Adeno-associated viral vector-mediated vascular endothelial growth factor gene transfer induces neovascular formation in ischemic heart

Nanotechnology: The Future for Diagnostic and Therapeutic Intervention in Cardiovascular Diseases is Here

With advances in technology and medicine over the last 3 decades, cardiovascular medicine has evolved tremendously. Nanotechnology provides a promising future in personalized precision medicine. In this review, we delve into the current and prospective applications of nanotechnology and nanoparticles in cardiology. Nanotechnology has allowed for point-of-care testing such as high-sensitivity troponins, as well as more precise cardiac imaging. This review is focused on 3 diseases within cardiology: coronary artery disease, heart failure, and valvular heart disease. The use of nanoparticles in coronary stents has shown success in preventing in-stent thrombosis, as well as using nanosized drug delivery medications to prevent neointimal proliferation in a way that spares systemic toxicity. In addition, by using nanoparticles as drug delivery systems, nanotechnology can be utilized in the delivery of goal-directed medical therapy in heart failure patients. It has also been shown to improve cell therapy in this patient population by helping in cell retention of grafts. Finally, the use of nanoparticles in the manufacturing of bioprosthetic valves provides a promising future for the longevity and success of cardiac valve repair and replacement.

Contribution of VEGF-B-Induced Endocardial Endothelial Cell Lineage in Physiological Versus Pathological Cardiac Hypertrophy

BACKGROUND

Preclinical studies have shown the therapeutic potential of VEGF-B (vascular endothelial growth factor B) in revascularization of the ischemic myocardium, but the associated cardiac hypertrophy and adverse side effects remain a concern. To understand the importance of endothelial proliferation and migration for the beneficial versus adverse effects of VEGF-B in the heart, we explored the cardiac effects of autocrine versus paracrine VEGF-B expression in transgenic and gene-transduced mice.

METHODS

We used single-cell RNA sequencing to compare cardiac endothelial gene expression in VEGF-B transgenic mouse models. Lineage tracing was used to identify the origin of a VEGF-B-induced novel endothelial cell population and adeno-associated virus-mediated gene delivery to compare the effects of VEGF-B isoforms. Cardiac function was investigated using echocardiography, magnetic resonance imaging, and micro-computed tomography.

RESULTS

Unlike in physiological cardiac hypertrophy driven by a cardiomyocyte-specific VEGF-B transgene (myosin heavy chain alpha-VEGF-B), autocrine VEGF-B expression in cardiac endothelium (aP2 [adipocyte protein 2]-VEGF-B) was associated with septal defects and failure to increase perfused subendocardial capillaries postnatally. Paracrine VEGF-B led to robust proliferation and myocardial migration of a novel cardiac endothelial cell lineage (VEGF-B-induced endothelial cells) of endocardial origin, whereas autocrine VEGF-B increased proliferation of VEGF-B-induced endothelial cells but failed to promote their migration and efficient contribution to myocardial capillaries. The surviving aP2-VEGF-B offspring showed an altered ratio of secreted VEGF-B isoforms and developed massive pathological cardiac hypertrophy with a distinct cardiac vessel pattern. In the normal heart, we found a small VEGF-B-induced endothelial cell population that was only minimally expanded during myocardial infarction but not during physiological cardiac hypertrophy associated with mouse pregnancy.

CONCLUSIONS

Paracrine and autocrine secretions of VEGF-B induce expansion of a specific endocardium-derived endothelial cell population with distinct angiogenic markers. However, autocrine VEGF-B signaling fails to promote VEGF-B-induced endothelial cell migration and contribution to myocardial capillaries, predisposing to septal defects and inducing a mismatch between angiogenesis and myocardial growth, which results in pathological cardiac hypertrophy.

The Transcription Factor EB (TFEB) Sensitizes the Heart to Chronic Pressure Overload

