Are comorbidities associated with the cytokine/chemokine profile of persistent apical periodontitis?

Mimicking and in vitro validating chronic inflammation in human gingival fibroblasts

OBJECTIVE

The aim of this study was to identify and validate in vitro conditions that may mimic the translational, cytokine and chemokine profiles observed in human inflamed gingiva in vivo.

DESIGN

Primary human gingiva fibroblast cells (HFIB-G) were cultured under serum starvation conditions (0 - 10 %), supplemented with increasing lipopolysaccharide (LPS) concentrations (0.1, 1, or 10 µg/ml) from two bacterial strains E. coli and P. gingivalis and 0.1, 1, or 10 ng/ml recombinant interleukin 1β (IL-1β), alone or in combinations. The levels of cytokines/chemokines were measured in the cell culture medium by Luminex, and gene expression was quantified by Affymetrix microarrays at 24, 48 and 72 h.

RESULTS

Inflammation markers were not elevated after stimulation with P. gingivalis LPS, while E. coli LPS and IL-1β individually increased the secretion of interleukin 6 (IL-6) and monocyte chemoattractant protein-1 (MCP-1) to the cell culture medium. IL-1β administration also increased the secretion of several factors, including tumor necrosis factor (TNFα). However, the combination of 1 µg/ml E. coli LPS, 1 ng/ml IL-1β and serum starvation led to increased secretion of IL-6, TNFα, in addition to other factors found in inflamed tissue. Gene expression analyses revealed that this combination not only enhanced the expression interleukins/chemokines genes but also T helper cell signaling and matrix metalloproteinases.

CONCLUSION

Serum reduction in cell culture medium together with the administration of E. coli LPS and IL-1β resulted in gene expression and secreted cytokine/chemokine profiles similar to that found in vivo during chronic inflammation.