Smooth muscle cell-specific deletion of Col15a1 unexpectedly leads to impaired development of advanced atherosclerotic lesions

Protein glycosylation in cardiovascular health and disease

Protein glycosylation, which involves the attachment of carbohydrates to proteins, is one of the most abundant protein co-translational and post-translational modifications. Advances in technology have substantially increased our knowledge of the biosynthetic pathways involved in protein glycosylation, as well as how changes in glycosylation can affect cell function. In addition, our understanding of the role of protein glycosylation in disease processes is growing, particularly in the context of immune system function, infectious diseases, neurodegeneration and cancer. Several decades ago, cell surface glycoproteins were found to have an important role in regulating ion transport across the cardiac sarcolemma. However, with very few exceptions, our understanding of how changes in protein glycosylation influence cardiovascular (patho)physiology remains remarkably limited. Therefore, in this Review, we aim to provide an overview of N-linked and O-linked protein glycosylation, including intracellular O-linked N-acetylglucosamine protein modification. We discuss our current understanding of how all forms of protein glycosylation contribute to normal cardiovascular function and their roles in cardiovascular disease. Finally, we highlight potential gaps in our knowledge about the effects of protein glycosylation on the heart and vascular system, highlighting areas for future research.

miR-9 promotes canine endothelial-like cell migration by targeting COL15A1

BACKGROUND

Endothelial cell migration is the initial stage of angiogenesis. In previous studies, miR-9 has been found to regulate angiogenesis and cell migration in human medicine.

OBJECTIVES

This study aimed to reveal the regulatory effect of miR-9 on canine endothelial cell migration.

METHODS

Embryonic canine ventricle myocardium tissues were collected and induced to differentiate into endothelial-like cells (ELCs). A transwell and invasion assay were used to evaluate the impact of miR-9 on the migration capacity of ELCs, after which a luciferase reporter assay, western blotting, RNA sequencing and reverse transcription-polymerase chain reaction were conducted to explore the regulatory mechanism.

RESULTS

Our results showed that we successfully induced the primary cells derived from canine cardiac embryo tissues into ELCs. MiR-9 also promoted the migration and invasion of canine ELCs, and inhibited the expression of collagen XV, an angiogenic inhibitor, at the translational level by targeting the 3' untranslated region of COL15A1 gene. Furthermore, RNA sequencing showed that overexpression of miR-9 impacted several signalling pathways and eight genes involved in angiogenesis and cell migration in canine ELCs.

CONCLUSIONS

These findings suggest that miR-9 enhances the migration of canine ELCs and may serve as a potential diagnostic and therapeutic target for canine diseases involved in endothelial cells migration and angiogenesis, but more further studies are needed.

The Role of Hydrogen Sulfide in Plaque Stability

Atherosclerosis is the greatest contributor to cardiovascular events and is involved in the majority of deaths worldwide. Plaque rapture or erosion precipitates life-threatening thrombi, resulting in the obstruction blood flow to the heart (acute coronary syndrome), brain (ischemic stroke) or low extremities (peripheral vascular diseases). Among these events, major causation dues to the plaque rupture. Although the initiation, procession, and precise time of controlling plaque rupture are unclear, foam cell formation and apoptosis, cell death, extracellular matrix components, protease expression and activity, local inflammation, intraplaque hemorrhage, and calcification contribute to the plaque instability. These alterations tightly associate with the function regulation of intraplaque various cell populations. Hydrogen sulfide (H₂S) is gasotransmitter derived from methionine metabolism and exerts a protective role in the genesis of atherosclerosis. Recent progress also showed H₂S mediated the plaque stability. In this review, we discuss the progress of endogenous H₂S modulation on functions of vascular smooth muscle cells, monocytes/macrophages, and T cells, and the molecular mechanism in plaque stability.

Peptidylarginine deiminase 4 deficiency in bone marrow cells prevents plaque progression without decreasing atherogenic inflammation in apolipoprotein E-knockout mice

INTRODUCTION

Despite multiple studies in the past, the role of peptidylarginine deiminase 4 (PAD4) in atherosclerosis is currently insufficiently understood. In this regard, PAD4 deletion or inhibition of enzymatic activity was previously reported to ameliorate disease progression and inflammation. Besides, strong influence of neutrophil extracellular traps (NETs) on atherosclerosis burden has been proposed. Here, we studied the role of PAD4 for atherogenesis and plaque progression in a mouse model of atherosclerosis.

