3ABA-induced autophagy defects to those of the controls by normalizing mTORC1 activity. Moreover, autophagy induction, with only RAPA treatment, increased the rate of blastocyst development (70.05 ± 0.93 vs. 50.61 ± 3.49%), total cell number (58.48 ± 2.94 vs. 49.58 ± 2.43) and blastomere survival, but decreased the accumulation of SQSTM1/p62 aggregates. In summary, mTORC1 signaling is a key mechanism of PARylation-autophagy and its inhibition improved developmental ability and embryo quality by promoting selective autophagic degradation of ubiquitinated aggregates in porcine blastocysts. Therefore, these findings have significant implications for understanding the importance of autophagy regulation for successful in vitro production of porcine embryos.