Matrix metalloproteinase expression by endothelial cells in collagen lattices changes during co-culture with fibroblasts and upon induction of decorin expression

EA.hy 926 cells, a derivative of human umbilical vein endothelial cells, in the presence of fibroblasts show the phenomena of angiogenesis, express th e proteoglycan decorin and escape apoptosis, when they are maintained in co llagen lattices, while fibroblast-free cultures do not show these changes, Virus-mediated decorin expression can substitute for the presence of fibrob lasts. Since the expression of matrix metalloproteinases (MMPs) is an essen tial step in the formation of capillaries, several MMPs and tissue inhibito rs of metalloproteinases (TIMPs) were investigated. MMP-1, MMP-2, MMP-9, an d the cell-associated MMP-14 were augmented on the protein level in the pre sence of fibroblasts. No effect was seen with respect to MMP-3, TIMP-1, and TIMP-2, Semiquantitative RT-PCRs of endothelial cells in co-culture reveal ed a 7-, 19-, and 11-fold increase for mRNAs of MMP-1, MMP-2, and MMP-14 af ter six days, respectively. Virus-mediated decorin expression also was acco mpanied by an up-regulation of these MMPs. The expression of MMP-1 mRNAs in creased 5-fold after 2 days and gradually declined thereafter. In contrast, MMP-2 and MMP-14 showed a 7-fold acid a 14-Told increase on day two which returned to basal levels within 24 h, indicating that the expression of MMP -1 is differentially regulated from MMP-2 and MMP-14. In spite of the upreg ulation of the proteases, an enhanced degradation of decorin was not observ ed. These results indicate that the expression of decorin is a sufficient s ignal in EA.hy 926 cells for a finely tuned induction of selected MMPs whic h are involved in angiogenesis whereas the up-regulation of MMPs does not l ead to the degradation of the responsible proteoglycan. (C) 2001 Wiley-Liss , inc.