Protease genes were identified that exhibited increased mRNA levels before and immediately after rupture of the naturally selected, dominant follicle of rhesus macaques at specific intervals after an ovulatory stimulus. Quantitative real-time PCR validation revealed increased mRNA levels for matrix metalloproteinase (MMP1, MMP9, MMP10, and MMP19) and a disintegrin and metalloproteinase with thrombospondin-like repeats (ADAMTS1, ADAMTS4, ADAMTS9, and ADAMTS15) family members, the cysteine protease cathepsin L (CTSL), the serine protease urokinase-type plasminogen activator (PLAU), and the aspartic acid protease pepsinogen 5 (PGA5). With the exception of MMP9, ADAMTS1, and PGA5, mRNA levels for all other up-regulated proteases increased significantly (P Ͻ 0.05) 12 h after an ovulatory human chorionic gonadotropin (hCG) bolus. MMP1, ADAMTS1, CTSL; PLAU; and PGA5 also exhibited a secondary increase in mRNA levels in 36-h postovulatory follicles. To further determine metalloproteinase involvement in ovulation, vehicle (n ϭ 4) or metalloproteinase inhibitor (GM6001, 0.5 g/follicle, n ϭ 8) was injected into the preovulatory follicle at the time of hCG administration. Of the eight GM6001-injected follicles, none displayed typical stigmata indicative of ovulation at 72 h after hCG; whereas all four vehicle-injected follicles ovulated. No significant differences in mean luteal progesterone levels or luteal phase length occurred between the two groups. Subsequent histological analysis revealed that vehicle-injected follicles ruptured, whereas GM6001-injected follicles did not, as evidenced by an intact stroma and trapped oocytes (n ϭ 3). These findings demonstrate metalloproteinases are critical for follicle rupture in primates, and blocking their activity would serve as a novel, nonhormonal means to achieve contraception. (Endocrinology 152: 3963-3974, 2011) A fter the midcycle LH surge, processes critical for the release of the oocyte from the preovulatory follicle are initiated. The release of the oocyte from the follicle requires highly coordinated events that include the degradation of type IV collagen, laminin, and fibronectin that forms the basement membrane surrounding the follicle as well as the degradation of type I collagen within the follicle wall at the site of rupture (1-5). The degradation and cellular reorganization that takes place also allows for the invasion of newly forming blood vessels into the mural granulosa layer of the follicle (6). Such a high degree of extracellular matrix (ECM) remodeling and cellular reorganization is associated with increased gelatinase, collagenase, and serine protease activities (1). Furthermore, proteolytic activities are required within the follicle to ensure significant expansion of the intercellular space be-
