Possible dual role of decorin in abdominal aortic aneurysm

Single-Cell Transcriptomics Identifies Selective Lineage-Specific Regulation of Genes in Aortic Smooth Muscle Cells in Mice

BACKGROUND

Smooth muscle cells (SMCs) of the proximal thoracic aorta are derived from second heart field (SHF) and cardiac neural crest (CNC) lineages. Recent studies, both in vitro and in vivo, have implied relevance of lineage-specific SMC functions in the pathophysiology of thoracic aortic diseases; however, whether 2 lineage-derived SMCs have any predisposed transcriptional differences in the control aorta remains unexplored.

METHODS

Single-cell RNA sequencing and single-nucleus assay for transposase-accessible chromatin sequencing were performed on isolated cells from the aortic root and ascending aortas of 14-week-old SHF-traced (Mef2c-Cre+/0-Yfp+/0) and CNC-traced (Wnt1-Cre+/0-Yfp+/0) male mice. RNA in situ hybridization was performed for spatial expression of selected differentially expressed genes (DEGs) of both lineages.

RESULTS

Lineage stratification of SMCs in the proximal thoracic aorta was identified using antibody-based immunofluorescence staining. Single-cell RNA sequencing recognized 12 consistently upregulated DEGs (Des, Tnnt2, Hand2os1, Psd, Gpc3, Meis2, Dcn, Gm34030, Palld, Nrtn, Lum, and Cfh) in SHF-derived SMCs and 9 consistently upregulated DEGs (Ccn5, Ccdc42, Tes, Eln, Aebp1, Galnt6, Ccn2, Aopep, and Wtip) in CNC-derived SMCs. RNA in situ hybridization validated upregulated expressions of selective SHF-specific DEGs at the aortic root. We found SHF-derived SMCs contain a distinct, large subpopulation of SMCs that is enriched with Des and Tnnt2 expressions. Single-nucleus assay for transposase-accessible chromatin analysis further confirmed higher chromosomal accessibility for upregulated DEGs of SHF-derived SMCs.

CONCLUSIONS

The present study recognizes the presence of limited but distinct transcriptomic differences between CNC-derived and SHF-derived SMCs in the control proximal thoracic aorta.

Is There Enough Evidence to Support the Role of Glycosaminoglycans and Proteoglycans in Thoracic Aortic Aneurysm and Dissection?—A Systematic Review

Altered proteoglycan (PG) and glycosaminoglycan (GAG) distribution within the aortic wall has been implicated in thoracic aortic aneurysm and dissection (TAAD). This review was conducted to identify literature reporting the presence, distribution and role of PGs and GAGs in the normal aorta and differences associated with sporadic TAAD to address the question; is there enough evidence to establish the role of GAGs/PGs in TAAD? 75 studies were included, divided into normal aorta (n = 51) and TAAD (n = 24). There is contradictory data regarding changes in GAGs upon ageing; most studies reported an increase in GAG sub-types, often followed by a decrease upon further ageing. Fourteen studies reported changes in PG/GAG or associated degradation enzyme levels in TAAD, with most increased in disease tissue or serum. We conclude that despite being present at relatively low abundance in the aortic wall, PGs and GAGs play an important role in extracellular matrix maintenance, with differences observed upon ageing and in association with TAAD. However, there is currently insufficient information to establish a cause-effect relationship with an underlying mechanistic understanding of these changes requiring further investigation. Increased PG presence in serum associated with aortic disease highlights the future potential of these biomolecules as diagnostic or prognostic biomarkers.

Tissue-specific smooth muscle cell subtypes identified by transcriptional profiling

Smooth muscle cells (SMCs) are specialized cells present in many organs where they serve diverse tissue-specific functions. Using the Tabula Muris compendium of single-cell RNA sequencing data, we extracted individual SMC transcriptomes from eight mouse tissues to investigate the transcriptomic landscape of tissue-specific SMCs. We identified marker genes, signaling pathways, and biological processes enriched in tissue-specific SMCs, and inferred potential ligand-receptor interaction between SMC and other cell types. Our analysis also identified sex differences in SMC gene expression in different tissues. Lastly, we used unsupervised clustering to identify novel SMC subtypes based on their downstream targets of transcription factors. Our results highlight the variable SMC phenotypes and underscore this cell's remarkable adaptability to contribute to diverse tissue function.

