Inhibitory Effects of Hypercholesterolemia and Ox-LDL on Angiogenesis-like Endothelial Growth in Rabbit Aortic Explants

Abstract

Hypercholesterolemic (HC) rabbits exhibit suppressed compensatory vascular growth after restriction of arterial supply. However, neovascularization is commonly found in atheromas containing inflammatory cells. We used an in vitro model to determine the effects of hypercholesterolemia on angiogenesis in the absence or presence of inflammatory cells. HC rabbit aortic explants (1 mm2) with or without (n = 90 each) lesion-forming inflammatory cells were cultured in a collagen matrix with serum-free medium. Explant-derived endothelial cell growth was organized into capillary-like microtubes (CLM) that could be videomicroscopically quantified. CLM growth from lesion-free HC explants was significantly reduced to 13 +/- 4% of the value in explants (n = 90) from normocholesterolemic (NC, n = 15) rabbits (P < .001). In contrast, in lesion-containing HC explants, the matrix was invaded by foam cells, and CLM growth was not inhibited. Immunoassayable basic fibroblast growth factor (bFGF, in pg/mL) in the culture medium was significantly lower in lesion-free HC (< 5) than NC explants (11 +/- 2, P < .01) or HC explants with lesions (14 +/- 3). In addition, CLM growth was reduced in NC explants incubated with oxidized LDL (ox-LDL, 50-100 micrograms/mL). Exogenous bFGF (10 ng/mL) reversed the inhibitory effects of hypercholesterolemia and ox-LDL, whereas bFGF-neutralizing antibody (10 micrograms/mL) abolished CLM growth in all groups. In cultured rabbit aortic endothelial cells, ox-LDL reduced DNA synthesis, but this inhibition was reversed by bFGF. We conclude that hypercholesterolemia and ox-LDL inhibit angiogenesis like endothelial growth because of a suppressed availability of endogenous bFGF. Retained responsiveness to exogenous bFGF suggests that inducing bFGF expression at targeted sites may improve collateral growth in hyperlipidemic arterial disease.

Small Concentrations of oxLDL Induce Capillary Tube Formation From Endothelial Cells via LOX-1–Dependent Redox-Sensitive Pathway

“…The latter phenomenon is in keeping with several previous studies. [21][22][23] The oxLDL treatment of HCAECs was associated with a concentrationdependent expression of LOX-1 as shown earlier. 25 Pretreatment of cells with a specific anti-LOX-1 antibody blocked the angiogenic response, suggesting that oxLDL induces tube formation from HCAECs via LOX-1 upregulation.…”

“…In contrast to the ability of small concentrations of oxLDL to stimulate tube formation, higher concentrations of oxLDL (10, 20, 40 g/mL) were noted to inhibit cell growth and cause cell injury in accordance with previous observations. [21][22][23][24] We also used native-LDL as a negative control, and found that native LDL (5 g/mL) had no effect on tube formation. Based on these findings, we chose the maximum effective concentration of oxLDL (5 g/mL) for subsequent experiments.…”

Functional Inhibition of Ras by S - trans , trans -Farnesyl Thiosalicylic Acid Attenuates Atherosclerosis in Apolipoprotein E Knockout Mice

“…Furthermore, growth factors other than vascular endothelial growth factor can also be involved in atherogenesis, which complicates the interpretation of the results. 27,28 In the present study, we did not address the effects of FTS on endothelial cell function in this atherosclerosis model.…”

Number and Migratory Activity of Circulating Endothelial Progenitor Cells Inversely Correlate With Risk Factors for Coronary Artery Disease

“…Thus, increases in age or hypercholesterolemia are associated with reduced angiogenesis. 15,16 Moreover, clinical data suggest a relation between impaired coronary blood flow regulation and risk A, EPCs were isolated from peripheral blood from 28 patients with CAD and 9 age-matched control subjects, and VEGF-stimulated migration was determined with a modified Boyden chamber. B through E, Number of migrating EPCs from 28 patients with CAD and 9 age-matched healthy volunteers was correlated with total number of risk factors (B) and individual risk factors (C through E).…”