Figure 3.

This figure depicts a hypothetical positive feedback cycle in the homeostasis of connective tissue fibres. As shown in the picture fibrillin-1 mutation leads to elevated serum and tissue Transforming Growth Factor-β levels, as the ability of fibrillin-1 protein to sequester latent TGF-β decreases. Through intracellular signal transduction active TGF-β up-regulates matrix metalloproteinases (MMP-3 and MMP-9). Increased MMP activity in the connective tissue in turn leads to the integrin dependent activation of latent TGF-β which results in further increase of the active TGF-β tissue level. Both aortic dissection and striae (stretch marks) may be the consequence of increased tissue activity of MMPs. This positive feedback cycle could provide a link between aortic dissection and the three extracardiac predictors (TGF-β serum level, MMP-3 expression and striae atrophicae) described in this article.