1. ¹Department Ophthalmology, Wakayama Medical University, Kimiidera, Wakayama, Japan
2. ²Department Anatomy, Graduate School of Medicine, Osaka City University, Japan
3. ³Department of Pathology, Wakayama Medical University, Kimiidera, Wakayama, Japan
4. ⁴Department of Anatomy/Neurobiology, Graduate School of Medicine, Osaka City University, Japan
5. ⁵Laboratory of Cell Regulation and Carcinogenesis, National Cancer Institute, National Institutes of Health, Bethesda, MD, USA

Correspondence: Dr S Saika, MD, PhD, Department of Ophthalmology, Wakayama Medical University, 811-1 Kimiidera, Wakayama 641-0012, Japan. E-mail: shizuya@wakayama-med.ac.jp

Received 22 April 2004; Accepted 20 May 2004; Published online 19 July 2004.

Abstract

We examined the effect of adenovirus-mediated transient expression of Smad7, an inhibitory Smad in TGF/activin signaling, on injury-induced epithelial–mesenchymal transition (EMT) of lens epithelium in mice. A volume of 3 l of adenoviral solution was injected into the right lens of adult male C57BL/6 mice (n=56) at the time of capsular injury made using a hypodermic needle under general anesthesia. A mixture of recombinant adenovirus carrying CAG promoter-driven Cre (Cre adv) and mouse Smad7 complementary DNA (Smad7 adv) was administered to induce Smad7 expression, while control lenses were treated with Cre adv alone. After healing intervals of 2, 3, 5, and 10 days, animals were killed 2 h after labeling with bromodeoxyuridine (BrdU) and eyes were processed for histology. During healing, marked expression of Smad7 was observed in lens epithelial cells in the Smad7 adv group with loss of nuclear translocation of Smads2/3, while little Smad7 and abundant nuclear Smads2/3 were seen in cells in the Cre adv group. Lens epithelial cells in the Cre adv control group exhibited a fibroblastic appearance at days 5 and 10 and the capsular break was sealed with fibrous tissue, while Smad7 adv-treated cells around the capsular break retained their epithelial morphology and the break was not sealed. Expression of snail mRNA, and -smooth muscle actin, lumican, and collagen VI proteins, markers of EMT, was observed in control-treated eyes, but not in cells of the Smad7 adv group at day 5 with minimal expression at day 10. Additionally, cell proliferation increased in epithelium infected with Smad7 adv consistent with suppression of injury-induced upregulation of TGF1 in epithelium. We conclude that gene transfer of Smad7 in mice prevents injury-induced EMT of lens epithelial cells and sealing of the capsular break with fibrous tissue.