Quantitative histological methods to define mucin alterations

Mucins, the fundamental structural components of mucus, constitute a diverse family of complex glycoproteins. They are classified into two main categories: secreted mucins and surface-associated mucins, both of which serve critical roles in protecting and lubricating epithelial surfaces. The extensive glycosylation of mucins is pivotal to their diverse functions, influencing hydration, lubrication, microbial interactions and structural integrity. Glycans on mucin facilitate water retention and lubrication by binding and trapping water molecules. They also act as decoys, preventing microbial adhesion and mediating interactions with commensal and pathogenic bacteria, as well as attenuating microbial virulence factors. Furthermore, glycans contribute to the physical structure of mucus, supporting its barrier functions. Dysregulation of mucin glycosylation has been implicated in various pathologies, including cancer, Inflammatory bowel disease (IBD), and cystic fibrosis. Notably, specific patterns of mucin glycosylation have been used as biomarkers, for example in IBD, underscoring the importance of distinguishing between glycosylated vs non-glycosylated mucins.