The Abundance and Function of Neutrophils in the Endometriosis Systemic and Pelvic Microenvironment

Figure 1

Inflammatory events in menstruation. (a) Ovarian-derived estradiol and progesterone play a significant role in the structure and shape of the endometrium throughout the menstrual cycle. (b) Progesterone withdrawal leads to the release of chemokines into the surrounding tissues and the recruitment of neutrophils into the endometrium. Macrophages may have a proinflammatory (M1) phenotype in the early stages, and their phagocytic clearance of apoptotic cells is required to reduce local inflammation. Eosinophils are also recruited, while local mast cells become highly active and uterine natural killer (uNK) cells proliferate and release cytolytic chemicals. As these cells undergo a phenotypic shift, MMPs and degradative enzymes are released, stimulating the MMP activation cascade and driving ECM breakdown and endometrial rupture. (c) After menstruation, macrophages remove cellular debris while neutrophils of different phenotypes assist in the remodeling and repair of the functional endometrial layer.