Abstract
Purpose:
To investigate the role of palladin, actin assembly-related protein, in the cornea, we examined expression of palladin in normal, diseased, or injured corneal tissue as well as in cultured corneal fibroblasts.
Methods:
Expression of palladin and α-smooth muscle actin (α-SMA) in the rat cornea with an incision wound, in the human cornea (normal, bullous keratopathy, or keratoconus), and in cultured human corneal fibroblasts was examined by immunofluorescence or immunoblot analysis.
Results:
The expression of both palladin and α-SMA was detected at the lesion site during wound healing in the rat cornea. Whereas neither palladin nor α-SMA was detected in the normal human cornea or a cornea affected by bullous keratopathy, both proteins were detected in association with scarring in a keratoconic cornea. The expression of both palladin and α-SMA in cultured human corneal fibroblasts was increased by transforming growth factor-β (TGF-β) in a manner sensitive to inhibition by blockers of mitogen-activated protein kinase (MAPK) signaling. Finally, RNA interference-mediated depletion of palladin attenuated the TGF-β-induced up-regulation of α-SMA expression in human corneal fibroblasts.
Conclusions:
Palladin was expressed in the rat and human cornea in association with scar formation. The expression of palladin in human corneal fibroblasts was increased by TGF-β in a manner dependent on MAPK signaling and was required for the TGF-β-induced up-regulation of α-SMA. Our data thus implicate palladin in scar formation in the corneal stroma and suggest that it contributes to the up-regulation of α-SMA by TGF-β in corneal fibroblasts.