Abstract-The roles of adventitial vasa vasorum have been highlighted in vascular wall homeostasis. Vascular endothelial growth factor (VEGF) is a potent angiogenic factor in physiological and pathophysiological conditions. However, little is known regarding the changes in adventitial vasa vasorum and the mechanism of the formation in hypertensive arteries. Accordingly, endothelial cell proliferation, adventitial vasa vasorum count, and expression of VEGF signaling axis proteins were examined in the ascending aorta of hypertensive Wistar rats that underwent suprarenal aortic constriction.Hypertension not only induced medial and adventitial thickening but also significantly increased adventitial vasa vasorum count by day 28. Preceding the medial thickening, BrdU ϩ -proliferative endothelial cells were observed in the adventitia but not in the media and intima after day 3; they peaked at day 7 and remained modestly increased at day 28. The BrdU ϩ endothelial cells showed induction of Ets-1, a transcription factor mediating angiogenic response of VEGF. Furthermore, concomitant expression of VEGF and a hypoxia-inducible transcription factor (HIF-1␣) was observed in the outer layers of medial smooth muscle cells at day 3 and extended to the middle layers of medial smooth muscle cells at day 7, returning to lower levels by day 28. In conclusion, adventitial vasa vasorum formation was induced by hypertension through the HIF-1␣/VEGF/Ets-1 pathway during hypertensive remodeling. There is convincing evidence that disruption of blood flow to the AVV results in medial necrosis 3 and intimal hyperplasia. 4,5 Moreover, it has been demonstrated that in balloon-injured arteries, the arterial wall oxygen supply is impaired after injury but is later compensated for by new AVV formation. 6 Accordingly, the role of AVV has been highlighted in vascular wall homeostasis. Most conduit and muscular arteries have vasa vasorum in the adventitia but not in the media; oxygen and nutrients are supplied by diffusion from the AVV to the outer media and from the main vessel lumen to the inner media. 7 Oxygen requirements of the vessel wall itself are relatively modest. 8 However, medial thickening may create the hypoxic zone in the media by increasing the distance required for oxygen diffusion from the lumen. 9,10 Because hypertension produces medial thickening, it is conceivable that the AVV plays a role in the maintenance of homeostasis during vascular remodeling in hypertensive arteries. However, there has been little study of the AVV in hypertensive arteries.Vascular endothelial growth factor (VEGF) has potent mitogenic and promigratory actions specific for endothelial cells (ECs), intimately linked with new vessel development in physiological and various diseased situations. 11,12 These stimulatory effects on ECs are initiated by the binding of VEGF to its high-affinity tyrosine kinase receptor Flk-1 13 and subsequently result in activation of a transcription factor, Ets-1, leading to conversion of ECs to the angiogenic phenotype. 14,15 A ...

Abstract-Recently, we have shown that in rats with a suprarenal abdominal aortic constriction (AC), pressure overload induces early perivascular fibro-inflammatory changes (transforming growth factor [TGF]-␤ induction and fibroblast proliferation) within the first week after AC and then causes the development of cardiac remodeling (myocyte hypertrophy and reactive myocardial fibrosis) associated with diastolic dysfunction. Intercellular adhesion molecule (ICAM)-1 is implicated in the recruitment of leukocytes, especially macrophages, in various inflammatory situations. Thus, we sought to investigate the causal relation of ICAM-1 to macrophage recruitment and cardiac remodeling in AC rats. In AC rats, immunoreactive ICAM-1 was observed transiently on endothelial cells of the intramyocardial coronary arterioles after day 1, with a peak at day 3, returning to baseline by day 7. Also, ED1 ϩ macrophage accumulation was found in the area adjacent to the arteries expressing ICAM-1. Chronic treatment with an anti-ICAM-1 neutralizing antibody, but not with control IgG, remarkably reduced the accumulations of macrophages and proliferative fibroblasts and inhibited the upregulation of TGF-␤ expression. Furthermore, the neutralizing antibody significantly prevented myocardial fibrosis without affecting arterial pressure and left ventricular and myocyte hypertrophy. In conclusion, ICAM-1 expression was induced by pressure overload in the intramyocardial arterioles, and triggered perivascular macrophage accumulation. In pressure-overloaded hearts, a crucial role in ICAM-1-mediated macrophage accumulation was suggested in the development of myocardial fibrosis, through TGF-␤ induction and fibroblast activation.

Abstract-A role of interferon-␥ is suggested in early development of atherosclerosis. However, the role of interferon-␥ in progression and destabilization of advanced atherosclerotic plaques remains unknown. Thus, the aim of this study was to determine whether postnatal inhibition of interferon-␥ signaling could inhibit progression of atherosclerotic plaques and stabilize the lipid-and macrophage-rich advanced plaques. Atherosclerotic plaques were induced in ApoE-knockout (KO) mice by feeding high-fat diet from 8 weeks old (w). Interferon-␥ function was postnatally inhibited by repeated gene transfers of a soluble mutant of interferon-␥ receptors (sIFN␥R), an interferon-␥ inhibitory protein, into the thigh muscle every 2 weeks. When sIFN␥R treatment was started at 12 w (atherosclerotic stage), sIFN␥R not only prevented plaque progression but also stabilized advanced plaques at 16 w: sIFN␥R decreased accumulations of the lipid and macrophages and increased fibrotic area with more smooth muscle cells. Moreover, sIFN␥R downregulated expressions of proinflammatory cytokines, chemokines, adhesion molecules, and matrix metalloproteinases but upregulated procollagen type I. sIFN␥R did not affect serum cholesterol levels. In conclusion, postnatal blocking of interferon-␥ function by sIFN␥R treatment would be a new strategy to inhibit plaque progression and to stabilize advanced plaques through the antiinflammatory effects.