Angiogenesis Publications

Uemura A, Fruttiger M, D'Amore PA, De Falco S, Joussen AM, Sennlaub F, Brunck LR, Johnson KT, Lambrou GN, Rittenhouse KD, Langmann T. VEGFR1 signaling in retinal angiogenesis and microinflammation. Prog Retin Eye Res 2021;84:100954.Abstract
Five vascular endothelial growth factor receptor (VEGFR) ligands (VEGF-A, -B, -C, -D, and placental growth factor [PlGF]) constitute the VEGF family. VEGF-A binds VEGF receptors 1 and 2 (VEGFR1/2), whereas VEGF-B and PlGF only bind VEGFR1. Although much research has been conducted on VEGFR2 to elucidate its key role in retinal diseases, recent efforts have shown the importance and involvement of VEGFR1 and its family of ligands in angiogenesis, vascular permeability, and microinflammatory cascades within the retina. Expression of VEGFR1 depends on the microenvironment, is differentially regulated under hypoxic and inflammatory conditions, and it has been detected in retinal and choroidal endothelial cells, pericytes, retinal and choroidal mononuclear phagocytes (including microglia), Müller cells, photoreceptor cells, and the retinal pigment epithelium. Whilst the VEGF-A decoy function of VEGFR1 is well established, consequences of its direct signaling are less clear. VEGFR1 activation can affect vascular permeability and induce macrophage and microglia production of proinflammatory and proangiogenic mediators. However the ability of the VEGFR1 ligands (VEGF-A, PlGF, and VEGF-B) to compete against each other for receptor binding and to heterodimerize complicates our understanding of the relative contribution of VEGFR1 signaling alone toward the pathologic processes seen in diabetic retinopathy, retinal vascular occlusions, retinopathy of prematurity, and age-related macular degeneration. Clinically, anti-VEGF drugs have proven transformational in these pathologies and their impact on modulation of VEGFR1 signaling is still an opportunity-rich field for further research.
Khajavi M, Zhou Y, Schiffer AJ, Bazinet L, Birsner AE, Zon L, D'Amato RJ. Identification of Basp1 as a novel angiogenesis-regulating gene by multi-model system studies. FASEB J 2021;35(5):e21404.Abstract
We have previously used the genetic diversity available in common inbred mouse strains to identify quantitative trait loci (QTLs) responsible for the differences in angiogenic response using the corneal micropocket neovascularization (CoNV) assay. Employing a mouse genome-wide association study (GWAS) approach, the region on chromosome 15 containing Basp1 was identified as being significantly associated with angiogenesis in inbred strains. Here, we developed a unique strategy to determine and verify the role of BASP1 in angiogenic pathways. Basp1 expression in cornea had a strong correlation with a haplotype shared by mouse strains with varied angiogenic phenotypes. In addition, inhibition of BASP1 demonstrated a dosage-dependent effect in both primary mouse brain endothelial and human microvascular endothelial cell (HMVEC) migration. To investigate its role in vivo, we knocked out basp1 in transgenic kdrl:zsGreen zebrafish embryos using a widely adopted CRISPR-Cas9 system. These embryos had severely disrupted vessel formation compared to control siblings. We further show that basp1 promotes angiogenesis by upregulating β-catenin gene and the Dll4/Notch1 signaling pathway. These results, to the best of our knowledge, provide the first in vivo evidence to indicate the role of Basp1 as an angiogenesis-regulating gene and opens the potential therapeutic avenues for a wide variety of systemic angiogenesis-dependent diseases.
Fu Z, Smith LEH. Cellular senescence in pathologic retinal angiogenesis. Trends Endocrinol Metab 2021;32(7):415-416.Abstract
Pathologic angiogenesis causes blindness in many eye diseases. Crespo-Garcia, Tsuruda, and Dejda et al. employed bioinformatics to characterize cell senescence as a primary factor in the common pathogenesis of retinopathies. They validated their findings using human and mouse retina with proliferative retinopathy. Clearance of senescent cells suppressed neovessel growth.
Di Zazzo A, Gaudenzi D, Yin J, Coassin M, Fernandes M, Dana R, Bonini S. Corneal angiogenic privilege and its failure. Exp Eye Res 2021;204:108457.Abstract
The cornea actively maintains its own avascular status to preserve its ultimate optical function. This corneal avascular state is also defined as "corneal angiogenic privilege", which results from a critical and sensitive balance between anti-angiogenic and pro-angiogenic mechanisms. In our review, we aim to explore the complex equilibrium among multiple mediators which prevents neovascularization in the resting cornea, as well as to unveil the evolutive process which leads to corneal angiogenesis in response to different injuries.
