Submission Number: CHA-4-23-1

Abstract Number: 176

CONTROL OF GRANULOSA CELL PROLIFERATION IN THE PRIMATE PERIOVULATORY FOLLICLE.

Charles L Chaffin* ¹, Kristine M Schwinof ¹ and Richard L Stouffer* ^1,2

Division of Reproductive Sciences, Oregon Regional Primate Research Center, Beaverton, OR, USA ¹
Department of Physiology and Pharmacology, Oregon Health Sciences University, Portland, OR, USA ²

Abstract:
The mechanisms whereby the gonadotropin surge terminates follicle growth and initiates luteal differentiation are poorly understood, especially in primates. This study examined gonadotropin and local (via steroid/progesterone, P) control of (1) mitosis (assessed by Ki-67 immunostaining), and (2) mRNA levels for activators (cyclins) and inhibitors (cyclin-dependent kinase inhibitors, CKI) of the cell cycle in granulosa cells of the primate ovulatory follicle. Adult, female rhesus monkeys received recombinant human gonadotropins (r-hFSH r-hLH; Ares Advanced Technology) to promote development of multiple preovulatory follicles. Granulosa cells or ovaries (n=3-5/time-point) were obtained before (0 h), 12, or 36 h after administering an ovulatory bolus of r-hCG (AAT) with or without the 3HSD inhibitor Trilostane (TRL, Sanofi) and the non-metabolizable progestin R5020. The percentage of Ki-67 positive cells decreased from 48% to 19% within 12 h of hCG (p<0.05). Steroid depletion did not affect the percentage of Ki-67 positive cells at 12 h. Cyclin D2 mRNA increased 1.8-fold by 12 h post-hCG (p<0.05), and steroid depletion did not alter mRNA levels. In contrast, cyclin B mRNA declined 3-fold within 12 h of hCG (p<0.05), and then remained at this level. Steroid depletion resulted in a significant increase in cyclin B mRNA (p<0.05) at both 12 and 36 h post-hCG that was reversible by R5020 at 36 h, but not 12 h. CKI p21^Cip1 increased 9-fold within 12 h of hCG (p<0.05), and was intermediate between 0 and 12 h values at 36 h post-hCG. CKI p27^Kip1 mRNA levels were low until 36 h, at which time they increased 30-fold (p<0.05). Steroid depletion did not alter p21^Cip1 or p27^Kip1 mRNA levels 36 h after an ovulatory stimulus. These data suggest that gonadotropin plays the major role in inhibiting granulosa cell mitosis early (12 h) in the periovulatory interval, while P may play a role later (36 h) in maintaining luteal cell quiescence. Gonadotropin and progesterone regulates the dynamic interaction of cyclins and CKIs that suppress the cell cycle during formation of a functional corpus luteum in primates. Supported by HD08302, HD20869, HD18185, RR00163.

Keywords: ovulation, proliferation, granulosa cell, monkey

This abstract is being presented at: 8:00 AM in session:
Ovulation