Wijnand den Dekker

First experience in humans using adipose tissue-derived regenerative cells in the treatment of patients with ST-segment elevation myocardial infarction.

To the Editor: In preclinical animal models of acute myocardial infarction (AMI), administration of freshly isolated adipose tissue–derived regenerative cells (ADRCs) immediately after the AMI improved left ventricular (LV) function and myocardial perfusion ([1,2][1]). The predominant working

Toll like receptor 4 in atherosclerosis and plaque destabilization

The immune system plays a pivotal role in initiation and progression of atherosclerosis. Monocytes and T-lymphocytes are the first cells to enter the damaged endothelium. Differentiation of monocytes into macrophages and ingestion of lipids by these macrophages turning them into foam cells is a crucial step in the development of a fatty streak, the first sign of atherosclerosis. In recent years there has been accumulating evidence for the involvement of Toll like receptor 4, a pattern recognition receptor of the innate immune system, in the pathogenesis of atherosclerosis. Different cell types present in the atherosclerotic plaque express TLR4 and several pro-atherogenic ligands have been shown to activate TLR4. The innate immune system and the TLR signaling cascade may play an important role not only in the pathogenesis of atherosclerosis, but also in plaque destabilization. In this review, we discuss the role of TLR4 in the pathogenesis of atherosclerosis and vulnerable plaque development.

Endothelial Cell–Specific FGD5 Involvement in Vascular Pruning Defines Neovessel Fate in Mice

Background— New vessel formation contributes to organ development during embryogenesis and tissue repair in response to mechanical damage, inflammation, and ischemia in adult organisms. Early angiogenesis includes formation of an excessive primitive network that needs to be reorganized into a secondary vascular network with higher hierarchical structure. Vascular pruning, the removal of aberrant neovessels by apoptosis, is a vital step in this process. Although multiple molecular pathways for early angiogenesis have been identified, little is known about the genetic regulators of secondary network development. Methods and Results— Using a transcriptomics approach, we identified a new endothelial specific gene named FYVE, RhoGEF, and PH domain–containing 5 (FGD5) that plays a crucial role in vascular pruning. Loss- and gain-of-function studies demonstrate that FGD5 inhibits neovascularization, indicated by in vitro tube-formation, aortic-ring, and coated-bead assays and by in vivo coated-bead plug assays and studies in the murine retina model. FGD5 promotes apoptosis-induced vaso-obliteration via induction of the hey1-p53 pathway by direct binding and activation of cdc42. Indeed, FGD5 correlates with apoptosis in endothelial cells during vascular remodeling and was linked to rising p21CIP1 levels in aging mice. Conclusion— We have identified FGD5 as a novel genetic regulator of vascular pruning by activation of endothelial cell–targeted apoptosis.

Mast Cells Induce Vascular Smooth Muscle Cell Apoptosis via a Toll-Like Receptor 4 Activation Pathway

Objective—Activated mast cells (MCs) release chymase, which can induce vascular smooth muscle cell (VSMC) apoptosis leading to plaque destabilization. Because the mechanism through which MCs release chymase in atherosclerosis is unknown, we studied whether MC-associated VSMC apoptosis is regulated by toll-like receptor 4 (TLR4) signaling. Methods and Results—Local recruitment and activation of MCs reduced VSMC content specifically in the cap region of vulnerable plaques in apolipoprotein E knockout mice. Cotreatment with the TLR4 antagonist Bartonella quintana lipopolysaccharide prevented this VSMC loss, suggesting an important role for TLR4 signaling in MC-induced VSMC apoptosis. Coculture of VSMCs with MCs activated by the TLR4 agonist Escherichia coli lipopolysaccharide increased VSMC apoptosis. Apoptosis was inhibited by TLR4 and chymase blockers, indicating that TLR4 signaling is involved in chymase release in MCs. This pathway was mediated via interleukin-6 because interleukin-6 promoted MC-associated VSMC apoptosis, which was inhibited by blocking chymase release. In addition, TLR4 activation in MCs induced interleukin-6 production, which was reduced by preincubation with either B. quintana lipopolysaccharide or an anti-TLR4 antibody. Conclusion—We show that MCs promote VSMC apoptosis in vivo. In addition, TLR4 signaling is important in chymase release in MCs and, therefore, in plaque destabilization by regulating VSMC apoptosis.