Whitmore HAB, Amarnani D, O'Hare M, Delgado-Tirado S, Gonzalez-Buendia L, An M, Pedron J, Bushweller JH, Arboleda-Velasquez JF, Kim LA. TNF-α signaling regulates RUNX1 function in endothelial cells. FASEB J 2021;35(2):e21155.Abstract
Runt-related transcription factor 1 (RUNX1) acts as a mediator of aberrant retinal angiogenesis and has been implicated in the progression of proliferative diabetic retinopathy (PDR). Patients with PDR, retinopathy of prematurity (ROP), and wet age-related macular degeneration (wet AMD) have been found to have elevated levels of Tumor Necrosis Factor-alpha (TNF-α) in the eye. In fibrovascular membranes (FVMs) taken from patients with PDR RUNX1 expression was increased in the vasculature, while in human retinal microvascular endothelial cells (HRMECs), TNF-α stimulation causes increased RUNX1 expression, which can be modulated by RUNX1 inhibitors. Using TNF-α pathway inhibitors, we determined that in HRMECs, TNF-α-induced RUNX1 expression occurs via JNK activation, while NF-κB and p38/MAPK inhibition did not affect RUNX1 expression. JNK inhibitors were also effective at stopping high D-glucose-stimulated RUNX1 expression. We further linked JNK to RUNX1 through Activator Protein 1 (AP-1) and investigated the JNK-AP-1-RUNX1 regulatory feedback loop, which can be modulated by VEGF. Additionally, stimulation with TNF-α and D-glucose had an additive effect on RUNX1 expression, which was downregulated by VEGF modulation. These data suggest that the downregulation of RUNX1 in conjunction with anti-VEGF agents may be important in future treatments for the management of diseases of pathologic ocular angiogenesis.
Wu W, Xia X, Tang L, Yao F, Xu H, Lei H. Normal vitreous promotes angiogenesis via activation of Axl. FASEB J 2021;35(1):e21152.Abstract
Vitreous has been reported to prevent tumor angiogenesis, but our previous findings indicate that vitreous activate the signaling pathway of phosphoinositide 3-kinase (PI3K)/Akt, which plays a critical role in angiogenesis. The goal of this research is to determine which role of vitreous plays in angiogenesis-related cellular responses in vitro. We found that in human retinal microvascular endothelial cells (HRECs) vitreous activates a number of receptor tyrosine kinases including Anexelekto (Axl), which plays an important role in angiogenesis. Subsequently, we discovered that depletion of Axl using CRISPR/Cas9 and an Axl-specific inhibitor R428 suppress vitreous-induced Akt activation and cell proliferation, migration, and tuber formation of HRECs. Therefore, this line of research not only demonstrate that vitreous promotes angiogenesis in vitro, but also reveal that Axl is one of receptor tyrosine kinases to mediate vitreous-induced angiogenesis in vitro, thereby providing a molecular basis for removal of vitreous as cleanly as possible when vitrectomy is performed in treating patients with proliferative diabetic retinopathy.
Wang J, Wang X, Gao Y, Lin Z, Chen J, Gigantelli J, Shapiro JI, Xie Z, Pierre SV. Stress Signal Regulation by Na/K-ATPase As a New Approach to Promote Physiological Revascularization in a Mouse Model of Ischemic Retinopathy. Invest Ophthalmol Vis Sci 2020;61(14):9.Abstract
Purpose: The identification of target pathways to block excessive angiogenesis while simultaneously restoring physiological vasculature is an unmet goal in the therapeutic management of ischemic retinopathies. pNaKtide, a cell-permeable peptide that we have designed by mapping the site of α1 Na/K-ATPase (NKA)/Src binding, blocks the formation of α1 NKA/Src/reactive oxygen species (ROS) amplification loops and restores physiological ROS signaling in a number of oxidative disease models. The aim of this study was to evaluate the importance of the NKA/Src/ROS amplification loop and the effect of pNaKtide in experimental ischemic retinopathy. Methods: Human retinal microvascular endothelial cells (HRMECs) and retinal pigment epithelium (ARPE-19) cells were used to evaluate the effect of pNaKtide on viability, proliferation, and angiogenesis. Retinal toxicity and distribution were assessed in those cells and in the mouse. Subsequently, the role and molecular mechanism of NKA/Src in ROS stress signaling were evaluated biochemically in the retinas of mice exposed to the well-established protocol of oxygen-induced retinopathy (OIR). Finally, pNaKtide efficacy was assessed in this model. Results: The results suggest a key role of α1 NKA in the regulation of ROS stress and the Nrf2 pathway in mouse OIR retinas. Inhibition of α1 NKA/Src by pNaKtide reduced pathologic ROS signaling and restored normal expression of hypoxia-inducible factor 1-α/vascular endothelial growth factor (VEGF). Unlike anti-VEGF agents, pNaKtide did promote retinal revascularization while inhibiting neovascularization and inflammation. Conclusions: Targeting α1 NKA represents a novel strategy to develop therapeutics that not only inhibit neovascularization but also promote physiological revascularization in ischemic eye diseases.
