Brain and pituitary fibroblast growth factors (FGF) have been purified to apparent homogeneity from crude tissue extracts by a three-step procedure, including salt precipitation, ion-exchange chromatography, and heparin-Sepharose affinity chromatography. Brain and pituitary FGF have similar amino acid compositions and are indistinguishable with respect to molecular weight (16,000 by polyacrylamide gel electrophoresis), retention behavior in reversed-phase high-performance liquid chromatography, and recognition by antibodies directed against the amino-terminal sequence of pituitary FGF. Brain FGF preparations purified by heparinSepharose contain, in addition to the major FGF molecular species, at least two additional forms of the growth factor, which appear to be very similar by all the above criteria, except for retention in high-performance liquid chromatography.

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An angiogenic growth factor present in bovine corpus luteum (CL) has been purified to apparent homogeneity by a combination of differential salt precipitation, ion exchange chromatography, and heparin-Sepharose chromatography. It is a single chain polypeptide with an apparent mol wt of 15,000 and an amino acid composition similar to that previously reported for pituitary and brain fibroblast growth factor (FGF). Sequence analysis of the first 17 residues of the CL-derived growth factor identified the sequence; His-Phe-Lys-Asp-Pro-Lys-Arg-Leu-Tyr-X-Lys-Asn-Gly-Gly-X-Phe-Leu. This sequence is identical to residues 16-33 of bovine pituitary and brain FGF, indicating that the CL-derived growth factor is an amino-terminally truncated form of FGF and is otherwise similar, if not identical, to FGF. The biological activity of CL FGF is indistinguishable from that of pituitary or brain FGF. It is highly active in triggering the proliferation of cultured bovine vascular endothelial cells derived either from large vessels (aortic arch) or from corpus luteum and adrenal cortex capillaries (half-maximal stimulation at 20-40 pg/ml and saturation at 400-600 pg/ml). In vivo implants containing 50 ng to 1 microgram CL-derived growth factor stimulate neovascularization in the chorioallantoic membrane of the chick embryo. In addition to being mitogenic for vascular endothelial cells, CL FGF also stimulates the proliferation of a wide variety of mesoderm- and neuroectoderm-derived cells, including vascular smooth muscle cells, granulosa and adrenal cortex cells, rabbit costal chondrocytes, and corneal endothelial cells.

The permissive effects of extracellular matrix (ECM) on in vitro growth and differentiation of fetal human retinal pigment epithelial (RPE) cells have been studied. Factors which enhanced the effect of ECM to support cell division were also examined, including growth factors, culture media, and serum requirement. Under the specific culture conditions we have defined, it is possible to propagate these RPE cells at low density (less than 20 cells/mm2) with excellent growth properties for greater than 72 doublings (fourteen passages) in serial culture. Later-passaged cells maintained the morphological appearance of early-passaged cultures. ECM produced by bovine corneal endothelial cells was by far the most predominant factor in promoting rapid cell proliferation and viability over repeated passaging. Basic fibroblast growth factor (bFGF) exerted a substantial effect on the rate of cell division at different serum concentrations on plastic dishes. In addition, this factor showed profound synergistic effect when RPE cells were maintained on ECM, both in the preservation of cell morphology and also in long term viability. Other growth factors, such as epidermal growth factor (EGF) and transforming growth factor-beta (TGF-B), were also tested, but EGF effects were less prominent than those observed with bFGF, and TGF-B had an inhibitory effect at high concentrations. The ability to obtain a relatively large number of human RPE cells in vitro which preserve the appearance of early passage cells may provide useful opportunities to study the physiological properties and pathological alterations involving this important cell type.