The transcription factor EB (TFEB) promotes protein degradation by the autophagy and lysosomal pathway (ALP) and overexpression of TFEB was suggested for the treatment of ALP-related diseases that often affect the heart. However, TFEB-mediated ALP induction may perturb cardiac stress response. We used adeno-associated viral vectors type 9 (AAV9) to overexpress TFEB (AAV9-Tfeb) or Luciferase-control (AAV9-Luc) in cardiomyocytes of 12-week-old male mice. Mice were subjected to transverse aortic constriction (TAC, 27G; AAV9-Luc: n = 9; AAV9-Tfeb: n = 14) or sham (AAV9-Luc: n = 9; AAV9-Tfeb: n = 9) surgery for 28 days. Heart morphology, echocardiography, gene expression, and protein levels were monitored. AAV9-Tfeb had no effect on cardiac structure and function in sham animals. TAC resulted in compensated left ventricular hypertrophy in AAV9-Luc mice. AAV9-Tfeb TAC mice showed a reduced LV ejection fraction and increased left ventricular diameters. Morphological, histological, and real-time PCR analyses showed increased heart weights, exaggerated fibrosis, and higher expression of stress markers and remodeling genes in AAV9-Tfeb TAC compared to AAV9-Luc TAC. RNA-sequencing, real-time PCR and Western Blot revealed a stronger ALP activation in the hearts of AAV9-Tfeb TAC mice. Cardiomyocyte-specific TFEB-overexpression promoted ALP gene expression during TAC, which was associated with heart failure. Treatment of ALP-related diseases by overexpression of TFEB warrants careful consideration.

Combined gene therapy via VEGF and mini-dystrophin synergistically improves pathologies in temporalis muscle of dystrophin/utrophin double knockout mice

Duchenne muscular dystrophy (DMD) is a severe X-linked inherited muscular disorder characterized by the loss of dystrophin. We have previously shown that monogene therapy using the mini-dystrophin gene improves muscle function in DMD. However, chronic inflammation plays an important role in progressive muscle degeneration in DMD as well. Vascular endothelial growth factor (VEGF) has been used to enhance muscle vasculature, reduce local inflammation and improve DMD muscle function. Temporalis muscles are the key skeletal muscles for mastication and loss of their function negatively affects DMD patient quality of life by reducing nutritional intake, but little is known about the pathology and treatment of the temporalis muscle in DMD. In this work, we tested the hypothesis that the combined delivery of the human mini-dystrophin and human VEGF genes to the temporalis muscles using separate recombinant adeno-associated viral (rAAV) vectors will synergistically improve muscle function and pathology in adult male dystrophin/utrophin double-knockout (mdx/utrn+/-) mice. The experimental mice were divided into four groups including: dystrophin + VEGF combined, dystrophin only, VEGF only and PBS control. After 2 months, gene expression and histological analysis of the temporalis muscles showed a synergistic improvement in temporalis muscle pathology and function coincident with increased restoration of dystrophin-associated protein complexes and nNOS in the dystrophin + VEGF combined group. We also observed significantly reduced inflammatory cell infiltration, central nucleation, and fibrosis in the dystrophin + VEGF combined group. We have demonstrated the efficacy of combined rAAV-mediated dystrophin and VEGF treatment of temporalis muscles in a DMD mouse model.

Sialyltransferase7A promotes angiotensin II-induced cardiomyocyte hypertrophy via HIF-1α-TAK1 signalling pathway

AIMS

Sialylation is up-regulated during the development of cardiac hypertrophy. Sialyltransferase7A (Siat7A) mRNA is consistently over-expressed in the hypertrophic left ventricle of hypertensive rats independently of genetic background. The aims of this study were: (i) to detect the Siat7A protein levels and its roles in the pathological cardiomyocyte hypertrophy; (ii) to elucidate the effect of sialylation mediated by Siat7A on the transforming-growth-factor-β-activated kinase (TAK1) expression and activity in cardiomyocyte hypertrophy; and (iii) to clarify hypoxia-inducible factor 1 (HIF-1) expression was regulated by Siat7A and transactivated TAK1 expression in cardiomyocyte hypertrophy.

METHODS AND RESULTS

Siat7A protein level was increased in hypertrophic cardiomyocytes of human and rats subjected to chronic infusion of angiotensin II (ANG II). Delivery of adeno-associated viral (AAV9) bearing shRNA against rat Siat7A into the left ventricular wall inhibited ventricular hypertrophy. Cardiac-specific Siat7A overexpression via intravenous injection of an AAV9 vector encoding Siat7A under the cardiac troponin T (cTNT) promoter aggravated cardiac hypertrophy in ANG II-treated rats. In vitro, Siat7A knockdown inhibited the induction of Sialyl-Tn (sTn) antigen and cardiomyocyte hypertrophy stimulated by ANG II. Mechanistically, ANG II induced the activation of TAK1-nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) signalling in parallel to up-regulation of Siat7A in hypertrophic cardiomyocytes. Siat7A knockdown inhibited activation of TAK1-NF-κB pathway. Interestingly, HIF-1α expression was increased in cardiomyocytes stimulated by ANG II but decreased after Siat7A knockdown. HIF-1α knockdown efficiently decreased TAK1 expression. ChIP and luciferase assays showed that HIF-1α transactivated the TAK1 promoter region (nt -1285 to -1274 bp) in the cardiomyocytes following ANG II stimulus.

