Sequence- and target-independent angiogenesis suppression by siRNA via TLR3.
ABSTRACT: Clinical trials of small interfering RNA (siRNA) targeting vascular endothelial growth factor-A (VEGFA) or its receptor VEGFR1 (also called FLT1), in patients with blinding choroidal neovascularization (CNV) from age-related macular degeneration, are premised on gene silencing by means of intracellular RNA interference (RNAi). We show instead that CNV inhibition is a siRNA-class effect: 21-nucleotide or longer siRNAs targeting non-mammalian genes, non-expressed genes, non-genomic sequences, pro- and anti-angiogenic genes, and RNAi-incompetent siRNAs all suppressed CNV in mice comparably to siRNAs targeting Vegfa or Vegfr1 without off-target RNAi or interferon-alpha/beta activation. Non-targeted (against non-mammalian genes) and targeted (against Vegfa or Vegfr1) siRNA suppressed CNV via cell-surface toll-like receptor 3 (TLR3), its adaptor TRIF, and induction of interferon-gamma and interleukin-12. Non-targeted siRNA suppressed dermal neovascularization in mice as effectively as Vegfa siRNA. siRNA-induced inhibition of neovascularization required a minimum length of 21 nucleotides, a bridging necessity in a modelled 2:1 TLR3-RNA complex. Choroidal endothelial cells from people expressing the TLR3 coding variant 412FF were refractory to extracellular siRNA-induced cytotoxicity, facilitating individualized pharmacogenetic therapy. Multiple human endothelial cell types expressed surface TLR3, indicating that generic siRNAs might treat angiogenic disorders that affect 8% of the world's population, and that siRNAs might induce unanticipated vascular or immune effects.
Project description:Neovascularization in response to tissue injury consists of the dual invasion of blood (hemangiogenesis) and lymphatic (lymphangiogenesis) vessels. We reported recently that 21-nt or longer small interfering RNAs (siRNAs) can suppress hemangiogenesis in mouse models of choroidal neovascularization and dermal wound healing independently of RNA interference by directly activating Toll-like receptor 3 (TLR3), a double-stranded RNA immune receptor, on the cell surface of blood endothelial cells. Here, we show that a 21-nt nontargeted siRNA suppresses both hemangiogenesis and lymphangiogenesis in mouse models of neovascularization induced by corneal sutures or hindlimb ischemia as efficiently as a 21-nt siRNA targeting vascular endothelial growth factor-A. In contrast, a 7-nt nontargeted siRNA, which is too short to activate TLR3, does not block hemangiogenesis or lymphangiogenesis in these models. Exposure to 21-nt siRNA, which we demonstrate is not internalized unless cell-permeating moieties are used, triggers phosphorylation of cell surface TLR3 on lymphatic endothelial cells and induces apoptosis. These findings introduce TLR3 activation as a method of jointly suppressing blood and lymphatic neovascularization and simultaneously raise new concerns about the undesirable effects of siRNAs on both circulatory systems.
Project description:RNA interference (RNAi) has become a powerful tool for suppressing gene expression in vitro and in vivo. A great deal of evidence has demonstrated the potential for the use of synthetic small interfering RNAs (siRNAs) as therapeutic agents. However, the application of siRNA to clinical medicine is still limited, mainly due to sequence-independent suppression of angiogenesis mediated by Toll-like receptor 3 (TLR3). Here, we describe novel types of synthetic RNA, named nkRNA and PnkRNA, that exhibit sequence-specific gene silencing through RNAi without activating TLRs or RIG-I-like receptor signaling. In addition, we confirmed the therapeutic effect for the novel types of RNA in an animal model of age-related macular degeneration (AMD) without retinal degeneration. These data indicate that nkRNA and PnkRNA are of great potential utility as therapies against blinding choroidal neovascularization due to AMD.
