Gonadotrophin regulation of production of tissue inhibitor of metalloproteinases-1 by luteinized human granulosa cells: a potential mechanism for luteal rescue

Abstract

Human granulosa cells were maintained in culture with extracellular matrix in the presence or absence of human chorionic gonadotrophin (HCG) using a defined culture medium. Such cultures are maintained by gonadotrophin in a manner suggesting that features of 'luteal rescue' may be occurring in vitro. Western analysis of culture medium demonstrated that the granulosa cells produced tissue inhibitor of metalloproteinases (TIMP)-1 but not TIMP-2. The presence of TIMP-1 in cultured cells was also detected immunocytochemically. Immunoassay of TIMP-1 output revealed that HCG exposure for 7 days caused a 2-fold increase in TIMP-1 production versus control reaching maximum at approximately 1 ng HCG/ml. The sensitivity of this response to HCG was similar to that observed for stimulation of progesterone production. Delayed addition of HCG, from day 4 of culture, elicited increases in TIMP-1 which were evident within 24 hours, and were not explained by changes in cell replication or survival. Removal of HCG from cultures previously luteinized with HCG for 6 days resulted in a fall in TIMP-1 production. Thus TIMP-1 production by luteinized granulosa cells in culture is gonadotrophin dependent. We speculate that prolonged cellular function associated with 'luteal rescue' may result from increased extracellular matrix stability mediated by up-regulation of TIMP-1 production.