117 Kit ligand enhances growth and nuclear maturation of buffalo oocytes in vitro

Abstract

This study aimed to investigate the effect of Kit ligand (KL), a growth factor that regulates folliculogenesis in mammalian ovaries, on growth of buffalo oocytes in early antral follicles in vitro. Cumulus-oocyte complexes were dissected from early antral follicles (1 mm) of slaughtered buffaloes and cultured in Dulbecco’s minimum essential medium supplemented with fetal bovine serum, sodium pyruvate, gentamycin, hypoxanthine, dexamethasone, cysteine, polyvinylpyrolidione, l-ascorbic acid, oestradiol-17β, and androstenedione in a 96-well culture plate at 38.5°C under an atmosphere of 5% CO₂ in air for 6 days. The culture medium was supplemented with 0, 50, and 100 ng/mL KL (recombinant human SCF, Cat. No. H8416, R&D Systems, Minneapolis, MN, USA). Sixty oocytes were cultured in each group with 6 replications. In vitro-grown oocytes were cultured for maturation in tissue culture medium-199 supplemented with 5% fetal bovine serum, sodium pyruvate, gentamycin, and 100 ng/mL FSH at 38.5°C for 24 h under an atmosphere of 5% CO₂ in air. The oocytes were then stained with aceto-orcein and examined under a differential interference contrast microscope. Data were analysed using SAS/STAT version 9.1.3 for Windows (SAS Institute Inc., Cary, NC, USA) by one-way ANOVA and means compared with Tukey’s HSD test. The mean diameter of oocytes measured at the time of seeding on the culture substrate was 100.6 ± 0.4 μm (n = 180). After 6 days of culture, the diameters of oocytes increased to 110.8 ± 0.5, 114.0 ± 0.5, and 115.0 ± 0.6 µm in 0, 50, and 100 ng/mL KL-treated groups, respectively. The survival rates were 60.0 ± 6, 81.2 ± 1.2, and 92.0 ± 4.9% in 0, 50, and 100 ng/mL KL-supplemented oocytes at Day 6. Moreover, KL pretreatment enhanced maturation of buffalo oocytes dose dependently. A small proportion of oocytes (8.4%) treated with 50 ng/mL KL reached the MII stage. This number increased to 25% when oocytes were treated with 100 ng/mL KL. These results show that KL enhances growth, viability, and meiotic progression of buffalo oocytes in vitro.