METHODS AND RESULTS

Lethally irradiated ApoE -/- mice were reconstituted with ApoE -/-/Pad4 -/- bone marrow cells and fed a high-fat diet (HFD) for 4 and 10 weeks, respectively. PAD4 deficiency did not prevent the development of atherosclerotic lesions after 4 weeks of HFD. However, after 10 weeks of HFD, mice with bone marrow cells-restricted PAD4 deficiency displayed significantly reduced lesion size, impaired lipid incorporation, decreased necrotic core area and less collagen when compared to ApoE -/- bone marrow-transplanted mice as demonstrated by histological staining. Moreover, flow cytometric analysis and quantitative real-time PCR revealed different macrophage subsets in atherosclerotic lesions and higher inflammatory response in these mice, as reflected by increased content of M1-like macrophages and upregulated aortic expression of the pro-inflammatory genes CCL2 and iNOS. Notably, diminished oxLDL uptake by in vitro-polarized M1-like macrophages was evidenced when compared to M2-like cells.

CONCLUSION

These results suggest that pharmacological inhibition of PAD4 may impede lipid accumulation and lesion progression despite no beneficial effects on vascular inflammation.

Dichotomous Roles of Smooth Muscle Cell-Derived MCP1 (Monocyte Chemoattractant Protein 1) in Development of Atherosclerosis

BACKGROUND

Smooth muscle cells (SMCs) in atherosclerotic plaque take on multiple nonclassical phenotypes that may affect plaque stability and, therefore, the likelihood of myocardial infarction or stroke. However, the mechanisms by which these cells affect stability are only beginning to be explored.

METHODS

In this study, we investigated the contribution of inflammatory MCP1 (monocyte chemoattractant protein 1) produced by both classical Myh11 (myosin heavy chain 11)⁺ SMCs and SMCs that have transitioned through an Lgals3 (galectin 3)⁺ state in atherosclerosis using smooth muscle lineage tracing mice that label all Myh11⁺ cells and a dual lineage tracing system that targets Lgals3-transitioned SMC only.

RESULTS

We show that loss of MCP1 in all Myh11⁺ smooth muscle results in a paradoxical increase in plaque size and macrophage content, driven by a baseline systemic monocytosis early in atherosclerosis pathogenesis. In contrast, knockout of MCP1 in Lgals3-transitioned SMCs using a complex dual lineage tracing system resulted in lesions with an increased Acta2 (actin alpha 2, smooth muscle)⁺ fibrous cap and decreased investment of Lgals3-transitioned SMCs, consistent with increased plaque stability. Finally, using flow cytometry and single-cell RNA sequencing, we show that MCP1 produced by Lgals3-transitioned SMCs influences multiple populations of inflammatory cells in late-stage plaques.

CONCLUSIONS

MCP1 produced by classical SMCs influences monocyte levels beginning early in disease and was atheroprotective, while MCP1 produced by the Lgals3-transitioned subset of SMCs exacerbated plaque pathogenesis in late-stage disease. Results are the first to determine the function of Lgals3-transitioned inflammatory SMCs in atherosclerosis and highlight the need for caution when considering therapeutic interventions involving MCP1.

Endothelial OCT4 is atheroprotective by preventing metabolic and phenotypic dysfunction

AIMS

Until recently, the pluripotency factor Octamer (ATGCAAAT)-binding transcriptional factor 4 (OCT4) was believed to be dispensable in adult somatic cells. However, our recent studies provided clear evidence that OCT4 has a critical atheroprotective role in smooth muscle cells. Here, we asked if OCT4 might play a functional role in regulating endothelial cell (EC) phenotypic modulations in atherosclerosis.

METHODS AND RESULTS

Specifically, we show that EC-specific Oct4 knockout resulted in increased lipid, LGALS3+ cell accumulation, and altered plaque characteristics consistent with decreased plaque stability. A combination of single-cell RNA sequencing and EC-lineage-tracing studies revealed increased EC activation, endothelial-to-mesenchymal transitions, plaque neovascularization, and mitochondrial dysfunction in the absence of OCT4. Furthermore, we show that the adenosine triphosphate (ATP) transporter, ATP-binding cassette (ABC) transporter G2 (ABCG2), is a direct target of OCT4 in EC and establish for the first time that the OCT4/ABCG2 axis maintains EC metabolic homeostasis by regulating intracellular heme accumulation and related reactive oxygen species production, which, in turn, contributes to atherogenesis.

CONCLUSIONS

These results provide the first direct evidence that OCT4 has a protective metabolic function in EC and identifies vascular OCT4 and its signalling axis as a potential target for novel therapeutics.

