A link between smooth muscle cell death and extracellular matrix degradation during vascular atrophy

Abstract

Objective We have previously reported that high blood flow induces neo-intimal atrophy in polytetrafluoroethylene (PTFE) aorto-iliac grafts and that a tight external PTFE wrap of the iliac artery induces medial atrophy. In both non-human primate models, atrophy with loss of smooth muscle cells and extracellular matrix (ECM) begins within 4 days. We hypothesize that matrix loss is linked to cell death, but the factors and mechanisms involved are not known. The purpose of this study was to determine commonly regulated genes in these two models, which we hypothesized would be a small set of genes that might be key regulators of vascular atrophy. Methods DNA microarray analysis (Illumina Sentrix Human Ref-8; ~23,000 genes) was performed on arterial tissue from the wrap model (n=9) and graft neointima from the graft model (n=5) one day after wrapping or the switch to high flow, respectively. Quantitative polymerase chain reaction (qRT-PCR) was also performed. Expression of this vascular atrophy gene set was also studied in two in vitro models of Fas ligand-induced cell death (cultured smooth muscle cells and organ cultured arteries). Results By microarray analysis fifteen genes were found to be regulated in the same direction in both atrophy models − 9 up-regulated and 6 down-regulated. Of these genes, 7 of 9 up-regulated genes were confirmed by RT-qPCR in both models. Upregulated genes included ECM degrading enzymes (ADAMTS4, tissue plasminogen activator, and hyaluronidase 2), possible growth regulatory factors (chromosome 8 open reading frame 4 [TC1] and leucine-rich repeat family containing 8), a differentiation regulatory factor (musculoskeletal embryonic nuclear protein 1), a dead cell removal factor (ficolin 3), and a prostaglandin transporter (solute carrier organic anion transporter family member 2A1). Five down-regulated genes were confirmed but only in one or the other model. Of the 7 up-regulated genes, ADAMTS4, tissue plasminogen activator, hyaluronidase 2, solute carrier organic anion transporter family member 2A1, leucine-rich repeat family containing 8, and chromosome 8 open reading frame 4 (TC1) were also up-regulated in vitro in cultured smooth muscle cells or cultured iliac artery by treatment with FasL, which causes cell death. However, blockade of caspase activity with ZVAD inhibited FasL-mediated cell death, but not gene induction. Conclusion A total of 7 gene products were up-regulated in two distinctly different in vivo non-human primate vascular atrophy models. In addition, induction of cell death by FasL in vitro induced 6 of these genes, including the ECM degrading factors ADAMTS4, hyaluronidase 2, and tissue plasminogen activator, suggesting a mechanism by which the program of tissue atrophy coordinately removes extracellular matrix as cells die. These genes may be key regulators of vascular atrophy.

Enhanced Caspase Activity Contributes to Aortic Wall Remodeling and Early Aneurysm Development in a Murine Model of Marfan Syndrome

“…Loss of aortic wall SMCs via apoptosis may also contribute to aneurysm development through other mechanisms. 23 Given that SMCs represent the major source of ECM protein production, apoptosis of SMCs may reduce the ability to repair connective tissue loss during early vessel wall remodeling and development. 24 Indeed, our laboratory has previously reported that reduced elastogenesis coincides with increased apoptosis during early aneurysm development in this model system.…”

A role for proteoglycans in vascular disease

“…The fragments generated by the ADAMTS enzymes and other proteases have also been observed to build up in lesions in both human [92] and in several different animal models of vascular disease [93, 98, 103]. In fact, in a primate model of blood flow-induced intimal atrophy, Kenagy and colleagues found a selective increase in ADAMTS4 and fragmented versican coinciding with ASMC death and lesion regression [93, 103-106]. Furthermore, this group went on to show that Fas ligand induced ADAMTS4 synthesis by ASMCs in vitro and that ADAMTS4 colocalized with TUNEL-positive SMCs in the vascular graft [93, 103].…”

“…Furthermore, this group went on to show that Fas ligand induced ADAMTS4 synthesis by ASMCs in vitro and that ADAMTS4 colocalized with TUNEL-positive SMCs in the vascular graft [93, 103]. In an extension of these studies, Kenagy and colleagues compared the neointimal atrophy that occurs in the baboon model of vascular graft failure to a tight external wrap graft failure model and found that of 23,000 genes, only three ECM-modifying genes were common to both models with ADAMTS4 being one of them [106]. Such findings implicate this enzyme and versican turnover as important players in vascular disease.…”

ADAMTS-1 and ADAMTS-4 Levels Are Elevated in Thoracic Aortic Aneurysms and Dissections

“…ADAMTS-1 and ADAMTS-4 were found to be highly expressed in macrophage-rich areas of human atherosclerotic plaque [11,12]. In addition, ADAMTS-4 was shown to be associated with VSMC death and vascular atrophy, and an ADAMTS-1 gene variation was shown to be associated with an increased risk of coronary artery disease events [13,14]. Most notably, Taketani and colleagues reported that ADAMTS1 expression was significantly upregulated in TAA patients in DNA microarray and real-time PCR experiments [10].…”