Lužnik Z, Anchouche S, Dana R, Yin J. Regulatory T Cells in Angiogenesis. J Immunol 2020;205(10):2557-2565.Abstract
Regulatory T cells (Tregs) are crucial mediators of immune homeostasis. They regulate immune response by suppressing inflammation and promoting self-tolerance. In addition to their immunoregulatory role, a growing body of evidence highlights the dynamic role of Tregs in angiogenesis, the process of forming new blood vessels. Although angiogenesis is critically important for normal tissue regeneration, it is also a hallmark of pathological processes, including malignancy and chronic inflammation. Interestingly, the role of Tregs in angiogenesis has been shown to be highly tissue- and context-specific and as a result can yield either pro- or antiangiogenic effects. For these reasons, there is considerable interest in determining the molecular underpinnings of Treg-mediated modulation of angiogenesis in different disease states. The present review summarizes the role of Tregs in angiogenesis and mechanisms by which Tregs regulate angiogenesis and discusses how these mechanisms differ in homeostatic and pathological settings.
Steinberg E, Fluksman A, Zemmour C, Tischenko K, Karsch-Bluman A, Brill-Karniely Y, Birsner AE, D'Amato RJ, Benny O. Low dose amiodarone reduces tumor growth and angiogenesis. Sci Rep 2020;10(1):18034.Abstract
Amiodarone is an anti-arrhythmic drug that was approved by the US Food and Drug Administration (FDA) in 1985. Pre-clinical studies suggest that Amiodarone induces cytotoxicity in several types of cancer cells, thus making it a potential candidate for use as an anti-cancer treatment. However, it is also known to cause a variety of severe side effects. We hypothesized that in addition to the cytotoxic effects observed in cancer cells Amiodarone also has an indirect effect on angiogensis, a key factor in the tumor microenvironment. In this study, we examined Amiodarone's effects on a murine tumor model comprised of U-87 MG glioblastoma multiforme (GBM) cells, known to form highly vascularized tumors. We performed several in vitro assays using tumor and endothelial cells, along with in vivo assays utilizing three murine models. Low dose Amiodarone markedly reduced the size of GBM xenograft tumors and displayed a strong anti-angiogenic effect, suggesting dual cancer fighting properties. Our findings lay the ground for further research of Amiodarone as a possible clinical agent that, used in safe doses, maintains its dual properties while averting the drug's harmful side effects.
Bai J, Khajavi M, Sui L, Fu H, Krishnaji ST, Birsner AE, Bazinet L, Kamm RD, D'Amato RJ. Angiogenic responses in a 3D micro-engineered environment of primary endothelial cells and pericytes. Angiogenesis 2020;Abstract
Angiogenesis plays a key role in the pathology of diseases such as cancer, diabetic retinopathy, and age-related macular degeneration. Understanding the driving forces of endothelial cell migration and organization, as well as the time frame of these processes, can elucidate mechanisms of action of important pathological pathways. Herein, we have developed an organ-specific microfluidic platform recapitulating the in vivo angiogenic microenvironment by co-culturing mouse primary brain endothelial cells with brain pericytes in a three-dimensional (3D) collagen scaffold. As a proof of concept, we show that this model can be used for studying the angiogenic process and further comparing the angiogenic properties between two different common inbred mouse strains, C57BL/6J and 129S1/SvlmJ. We further show that the newly discovered angiogenesis-regulating gene Padi2 promotes angiogenesis through Dll4/Notch1 signaling by an on-chip mechanistic study. Analysis of the interplay between primary endothelial cells and pericytes in a 3D microfluidic environment assists in the elucidation of the angiogenic response.