A Novel Hybrid Drug Delivery System for Treatment of Aortic Aneurysms

Ongoing aortic wall degeneration and subsequent aneurysm exclusion failure are major concerns after an endovascular aneurysm repair with a stent-graft. An ideal solution would be a drug therapy that targets the aortic wall and inhibits wall degeneration. Here, we described a novel drug delivery system, which allowed repetitively charging a graft with therapeutic drugs and releasing them to the aortic wall in vivo. The system was composed of a targeted graft, which was labeled with a small target molecule, and the target-recognizing nanocarrier, which contained suitable drugs. We developed the targeted graft by decorating a biotinylated polyester graft with neutravidin. We created the target-recognizing nanocarrier by conjugating drug-containing liposomes with biotinylated bio-nanocapsules. We successfully demonstrated that the target-recognizing nanocarriers could bind to the targeted graft, both in vitro and in blood vessels of live mice. Moreover, the drug released from our drug delivery system reduced the expression of matrix metalloproteinase-9 in mouse aortas. Thus, this hybrid system represents a first step toward an adjuvant therapy that might improve the long-term outcome of endovascular aneurysm repair.

SIRT1 protects against aortic dissection by regulating AP-1/decorin signaling-mediated PDCD4 activation

Medial degeneration of aorta wall is the principal feature of aortic dissection (AD). Sirtuin 1 (SIRT1) plays essential protective effect on many aortic-associated disease. However, it is still unclear whether SIRT1participates in the process of medial degeneration-mediated AD. The purpose of this study is to explore the association between SIRT1 and AD process. qRT-PCR was used to evaluate the transcriptional level of genes involved in study. Protein levels and acetylation detection were measured by Western blotting. The regulatory relations between AP-1 and decorin was assessed by luciferase reporter gene assay. Acute aortic dissection (AAD) mice model was constructed by feeding with β-aminopropionitrile monofumarate (BAPN). Haematoxylin and eosin (HE) and Mallory staining were performed for pathological analysis. In clinical aorta tissue of thoracic aortic dissection (TAD), the expression of SIRT1, activator protein 1 (AP-1) and decorin were in accordant trend. AP-1 expression which acts on Decorin promoter region is possibly regulated in a SIRT1-mediated deacetylation dependent manner. Resveratrol or SRT1720-initiated SIRT1 activation ameliorated BAPN-induced AAD symptoms accompanied by the activation of AP-1/decorin signaling and decorin-mediated programmed cell death 4 (PDCD4) expression by inhibiting miR-21 and miR-181b. These data suggest that SIRT1/AP-1/decorin signal cascades possibly play a part role in the process of AD. Our research demonstrate that activation of SIRT1 protects against AAD symptoms by enhancing AP-1-mediated decorin expression and downstream PDCD4 signaling pathway. Possibly, SIRT1 is served as a protective factor of AD and targeting SIRT1 therapy might be an attractive therapeutic approaches for AD treatment.

NOX1/NADPH oxidase in bone marrow-derived cells modulates intestinal barrier function

The involvement of reactive oxygen species (ROS) has been suggested in the development of inflammatory bowel disease (IBD). An impaired intestinal barrier function is common in IBD patients. Here, we report the central role of NOX1/NADPH oxidase, a major source of ROS in nonphagocytic cells, in intestinal barrier dysfunction. By in vivo imaging using L-012 as a probe, a time-dependent increase in ROS was demonstrated in the abdomen of wild-type mice (WT) administered lipopolysaccharide (LPS: 6 mg/kg i.p.), but it was almost completely abolished in mice deficient in Nox1 (Nox1-KO) or the inducible nitric oxide synthase gene (iNOS-KO). By ex vivo imaging, increased ROS production was mainly shown in the ileum, where enhanced immunostaining of NOX1 was observed on the apical side of the epithelium. On the other hand, a punctate staining pattern of 3-nitrotyrosine, a marker of peroxynitrite production, was demonstrated in the lamina propria. When LPS-induced intestinal hyperpermeability was assessed by the oral administration of fluorescein isothiocyanate-conjugated dextran (FD-4), it was significantly suppressed in Nox1-KO as well as iNOS-KO. When Nox1-KO adoptively transferred with WT bone marrow were treated with LPS, the serum level of FD-4 was significantly elevated, whereas it remained unchanged in WT receiving bone marrow derived from Nox1-KO. Concomitantly, the activation of matrix metalloproteinase-9 induced by LPS was alleviated not only in intestinal tissue but also in peritoneal macrophages of Nox1-KO. Up-regulation of iNOS by LPS was significantly inhibited in macrophages deficient in Nox1, illustrating a functional hierarchy in NOX1/iNOS signaling. Together, these findings suggest that NOX1 in bone marrow-derived cells, but not epithelial cells, perturbs intestinal barrier integrity during endotoxemia.

