PTH-178 In vitroandex vivomodels of topical alginate protection of human oesophageal epithelium in gastro-oesophageal reflux disease

Abstract

Introduction Up to 40% of patients with gastro-oesophageal reflux disease remain symptomatic despite PPI therapy. In addition to acid the refluxate contains pepsin and bile acids, which may be important in symptom perception. A topical therapy could protect against all components of the refluxate. A reliable model for testing could be used to screen compounds for clinical evaluation. We aimed to evaluate and compare the topical protective effect of an alginate solution in a cell culture and human biopsy model. Method Primary human oesophageal epithelial cells were established into multilayer stratified squamous epithelia using an air-liquid interface technique. After placing in Ussing chambers the apical surface was “protected” with 200 µl of either alginate, viscous control, or was unprotected. After 15 min washing in neutral solution the tissue was exposed to pH 3 + bile acid solution for 30 min and TER change was calculated. Distal human oesophageal biopsies were taken, placed in Ussing chambers and “protected” as above. After 15 min or 60 min washing in neutral solution, change in TER on 30 min exposure to pH 1 + bile acid + pepsin solution was measured. Thickness of a fluorescent-labelled alginate coating on the biopsy luminal surface was measured after 15 min (5 biopsies) and 60 min (5 biopsies) washing in pH 7.4 solution. Results Acid-induced change in TER was significantly less in alginate-protected epithelium than in epithelium protected with viscous control or unprotected tissue. This was seen in both the cell culture (–1.2 ± 5.1%, n = 5 vs. –38.4 ± 6.2%, n = 4 vs. –41.9 ± 8.1%, n = 3) and human biopsy models (−2.7 ± 1.8% vs. −15.26 ± 3.7% vs. −21.1 ± 4.4%, all n = 12) after 15 min washing. Statistically significant protection was still seen after 60 min washing (–8.3 ± 2.2% vs. –25.1 ± 4.5% vs. –26.4 ± 5.3%, n = 12). After 15 min washing the mean alginate layer thickness was 5.7 ± 0.3 µm, and was 4.3 ± 0.3 µm after 60 min washing. Conclusion Alginate topical protection of human oesophageal epithelium against acid-injury is demonstrated in both cell culture and human biopsy models. Epithelial adherence persists for up to 60 min. Topical alginate mucosal protection may be promising as an add-on/alternative therapy for gastro-oesophageal reflux disease. Since the cell culture model was able to reproduce ex vivobiopsy results, it could be an effective tool to screen candidate products prior to clinical evaluation. Disclosure of interest F. Batista-Lima: None Declared, C. Lee: None Declared, D. Sifrim Grant/ Research Support from: Research grant from Reckitt-Benckiser, P. Woodland: None Declared.