Ets2 Determines the Inflammatory State of Endothelial Cells in Advanced Atherosclerotic Lesions

Rationale: Neovascularization is required for embryonic development and plays a central role in diseases in adults. In atherosclerosis, the role of neovascularization remains to be elucidated. In a genome-wide microarray-screen of Flk1+ angioblasts during murine embryogenesis, the v-ets erythroblastosis virus E26 oncogene homolog 2 (Ets2) transcription factor was identified as a potential angiogenic factor. Objectives: We assessed the role of Ets2 in endothelial cells during atherosclerotic lesion progression toward plaque instability. Methods and Results: In 91 patients treated for carotid artery disease, Ets2 levels showed modest correlations with capillary growth, thrombogenicity, and rising levels of tumor necrosis factor-&agr; (TNF&agr;), monocyte chemoattractant protein 1, and interleukin-6 in the atherosclerotic lesions. Experiments in ApoE−/− mice, using a vulnerable plaque model, showed that Ets2 expression was increased under atherogenic conditions and was augmented specifically in the vulnerable versus stable lesions. In endothelial cell cultures, Ets2 expression and activation was responsive to the atherogenic cytokine TNF&agr;. In the murine vulnerable plaque model, overexpression of Ets2 promoted lesion growth with neovessel formation, hemorrhaging, and plaque destabilization. In contrast, Ets2 silencing, using a lentiviral shRNA construct, promoted lesion stabilization. In vitro studies showed that Ets2 was crucial for TNF&agr;-induced expression of monocyte chemoattractant protein 1, interleukin-6, and vascular cell adhesion molecule 1 in endothelial cells. In addition, Ets2 promoted tube formation and amplified TNF&agr;-induced loss of vascular endothelial integrity. Evaluation in a murine retina model further validated the role of Ets2 in regulating vessel inflammation and endothelial leakage. Conclusions: We provide the first evidence for the plaque-destabilizing role of Ets2 in atherosclerosis development by induction of an intraplaque proinflammatory phenotype in endothelial cells.

PDGF-Induced Migration of Vascular Smooth Muscle Cells Is Inhibited by Heme Oxygenase-1 Via VEGFR2 Upregulation and Subsequent Assembly of Inactive VEGFR2/PDGFRβ Heterodimers

Objective—In cardiovascular regulation, heme oxygenase-1 (HO-1) activity has been shown to inhibit vascular smooth muscle cell (VSMC) proliferation by promoting cell cycle arrest at the G1/S phase. However, the effect of HO-1 on VSMC migration remains unclear. We aim to elucidate the mechanism by which HO-1 regulates PDGFBB-induced VSMC migration. Methods and Results—Transduction of HO-1 cDNA adenoviral vector severely impeded human VSMC migration in a scratch, transmembrane, and directional migration assay in response to PDGFBB stimulation. Similarly, HO-1 overexpression in the remodeling process during murine retinal vasculature development attenuated VSMC coverage over the major arterial branches as compared with sham vector-transduced eyes. HO-1 expression in VSMCs significantly upregulated VEGFA and VEGFR2 expression, which subsequently promoted the formation of inactive PDGFR&bgr;/VEGFR2 complexes. This compromised PDGFR&bgr; phosphorylation and impeded the downstream cascade of FAK-p38 signaling. siRNA-mediated silencing of VEGFA or VEGFR2 could reverse the inhibitory effect of HO-1 on VSMC migration. Conclusion—These findings identify a potent antimigratory function of HO-1 in VSMCs, a mechanism that involves VEGFA and VEGFR2 upregulation, followed by assembly of inactive VEGFR2/PDGFR&bgr; complexes that attenuates effective PDGFR&bgr; signaling.

