Mice Exhibit Altered Aggrecan Proteolytic Profiles That Correlate With Ascending Aortic Anomalies.

OBJECTIVE

Investigate the requirement of Aggrecan (Acan) cleavage during aortic wall development in a murine model with ADAMTS (a disintegrin-like and metalloprotease domain with thrombospondin-type motifs) 5 deficiency and bicuspid aortic valves.

APPROACH

Mice with altered extracellular matrix remodeling of proteoglycans will be examined for anomalies in ascending aortic wall development. Neo-epitope antibodies that recognize ADAMTS cleaved Acan fragments will be used to investigate the mechanistic requirement of Acan turnover, in aortic wall development.

RESULTS

mice exhibited a high penetrance of aortic anomalies (n=17/17); mice with bicuspid aortic valves (7/17) showed a higher number of anomalies than mice with tricuspid aortic valves. Single mutant mice also displayed a high penetrance of aortic anomalies (n=19/19) compared with wild type (n=1/11). Aortic anomalies correlated with Acan accumulation that was apparent at the onset of elastogenesis in mice. Neo-epitope antibodies that recognize the initial amino acids in the Acan cleaved fragments neo-FREEE, neo-GLGS, and neo-SSELE were increased in the aortas compared with WT. Conversely, neo-TEGE, which recognizes highly digested Acan core fragments, was reduced in mice. However, mice containing a mutation in the TEGE↓ALGSV site, rendering it noncleavable, had low penetrance of aortic anomalies (n=2/4). Acan neo-DIPEN and neo-FFGVG fragments were observed in the aortic adventitia; Acan neo-FFGVG was increased abnormally in the medial layer and overlapped with smooth muscle cell loss in aortas.

CONCLUSIONS

Disruption of ADAMTS5 Acan cleavage during development correlates with ascending aortic anomalies. These data indicate that the mechanism of ADAMTS5 Acan cleavage may be critical for normal aortic wall development.