Pseudomonas aeruginosa entry into Caco-2 cells is enhanced in repairing wounded monolayers

Human respiratory cells participating in the repair of epithelial wounds have been shown to be highly susceptible to Pseudomonas aeruginosa adherence. To ascertain whether such susceptibility is a common feature of different repairing epithelial cells, Caco-2 cell monolayers were chemically injured, reincubated for 48 h to partially repair and exposed to bacteria. Cells edging the wounds that spread and migrate to re-establish cell confluence were called 'repairing cells' while cells far from the wounds were called 'non-repairing cells'. By light microscopy, bacteria were seen to adhere to and to enter into both repairing and non-repairing cells. The percentage of intracellular bacteria in repairing cells was significantly higher than in non-repairing cells. The higher susceptibility of repairing monolayers to bacterial entry was confirmed by the gentamicin exclusion assay. P. aeruginosa entry into Caco-2 cells was greatly enhanced in non-injured confluent monolayers treated with EDTA to disrupt intercellular junctions. As tight junction disfunctions have been described during the wound repair process, we speculate that exposure of basolateral receptors to bacterial ligands may account for the enhancement of P. aeruginosa internalization by repairing monolayers.