A new model of anterior subcapsular cataract: involvement of TGFbeta/Smad signaling.
OBJECTIVE
To develop a new animal model of anterior subcapsular cataract formation by topical application of alkali to the eye and to examine the role of Transforming growth factorbeta/Smad3 (TGFbeta/Smad3) signaling in the formation of this cataract model.


METHODS
Under anesthesia, one eye of adult Wistar rats (n=142) was subjected to alkali burn by topical application of 1 N NaOH. The eye was then histologically examined at specific time intervals. Immunohistochemistry with a battery of antibodies was carried out to examine the epithelial-mesenchymal transition (EMT) in lens epithelium. Enzyme immunoassay was employed to determine the level of growth factors in aqueous humor and lens tissue. Smad3-null mice were also used to examine the role of Smad3 signaling in cataractogenesis in this model.


RESULTS
Two days post-burn of the ocular surface, lens epithelium underwent EMT as evidenced by the upregulation of Snail and alpha-smooth muscle actin and formed a multilayer of cells beneath the capsule. Smad signaling was found to be activated in EMT-type lens cells. The majority of myofibroblast-type lens cells expressed proliferative cell nuclear antigen (PCNA). The total amount of active TGFbeta2, total TGFbeta2, and Fibroblast growth factor 2 (FGF2) increased in the aqueous humor and lens. Loss of Smad3 attenuated, but did not completely abolish, EMT in the lens epithelium.


CONCLUSIONS
Topical alkali treatment of the ocular surface readily induces an EMT-type anterior subcapsular cataract. Smad3 signaling is involved, but not required, for achievement of EMT in the lens epithelium in this cataract model.
Shirai
Kumi
K
Department of Ophthalmology, Wakayama Medical University, Kimiidera, Wakayama, Japan. shirai@wakayama-med.ac.jp
Saika
Shizuya
S
Tanaka
Takeshi
T
Okada
Yuka
Y
Flanders
Kathleen C
KC
Ooshima
Akira
A
Ohnishi
Yoshitaka
Y
D000199:Actins / Q000378:metabolism; D000468:Alkalies; D000818:Animals; D001082:Aqueous Humor / Q000378:metabolism; D002057:Burns, Chemical / Q000150:complications* / Q000378:metabolism*; D002386:Cataract / Q000209:etiology* / Q000473:pathology; D016923:Cell Death; D049109:Cell Proliferation; D004195:Disease Models, Animal; D004848:Epithelium / Q000473:pathology; D016222:Fibroblast Growth Factor 2 / Q000378:metabolism; D005347:Fibroblasts / Q000378:metabolism; D007908:Lens, Crystalline / Q000378:metabolism / Q000473:pathology; D008297:Male; D008648:Mesoderm / Q000473:pathology; D051379:Mice; D018345:Mice, Knockout; D009130:Muscle, Smooth / Q000378:metabolism; D032389:Myocytes, Smooth Muscle / Q000378:metabolism; D018809:Proliferating Cell Nuclear Antigen / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction; D051900:Smad3 Protein / Q000378:metabolism*; D000071250:Snail Family Transcription Factors; D014018:Tissue Distribution; D014157:Transcription Factors / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000378:metabolism*; D053781:Transforming Growth Factor beta2
D000199:Actins; D000468:Alkalies; D018809:Proliferating Cell Nuclear Antigen; D051900:Smad3 Protein; C000604450:Snai2 protein, rat; D000071250:Snail Family Transcription Factors; D014157:Transcription Factors; D016212:Transforming Growth Factor beta; D053781:Transforming Growth Factor beta2; D016222:Fibroblast Growth Factor 2