ACE and hypertensive disorder: Although the cause of the reduced number of EPCs in hypertension is still unclear, the finding that lowering blood pressure by angiotensin receptor blockers (Bahlmann et al., 2005) or ACE inhibitors (Pirro et al., 2007) could restore their circulating numbers, in combination with their role in vascular repair, maintenance and angiogenesis, is consistent with the concept that shortage of these cells contributes to hypertension-induced rarefaction.