Plaque-targeted, proteolysis-resistant, activatable and MRI-visible nano-GLP-1 receptor agonist targets smooth muscle cell differentiation in atherosclerosis

Background: Glucagon-like peptide-1 receptor (GLP-1R) agonists are powerful glycemia-lowering agents, which have systematically been shown to lower cardiovascular events and mortality. These beneficial effects were difficult to pinpoint within atherosclerotic plaque due to lack of particular specificity of such agonists to the vascular cells and an inadequate understanding of the GLP-1R expression in atherosclerosis. Here, we hypothesized that the direct engagement of the GLP-1R in atherosclerosis by targeted agonists will alleviate vascular inflammation and plaque burden, even at a very low dose. Methods: The expression of GLP-1 receptor (GLP-1R, Glp1r mRNA) in human lesions with pathologic intimal thickening, Apoe-/- mouse atheroma and cultured immune/non-immune cells was investigated using genetic lineage tracing, Southern blotting and validated antisera against human GLP-1R. Protease-resistant and "activatable" nanoparticles (NPs) carrying GLP-1R agonist liraglutide (GlpNP) were engineered and synthesized. Inclusion of gadolinium chelates into GlpNP allowed for imaging by MRI. Atherosclerotic Apoe-/- mice were treated intravenously with a single dose (30 µg/kg of liraglutide) or chronically (1 µg/kg, 6 weeks, 2x/week) with GlpNP, liraglutide or control NPs, followed by assessment of metabolic parameters, atheroma burden, inflammation and vascular function. Results: Humal plaque specimens expressed high levels of GLP-1R within the locus of de-differentiated smooth muscle cells that also expressed myeloid marker CD68. However, innate immune cells under a variety of conditions expressed very low levels of Glp1r, as seen in lineage tracing and Southern blotting experiments examining full-length open reading frame mRNA transcripts. Importantly, de-differentiated vascular smooth muscle cells demonstrated significant Glp1r expression levels, suggesting that these could represent the cells with predominant Glp1r-positivity in atherosclerosis. GlpNP resisted proteolysis and demonstrated biological activity including in vivo glycemia lowering at 30 µg/kg and in vitro cholesterol efflux. Activatable properties of GlpNP were confirmed in vitro by imaging cytometry and in vivo using whole organ imaging. GlpNP targeted CD11b+/CD11c+ cells in circulation and smooth muscle cells in aortic plaque in Apoe-/- mice when assessed by MRI and fluorescence imaging. At a very low dose of 1 µg/kg, previously known to have little effect on glycemia and weight loss, GlpNP delivered i.v. for six weeks reduced triglyceride-rich lipoproteins in plasma, plaque burden and plaque cholesterol without significant effects on weight, glycemia and plasma cholesterol levels. Conclusions: GlpNP improves atherosclerosis at weight-neutral doses as low as 1 µg/kg with the effects independent from the pancreas or the central nervous system. Our study underlines the importance of direct actions of GLP-1 analogs on atherosclerosis, involving cholesterol efflux and inflammation. Our findings are the first to suggest the therapeutic modulation of vascular targets by GlpNP, especially in the context of smooth muscle cell inflammation.

Evaluation of the Usefulness of Human Adipose-Derived Stem Cell Spheroids Formed Using SphereRing® and the Lethal Damage Sensitivity to Synovial Fluid In Vitro

Osteoarthritis (OA) is an irreversible degenerative condition causing bone deformation in the joints and articular cartilage degeneration with chronic pain and impaired movement. Adipose-derived stem cell (ADSC) or crushed adipose tissue injection into the joint cavity reportedly improve knee function and symptoms, including pain. Stem cell spheroids may be promising treatment options due to their anti-inflammatory and enhanced tissue regeneration/repair effects. Herein, to form human ADSC spheroids, we used first SphereRing® (Fukoku Co., Ltd., Ageo, Japan), a newly developed rotating donut-shaped tube and determined their characteristics by DNA microarray of mRNA analysis. The variable gene expression cluster was then identified and validated by RT-PCR. Gene expression fluctuations were observed, such as COL15A1 and ANGPTL2, related to vascular endothelial cells and angiogenesis, and TNC, involved in tissue formation. In addition, multiplex cytokine analysis in the medium revealed significant cytokines and growth factors production increase of IL-6, IL-10, etc. However, ADSC administration into the joint cavity involves their contact with the synovial fluid (SF). Therefore, we examined how SF collected from OA patient joint cavities affect 2D-culture ADSCs and ADSC spheroids and observed SF induced cell death. ADSC spheroids could become promising OA treatment options, although studying the administration methods and consider their interaction with SF is essential.

Effects of semaglutide on vascular structure and proteomics in high-fat diet-induced obese mice

BACKGROUND

Obesity is a chronic metabolic disease caused by a combination of genetic and environmental factors. To determine whether semaglutide could improve aortic injury in obese C57BL/6J mice, and further explore its molecular mechanism of action using proteomics.

METHODS

24 C57BL/6J male mice were randomly divided into normal diet group (NCD group), high-fat diet group (HFD group) and high-fat diet + semaglutide group (Sema group, semaglutide (30 nmol/kg/d) for 12 weeks). The serum samples were collected from mice to detect blood glucose, insulin and blood lipid concentrations. Aortic stiffness was detected by Doppler pulse wave velocity (PWV). Changes in vascular structure were detected by HE, masson, EVG staining and electron microscopy. The aorta-related protein expression profiles were detected by proteomic techniques, and proteins with potential molecular mechanisms were identified.