Characterization of Matrix Metalloprotease-9 Gene from Nile tilapia (Oreochromis niloticus) and Its High-Level Expression Induced by the Streptococcus agalactiae Challenge

The bacterial diseases of tilapia caused by Streptococcus agalactiae have resulted in the high mortality and huge economic loss in the tilapia industry. Matrix metalloproteinase-9 (MMP-9) may play an important role in fighting infection. However, the role of MMP-9 in Nile tilapia against S. agalactiae is still unclear. In this work, MMP-9 cDNA of Nile tilapia (NtMMP-9) has been cloned and characterized. NtMMP-9 has 2043 bp and encodes a putative protein of 680 amino acids. NtMMP-9 contains the conserved domains interacting with decorin and inhibitors via binding forces compared to those in other teleosts. Quantitative real-time-polymerase chain reaction (qPCR) analysis reveals that NtMMP-9 distinctly upregulated following S. agalactiae infection in a tissue- and time-dependent response pattern, and the tissues, including liver, spleen, and intestines, are the major organs against a S. agalactiae infection. Besides, the proteolytic activity of NtMMP-9 is also confirmed by heterologous expression and zymography, which proves the active function of NtMMP-9 interacting with other factors. The findings indicate that NtMMP-9 was involved in immune responses against the bacterial challenge at the transcriptional level. Further work will focus on the molecular mechanisms of NtMMP-9 to respond and modulate the signaling pathways in Nile tilapia against S. agalactiae invasion and the development of NtMMP-9-related predictive biomarkers or vaccines for preventing bacterial infection in the tilapia industry.

Diabetes and aortic aneurysm: current state of the art

Aortic aneurysm is a life-threatening disease due to the risk of aortic rupture. The only curative treatment available relies on surgical approaches; drug-based therapies are lacking, highlighting an unmet need for clinical practice. Abdominal aortic aneurysm (AAA) is frequently associated with atherosclerosis and cardiovascular risk factors including male sex, age, smoking, hypertension, and dyslipidaemia. Thoracic aortic aneurysm (TAA) is more often linked to genetic disorders of the extracellular matrix and the contractile apparatus but also share similar cardiovascular risk factors. Intriguingly, a large body of evidence points to an inverse association between diabetes and both AAA and TAA. A better understanding of the mechanisms underlying the negative association between diabetes and aortic aneurysm could help the development of innovative diagnostic and therapeutic approaches to tackle the disease. Here, we summarize current knowledge on the relationship between glycaemic parameters, diabetes, and the development of aortic aneurysm. Cellular and molecular pathways that underlie the protective effect of diabetes itself and its treatment are reviewed and discussed, along with their potential implications for clinical translation.

Functional Vascular Tissue Engineering Inspired by Matricellular Proteins

Modern regenerative medicine, and tissue engineering specifically, has benefited from a greater appreciation of the native extracellular matrix (ECM). Fibronectin, collagen, and elastin have entered the tissue engineer's toolkit; however, as fully decellularized biomaterials have come to the forefront in vascular engineering it has become apparent that the ECM is comprised of more than just fibronectin, collagen, and elastin, and that cell-instructive molecules known as matricellular proteins are critical for desired outcomes. In brief, matricellular proteins are ECM constituents that contrast with the canonical structural proteins of the ECM in that their primary role is to interact with the cell. Of late, matricellular genes have been linked to diseases including connective tissue disorders, cardiovascular disease, and cancer. Despite the range of biological activities, this class of biomolecules has not been actively used in the field of regenerative medicine. The intent of this review is to bring matricellular proteins into wider use in the context of vascular tissue engineering. Matricellular proteins orchestrate the formation of new collagen and elastin fibers that have proper mechanical properties-these will be essential components for a fully biological small diameter tissue engineered vascular graft (TEVG). Matricellular proteins also regulate the initiation of thrombosis via fibrin deposition and platelet activation, and the clearance of thrombus when it is no longer needed-proper regulation of thrombosis will be critical for maintaining patency of a TEVG after implantation. Matricellular proteins regulate the adhesion, migration, and proliferation of endothelial cells-all are biological functions that will be critical for formation of a thrombus-resistant endothelium within a TEVG. Lastly, matricellular proteins regulate the adhesion, migration, proliferation, and activation of smooth muscle cells-proper control of these biological activities will be critical for a TEVG that recellularizes and resists neointimal formation/stenosis. We review all of these functions for matricellular proteins here, in addition to reviewing the few studies that have been performed at the intersection of matricellular protein biology and vascular tissue engineering.

