Emerging bacterial factors for understanding pathogenesis of endometriosis

Abstract

The pathogenesis of endometriosis is a complex process, and recent research has introduced novel hypotheses in this field. This review summarizes recent studies on the pathogenesis of endometriosis. We focused on several classical hypotheses, as well as their interactions with the microenvironment of hormonal dependence and immunosuppression. Furthermore, we highlighted the emergence of bacterial factors associated with endometriosis. Recent advances in next-generation sequencing (NGS) have revealed the presence and detailed distribution of these bacteria as well as the involvement of specific bacteria in pathogenesis. These factors alter the microenvironment in the early stages of endometriosis development, leading to lesion formation. Understanding the mechanisms underlying the early development of endometriosis from a new perspective would be helpful for the development of novel therapeutic agents for endometriosis.

Keywords: Medical microbiology; Microbiology; Women’s health.

Figure 1

Relationship between bacteria and endometrial cells in the microenvironment of the endometrium In the endometrium, infected bacteria attract macrophages to the surrounding microenvironment, and transformed M2 macrophages produce TGF. Subsequently, endometrial fibroblasts transform into myofibroblasts in a TGF-rich microenvironment. These phenotypic transformations induce adhesion, migration, and proliferation at the ectopic site to develop endometriosis lesions. The presence of bacteria in the endometrium causes the transformation of fibroblasts that develop endometriosis.

Figure 2

Various hypotheses of endometriosis pathogenesis Classical hypotheses for endometriosis include retrograde menstruation, coelomic metaplasia, and stem/progenitor cells. Based on these theories, microenvironmental interactions between hormonal dependence and immune dysregulations are important aspects of the pathogenesis of endometriosis. Recently, the presence of bacteria has been highlighted, and various factors have been shown to be involved in the development of endometriosis. ER, estrogen receptor; PR, progesterone receptor.