The type III intermediate filaments (IFs) are essential cytoskeletal elements of mechanosignal transduction and serve critical roles in tissue repair. Mice genetically deficient for the IF protein vimentin (Vim -/-) have impaired wound healing from deficits in myofibroblast development. We report a surprising finding made in Vim -/- mice that corneas are protected from fibrosis and instead promote regenerative healing after traumatic alkali injury. This reparative phenotype in Vim -/- corneas is strikingly recapitulated by the pharmacological agent withaferin A (WFA), a small molecule that binds to vimentin and down-regulates its injury-induced expression. Attenuation of corneal fibrosis by WFA is mediated by down-regulation of ubiquitin-conjugating E3 ligase Skp2 and up-regulation of cyclin-dependent kinase inhibitors p27 Kip1 and p21 Cip1. In cell culture models, WFA exerts G 2/M cell cycle arrest in a p27 Kip1- and Skp2-dependent manner. Finally, by developing a highly sensitive imaging method to measure corneal opacity, we identify a novel role for desmin overexpression in corneal haze. We demonstrate that desmin down-regulation by WFA via targeting the conserved WFA-ligand binding site shared among type III IFs promotes further improvement of corneal transparency without affecting cyclin-dependent kinase inhibitor levels in Vim -/- mice. This dissociates a direct role for desmin in corneal cell proliferation. Taken together, our findings illuminate a previously unappreciated pathogenic role for type III IF overexpression in corneal fibrotic conditions and also validate WFA as a powerful drug lead toward anti-fibrosis therapeutic development.
All Science Journal Classification (ASJC) codes
- Molecular Biology
- Cell Biology