Project description:Many patients with wet age-related macular degeneration do not respond well to anti- vascular endothelial growth factor A (VEGFA) therapy for choroidal neovascularization (CNV), and the efficacy of anti-VEGFA decreases over time. We investigated the hypothesis that fibrotic changes, in particular via endothelial-to-mesenchymal transition (EndoMT), play a role in CNV and alter the therapeutic effects of VEGFA pathway blockage. Induction of EndoMT of primary human retinal endothelial cells led to a significantly reduced response to VEGFA at the level of gene expression, cellular proliferation, migration, and tube formation. Suppression of EndoMT restored cell responsiveness to VEGFA. In a mouse model of spontaneous CNV, fibrotic changes and EndoMT persisted as the CNV lesions became more established over time. VEGFA receptor-2 (VEGFR2) antagonism further induced fibrosis and EndoMT in the CNV. The combination of VEGFR2 antagonism and fibrosis/EndoMT inhibition was more effective than either individual treatment in reducing CNV. Our data indicate that fibrosis and EndoMT are involved in the progression of CNV, are exacerbated by VEGFR2 inhibition, and could provide an explanation for the reduced efficacy of anti-VEGFA treatment over time.
Project description:Although blocking VEGF has a positive effect in wet age-related macular degeneration (AMD), the effect of blocking its receptors remains unclear. This was an investigation of the effect of VEGF receptor (VEGFR) 1 and/or 2 blockade on retinal microglia/macrophage infiltration in laser-induced choroidal neovascularization (CNV), a model of wet AMD. CNV lesions were isolated by laser capture microdissection at 3, 7, and 14 days after laser and analyzed by RT-PCR and immunofluorescence staining for mRNA and protein expression, respectively. Neutralizing antibodies for VEGFR1 or R2 and the microglia inhibitor minocycline were injected intraperitoneally (IP). Anti-CD11b, CD45 and Iba1 antibodies were used to confirm the cell identity of retinal microglia/macrophage, in the RPE/choroidal flat mounts or retinal cross sections. CD11b(+), CD45(+) or Iba1(+) cells were counted. mRNA of VEGFR1 and its three ligands, PlGF, VEGF-A (VEGF) and VEGF-B, were expressed at all stages, but VEGFR2 were detected only in the late stage. PlGF and VEGF proteins were expressed at 3 and 7 days after laser. Anti-VEGFR1 (MF1) delivered IP 3 days after laser inhibited infiltration of leukocyte populations, largely retinal microglia/macrophage to CNV, while anti-VEGFR2 (DC101) had no effect. At 14 days after laser, both MF1 and DC101 antibodies markedly inhibited retinal microglia/macrophage infiltration into CNV. Therefore, VEGFR1 and R2 play differential roles in the pathogenesis of CNV: VEGFR1 plays a dominant role at 3 days after laser; but both receptors play pivotal roles at 14 days after laser. In vivo imaging demonstrated accumulation of GFP-expressing microglia into CNV in both CX3CR1(gfp/gfp) and CX3CR1(gfp/+) mice. Minocycline treatment caused a significant increase in lectin(+) cells in the sub-retinal space anterior to CNV and a decrease in dextran-perfused neovessels compared to controls. Targeting the chemoattractant molecules that regulate trafficking of retinal microglia/macrophage appears to be a compelling therapeutic strategy to control CNV and treat wet AMD.
