Massive aggrecan and versican accumulation in thoracic aortic aneurysm and dissection
Frank S. Cikach, … , Eric E. Roselli, Suneel S. Apte
Frank S. Cikach, … , Eric E. Roselli, Suneel S. Apte
Published March 8, 2018
Citation Information: JCI Insight. 2018;3(5):e97167. https://doi.org/10.1172/jci.insight.97167.
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Research Article Vascular biology

Massive aggrecan and versican accumulation in thoracic aortic aneurysm and dissection

Abstract

Proteoglycan accumulation is a hallmark of medial degeneration in thoracic aortic aneurysm and dissection (TAAD). Here, we defined the aortic proteoglycanome using mass spectrometry, and based on the findings, investigated the large aggregating proteoglycans aggrecan and versican in human ascending TAAD and a mouse model of severe Marfan syndrome. The aortic proteoglycanome comprises 20 proteoglycans including aggrecan and versican. Antibodies against these proteoglycans intensely stained medial degeneration lesions in TAAD, contrasting with modest intralamellar staining in controls. Aggrecan, but not versican, was increased in longitudinal analysis of Fbn1mgR/mgR aortas. TAAD and Fbn1mgR/mgR aortas had increased aggrecan and versican mRNAs, and reduced expression of a key proteoglycanase gene, ADAMTS5, was seen in TAAD. Fbn1mgR/mgR mice with ascending aortic dissection and/or rupture had dramatically increased aggrecan staining compared with mice without these complications. Thus, aggrecan and versican accumulation in ascending TAAD occurs via increased synthesis and/or reduced proteolytic turnover, and correlates with aortic dissection/rupture in Fbn1mgR/mgR mice. Tissue swelling imposed by aggrecan and versican is proposed to be profoundly deleterious to aortic wall mechanics and smooth muscle cell homeostasis, predisposing to type-A dissections. These proteoglycans provide potential biomarkers for refined risk stratification and timing of elective aortic aneurysm repair.

Authors

Frank S. Cikach, Christopher D. Koch, Timothy J. Mead, Josephine Galatioto, Belinda B. Willard, Kelly B. Emerton, Matthew J. Eagleton, Eugene H. Blackstone, Francesco Ramirez, Eric E. Roselli, Suneel S. Apte

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Figure 1

Isolation and analysis of proteoglycans from human control ascending aortas and ascending thoracic aortic aneurysm and dissection (TAAD).

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Isolation and analysis of proteoglycans from human control ascending aor...
(A) Workflow of human aorta proteoglycan (PG) extraction, isolation by diethylaminoethyl (DEAE)–Sephacel chromatography and analysis. LC-MS/MS, liquid chromatography–tandem mass spectrometry; GuHCl, guanidine hydrochloride. (B) Top: Evaluation of DEAE-Sephacel fractions for glycosaminoglycan (GAG) content by safranin-O dot-blot assay. Bottom: Colorimetric quantification of safranin-O dot blot after solubilization of precipitate using cetylpyridinium chloride. FT, flow-through. (C) Fluorophore-assisted carbohydrate electrophoresis analysis for hyaluronan (HA) and chondroitin sulfate (CS) GAGs. A preparation of purified HA and CS mono- and disaccharides was used as the standard as indicated on the left. GalNAc, N-acetylgalactosamine. Sulfation positions of the saccharides are indicated as non-sulfated (0S), 2S, 4S, and 6S. (D) Western blot analysis of FT and pooled DEAE-Sephacel PG-containing fractions 1–3. Monoclonal antibody 12C5 recognizes the versican G1 domain and polyclonal antibody VC recognizes both versican and a disintegrin-like and metalloprotease domain with thrombospondin type 1 motifs (ADAMTS) protease-cleaved versican. 12C5 Western blot was performed under nonreducing conditions and VC Western blot under reducing conditions. All samples were digested with chondroitinase ABC prior to electrophoresis. Medium from HEK 293T cells transiently expressing recombinant human versican N-terminal fragment (versikine) was used as the positive control (Pos) for both antibodies.