Structure and dynamics of epithelial cells : Studied with confocal microscopy and flourescence recovery after photobleaching

Abstract: Epithelial cells of the human body form a physical barrier to harmful agents and potential invading microorganisms. In the small intestine they must also produce enzymes for digestion of food and be able to absorb nutrients.The aim of this work was to study properties of epithelial cells in model systems using cell lines and toad bladder cells, and to study the effect of gluten intolerance (celiac disease, CD), viz. a pathological condition, on human small-intestine epithelial cells, enterocytes. Fluores-cence microscopy techniques, and primarily confocallaser scanning microscopy (CLSM), have beeen used as the major methods in the investigation. Part of the work has also been to develop, and apply, tools for measurements in confocal rnicroscopy images to obtain semi-quantitative information on structures.Fluorescence recovery after photobleaching (FRAP) was used to study the effect of maturation of small intestine-like epithelial cells. Lateral diffusion of membrane components was measured to reveal alterations in membrane fluidity induced by differentiation. No general effects on the lateral mobility of membrane components was observed, rather distinct effects were noticed on protein diffusion.Vasopressin induces the fusion of vesicles containing water channels with the apical membrane of toad bladder epithelial cells. This fusion is known to result in depolymerization of fllamentous actin (F-actin) of the cell. CLSM was used to assess where in the cell the depolymerization occurs. It was demonstrated that the depolymerization is not evenly distributed, but confined only to the apical region of the cells.In children suffering from celiac disease the mucosa of the small intestine is severely damaged. The damage at the enterocyte level is, however, less investigated. In the present work, CLSM was applied to compare the distributions ofF-actin and of glycoconjugates in enterocytes  from children with CD to enterocytes from children not suffering from the  disease. The results show that in children with active CD the distribution of both structures was altered, but also that compliance to a gluten-free diet results in the return to normal-looking enterocytes.