Expression and Regulation of the Cell Surface Proteins CD47 and SIRPα in Resident Periodontal Cells

Periodontal disease is an inflammatory disorder affecting the supporting tissues of the tooth. The inflammation triggers a destruction of the connective- and bone tissue surrounding the tooth, a process that is not fully elucidated. It is known that periodontitis shares features with other inflammatory disease like Crohn's disease and rheumatoid arthritis. The cell surface proteins signal regulatory protein alpha (SIRPα) and cluster of differentiation 47 (CD47) are important for the progression of the inflammation in rheumatoid arthritis and Crohn's disease. It has also been shown that lack of SIRPα or CD47 render in reduced number of osteoclast. The aim of this study was to investigate if cells from the periodontium (human gingival fibroblasts) from periodontally healthy individuals express SIRPα and CD47 and if the expression of these membrane proteins is regulated under inflammatory conditions. We demonstrate, by using quantitative rt-qPCR, that human gingival fibroblasts express both CD47 and SIRPα mRNA. The expression of SIRPα was positively regulated (2-fold) by the pro-inflammatory cytokines tumor necrosis factor alpha (TNF-α) and interleukin-1-beta (IL-1β). TNF-α caused a 2-fold up-regulation of CD47 in human gingival fibroblasts. Neither CD47 nor SIRPα were time-dependently regulated by the two pro-inflammatory cytokines. We here conclude that SIRPα and CD47 gene expression are up-regulated in human gingival fibroblasts cultured under inflammatory conditions. These findings indicate that SIRPα and CD47 may play a role in periodontal disease.