Microbiome profiles across the vagina, endometrium and endometrial polyps

Endometrial polyps (EPs) have been associated with alterations in the vaginal and endometrial microbiome, but existing evidence is inconsistent and limited by study design. This study aimed to characterize microbiome profiles across the vagina, endometrium, and EP tissue, and to assess whether EPs are associated with microbiome alterations. This study included 50 women: 20 diagnosed with EPs, 10 without EPs but diagnosed with other gynecological conditions (NEP), and 20 fertile controls. Microbial DNA from vaginal swabs, endometrial biopsies, and EP tissue was analyzed using 16S rRNA gene sequencing. Microbiome composition, diversity, and within-subject similarity across anatomical sites were assessed using established bioinformatic and statistical approaches. Microbial DNA was detected in 112 of 120 samples (93%) across vaginal, endometrial, and EP specimens. Bacterial DNA was not detectable in six endometrial samples and in two EP sample. Sequencing yield was markedly higher in vaginal samples than in endometrial and EP tissues. Microbial DNA profiles were predominantly Lactobacillus -dominated, and no consistent EP-associated differences in community composition were detected within vaginal or endometrial samples. The prevalence of vaginal dysbiosis did not differ significantly between women with EPs and either the control or NEP group ( p > 0.05). Beta diversity did not differ between the groups, indicating that EP status was not associated with distinct community-level shifts. Within-individual paired analyses demonstrated moderate to strong concordance between vaginal and endometrial microbial DNA profiles. In women with EPs, microbial DNA profiles in polyp and adjacent endometrial samples were more similar to each other than to vaginal profiles. This similarity may reflect their shared tissue origin and local microenvironment, but the present study cannot distinguish biological similarity from effects related to low biomass or sampling. EPs were not associated with distinct alterations in the vaginal or endometrial microbiome. The similarity between vaginal and uterine microbial DNA profiles is consistent with biological continuity, transient microbial DNA, or sampling-related carryover; these possibilities cannot be distinguished by the present study design. These findings do not support an association between vaginal dysbiosis and the presence of EPs.