Masataka Sata

Hematopoietic stem cells differentiate into vascular cells that participate in the pathogenesis of atherosclerosis

Excessive accumulation of smooth-muscle cells (SMCs) has a key role in the pathogenesis of vascular diseases. It has been assumed that SMCs derived from the outer medial layer migrate, proliferate and synthesize extracellular matrix components on the luminal side of the vessel. Although much effort has been devoted to targeting migration and proliferation of medial SMCs, there is no effective therapy that prevents occlusive vascular remodeling. We show here that in models of post-angioplasty restenosis, graft vasculopathy and hyperlipidemia-induced atherosclerosis, bone-marrow cells give rise to most of the SMCs that contribute to arterial remodeling. Notably, purified hematopoietic stem cells differentiate into SMCs in vitro and in vivo. Our findings indicate that somatic stem cells contribute to pathological remodeling of remote organs, and may provide the basis for the development of new therapeutic strategies for vascular diseases through targeting mobilization, homing, differentiation and proliferation of bone marrow-derived vascular progenitor cells.

Role of adiponectin in preventing vascular stenosis: The missing link of adipo-vascular axis

Obesity is more linked to vascular disease, including atherosclerosis and restenotic change, after balloon angioplasty. The precise mechanism linking obesity and vascular disease is still unclear. Previously we have demonstrated that the plasma levels of adiponectin, an adipose-derived hormone, decreases in obese subjects, and that hypoadiponectinemia is associated to ischemic heart disease. In current the study, we investigated the in vivorole of adiponectin on the neointimal thickening after artery injury using adiponectin-deficient mice and adiponectin-producing adenovirus. Adiponectin-deficient mice showed severe neointimal thickening and increased proliferation of vascular smooth muscle cells in mechanically injured arteries. Adenovirus-mediated supplement of adiponectin attenuated neointimal proliferation. In cultured smooth muscle cells, adiponectin attenuated DNA synthesis induced by growth factors including platelet-derived growth factor, heparin-binding epidermal growth factor (EGF)-like growth factor (HB-EGF), basic fibroblast growth factor, and EGF and cell proliferation and migration induced by HB-EGF. In cultured endothelial cells, adiponectin attenuated HB-EGF expression stimulated by tumor necrosis factor α. The current study suggests an adipo-vascular axis, a direct link between fat and artery. A therapeutic strategy to increase plasma adiponectin should be useful in preventing vascular restenosis after angioplasty.

Notch1 but Not Notch2 Is Essential for Generating Hematopoietic Stem Cells from Endothelial Cells

Hematopoietic stem cells (HSCs) are thought to arise in the aorta-gonad-mesonephros (AGM) region of embryo proper, although HSC activity can be detected in yolk sac (YS) and paraaortic splanchnopleura (P-Sp) when transplanted in newborn mice. We examined the role of Notch signaling in embryonic hematopoiesis. The activity of colony-forming cells in the YS from Notch1(-/-) embryos was comparable to that of wild-type embryos. However, in vitro and in vivo definitive hematopoietic activities from YS and P-Sp were severely impaired in Notch1(-/-) embryos. The population representing hemogenic endothelial cells, however, did not decrease. In contrast, Notch2(-/-) embryos showed no hematopoietic deficiency. These data indicate that Notch1, but not Notch2, is essential for generating hematopoietic stem cells from endothelial cells.

Krüppel-like zinc-finger transcription factor KLF5/BTEB2 is a target for angiotensin II signaling and an essential regulator of cardiovascular remodeling.

We recently isolated a Krüppel-like zinc-finger transcription factor 5 (KLF5; also known as BTEB2 and IKLF), which is markedly induced in activated vascular smooth-muscle cells and fibroblasts. Here we describe our analysis of the in vivo function of KLF5 using heterozygous KLF5-knockout mice (Klf5+/−). In response to external stress, Klf5+/− mice showed diminished levels of arterial-wall thickening, angiogenesis, cardiac hypertrophy and interstitial fibrosis. Also, angiotensin II induced expression of KLF5, which in turn activated platelet-derived growth factor-A (PDGF-A) and transforming growth factor-β (TGF-β) expression. In addition, we determined that KLF5 interacted with the retinoic-acid receptor (RAR), that synthetic RAR ligands modulated KLF5 transcriptional activity, and that in vivo administration of RAR ligands affected stress responses in the cardiovascular system in a KLF5-dependent manner. KLF5 thus seems to be a key element linking external stress and cardiovascular remodeling.

