Effect of FDC-SP on the phenotype expression of cultured periodontal ligament cells

Introduction: Recently, a novel protein, follicular dendritic cell secreted protein (FDC-SP), has been identified in human periodontal ligament (PDL) tissue and a biomolecular study suggested that the expression of FDC-SP might be associated with the expression of the PDL phenotype. The purpose of this study was to test the effect of FDC-SP on the proliferation and phenotype of PDL cells. Material and methods: Periodontal ligament cells obtained following the 3(rd) passage were exposed to various concentrations of FDC-SP The cell proliferation was monitored by 3[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide(MTT) assay. Then, as a measure of osteogenic activity, the alkaline phosphatase (ALP) activity was recorded after 4, 7, and 14 days using p-nitrophenylphosphate as a substrate. Finally, total RNA was extracted and RT-PCR was performed for gene analysis. Results: The results indicated that PDL cells exposed to 50 ng/ml FDC-SP could proliferate more rapidly. RT-PCR results showed that the mRNA expression of epidermal growth factor receptor (EGER) was obviously upregulated and the mRNA expression of osteocalcin (OCN) and bone sialoprotein (BSP) were downregulated in PDL cells exposed to FDC-SP. Moreover, two groups of PDL cells exposed to FDC-SP showed a significant decrease of ALP activity during all the culture days. Conclusions: In sum, the findings observed in this study suggest that FDC-SP in PDL cells could positively affect the proliferation and act as a fibroblastic phenotype stabilizer by inhibiting their differentiation into mineralized tissue-forming cells.