Control of coronary angiogenesis.

We investigated the development of coronary collaterals in canine and porcine models using either progressive experimental coronary occlusion or microembolism of small vessels. Muscular arteries developed on the epicardial surface of canine--but not of porcine hearts, where large, thin-walled intra-myocardial capillaries developed irrespective of the type of vascular occlusion. The common motif for both types of vascular adaptation is the part played by inflammation, i.e. the involvement of monocytes/macrophages that are probably the producers of growth factors. Emphasis is placed on the importance of remodelling by controlled proteolysis to create the space for the new vascular cells.