Project description:Endothelial cell (EC) metabolism regulates angiogenesis and is an emerging target for anti-angiogenic therapy in tumor and choroidal neovascularization (CNV). In contrast to tumor ECs (TECs), CNV-ECs cannot be isolated for unbiased metabolic target discovery. Here we used scRNA-sequencing to profile 28,337 choroidal ECs (CECs) from mice to in silico distinguish healthy CECs from CNV-ECs. Trajectory inference suggested that CNV-ECs plastically upregulate genes in central carbon metabolism and collagen biosynthesis during differentiation from quiescent postcapillary venous ECs. CEC-tailored genome scale metabolic modeling predicted essentiality of SQLE and ALDH18A1 for proliferation and collagen production, respectively. Comparative analysis in TECs revealed more outspoken metabolic transcriptome heterogeneity in subtypes and consistent upregulation of SQLE and ALDH18A1 across tumor types. Inhibition of SQLE and ALDH18A1 reduced sprouting angiogenesis in vitro. These findings demonstrate the potential of integrated scRNA-seq analysis to identify angiogenic metabolic targets in disease ECs.
Project description:Angiopoietin-like 4 (ANGPTL4) is known to regulate various cellular and systemic functions. However, its cell-specific role in endothelial cells (ECs) function and metabolic homeostasis remains to be elucidated. Here, using endothelial-specific Angptl4 knock-out mice (Angptl4iEC), and transcriptomics and metabolic flux analysis, we demonstrate that ANGPTL4 is required for maintaining EC metabolic function vital for vascular permeability and angiogenesis. Knockdown of ANGPTL4 in ECs promotes lipase-mediated lipoprotein lipolysis, which results in increased fatty acid (FA) uptake and oxidation. This is also paralleled by a decrease in proper glucose utilization for angiogenic activation of ECs. Mice with endothelial-specific deletion of Angptl4 showed decreased pathological neovascularization with stable vessel structures characterized by increased pericyte coverage and reduced permeability. Together, our study denotes the role of endothelial-ANGPTL4 in regulating cellular metabolism and angiogenic functions of EC.
Project description:Angiogenesis, a process mediating the expansion of vascular beds in many physiological and pathological settings, requires dynamic changes in endothelial cell (EC) behavior. The molecular mechanisms governing EC activity during different phases of vascular growth, remodeling, maturation, and quiescence remain elusive. Here, we have employed actively translating transcriptome analysis of mouse retinal ECs for the characterization of dynamic gene expression changes during postnatal development and the identification of critical angiogenic factors.
Project description:Age-related macular degeneration (AMD) is a global leading cause of visual impairment in older populations. ‘Wet’ AMD, the most common subtype of this disease, occurs when pathological angiogenesis infiltrates the subretinal space (choroidal neovascularization), causing hemorrhage and retinal damage. Gold standard anti-vascular endothelial growth factor (VEGF) treatment is an effective therapy, but the long-term prevention of visual decline has not been as successful. This warrants the need to elucidate potential VEGF-independent pathways. We generated blood out-growth endothelial cells (BOECs) from wet AMD and normal control subjects, then induced angiogenic sprouting of BOECs using a fibrin gel bead assay. To deconvolute endothelial heterogeneity, we performed single-cell transcriptomic analysis on the sprouting BOECs, revealing a spectrum of cell states. Our wet AMD BOECs share common pathways with choroidal neovascularization such as extracellular matrix remodeling that promoted proangiogenic phenotype, and our ‘activated’ BOEC subpopulation demonstrated proinflammatory hallmarks, resembling the tip-like cells in vivo. We uncovered new molecular insights that pathological angiogenesis in wet AMD BOECs could also be driven by interleukin signaling and amino acid metabolism. A web-based visualization of the sprouting BOEC single-cell transcriptome (https://christinecheunglab.shinyapps.io/human_wet_AMD_sprouting/) has been created to facilitate further discovery research.
