Smad3 Signaling Is Required for Epithelial-Mesenchymal Transition of Lens Epithelium after Injury

• Published in: The American journal of pathology Vol. 164; no. 2; pp. 651 - 663
• Main Authors: Saika, Shizuya, Kono-Saika, Satoko, Ohnishi, Yoshitaka, Sato, Misako, Muragaki, Yasuteru, Ooshima, Akira, Flanders, Kathleen C., Yoo, Jiyun, Anzano, Mario, Liu, Chia-Yang, Kao, Winston W.–Y., Roberts, Anita B.
• Format: Journal Article
• Language: English
• Published: Bethesda, MD Elsevier Inc 01.02.2004; ASIP; American Society for Investigative Pathology
• Subjects: Animals; Biological and medical sciences; Biomarkers - analysis; Cells, Cultured; Disease Models, Animal; DNA-Binding Proteins - biosynthesis; DNA-Binding Proteins - genetics; DNA-Binding Proteins - metabolism; Epithelial Cells - physiology; Fibrosis - physiopathology; Immunohistochemistry; In Situ Hybridization; Investigative techniques, diagnostic techniques (general aspects); Lens, Crystalline - cytology; Lens, Crystalline - injuries; Lens, Crystalline - pathology; Medical sciences; Mesoderm - cytology; Mesoderm - physiology; Mice; Mice, Knockout; Organ Culture Techniques; Pathology. Cytology. Biochemistry. Spectrometry. Miscellaneous investigative techniques; Regular; Signal Transduction - physiology; Smad3 Protein; Snail Family Transcription Factors; Swine; Trans-Activators - genetics; Trans-Activators - metabolism; Transcription Factors - biosynthesis; Transforming Growth Factor beta - biosynthesis; Eye; Visual system; Signal transduction; Anatomic pathology; Smad protein; Mesenchyma; Lens; Lesion; Epithelium
• ISSN: 0002-9440; 1525-2191
• DOI: 10.1016/S0002-9440(10)63153-7

Lens epithelial cells undergo epithelial-mesenchymal transition (EMT) after injury as in cataract extraction, leading to fibrosis of the lens capsule. Fibrosis of the anterior capsule can be modeled in the mouse by capsular injury in the lens, which results in EMT of the lens epithelium and subsequent deposition of extracellular matrix without contamination of other cell types from outside the lens. We have previously shown that signaling via Smad3, a key signal-transducing element downstream of transforming growth factor (TGF)-β and activin receptors, is activated in lens epithelial cells by 12 hours after injury and that this Smad3 activation is blocked by administration of a TGF-β2-neutralizing antibody in mice. We now show that EMT of primary lens epithelial cells in vitro depends on TGF-β expression and that injury-induced EMT in vivo depends, more specifically, on signaling via Smad3. Loss of Smad3 in mice blocks both morphological changes of lens epithelium to a mesenchymal phenotype and expression of the EMT markers snail , α-smooth muscle actin, lumican, and type I collagen in response to injury in vivo or to exposure to exogenous TGF-β in organ culture. The results suggest that blocking the Smad3 pathway might be beneficial in inhibiting capsular fibrosis after injury and/or surgery.