Tannic Acid Achieves Rapid Scar-Free Corneal Healing by Chelating Excess Copper to Suppress Aberrant LOX-Mediated...

Corneal scarring and fibrosis following injury remain the leading causes of visual impairment worldwide. This study aimed to evaluate the therapeutic effects of tannic acid (TA), a natural polyphenolic compound with antioxidant, anti-inflammatory, and metal-chelating properties, and to elucidate its underlying molecular mechanisms in corneal wound healing.

In vitro (human corneal epithelial and stromal cells) and in vivo (rabbit anterior lamellar keratectomy) models were established to evaluate TA's efficacy. Epithelial migration was assessed by scratch and Transwell assays, whereas TGF-β-induced models evaluated anti-fibrotic activity. Histopathology was examined by hematoxylin and eosin, Masson's trichrome staining, and α-SMA immunohistochemistry. Transcriptomic sequencing, Western blot, and RT-qPCR analyzed gene and protein expression. Copper ion concentrations were measured by inductively coupled plasma mass spectrometry (ICP-MS), and lysyl oxidase (LOX) enzymatic activity was determined using fluorometric activity assay kits.

Within biocompatible concentrations, TA dose-dependently promoted epithelial cell migration and suppressed stromal fibrosis in vitro. In vivo, TA treatment achieved rapid scar-free healing, outperforming rhEGF treatment. Mechanistic investigations revealed that TA exerts anti-fibrotic effects by downregulating LOX family gene expression and modulating collagen fibril assembly pathways. Protein and mRNA analyses confirmed that TA suppresses LOX expression and activity through chelation of excess copper ions, with functional validation via exogenous copper supplementation further supporting this mechanism.

These findings demonstrate that TA chelates excess copper ions accumulated in injured corneas, thereby mediating LOX inhibition and reducing fibrosis, representing an important mechanistic complement to TA's established antioxidant and anti-inflammatory properties.