RESULTS

Semaglutide could reduce body weight, the concentrations of blood glucose, total cholesterol (TC), triglycerides (TG), lipoprotein cholesterol (LDL-C), and reduce the aortic PWV and ameliorate vascular damage in obese mice. The results of proteomic analysis showed there were 537 up-regulated differentially expressed proteins (DEPs) and 322 down-regulated DEPs in NCD/HFD group, 251 up-regulated DEPs and 237 down-regulated proteins in HFD/Sema group. There were a total of 25 meaningful overlapping DEPs in the NCD/HFD and HFD/Sema groups. GO enrichment analysis of overlapping DEPs found that these differential proteins were mainly located in the signaling pathways of the extracellular matrix. The most obvious changes of extracellular matrix associated proteins in the three experimental groups were Coll5a1, Lama4, Sparc.

CONCLUSION

Semaglutide may protect vascular structure and improve endothelial permeability by reducing the levels of Coll5a1, Lama4, Sparc in extracellular matrix, so as to improve vascular function and achieve vascular protection.

SMC-Derived Hyaluronan Modulates Vascular SMC Phenotype in Murine Atherosclerosis

[Figure: see text].

Construction of a DLBCL Prognostic Signature Based on Tumor Microenvironment

BACKGROUNDS

Diffuse large B-cell lymphoma (DLBCL) is a common curable non-Hodgkin's lymphoma. Patients with this disease can be cured after the R-CHOP immunochemotherapy (rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisone). Nonetheless, most cured patients will relapse again and have dismal prognosis. In this study, we aim to identify a potential biomarker by analyzing gene expression data, and to predict patient's survival rate by constructing a risk model.

METHODS

Firstly, mRNA chip data (GSE87371) and clinical data of DLBCL patients were obtained from Gene Expression Omnibus (GEO). Samples were scored with estimate package. The obtained stromal score (P < 0.05) and ESTIMATE score (P < 0.05) were significantly correlated with the prognosis. Differentially expressed genes (DEGs) screened through the above two scoring methods were intersected and 279 DEGs were obtained. Next, five feature genes (CD163, CLEC4A, COL15A1, GABRB2, IFIT3) were identified by univariate Cox, LASSO and multivariate Cox regression analyses to establish a risk evaluation model. Thereafter, the 5-gene risk model was validated on a validation set. ROC and survival analyses were performed to assess the performance of the model.

RESULTS

Further analysis showed that the risk model was capable of independently determining the prognosis of patients, and a nomogram was sequentially established.

CONCLUSIONS

Authors screened DEGs related to ESTIMATE and stromal scores from GEO database, and established a 5-gene prognostic signature through Cox regression analysis and LASSO analysis. The risk model and nomogram will help individuals accurately predict the prognosis of DLBCL patients.

Multiple cell types contribute to the atherosclerotic lesion fibrous cap by PDGFRβ and bioenergetic mechanisms

Stable atherosclerotic plaques are characterized by a thick, extracellular matrix-rich fibrous cap populated by protective ACTA2⁺ myofibroblast (MF)-like cells, assumed to be almost exclusively derived from smooth muscle cells (SMCs). Herein, we show that in murine and human lesions, 20% to 40% of ACTA2⁺ fibrous cap cells, respectively, are derived from non-SMC sources, including endothelial cells (ECs) or macrophages that have undergone an endothelial-to-mesenchymal transition (EndoMT) or a macrophage-to-mesenchymal transition (MMT). In addition, we show that SMC-specific knockout of the Pdgfrb gene, which encodes platelet-derived growth factor receptor beta (PDGFRβ), in Apoe^-/- mice fed a Western diet for 18 weeks resulted in brachiocephalic artery lesions nearly devoid of SMCs but with no changes in lesion size, remodelling or indices of stability, including the percentage of ACTA2⁺ fibrous cap cells. However, prolonged Western diet feeding of SMC Pdgfrb-knockout mice resulted in reduced indices of stability, indicating that EndoMT- and MMT-derived MFs cannot compensate indefinitely for loss of SMC-derived MFs. Using single-cell and bulk RNA-sequencing analyses of the brachiocephalic artery region and in vitro models, we provide evidence that SMC-to-MF transitions are induced by PDGF and transforming growth factor-β and dependent on aerobic glycolysis, while EndoMT is induced by interleukin-1β and transforming growth factor-β. Together, we provide evidence that the ACTA2⁺ fibrous cap originates from a tapestry of cell types, which transition to an MF-like state through distinct signalling pathways that are either dependent on or associated with extensive metabolic reprogramming.

