Effect of Exogenous Melatonin on the Development of Mice Ovarian Follicles and Follicular Angiogenesis

In mammalian, the periodic growth and development of ovarian follicles constitutes the physiological basis of female estrus and ovulation. Concomitantly, follicular angiogenesis exerts a pivotal role in the growth of ovarian follicles. Melatonin (N-acetyl-5-methoxytryptamine, Mel), exists in follicle fluid, was suggested to affect the development of follicles and angiogenesis. This research was conducted to investigate the effects and mechanisms of Mel on the development of ovarian follicles and its angiogenesis. In total, 40 ICR mice at age of 3 weeks were allocated into four groups at liberty: control, Mel, FSH and FSH + Mel for a 12-day trial. Ovaries were collected at 8:00 a.m. on Day 13 for detecting the development of ovarian follicles and angiogenesis. Results indicated that Mel promoted the development of ovarian follicles of 50–250 μm (secondary follicles) and periphery angiogenesis, while FSH remarkably increased the number of antral follicles and periphery angiogenesis. Mechanically, Mel and FSH may regulate the expression of VEGF and antioxidant enzymes in different follicular stages. In conclusion, Mel primarily acted on the secondary follicles, while FSH mainly promoted the development of antral follicles. They both conduced to related periphery angiogenesis by increasing the expression of VEGF. These findings may provide new targets for the regulating of follicular development.