Project description:Rationale: Choroidal neovascularization (CNV) is a major cause of severe vision loss and occurs in many ocular diseases, especially neovascular age-related macular degeneration (nAMD). Circular RNAs (circRNAs) are emerging as a new class of endogenous noncoding RNAs, which have been implicated in the regulation of endothelial cell dysfunction in diabetes mellitus and cancer. In this study, we aimed to determine the role of circRNA-ZBTB44 (cZBTB44) in the pathogenesis of CNV. Methods: Quantitative polymerase chain reaction was conducted to detect cZBTB44 expression pattern during CNV development. Isolectin B4 staining, hematoxylin and eosin (HE) staining, and choroidal sprouting assay ex vivo were conducted to evaluate the role of cZBTB44 in the development of CNV. Endothelial cell proliferation, migration and tube formation assays were conducted to determine the role of cZBTB44 in angiogenic effect in vitro. Bioinformatics analysis, RNA immunoprecipitation assay, luciferase assay, and in vitro studies were conducted to investigate the mechanism of cZBTB44-mediated CNV development. Results: cZBTB44 expression was significantly up-regulated in a laser-induced CNV mouse model in vivo and in endothelial cells upon hypoxia stress in vitro. cZBTB44 silencing retarded CNV development, while overexpression of cZBTB44 showed the opposite effects. The role of cZBTB44 in CNV development was confirmed in choroidal sprouting assay ex vivo. cZBTB44 silencing reduced endothelial cell viability, proliferation, migration and tube formation in vitro. cZBTB44 acted as miR-578 sponge to sequester and inhibit miR-578 activity, which led to increased expression of vascular endothelial growth factor A (VEGFA) and vascular cell adhesion molecule-1 (VCAM1). Overexpression of miR-578 mimicked cZBTB44 silencing-mediated anti-angiogenic effects in vivo and in vitro. Furthermore, dysregulated cZBTB44 expression was detected in the clinical samples of nAMD patients. Conclusions: This study provided novel insights into the molecular pathogenesis of CNV. The cZBTB44-miR-578-VEGFA/VCAM1 axis might be a potential source of novel therapeutic targets for neovascularization-related diseases.
Project description:Vascular endothelial growth factor A (VEGFA) is involved in the pathogenesis of vasoproliferative retinal diseases, such as exudative age-related macular degeneration (AMD). The objective of this study was to investigate whether dual-acting therapy based on the simultaneous expression of anti-VEGFA microRNAs (miRNAs) and the secreted, antiangiogenic protein pigment endothelial-derived factor (PEDF) delivered by adeno-associated virus (AAV) vectors provides improved protection against choroidal neovascularization (CNV). To investigate this, a multigenic AAV vector allowing retina pigment epithelium (RPE)-specific expression of anti-VEGFA miRNAs and PEDF was engineered. Robust expression of PEDF, driven by the RPE-specific vitelliform macular dystrophy 2 promoter, was observed in human cells and in mouse retina. A significant reduction in CNV was observed in a laser-induced CNV mouse model 57 days post-injection of the AAV5 particles conveying either anti-VEGFA miRNA and PEDF dual therapy or anti-VEGFA miRNA monotherapy. Overall, CNV reduction was most prominent in animals receiving dual-acting therapy. In both cases, the reduction in CNV was accompanied by a significant attenuation of VEGFA. In conclusion, the presented data reveal that gene therapy targeting VEGFA via multigenic AAV vectors displays combined efficacy, suggesting that dual-acting therapy is an important tool in future eye gene therapy for the treatment of neovascular ocular diseases, including AMD.
Project description:Background:Age-related macular degeneration (AMD), the most common cause of blindness in the developed world, usually affects individuals older than 60 years of age. The majority of visual loss in this disease is attributable to the development of choroidal neovascularization (CNV). Mononuclear phagocytes, including monocytes and their tissue descendants, macrophages, have long been implicated in the pathogenesis of neovascular AMD (nvAMD). Current therapies for nvAMD are based on targeting vascular endothelial growth factor (VEGF). This study is aimed at assessing if perturbation of chemokine signaling and mononuclear cell recruitment may serve as novel complementary therapeutic targets for nvAMD. Methods:A promiscuous chemokine antagonist (BKT130), aflibercept treatment, or combined BKT130+aflibercept treatment was tested in an in vivo laser-induced model of choroidal neovascularization (LI-CNV) and in an ex vivo choroidal sprouting assay (CSA). Quantification of CD11b+ cell in the CNV area was performed, and mRNA levels of genes implicated in CNV growth were measured in the retina and RPE-choroid. Results:BKT130 reduced the CNV area and recruitment of CD11b+ cells by 30-35%. No effect of BKT130 on macrophages' proangiogenic phenotype was demonstrated ex vivo, but a lower VEGFA and CCR2 expression was found in the RPE-choroid and a lower expression of TNF? and NOS1 was found in both RPE-choroid and retinal tissues in the LI-CNV model under treatment with BKT130. Conclusions:Targeting monocyte recruitment via perturbation of chemokine signaling can reduce the size of experimental CNV and should be evaluated as a potential novel therapeutic modality for nvAMD.
