Repair in arterial tissue. The role of endothelium in the permeability of a healing intimal surface. Vital staining with Evans blue and silver-staining of the aortic intima after a single dilatation trauma.

The role of the endothelium as a factor determining the permeability of a healing aortic intima after a severe mechanical lesion in the rabbit was studied by vital staining with Evans blue, by surface light microscopy after silver-staining, fluorescence microscopy and by other methods. Endothelium to develop from pre-existing endothelium in the mouths of intercostal arteries and at the borders of the lesion, remained unstained by vital staining, whereas denuded surfaces as well as pseudo-endothelium, probably derived from smooth muscle cells in the neointima, were intensely coloured. There was a general tendency towards a decreasing permeability of the aortic wall throughout an experimental period of 6 months. The determinant factor in the decreasing permeability was the presence of genuine endothelium, but changes in the endothelium, probably in the form of differentiation of intercellular junctions and changes in the connective tissue in the deeper layers, seemed to be additional factors which influenced the permeability.