CONCLUSION

Siat7A was up-regulated in hypertrophic myocardium and promoted cardiomyocyte hypertrophy via activation of the HIF-1α-TAK1-NF-κB pathway.

Acute mechanical stress in primary porcine RPE cells induces angiogenic factor expression and in vitro angiogenesis

Background

Choroidal neovascularization (CNV) is a major cause of blindness in patients with age-related macular degeneration. CNV is characterized by new blood vessel growth and subretinal fluid accumulation, which results in mechanical pressure on retinal pigment epithelial (RPE) cells. The overexpression of RPE-derived angiogenic factors plays an important role in inducing CNV. In this work, we investigated the effect of mechanical stress on the expression of angiogenic factors in porcine RPE cells and determined the impact of conditioned medium on in-vitro angiogenesis.

Results

The goal of this study was to determine whether low levels of acute mechanical stress during early CNV can induce the expression of angiogenic factors in RPE cells and accelerate angiogenesis. Using a novel device, acute mechanical stress was applied to primary porcine RPE cells and the resulting changes in the expression of major angiogenic factors, VEGF, ANG2, HIF-1α, IL6, IL8 and TNF-α, were examined using immunocytochemistry, qRT-PCR, and ELISA. An in vitro tube formation assay was used to determine the effect of secreted angiogenic proteins due to mechanical stress on endothelial tube formation by human umbilical vein endothelial cells (HUVECs). Our results showed an increase in the expression of VEGF, ANG2, IL-6 and IL-8 in response to mechanical stress, resulting in increased in vitro angiogenesis. Abnormal epithelial-mesenchymal transition (EMT) in RPE cells is also associated with CNV and further retinal degeneration. Our qRT-PCR results verified an increase in the expression of EMT genes, CDH2, VIM and FN1, in RPE cells.

Conclusions

In conclusion, we showed that acute mechanical stress induces the expression of major angiogenic and EMT factors and promotes in vitro angiogenesis, suggesting that mechanical stress plays a role in promoting aberrant angiogenesis in AMD.

Effect of elevation of vascular endothelial growth factor level on exacerbation of hemorrhage in mouse brain arteriovenous malformation

OBJECTIVE

A high level of vascular endothelial growth factor (VEGF) has been implicated in brain arteriovenous malformation (bAVM) bleeding and rupture. However, direct evidence is missing. In this study the authors used a mouse bAVM model to test the hypothesis that elevation of focal VEGF levels in bAVMs exacerbates the severity of bAVM hemorrhage.

METHODS

Brain AVMs were induced in adult mice in which activin receptor-like kinase 1 (Alk1, a gene that causes AVM) gene exons 4-6 were floxed by intrabasal ganglia injection of an adenoviral vector expressing Cre recombinase to induce Alk1 mutation and an adeno-associated viral vector expressing human VEGF (AAV-VEGF) to induce angiogenesis. Two doses of AAV-VEGF (5 × 109 [high] or 2 × 109 [low]) viral genomes were used. In addition, the common carotid artery and external jugular vein were anastomosed in a group of mice treated with low-dose AAV-VEGF 6 weeks after the model induction to induce cerebral venous hypertension (VH), because VH increases the VEGF level in the brain. Brain samples were collected 8 weeks after the model induction. Hemorrhages in the bAVM lesions were quantified on brain sections stained with Prussian blue, which detects iron deposition. VEGF levels were quantified in bAVM tissue by enzyme-linked immunosorbent assay.

RESULTS

Compared to mice injected with a low dose of AAV-VEGF, the mice injected with a high dose had higher levels of VEGF (p = 0.003) and larger Prussian blue-positive areas in the bAVM lesion at 8 or 9 weeks after model induction (p = 0.002). VH increased bAVM hemorrhage in the low-dose AAV-VEGF group. The overall mortality in the high-dose AAV-VEGF group was 26.7%, whereas no mouse died in the low-dose AAV-VEGF group without VH. In contrast, VH caused a mortality of 50% in the low-dose AAV-VEGF group.

