The effect of epigallocatechin-3-gallate (EGCG) on human alveolar bone cells both in vitro and in vivo

Objective The effects of epigallocatechin-3-gallate (EGCG), a major catechin in green tea, on human and mouse osteoblasts remain controversial. This study investigated the direct effects of EGCG on human alveolar bone-derived cells (hABCs) both in vitro and in vivo. Design hABCs which were collected from eight children (aged 7-9 years, seven males and one female) were treated with EGCG at various concentrations (1, 5, 10, 25, and 50 μM), and a proliferation assay, flow cytometric analysis for apoptosis evaluation, migration assay, and in vitro osteogenic differentiation were performed. hABCs that were pretreated with 10 μM EGCG and mixed with calcium phosphate carrier combined with EGCG (0.1, 0.5, or 1.5 mg) in vivo were transplanted into immunodeficient mouse. Histological staining, quantitative gene expressions, and alkaline phosphatase activity were evaluated in the retrieved transplants. Results The proliferation and migration were decreased when EGCG was present at over 25 μM. The osteogenic differentiation increased slightly when EGCG was present at up to 10 μM, and clearly decreased for higher concentrations of EGCG. In vivo, the potential for hard-tissue formation was slightly higher for the group with 0.1 mg of EGCG than for the control group, and decreased sharply for higher concentrations of EGCG. Conclusion The present observations suggest that EGCG at a low concentration can slightly enhance the osteogenic effect in vivo, whereas at a higher concentration it can prevent the osteogenic differentiation of hABCs both in vitro and in vivo.