Through thick and thin collagen fibrils, stress, and aortic rupture: another piece in the jigsaw.

This century has seen a leap forward in both treatment and understanding of the molecular and pathogenetic mechanisms underlying aortic dissection. The advantages of endovascular stenting are becoming obvious, and results from the Investigation of Stent Grafts in Patients With Type B Aortic Dissection (INSTEAD) trial are pending.1 Molecular and pathogenetic advances include genetic defects mapped to several chromosomes in familial thoracic aortic dissection, including splice and missense mutations in the TGFBR2 gene on chromosome 3 associated with a Marfanoid syndrome.2 Indeed, evidence is increasing that dysregulated transforming growth factor– signaling is an underlying mechanism in aneurysm formation. The small leucine-rich proteoglycans, including biglycan, bind transforming growth factor– and regulate collagen fibrillogenesis in vitro.3 The current article by Heegaard and colleagues,4 as well as the recent work of Takaluoma et al,5 uses mouse models to further our understanding of the weaknesses in collagen fibrils that can provoke the aortic dissection characteristic of Ehlers-Danlos syndrome.