Diverse Contribution of Bone Marrow Cells to Neointimal Hyperplasia After Mechanical Vascular Injuries

Abstract— We and others have suggested that bone marrow-derived progenitor cells may contribute to the pathogenesis of vascular diseases. On the other hand, it was reported that bone marrow cells do not participate substantially in vascular remodeling in other experimental systems. In this study, three distinct types of mechanical vascular injuries were induced in the same mouse whose bone marrow had been reconstituted with that of GFP or LacZ mice. All injuries are known to cause smooth muscle cell (SMC) hyperplasia. At 4 weeks after wire-mediated endovascular injury, a significant number of the neointimal and medial cells derived from bone marrow. In contrast, marker-positive cells were seldom detected in the lesion induced by perivascular cuff replacement. There were only a few bone marrow-derived cells in the neointima after ligation of the common carotid artery. These results indicate that the origin of intimal cells is diverse and that contribution of bone marrow-derived cells to neointimal hyperplasia depends on the type of model.

Oxidized LDL activates fas-mediated endothelial cell apoptosis

Oxidized low density lipoproteins (OxLDL) promote chronic inflammatory responses in the vasculature that give rise to atherosclerotic plaques. Fas ligand (FasL) is naturally expressed on the vascular endothelium where it can induce apoptosis in Fas-expressing immune cells as they enter the vessel wall. Although vascular endothelial cells are normally resistant to Fas-mediated cell death, OxLDL were shown to induce apoptosis in cultured endothelial cells and endothelium of arterial explants by a process that could be inhibited with Fas L neutralizing antibodies. OxLDL-induced cell death was also reduced in the aortic endothelium cultured from gld (FasL-/-) and lpr (Fas-/-) mice as compared with wild-type mice. OxLDL acted by sensitizing endothelial cells to death signals from the Fas receptor. Thus, the ability of OxLDL to promote Fas-mediated endothelial cell suicide may be a feature that contributes to their atherogenicity.

Coronary Atherosclerosis Is Associated With Macrophage Polarization in Epicardial Adipose Tissue

OBJECTIVES The purpose of this report was to assess the link between macrophage polarization in epicardial adipose tissue and atherosclerosis in patients with coronary artery disease (CAD). BACKGROUND Macrophage accumulation enhances chronic inflammation in adipose tissue, but macrophage phenotypic change in human epicardial adipose tissue and its role in atherogenesis are unknown. METHODS Samples were obtained from epicardial and subcutaneous adipose tissue during elective cardiac surgery (CAD, n = 38; non-CAD, n = 40). Infiltration of M1/M2 macrophages was investigated by immunohistochemical staining with antibodies against CD11c and CD206, respectively. Expression of pro- and anti-inflammatory adipocytokines in adipose tissue was evaluated by real-time quantitative polymerase chain reaction. RESULTS Infiltration of macrophages and expression of pro- and anti-inflammatory cytokines were enhanced in epicardial fat of patients with CAD compared with that in non-CAD patients (p < 0.05). The ratio of M1/M2 macrophages was positively correlated with the severity of CAD (r = 0.312, p = 0.039). Furthermore, the expression of pro-inflammatory cytokines was positively correlated, and the expression of anti-inflammatory cytokines was negatively correlated with the ratio of M1/M2 macrophages in epicardial adipose tissue of CAD patients. By contrast, there was no significant difference in macrophage infiltration and cytokine expression in subcutaneous adipose tissue between the CAD and non-CAD groups. CONCLUSIONS The ratio of M1/M2 macrophages in epicardial adipose tissue of CAD patients is changed compared with that in non-CAD patients. Human coronary atherosclerosis is associated with macrophage polarization in epicardial adipose tissue.

