TGF-β Signaling: New Insights Into Aortic Aneurysms

Abstract

Aneurysm-osteoarthritis syndrome (AOS) is an autosomal dominant SMAD3 mutation that is characterized by aneurysms within the arterial tree and early-onset arthritis of the joints (van der Linde et al., 2012, van der Linde et al., 2013). It is uniquely different from Marfan's syndrome (MFS) which is a disorder of the extracellular matrix, specifically fibrillin-1 (Judge and Dietz, 2005). In this issue of EBioMedicine, van der Pluijm et al. dissect out the features of a whole body SMAD3 deficient mouse and compares it to a Fibulin-4 deficient mouse model (extracellular matrix defect model) (Fig. 8 of paper) (van der Pluijm et al., 2016). It is extremely interesting that while the phenotypes in aneurysm formation are similar, the molecular mechanisms are quite distinct. The authors note that there were no changes in aortic stiffness or MMP activity within the vascular smooth muscle cells (VSMCs) of the SMAD3-deficient mice, but instead more inflammatory infiltration of immune cells into the adventitia. Likewise, while both models show elevation of phosphorylated SMAD2 and ERK, the downstream targets of TGF-β signaling are decreased with SMAD3 deficiency, but have no effect or increased signaling with Fibulin-4 deficient mice (van der Pluijm et al., 2016).