Fate of polarized membrane components and evidence for microvillus disassembly on migrating enterocytes during repair of native intestinal epithelium.

BACKGROUND

Maintenance of enterocyte polarity is crucial to normal intestinal function. Tight junctions and cell-matrix interactions play a role in maintaining polarized cell membrane domains. In many intestinal epithelial wounds, normal cell-cell associations mediated by tight junctions are lost. The goal of this study was to examine the fate of an apically restricted fucosylated glycoconjugate (FGC) and basolaterally restricted Na/K-ATPase in a model of intestinal epithelial repair. Comparisons are made to isolated enterocytes in which cell-matrix interactions are disrupted as well.

EXPERIMENTAL DESIGN

We present a novel physiologically relevant model of intestinal epithelial injury and restitution that was used to examine the fate of two polarized membrane components by fluorescent and ultrastructural techniques. In addition, we used mechanical vibration to isolate enterocytes as individual and short sheets of cells from the intestinal basement membrane and evaluated the fate of these restricted membrane components using immuno- and lectin histochemistry.

RESULTS

Na/K-ATPase maintained its basolateral membrane location in restituting epithelial but relocated to a nonbasolateral position in the majority of isolated enterocytes. The FGC maintained its apical restriction in isolated enterocytes and in epithelial cells migrating across denuded basement membrane. An additional and important observation noted in this study was a drastic alteration in shape of migrating epithelial cells characterized by diminution and loss of microvilli as the cells migrated across the injury.

CONCLUSIONS

We conclude from our results that maintenance of Na/K-ATPase to a basolateral membrane position is influenced by cell-matrix interactions. In contrast, restriction of FGC to the apical membrane of enterocytes is dependent on the presence of microvilli and is not related to either cell-cell or cell-matrix interactions. Additionally, we suggest a new model of intestinal repair in which microvilli are disassembled. We speculate that membrane from disassembled microvilli, as well as lateral cell membrane, are used at the leading edge of the migrating cell.