Targeting inflammation in atherosclerosis - from experimental insights to the clinic

Atherosclerosis, a dominant and growing cause of death and disability worldwide, involves inflammation from its inception to the emergence of complications. Targeting inflammatory pathways could therefore provide a promising new avenue to prevent and treat atherosclerosis. Indeed, clinical studies have now demonstrated unequivocally that modulation of inflammation can forestall the clinical complications of atherosclerosis. This progress pinpoints the need for preclinical investigations to refine strategies for combatting inflammation in the human disease. In this Review, we consider a gamut of attractive possibilities for modifying inflammation in atherosclerosis, including targeting pivotal inflammatory pathways such as the inflammasomes, inhibiting cytokines, manipulating adaptive immunity and promoting pro-resolution mechanisms. Along with lifestyle measures, pharmacological interventions to mute inflammation could complement traditional targets, such as lipids and hypertension, to make new inroads into the management of atherosclerotic risk.

Reactive Oxygen Species and Oxidative Stress in the Pathogenesis and Progression of Genetic Diseases of the Connective Tissue

Connective tissue is known to provide structural and functional “glue” properties to other tissues. It contains cellular and molecular components that are arranged in several dynamic organizations. Connective tissue is the focus of numerous genetic and nongenetic diseases. Genetic diseases of the connective tissue are minority or rare, but no less important than the nongenetic diseases. Here we review the impact of reactive oxygen species (ROS) and oxidative stress on the onset and/or progression of diseases that directly affect connective tissue and have a genetic origin. It is important to consider that ROS and oxidative stress are not synonymous, although they are often closely linked. In a normal range, ROS have a relevant physiological role, whose levels result from a fine balance between ROS producers and ROS scavenge enzymatic systems. However, pathology arises or worsens when such balance is lost, like when ROS production is abnormally and constantly high and/or when ROS scavenge (enzymatic) systems are impaired. These concepts apply to numerous diseases, and connective tissue is no exception. We have organized this review around the two basic structural molecular components of connective tissue: The ground substance and fibers (collagen and elastic fibers).

Exosome-Mediated Transfer of Anti-miR-33a-5p from Transduced Endothelial Cells Enhances Macrophage and Vascular Smooth Muscle Cell Cholesterol Efflux

Atherosclerosis is a disease of large- and medium-sized arteries that is caused by cholesterol accumulation in arterial intimal cells, including macrophages and smooth muscle cells (SMC). Cholesterol accumulation in these cells can be prevented or reversed in preclinical models-and atherosclerosis reduced-by transgenesis that increases expression of molecules that control cholesterol efflux, including apolipoprotein AI (apoAI) and ATP-binding cassette subfamily A, member 1 (ABCA1). In a previous work, we showed that transduction of arterial endothelial cells (EC)-with a helper-dependent adenovirus (HDAd) expressing apoAI-enhanced EC cholesterol efflux in vitro and decreased atherosclerosis in vivo. Similarly, overexpression of ABCA1 in cultured EC increased cholesterol efflux and decreased inflammatory gene expression. These EC-targeted gene-therapy strategies might be improved by concurrent upregulation of cholesterol-efflux pathways in other intimal cell types. Here, we report modification of this strategy to enable delivery of therapeutic nucleic acids to cells of the sub-endothelium. We constructed an HDAd (HDAdXMoAntimiR33a5p) that expresses an antagomiR directed at miR-33a-5p (a microRNA that suppresses cholesterol efflux by silencing ABCA1). HDAdXMoAntimiR33a5p contains a sequence motif that enhances uptake of anti-miR-33a-5p into exosomes. Cultured EC release exosomes containing small RNA, including miR-33a-5p. After transduction with HDAdXMoAntimiR33a5p, EC-derived exosomes containing anti-miR-33a-5p accumulate in conditioned medium (CM). When this CM is added to macrophages or SMC, anti-miR-33a-5p is detected in these target cells. Exosome-mediated transfer of anti-miR-33a-5p reduces miR-33a-5p by ∼65-80%, increases ABCA1 protein by 1.6-2.2-fold, and increases apoAI-mediated cholesterol efflux by 1.4-1.6-fold (all p ≤ 0.01). These effects were absent in macrophages and SMC incubated in exosome-depleted CM. EC transduced with HDAdXMoAntimiR33a5p release exosomes that can transfer anti-miR-33a-5p to other intimal cell types, upregulating cholesterol efflux from these cells. This strategy provides a platform for genetic modification of intimal and medial cells, using a vector that transduces only EC.

