Purification, characterization, and biological properties of the eye-derived growth factor from retina: analogies with brain-derived growth factor

Abstract

Several ocular tissues contain a polypeptide growth factor(s) (eye-derived growth factor(s) or EDGF) that stimulates the proliferation of a large variety of cells from different tissues or species. Partial purification of EDGF from adult bovine retina was accomplished by acid precipitation, blue Ultrogel chromatography, and high-pressure liquid chromatography. EDGF has an isoelectrical point at pH 4.5 +/- 0.5 and an apparent molecular weight of 17,500 +/- 3,500 measured by high-pressure liquid chromatography. On the basis of these data as well as its biological properties EDGF is different from other known growth factors. The specific activity of highly purified EDGF is 1,000-fold greater than that of a 20,000g supernatant of a crude retinal extract. At this stage of purification, EDGF stimulates replicative DNA synthesis and cell proliferation of bovine epithelium lens cells at a concentration of 14 ng/ml of culture medium and for these cells is as efficient as purified brain fibroblast growth factor. The same purification steps were applied to crude bovine brain extracts. Growth factor activity was recovered exactly as for EDGF with slightly smaller apparent molecular weight 14,000 +/- 3,500, suggesting a great similarity between the two tissues as a source of growth factors. A purification of about 2,500-fold was obtained and cell proliferation stimulated at a concentration of 100 ng/ml. Interestingly an inhibitory activity not retained on blue Ultrogel was recovered from both preparations.