Project description:The discovery of sequence-specific gene silencing by endogenous double-stranded RNAs (dsRNA) has propelled synthetic short-interfering RNAs (siRNAs) to the forefront of targeted pharmaceutical engineering. The first clinical trials utilized 21-nucleotide (nt) siRNAs for the treatment of neovascular age-related macular degeneration (AMD). Surprisingly, these compounds were not formulated for cell permeation, which is required for bona fide RNA interference (RNAi). We showed that these "naked" siRNAs suppress neovascularization in mice not via RNAi but via sequence-independent activation of cell surface Toll-like receptor-3 (TLR3). Here, we demonstrate that noninternalized siRNAs induce retinal degeneration in mice by activating surface TLR3 on retinal pigmented epithelial cells. Cholesterol conjugated siRNAs capable of cell permeation and triggering RNAi also induce the same phenotype. Retinal degeneration was not observed after treatment with siRNAs shorter than 21-nts. Other cytosolic dsRNA sensors are not critical to this response. TLR3 activation triggers caspase-3-mediated apoptotic death of the retinal pigment epithelium (RPE) via nuclear translocation of interferon regulatory factor-3. While this unexpected adverse effect of siRNAs has implications for future clinical trials, these findings also introduce a new preclinical model of geographic atrophy (GA), a late stage of dry AMD that causes blindness in millions worldwide.
Project description:Choroidal neovascularization (CNV) is aberrant angiogenesis associated with exudative age-related macular degeneration (AMD), a leading cause of blindness in the elderly. Inflammation has been suggested as a risk factor for AMD. The IKK2/NF-?B pathway plays a key role in the inflammatory response through regulation of the transcription of cytokines, chemokines, growth factors and angiogenic factors. We investigated the functional role of IKK2 in development of the laser-induced CNV using either Ikk2 conditional knockout mice or an IKK2 inhibitor. The retinal neuronal tissue and RPE deletion of IKK2 was generated by breeding Ikk2(-/flox) mice with Nestin-Cre mice. Deletion of Ikk2 in the retina caused no obvious defect in retinal development or function, but resulted in a significant reduction in laser-induced CNV. In addition, intravitreal or retrobulbar injection of an IKK2 specific chemical inhibitor, TPCA-1, also showed similar inhibition of CNV. Furthermore, in vitro inhibition of IKK2 in ARPE-19 cells significantly reduced heat shock-induced expression of NFKBIA, IL1B, CCL2, VEGFA, PDGFA, HIF1A, and MMP-2, suggesting that IKK2 may regulate multiple molecular pathways involved in laser-induced CNV. The in vivo laser-induced expression of VEGFA, and HIF1A in RPE and choroidal tissue was also blocked by TPCA-1 treatment. Thus, IKK2/NF-?B signaling appears responsible for production of pro-inflammatory and pro-angiogenic factors in laser-induced CNV, suggesting that this intracellular pathway may serve as an important therapeutic target for aberrant angiogenesis in exudative AMD.
Project description:Macrophages are rapidly conditioned by cognate and soluble signals to acquire phenotypes that deliver specific functions during inflammation, wound healing and angiogenesis. Whether inhibitory CD200R signaling regulates pro-angiogenic macrophage phenotypes with the potential to suppress ocular neovascularization is unknown. CD200R-deficient bone marrow derived macrophages (BMM?) were used to demonstrate that macrophages lacking this inhibitory receptor exhibit enhanced levels of Vegfa, Arg-1 and Il-1? when stimulated with PGE2 or RPE-conditioned (PGE2-enriched) media. Endothelial tube formation in HUVECs was increased when co-cultured with PGE2-conditioned CD200R(-/-) BMM?, and laser-induced choroidal neovascularization was enhanced in CD200R-deficient mice. In corroboration, signaling through CD200R results in the down-regulation of BMM? angiogenic and pro-inflammatory phenotypes. Translational potential of this pathway was investigated in the laser-induced model of choroidal neovascularization. Local delivery of a CD200R agonist mAb to target myeloid infiltrate alters macrophage phenotype and inhibits pro-angiogenic gene expression, which suppresses pathological angiogenesis and CNV development.