Effect of oxygen on the developing retinal vessels of the rabbit: III. Mode of growth of rabbit retinal vessels in tissue culture

Abstract

This paper is the third in a series reporting our studies on the effect of hyperoxia on the growing retinal vessels of the rabbit. It deals with the in vitro behaviour of the rabbit retinal complex in a normal tissue culture environment, a necessary preliminary to an investigation of the effect of hyperoxia on such cultures, which is reported in the fourth and last paper of this series. An account is given of the materials and methods employed, including timelapse cinephotomicrography, phase contrast light microscopy, conventional light microscopy and electron microscopy. The origin and mode of growth of the cells composing the vascular complex, their differentiation and formation into capillaries, and the behaviour of their associated cells are described. It was found that growth began both as a budding of mesenchymal-like cells, arising from endothelium and pericytes, and as a direct growth of endothelial cells. In either case the cultures eventually assumed the typical appearances of endothelial growth with the formation of interlacing cords or strands which very occasionally differentiated into capillaries. The outgrowth was associated with an active proliferation of macrophages, but there was no evidence that these arose from the mesenchymal or endothelial cells or vice versa. Since this is the only reported work on tissue cultures of retinal endothelium the findings are compared and contrasted with tissue culture studies of endothelium from other tissue sources.