- Ovarian steroidogenesis is heavily controlled by the formation and function of the theca cells. A condition known as polycystic ovarian disease in humans and cystic ovarian disease in cattle is due to abnormal steroidogenesis. Knowing more about theca cell formation and function can aid in gaining further knowledge about polycystic ovarian disease and cystic ovarian disease. Currently very little is known about the role theca cells play in these two diseases. The goal of this thesis research was to look at the effect of kit ligand neutralization on the growth of bovine follicles in culture. Ovariectomies were performed on Holstein and Jersey dairy cows to retrieve follicles. The effects of kit ligand replacement were observed on the growth of bovine follicles in a novel matrix-free 3D culture using round bottom low attachment plates. The effects of kit ligand replacement were also observed on the formation and function of the theca cell layer in those follicles. The results suggest that kit ligand is secreted by multilayer follicles, but only small antral follicles possess the receptor for kit ligand (c-kit). No statistically significant differences were found in all follicle types in survival rate or in the rate of growth when comparing two types of media used for in vitro follicle maturation (α-MEM and T-199). Additionally, no significant differences were observed in the percentage of surviving follicles of each type per media. Statistical significance was observed in the kit ligand treated group as the treatment tended to reduce the number of days it took a follicle to form an antrum. Both fast and slow antrum follicles that were treated with kit ligand developed a significantly larger diameter compared to the controls, but the fast antrum follicles died after two days. While not statistically significant, addition of kit ligand does appear to increase percent antrum formation.