Introduction
Polycystic ovary syndrome (PCOS) is a leading endocrine cause of female infertility characterized by oligo-amenorrhea or ovulatory dysfunction (OA), hyperandrogenism (HA), and polycystic ovarian morphology (PCOM)1. The global prevalence of PCOS is estimated to be 5-15% based on the diagnostic criteria applied2. PCOS can also lead to metabolic manifestations such as obesity, hyperinsulinemia/insulin resistance (IR), and an increase in the risk of developing type 2 diabetes (T2D)3, 4 and coronary heart disease5. One of the most widely used diagnostic criteria for PCOS is the Rotterdam criteria6, which requires the presence of at least two of above three cardinal traits. This results in four different phenotypes: phenotype A: HA + OA + PCOM; phenotype B: HA + OA; phenotype C: HA + PCOM; phenotype D: OA+ PCOM, which diversifies the presentation of PCOS.
Despite its prominent impact on female reproductive and metabolic health, the etiology of PCOS remains unclear. Although attention has been focused on key genetic factors during the past decade2, recent studies on PCOS intestinal microbiota have suggested a novel environmental-related disease mechanism7, 8. Apart from the gut, another important microbial niche in women is the vagina. Dysbiosis of the microbiome in the lower female reproductive tract has been implicated in a variety of diseases, such as preterm birth9, sexually transmitted infections 10, 11, pelvic inflammatory disease12, and gynecological cancers13, 14. Recent studies have also begun to explore the role of the vaginal microbiome (VMB) in PCOS. However, due to a limited sample size and complex confounding factors of the selected cohort, studies that used 16S ribosomal RNA (16s rRNA) gene sequencing techniques to compare women diagnosed with PCOS and healthy controls have led to different results regarding the diversity and composition of the vaginal microbiota15, 16. Furthermore, endocrine and metabolic characteristics vary among different PCOS subsets17, but discrepancies in vaginal microbial PCOS subtypes have rarely been clarified.
In this study, we analyzed the vaginal microbial characteristics of 1,446 subjects using high-throughput sequencing to determine the microbial characteristics, bacterial community interactions, as well as functional prediction of the vaginal microbiota and different subsets related to PCOS.