Connective Tissue Growth Factor Expression in the Human Corpus Luteum: Paracrine Regulation by Human Chorionic Gonadotropin

Abstract

The molecular mechanisms of luteolysis and its inhibition during maternal recognition of pregnancy remain unclear. The objective of this study was to investigate the differential regulation of connective tissue growth factor (CTGF) expression in human corpora lutea using in vivo and in vitro models. Corpora lutea from different stages of the luteal phase and after luteal rescue with human chorionic gonadotropin (hCG) were studied. Primary cultures and cocultures of luteinized granulosa cells and luteal fibroblast-like cells were performed. This study was performed at the research center of a university teaching hospital. Women with regular cycles having hysterectomy for nonmalignant conditions and women undergoing oocyte collection for assisted conception were studied. CTGF localization was determined by in situ hybridization, and expression by quantitative RT-PCR. The outcome measures were the effect of hCG on the expression and localization of CTGF mRNA in human corpora lutea and the effect of hCG on CTGF expression in primary cultures of luteinized granulosa cells and luteal fibroblast-like cells. Luteal rescue reduced CTGF expression compared with that in the late luteal phase (P < 0.05). CTGF expression was localized to fibroblast-like cells and endothelial cells of larger blood vessels, not to steroidogenic cells. The expression of CTGF by fibroblast-like cells in vitro was not regulated by hCG. When cocultured with luteinized granulosa cells, fibroblast-like cell CTGF expression was inhibited by hCG (P < 0.001). This effect was independent of stimulated progesterone concentrations and was not blocked by follistatin or indomethacin. Both IL-1alpha (P < 0.05) and cAMP (P < 0.001) inhibited CTGF expression in fibroblast-like cells. These results provide evidence for negative regulation of CTGF by hCG during luteal rescue mediated by paracrine signals.