RGD-containing fibrillin-1 fragments upregulate matrix metalloproteinase expression in cell culture: A potential factor in the pathogenesis of the Marfan syndrome

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Abstract
The Marfan syndrome (MFS), a relatively common autosomal dominant disorder of connective tissue, is caused by mutations in the gene for fibrillin-1 (FBN1). Fibrillin-1 is the main component of the 10- to 12-nm microfibrils that together with elastin form elastic fibers found in tissues such as the aortic media. Recently, FBN1 mutations have been shown to increase the susceptibility of fibrillin-1 to proteolysis in vitro, and other findings suggest that up-regulation of matrix metalloproteinases (MMP), as well as fragmentation of microfibrils, could play a role in the pathogenesis of MFS. In the present work, we have investigated the influence of fibrillin-1 fragments on the expression of MMP-1, MMP-2, and MMP-3 in a cell culture system. Cultured human dermal fibroblasts were incubated with several different recombinant fibrillin-1 fragments. The expression level of MMP-1, MMP-2, and MMP-3, was determined by quantitative reverse transcriptase-polymerase chain reaction (RT-PCR), and the concentration of the corresponding proteins was estimated by quantitative Western blotting. Our results establish that treatment of cultured human dermal fibroblasts with recombinant fibrillin-1 fragments containing the arginine–glycine–aspartic acid (RGD) integrin-binding motif of fibrillin-1 induces up-regulation of MMP-1 and MMP-3. A similar effect was seen upon stimulation with a synthetic RGD peptide. The expression of MMP-2 was not influenced by treatment. Our results suggest the possibility that fibrillin fragments could themselves have pathogenic effects by leading to up-regulation of MMPs, which in turn may be involved in the progressive breakdown of microfibrils thought to play a role in MFS.