Purification and Characterization of VEGFNPF Secreted by Human Retinal Pigment Epithelial Cells

Role of vascular endothelial growth factor in diabetic vascular complications

BACKGROUND

Much of the morbidity and mortality associated with diabetes mellitus predominantly reflects its deleterious effects on microcirculation and macrocirculation. During the past few years, rapid advancement has been made in our understanding of the mechanisms and molecules involved in the pathogenesis of diabetic microvasculopathy. This is particularly true with regard to retinal vascular disease and the role of the angiogenesis- and vasopermeability-inducing molecule, vascular endothelial growth factor (VEGF).

METHODS

Biochemical studies in many relevant cell types have been performed. Effects of VEGF action and inhibition have been evaluated in animals. Interventions that block the biochemical pathways initiated by VEGF have been tested both in culture and in animals. Human clinical trials have begun.

RESULTS

VEGF induces vascular endothelial cell proliferation, migration and vasopermeability in many cells and tissues. In vivo, VEGF has been identified as a primary initiator of proliferative diabetic retinopathy, and as a potential mediator of nonproliferative retinopathy. In addition, VEGF has been implicated in the development of neuropathy and nephropathy in the patient with diabetes. In patients with diabetes and coronary artery or peripheral vascular disease, VEGF may induce development of cardiac and limb vascular collateralization, respectively. Many biochemical processes mediating these actions have now been elucidated.

CONCLUSIONS

VEGF appears to play a central role in mediating diabetic vasculopathy in many organs. Improved understanding of the molecular mechanisms underlying these processes has permitted development of novel therapeutic interventions, several of which are now in human clinical trials. These scientific advances and various implications for the future care of vasculopathy associated with diabetes will be discussed.

Vascular endothelial growth factor and severity of nonproliferative diabetic retinopathy mediate retinal hemodynamics in vivo: a potential role for vascular endothelial growth factor in the progression of nonproliferative diabetic retinopathy

PURPOSE

To determine the effect of vascular endothelial growth factor and retinopathy level on retinal hemodynamics in nondiabetic and diabetic rats and to evaluate retinal hemodynamics in nondiabetic and diabetic patients.

METHODS

Forty-eight diabetic and 22 nondiabetic patients had their diabetic retinopathy levels determined from fundus photographs according to Early Treatment Diabetic Retinopathy Study (ETDRS). Fluorescein angiograms were recorded from the left eye by video fluorescein angiography. Retinal blood flow was calculated from the digitized angiograms. Human recombinant vascular endothelial growth factor or vehicle alone was injected intravitreally into 13 nondiabetic and 11 diabetic rats.

RESULTS

Retinal blood flow decreased 33% in patients with ETDRS retinopathy level 10 compared with control patients (P = .001) and increased sequentially in more advanced stages of retinopathy, with a strong correlation between retinal blood flow and retinopathy level (r2 = 0.434, P = .001). In the diabetic rats, retinal blood flow was decreased 35.6% (P = .01). Vascular endothelial growth factor maximally increased retinal blood flow by 36.1% in nondiabetic rats after 25 minutes (P = .001) and by 73.7% in diabetic rats after only 5 minutes (P = .01) and caused a greater response in diabetic than in nondiabetic rats.

CONCLUSIONS

Retinal blood flow increases with advancing nonproliferative diabetic retinopathy in humans, and diabetes accentuates the vascular endothelial growth factor-induced increase in retinal blood flow and venous dilation in rats. Vascular endothelial growth factor may contribute to the changes in retinal hemodynamics and morphology observed in early diabetic retinopathy.

Effect of temperature on in vitro proliferative activity of human umbilical vein endothelial cells

Human umbilical vein endothelial cells, skin fibroblasts, and retinal pigment epithelial cells are cultivated in medium supplemented with 15 to 20% serum in our laboratory. The effects of various incubation temperatures on the proliferation of these cells was examined. Our study shows that the mitogenic response of the endothelial cells to a change of temperature differed markedly from that of the fibroblasts and epithelial cells. Cultivation of human umbilical vein endothelial at 37 degrees C required seeding densities as high as 1-2 x 10(4) cells/cm2, and yet resulted in a low growth rate and premature senescence. However, under the same culture conditions, but at 33 degrees C, the proliferative capacity of these endothelial cells was potentiated. The results were striking; at 33 degrees C the cells grew actively and the life span was extended. The number of cumulative population doublings increased fourfold compared with that for the same cells cultivated at 37 degrees C. The inoculum size could be reduced, since at 33 degrees C the endothelial cells were able to replicate at seeding densities as low as 20 cells/cm2. The cells serially subcultured at 33 degrees C retained morphological features and specific immunological markers of endothelial cells.