Endothelial cells are known to bind to
laminin, and two
peptides derived from the
laminin A (CTFALRGDNP) and B1 (
CDPGYIGSR) chains block the capillary-like tube formation on a
laminin-rich basement membrane matrix,
Matrigel. In the present study, we have used various in vitro and in vivo assays to investigate the angiogenic-
biologic effects of a third active site in the
laminin A chain, CSRARKQAASIKVAVSADR (designated PA22-2) on endothelial cells. The
SIKVAV-containing
peptide was as active as the
YIGSR-containing
peptide for endothelial cell attachment but was less active than either the RGD-containing
peptide or intact
laminin. Endothelial cells seeded on this
peptide appeared fibroblastic with many extended processes, unlike the normal cobblestone morphology observed on tissue culture
plastic. In addition, in contrast to normal tube formation on
Matrigel, short irregular structures formed, some of which penetrated the matrix and sprouting was more apparent. Analysis of endothelial cell
conditioned media of cells cultured in the presence of this
peptide indicated degradation of the
Matrigel and zymograms demonstrated active
collagenase IV (
gelatinase) at 68 and 62 Kd. A murine in vivo angiogenesis assay and the chick yolk sac/chorioallantoic membrane assays with the
peptide demonstrated increased endothelial cell mobilization, capillary branching, and vessel formation. These data suggest that the -
SIKVAV-site may play an important role in initiating branching and formation of new capillaries from the parent vessels, a behavior that is observed in vivo in response to
tumor growth or in the normal vascular response to injury.