These results suggest that bFGF may promote angiogenesis both by a direct effect on endothelial cells and also indirectly by the upregulation of VEGF in VSMCs. The synergy demonstrated between hypoxia and either bFGF or TGF-beta 1 suggests that multiple diverse stimuli may interact via the upregulation of VEGF expression in VSMCs to amplify the angiogenic response.
Forty-nine patients with the Klippel-Trenaunay syndrome have been studied. Sixty-eight per cent have a superficial, embryological venous channel on the lateral aspect of the limb, 25 per cent have had one or more severe spontaneous haemorrhages from dilated varices and 22 per cent have suffered a venous thrombo-embolism. Twenty-nine per cent have had episodes of rectal bleeding or haematuria associated with pelvic angiomas. Foot volumetry (n = 31) showed that calf emptying was decreased in only five patients and only one of these had phlebographic evidence of deep venous obstruction, which conflicts with previous findings. The rate of calf refilling was increased in 81 per cent and phlebography demonstrated incompetent communicating veins in 45 per cent of patients. No patient had clinical evidence of an arteriovenous fistula, and arteriography (n = 22) and calf blood flow (n = 33) were normal, but lymphangiography (n = 14) showed lymphatic hypoplasia in 55 per cent of limbs. Eighty-eight operations have been performed on 38 patients but symptoms persist in 90 per cent. We suggest that surgery should be limited to the excision of localized symptomatic abnormalities and that the best form of control is provided by graduated compression stockings.
Oxygenation of the arterial wall is provided by diffusion of oxygen outward from the main vessel lumen and inward from the adventitial vasa vasorum. In a group of four Yucatan miniature pigs the oxygenation profiles across the superficial femoral arteries were recorded by polarographic oxygen microelectrodes. The profiles obtained suggested a relatively poorly oxygenated media (a trough value of approximately 25% that of the intimal oxygenation) with a progressive rise in oxygenation toward the intimal and adventitial surfaces. In four other survival experiments, occlusion of the adventitial vasa vasorum by flush ligation of the arterial branches that supply them resulted in the production of a focal, intimal hyperplastic lesion that was absent in control vessels (intimal to medial ratios [mean +/- SEM] of 0.053 +/- 0.008, n = 8, p < 0.001 and 0.013 +/- 0.001, n = 8, respectively). By electron microscopy this lesion was seen to be composed mainly of smooth muscle cells. This evidence would support the hypothesis that arterial wall hypoxia may be involved in the initiation of intimal hyperplasia. It is proposed that human atherosclerosis may be initiated by occlusion of the vasa vasorum and concomitant hypoxia.
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