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It would appear that the angiogenic pheno type has evolved as a highly conserved response without the need for its own med ia tor system.Rather, endo thelial cells are able to utilize whatever growthst imu la tors and inhibitors are made available to them to produce new capillaries.For example, during embryonic deve lopmen t, bas ic fibroblast growth factor and has been shown to be the principal med ia tor of vasculogenesis and ang iogenes is.Whether angiogenic stimulators and inhibitors are tissue or processspecific is the subject of much speculation.Clearly, the great redundancy in positive and negative regulators capable of orchestrating an angiogenic response attests to its fundamental importance in pathophysiological processes. Wound healing is an essential biologic process that is driven by the cooperative interaction of a variety of cell types and mediator systems.Normal tissue repair requires that the cells and Columbin mediators of the immune system, the connective tissue, and vascular endothelium coordinate to effect the repair process in a timely and efficient manner.Although numerous cell types are involved, the monocytederived macrophage appears to play a central role in orchestrating the repair process.Macrophages migrating into healing wounds phagocytose wound debris, become activated, and secrete diffusible cytokines that modulate tissue repair. In surgical models of wound healing, activated macrophages have been shown to be the predominant cell type by day postinjury, when the proliferative phase of the repair process is most pronounced. Several reports suggested that wound macrophages function primarily to augment the repair response.The introduction of activated macrophages into healing wounds results in enhanced wound repair, and activation of wound macrophages by either systemic or topical administration of the macrophage stimulant, glucan, significantly increased woundbreaking strength. Macrophages are believed to be responsible for coordinating much of the growth and tissue remodeling that occur during the wound response.A key step in the repair process is the formation of inflammatory Farlutin granulation tissue, a temporary tissue that consists largely of new capillary blood vessels.It is now wellestablished that macrophages are key regulators of wound neovascularization.Activated macrophages or their culture supernatants have been shown to induce new capillary growth in vitro and angiogenesis in vivo. Similar results were obtained with inflammatory exudate macrophages derived from guinea pigs and mice. During the proliferative phase, growing capillaries provide nutrient support for regenerating tissues, while, during the resolution phase, many of the newly formed capillaries regress as tissue regeneration is complete.Recent evidence suggests that capillary regression may also be mediated by macrophages, since macrophages have been shown to produce substances which are inhibitory to endothelial cell growth, and some which are antiangiogenic in vivo. Thus, a substantial body of evidence has implicated the macrophage as a central regulator of wound angiogenesis.The macrophage can influence new capillary ingrowth by several different mechanisms.A second mechan ism by which macrophages might modu la te ang iogenes is is by modifying the extracellular matrix. The compos ition of the ECM has been shown to influence endo thelial cell sh ape and morphology dramatically, and may profoundly influence new capillary growth.

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