In vitro proliferation of endothelial cells from kitten retinal capillaries.

When microvessel (predominantly capillary) fragments freshly isolated from the retinas of young kittens are incubated in tissue culture medium, we observe the slow outgrowth of cells that appear to be derived from the capillary endothelium. The cells grow as a monolayer with a tightly packed, mosaic-like array. Electron microscopy of these cells reveals "tight junctions" (zonulae occludentes) resembling those found in the endothelium of intact capillaries. The availability of in vitro preparations of retinal capillary endothelial cells should facilitate investigations of the causes of abnormal endothelial cell proliferation in various diseases and of factors that modify cell junctions and capillary permeability in the retina. Since we have previously demonstrated proliferation in culture of intramural pericytes ("mural cells") from retinal capillaries, it should now be possible to carry out compratative studies of biochemical and functional properties of retinal capillary pericytes and endothelial cells.