(230an) Viscoelasticity of Mucus Layers Secreted By Intestinal Epithelial Cells

A small-gap rheometry technique is developed to evaluate the viscoelasticity of the adherent mucus secreted by living cell cultures of human intestinal epithelial cells as a function of position above the substrate surface. Non-mucus producing (HT29) and mucus producing (HT29-MTX) intestinal epithelial cells are grown to confluence over 2.5 cm glass cover slips mounted in polystyrene wells, which are then mounted directly to the lower platen of a parallel plate rheometer (Rheometrics ARES), using cyanoacrylate adhesive. A reference point for setting the gap of the rheometer is established by â??zeroingâ? the instrument against an ultra-high precision 3mm stainless steel ball placed at the center of the cover slip. The linear viscoelastic responses Gâ??(Ï?) and Gâ?(Ï?) are then measured at frequencies Ï? ranging from 0.16-16 Hz and 0.5% strain, for gaps varying from 0.050-0.150mm above the cover slip surface. The results¹ show that the adherent mucus layer over the mucus-producing (H29-MTX) cells is approximately 0.10 mm thick, and that the viscoelastic response is dominated by the storage modulus Gâ??(Ï?), which varies strongly with position within the mucus layer. At a fixed frequency of Ï?=1.6 Hz, Gâ?? varies from approximately 180 Pa to 37000Pa as the gap (height above the cover slip) decreases from 0.100mm to 0.050mm. As expected, the non-mucus producing (HT29) cell culture does not exhibit a significant viscoelastic response at any of the gap positions tested. An addition set of experiments performed with HT29-MTX mucus producing cells exposed to estrogen shows that estrogen-treated cells produce mucus layers with significantly higher viscoelasticity than those not treated with estrogen.

1. Diebel, M. E, Diebel, L. N., Liberati, D. M. and Manke, C. W., â??Estrogen modulates intestinal mucus physiochemical properties and protects against oxidant injuryâ?, Journal of Trauma and Acute Care Surgery, 78, 94-99 (2015).