Reprogramming of myeloid angiogenic cells by Bartonella henselae leads to microenvironmental regulation of pathological angiogenesis.

The contribution of myeloid cells to tumour microenvironments is a decisive factor in cancer progression. Tumour-associated macrophages (TAMs) mediate tumour invasion and angiogenesis through matrix remodelling, immune modulation and release of pro-angiogenic cytokines. Nothing is known about how pathogenic bacteria affect myeloid cells in these processes.

Histone deacetylase 9 promotes angiogenesis by targeting the antiangiogenic microRNA-17-92 cluster in endothelial cells.

Objective: Histone deacetylases (HDACs) modulate gene expression by deacetylation of histone and nonhistone proteins. Several HDACs control angiogenesis, but the role of HDAC9 is unclear.

Methods And Results: Here, we analyzed the function of HDAC9 in angiogenesis and its involvement in regulating microRNAs.

Atheroprotective communication between endothelial cells and smooth muscle cells through miRNAs.

The shear-responsive transcription factor Krüppel-like factor 2 (KLF2) is a critical regulator of endothelial gene expression patterns induced by atheroprotective flow. As microRNAs (miRNAs) post-transcriptionally control gene expression in many pathogenic and physiological processes, we investigated the regulation of miRNAs by KLF2 in endothelial cells. KLF2 binds to the promoter and induces a significant upregulation of the miR-143/145 cluster.

Epigenetic regulation of endothelial lineage committed genes in pro-angiogenic hematopoietic and endothelial progenitor cells.

Rationale: Proangiogenic hematopoietic and endothelial progenitor cells (EPCs) contribute to postnatal neovascularization, but the mechanisms regulating differentiation to the endothelial lineage are unclear.

Objective: To elucidate the epigenetic control of endothelial gene expression in proangiogenic cells and EPCs.

Methods And Results: Here we demonstrate that the endothelial nitric oxide synthase (eNOS) promoter is epigenetically silenced in proangiogenic cells (early EPCs), CD34(+) cells, and mesoangioblasts by DNA methylation and prominent repressive histone H3K27me3 marks.

Class IIb HDAC6 regulates endothelial cell migration and angiogenesis by deacetylation of cortactin.

Histone deacetylases (HDACs) deacetylate histones and non-histone proteins, thereby affecting protein activity and gene expression. The regulation and function of the cytoplasmic class IIb HDAC6 in endothelial cells (ECs) is largely unexplored. Here, we demonstrate that HDAC6 is upregulated by hypoxia and is essential for angiogenesis.

Transplantation of progenitor cells and regeneration enhancement in acute myocardial infarction (TOPCARE-AMI): final 5-year results suggest long-term safety and efficacy.

Background: Limited data is available for investigating the long-term safety and effects of intracoronary progenitor cell therapy in patients with acute myocardial infarction (AMI).

Objective: To assess the clinical course, NT-proBNP and MRI data as objective markers of cardiac function of the TOPCARE-AMI patients at 5-year follow-up.

Design: The TOPCARE-AMI trial was the first randomized study investigating the effects of intracoronary infusion of circulating (CPC) or bone marrow-derived progenitor cells (BMC) in 59 patients with successfully reperfused AMI.

Proteomic characterization of human early pro-angiogenic cells.

Early pro-angiogenic cells (EPCs) have been shown to be involved in neovascularization, angiogenesis and re-endothelialization and cathepsin L inhibition blunted their pro-angiogenic effect. In the present study, we have analysed and mapped the proteome and secretome of human EPCs, utilizing a combination of difference in-gel electrophoresis (DIGE) and shotgun proteomics. A population of 206 protein spots were analysed, with 171 being identified in the cellular proteome of EPCs.

Angiopoietin-2 regulates gene expression in TIE2-expressing monocytes and augments their inherent proangiogenic functions.

