Established options for revascularisation of coronary artery disease (CAD) are angioplasty or bypass surgery, both of which are unsuitable in about one in five patients because of the severity of atherosclerosis, co-morbidities, or both. An alternative therapeutic option is to promote the endogenous development of collateral vessels.

There are three principle ways in which vessel growth can occur: (1) vasculogenesis—this occurs primarily during embryonic development by differentiation of haematopoietic stem cells; (2) angiogenesis—this is the sprouting of new vessels out of existing ones, occurring during embryonic development and under certain conditions in the adult; (3) arteriogenesis—pre-existing collateral arterioles transform into arteries by dilatation, smooth muscle cells and endothelial cells proliferate, and consecutively acquire a typical arterial structure.¹ Angiogenesis is induced by various cytokines, is dependant on ischaemia, and mainly results in high resistance capillaries; true collateral artery growth is temporally and spatially dissociated from ischaemia and results in large interconnecting arterioles which …