Dexamethasone induces cross-linked actin networks in trabecular meshwork cells through noncanonical wnt signaling.

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.
METHODS: 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.
RESULTS: 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.
CONCLUSIONS: 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.