TIE2-expressing monocytes/macrophages (TEM) are a highly proangiogenic subset of myeloid cells in tumors. Here, we show that circulating human TEMs are already preprogrammed in the circulation to be more angiogenic and express higher levels of such proangiogenic genes as matrix metalloproteinase-9 (MMP-9), VEGFA, COX-2, and WNT5A than TIE2(-) monocytes. Additionally, angiopoietin-2 (ANG-2) markedly enhanced the proangiogenic activity of TEMs and increased their expression of two proangiogenic enzymes: thymidine phosphorylase (TP) and cathepsin B (CTSB).

Kruppel-like factor 2 improves neovascularization capacity of aged proangiogenic cells.

Aims: Coronary artery disease (CAD) patients have less circulating proangiogenic cells (PACs), formerly known as endothelial progenitor cells, which exhibit impaired neovascularization properties. Inverse correlations were also found between PAC function and risk factors like age. Krüppel-like factor 2 (KLF2) is expressed by mature endothelial cells (ECs), is induced by both shear stress and statins, and provokes endothelial functional differentiation.

Comparative proteomics profiling reveals role of smooth muscle progenitors in extracellular matrix production.

Objective: Recent studies on cardiovascular progenitors have led to a new appreciation that paracrine factors may support the regeneration of damaged tissues.

Methods And Results: We used a shotgun proteomics strategy to compare the secretome of peripheral blood-derived smooth muscle progenitors (SPCs) with human aortic smooth muscle cells. The late-outgrowth SPCs produced fewer proteolytic enzymes and inflammatory cytokines and showed reduced invasive capacity.

Mechanism of improved cardiac function after bone marrow mononuclear cell therapy: role of cardiovascular lineage commitment.

Background: Cell therapy is a promising option to improve functional recovery after ischemia. Several subsets of bone marrow-derived cells were shown to reduce infarct size and increase ejection fraction in experimental models of ischemia. The mechanisms underlying the functional improvement are diverse and have been shown to include paracrine effects of the injected cells, as well as a variable degree of differentiation to endothelial cells, pericytes, smooth muscle, and cardiac muscle.

Members of the microRNA-17-92 cluster exhibit a cell-intrinsic antiangiogenic function in endothelial cells.

MicroRNAs are endogenously expressed small noncoding RNAs that regulate gene expression on the posttranscriptional level. The miR-17-92 cluster (encoding miR-17, -18a, -19a/b, -20a, and miR-92a) is highly expressed in tumor cells and is up-regulated by ischemia. Whereas miR-92a was recently identified as negative regulator of angiogenesis, the specific functions of the other members of the cluster are less clear.

Sox2 transduction enhances cardiovascular repair capacity of blood-derived mesoangioblasts.

Rationale: Complementation of pluripotency genes may improve adult stem cell functions.

Objectives: Here we show that clonally expandable, telomerase expressing progenitor cells can be isolated from peripheral blood of children. The surface marker profile of the clonally expanded cells is distinct from hematopoietic or mesenchymal stromal cells, and resembles that of embryonic multipotent mesoangioblasts.

MicroRNA-92a controls angiogenesis and functional recovery of ischemic tissues in mice.

MicroRNAs (miRs) are small noncoding RNAs that regulate gene expression by binding to target messenger RNAs (mRNAs), leading to translational repression or degradation. Here, we show that the miR-17approximately92 cluster is highly expressed in human endothelial cells and that miR-92a, a component of this cluster, controls the growth of new blood vessels (angiogenesis). Forced overexpression of miR-92a in endothelial cells blocked angiogenesis in vitro and in vivo.

Proteomic analysis reveals presence of platelet microparticles in endothelial progenitor cell cultures.

The concept of endothelial progenitor cells (EPCs) has attracted considerable interest in cardiovascular research, but despite a decade of research there are still no specific markers for EPCs and results from clinical trials remain controversial. Using liquid chromatography-tandem mass spectrometry, we analyzed the protein composition of microparticles (MPs) originating from the cell surface of EPC cultures. Our data revealed that the conventional methods for isolating mononuclear cells lead to a contamination with platelet proteins.

HDAC5 is a repressor of angiogenesis and determines the angiogenic gene expression pattern of endothelial cells.