Tomita Y, Shao Z, Cakir B, Kotoda Y, Fu Z, Smith LEH. An Ex Vivo Choroid Sprouting Assay of Ocular Microvascular Angiogenesis. J Vis Exp 2020;(162)Abstract
Pathological choroidal angiogenesis, a salient feature of age-related macular degeneration, leads to vision impairment and blindness. Endothelial cell (EC) proliferation assays using human retinal microvascular endothelial cells (HRMECs) or isolated primary retinal ECs are widely used in vitro models to study retinal angiogenesis. However, isolating pure murine retinal endothelial cells is technically challenging and retinal ECs may have different proliferation responses than choroidal endothelial cells and different cell/cell interactions. A highly reproducible ex vivo choroidal sprouting assay as a model of choroidal microvascular proliferation was developed. This model includes the interaction between choroid vasculature (EC, macrophages, pericytes) and retinal pigment epithelium (RPE). Mouse RPE/choroid/scleral explants are isolated and incubated in growth-factor-reduced basal membrane extract (BME) (day 0). Medium is changed every other day and choroid sprouting is quantified at day 6. The images of individual choroid explant are taken with an inverted phase microscope and the sprouting area is quantified using a semi-automated macro plug-in to the ImageJ software developed in this lab. This reproducible ex vivo choroidal sprouting assay can be used to assess compounds for potential treatment and for microvascular disease research to assess pathways involved in choroidal micro vessel proliferation using wild type and genetically modified mouse tissue.
Liu Z, Xu J, Ma Q, Zhang X, Yang Q, Wang L, Cao Y, Xu Z, Tawfik A, Sun Y, Weintraub NL, Fulton DJ, Hong M, Dong Z, Smith LEH, Caldwell RB, Sodhi A, Huo Y. Glycolysis links reciprocal activation of myeloid cells and endothelial cells in the retinal angiogenic niche. Sci Transl Med 2020;12(555)Abstract
The coordination of metabolic signals among different cellular components in pathological retinal angiogenesis is poorly understood. Here, we showed that in the pathological angiogenic vascular niche, retinal myeloid cells, particularly macrophages/microglia that are spatially adjacent to endothelial cells (ECs), are highly glycolytic. We refer to these macrophages/microglia that exhibit a unique angiogenic phenotype with increased expression of both M1 and M2 markers and enhanced production of both proinflammatory and proangiogenic cytokines as pathological retinal angiogenesis-associated glycolytic macrophages/microglia (PRAGMs). The phenotype of PRAGMs was recapitulated in bone marrow-derived macrophages or retinal microglia stimulated by lactate that was produced by hypoxic retinal ECs. Knockout of 6-phosphofructo-2-kinase/fructose-2, 6-bisphosphatase (; for rodents), a glycolytic activator in myeloid cells, impaired the ability of macrophages/microglia to acquire an angiogenic phenotype, rendering them unable to promote EC proliferation and sprouting and pathological neovascularization in a mouse model of oxygen-induced proliferative retinopathy. Mechanistically, hyperglycolytic macrophages/microglia produced large amount of acetyl-coenzyme A, leading to histone acetylation and PRAGM-related gene induction, thus reprogramming macrophages/microglia into an angiogenic phenotype. These findings reveal a critical role of glycolytic metabolites as initiators of reciprocal activation of macrophages/microglia and ECs in the retinal angiogenic niche and suggest that strategies targeting the metabolic communication between these cell types may be efficacious in the treatment of pathological retinal angiogenesis.
