(331) Ovulatory Signals Stimulate Active Theca Cell Migration

1. Department of Biomedical and Translational Sciences, Macon and Joan Brock Virginia Health Sciences, Eastern Virginia Medical School at Old Dominion University, Norfolk, VA

2. Department of Biological Sciences, Old Dominion University, Norfolk, VA

3. Department of Obstetrics and Gynecology, University of Kentucky, Lexington, KY

Abstract Text:

Theca cells are an integral component of the ovarian follicle. Theca cells synthesize all androgens produced by the follicle.  Androgens are then converted into estrogens by granulosa cells. After the ovulatory luteinizing hormone (LH) surge, oocyte release occurs concomitantly with the rapid transformation of the follicle remnant into the corpus luteum. During this process, theca cells integrate into the luteinizing granulosa cell layer. Whether theca cell movement during ovulation/luteinization is the result of passive relocation or if it is an active, intentional process of migration has not been investigated. We hypothesize that theca cells actively migrate during ovulation in response to hCG and/or hCG-stimulated local mediators of ovulation. We have previously shown that granulosa cells of the ovulatory follicle produce neurotensin (NTS) in response to the LH surge or the LH receptor ligand hCG, and that the local action of NTS is essential for ovulation to occur. Theca cells express receptors for LH/hCG as well as NTS, so either stimulus may alter theca cell function. To determine the role of hCG and hCG-stimulated NTS in theca cell migration in vivo, a vehicle control or a NTS receptor antagonist was injected into the adult female cynomolgus macaque ovulatory follicle, and hCG was administered systemically. After 48 hours, the ovaries were removed and fixed for immunofluorescent detection of theca cells. hCG stimulated theca cell invasion from the surrounding stroma into the ovulatory follicle.  Follicle injection of a NTS receptor antagonist reduced the hCG-stimulated increase in theca cell invasion by 66%, demonstrating that both hCG and NTS can stimulate theca cell migration in vivo. Additional studies were performed in vitro to determine if hCG or NTS acts directly at theca cells to stimulate migration. Primary theca cells isolated from monkey ovaries were cultured in vitro and allowed to migrate through a porous membrane towards hCG or NTS. hCG and NTS increased theca cell migration 66% above basal migration and 71% above basal migration, respectively. NTS-stimulated theca cell migration was blocked in the presence of a NTS receptor antagonist in vitro. Furthermore, assessment of theca cell migration through a three-dimensional (3D) matrix determined that NTS increased both theca cell migration distance by 42% and the number of theca cell offshoots by 70% over basal levels. In contrast, hCG did not stimulate theca cell migration in our 3D assay. Taken together, these data suggest that theca cells actively migrate in response to hCG and NTS during ovulation. Importantly, these findings indicate that LH/hCG-stimulated theca cell migration in vivo may be dependent upon locally-produced NTS. Future investigation will query the mechanism by which theca cells migrate and the role of extracellular matrix in ovulatory migration. These studies will contribute to our overall understanding of theca cell function during ovulation and corpus luteum development, and may shed light on the development of future fertility-improving treatments or contraceptive strategies. This work was supported by a generous product donation from Organon and NIH HD097675 to DMD and TEC.