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From the Department of Anatomy and Cell Biology, Wayne State University School of Medicine, Detroit, Michigan.
PURPOSE. To measure the effect of extracellular matrix substrate, pH, and O2 on Pseudomonas aeruginosa binding.
METHODS. Extracellular matrix substrates were prepared from human corneal epithelial cells cultured in 2% or 20% O2. P. aeruginosa strains ATCC 19660 or PAO1 (suspended in pH 7.0 or 7.5 buffer) were cultured on extracellular matrix substrates in 2% or 20% O2. The mean number of adherent bacteria per counted per field ± SEM (n = 15) was determined for combinations of bacteria, extracellular matrix substrate, pH, and O2. Binding in the presence of antibodies directed against laminin-5 was also measured.
RESULTS. Extracellular matrix substrates produced by cells cultured in 20% O2, combined with an environment of pH 7.0, provided the least favorable conditions for binding of strain 19660. In contrast, extracellular matrix substrates produced by cells cultured in 2% O2, combined with an environment of pH 7.0, provided the most favorable conditions for binding of strain 19660. Binding of PAO1, however, as a function of extracellular matrix substrate and pH, did not similarly compare with binding of strain 19660. Antibodies against laminin-5 chains served to increase the number of strain 19660 bacteria bound to extracellular matrix substrates compared with the control.
CONCLUSIONS. The extracellular matrix secreted by hypoxic corneal epithelial cells is a substrate for binding of P. aeruginosa. Results in previous studies have shown that hypoxic extracellular matrix contains less laminin-5 protein than normoxic matrix. The antibody studies in this report suggest that the decrease in laminin-5 content in hypoxic matrix, relative to matrix secreted by normoxic corneal epithelium, may be responsible for increased bacterial adhesion.
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