Objective: The objective of this study was to isolate the subpopulation of epithelial cells associated with P.gingivalis and to determine whether these cells had a different gene expression pattern compared to those not associated with bacteria.
Methods: Fluorescently labelled P.gingivalis were incubated for 90 minutes with the H357 oral keratinocyte cell line at a multiplicity of infection of 100:1. Cells associated with P. gingivalis were separated using flow cytometry cell sorting and the RNA extracted from these and cells not associated with bacteria, reverse transcribed and applied to an Affymetrix U133 plus2 human gene array.
Results: By microarray analysis, 5 genes were over expressed > 3 fold in cells associated with bacteria compared to those that were not. These were endothelin 1, grainyhead-like 3, zinc finger protein 750, keratin associated protein 2-4, vestigial like 3 and small proline-rich protein 3. The serpin peptidase inhibitor 1 gene showed >3 fold lower expression. Over expression of endothelin-1 in cells associated with P. gingivalis has been confirmed using qRTPCR.
Conclusion: The identification of subpopulations of epithelial cells which are preferentially targeted by P.gingivalis is an important finding. Transcriptomic profiling of these cells has revealed that a number of genes are differentially expressed including endothelin-1, a peptide with pleiotropic effects on cell signalling pathways. Further work is required to determine whether these molecules facilitate cell invasion or are a changed in response bacterial to invasion.