Collagen XV, a multifaceted multiplexin present across tissues and species

Type XV collagen is a non-fibrillar collagen that is associated with basement membranes and belongs to the multiplexin subset of the collagen superfamily. Collagen XV was initially studied because of its sequence homology with collagen XVIII/endostatin whose anti-angiogenic and anti-tumorigenic properties were subjects of wide interest in the past years. But during the last fifteen years, collagen XV has gained growing attention with increasing number of studies that have attributed new functions to this widely distributed collagen/proteoglycan hybrid molecule. Despite the cumulative evidence of its functional pleiotropy and its evolutionary conserved function, no review compiling the current state of the art about collagen XV is currently available. Here, we thus provide the first comprehensive view of the knowledge gathered so far on the molecular structure, tissue distribution and functions of collagen XV in development, tissue homeostasis and disease with an evolutionary perspective. We hope that our review will open new roads for promising research on collagen XV in the coming years.

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Type XV collagen belongs to the multiplexin subset of the collagen superfamily.

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It is evolutionarily conserved collagen and associated with basement membranes.

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This collagen/proteoglycan hybrid molecule contains an anti-angiogenic restin domain.

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It has important functions in the cardiovascular and the neuromuscular systems.

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Its expression is dysregulated in various diseases including cancers.

Novel Autoimmune IgM Antibody Attenuates Atherosclerosis in IgM Deficient Low-Fat Diet-Fed, but Not Western Diet-Fed Apoe-/- Mice

OBJECTIVE

Oxidized phospholipids (OxPL), such as the oxidized derivatives of 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphorylcholine, 1-palmitoyl-2-(5-oxovaleroyl)-sn-glycero-3-phosphorylcholine, and 1-palmitoyl-2-glutaroyl-sn-glycero-3-phosphorylcholine, have been shown to be the principal biologically active components of minimally oxidized LDL (low-density lipoprotein). The role of OxPL in cardiovascular diseases is well recognized, including activation of inflammation within vascular cells. Atherosclerotic Apoe-/- mice fed a high-fat diet develop antibodies to OxPL, and hybridoma B-cell lines producing natural anti-OxPL autoantibodies have been successfully generated and characterized. However, as yet, no studies have been reported demonstrating that treatment with OxPL neutralizing antibodies can be used to prevent or reverse advanced atherosclerosis. Approach and Results: Here, using a screening against 1-palmitoyl-2-(5-oxovaleroyl)-sn-glycero-3-phosphorylcholine/1-palmitoyl-2-glutaroyl-sn-glycero-3-phosphorylcholine, we generated a novel IgM autoantibody, 10C12, from the spleens of Apoe-/- mice fed a long-term Western diet, that demonstrated potent OxPL neutralizing activity in vitro and the ability to inhibit macrophage accumulation within arteries of Apoe-/- mice fed a Western diet for 4 weeks. Of interest, 10C12 failed to inhibit atherosclerosis progression in Apoe-/- mice treated between 18 and 26 weeks of Western diet feeding likely due at least in part to high levels of endogenous anti-OxPL antibodies. However, 10C12 treatment caused a 40% decrease in lipid accumulation within aortas of secreted IgM deficient, sIgM-/-Apoe-/-, mice fed a low-fat diet, when the antibody was administrated between 32-40 weeks of age.

CONCLUSIONS

Taken together, these results provide direct evidence showing that treatment with a single autoimmune anti-OxPL IgM antibody during advanced disease stages can have an atheroprotective outcome.

Vascular smooth muscle cells in atherosclerosis

Vascular smooth muscle cells (VSMCs) are a major cell type present at all stages of an atherosclerotic plaque. According to the 'response to injury' and 'vulnerable plaque' hypotheses, contractile VSMCs recruited from the media undergo phenotypic conversion to proliferative synthetic cells that generate extracellular matrix to form the fibrous cap and hence stabilize plaques. However, lineage-tracing studies have highlighted flaws in the interpretation of former studies, revealing that these studies had underestimated both the content and functions of VSMCs in plaques and have thus challenged our view on the role of VSMCs in atherosclerosis. VSMCs are more plastic than previously recognized and can adopt alternative phenotypes, including phenotypes resembling foam cells, macrophages, mesenchymal stem cells and osteochondrogenic cells, which could contribute both positively and negatively to disease progression. In this Review, we present the evidence for VSMC plasticity and summarize the roles of VSMCs and VSMC-derived cells in atherosclerotic plaque development and progression. Correct attribution and spatiotemporal resolution of clinically beneficial and detrimental processes will underpin the success of any therapeutic intervention aimed at VSMCs and their derivatives.

