Exploratory analyses of cervicovaginal mucus <i>O-</i> glycan composition and microbiota profiles in unexplained infertility

In addition to the specific causes of infertility, two components of the vaginal ecosystem, the vaginal microbiota and the cervicovaginal mucus (CVM), may be associated to reduced fecundity and the success of infertility treatments. The aim of this study was to explore the composition of the CVM O-glycans and vaginal microbiota in women with unexplained infertility. We collected CVM and vaginal swab samples during medically induced ovulation from 19 women with unexplained infertility. Mucin O-glycosylation profiles were generated through Matrix-Assisted Laser Desorption/Ionization Time-Of-Flight (MALDI-ToF) mass spectrometry and taxonomic profiles of the vaginal microbiota through 16S rRNA gene amplicon sequencing. Altogether 57 O-glycan structures were identified, dominated by core 1 and 2 structures. A significant proportion, nearly 85%, of the glycans were fucosylated and five structures dominated the profiles, accounting for >50% of the glycans observed in most samples. The vaginal microbiota of the patients was dominated by Lactobacillus crispatus (79%), followed by Lactobacillus jensenii (32%) and Lactobacillus iners (21%) and Gardnerella vaginalis (5%, single sample). PERMANOVA analysis indicated significant associations between the glycan structures and dominant taxa (q = 0.0011, R2 = 0.37). This exploratory study provides initial insights into the composition and variation of CVM O-glycans in unexplained fertility and in relation to the vaginal microbiota composition, laying a groundwork for future research.