Lens-specific expression of TGF-beta induces anterior subcapsular cataract formation in the absence of Smad3.
OBJECTIVE
Smad3, a mediator of TGF-beta signaling has been shown to be involved in the epithelial-to-mesenchymal transformation (EMT) of lens epithelial cells in a lens injury model. In this study, the role of Smad3 in anterior subcapsular cataract (ASC) formation was investigated in a transgenic TGF-beta/Smad3 knockout mouse model.


METHODS
TGF-beta1 transgenic mice (containing a human TGF-beta1 cDNA construct expressed under the alphaA-crystallin promoter) were bred with mice on a Smad3-null background to generate mice with the following genotypes: TGF-beta1/Smad3(-/-) (null), TGF-beta1/Smad3(+/-), TGF-beta1/Smad3(+/+), and nontransgenic/Smad3(+/+). Lenses from mice of each genotype were dissected and prepared for histologic or optical analyses.


RESULTS
All transgenic TGF-beta1 lenses demonstrated subcapsular plaque formation and EMT as indicated by the expression of alpha-smooth muscle actin. However, the sizes of the plaques were reduced in the TGF-beta1/Smad3(-/-) lenses, as was the level of type IV collagen deposition when compared with TGF-beta1/Smad3(+/-) and TGF-beta1/Smad3(+/+) lenses. An increased number of apoptotic figures was also observed in the plaques of the TGF-beta1/Smad3(-/-) lenses compared with TGF-beta1/Smad3(+/+) littermates.


CONCLUSIONS
Lens-specific expression of TGF-beta1 induced ASC formation in the absence of the Smad3 signaling mediator, suggests that alternative TGF-beta-signaling pathways participate in this ocular fibrotic model.
Banh
Alice
A
School of Optometry, University of Waterloo, Ontario, Canada.
Deschamps
Paula A
PA
Gauldie
Jack
J
Overbeek
Paul A
PA
Sivak
Jacob G
JG
West-Mays
Judith A
JA
D000199:Actins / Q000378:metabolism; D000818:Animals; D017209:Apoptosis; D015153:Blotting, Western; D002386:Cataract / Q000209:etiology* / Q000378:metabolism* / Q000473:pathology; D024141:Collagen Type IV / Q000378:metabolism; D005353:Fibronectins / Q000378:metabolism; D019084:Fluorescent Antibody Technique, Indirect; D005786:Gene Expression Regulation / Q000502:physiology*; D005838:Genotype; D020287:In Situ Nick-End Labeling; D007903:Lens Capsule, Crystalline / Q000378:metabolism* / Q000473:pathology; D007908:Lens, Crystalline / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008822:Mice, Transgenic; D051900:Smad3 Protein / Q000172:deficiency* / Q000235:genetics; D016212:Transforming Growth Factor beta / Q000235:genetics*; D053773:Transforming Growth Factor beta1
D000199:Actins; D024141:Collagen Type IV; D005353:Fibronectins; D051900:Smad3 Protein; C497791:Smad3 protein, mouse; C508960:TGFB1 protein, human; C508961:Tgfb1 protein, mouse; D016212:Transforming Growth Factor beta; D053773:Transforming Growth Factor beta1