Project description:Branching from conduits is a defining feature of the gas delivery systems of invertebrates (tracheae built from epithelial cells) and vertebrates (vasculature lined by endothelial cells). Here, we show that the vertebrate transcriptional repressor Tel plays an evolutionarily conserved role in angiogenesis: it is indispensable for sprouting of primary human endothelial cells and for the normal development of the Danio rerio embryo blood circulatory system. Tel controls endothelial sprouting via binding to the generic co-repressor C-terminal binding protein (CtBP). In endothelial cells, the Tel:CtBP complex temporally restricts a VEGF-mediated pulse of dll4 expression and consequently integrates VEGFR intracellular signaling and intercellular Notch-Dll4 signaling. It further refines branching by regulating expression of other factors that constrain angiogenesis such as sprouty family members and ve-cadherin. Thus, the Tel:CtBP complex moderates the balance between positive and antagonistic angiogenesis cues and thereby conditions endothelial cells for angiogenesis. Since the activity of CtBP is attuned to intracellular NADH levels, our results raise the possibility that Tel-mediated sprouting could be sensitized to the metabolic status of the tissue. Tel control of branching appears to be evolutionarily conserved since Yan, the invertebrate orthologue of Tel, is similarly required for branching morphogenesis of the invertebrate tracheae. Collectively, our work suggests that Tel is a central regulator of angiogenesis and highlights Tel and its associated networks as potential targets for the development of therapeutic strategies to inhibit pathological angiogenesis. 2 independent screens were performed testing effects of knockdown of Tel or CtBP (screen 1) or effects of VEGF-A (screen 2) on Human Umbilical Vein Endothelial Cells (HUVECs). For screen 1 we tested 3 different conditions. We established stable HUVEC cell lines which were either infected with control lentivirus (Mock), or lentivirus expressing short hairpin RNA constructs for the specific knockdown of Tel(Teli) or CtBP2 (CtBP2i). Expression in the Teli and CtBP2i cell lines was compared to expression in the Mock cell line for screen 1. For screen 2 we tested 2 conditions. We exposed HUVECs to VEGF (50ng/mL) for 30 minutes (samplename: VEGF30) and compared the transcriptome of these cells to untreated HUVECs (VEGF0). For each condition 2 independent repeats were analyzed and expression of genes was averaged for each repeat. HUVECs were grown under standard conditions (37degrees Celsius, 5% CO2) in EGM2 medium (Lonza).
Project description:Heterogeneity of endothelial cells that form the innermost layer of all vessels is critical for vascular sprouting and angiogenesis. After new vessels form, endothelial cell heterogeneity is believed to be gradually lost as vessels respond to flow-mediated signals, mature, remodel and become homeostatic. However, whether and at what level endothelial cell lost heterogeneity is poorly understood. Here we investigated heterogeneity change of endothelial cells under homeostatic laminar shear tress in comparison to static cultures.
Project description:Angiogenesis, the formation of new blood vessels from pre-existing ones, is a complex and demanding biological process that plays an important role in physiological as well as pathological settings such as cancer and ischemia. Given its critical role, the regulation of endothelial growth factor receptor (e.g. VEGFR2, FGFR1) represents important mechanisms for the control of angiogenesis. Recent evidences support cell metabolism as a critical regulator of angiogenesis. However, it is unknown how glutamine metabolism regulates growth factor receptor expression. Here, by using genetic and pharmacological approaches, we show that glutaminolysis and glutamate-dependent transaminases (TAs) support alpha-ketoglutarate (αKG) levels and are critical regulators of angiogenic response during pathological conditions. Indeed, the endothelial specific blockage of GLS1 impairs ischemic and tumor angiogenesis by suppressing VEGFR2 translation via mTORC1-dependent pathway. Lastly, we discover that ECs catabolized the glutamine-derived glutamate via phosphoserine aminotransferase 1 (PSAT1) as crucial to support VEGFR2 translation. These findings identify glutamine anaplerosis and TA activity as a critical regulator of growth factor receptor translation in normal and pathological angiogenesis. We anticipate our studies to be a starting point for novel anti-angiogenesis approaches based on GLS1/PSAT1 inhibitor treatments to overcome anti-VEGF therapies resistance.
Project description:Exercise is a powerful driver of physiological angiogenesis during adulthood, but the mechanisms of exercise-induced vascular expansion are poorly understood. We explored endothelial heterogeneity in skeletal muscle and identified two capillary muscle endothelial cells (mEC) populations which are characterized by differential expression of ATF3/4. Spatial mapping showed that ATF3/4 + mECs are enriched in red oxidative muscle areas while ATF3/4 low ECs lie adjacent to white glycolytic fibers. In vitro and in vivo experiments revealed that red ATF3/4 + mECs are more angiogenic when compared to white ATF3/4 low mECs. Mechanistically, ATF3/4 in mECs control genes involved in amino acid uptake and metabolism and metabolically prime red (ATF3/4 + ) mECs for angiogenesis. As a consequence, supplementation of non-essential amino acids and overexpression of ATF4 increased proliferation of white mECs. Finally, deleting Atf4 in ECs impaired exercise-induced angiogenesis. Our findings illustrate that spatial metabolic angiodiversity determines the angiogenic potential of muscle ECs.