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J. Sapitro, A. Krishnan, X. Qiu, B. Y. J. T. Yue, H. Nakamura; Suppression of Transforming Growth Factor-β Effects in Rabbit Subconjunctival Fibroblasts by Activin Receptor-Like Kinase Inhibitors. Invest. Ophthalmol. Vis. Sci. 2008;49(13):4154.
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To evaluate the efficacy of activin receptor-like kinase (ALK) inhibitors in blocking the transforming growth factor-β (TGF-β) pathway in cultured rabbit subconjunctival fibroblasts. TGF-β2 is a cytokine involved in directing wound-healing responses in the eye including scarring following glaucoma filtration surgery.
Subconjunctival fibroblasts derived from New Zealand white rabbits were incubated with or without 2 ng/mL of TGF-β2 and treated with various concentrations of selected ALK inhibitors, SB-431542 and A-83-01, for 48 and 72 hours. The expression of connective tissue growth factor (CTGF), a TGF-β downstream mediator, was evaluated by Western blotting. Two other proteins known to be induced by TGF-β treatment, α-smooth muscle actin (α-SMA) and fibronectin, were also examined. In addition, the cell morphology of the fibroblasts was assessed microscopically.
The CTGF expression was found to be suppressed in TGF-β2-treated cultures at both 48 and 72 hour time points by 3 nM SB-431542 and 1 nM A-83-01. The suppressive effects were more pronounced when the inhibitor concentrations were increased to 10 and 3 nM, respectively. A similar reduction of α-SMA and fibronectin levels was also observed at all concentrations of the inhibitors tested. TGF-β2 caused the fibroblasts to assume an even more elongated morphology. The TGF-β2-induced morphological change could be averted by treatment of either 10 nM of SB-431542 or 3 nM of A-83-01.
Both SB-431542 and A-83-01 are effective in inhibiting the signaling pathway of TGFβ in rabbit subconjunctival fibroblasts. A-83-01 appears to be at least 3 fold more effective than SB-431542. These inhibitors may be useful in the suppression of ocular scarring, such as that seen in glaucoma filtration surgery.
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