Healthy PDLF Cells Influence Diseased PDLF Inflammatory Response

Objective: Periodontal disease threatens the oral health of nearly 75% of the US population (14% severely), and may contribute to cardiovascular and other systemic diseases. We have reported that periodontal ligament fibroblasts isolated from healthy and diseased sites demonstrate a significantly different gene expression and protein profiles.   The goal of this study was to determine if secreted products from diseased or healthy tissue can influence each other in a co-culture environment.

Method: Periodontal ligament fibroblasts (PDLFs) were isolated from patients diagnosed with chronic periodontitis including advanced periodontal lesions.  Periodontal ligament fibroblasts established in culture from healthy tissues harvested from individual patients served as the control group.  The cells were grown to near confluency in 24 well plates and transwells.  Healthy PDLFs in transwells were transferred to 24 well plates containing diseased cells; diseased PDLFs in transwells were transferred to 24 well plates containing healthy PDLFs.  Half of the groups received LPS (1mg/mL, E.coli) for 6 h prior to harvest.  At 24 h, culture media was harvested and cells were fixed for measurement of IL-6.  Intracellular IL-6 was measured by in-cell western techniques using the Odyssey® imaging system.  Secreted IL-6 was measured via ELISA. Changes in protein levels were analyzed using ANOVA and Tukey post-hoc test (a=0.05). 

Result: As expected, intracellular levels of IL-6 increased significantly in all groups in response to LPS.  Exposure to healthy or diseased cells in co-culture made no significant difference in the intracellular  response.  However, when diseased PDLFs were cocultured with transwells containing healthy PDLFs, the LPS-induced secretion of IL-6 was significantly lower (p<0.05).

Conclusion: These data suggest that healthy PDLFs secrete products that suppress the response of diseased PDLFs to an inflammatory challenge.  Further investigation of the secreted products of healthy PDLFs is needed to identify these anti-inflammatory products.