Study on the correlation among dysbacteriosis, imbalance of cytokine and the formation of intrauterine adhesion

Intrauterine adhesion (IUA) is one of the most important causes of female infertility, while iatrogenic endometrial injury is the main, but not the entire, cause of IUA. The microorganisms of the female reproductive tract play an important role in its health and disease. The imbalance of immune regulation caused by the imbalance of reproductive tract dysbacteriosis may be an important link in the formation mechanism of uterine cavity adhesion.

IUA is characterized by an increased bacterial burden, decreased diversity of bacterial communities in the vagina/cervical canal, and increased immune cytokines of pro-fibrosis, which may predict new and more effective therapeutic schemes for the treatment of IUA.

We prospectively enrolled 30 patients diagnosed with IUA and 30 women with a history of intrauterine surgery, but without IUA, as control subjects. All participants were diagnosed with hysteroscopy while two swabs-one being leucorrhea drawn from the middle of the vagina and the other being cervical mucus drawn from the cervical canal-were taken. The bacterial load and community were identified by 16S rDNA quantitative polymerase chain reaction and pyrosequencing. Immunocytokines in serum were quantitatively detected by human T-helper cytokine kit. The correlation between Th cytokines and microorganisms in IUA and non-IUA groups was analyzed.

Compared with non-IUA participants at the phylum level, patients with IUA had a significantly higher percentage of firmicutes in most samples, while the diversity of bacteria was significantly decreased. Some species that were members of vaginal and cervical canal bacterial phyla, including Euryarchaeota, Acidobacteria, Chlamydiae, Chlorobi, Planctomycetes and TM6 (Dependentiae), almost disappeared. The quantity in serum of IUA patients of classical proinflammatory cytokines IL-6 and TNF-γ, released from immune cells, also known as profibrotic cytokines, were significantly higher than that of the non-IUA women in our study (P<0.05). Conclusions: IUA is characterized by an increased bacterial burden, decreased diversity of bacterial communities in the vagina/cervical canal, and increased immune cytokines of pro-fibrosis, which may predict new and more effective therapeutic schemes for the treatment of IUA.