Therapeutic angiogenesis is a promising approach to re-establish cardiac perfusion following ischemia or in heart failure. Recently, it has been proposed that a combination of growth factors may be key to the generation of stable vascular networks. However, it is currently unknown what growth factor combinations are optimal for therapeutic angiogenesis and what mode of administration is most adapted to achieve functional revascularization of the heart.

The aim of this study was to investigate the effects of novel growth factor combinations and to evaluate their angiogenic effects in vivo following delivery with a new biodegradable polymer system.

First, we found that FGF-2 (Fibroblast Growth Factor-2) and HGF (Hepatocyte Growth Factor) display synergistic stimulatory effects on the migration and proliferation of murine endothelial cells in vitro. Furthermore, we show that whereas HGF potentiates the proliferative effect of FGF-2 in smooth muscle cells, the HGFinduced mobility response in these cells is enhanced by FGF-2. The molecular mechanisms of the reciprocal stimulatory effects involve upregulation in endothelial cells of the HGF receptor, c-Met, by FGF-2, and vice versa upregulation of the FGFR-1 by HGF stimulation.

Next, we determined the release potential of a new polymeric delivery system based on biodegradable alginate microparticules adapted for cardiac injection. We found that FGF-2 is liberated during less than 1 month with a strong initial level of release during the first ten days. In contrast, HGF is continuously liberated during 40 days with a maximal release around day eighth. Our in vivo data, from a Matrigel plug assay in mice, indicate a significantly increased efficacy of angiogenic therapy using growth factors delivered by alginate polymers. Moreover, we found that a combination of HGF and FGF-2 displays a potent synergistic angiogenic effect in vivo.

In conclusion, we demonstrate the potential of the specific combination of FGF-2 and HGF in obtaining a synergistic stimulatory effect in vitro and in vivo. Further, our new alginate-based injectable polymeric system seems well adapted for delivery of growth factors for therapeutic angiogenic approaches to ameliorate cardiac perfusion.