Induction of mesenchymal-epithelial transition (MET) by epigallocatechin-3-gallate to reverse epithelial-mesenchymal transition (EMT) in SNAI1-overexpressed renal cells: A potential anti-fibrotic strategy

Dynamic transdifferentiation of epithelial cells from epithelial-mesenchymal transition (EMT) to its reverse process, mesenchymal-epithelial transition (MET), has gained wide attention for management of cancers and tissue fibrosis. In this study, we addressed beneficial effects of epigallocatechin-3-gallate (EGCG) on EMT-MET reversion using an in vitro EMT model by overexpressing SNAI1 gene encoding Snail1, an EMT-inducing transcription factor, into renal tubular epithelial cells (pcDNA6.2-SNAI1 cells). The cells transfected with empty vector (pcDNA6.2 cells) served as the control. Titrating EGCG concentrations revealed its optimal dose at 25 µM for 24-h, which was used throughout. pcDNA6.2-SNAI1 cells had increased spindle index and typical morphology of EMT, whereas EGCG could restore the normal index and morphology. Increased nuclear Snail1 and β-catenin; increased cytoplasmic Snail1, p-GSK-3β, vimentin, fibronectin and F-actin; and decreased occludin, ZO-1, transepithelial resistance (TER), E-cadherin and cell cluster size were observed in the pcDNA6.2-SNAI1 cells. These pcDNA6.2-SNAI1 cells also had increased migrating activity associated with increased forward but decreased non-forward α-tubulin filaments, G₀/G₁ cell cycle escape, and increased matrix metalloproteinase-2 (MMP-2) and MMP-9. All of these EMT features were successfully abolished by EGCG (partially, completely, or overly). Collectively, our data have demonstrated that EGCG can reverse EMT to MET processes in renal cells. Therefore, EGCG may have the therapeutic potential as one of the promising anti-fibrotic agents to reverse the fibrotic kidney.