Targetable cellular signaling events drive arterial rupture in knock-in mouse models of vascular Ehlers-Danlos Syndrome

Abstract

glycine substitutions in critical residues involved in collagen triple helix assembly (Fig. 1A, B and Supplementary Table 1).Both the Col3a1 G209S/+ and Col3a1 G938D/+ mouse models recapitulate vEDS vascular phenotypes.Mice die suddenly due to aortic rupture, aortic dissection or organ rupture, presenting with hemothorax or hemoperitoneum at necropsy. Col3a1 G938D/+ mice present with a more severe phenotype, with a median survival of 45 days compared to 400 days for the Col3a1 G209S/+ mice, p<0.0001, Fig. 1C-E). Neither mouse model shows a tendency for formation of aortic root or ascending aortic aneurysm, consistent with human phenotypes ( Supplementary Fig. 1).Although the aortic wall architecture is relatively preserved in both models, minor alterations include occasional elastic fiber breaks, decreased aortic wall thickness, and decreased collagen content ( Fig. 1F-I). Analysis by transmission electron microscopy shows disruption of elastic lamellar units including thickened elastic fibers with a moth-eaten appearance, disarray of vascular smooth muscle cells (VSMCs) between fibers, and a paucity of collagen fibrils that normally occupy the intervening space between VSMCs and adjacent elastic fibers ( Supplementary Fig. 2). Collagen fibrils within the aortic media showed wide variation in diameter with a generally smaller size when compared to control mice ( Supplementary Fig. 2), consistent with previous reports 2, 8,10 . Fibroblasts within the aortic adventitia of vEDS mice showed gross distension of the endoplasmic reticulum presumably due to impaired trafficking of abnormally folded type III collagen ( Supplementary Fig. 2).In order to evaluate the effect of drugs previously tested in other models of aortic disease such as Marfan (MFS) and Loeys-Dietz Syndrome (LDS) 11-16 , we assessed the effect of losartan, propranolol, atenolol and amlodipine on survival of vEDS mouse models. Despite all these drugs causing the predicted reduction in blood pressure ( Supplementary Fig. 3), no drugs resulted in increased survival, with losartan, propranolol, and atenolol having no impact, and amlodipine actually increasing the risk of aortic dissection ( Supplementary Fig. 3).We also tested the effect of celiprolol, a b1 antagonist/b2 agonist that previous work has proposed, on the basis of a small trial, to delay adverse events in patients with vEDS 17,18 . Surprisingly, celiprolol, while having the predicted effect on pulse rate, accelerated death from aortic dissection in both the severe Col3a1 G938D/+ and mild Col3a1 G209S/+ vEDS mouse models ( Supplementary Fig. 3). The fact that propranolol, a nonspecific b1/b2 antagonist, and atenolol, a specific b1 antagonist, had no impact on survival, suggest that this deleterious effect does not extend to all b-blockers and may be related to the drug's b2 agonism and/or a2 antagonism 19 .In order to elucidate which signaling abnormalities may mediate disease pathology in vEDS, we performed comparative transcriptional profiling by high-throughput RNA sequencing (RNA-seq) on th...