PROJECT SUMMARY/ABSTRACT: Endometriosis is a gynecological disease resulting from abnormal growth of endometrial tissue outside the uterine cavity. This disease causes chronic pain, extreme pain with menstruation, and/or infertility in at least 7.4 million American women per year. The annual cost burden exceeds $70 billion and no cure or effective treatments exist. A common therapy is the suppression of ovarian estrogen production, but upon cessation of treatment >70% of women report symptomatic disease. Women with endometriosis have increased immune cells in their peritoneal cavity and often have higher incidences of autoimmune disorders; however, the pathogenesis of endometriosis remains poorly understood. Data from our mouse model of endometriosis, in which donor uterine tissue is freely dispersed into the peritoneal cavity of an immunocompetent host, has uncovered that initiation of endometriosis is dependent on the immune system. These data from our mouse model strongly correlate with alterations seen in women. Our long-term goal is to contribute toward the development of mechanism-based strategies to prevent, diagnose, and/or treat endometriosis. The objective in this proposal is to determine the role of neutrophil and macrophage mediated signaling on uterine tissue attachment during the immune-dependent phase of endometriosis. Therefore, we hypothesize the crosstalk among uterine cells, PMNs, and MΦs in women with EMS secrete matrisome and matrisome associated factors that promote and support EMS lesion establishment. The following aims are designed to test this hypothesis: Aim 1 will identify the neutrophil population and characterize how their secreted signaling molecules contribute to endometriosis lesion attachment. Aim 2 will identify the macrophage population and characterize how secreted signaling molecules contribute to endometriosis lesion survival. Aim 3 will uncover key matrisome factors that induce uterine tissue to form EMS lesions in vitro and in vivo. At the successful completion of this proposed research, the results are expected to have an important positive impact on the understanding of endometriosis. The data will contribute substantively to a mechanism based framework to elucidate endometriosis disease initiation that will, in turn, provide new opportunities for identifying targets for the development of novel therapeutics.