TNF-alpha and P. gingivalis Lipopolysaccharides Decrease PDL Fibroblast Periostin Expression

Periostin is a matricellular protein essential for tissue integrity and maturation and is believed to have a key function as a modulator of periodontal ligament (PDL) homeostasis. Objective: To evaluate whether periodontal pathogen-related byproducts (endotoxins/lipopolysaccharides (LPS)) and pro-inflammatory cytokines alter the expression of Periostin in PDL fibroblastic cells. Methods: hPDL cultures (250,000 cells/well) were exposed to pro-inflammatory mediators (i.e., TNF-α), bacterial byproducts (i.e., P. gingivalis LPS), or both in a biomechanically challenged environment (loaded with 14% stretching at 6 cycles/min). Culture conditions were applied for 24h, 4, and 7 days and media supplemented every 24h. POSTN, Twist-1, and ßIg-H3 mRNA expression from cell lysates were analyzed. Periostin and ßIg-H3 proteins were also identified and semi-quantified both in cell lysates and media by Western Blot. In addition, Periostin localization was performed by immunofluorescence. The ANOVA and Fisher’s tests were used to detect any statistical differences among groups (p<0.05). Results: In a mechanically challenged environment (loaded), Periostin protein molecules were more efficiently incorporated into the matrix compared to the unloaded controls, as higher levels of Periostin were present in the conditioned media in the unloaded group. Chronic exposure (4 and 7days) to pro-inflammatory cytokines (e.g., TNF-α) and/or microbial virulence factors (e.g., P. g. lipopolysaccharides, significantly decreased Periostin protein levels in the loaded cultures. Altered expression levels were also observed for ßIg-H3. However, there was greater variability with no evident pattern. Conclusion: Inflammatory mediators (i.e., TNF-α) and bacterial byproducts (i.e., P. gingivalis LPS) appear to decrease Periostin expression in human PDL fibroblasts. These results support a potential mechanism by which Periostin alterations could constitute a contributing factor during periodontal disease progression.