Fig. 1: The schematic model illustrates aging-related differences in oocyte and follicle development between young and middle-aged ovaries.

In young ovaries, active angiogenesis supports abundant blood vessel formation and a healthy stromal environment, ensuring an adequate supply of nutrients and hormones for follicle growth and the maintenance of high-quality oocytes (left). In contrast, reduced angiogenesis in middle-aged ovaries leads to poor vascularization and an unhealthy stromal environment, resulting in insufficient nutrient and hormone supply and subsequently lower-quality oocytes (right). Pink dots represent nutrients, and purple dots represent hormones.