Insulin improves in vitro survival of equine preantral follicles enclosed in ovarian tissue and reduces reactive oxygen species production after culture.

The research article focuses on the impact of insulin concentration on equine preantral follicles’ survival and growth within ovarian tissues when cultured in vitro. It uncovered that a physiological concentration of insulin aids the follicles’ growth and reduces oxidative stress.

Study Methodology

• The research involved investigating the effect of different insulin concentrations in the culture of equine preantral follicles within ovarian tissue.
• Ovarian tissue samples were either immediately fixed (noncultured control) or cultured for 1 to 7 days in an α-MEM(+) medium supplemented with 0 ng/mL, 10 ng/mL, or 10 μg/mL insulin.
• After the in vitro culture, the ovarian tissues were subjected to classical histology.
• The culture medium samples were collected after 1 and 7 days of culture to analyze steroid and ROS (Reactive Oxygen Species) levels.

Results and Findings

• The results showed that the percentage of morphologically normal follicles was significantly higher in the insulin-treated groups after one day of culture. More such follicles were observed after seven days of culture in medium supplemented with 10-ng/mL insulin.
• An increase in developing follicles (transition, primary, and secondary) between the ninth and tenth days of culture was noted only in the group treated with 10-ng/mL insulin.
• The production of Reactive Oxygen Species (ROS), potentially damaging oxygen compounds, was lower in medium cultured with 10-ng/mL insulin compared to other treatments, indicating a reduction in oxidative stress.
• Despite the different treatments, the ability of the ovarian tissue containing preantral follicles to produce estradiol and progesterone remained undifferentiated, showing equal levels of steroid production.

Conclusion

• The study concludes that employing a physiological concentration (10 ng/mL) of insulin as opposed to the previously reported concentration (10 μg/mL) enhances the survival and growth of equine preantral follicles in an in vitro culture setup.
• Moreover, the application of a given insulin concentration also reduced oxidative stress in the culture environment.
• The findings of this research offer insights into enhancing the in vitro survival and growth of preantral follicles, pointing to possible improvements in creating the optimal medium to support this process.