The role of smooth muscle cells in plaque stability: Therapeutic targeting potential

Events responsible for cardiovascular mortality and morbidity are predominantly caused by rupture of "vulnerable" atherosclerotic lesions. Vascular smooth muscle cells (VSMCs) play a key role in atherogenesis and have historically been considered beneficial for plaque stability. VSMCs constitute the main cellular component of the protective fibrous cap within lesions and are responsible for synthesising strength-giving extracellular matrix components. However, lineage-tracing experiments in mouse models of atherosclerosis have shown that, in addition to the fibrous cap, VSMCs also give rise to many of the cell types found within the plaque core. In particular, VSMCs generate a substantial fraction of lipid-laden foam cells, and VSMC-derived cells expressing markers of macrophages, osteochondrocyte, and mesenchymal stem cells have been observed within lesions. Here, we review recent studies that have changed our perspective on VSMC function in atherosclerosis and discuss how VSMCs could be targeted to increase plaque stability.

Exploring the roles of MACIT and multiplexin collagens in stem cells and cancer

The extracellular matrix (ECM) is ubiquitously involved in neoplastic transformation, tumour growth and metastatic dissemination, and the interplay between tumour and stromal cells and the ECM is now considered crucial for the formation of a tumour-supporting microenvironment. The 28 different collagens (Col) form a major ECM protein family and display extraordinary functional diversity in tissue homeostasis as well as in pathological conditions, with functions ranging from structural support for tissues to regulatory binding activities and storage of biologically active cryptic domains releasable through ECM proteolysis. Two subfamilies of collagens, namely the plasma membrane-associated collagens with interrupted triple-helices (MACITs, including ColXIII, ColXXIII and ColXXV) and the basement membrane-associated collagens with multiple triple-helix domains with interruptions (multiplexins, including ColXV and ColXVIII), have highly interesting regulatory functions in tissue and organ development, as well as in various diseases, including cancer. An increasing, albeit yet sparse, data suggest that these collagens play crucial roles in conveying regulatory signals from the extracellular space to cells. We summarize here the current knowledge about MACITs and multiplexins as regulators of stemness and oncogenic processes, as well as their roles in influencing cell fate decisions in healthy and cancerous tissues. In addition, we present a bioinformatic analysis of the impacts of MACITs and multiplexins transcript levels on the prognosis of patients representing a wide array of malignant diseases, to aid future diagnostic and therapeutic efforts.

Quantitative Analysis of Cellular Composition in Advanced Atherosclerotic Lesions of Smooth Muscle Cell Lineage-Tracing Mice

Atherosclerosis remains the leading cause of death worldwide and, despite countless preclinical studies describing promising therapeutic targets, novel interventions have remained elusive. This is likely due, in part, to a reliance on preclinical prevention models investigating the effects of genetic manipulations or pharmacological treatments on atherosclerosis development rather than the established disease. Also, results of these studies are often confounding because of the use of superficial lesion analyses and a lack of characterization of lesion cell populations. To help overcome these translational hurdles, we propose an increased reliance on intervention models that employ investigation of changes in cellular composition at a single cell level by immunofluorescent staining and confocal microscopy. To this end, we describe a protocol for testing a putative therapeutic agent in a murine intervention model including a systematic approach for animal dissection, embedding, sectioning, staining, and quantification of brachiocephalic artery lesions. In addition, due to the phenotypic diversity of cells within late-stage atherosclerotic lesions, we describe the importance of using cell-specific, inducible lineage tracing mouse systems and how this can be leveraged for unbiased characterization of atherosclerotic lesion cell populations. Together, these strategies may assist vascular biologists to more accurately model therapeutic interventions and analyze atherosclerotic disease and will hopefully translate into a higher rate of success in clinical trials.

Cell Type-Specific Roles of NF-κB Linking Inflammation and Thrombosis

The transcription factor NF-κB is a central mediator of inflammation with multiple links to thrombotic processes. In this review, we focus on the role of NF-κB signaling in cell types within the vasculature and the circulation that are involved in thrombo-inflammatory processes. All these cells express NF-κB, which mediates important functions in cellular interactions, cell survival and differentiation, as well as expression of cytokines, chemokines, and coagulation factors. Even platelets, as anucleated cells, contain NF-κB family members and their corresponding signaling molecules, which are involved in platelet activation, as well as secondary feedback circuits. The response of endothelial cells to inflammation and NF-κB activation is characterized by the induction of adhesion molecules promoting binding and transmigration of leukocytes, while simultaneously increasing their thrombogenic potential. Paracrine signaling from endothelial cells activates NF-κB in vascular smooth muscle cells and causes a phenotypic switch to a “synthetic” state associated with a decrease in contractile proteins. Monocytes react to inflammatory situations with enforced expression of tissue factor and after differentiation to macrophages with altered polarization. Neutrophils respond with an extension of their life span—and upon full activation they can expel their DNA thereby forming so-called neutrophil extracellular traps (NETs), which exert antibacterial functions, but also induce a strong coagulatory response. This may cause formation of microthrombi that are important for the immobilization of pathogens, a process designated as immunothrombosis. However, deregulation of the complex cellular links between inflammation and thrombosis by unrestrained NET formation or the loss of the endothelial layer due to mechanical rupture or erosion can result in rapid activation and aggregation of platelets and the manifestation of thrombo-inflammatory diseases. Sepsis is an important example of such a disorder caused by a dysregulated host response to infection finally leading to severe coagulopathies. NF-κB is critically involved in these pathophysiological processes as it induces both inflammatory and thrombotic responses.

