Transforming growth factor-alpha (TGF-α) transduces its signal through the epidermal growth factor receptor and is essential for corneal epithelial homeostasis. Previous studies have demonstrated that overexpression of TGF-α in the developing eye leads to anterior segment dysgenesis. However, the underlying mechanisms remain unclear. Here we examined the effects of TGF-α overexpression on adult ocular surface homeostasis.
Binary Tet-On transgenic Krt12(rtTA)/tet-O-TGF-α mice were subjected to doxycycline (Dox) induction to overexpress TGF-α in the corneal epithelium. Intraocular pressure (IOP) was measured by noninvasive tonometry. The enucleated eyes of the experimental mice were subjected to histopathology, immunohistochemistry, and biochemistry examination.
Histologic and immunofluorescent examination showed that double-transgenic mice overexpressing TGF-α manifested peripheral anterior synechiae. Elevation of IOP, activation of glial cells, and loss of retinal ganglion cells were also observed. Quantitative real-time PCR revealed that the expressions of genes (RXRα, PITX2, and FOXC1) related to anterior segment dysgenesis were downregulated. Canonical Wnt signaling was suppressed, whereas noncanonical Wnt ligands (Wnt4 and Wnt5a) were upregulated. Increased myosin light chain phosphorylation suggested that noncanonical Wnt signaling is activated in affected eyes.
Overexpression of TGF-α in the corneal epithelium induces changes in anterior segment morphology. Corneal endothelial abnormalities are associated with the activation of the noncanonical Wnt and RhoA/ROCK signaling axis, indicating a potential application of RhoA/ROCK inhibitors as a therapeutic strategy for certain types of secondary angle-closure glaucoma.
[Show abstract][Hide abstract] ABSTRACT: Purpose:
Dexamethasone (DEX) regulates aqueous humor outflow by inducing a reorganization of the cytoskeleton to form cross-linked actin networks (CLANs) in trabecular meshwork (TM) cells. Rho-associated protein kinase (ROCK) has been demonstrated to have an important role in this process, but the upstream components leading to its activation remain elusive. The purpose of the study is to demonstrate that noncanonical Wnt signaling mediates the DEX-induced CLAN formation in TM cells.
The TM cells were treated with 100 nM DEX in low serum medium for over 7 days. The medium was changed every 3 days. The cells were harvested and subjected to molecular analysis for the expression of Wnt ligands. Stress fiber structures were revealed by Phalloidin staining. Lentivirus-based shRNA against noncanonical Wnt receptor (Ror2) was used to determine the role of noncanonical Wnt signaling in DEX-induced CLAN formation.
The DEX induced stress fiber rearrangement in TM cells. A noncanonical Wnt ligand (Wnt5a) was upregulated by DEX as demonstrated by Wnt ligand degenerate PCR, real-time quantitative PCR (qRT-PCR), and Western blotting. Knocking-down Ror2, the receptor of noncanonical Wnt signaling, abolished the effects of DEX on the TM cells.
Our data suggest that DEX induces the upregulation of noncanonical Wnt ligand Wnt5a. Recombinant WNT5a protein induces CLAN formation through the noncanonical Wnt receptor ROR2/RhoA/ROCK signaling axis. Given the similarities between DEX-induced ocular hypertension and primary open-angle glaucoma, our results provide a mechanism of action for applying ROCK inhibitor to treat primary open-angle glaucoma.
[Show abstract][Hide abstract] ABSTRACT: Corneal wound healing studies have a long history and rich literature that describes the data obtained over the past 70 years using many different species of animals and methods of injury. These studies have lead to reduced suffering and provided clues to treatments that are now helping patients live more productive lives. In spite of the progress made, further research is required since blindness and reduced quality of life due to corneal scarring still happens. The purpose of this review is to summarize what is known about different types of wound and animal models used to study corneal wound healing. The subject of corneal wound healing is broad and includes chemical and mechanical wound models. This review focuses on mechanical injury models involving debridement and keratectomy wounds to reflect the authors' expertise.
Experimental Eye Research 04/2014; 121. DOI:10.1016/j.exer.2014.02.007 · 2.71 Impact Factor
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