Resident microbes shape the vaginal epithelial glycan landscape

Area of Science:

• Microbiology
• Glycobiology
• Epithelial Biology

Background:

• The vaginal epithelial surface is covered by a protective glycocalyx, a layer of carbohydrates (glycans).
• Bacterial vaginosis (BV) is linked to negative health outcomes and involves direct contact between vaginal bacteria and the epithelium.
• The specific glycan composition of the vaginal epithelium and its alteration in BV are not well understood.

Purpose of the Study:

• To characterize the normal vaginal epithelial glycan landscape.
• To investigate the impact of resident microbes on the vaginal glycocalyx, particularly in the context of BV.
• To explore the role of bacterial glycosyl hydrolases in altering the vaginal glycan profile.

Main Methods:

• Electron microscopy to visualize glycocalyx structure.
• Biochemical and mass spectrometry to analyze glycan composition.
• Treatment of primary vaginal epithelial cells and cultured VK2 cells with recombinant *Gardnerella* sialidases.

Main Results:

• BV samples showed a visibly diminished glycocalyx compared to controls.
• BV epithelial cells were depleted of sialylated N- and O-glycans, exposing galactose residues.
• *Gardnerella* sialidase treatment induced BV-like glycan changes and altered gene expression related to cell death, differentiation, and inflammation.

Conclusions:

• The vaginal epithelial glycan landscape is significantly altered in BV.
• Bacterial sialidases may contribute to the observed glycan changes in BV.
• Altered epithelial glycans and bacterial enzymes may influence epithelial cell turnover and host-microbiome interactions.