Targeting the fibronectin type III repeats in tenascin-C inhibits epithelial-mesenchymal transition in the context of posterior capsular opacification.

Purpose: Posterior capsular opacification (PCO) is a common complication following extracapsular surgery, associated with fibrosis, opacification, and contraction of the posterior lens capsule. It is characterized by increased expression of extracellular matrix proteins such as tenascin-C, fibronectin, collagens, and proteoglycans. Tenascin-C is known to be critical for injury-induced epithelial-mesenchymal transition (EMT) in the lens epithelium. We aimed to target fibronectin type III repeats 1-5 within tenascin-C (TNfnIII 1-5) using an scFv (single-chain variable fragment) antibody, and to evaluate its effectiveness in the context of lens epithelial cells.

Methods: Phage display library screening was used to generate an antibody against TNfnIII 1-5. Lens epithelial cells were cultured in the presence of the scFv antibodies to evaluate the effects on cell proliferation, migration, fibronectin polymerization and deposition, matrix metalloprotease (MMP) regulation, actin stress fiber distribution, and expression of EMT markers. The effect on SMAD-dependent and SMAD-independent pathways was also examined.

Results: The scFv TN64 was found to be effective in regulating the proliferation, migration, and expression of MMP-2 and MMP-9, fibronectin polymerization and deposition, and expression of EMT markers. TN64 did not interfere with SMAD3 phosphorylation. Altered localization of β-catenin, as well as downregulation of phosphorylation of mitogen-activated protein (MAP) kinases and focal adhesion kinase (FAK), was involved.

Conclusions: Our data suggest that the TNfnIII 1-5 repeats play an important role in PCO pathology. The inhibition of EMT by TN64 is mediated by SMAD-independent, integrin-β-catenin-FAK signaling pathway, and is therefore proposed as a novel antifibrotic therapeutic candidate.