199 Effects of stem cell factor on the in vitro maturation of porcine oocytes and subsequent development following in vitro fertilization

The cytokine stem cell factor (SCF) interacts with the c-kit receptor (CD117) to activate signaling pathways that promote follicular development and support oocyte survival. This study aimed to investigate the effects of SCF treatment on IVM in pigs. During IVM, recombinant human SCF protein (R&D Systems) was added to M199 medium at concentrations of 0, 1, 10, and 100 ng mL⁻¹, along with FSH and LH. More than 520 cumulus–oocyte complexes (COCs) were used per group. COCs were incubated in a humidified atmosphere of 5% CO₂ at 37°C for 44 h. Following IVM, nuclear and cytoplasmic maturation were assessed, and the developmental competence of embryos generated via IVF was analyzed. For IVF, MII-stage oocytes were co-incubated with sperm at a final concentration of 5.0 × 10⁵ sperm mL⁻¹ in mTBM droplets for 5 h at 39°C in a humidified atmosphere of 5% CO₂ and 95% air. After fertilization, porcine embryos were cultured in MU4 medium and incubated in a humidified atmosphere of 5% CO₂ and 5% O₂ at 37°C for 7 days. Each experiment consisted of at least four replicates, and comparisons among all groups were conducted using one-way ANOVA followed by the Tukey range test. After 44 h of IVM, oocytes treated with 10 ng mL⁻¹ of SCF exhibited a significantly decreased intracellular ROS level (P < 0.05), with no significant change in the rate of nuclear maturation. Transcript levels of genes associated with cumulus expansion, specifically PTGS2 and HAS2, were significantly elevated (P < 0.05) in cumulus cells treated with 1 ng mL⁻¹ and 10 ng mL⁻¹ of SCF compared with the control, as determined by RT-qPCR. Additionally, mRNA levels of pro-apoptotic genes, such as CASP3 and BAX, were significantly decreased (P < 0.05) in oocytes from the 1 ng mL⁻¹ and 10 ng mL⁻¹ SCF treatment groups. Following IVF, at the 4-cell stage, the 1 ng mL⁻¹ and 10 ng mL⁻¹ SCF treatment groups showed a significantly lower (P < 0.05) expression of cathepsin K and a significantly higher (P < 0.05) expression of Cyto ID, an autophagy indicator, compared with the control group. Furthermore, the group treated with 10 ng mL⁻¹ of SCF exhibited a notably higher (P < 0.05) rate of blastocyst formation (36.2 ± 1.3%) compared with the control group (28.9 ± 2.1%). Blastocysts derived from oocytes treated with 10 ng mL⁻¹ of SCF had a significantly greater (P < 0.05) total cell count (91.7 ± 12.8) and a higher number of SOX2-expressing cells (18.2 ± 3.5), indicative of epiblasts, compared with the control group (62.3 ± 6.8 and 8.2 ± 1.5, respectively). These results illustrate that SCF treatment during IVM of porcine oocytes may enhance autophagy potential, decrease apoptotic potential, and induce blastocyst development. The system might be used to improve pig IVM and produce healthier embryos.