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C. Saravanan, F. T. Liu, I. K. Gipson, N. Panjwani; Galectin-3 Promotes Formation of Lamellipodia, Filopodia and Tunneling Nanotube (TNT)-Like Structures in Corneal Epithelium. Invest. Ophthalmol. Vis. Sci. 2007;48(13):2736.
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We have previously shown that: (i) re-epithelialization of corneal wounds is significantly slower in galectin-3-deficient mice compared to the wild type mice, and (ii) the exogenous addition of galectin-3 stimulates re-epithelialization of corneal wounds in a mouse animal model (J. Biol. Chem. 277:42299-42305, 2002). In an effort to define the molecular mechanism by which galectin-3 stimulates the cell migration, the goal of the present study was to characterize the lectin-induced morphological changes in human corneal epithelial cells in vitro.
Confluent and sparse cultures of human corneal epithelial cells were exposed to varying amounts of recombinant galectin-3 in serum-free media. At the end of incubation period (5 to 30 minutes), the cells were stained with rhodamine-conjugated phalloidin and were examined by fluorescence microscopy.
In sparse cultures, within 30 minutes after the treatment with galectin-3, a significant number of cells showed changes in cell shape with filopodial and lamellipodial extensions characteristics of motile cell morphology. In addition, actin-rich tube-like connecting structures were noted in the monolayer cultures treated with galectin-3 but not in controls. The galectin-3-induced connecting structures observed between the cells differ from previously described tunneling nanotubes (TNTs, 50-200 nm diameter) in that they are much larger (1-3 µm diameter), and are resistant to fixation and light exposure as opposed to TNTs. The stimulatory effect of galectin-3 on the formation of connecting structures was dose dependent and was specifically inhibited by a competing sugar, ß-lactose, but not by an irrelevant disaccharide, sucrose.
Galectin-3 may influence re-epithelialization of corneal wounds by initiating the formation of lamellipodia and filopodia in corneal epithelial cells. Moreover, galectin-3-induced formation of actin-rich cell-cell connecting structures may help in intercellular communications during epithelial sheet movement.
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