The role of PLVAP protein in endothelial cells of liver

Abstract

In endothelial cells (EC) PLVAP protein forms permeability regulating structures known as diaphragms. In some previous studies it has been stated that PLVAP does not exist in adult liver ECs, because diaphragms of liver ECs disappear after birth. On the other hand, in some previous studies both the PLVAP and the mRNA encoding it have been found in adult liver ECs. On the basis of this contradiction, the goal of this study was to clarify the role of PLVAP in development, structure and function in the ECs of liver.

In this study mouse liver tissue was analysed from PLVAP-deficient mouse strain and wild type mouse strains. From these mouse strains both embryonic and adult liver tissue were analysed. PLVAP expression was analysed by immunofluorescence staining and microscope imaging. Fine structures of ECs were analysed by electron microscopy. Endocytosis of the ECs was studied by injecting fluorescent compounds to the mice and then measuring their concentrations in ECs by flow cytometric analyses. Associations between PLVAP and other molecules in ECs were studied by proximal ligation assays.

In this study was found out that PLVAP is being expressed in both embryonic and adult liver ECs. The development of ECs, except for some fine structures, is not PLVAP-dependent although endocytosis function is severely deteriorated. There are many associations between PLVAP and other molecules in ECs, but the role of these associations remain to be studied. In conclusion, the role of PLVAP in liver EC function is substantial although not necessary.