Expression of Fractalkine and CX3CR1 in Periodontal Diseased Tissue

Objective: The regulatory role of chemokines and chemokine receptors on specific lymphocyte recruitment into periodontal diseased tissue is poorly characterized. The aim of this study is to examine the expression of fractalkine and its receptor CX3CR1 in periodontal tissue and the production of fractalkine by human umbilical vein endothelial cells (HUVEC) stimulated with pathogen-associated molecular patterns (PAMPs) including Porphyromonas gingivalis (P.gingivalis) LPS. Methods: Tissue biopsies were sampled from the inflamed gingiva of patients at surgery who were diagnosed with chronic periodontitis or from the gingiva of clinically healthy subjects. Immunohistochemical staining and RT-PCR were used to examine the expression of fractalkine and CX3CR1 in healthy and periodontal diseased tissues. HUVEC was stimulated with PAMPs (E.coli LPS, P.gingivalis LPS, S.mutans LTA and S.aureus LTA) and fractalkine mRNA expression was analyzed by RT-PCR and soluble fractalkine protein expression by ELISA. Results: Immunohistochemical staining showed that fractalkine was clearly expressed on endothelial cells in periodontal diseased tissues but expression was very slight in healthy tissues. A lot of CX3CR1 positive cells were infiltrated in periodontal diseased tissues but very few CX3CR1 positive cells were seen in healthy tissues. RT-PCR from gingival tissues demonstrated that fractalkine and CX3CR1 mRNA was expressed only in periodontal diseased tissues. ELISA and RT-PCR analysis from HUVEC revealed that all PAMPs used in this study induced fractalkine mRNA and protein by HUVEC. Conclusion: These findings suggested that CX3CR1 and the corresponding chemokine, fractalkine may have an important regulatory role on specific lymphocyte migration into inflamed periodontal tissue and fractalkine production by endothelial cells may be controlled by PAMPs in periodontal diseased tissues.