Effects of insulin and transforming growth factor-beta on alkaline phosphatase activity and total protein content in human periodontal ligament cells

Abstract

OBJECTIVE: The aim of this study is to evaluate the biological effects of insulin and/or transforming growth factor (TGF-beta) on alkaline phosphatase (ALPase) activity and protein synthesis of periodontal ligament (PDL) cells in vitro. METHODS: The fifth passage of PDL cells were cultured in a 5% humid CO2 environment at 37 degrees C by using Dulbecco minimum essential medium (DMEM) supplemented with 10% fetal bovine serum (FBS) for 24 hours, and then insulin, TGF-beta, and insulin and TGF-beta were added respectively in a medium of 1% FBS. After 5 days, their ALPase activities were measured by using a kinetic method, and the total protein content was measured by using Coomassie brilliant blue staining. RESULTS: Both insulin and TGF-beta significantly increased the ALPase activity and the total protein content of PDL cells at the concentrations from 1.0 to 100 U/L, and of 0.1-100 micrograms/L. The most optimal concentrations of insulin and TGF-beta were respectively 10 U/L and 1 microgram/L. The synergistic effect of insulin (10 U/L) and TGF-beta (1 microgram/L) was observed (P < 0.01). CONCLUSION: The results suggest that insulin and/or TGF-beta may promote the differentiation and protein synthesis of PDL cells. The combination of them may be valuable in the regeneration of periodontal tissue.