Tomita Y, Cakir B, Liu C-H, Fu Z, Huang S, Cho SS, Britton WR, Sun Y, Puder M, Hellström A, Talukdar S, Smith LEH. Free fatty acid receptor 4 activation protects against choroidal neovascularization in mice. Angiogenesis 2020;23(3):385-394.Abstract
To examine whether free fatty acid receptor 4 (FFAR4) activation can protect against choroidal neovascularization (CNV), which is a common cause of blindness, and to elucidate the mechanism underlying the inhibition, we used the mouse model of laser-induced CNV to mimic angiogenic aspects of age-related macular degeneration (AMD). Laser-induced CNV was compared between groups treated with an FFAR4 agonist or vehicle, and between FFAR4 wild-type (Ffar4) and knock out (Ffar4) mice on a C57BL/6J/6N background. The ex vivo choroid-sprouting assay, including primary retinal pigment epithelium (RPE) and choroid, without retina was used to investigate whether FFAR4 affects choroidal angiogenesis. Western blotting for pNF-ĸB/NF-ĸB and qRT-PCR for Il-6, Il-1β, Tnf-α, Vegf, and Nf-ĸb were used to examine the influence of FFAR4 on inflammation, known to influence CNV. RPE isolated from Ffar4 and Ffar4 mice were used to assess RPE contribution to inflammation. The FFAR4 agonist suppressed laser-induced CNV in C57BL/6J mice, and CNV increased in Ffar4 compared to Ffar4 mice. We showed that the FFAR4 agonist acted through the FFAR4 receptor. The FFAR4 agonist suppressed mRNA expression of inflammation markers (Il-6, Il-1β) via the NF-ĸB pathway in the retina, choroid, RPE complex. The FFAR4 agonist suppressed neovascularization in the choroid-sprouting ex vivo assay and FFAR4 deficiency exacerbated sprouting. Inflammation markers were increased in primary RPE cells of Ffar4 mice compared with Ffar4 RPE. In this mouse model, the FFAR4 agonist suppressed CNV, suggesting FFAR4 to be a new molecular target to reduce pathological angiogenesis in CNV.
Yanagida K, Engelbrecht E, Niaudet C, Jung B, Gaengel K, Holton K, Swendeman S, Liu CH, Levesque MV, Kuo A, Fu Z, Smith LEH, Betsholtz C, Hla T. Sphingosine 1-Phosphate Receptor Signaling Establishes AP-1 Gradients to Allow for Retinal Endothelial Cell Specialization. Dev Cell 2020;52(6):779-793.e7.Abstract
Transcriptional mechanisms that drive angiogenesis and organotypic vascular endothelial cell specialization are poorly understood. Here, we show that retinal endothelial sphingosine 1-phosphate receptors (S1PRs), which restrain vascular endothelial growth factor (VEGF)-induced angiogenesis, spatially restrict expression of JunB, a member of the activator protein 1 (AP-1) family of transcription factors (TFs). Mechanistically, VEGF induces JunB expression at the sprouting vascular front while S1PR-dependent vascular endothelial (VE)-cadherin assembly suppresses JunB expression in the nascent vascular network, thus creating a gradient of this TF. Endothelial-specific JunB knockout mice showed diminished expression of neurovascular guidance genes and attenuated retinal vascular network progression. In addition, endothelial S1PR signaling is required for normal expression of β-catenin-dependent genes such as TCF/LEF1 and ZIC3 TFs, transporters, and junctional proteins. These results show that S1PR signaling restricts JunB function to the expanding vascular front, thus creating an AP-1 gradient and enabling organotypic endothelial cell specialization of the vascular network.
Wu W, Zhou G, Han H, Huang X, Jiang H, Mukai S, Kazlauskas A, Cui J, Matsubara JA, Vanhaesebroeck B, Xia X, Wang J, Lei H. PI3Kδ as a Novel Therapeutic Target in Pathological Angiogenesis. Diabetes 2020;69(4):736-748.Abstract
Diabetic retinopathy is the most common microvascular complication of diabetes, and in the advanced diabetic retinopathy appear vitreal fibrovascular membranes that consist of a variety of cells, including vascular endothelial cells (ECs). New therapeutic approaches for this diabetic complication are urgently needed. Here, we report that in cultured human retinal microvascular ECs, high glucose induced expression of p110δ, which was also expressed in ECs of fibrovascular membranes from patients with diabetes. This catalytic subunit of a receptor-regulated PI3K isoform δ is known to be highly enriched in leukocytes. Using genetic and pharmacological approaches, we show that p110δ activity in cultured ECs controls Akt activation, cell proliferation, migration, and tube formation induced by vascular endothelial growth factor, basic fibroblast growth factor, and epidermal growth factor. Using a mouse model of oxygen-induced retinopathy, p110δ inactivation was found to attenuate pathological retinal angiogenesis. p110δ inhibitors have been approved for use in human B-cell malignancies. Our data suggest that antagonizing p110δ constitutes a previously unappreciated therapeutic opportunity for diabetic retinopathy.