Bacterial microbiome analysis of vaginal, cervical, and endometrial samples in patients with adenomyosis during the window of implantation

Adenomyosis poorly responds to treatment and assisted reproductive technologies. Here, we report a comprehensive 16S rRNA-based analysis of vaginal, cervical, and endometrial samples, obtained minimally invasively (transcervically) in a cohort of Caucasian women during the receptive phase of endometrium. Results revealed the least invasive option, vaginal microbiome sampling, reliably predicts the microbiome compositions of cervix and endometrium. We showed substantial variation in microbial composition of adenomyosis patients. <i>L. iners</i>, a species with specific functional traits, was consistently associated with adenomyosis presence and related symptoms. This finding suggests microbiome remodeling as a viable novel therapeutic option for adenomyosis. Furthermore, our findings indicate that the pathogenic role of <i>G. vaginalis</i> may be context-dependent. Ongoing genomic and ecological profiling is essential to clarify <i>Gardnerella's</i> dual commensal-pathogenic nature. Previous adenomyosis studies have mostly focused on the vaginal microbiome, whereas the endometrial microbiome has rarely been studied and never in the time of window of implantation.