Development and characterisation of a human ex vivo model of aneurysm

Background: Aortic aneurysm rupture is a cause of premature mortality worldwide. To gain insight into the pathogenesis of aneurysms, several mouse models have been developed, however at least 15% of animals suffer aortic dissection and sudden death. Our aim is to develop and characterise a reproducible ex-vivo human model of aneurysm, to be used alongside/instead of mouse models.

Methods and Results: Arteries were isolated from human umbilical cords, placed within a bioreactor and exposed to laminar flow (6.5 dynes/cm2) for 72 hours, with and without 5 uM angiotensin-II (Ang-II), or with and without 250 mM calcium chloride (CaCl2). Furthermore, the protective effects of tissue inhibitor of metalloproteinases 3 (TIMP-3), transforming growth factor beta neutralising antibody (TGF-B NAb) and an MMP-12 inhibitor (RXP470) were also investigated.

CaCl2 pre-treatment of umbilical arteries reduced medial thickness (44%; p<0.05; n=6), medial elastin content (33%; p<0.01; n=6), and medial cell density (50%; p<0.05; n=6), despite no change in vessel area. Ang-II stimulation increased total vessel area (90%; p<0.05; n=6) and medial cell density (34%; p<0.05; n=5), compared to untreated arteries. Moreover Ang-II decreased medial thickness (49%; p<0.05; n=6), and medial elastin content (61%; p<0.05; n=6) suggesting aneurysm formation. Recombinant TIMP-3, TGF-B NAb or RXP470 significantly reduced vessel dilatation (42%, 33%, 40%; p<0.05; n=5), increased medial thickness (93%, 124%, 118%; p<0.05; n=5) and elastin content (168%, 214%, 185%; p<0.05; n=5) compared to Ang-II alone.

Conclusions: Our novel ex-vivo model deploying Ang-II infusion of human umbilical cord artery, induced morphological and compositional changes associated with aneurysm formation, which are reversed by exogenous TIMP-3, TGF-B Nab or RXP470. Collectively, these findings support the use of this model for aneurysm studies, supplanting ethically challenging animal experiments.