Abstract-Hepatocyte growth factor (HGF) exclusively stimulates the growth of endothelial cells without replication of vascular smooth muscle cells and acts as a survival factor against endothelial cell death. Therefore we hypothesized that a decrease in local vascular HGF might be related to the pathogenesis of peripheral arterial disease. We initially evaluated vascular HGF concentration in the vessels of patients with arteriosclerosis obliterans. Consistent with in vitro findings that hypoxia downregulated vascular HGF production, vascular HGF concentration in the diseased segments of vessels from patients with arteriosclerosis obliterans was significantly decreased as compared with disease-free segments from the same patients (PϽ0.05), accompanied by a marked reduction in HGF mRNA. On the other hand, a novel therapeutic strategy for ischemic diseases that uses angiogenic growth factors to expedite and/or augment collateral artery development has recently been proposed. Thus in view of the decreased endogenous vascular HGF, rhHGF (500 g/animal) was intra-arterially administered through the internal iliac artery of rabbits in which the femoral artery was excised to induce unilateral hind limb ischemia, to evaluate the angiogenic activity of HGF, which could potentially have a beneficial effect in hypoxia. Administration of rhHGF twice on days 10 and 12 after surgery produced significant augmentation of collateral vessel development on day 30 in the ischemic model as assessed by angiography (PϽ0.01). Serial angiograms revealed progressive linear extension of collateral arteries from the origin stem artery to the distal point of the reconstituted parent vessel in HGF-treated animals. In addition, we examined the feasibility of intravenous administration of rhHGF in a moderate ischemia model. Importantly, intravenous administration of rhHGF also resulted in a significant increase in angiographic score as compared with vehicle (PϽ0.01). Overall, a decrease in vascular HGF might be related to the pathogenesis of peripheral arterial disease. In the presence of decreased endogenous HGF, administration of rhHGF induced therapeutic angiogenesis in the rabbit ischemic hind limb model, as potential cytokine supplement therapy for peripheral arterial disease. (Hypertension. 1999;33:1379-1384.)

Endothelial cells are known to secrete various antiproliferative and vasodilating factors, such as nitric oxide and natriuretic peptides. The presence of endothelial dysfunction, well known in hypertensive individuals, potentially results in the development and progression of atherosclerosis. Therefore, it is important to know the factors that might influence endothelial cell growth. We examined the mitogenic actions of hepatocyte growth factor (HGF) on human endothelial and vascular smooth muscle cells. Exogenously added human recombinant HGF stimulated endothelial but not vascular smooth muscle cell growth in a dose-dependent manner. We also compared the mitogenic action of HGF with that of basic fibroblast growth factor and vascular endothelial growth factor. Interestingly, the mitogenic action of HGF on endothelial cells was greater than the actions of basic fibroblast growth factor and vascular endothelial growth factor, whereas basic fibroblast growth factor but not HGF and vascular endothelial growth factor stimulated vascular smooth muscle cell growth. Given the characteristics of HGF as an endothelium-specific growth factor, we evaluated the relationship of circulating HGF and blood pressure in normotensive and hypertensive subjects. Serum HGF concentration has been reported to be elevated in response to organ damage, such as in hepatitis and nephritis, and recent findings show that HGF may play an important role in tissue regeneration. We hypothesized that HGF might contribute to the protection or repair of vascular endothelial cells. If so, serum HGF level might be elevated in response to endothelial cell damage induced by hypertension. To test this hypothesis, we measured serum levels of HGF, lipoprotein(a), plasminogen activator inhibitor-1, tissue plasminogen activator, total cholesterol, and blood pressure in 41 normotensive and hypertensive subjects without liver, kidney, or lung damage. Serum HGF concentration was significantly correlated with systolic pressure (P < .01, r = .43) but not diastolic pressure. Serum HGF concentration in hypertensive subjects was significantly higher than in normotensive subjects. None of the other factors showed any correlation with blood pressure. We have demonstrated that HGF is an endothelium-specific growth factor whose serum concentration is significantly associated with systolic pressure. These results suggest that HGF secretion might be elevated in response to high blood pressure as a counterregulatory system against endothelial dysfunction.

Background-Although hepatocyte growth factor (HGF), a novel angiogenic growth factor, plays an important role in angiogenesis, regulation of local HGF production under hypoxia has not yet been clarified in vascular smooth muscle cells (VSMC) and endothelial cells (EC). Thus, we have studied the role of HGF in hypoxia-induced endothelial injury and the regulation of local vascular HGF expression in response to hypoxia. Methods and Results-HGF attenuated hypoxia-induced endothelial cell death. Importantly, hypoxic treatment of EC resulted in a significant decrease in local HGF production according to the severity of hypoxia and increased VEGF. Similarly, hypoxia significantly decreased in mRNA and protein of HGF and increased VEGF production in VSMC. In organ culture system, local HGF production was also significantly decreased by hypoxia (PϽ0.01). Downregulation of HGF by hypoxia is due to a significant decrease in cAMP, as hypoxic treatment decreased cAMP, a stimulator of HGF. Although active TGF-␤, a suppressor of HGF, was increased at 72 hours after hypoxic treatment, treatment of anti-TGF-␤ antibody did not attenuate decreased HGF production. Finally, rHGF was intra-arterially administered into unilateral hind limb ischemia rabbits, to evaluate in vivo angiogenic activity. Of importance, a single intra-arterial administration of rHGF reduced severe necrosis due to ischemia in rabbit muscle, accompanied by a significant increase in angiographic score (PϽ0.01). Conclusions-Overall, these data demonstrated that hypoxic treatment of vascular cells significantly downregulated HGF production due to decreased cAMP, suggesting their potential roles in the pathophysiology of ischemic diseases. Moreover, administration of rHGF induced therapeutic angiogenesis, accompanied by improvement of necrotic changes in the ischemic hind limb model, as cytokine supplement therapy for peripheral arterial disease. (Circulation. 1999;100[suppl II]:II-301-II-308.

Although most therapeutic strategies to prevent restenosis are designed to inhibit vascular smooth muscle cell (VSMC) proliferation directly, VSMC proliferation might be indirectly inhibited by re-endothelialization, as endothelial cells secrete antiproliferative and antithrombotic substances. We hypothesized that application of an endothelium-specific growth factor to balloon-injured arteries could accelerate re-endothelialization, thereby attenuating intimal hyperplasia. In this study, we investigated in vivo gene transfer of human HGF that exclusively stimulated endothelial cells without replication of VSMC growth into injured vessels. Transfection of human HGF gene into rat balloon-injured carotid artery resulted in significant inhibition of neointimal formation up to at least 8 weeks after transfection, accompanied by detection of human immunoreactive HGF. Induction of re-endothelialization induced by overexpression of human HGF gene transfer into balloon-injured vessels is supported by