Recombinant Decorin Fusion Protein Attenuates Murine Abdominal Aortic Aneurysm Formation and Rupture

Decorin (DCN) is a small-leucine rich proteoglycan that mediates collagen fibrillogenesis, organization, and tensile strength. Adventitial DCN is reduced in abdominal aortic aneurysm (AAA) resulting in vessel wall instability thereby predisposing the vessel to rupture. Recombinant DCN fusion protein CAR-DCN was engineered with an extended C-terminus comprised of CAR homing peptide that recognizes inflamed blood vessels and penetrates deep into the vessel wall. In the present study, the role of systemically-administered CAR-DCN in AAA progression and rupture was assessed in a murine model. Apolipoprotein E knockout (ApoE-KO) mice were infused with angiotensin II (AngII) for 28 days to induce AAA formation. CAR-DCN or vehicle was administrated systemically until day 15. Mortality due to AAA rupture was significantly reduced in CAR-DCN-treated mice compared to controls. Although the prevalence of AAA was similar between vehicle and CAR-DCN groups, the severity of AAA in the CAR-DCN group was significantly reduced. Histological analysis revealed that CAR-DCN treatment significantly increased DCN and collagen levels within the aortic wall as compared to vehicle controls. Taken together, these results suggest that CAR-DCN treatment attenuates the formation and rupture of Ang II-induced AAA in mice by reinforcing the aortic wall.

Adventitial SCA-1+ Progenitor Cell Gene Sequencing Reveals the Mechanisms of Cell Migration in Response to Hyperlipidemia

Adventitial progenitor cells, including SCA-1⁺ and mesenchymal stem cells, are believed to be important in vascular remodeling. It has been shown that SCA-1⁺ progenitor cells are involved in neointimal hyperplasia of vein grafts, but little is known concerning their involvement in hyperlipidemia-induced atherosclerosis. We employed single-cell sequencing technology on primary adventitial mouse SCA-1⁺ cells from wild-type and atherosclerotic-prone (ApoE-deficient) mice and found that a group of genes controlling cell migration and matrix protein degradation was highly altered. Adventitial progenitors from ApoE-deficient mice displayed an augmented migratory potential both in vitro and in vivo. This increased migratory ability was mimicked by lipid loading to SCA-1⁺ cells. Furthermore, we show that lipid loading increased miRNA-29b expression and induced sirtuin-1 and matrix metalloproteinase-9 levels to promote cell migration. These results provide direct evidence that blood cholesterol levels influence vascular progenitor cell function, which could be a potential target cell for treatment of vascular disease.

Focal Adhesion Kinase Promotes the Progression of Aortic Aneurysm by Modulating Macrophage Behavior

OBJECTIVE

Abdominal aortic aneurysm (AAA) is a life-threatening vascular disease that is associated with persistent inflammation and extracellular matrix degradation. The molecular mechanisms underlying the macrophage-mediated progression of AAA remain largely unclear.

APPROACH AND RESULTS

We show that focal adhesion kinase (FAK) expression and activity are enhanced in macrophages that are recruited to AAA tissue. FAK potentiates tumor necrosis factor-α-induced secretion of matrix-degrading enzymes and chemokines by cultured macrophages. FAK also promotes macrophage chemotaxis. In mice, the administration of a FAK inhibitor that tempers local macrophage accumulation markedly suppresses the development and progression of chemically induced AAA.

CONCLUSIONS

FAK plays a key role in macrophage behavior, which underlies the chronic progression of AAA. These findings provide insights into AAA progression and identify FAK as a novel therapeutic target.

Co-transfection of decorin and interleukin-10 modulates pro-fibrotic extracellular matrix gene expression in human tenocyte culture

Extracellular matrix synthesis and remodelling are driven by increased activity of transforming growth factor beta 1 (TGF-β1). In tendon tissue repair, increased activity of TGF-β1 leads to progressive fibrosis. Decorin (DCN) and interleukin 10 (IL-10) antagonise pathological collagen synthesis by exerting a neutralising effect via downregulation of TGF-β1. Herein, we report that the delivery of DCN and IL-10 transgenes from a collagen hydrogel system supresses the constitutive expression of TGF-β1 and a range of pro-fibrotic extracellular matrix genes.