Dysbiosis in pregnant mice induced by transfer of human vaginal microbiota followed by reversal of pathological changes in the uterus and placenta via progesterone treatment.

OBJECTIVE: The vaginal microbiota dysbiosis induces inflammation in the uterus that triggers tissue damage and is associated with preterm birth. Progesterone is used to prevent labor in pregnant women at risk of preterm birth. However, the mechanism of action of progesterone still needs to be clarified. We aimed to show the immunomodulatory effect of progesterone on the inflammation of uterine tissue triggered by dysbiotic vaginal microbiota in a pregnant mouse model. METHODS: Healthy (n = 6) and dysbiotic (n = 7) vaginal microbiota samples isolated from pregnant women were transferred to control (n = 10) and dysbiotic (n = 14) pregnant mouse groups. The dysbiotic microbiota transferred group was treated with 1 mg progesterone (n = 7). Flow cytometry and immunohistochemistry analyses were used to evaluate inflammatory processes. Vaginal microbiota samples were analyzed by 16 S rRNA sequencing. RESULTS: Vaginal exposure to dysbiotic microbiota resulted in macrophage accumulation in the uterus and cellular damage in the placenta. Even though TNF and IL-6 elevations were not significant after dysbiotic microbiota transplantation, progesterone treatment decreased TNF and IL-6 expressions from 49.085 to 31.274% (p = 0.0313) and 29.279-21.216% (p = 0.0167), respectively. Besides, the macrophage density in the uterus was reduced, and less cellular damage in the placenta was observed. CONCLUSION: Analyzing the vaginal microbiota before or during pregnancy may support the decision for initiation of progesterone therapy. Our results also guide the development of new strategies for preventing preterm birth.

The vaginal microbiome composition during pregnancy in a region compromising different ethnic origins.

BACKGROUND: The vaginal microbiota plays a significant role in pregnancy outcomes and newborn health. Indeed, the composition and diversity of the vaginal microbiota can vary among different ethnic groups. Our study aimed to investigate the composition of the vaginal microbiome throughout the three trimesters of pregnancy and to identify any potential variations or patterns in the Turkish population compromising mixed ethnicities. METHOD: We conducted a longitudinal study to characterize the vaginal microbiota of pregnant women. The study included a total of 25 participants, and the samples were collected at each trimester: 11-13 weeks, 20-24 weeks and 28-34 weeks gestation. RESULTS: Lactobacillus species were consistently found to be dominant in the vaginal microbiota throughout all trimesters of pregnancy. Among Lactobacillus species, L. crispatus had the highest abundance in all trimesters (40.6%, 40.8% and 44.4%, respectively). L. iners was the second most prevalent species (28.5%, 31% and 25.04, respectively). Our findings reveal that the dominant composition of the vaginal microbiota aligns with the CST-type I, commonly observed in the European population. CONCLUSIONS: This suggests that there are shared mechanisms influencing the microbial communities in the vagina, which are likely influenced by factors such as genetics, lifestyle, and cultural behaviors rather than ethnicity alone. The complex interplay of these factors contributes to the establishment and maintenance of the vaginal microbiota during pregnancy. Understanding the underlying mechanisms and their impact on vaginal health across diverse populations is essential for improving pregnancy outcomes. The study was approved by the Koc University Ethical Committee (no:2019.093.IRB2.030) and registered at the clinical trials.

Alterations in vaginal microbiota among pregnant women with COVID-19.

The maintenance of vaginal microbiota is an important factor to achieve optimum pregnancy outcomes. The study aims to describe the alterations in the composition of vaginal microbiota in pregnant women with coronavirus disease 2019 (COVID-19). This was a prospective case-control study. Vaginal swabs were collected from uninfected pregnant women (n = 28) and pregnant women with COVID-19 (n = 19) during the active phase of infection and within a month after recovering from infection. The vaginal microbiota on the swabs was examined by 16S rRNA gene sequencing. Shannon index indicates that alpha diversity is significantly higher in women with COVID-19 (p = 0.012). There was a significant decrease in Firmicutes (p = 0.014) with an increase in Bacteroidota (p = 0.018) phyla and a decrease in Lactobacillus (p = 0.007) genus in women with COVID-19 than those of uninfected pregnant women. The relative abundance of L. crispatus, L. iners, L. gasseri, and L. jensenii were lower in the COVID-19 group than in uninfected pregnant women. In subgroup analysis, the amount of Ureaplasma spp. was higher in women with moderate/severe than those of asymptomatic/mild disease (p = 0.036). The study revealed that vaginal dysbiosis with low abundance of Lactobacillus species occurred in pregnant women infected with severe acute respiratory syndrome coronavirus-2. These findings may lead to new studies to elucidate the risk of pregnancy adverse outcomes related to COVID-19.