PCB2 improves porcine oocyte maturation by enhancing TZP-mediated cumulus-oocyte communication

Transzonal projections (TZPs)-mediated communication between oocytes and cumulus cells plays a critical role in oocyte maturation and developmental competence, and disruption of this communication during in vitro maturation (IVM) is considered a major factor limiting oocyte quality. This study investigated the effects of Procyanidin B2 (PCB2) on porcine oocyte maturation and the underlying mechanisms. PCB2 supplementation significantly increased polar body extrusion (71.49 ± 5.75% vs. 87.23 ± 2.67%, P < 0.05, in the Control and PCB2 groups, respectively) and blastocyst cell numbers (28.00 ± 2.60 vs. 35.58 ± 2.17, P < 0.05). In addition, PCB2 reduced intracellular reactive oxygen species levels (58.60 ± 2.75 vs. 46.41 ± 2.06, P < 0.001) and increased glutathione content in porcine oocytes (73.75 ± 1.19 vs. 76.93 ± 0.78, P < 0.05). PCB2 also promoted cumulus expansion (P < 0.05) and increased TZP abundance during IVM (P < 0.05). Furthermore, we discovered that gap junctional uncoupler carbenoxolone (CBX) treatment impaired oocyte maturation (P < 0.05), cumulus expansion (P < 0.05), oocyte viability (P < 0.001), and lipid content (P < 0.001), whereas PCB2 partially rescued these defects (P < 0.05). Collectively, these findings demonstrate that PCB2 improves porcine oocyte maturation through the combined interaction between improved redox homeostasis, enhanced cumulus cell function, cellular metabolism, and cumulus-oocyte communication.