The role of MMPs, Smad3 and heat shock proteins in TGF-beta-induced anterior subcapsular cataract development

Transforming growth factor beta (TGF-beta) has been implicated in anterior subcapsular cataract (ASC) development. In the first section of this thesis, an in-vitro rat lens model was used to determine the role of matrix metalloproteinases during TGF-beta-induced ASC. In the second part, an in-vivo TGF-beta transgenic and Smad3 knockout model was used to examine the role of Smad3 signaling pathway in TGF-beta-induced ASC development. Lastly, an in-vitro rat lens epithelial explant culture model was used to investigate the potential role of heat shock proteins (Hsps) in TGF-beta-induced epithelialmesenchymal transition (EMT). Optical, morphological and molecular changes were analyzed in theses studies.;Results from cultured rat lenses show a significant increase of back vertex distance variability (decrease of sharpness and focus) during ASC development. Inhibition of MMPs eliminated the TGF-beta-induced plaque formation. Similarly, the overexpression of TGF-beta1 in transgenic mouse lenses leads to ASC formation and a decrease in lens optical quality in comparison to wild-type lenses, while TGF-beta1/Smad3-/- (null) lenses show diminished TGF-beta-induced effects. The plaques formed in the TGF-beta1/Smad3 -/- lenses are substantially smaller than in the TGF-beta1/Smad3 +/+ lenses. The morphological and molecular changes of TGF-beta2/FGF-2 treated rat lens epithelial explants are similar to those found in the TGF-beta2 treated rat lenses and transgenic TGF-beta1 mouse lenses. Heat shock treatment prior to TGF-beta treatment significantly reduced the effects of EMT in rat LECs.;In conclusion, MMP inhibition prevented TGF-beta-induced ASC formation whereas heat shock treatment and the absence of Smad3 protein expression only reduced the severity of TGF-beta-induced effects.