O36 Investigating clonal expansions in the normal stomach and the 3D architecture of oxyntic gastric glands

IntroductionGastric epithelium is exposed to constant environmental insults, with H. Pylori the primary carcinogen of non-cardia intestinal type gastric cancer. How mutations clonally expand in normal and inflamed epithelium prior to the development of cancer is relatively unknown. In this study we use neutral clonal markers to characterise clonal expansions in normal epithelium. We investigate the impact previous H. Pylori exposure has on clonal expansions in gastric epithelium. We then develop a new method of 3D reconstruction to visualise the structure of individual gastric glands.MethodsWe collected tissue from patients undergoing sleeve gastrectomy for weight loss (n=15). Gastric corpus tissue was harvested and embedded en face, then labelled using enzyme- & immuno-histochemistry for neutral clonal markers (Cytochrome C Oxidase (CCO) & MTCO1) to identify clonal patches. Quantification was performed using digital pathology software (Qupath), to analyse clonal patch sizes. Serial tissue sectioning was performed to trace CCO/MTCO1 mutated glands of interest for 3D reconstruction. Briefly, registration using a rigid and non-rigid B-spline transformation was applied, followed by a denoising step. Segmentation of glands was done by modelling using a Gaussian distribution, extraction of closing maps and applying an ellipsoidal fitting model. Cubic interpolation was then used for 3D modelling.ResultsPatient ages were 31–65 years. Histologically, 8 were normal, 2 had active H. Pylori infection, 4 had evidence of previous infection with chronic inflammation, atrophy and intestinal metaplasia. CCO and MTCO1 clones were seen as wholly mutated glands and partially mutated glands. Overall clonal expansions were small, patch size analysis showed clones were most frequently singular glands, and rarely small patches (mean patch size = 1.65 glands). H.Pylori infection or chronic inflammation increased the frequency and size of patches compared to non-exposed tissue. 3D reconstruction (figure 1) allowed visualisation of the structure of the oxyntic gland, and tracing of CCO lineages allowed visualisation the functional architecture.Abstract O36 Figure 13D reconstruction of gastric gland with CCO positive (brown) & negative regions (blue) visibleConclusionsThis data describes the pattern of clonal expansions occurring in normal gastric epithelium. H.Pylori exposure and chronic inflammation lead to an increase of up to ten fold in frequency and size of clonal expansions.