2023-11-13 00:12:12
Endometriosis, which affects approximately one in 10 women worldwide, has origins that are still poorly understood. It is characterized by the migration and development of tissues of the uterine lining outside the uterus, in the endometrium, but also in other parts of the pelvic area (ovaries, tubes, bladders, peritoneum, etc.). At the moment, there is no actual treatment for the disease. Taking hormones to stop the menstrual cycle is one option. In the most advanced cases, surgery can be offered but it remains complex. People with endometriosis are more likely to suffer from infertility and develop ovarian cancers.
The current state of research points towards a multifactorial disease, with hormonal, environmental and genetic factors (the risk of developing endometriosis is multiplied by five in women who have a sister or mother affected by this disease ). But the microbiota might well also be involved, according to recent work published in the journal Science by a Japanese team.
Fusobacterium, en cause dans l’inflammation?
A team from Nagoya University collected endometrial tissue from 28 people, half of whom had endometriosis. After genetic analysis, the team noted abnormalities in fibroblasts, connective tissue cells. Among the 13 genes overexpressed in fibroblasts is the TAGLN gene. The latter causes the production of a protein that causes cells to proliferate and migrate into tissues, which might explain why endometrial cells grow outside the uterus in endometriosis. However, TAGLN activity is also boosted by inflammation. The team therefore began looking for a bacteria that might cause this inflammation.
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By analyzing the bacteria present in 155 participants, the work showed that 64% of them who had endometriosis were also carriers of Fusobacterium, a bacteria which is part of the oral flora, in the gastrointestinal tract and in the female genital tract. Among those who did not suffer from it, only 7% also carried this bacteria. Results which suggest that Fusobacterium would be much more present in people with endometriosis.
An ongoing human trial
To understand whether Fusobacterium might directly impact the development of endometriosis, the team transplanted endometrial tissue from one group of mice to another. Within a few weeks, lesions typical of endometriosis formed in the mice that received the transplant. With this model, the researchers were able to see that the lesions were larger and more frequent in the mice in which Fusobacterium had been inoculated than in the others. Finally, the rodents received an antibiotic treatment, metronidazole or chloramphenicol, vaginally, which slowed the development of the disease and reduced the size and number of lesions already present.
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The study still presents some limitations. The bacteria would, for example, deserve to be observed within a more ethnically and gender diverse population, notes the journal Nature. Furthermore, research on humans is all the more necessary as mice are a limited model in this type of research: in fact, these rodents do not menstruate spontaneously and have no lesions of the endometrium. The Japanese study focuses on endometriosis lesions on the ovaries, while in humans it can occur in many places such as the colon and bladder. To go further, Nagoya University has already launched a new study: a clinical trial is currently underway to see if antibiotics also help relieve symptoms in humans.
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