COCULTURE OF 2 MDCK STRAINS WITH DISTINCT JUNCTIONAL PROTEIN EXPRESSION - A MODEL FOR INTERCELLULAR JUNCTION REARRANGEMENT AND CELL SORTING

Distinct epithelial MDCK cell strains displaying extremes in transepit helial electrical resistance (paracellular permeability) have been est ablished in co-culture and the subsequent cellular behaviour and forma tion of junctional complexes investigated, After high-density seeding, MDCK strain I and II cells in co-culture are initially randomly distr ibuted but subsequently sort themselves out in a time-dependent manner to form separate homotypic aggregates. The final pattern of cell arra ngement of homotypic aggregates depends on the relative seeding propor tion of each cell type. Immunostaining of established marker proteins for junctional complexes has revealed that MDCK I and II cells differ in the degree of expression of the zonula-adherens-associated protein, E-cadherin. their cytoskeletal architecture and the junctional distri bution of a desmosomal protein, and by showing subtle differences in t ight junction staining for the zona-occludens-associated proteins, ZO- 1 and occludin, The distinct pattern of junctional protein expression is maintained when the two MDCK strains are co-cultured; however, morp hologically atypical intercellular junctions between heterotypic cells at the boundary of homotypic cell aggregates have been observed, It h as been suggested that cell sorting, a phenomenon yet to be completely understood, is involved in important morphogenetic processes. We prop ose that co-culture of strains of the well-characterised MDCK cell lin e may be a novel but well-defined cell system for studying epithelial cell rearrangement and sorting in intact epithelial sheets.