Class IIa histone deacetylases (HDACs) are signal-responsive regulators of gene expression involved in vascular homeostasis. To investigate the differential role of class IIa HDACs for the regulation of angiogenesis, we used siRNA to specifically suppress the individual HDAC isoenzymes. Silencing of HDAC5 exhibited a unique pro-angiogenic effect evidenced by increased endothelial cell migration, sprouting, and tube formation.

Caspase-8 is involved in neovascularization-promoting progenitor cell functions.

Objective: Endothelial progenitor cells (EPCs) comprise a heterogeneous population of cells, which improve therapeutic neovascularization after ischemia. The neovascularization-promoting potential of progenitor cells depends on survival and retention of the infused cells to the tissue. Caspases mediate apoptosis but are also involved in other critical biological processes.

Sustained persistence of transplanted proangiogenic cells contributes to neovascularization and cardiac function after ischemia.

Circulating blood-derived vasculogenic cells improve neovascularization of ischemic tissue by a broad repertoire of potential therapeutic actions. Whereas initial studies documented that the cells incorporate and differentiate to cardiovascular cells, other studies suggested that short-time paracrine mechanisms mediate the beneficial effects. The question remains to what extent a physical incorporation is contributing to the beneficial effects of cell therapy.

The Wnt antagonist Dickkopf-1 mobilizes vasculogenic progenitor cells via activation of the bone marrow endosteal stem cell niche.

Therapeutic mobilization of vasculogenic progenitor cells is a novel strategy to enhance neovascularization for tissue repair. Prototypical mobilizing agents such as granulocyte colony-stimulating factor mobilize vasculogenic progenitor cells from the bone marrow concomitantly with inflammatory cells. In the bone marrow, mobilization is regulated in the stem cell niche, in which endosteal cells such as osteoblasts and osteoclasts play a key role.

High glucose reduces cathepsin L activity and impairs invasion of circulating progenitor cells.

Endothelial progenitor cells (EPC) significantly contribute to neovascularization and endothelial regeneration. Risk factors for coronary artery disease, particularly diabetes mellitus, reduce the number and functional activity of EPC. As we have recently shown, expression and activity of the matrix degrading cysteine protease cathepsin L in EPC is required for tissue invasion and EPC-mediated improvement of neovascularization.

Impaired interaction of platelets with endothelial progenitor cells in patients with cardiovascular risk factors.

Objective: Recent studies indicate that platelets influence endothelial progenitor cell (EPC) recruitment to sites of vascular injury and promote their differentiation to an endothelial phenotype. Patients with cardiovascular risk factors (CVRF) demonstrate a reduced number and impaired function of EPC, as well as platelet hyper-reactivity. Therefore, we investigated the interaction of platelets and EPC from patients with CVRF.

Interleukin-10 from transplanted bone marrow mononuclear cells contributes to cardiac protection after myocardial infarction.

Bone marrow mononuclear cells (BM-MNCs) have successfully been used as a therapy for the improvement of left ventricular (LV) function after myocardial infarction (MI). It has been suggested that paracrine factors from BM-MNCs may be a key mechanism mediating cardiac protection. We previously performed microarray analysis and found that the pleiotropic cytokine interleukin (IL)-10 was highly upregulated in human progenitor cells in comparison with adult endothelial cells and CD14+ cells.

Role of microRNAs in vascular diseases, inflammation, and angiogenesis.

The integrity of the endothelial monolayer is fundamental for the homoeostasis of the vascular system. Functional endothelial cells are also required for the growth of new blood vessels during neovascularization. Although multiple growth factors have been shown to regulate angiogenesis and vascular development, little is known about the complex upstream regulation of gene expression and translation.

Cytochrome P450 2C9-induced angiogenesis is dependent on EphB4.

Objective: Cytochrome P450 (CYP) epoxygenase-derived epoxyeicosatrienoic acids (EETs) are known to stimulate angiogenesis, but the mechanisms involved are incompletely understood. Because EphB4 is involved in vascular development, the aim of this study was to investigate whether, and to what extent, EphB4 is part of the signaling cascade that results in CYP2C9-mediated angiogenesis.

Methods And Results: CYP2C9 overexpression as well as stimulation with 11,12-EET (up to 48 hours) time-dependently increased EphB4 expression in endothelial cells.