Abstract
The human endometrial gland plays a vital role in maternal immune tolerance and placental development. Decidual macrophages are the major phagocytic cells that regulate tissue remodeling during pregnancy. This study examines the regulatory effect of endometrial gland secretome on macrophage polarization and functions using endometrial organoid. We demonstrated that endometrial organoids treated with hormones mimicking the environment of the secretory phase/early pregnancy polarize macrophages to acquire a decidua-like macrophage phenotype, including higher expressions of decidual macrophage markers, reduced phagocytic capacity and altered cytokine secretion. The results indicated that endometrial gland secretomes are critical for maintaining macrophage homeostasis at the maternal-fetal interface.