Suppression of injury-induced epithelial-mesenchymal transition in a mouse lens epithelium lacking tenascin-C.
OBJECTIVE
To investigate the role of tenascin-C in epithelial-mesenchymal transition (EMT) of the lens epithelium during wound healing in mice. Tenascin-C is a component of the extracellular matrix in patients having post-operative capsular opacification.


METHODS
The crystalline lens was injured by needle puncture in tenascin-C null (KO, n=56) and wild-type (WT, n=56) mice in a C57BL/6 background. The animals were killed at day 2, 5, or 10 post-injury. Immunohistochemistry was employed to detect alpha-smooth muscle actin (alphaSMA), a marker of EMT, collagen type I, transforming growth factor beta1 (TGFbeta1), phospho-Smad2, phospho-adducin, and phospho-myosin light chain 9 (MLC9). The expression levels of phospho-adducin and phospho-MLC9 were used as markers for the activation of protein kinase C and Rho kinase, respectively.


RESULTS
The expression of tenascin-C was upregulated in WT lens epithelial cells adjacent to the capsular break at day 5. The results showed that injury-induced EMT of the mouse lens epithelium, as evaluated by histology and the expression patterns of alphaSMA and fibronectin, was attenuated in the absence of tenascin-C. Upregulation of TGFbeta1 expression in the epithelium was also inhibited, and loss of tenascin-C attenuated the phosphorylation of Smad2 and adducin in epithelial cells adjacent to the capsular break. The expression of phospho-adducin was suppressed, while the expression level of phospho-MLC9 was unchanged, in the healing epithelium in the absence of tenascin C.


CONCLUSIONS
Tenascin-C is required for injury-induced EMT in the mouse lens epithelium. The mechanism behind this might involve impaired activation of cytoplasmic signaling cascades; i.e., TGFbeta/Smad and protein kinase C-adducing signaling, in the absence of tenascin-C.
Tanaka
Sai-ichi
S
Department of Ophthalmology, Wakayama Medical University, Wakayama, Japan. s-tanaka@wakayama-med.ac.jp
Sumioka
Takayoshi
T
Fujita
Norihito
N
Kitano
Ai
A
Okada
Yuka
Y
Yamanaka
Osamu
O
Flanders
Kathleen C
KC
Miyajima
Masayasu
M
Saika
Shizuya
S
D000818:Animals; D002148:Calmodulin-Binding Proteins / Q000378:metabolism; D004848:Epithelium / Q000293:injuries* / Q000378:metabolism / Q000473:pathology*; D005353:Fibronectins / Q000378:metabolism; D007150:Immunohistochemistry; D007908:Lens, Crystalline / Q000293:injuries* / Q000378:metabolism / Q000473:pathology*; D008648:Mesoderm / Q000378:metabolism / Q000473:pathology*; D051379:Mice; D008810:Mice, Inbred C57BL; D018994:Myosin Light Chains / Q000378:metabolism; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D000077293:Receptor, Transforming Growth Factor-beta Type I; D000077294:Receptor, Transforming Growth Factor-beta Type II; D018125:Receptors, Transforming Growth Factor beta / Q000378:metabolism; D051899:Smad2 Protein / Q000378:metabolism; D019063:Tenascin / Q000172:deficiency* / Q000378:metabolism; D053773:Transforming Growth Factor beta1 / Q000378:metabolism; D000099291:Adducins
D002148:Calmodulin-Binding Proteins; D005353:Fibronectins; D018994:Myosin Light Chains; D017346:Protein Serine-Threonine Kinases; D000077293:Receptor, Transforming Growth Factor-beta Type I; D000077294:Receptor, Transforming Growth Factor-beta Type II; D018125:Receptors, Transforming Growth Factor beta; D051899:Smad2 Protein; D019063:Tenascin; D053773:Transforming Growth Factor beta1; D000099291:Adducins