LAMININ SIKVAV PEPTIDE-INDUCED ANGIOGENESIS IN-VIVO IS POTENTIATED BYNEUTROPHILS

Angiogenesis has been investigated in vivo using subcutaneously inject ed reconstituted basement membrane (Matrigel) supplemented with angiog enic factors. Previously we found that the laminin-derived synthetic p eptide containing SIKVAV (ser-ile-lys-val-ala-val) promoted angiogenes is in vivo. In parallel studies, it was observed that new vessel forma tion in response to this peptide occurred several days after basic fib roblast growth factor-induced angiogenesis. Since this delay suggested that SIKVAV-induced angiogenesis may be secondary to other events, we investigated here earlier time points to determine if both indirect a nd direct mechanisms of angiogenesis are involved. We found that neutr ophils are continuously recruited to the SIKVAV-containing plugs betwe en 4 hours to 3 days following the initial injection. By day 7, column s of endothelial cells begin to migrate into the plug and form small b lood vessels. In contrast, neutropenic mice had a 62% reduction in SIK VAV-induced angiogenesis when compared to control mice. Freshly isolat ed neutrophils also degraded laminin, the major component of the basem ent membrane Matrigel. These cells also produced factors in response t o SIKVAV peptide which induced proliferation of human umbilical vein e ndothelial cells relative to a control peptide. In vitro experiments u tilizing human neutrophils demonstrated that these cells migrate to th e SIKVAV peptide and possess a specific cell surface SIKVAV binding pr otein of similar to 56 kD. These data suggest that neutrophils are ind uced to migrate to the Matrigel plugs, at least in part, by SIKVAV pep tide, where they may release their own angiogenic factors and degrade the matrix, thus physically facilitating cell migration and liberating additional angiogenic matrix fragments and/or cytokines. (C) 1994 Wil ey-Liss, Inc.*