Interleukin-6 supplementation during in vitro maturation improves developmental competence of in vitro fertilized porcine oocytes

Abstract

Interleukin 6 (IL-6) is a cytokine physiologically expressed within the reproductive tract, where it plays a crucial role in cellular communication and processes such as ovulation and implantation. These processes and the presence of embryos alter the immune response of the female reproductive tract in vivo, a physiological event of utmost relevance. Mimicking such physiological environment may optimize porcine in vitro embryo production (IVP). This study aimed to assess the impact of IL-6 supplementation during in vitro maturation (IVM) and/or in vitro culture (IVC) on the developmental competence of pig oocytes fertilized in vitro. In the first experiment, cumulus-oocytes complexes (COCs) were matured in media containing graded IL-6 concentrations (0-200 ng/mL). IL-6 did not affect maturation, fertilization, cleavage, or blastocyst formation rates. However, 100 ng/mL IL-6 significantly (P < 0.05) improved chromosome alignment, meiotic spindle formation, blastocyst efficiency, and total cell number compared to controls. In the second experiment, COCs were matured and fertilized without IL-6 supplementation. The resulting presumptive zygotes were cultured in IVC media with graded concentrations of IL-6 (0-200 ng/mL). IL-6 supplementation during IVC did not enhance developmental competence. Conversely, the highest IL-6 concentration significantly (P < 0.05) reduced cleavage rate. In the third experiment, combined supplementation of 100 ng/mL IL-6 during IVM and 10 ng/mL during IVC showed no additional improvements compared to IL-6 supplementation during IVM alone. In conclusion, the results of this study indicate that IL-6, particularly when added during oocyte maturation, positively impacts porcine in vitro embryo production.