Abstract

Objective: To investigate the presence of caspase-3 and Bcl-2 concentration in human endometrial tissue throughout the menstrual cycle, and study the effect of nitric oxide (NO) on cell proliferation and apoptosis during culture. Design: Expression of caspase-3 and Bcl-2 concentration in endometrial explants, and examination of L-arginine (L-Arg) effect on epithelial and stromal cell proliferation and apoptosis in vitro. Setting: Prospective study. Patient(s): Twenty-seven eumenorrheic women (37 ± 1.2 years). Intervention(s): Endometrial samples were obtained with Pipelle suction curette from the corpus of the uterus. Main outcome measure(s): Apoptosis (annexin V-FITC binding), Bcl-2 concentration (ELISA), caspase-3 (immunohistochemistry), cell proliferation (spectrophotometric assay), and gene expression (RT-PCR). Result(s): Caspase-3 was detected by immunoassay in epithelial tissue throughout the menstrual cycle and in stroma during secretory phase. The Bcl-2 concentration was similar in endometrial homogenates obtained throughout the menstrual cycle, but L-Arg decreased Bcl-2 only in endometrium from the proliferative phase. In epithelial cells, NO increased apoptosis by 2. 1 ± 0.2-fold, augmented mRNA expression of Bax, and reduced expression of Bcl-2 compared with basal cultures. In stromal cells, NO increased cell proliferation in a dose-dependent manner, an effect that was blocked by a NO synthase inhibitor. Conclusion(s): These data indicate that NO has a differential regulatory function on endometrial cell survival, as indicated by the results on stromal cell proliferation and epithelial cell apoptosis during culture, which suggests paracrine interactions between both cell types. © 2004 by American Society for Reproductive Medicine.