In Vivo Activation ofmetTyrosine Kinase by Heterodimeric Hepatocyte Growth Factor Molecule Promotes Angiogenesis

Abstract

Hepatocyte growth factor (HGF) is a powerful motogen and mitogen for epithelial cells. The factor is a 90-kD heterodimer composed of an alpha chain containing four kringle motifs and a beta chain showing structural homologies with serine proteases. It is, however, devoid of enzymatic activity. Recently, it has been reported that HGF activates migration and proliferation of endothelial cells and is angiogenic. In this article we discuss (1) the molecular domains of HGF required to activate in vitro and in vivo endothelial cells, studied by use of molecular mutants, and (2) the characteristics of the angiogenic response to HGF in an experimental model system of implanted reconstituted basement membrane (Matrigel). Two groups of mutants were made and used in vitro and in vivo: one with deletions of kringle domains and one with substitution at the cleavage site of the HGF precursor. In vitro, HGF variants containing only the first two (HGF-NK2) or the first three kringles (HGF-NK3) of the alpha chain did not induce proliferation of endothelial cells even if used at concentration 160-fold higher than that optimal for HGF (0.05 nmol/L). High concentrations of these mutants (4 to 8 nmol/L) activated a little endothelial cell motogenic response that was 60% lower than that elicited by HGF. Substitution of Arg 489 with Gln 489 in the HGF precursor generated an uncleavable single-chain factor, unable to induce either endothelial cell migration or proliferation. In vivo, HGF induced a dose-dependent angiogenic response, which was enhanced by heparin.

Hepatocyte growth factor-stimulated renal tubular mitogenesis: effects on expression of c-myc, c-fos, c-met, VEGF and the VHL tumour-suppressor and related genes

“…Enhanced VEGF mRNA levels may be induced by a number of events, including growth factor stimulation, induction Gene expression in HGF/SF-stimulated renal tubular mitogenesis 1427 of hypoxia and oncogene activation Grugel et al, 1995;Ikeda et al, 1995;Rak et al, 1995). In addition, Silvagno et al (1995) have reported that HGF/SF induces expression of angiogenic factors, including VEGF in vivo, and that a neutralizing antibody to VEGF partly prevented HGF-induced angiogenesis. Our results are consistent with these observations and the concept that HGF/SF has a role in the control of renal angiogenesis during development and that this role is, at least in part, mediated through the induction of VEGF expression.…”

“…HGF/SF is also believed to have a role in normal renal development and is the most potent renal tubular cell mitogen identified so far (Harris et al, 1993;Cantley et al, 1994;Woolf et al, 1995). Precise details of how HGF/SF promotes renal tubular cell mitogenesis are not known, although HGF/SF stimulation has been reported to increase in vivo expression of the VEGF gene in non-renal systems (Silvagno et al, 1995).…”

Alleviation of Aβ-induced cognitive impairment by ultrasound-mediated gene transfer of HGF in a mouse model

“…Since HGF is also an angiogenic growth factor, 9 we measured the density of vessels in the dentate gyrus of the hippocampus by fluorescein isothiocyanate (FITC)-albumin microangiography, which allows detection of capillary vessels. 19 In this study, we measured the vessel density at four different regions of interest, the ipsilateral and contralateral dentate gyri of the hippocampus to the Ab-injected side, and the ipsilateral and contralateral cortices to the Ab-injected side at 21 days after Ab injection (7 days after gene treatment; Figure 3a).…”

“…7 Moreover, HGF is a multifunctional growth factor, which has the potential to exert neurotrophic action 8 and induce angiogenesis. 9 Importantly, in vitro, exogenously applied HGF enhanced synaptic long-term potentiation in the CA1 region of the hippocampus. 10 Our previous in vivo report also demonstrated that overexpression of HGF improved memory and learning after cerebral infarction in rats.…”

Angiogenesis induced by hepatocyte growth factor in non-infarcted myocardium and infarcted myocardium: up-regulation of essential transcription factor for angiogenesis, ets

“…8,9 Recently, HGF has been reported as a mitogen exclusively for endothelial cells without the replication of vascular smooth muscle cells (VSMC), [10][11][12][13] thereby indicating it as a potential angiogenic growth factor. Indeed, activation of the HGF system promoted angiogenesis in a Matrigel system, 14 however, this system provides far from physiological conditions. Thus, there is no direct in vivo evidence of the angiogenic action of HGF.…”