Redox control of vascular smooth muscle cell function and plasticity

Vascular smooth muscle cells (SMC) play a major role in vascular diseases, such as atherosclerosis and hypertension. It has long been established in vitro that contractile SMC can phenotypically switch to function as proliferative and/or migratory cells in response to stimulation by oxidative stress, growth factors, and inflammatory cytokines. Reactive oxygen species (ROS) are oxidative stressors implicated in driving vascular diseases, shifting cell bioenergetics, and increasing SMC proliferation, migration, and apoptosis. In this review, we summarize our current knowledge of how disruptions to redox balance can functionally change SMC and how this may influence vascular disease pathogenesis. Specifically, we focus on our current understanding of the role of vascular nicotinamide adenine dinucleotide phosphate (NADPH) oxidases (NOX) 1, 4, and 5 in SMC function. We also review the evidence implicating mitochondrial fission in SMC phenotypic transitions and mitochondrial fusion in maintenance of SMC homeostasis. Finally, we discuss the importance of the redox regulation of the soluble guanylate cyclase (sGC)-cyclic guanosine monophosphate (cGMP)-protein kinase G (PKG) pathway as a potential oxidative and therapeutic target for regulating SMC function.

Irradiation abolishes smooth muscle investment into vascular lesions in specific vascular beds

The long-term adverse effects of radiotherapy on cardiovascular disease are well documented. However, the underlying mechanisms responsible for this increased risk are poorly understood. Previous studies using rigorous smooth muscle cell (SMC) lineage tracing have shown abundant SMC investment into atherosclerotic lesions, where SMCs contribute to the formation of a protective fibrous cap. Studies herein tested whether radiation impairs protective adaptive SMC responses during vascular disease. To do this, we exposed SMC lineage tracing (Myh11-ERT2Cre YFP+) mice to lethal radiation (1,200 cGy) followed by bone marrow transplantation prior to atherosclerosis development or vessel injury. Surprisingly, following irradiation, we observed a complete loss of SMC investment in 100% of brachiocephalic artery (BCA), carotid artery, and aortic arch lesions. Importantly, this was associated with a decrease in multiple indices of atherosclerotic lesion stability within the BCA. Interestingly, we observed anatomic heterogeneity, as SMCs accumulated normally into lesions of the aortic root and abdominal aorta, suggesting that SMC sensitivity to lethal irradiation occurs in blood vessels of neural crest origin. Taken together, these results reveal an undefined and unintended variable in previous studies using lethal irradiation and may help explain why patients exposed to radiation have increased risk for cardiovascular disease.

Statistical considerations in reporting cardiovascular research

The problem of inadequate statistical reporting is long standing and widespread in the biomedical literature, including in cardiovascular physiology. Although guidelines for reporting statistics have been available in clinical medicine for some time, there are currently no guidelines specific to cardiovascular physiology. To assess the need for guidelines, we determined the type and frequency of statistical tests and procedures currently used in the American Journal of Physiology-Heart and Circulatory Physiology. A PubMed search for articles published in the American Journal of Physiology-Heart and Circulatory Physiology between January 1, 2017, and October 6, 2017, provided a final sample of 146 articles evaluated for methods used and 38 articles for indepth analysis. The t-test and ANOVA accounted for 71% (212 of 300 articles) of the statistical tests performed. Of six categories of post hoc tests, Bonferroni and Tukey tests were used in 63% (62 of 98 articles). There was an overall lack in details provided by authors publishing in the American Journal of Physiology-Heart and Circulatory Physiology, and we compiled a list of recommended minimum reporting guidelines to aid authors in preparing manuscripts. Following these guidelines could substantially improve the quality of statistical reports and enhance data rigor and reproducibility.

Guidelines for authors and reviewers on antibody use in physiology studies

Antibody use is a critical component of cardiovascular physiology research, and antibodies are used to monitor protein abundance (immunoblot analysis) and protein expression and localization (in tissue by immunohistochemistry and in cells by immunocytochemistry). With ongoing discussions on how to improve reproducibility and rigor, the goal of this review is to provide best practice guidelines regarding how to optimize antibody use for increased rigor and reproducibility in both immunoblot analysis and immunohistochemistry approaches.

Listen to this article’s corresponding podcast at http://ajpheart.podbean.com/e/guidelines-on-antibody-use-in-physiology-studies/.