Eosinophil Cationic Protein Enhances the Growth of Human Gingival Fibroblasts

Objectives: Eosinophil cationic protein (ECP) is one of the proteins released by degranulation of eosinophil. ECP is generally recognized to be involved in allergic inflammation with cytotoxic activity, because it is frequently detected in the lesion with allergic inflammation. ECP must be involved in inflammatory responses in the oral tissues also. It is important to reveal the effects of ECP on fibroblast, which is one the most major cells consist of oral tissue. The objective of this study is to see the effects of ECP on the growth of human gingival fibroblasts (HGFs) and cytokine production of them. Methods: HGFs were isolated as previously reported from healthy volunteers, and were cultured in DMEM supplemented with 10 % fetal bovine serum and 10 μg/ml of gentamycin. HGFs were stimulated by recombinant human ECP (0 - 1,000 ng/ml) for 24 hours, and 3- (4, 5- dimethylthiazol- 2- thiazoyl)- diphenyl- tetrazolium bromide (MTT) assay was performed. The cytokine production of HGFs was evaluated using a cytokine array kit (RayBiotech, Inc., GA, USA). Furthermore, the production of cytokines as follows were quantitated using an ELISA kit (RayBiotech); interleukin-6, tumor necrosis factor-α, eotaxin, regulated upon activation, normal T-cell expressed and secreted (known as RANTES), monocyte chemotactic protein (MCP)-1 , MCP-2, fibroblast growth factor (FGF)-2 , FGF-4. Results: Unexpectedly, ECP was not cytotoxic to HGFs. On the contrary, ECP enhanced the growth of HGFs at 100 ng/ml significantly (P<0.05, ANOVA / Scheffe test.). All cytokines examined were detected by cytokine array analysis, but the significant changes of them were not observed by the ELISA quantification. Conclusions: ECP does not harm HGFs, but it promotes growth of HGFs without any changes in production of cytokines we examined. Unknown mechanism still remains.