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Janice L Walker, Brigid Bleaken, Liping Zhang, A Sue Menko; Vimentin is required for Repair Function During Wound Healing following Mock Cataract Surgery. Invest. Ophthalmol. Vis. Sci. 2014;55(13):3047.
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The wounding associated with cataract surgery leaves behind both the lens epithelium and a subpopulation of vimentin rich repair cells essential for effective wound-healing of the lens epithelium. The purpose of this study was to determine if vimentin, a defining feature of repair cells, is responsible both for their highly motile phenotype and their role in directing the response of an epithelium to wounding.
An ex vivo mock cataract surgery lens epithelial explant model was used for these studies. The cytoskeletal organization of repair cells at the leading edge was determined by immunofluoresence imaging. To determine if changes in vimentin detergent solubility were associated with migration, explants were first separated to enrich for cells in the original attachment zone vs. central migration zone (CMZ). Detergent soluble and insoluble pools of vimentin are reflective of different vimentin assembly states, from detergent soluble nonfilamentous vimentin particles to detergent insoluble mature vimentin filaments. Vimentin function during wound healing was examined using vimentin siRNA to knockdown vimentin expression and the vimentin inhibitor Withaferin A (WFA), which binds to and disrupts vimentin function, with an affinity for soluble vimentin.
The highly motile repair cell population was rich in vimentin intermediate filaments, which extended throughout these cells to their lamellipodia tips, a region where surprisingly few actin filaments could be detected. At the leading edge vimentin filaments extended to and inserted into paxillin rich focal adhesion structures, points of attachment during migration. Non filamentous forms of vimentin, associated with detergent soluble fractions, were also present near the tips of lamellipodia and an increase in the detergent soluble vimentin pool occurred in the CMZ region. These results reveal two distinct pools of vimentin in repair cells at the wound edge and highlight a potential function for soluble vimentin in regulating migration. Vimentin siRNA decreased vimentin expression and prevented cells at the leading edge from extending lamellipodia resulting in impaired wound closure. Parallel results were obtained with the inhibitor WFA.
These studies reveal for the first time a critical role for vimentin in repair cell function in regulating the collective movement of the epithelium in response to wounding.
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