The gut microbiota: a double-edged sword in endometriosis†.

Endometriosis that afflicts one in 10 women of reproductive age is characterized by growth of endometrial tissue in the extra-uterine sites and encompasses metabolic-, immunologic-, and endocrine-disruption. Importantly, several comorbidities are associated with endometriosis, especially autoimmune disorders such as inflammatory bowel disease. Primarily thought of as a condition arising from retrograde menstruation, emerging evidence uncovered a functional link between the gut microbiota and endometriosis. Specifically, recent findings revealed altered gut microbiota profiles in endometriosis and in turn this altered microbiota appears to be causal in the disease progression, implying a bidirectional crosstalk. In this review, we discuss the complex etiology and pathogenesis of endometriosis, emphasizing on this recently recognized role of gut microbiome. We review the gut microbiome structure and functions and its complex network of interactions with the host for maintenance of homeostasis that is crucial for disease prevention. We highlight the underlying mechanisms on how some bacteria promote disease progression and others protect against endometriosis. Furthermore, we highlight the areas that require future emphases in the gut microbiome-endometriosis nexus and the potential microbiome-based therapies for amelioration of endometriosis.