Abstract

FR.02.01

Sweet talk at the ocular surface

Berry M.¹, Nelson S.², Dave R.¹, Baos S.¹, McMaster T.^1
1University of Bristol, Mucin Research Group, Bristol Eye Hospital, Bristol, UK; ²University of the West of England, Department of Applied Sciences, Bristol, UK

Objective: The ocular surface is rich in glycosylated molecules that interact to form macromolecular assemblies and signal to the bacterial flora and to effectors of the systemic immune system. The collection of oligosaccharides decorating mucins is thought to be key to these varied interactions. We have measured biophysical properties of macromolecular complexes of ocular mucins and assessed bacteria-mucin interactions.
Methods: Mucins were extracted from normal ocular surfaces and from human corneal and conjunctival epithelial cells in vitro. Macromolecular assemblies were formed on either the AFM tip or on a substrate. Elastic moduli and adherence forces were measured in a physiological liquid. Adherence of bacteria to epithelial cells and their invasiveness were assessed in vitro. Effects of stratification, mucin production, addition of exogenous mucin and sialic-acid binding lectins were also quantified in this model, using luminescent bacteria.
Results: Mucins purified from cultured ocular epithelia produced membrane-spanning and secreted mucin species as present at the ocular surface in vivo. Glycosylation was sparser as assessed by buoyant density, while polymer lengths were polydisperse. Ocular mucin aggregates exhibited lubrication characteristics as well as shear thinning. Elastic moduli were of the order of tens of kPa. Lectins and mucins affected bacterial adhesion and growth, as well as invasiveness into cultured epithelia. The magnitude of these effects depended on the epithelial cell line used. Incubation with lectins was disadhesive for cultured monolayers.
Conclusions: Interactions between mucins and bacteria rely on sugar moieties, but are not abrogated by sparse glycosylation.

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