Journal of Leukocyte Biology 39:233-238 (1986) SHORT COMMUNICATION Induction of Neovascularization by

Neovascularization, the process of new blood vessel growth, is an important feature of many pathologic and physiologic processes. Monocytes were iso-lated from citrated blood buffy coat of healthy adult human donors on Ficoll-Hypaque gradients. Mononuclear cells from these gradients were fractionated on discontinuous Percoll gradients; monocyte-enriched fractions were isolated and assessed for angiogenic activity in rat corneas. Freshly isolated monocytes as well as monocytes cultured for 20 hr on fibronectin-coated collagen gels failed to stimulate neovascularization. In contrast, adherent monocytes acti-vated with concanavalin A (25 g/ml) or endotoxin (5 g/ml) for 20 hr were found to be potently angiogenic. We conclude that peripheral blood monocytes must be activated to acquire the ability to induce new blood vessel growth, a process central to inflammation, wound healing, and tumor development. Key words: monocyte, macrophage, angiogenesis, neovascularization Mononuclear phagocytes, as represented by circulating monocytes and tissue macrophages, play important roles in host defense mechanisms and inflammatory disease processes, both as scavenger cells with high phagocytic capacity, and as secretory cells capable of modulating the proliferative capacity of lymphoid and other mesenchymal cells [13,17]. We and others have demonstrated an important role fo