Study question: What happens to the gut microbiota during development of murine endometriosis?
Summary answer: Mice with the persistence of endometrial lesions for 42 days develop a distinct composition of gut microbiota.
What is known already: Disorders in the immune system play fundamental roles in changing the intestinal microbiota. No study has used high-throughput DNA sequencing to show how endometriosis changes the gut microbiota, although endometriosis is accompanied by abnormal cytokine expression and immune cell dysfunction.
Study design, size, duration: This study includes a prospective and randomized experiment on an animal endometriosis model induced via the intraperitoneal injection of endometrial tissues.
Participants/materials, setting, methods: The mice were divided into endometriosis and mock groups and were sacrificed at four different time points for model confirmation and fecal sample collection. To detect gut microbiota, 16S ribosomal-RNA gene sequencing was performed. Alpha diversity was used to analyze the complexity and species diversity of the samples through six indices. Beta diversity analysis was utilized to evaluate the differences in species complexity. Principal coordinate analysis and unweighted pair-group method with arithmetic means clustering were performed to determine the clustering features. The microbial features differentiating the fecal microbiota were characterized by linear discriminant analysis effect size method.
Main results and the role of chance: The endometriosis and mock mice shared similar diversity and richness of gut microbiota. However, different compositions of gut microbiota were detected 42 days after the modeling. Among the discriminative concrete features, the Firmicutes/Bacteroidetes ratio was elevated in mice with endometriosis, indicating that endometriosis may induce dysbiosis. Bifidobacterium, which is known as a commonly used probiotic, was also increased in mice with endometriosis.
Large scale data: N/A.
Limitations, reasons for caution: More control groups should be further studied to clarify the specificity of the dysbiosis induced by endometriosis. This study was performed only on mice. Thus, additional data acquired from patients with endometriosis are needed in future research. We only detected the changes of gut microbiota at 42 days after the modeling, while the long-term effect of endometriosis on gut microbiota remains poorly understood. Moreover, we only revealed a single effect of endometriosis on gut microbiota.
Wider implications of the findings: This study provided the first comprehensive data on the association of endometriosis and gut microbiota from high-throughput sequencing technology. The gut microbiota changed with the development of endometriosis in a murine model. The communication between the host and the gut microbiota is bidirectional, and further studies should be performed to clarify their relationship.
Study funding/competing interest(s): This research was supported by Grant (81571417) from the National Science Foundation of China and Grant (2015GSF118092) from the Technology Development Plan of Shandong Province. The authors report no conflict of interest.