Possible models describing enterocyte replacement in mouse Peyer's patch follicle-associated epithelial tissue.

Epithelial cells emerging from intestinal crypts surrounding Peyer's patch lymphoid follicles can be shown in chimaeric mice to adopt a wedge-like formation during migration to a central zone of cell extrusion (Schmidt et al. 1985). Similar tissue taken from normal mice has been used as a model in the present work to investigate how such a pattern of convergent migration might take place. Tissue treated cytochemically to reveal differences in surface alkaline phosphatase activity enabled a number of cell surface area measurements to be carried out by image analysis. The position where these measurements had been taken was then related to the geometrical centre of the tissue. Epithelial cell surface area halved during migration from edge to centre of these disc-like structures. An equation used to describe the positional dependence of this change had the form rho(r) = 6.86r(-0.24), where rho is cell density and r is cell distance from the centre measured in micrometers. Further calculation showed this decrease to be insufficient to explain all features associated with convergent migration. Differential changes occurring in the rate of cell migration and premature cell loss were also considered as possible factors affecting migration patterns. Mathematical modelling of these variables produced a migration pattern consistent with previous experimental findings. This model assumes that half the cell population is lost during migration and that cell migration rate near the centre is four times greater than at the edge. It should be possible to test this latter prediction in future experiments.