The mechanisms that control the preantral to early antral follicle transition and the strategies to have efficient culture systems to promote their growth in vitro

Preantral to early antral follicles transition is a complex process regulated by endocrine and paracrine factors, as well as by a precise interaction among oocyte, granulosa cells and theca cells. Understanding the mechanisms that regulate this step of folliculogenesis is important to improve in vitro culture systems, and opens new perspectives to use oocytes from preantral follicles for assisted reproductive technologies. Therefore, this review aims to discuss the endocrine and paracrine mechanisms that control granulosa cell proliferation and differentiation, formation of the antral cavity, estradiol production, atresia, and follicular fluid production during the transition from preantral to early antral follicles. The strategies that promote in vitro growth of preantral follicles are also discussed.

Automated summary

The transition from preantral to early antral follicles is a complex process regulated by endocrine and paracrine factors, as well as by interactions among oocyte, granulosa cells, and theca cells. Understanding the mechanisms that control this transition is important for improving in vitro culture systems and utilizing oocytes from preantral follicles in assisted reproductive technologies. This review discusses the endocrine and paracrine mechanisms involved in granulosa cell proliferation and differentiation, antral cavity formation, estradiol production, atresia, and follicular fluid production during this transition. The strategies for promoting in vitro growth of preantral follicles are also explored.