An ex vivo ovulation system enables the discovery of novel ovulatory pathways and nonhormonal contraceptive candidates†

Abstract

Ovulation is an integral part of women's menstrual cycle and fertility. Understanding the mechanisms of ovulation has broad implications for the treatment of anovulatory diseases and the development of novel contraceptives. Now, few studies have developed effective models that both faithfully recapitulate the hallmarks of ovulation and possess scalability. We established a three-dimensional encapsulated in vitro follicle growth (eIVFG) system that recapitulates folliculogenesis and produces follicles that undergo ovulation in a controlled manner. Here, we determined whether ex vivo ovulation preserves molecular signatures of ovulation and demonstrated its use in discovering novel ovulatory pathways and nonhormonal contraceptive candidates through a high-throughput ovulation screening. Mature murine follicles from eIVFG were induced to ovulate ex vivo using human chorionic gonadotropin and collected at 0, 1, 4, and 8 hours post-induction. Phenotypic analyses confirmed key ovulatory events, including cumulus expansion, oocyte maturation, follicle rupture, and luteinization. Single-follicle RNA-sequencing analysis revealed the preservation of ovulatory genes and dynamic transcriptomic profiles and signaling. Soft clustering identified distinct gene expression patterns and new pathways that may critically regulate ovulation. We further used this ex vivo ovulation system to screen 21 compounds targeting established and newly identified ovulatory pathways. We discovered that proprotein convertases activate gelatinases to sustain follicle rupture and do not regulate luteinization and progesterone secretion. Together, our ex vivo ovulation system preserves molecular signatures of ovulation, presenting a new powerful tool for studying ovulation and anovulatory diseases as well as for establishing a high-throughput ovulation screening to identify novel nonhormonal contraceptives for women.

Keywords: RNA-sequencing; nonhormonal contraceptive; ovulation; proprotein convertase; soft-clustering.