Regenerative Angiogenesis: Quality Over Quantity

Angiogenesis can broadly be defined as the growth of new capillaries and blood vessels. A complex set of multiphasic signaling pathways regulate angiogenic blood vessel growth,1,2 and these pathways have been the target for both pro- and antiangiogenic therapies. Angiogenesis is a fundamental physiological process that is required for fetal development, wound healing, and tissue repair after ischemic damage. For these reasons, promoting proangiogenic pathways has therapeutic potential to combat diseases where tissue blood flow is compromised, such as peripheral artery disease, ischemic heart disease, or after ischemic stroke. Thus, quantitative methods to assess the degree of angiogenic growth are critical. Article, see p 1453 Typically, blood vessel density and the degree of angiogenic growth are quantified histologically by counting the number of capillaries observed in a defined cross section of tissue. When angiogenesis occurs, the ratio of capillaries per tissue surface area increases. Functional measures of angiogenesis include measuring perfusion to the tissue involved, and it is typically expected that these parameters (vascular density and perfusion) change in parallel. However, this is not always the case.1 In fact, injured tissue may demonstrate both an increase in capillary density and an increase in blood flow but still have underperfused areas. Such a discrepancy could be because of improper vasoregulation of new vessels, or creation of arteriovenous anastomoses that maintain overall tissue flow, …