Ferritin Expression in Human Periodontal Ligament Cells

Objectives: Periodontal ligament (PDL) plays important roles in homeostasis, remodeling and regeneration of periodontal tissues. To clarify the character of PDL at molecular level, we analyzed an expression profile of active genes in the human PDL obtained by collecting sequences with a full length cDNA library of PDL. Interestingly, we found high expression of both Ferritin heavy chain (FTH) and Ferritin light chain (FTL) in the library. Ferritins are ubiquitous and well-characterized iron storage and detoxification proteins that play a key role in iron metabolism. However, no information of Ferritins in human PDL has been reported. In this study, we examined the Ferritins expression in human PDL cells during the osteogenic differentiation in vitro. Methods: The expression of FTH and FTL in various human tissues was analyzed by real-time PCR. Several primary cultured human cells, including PDL cells, gingival fibroblasts, bone-marrow stromal cells and dental pulp cells were cultured in á-MEM with 10%FCS in the presence of â-glycerophosphate and á-ascorbic acid. Messenger RNA expression of FTH and FTL was analyzed by real-time PCR. Results: The expression of FTH and FTL were observed in all human tissues tested and FTL expression was more prominent than FTH. The expression of either FTH or FTL in PDL was much higher than other human tissues. Interestingly, Ferritin was down-regulated during the course of osteogenic differentiation and the expression patterns of Ferritin were not only tissue-specific but also cell-specific. Conclusion: This is the first report of both FTH and FTL expressions in human PDL. Iron is critical for cytodifferentiation of PDL cells. We speculate that Ferritin may be involved in not only iron storage but also the periodontal-tissue homeostasis. This study was supported jointly by Grant-in Aids from Japan Society for the Promotion of Science (No. 23249086 and No. 23390478) and China Scholarship Council.