Matrix metalloproteinase-19 in capillary endothelial cells: Expression in acutely, but not in chronically, inflamed synovium

Matrix metalloproteinase-19 (MMP-19), originally isolated as an autoantigen from the synovium of a patient suffering from rheumatoid arthritis (RA), i s expressed in smooth muscle cells of the tunica media of large blood vesse ls of an RA patient, but not in the endothelial cell layer, By contrast, in acutely inflamed tissue, synovial capillaries strongly express MMP-19 in t he cytoplasm, as shown by immunofluorescence of cryostat sections. In MMP-1 9-producing capillaries the beta 3 integrin chain was found at the endothel ial cell surface, as was the vascular endothelial cell growth factor recept or-2 (KDR), The specific tissue inhibitor of metalloproteinases TIMP-1 was absent or faintly stained in MMP-19-expressing capillaries, whereas TIMP-1, but not TIMP-2, was strongly expressed in large vessels and in MMP-19-nega tive capillaries of RA synovia, In the spontaneously transformed human umbi lical vein endothelial cell line ECV304 neither MMP-19 transcripts nor prot ein could be detected. By contrast, primary cultures of human endothelial c ells of either dermal or adipose tissue origin produced MMP-19 mRNA and pro tein. The results strongly suggest the regulated induction of matrix metall oproteinase-19 in capillary endothelial cells during acute inflammation and hint at a role of MMP-19 in angiogenesis. (C) 1999 Academic Press.