412. The role of macrophages in regulating uterine epithelial cell proliferation

Abstract

During the oestrous cycle, uterine epithelial cells respond to ovarian steroid hormones by producing an array of cytokines and chemokines that cause macrophage recruitment into the uterus and regulate macrophage activation phenotype. In turn, growth factors and cytokines synthesised by macrophages potentially impact epithelial cell proliferation, secretory function and receptivity to embryo attachment. To investigate the hypothesis that uterine macrophages are essential contributors to the proliferation of uterine epithelial cells, we have used an ovariectomy and steroid replacement model in CD11b-DTR ‘Mac-terminator' mice. These mice are engineered for CD11b promoter-driven expression of the monkey diphtheria toxin (DT) receptor, allowing acute systemic ablation of macrophages by administration of human diphtheria toxin (DT). CD11b-DTR mice were ovariectomised, then 2–4 weeks later were primed with E ₂, followed by administration of DT (25 ng/g, ip) to effect macrophage depletion, and BrDU to label proliferating cells. Control mice were given PBS instead of DT. Uterine tissues were stained with F4/80 to detect macrophages, and anti-BrDU to detect BrDU+ epithelial cell nuclei. DT treatment was associated with a depletion of >90% of F4/80+ uterine macrophages. However, the numbers of BrDU+ epithelial cells and the architecture of the luminal epithelial surface and abundance of epithelial glands were similar in control and DT-treated uterine tissues. These data suggest that resident macrophages may not be essential for oestrogen-driven uterine epithelial cell proliferation. In ongoing experiments we are assessing the effect of macrophage depletion on epithelial cell expression of functional markers including those involved in regulation of embryo attachment.