The Effects of Epigallocatechin-3-Gallate and Mechanical Stimulation on Osteogenic Differentiation of Human Mesenchymal Stem Cells: Individual or Synergistic Effects

This study aims to investigate the roles and effects of EGCG (epigallocatechin-3-gallate) during the osteogenic differentiation of human mesenchymal stem cells (hMSCs) in vitro. Recent studies have shown that proper mechanical stimuli can induce osteogenic differentiation of hMSCs apart from biochemical factors. In this study, the hMSC cultures were subjected to: (1) 25 uM EGCG alone or (2) 3% mechanical stretching (0.2 Hz for 4 h/day for 4 days) or (3) in combination with 3% mechanical stretching (0.2 Hz for 4 h/day for 4 days). The two factors were applied to the cell cultures separately and in combination to investigate the individual and synergistic effect of both mechanical stimulation and ECGC in the osteogenic differentiation of hMSCs. Utilizing real time PCR, we measured various osteogenic markers and even those related to intracellular signalings. Further investigation of mitochondria was performed that mitochondria biogenesis, antioxidant capacity, and morphological related markers were measured. hMSCs were to be osteogenic or myogenic differentiated when they were under 3% stretching only. However, when EGCG was applied along with stretching they were to be osteogenic differentiated rather than to be myogenic differentiated. This was supported by evaluating intracellular signalings: BMP-2 and VEGF. Therefore, the synergistical effects of simultaneous employment of stretching and EGCG on osteogenic differentiation were confirmed. Moreover, simultaneous employment was found positive in mitochondria biogenesis, antioxidant capacity, and morphological changes. Through this study, we came into the conclusion that the combination of proper mechanical stretching, 3% in this study, and EGCG promote osteogenic differentiation. Reflecting that EGCG can be obtained from plants not from the chemical syntheses, it is worth to be studied further either by animal tests or long-term experiments for clinical applications.