The response of fenestrations, actin, and caveolin-1 to vascular endothelial growth factor in SK Hep1 cells

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Abstract
To study the regulation of fenestrations by vascular endothelial growth factor in liver sinusoidal endothelial cells, SK Hep1 cells were transfected with green fluorescence protein (GFP)-actin and GFP-caveolin-1. SK Hep1 cells had pores; some of which appeared to be fenestrations (diameter 55 ± 28 nm, porosity 2.0 ± 1.4%), rudimentary sieve plates, bristle-coated micropinocytotic vesicles and expressed caveolin-1, von Willebrand factor, vascular endothelial growth factor receptor-2, endothelial nitric oxide synthase and clathrin, but not CD31. There was avid uptake of formaldehyde serum albumin, consistent with endocytosis. Vascular endothelial growth factor caused an increase in porosity to 4.8 ± 2.6% ( P < 0.01) and pore diameter to 104 ± 59 nm ( P < 0.001). GFP-actin was expressed throughout the cells, whereas GFP-caveolin-1 had a punctate appearance; both responded to vascular endothelial growth factor by contraction toward the nucleus over hours in parallel with the formation of fenestrations. SK Hep1 cells resemble liver sinusoidal endothelial cells, and the vascular endothelial growth factor-induced formation of fenestration-like pores is preceded by contraction of actin cytoskeleton and attached caveolin-1 toward the nucleus.