Epithelial geometry and its physiological properties:revision of the osmotic flow water transport model with LI-cadherin assisting role.

Description

We introduce a mathematical model of an absorbing leaky epithelium to reconsider the problem established by Diamond and Bossert in 1967 of whether “[…] some distinctive physiological properties of epithelia might arise as geometrical consequences of epithelial ultrastructure”. We derive analytical expressions for a homogeneous concentration and for the spatial scale necessary for homogeneity to develop along the cleft. We found that a columnar epithelium is generally more stable to lumen hyperosmolarity than a cuboidal one. Nevertheless, the cuboidal epithelium can perform “uphill” water transport both by narrowing of the intercellular cleft (IC) width and by varying the expression level of aquaporins and ion channels in an enterocyte. Narrowing of the cleft increases ion concentration dramatically and can therefore prevent any outflow through tight junctions (TJs) and the lateral membrane as long as a certain extremely high threshold lumen osmolarity is not reached. Our model predicts that the system is to some extent self-regulating and thereby prevents fluxes into the lumen. Several theoretical scenarios of water fluxes through TJs, lateral membrane and opening of the cleft suggest an ability of enterocytes to adjust their parameters to changing lumen osmolarity. Analytical approximations for IC ion concentrations in columnar and cuboidal epithelia are derived. Recent experimental evidence has shown that liver-intestine (LI) cadherin can control the up/down flux in intestines via regulation of the cleft width. This finding is in full agreement with our theoretical model. We suggest that LIcadherin may increase water transport through epithelia via sequential narrowing of the cleft, starting from the highest concentration area at the beginning of the cleft and triggering a propagating squeezing motion.

Period	25 Mar 2017
Event title	unbekannt/unknown
Event type	Conference
Location	FranceShow on map