Dendritic Cell Function in Transplantation Arteriosclerosis Is Regulated by Heme Oxygenase 1

Rationale: Heme oxygenase (HO)1 is an important modulator of physiological function with cytoprotective properties. Although HO1 has previously been associated with an improved survival of the vascular allograft in rat models in response to pharmaceutical induction of HO1 the exact mechanism by which HO1 exerts it protective function remains to be elucidated. Objective: We sought to define the role of HO1 in dendritic cells (DCs) function that governs the alloimmune response underlying the development of transplantation associated vasculopathy. Methods and Results: Loss of HO1 in DCs or by small interfering RNA silencing resulted in major histocompatibility complex class II (MHCII) upregulation by CIITA- driven transcriptional regulation and by STAT1 (signal transducers and activators of transcription 1) phosphorylation. As a result, increased MHCII alloantigen presentation by HO1−/− DCs directed the primary T-cell response preferentially toward a CD4+ T-cell, rather than a CD8+ T-cell reaction. In a murine model for transplantation arteriosclerosis, adoptive transfer of HO1−/− DCs before allograft transplantation was indeed associated with pronounced intragraft CD4+ T-cell infiltration and increased IgG deposition, suggestive of an accelerated development of vasculopathy toward the chronic phase. The role of HO1 in DC-mediated T cell activation was further validated by inhibition of endogenous HO1 in allograft recipients. Inhibition of HO1 in DCs aggravated transplant arteriosclerosis development, by increasing intima hyperplasia, and by activation of a CD4+ T cells allograft response, mediated by MHCII upregulation. Conclusions: These findings demonstrate that HO1 plays an important role in the genetic regulation of the vascular alloimmune response elicited by DCs.

THSD1 preserves vascular integrity and protects against intraplaque haemorrhaging in ApoE−/− mice

AIMS Impairment of the endothelial barrier leads to microvascular breakdown in cardiovascular disease and is involved in intraplaque haemorrhaging and the progression of advanced atherosclerotic lesions that are vulnerable to rupture. The exact mechanism that regulates vascular integrity requires further definition. Using a microarray screen for angiogenesis-associated genes during murine embryogenesis, we identified thrombospondin type I domain 1 (THSD1) as a new putative angiopotent factor with unknown biological function. We sought to characterize the role of THSD1 in endothelial cells during vascular development and cardiovascular disease. METHODS AND RESULTS Functional knockdown of Thsd1 in zebrafish embryos and in a murine retina vascularization model induced severe haemorrhaging without affecting neovascular growth. In human carotid endarterectomy specimens, THSD1 expression by endothelial cells was detected in advanced atherosclerotic lesions with intraplaque haemorrhaging, but was absent in stable lesions, implying involvement of THSD1 in neovascular bleeding. In vitro, stimulation with pro-atherogenic factors (3% O2 and TNFα) decreased THSD1 expression in human endothelial cells, whereas stimulation with an anti-atherogenic factor (IL10) showed opposite effect. Therapeutic evaluation in a murine advanced atherosclerosis model showed that Thsd1 overexpression decreased plaque vulnerability by attenuating intraplaque vascular leakage, subsequently reducing macrophage accumulation and necrotic core size. Mechanistic studies in human endothelial cells demonstrated that THSD1 activates FAK-PI3K, leading to Rac1-mediated actin cytoskeleton regulation of adherens junctions and focal adhesion assembly. CONCLUSION THSD1 is a new regulator of endothelial barrier function during vascular development and protects intraplaque microvessels against haemorrhaging in advanced atherosclerotic lesions.

A 79-Year-Old Woman With Dyspnea and Hypoxemia That Worsened in an Upright Position

CASE PRESENTATION A 79-year-old woman presented to the ED with complaints of gradually worsening exertional dyspnea, dizziness, and chest discomfort. For several weeks she had not been able to perform light household work. The patients medical history mentioned pulmonary embolism following immobilization (2012), several fractures after trauma, an ischemic cerebral vascular accident (2014), and curative treatment for breast cancer (1995). Her current medication included esomeprazole, clopidogrel, simvastatin, calcium/vitamin D, amitriptyline, and acetaminophen.

Intravascular ultrasound chirp imaging

We demonstrate the feasibility of intravascular ultrasound chirp imaging. Chirp excitations were emitted with a 34 MHz single crystal intravascular transducer and compared to conventional Gaussian modulated pulses of equal peak negative pressure. The signal to noise ratio of the chirp images was increased up to 9 dB. The method shows potential for intravascular imaging of structures in and beyond coronary atherosclerotic plaques.