Abstract
The aim of this study was to investigate the effect of bioactive peptides (BAPT) from animal sources on the development of mouse preantral follicles in vitro. Preantral follicles were isolated and randomly divided into the following groups: an untreated group (control) and three groups supplemented with 20, 40 and 60 μg/mL BAPT, respectively. After establishing the in vitro follicle culture, the gene expression levels and hormone levels were quantified. After in vitro maturation, the developmental rates, reactive oxygen species (ROS) production levels and mitochondrial distributions of MII oocytes were investigated, followed by the analyses of embryonic developmental rates after in vitro fertilization.The results showed that BAPT promoted the growth of mouse preantral follicles. Notably, after 14 d of in vitro culture, the levels of 17 β-estradiol and progesterone were up-regulated with BAPT treatments. Moreover, the expression levels of Oct4, Bmp15, GDF9, FOXO3, Zp3, FOXL2, Inhibin alpha, SOD2, Catalase, GPx and Bcl-2 in the developing follicles were significantly up-regulated after BAPT treatments (P < 0.05), while BAPT significantly inhibited the expression levels of BAX (P < 0.05). Following BAPT treatments, the ROS production levels of MII oocytes were decreased while the mitochondrial distributions were significantly enhanced. Furthermore, increased maturation rates, fertilization and embryonic developmental rates were found in these BAPT-treated groups (P < 0.05).These results demonstrated that BAPT significantly improved the development of preantral follicles in vitro by reducing ROS-dependent cellular damages and by enhancing mitochondrial distributions, thereby promoting the further applications of animal-derived BAPT in biomedical research.
Highlights
Folliculogenesis, a major issue related with mammalian ovulation and fertility, occurs as a complex and dynamic process within female ovaries, which could be affected by multiple endocrine and intraovarianDue to the progressing development of assisted reproductive biotechnologies, these culture and maturation models of follicles mimic the native environmentalLiu et al Journal of Ovarian Research (2020) 13:108 differences of the developing follicles in vitro to obtain the functional germ cells [4]
On day 14, the diameter of follicles significantly increased from 133.66 ± 6.85 μm in the control group, 160.89 ± 7.55 μm in the bioactive peptides (BAPT) 20 group, 187.22 ± 7.36 μm in the BAPT 40 group to 214.56 ± 9.26 μm in the BAPT 60 group (P < 0.05), respectively
After 21 d in vitro culture, the mean diameter of follicles in the BAPT 40 group (252.00 ± 8.93 μm) and BAPT 60 group (290.78 ± 8.02 μm) were significantly higher than that of control group (204.89 ± 5.60 μm) and BAPT 20 group (222.78 ± 11.51 μm) (P < 0.05), which further indicated that BAPT treatment significantly enhanced the growth of isolated follicles in a dose-dependent manner
Summary
Folliculogenesis, a major issue related with mammalian ovulation and fertility, occurs as a complex and dynamic process within female ovaries, which could be affected by multiple endocrine and intraovarianDue to the progressing development of assisted reproductive biotechnologies, these culture and maturation models of follicles mimic the native environmentalLiu et al Journal of Ovarian Research (2020) 13:108 differences of the developing follicles in vitro to obtain the functional germ cells [4]. The addition of antioxidants to follicle cultures as ROS scavengers could prevent or decrease harmful damages, resulting in increased qualitiy of germ cells [14,15,16]. Different antioxidants, such as rutin [17], β-mercaptoethanol [18] and α lipoic acid [19], have been routinely applied to the culture system of developing follicles, the effect of bioactive peptides (BAPT), natural antioxidants derived from various food or animals sources [20] on the development of mammalian preantral follicles has not yet been investigated
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