title: LLC-PK1 cysts: a model for the study of epithelial polarity.
abstract: In the present work, we have taken advantage of the properties of two recently isolated clonal subpopulations of the pig kidney-derived LLC-PK1 cell line to study aspects of the establishment of epithelial polarity. When grown in suspension, LLC-PK1/D + Sc cells reaggregated within a few hours and, during the following days of culture, formed free-floating, hollow spheres or cysts, lined by a monolayer of polarized cells. In contrast, LLC-PK1/D- cells were unable to develop such polarized structures even upon prolonged culture in suspension. The polarity of the LLC-PK1/D + Sc cells lining the cysts was inverted compared to that in intact renal tubules, the microvilli-rich "apical" pole being oriented toward the external medium. However, upon embedding these preformed cysts in collagen gels, a reversal of polarity was observed within hours, the microvilli-rich pole now facing the cyst cavity. Thus, in the same clonally derived cell population, cell-to-cell contact and interaction with the extracellular matrix differentially affect the orientation of cellular polarity. The LLC-PK1/D + Sc cysts provide a suitable in vitro model system for further study of the sequential events by which extracellular matrix components induce an appropriately oriented polarization. In addition, the comparison between LLC-PK1/D + Sc and D- cells, which differ in their ability to polarize in response to cell-to-cell contact, should help define some of the cellular determinants involved in epithelial organization.
mesh_terms: D000818:Animals; D002448:Cell Adhesion; D002449:Cell Aggregation; D002450:Cell Communication; D002460:Cell Line; D002999:Clone Cells / Q000502:physiology; D003094:Collagen; D003560:Cysts / Q000503:physiopathology*; D004848:Epithelium / Q000502:physiology / Q000648:ultrastructure; D005782:Gels; D007668:Kidney / Q000502:physiology* / Q000648:ultrastructure; D008871:Microvilli / Q000502:physiology; D008954:Models, Biological; D013552:Swine
chemical_list: D005782:Gels; D003094:Collagen