Production of matrix metalloproteinases by cultured bovine theca and granulosa cells

Matrix metalloproteinases (MMPs) degrade the proteinaceous components of the extracellular matrix and are presumably essential for follicular growth culminating in ovulation or atresia. The objectives of this study were to characterize the gelatinolytic and caseinolytic MMPs secreted by cultured bovine thecal and granulosal cells and to determine the effect of luteinizing hormone (LH) on MMP secretion. Thecal and granulosal cells were collected from small bovine follicles (<5 mm) on day 2 or 5 of the estrous cycle (day 0 = estrus). A serum-free culture system was utilized in which bovine thecal and granulosal cells do not spontaneously luteinize, but produce androstenedione and estradiol in response to physiological concentrations of LH and follicle-stimulating hormone (FSH) respectively. The effect of LH (0, 1 or 100 ng/ml) on MMP production was determined in conditioned media collected every 48 h for 144 h. MMPs were detected by gelatin and casein zymography and MMP activity was quantified by image analysis. Thecal and granulosal cell conditioned media contained MMPs that had a relative molecular size (Mr) ranging from 53 000 to 200 000 and addition of 1,10 phenanthroline (MMP inhibitor) blocked gelatinolytic and caseinolytic activity. Patterns of gelatinolytic activity in thecal and granulosal cell conditioned media differed over time with theMr62 000 and 83 000 MMPs being increased (P< 0.05) and theMr53 000 MMP being decreased (P< 0.05) at 96 h of culture. LH (1 or 100 ng/ml) increased (P< 0.05) gelatinolytic activity of theMr53 000 and 62 000 gelatinases within thecal cell conditioned media but not granulosal cell conditioned media. TheMr62 000 and 83 000 gelatinolytic activities corresponded to the active forms of gelatinase A (Mr62 000) and B (Mr, 83 000) and gelatinase A was detected in thecal cell conditioned media by Western blot analysis. Caseinolytic activity (Mr83 000) was detected in both thecal and granulosal cell conditioned media and increased from 48 to 96 h. In summary, thecal and granulosal cells secrete gelatinolytic and caseinolytic MMPs and thecal cell production of gelatinase A was stimulated by LH.

Evidence that Cocaine- and Amphetamine-Regulated Transcript Is a Novel Intraovarian Regulator of Follicular Atresia

We recently obtained evidence that cocaine- and amphetamine-regulated transcript (CART), a potent anorectic neuropeptide, is expressed in the bovine ovary. The objectives of this study were to characterize bovine ovarian CART and determine its localization, regulation, and regulatory role during follicular development. CART mRNA was detected in stroma of adult ovaries and in large follicles, but was undetectable in several peripheral tissues, fetal ovaries, and corpora lutea. Within the ovary, CART mRNA and peptide were localized to the granulosal layer of some, but not all, antral follicles, with low, but detectable, expression in oocytes and cumulus cells. CART mRNA was undetectable in granulosal cells of dominant ovulatory follicles collected before and after the preovulatory gonadotropin surge, but was detected in the granulosal layer of adjacent subordinate follicles. In addition, amounts of CART mRNA and follicular fluid concentrations of CART peptide were greater in subordinate follicles vs. dominant follicles of the first follicular wave. Furthermore, CART treatment inhibited basal estradiol production, but not progesterone production, by granulosal cells in a dose-dependent fashion, and the effect was dependent on stage of cell differentiation. We conclude that granulosal cell CART expression is temporally regulated and potentially associated with follicle health status, and CART can inhibit granulosal cell estradiol production. Thus, CART may be a novel local regulator of follicular atresia in the bovine ovary.