Active hair growth (Anagen) is associated with angiogenesis

After the completion of skin development, angiogenesis, i.e., the growth of new capillaries from pre-existing blood vessels, is held to occur in the s kin only under pathologic conditions. It has long been noted, however, that hair follicle cycling is associated with prominent changes in skin perfusi on, that the epithelial hair bulbs of anagen follicles display angiogenic p roperties, and that the follicular dermal papilla can produce angiogenic fa ctors. Despite these suggestive observations, no formal proof is as yet ava ilable for the concept that angiogenesis is a physiologic event that occurs all over the mature mammalian integument whenever hair follicles switch fr om resting (telogen) to active growth (anagen). This study uses quantitativ e histomorphometry and double-immunohistologic detection techniques for the demarcation of proliferating endothelial cells, to show that synchronized hair follicle cycling in adolescent C57BL/6 mice is associated with substan tial angiogenesis, and that inhibiting angiogenesis in vivo by the intraper itoneal application of a fumagillin derivative retards experimentally induc ed anagen development in these mice. Thus, angiogenesis is a physiologic ev ent in normal postnatal murine skin, apparently is dictated by the hair fol licle, and appears to be required for normal anagen development. Anagen-ass ociated angiogenesis offers an attractive model for identifying the physiol ogic controls of cutaneous angiogenesis, and an interesting system for scre ening the effects of potential antiangiogenic drugs in vivo.