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Platelet-rich fibrin (PRF), originally used to support soft tissue healing, is also considered a therapeutic option for treating oral lichen planus and leukoplakia. The progression from the two premalignant lesions to the aggressive malignant oral squamous cell carcinoma involves an inflammatory process linked to chemokine expression. Thus, there is a rationale for studying how PRF modulates the expression of chemokines in oral squamous carcinoma cells. To this aim, we expose the oral squamous carcinoma cell line HSC2 to IL1β and TNFα either alone or in the presence of lysates obtained from solid PRF membranes. We report here that in HSC2 cells, PRF lysates significantly reduce the forced transcription of chemokines, e.g., CXCL1, CXCL2, CXCL8, CXCL10, and CCL5. Moreover, PRF lysates attenuate the nuclear translocation of p65 in HSC2 oral epithelial cells when exposed to IL1β and TNFα. PRF lysates further reduce chemokine expression provoked by poly:IC HMW. Even though less pronounced, PRF lysates reduce IL1β- and TNFα-induced chemokine expression in TR146 cells. In primary oral epithelial cells, however, PRF lysates increase the basal expression of CXCL1, CXCL2 and CXCL8. Thus, PRF can exert a biphasic effect on chemokine expression in oral squamous cell carcinoma cell lines and primary oral epithelial cells. These findings suggest that PRF may reduce inflammation in a malignant environment while provoking an immunological response in healthy oral epithelium.

Amelotin (AMTN) is a secretory calcium-binding phosphoprotein controlling the adhesion of epithelial cells to the tooth surface, forming a protective seal against the oral cavity. It can be proposed that signals released upon dentinolysis increase AMTN expression in periodontal cells, thereby helping to preserve the protective seal. Support for this assumption comes from our RNA sequencing approach showing that gingival fibroblasts exposed to acid dentin lysates (ADL) greatly increased AMTN expression. In the present study, we confirm that acid dentin lysates significantly increase AMTN in gingival fibroblasts and extend this observation towards the epithelial cell lineage by use of the HSC2 oral squamous and TR146 buccal carcinoma cell lines. AMTN immunostaining revealed an intensive signal in the nucleus of HSC2 cells exposed to acid dentin lysates. Acid dentin lysates mediate their effect via the transforming growth factor (TGF)-β type 1 receptor kinase as the antagonist SB431542 abolished the expression of AMTN in the epithelial cells and fibroblasts. Similar to what is known for fibroblasts, acid dentin lysate increased Smad-3 phosphorylation in HSC2 cells. HSC2 cells also respond to the AMTN-stimulating activity of the dentin lysate when adsorbed to gelatin. When simulating regenerative approaches, enamel matrix derivative, TGF-β1, and bone morphogenetic protein-2 also caused a robust increase in SB431542-dependent AMTN expression in HSC2. Taken together, we show here that acid dentin lysate uses the TGF-β-depended signaling pathway to support the AMTN expression in epithelial cells, possibly helping in maintaining the protective seal against the oral cavity.