Blockade of the Stromal Cell–Derived Factor-1/CXCR4 Axis Attenuates In vivo Tumor Growth by Inhibiting Angiogenesis in a Vascular Endothelial Growth Factor–Independent Manner

The interaction between the chemokine receptor CXCR4 and its specific ligand, stromal cell-derived factor-1 (SDF-1/CXCL12), mediates several cellular functions. In cancer, SDF-1-positive or CXCR4-positive cells of various lineages are detected within tumor tissues. Recent intensive research has indicated the possibility that blocking CXCR4 could reduce the metastatic potential of cancer cells. Here, we show that the inhibition of the SDF-1/CXCR4 axis decreases the growth of s.c. gastrointestinal tumors through the suppression of tumor neoangiogenesis. The neutralization of CXCR4 suppressed the growth in vivo of tumors derived from mouse Colon38 and PancO2 cells, whereas it did not affect the growth of Colon38 and PancO2 cells in vitro. This attenuation of tumor growth was found to be independent of the expression of CXCR4 by the cancer cells themselves, because CXCR4 knocked-down Colon38 cells grew similarly to control cells. Furthermore, CD31-positive tumor capillaries were reduced to 45% (P < 0.001) and intratumor blood flows were decreased to 65% (P < 0.01) by blockade of CXCR4. The vascular endothelial growth factor (VEGF) concentration in the tumors was not affected by the neutralization of CXCR4. Taken together with the detection of CXCR4-positive endothelial cells in the tumor tissues, the findings suggest that the antiangiogenic effects of the blockade of CXCR4 are related to a reduction of the establishment of tumor endothelium independently of VEGF inhibition. Our data indicate that the SDF-1/CXCR4 pathway might be a general target for anticancer strategies and that blocking this system could be cooperatively effective in combination with other antiangiogenic therapies, such as blockade of VEGF.

AMP-Activated Protein Kinase Inhibits Angiotensin II–Stimulated Vascular Smooth Muscle Cell Proliferation

Background—AMP-activated protein kinase (AMPK) is a stress-activated protein kinase that works as a metabolic sensor of cellular ATP levels. Here, we investigated whether AMPK signaling has a role in the regulation of the angiotensin II (Ang II)–induced proliferation signal in rat vascular smooth muscle cells (VSMCs). Methods and Results—Aminoimidazole-4-carboxamide-1-&bgr;-ribofuranoside (AICAR) activated AMPK in rat VSMCs and inhibited Ang II–induced extracellular signal–regulated kinase 1/2 phosphorylation but not that of p38 MAPK or Akt/PKB. Although Ang II activated AMPK, this activation was significantly inhibited by catalase, N-acetylcysteine, and diphenyleneiodonium chloride, an NADPH oxidase inhibitor. Moreover, the observation that AMPK was activated by H2O2 suggests that AMPK is redox sensitive. The Ang II type 1 receptor antagonist valsartan but not the Ang II type 2 receptor antagonist PD123319 significantly inhibited Ang II–induced AMPK activation, suggesting that Ang II–induced AMPK activation was Ang II type 1 receptor dependent. Whereas 3H-thymidine incorporation by VSMCs treated with Ang II was significantly inhibited when the cells were pretreated with 1 mmol/L AICAR, the inhibition of AMPK by dominant-negative AMPK overexpression augmented Ang II–induced cell proliferation. Subcutaneous injection of AICAR (1 mg/g body weight per day) for 2 weeks suppressed neointimal formation after transluminal mechanical injury of the rat femoral artery. Conclusions—Our findings indicate that Ang II–induced AMPK activation is synchronized with extracellular signal-regulated kinase signaling and that AMPK works as an inhibitor of the Ang II proliferative pathway. AMPK signaling might serve as a new therapeutic target of vascular remodeling in cardiovascular diseases.

G-CSF stimulates angiogenesis and promotes tumor growth: potential contribution of bone marrow-derived endothelial progenitor cells.

Solid tumors require neovascularization for their growth. Recent evidence indicates that bone marrow-derived endothelial progenitor cells (EPCs) contribute to tumor angiogenesis. We show here that granulocyte colony-stimulating factor (G-CSF) markedly promotes growth of the colon cancer inoculated into the subcutaneous space of mice, whereas G-CSF had no effect on cancer cell proliferation in vitro. The accelerated tumor growth was associated with enhancement of neovascularization in the tumor. We found that bone marrow-derived cells participated in new blood vessel formation in tumor. Our findings suggest that G-CSF may have potential to promote tumor growth, at least in part, by stimulating angiogenesis in which bone marrow-derived EPCs play a role.