The response of fenestrations , actin and caveolin - 1 to vascular endothelial growth factor in SK Hep 1 cells ( a liver endothelial cell line )

To study the regulation of fenestrations by vascular endothelial growth factor in liver sinusoidal endothelial cells, SK Hep1 cells were transfected with GFP-actin and GFPcaveolin-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 and both responded to vascular endothelial growth factor by contraction towards the nucleus over hours in parallel with the formation of fenestrations. SK Hep1 cells resemble liver sinusoidal endothelial cells and the VEGF-induced formation of fenestration-like pores is preceded by contraction of actin cytoskeleton and attached caveolin1 towards the nucleus.