(320) Exploring the Effect of Insulin on Germ Cell Cyst Breakdown and Primordial Follicle Formation

Exploring the Effect of Insulin on Germ Cell Cyst Breakdown and Primordial Follicle Formation.

Kirsten A. Rasmussen1, Melissa Pepling1.

1.Department of Biology, College of Arts and Sciences, Syracuse University, Syracuse, New York, United States.


Abstract Text:

The ovarian reserve, essential for female fertility, is composed of primordial follicles - oocytes surrounded by pre-granulosa cells. Disruption in its formation during perinatal development may lead to conditions like Primary Ovarian Insufficiency (POI). During development, primordial germ cells migrate to the gonad and become oogonia, which divide mitotically with incomplete cytokinesis to form germ cell cysts. These oogonia enter meiosis, becoming oocytes that arrest in prophase I. The cysts then break down, allowing individual oocytes to be encased by pre-granulosa cells to form primordial follicles. While KITL has been established as a crucial regulator of oogenesis as well as cyst breakdown and primordial follicle formation through KIT signaling, the role of insulin during cyst breakdown and primordial follicle formation remains unclear. Previous studies have shown that insulin is vital for promoting later follicle development and works additively with KITL, but its function during cyst breakdown and primordial follicle formation has yielded conflicting results. Recent research using a gestational diabetes mouse model revealed that fetal ovaries exhibited elevated glucose and insulin levels as well as increased primordial follicle numbers, though the individual contributions of glucose versus insulin remained undetermined. This study investigates the role of insulin during germ cell cyst breakdown and primordial follicle assembly and explores potential interactions between KIT and insulin signaling pathways during this transition. Using in vitro ovarian organ culture, we treated PND 1 mouse ovaries with varying concentrations of insulin (0.1-10 μg/mL), KIT (20 μg/mL) + insulin, glucose (25mM), or control media until PND 5. Our immunostaining and imaging analysis revealed that insulin promotes oocyte cyst breakdown and primordial follicle formation, as evidenced by measurements of both total oocyte count and the percentage of single oocytes.These findings advance our understanding of ovarian reserve establishment and may identify novel therapeutic targets for reproductive disorders such as POI.