CONCLUSIONS

Using mouse bAVM models, the authors provided direct evidence that elevation of the VEGF level increases bAVM hemorrhage and mouse mortality.

Nanoscale Technologies for Prevention and Treatment of Heart Failure: Challenges and Opportunities

The adult myocardium has a limited regenerative capacity following heart injury, and the lost cells are primarily replaced by fibrotic scar tissue. Suboptimal efficiency of current clinical therapies to resurrect the infarcted heart results in injured heart enlargement and remodeling to maintain its physiological functions. These remodeling processes ultimately leads to ischemic cardiomyopathy and heart failure (HF). Recent therapeutic approaches (e.g., regenerative and nanomedicine) have shown promise to prevent HF postmyocardial infarction in animal models. However, these preclinical, clinical, and technological advancements have yet to yield substantial enhancements in the survival rate and quality of life of patients with severe ischemic injuries. This could be attributed largely to the considerable gap in knowledge between clinicians and nanobioengineers. Development of highly effective cardiac regenerative therapies requires connecting and coordinating multiple fields, including cardiology, cellular and molecular biology, biochemistry and chemistry, and mechanical and materials sciences, among others. This review is particularly intended to bridge the knowledge gap between cardiologists and regenerative nanomedicine experts. Establishing this multidisciplinary knowledge base may help pave the way for developing novel, safer, and more effective approaches that will enable the medical community to reduce morbidity and mortality in HF patients.

Tongxinluo Improves Apolipoprotein E-Deficient Mouse Heart Function

Background:

Our previous studies have shown that Tongxinluo (TXL), a compound Chinese medicine, can decrease myocardial ischemia-reperfusion injury, protect capillary endothelium function, and lessen cardiac ventricle reconstitution in animal models. The aim of this study was to illuminate whether TXL can improve hypercholesterolemia-impaired heart function by protecting artery endothelial function and increasing microvascular density (MVD) in heart. Furthermore, we will explore the underlying molecular mechanism of TXL cardiovascular protection.

Methods:

After intragastric administration of TXL (0.1 ml/10 g body weight) to C57BL/6J wild-type mice (n = 8) and ApoE-/- mice (n = 8), total cholesterol, high-density lipoprotein-cholesterol, very-low-density lipoprotein (VLDL)-cholesterol, triglyceride, and blood glucose levels in serum were measured. The parameters of heart rate (HR), left ventricular diastolic end diameter, and left ventricular systolic end diameter were harvested by ultrasonic cardiogram. The left ventricular ejection fraction, stroke volume, cardiac output, and left ventricular fractional shortening were calculated. Meanwhile, aorta peak systolic flow velocity (PSV), end diastolic flow velocity, and mean flow velocity (MFV) were measured. The pulsatility index (PI) and resistant index were calculated in order to evaluate the vascular elasticity and resistance. The endothelium-dependent vasodilatation was evaluated by relaxation of aortic rings in response to acetylcholine. Western blotting and real-time quantitative reverse transcription polymerase chain reaction were performed for protein and gene analyses of vascular endothelial growth factor (VEGF). Immunohistochemical detection was performed for myocardial CD34 expression. Data in this study were compared by one-way analysis of variance between groups. A value of P < 0.05 was considered statistically significant.

Results:

Although there was no significant decrease of cholesterol level (F = 2.300, P = 0.240), TXL inhibited the level of triglyceride and VLDL (F = 9.209, P = 0.024 and F = 9.786, P = 0.020, respectively) in ApoE-/- mice. TXL improved heart function of ApoE-/- mice owing to the elevations of LVEF, SV, CO, and LVFS (all P < 0.05). TXL enhanced aortic PSV and MFV (F = 10.774, P = 0.024 and F = 11.354, P = 0.020, respectively) and reduced PI of ApoE-/- mice (1.41 ± 0.17 vs. 1.60 ± 0.17; P = 0.037). After incubation with 10 μmol/L acetylcholine, the ApoE-/- mice treated with TXL aortic segment relaxed by 44% ± 3%, significantly higher than control group mice (F = 9.280, P = 0.040). TXL also restrain the angiogenesis of ApoE-/- mice aorta (F = 21.223, P = 0.010). Compared with C57BL/6J mice, the MVD was decreased in heart tissue of untreated ApoE-/- mice (54.0 ± 3.0/mm²vs. 75.0 ± 2.0/mm²; F = 16.054, P = 0.010). However, TXL could significantly enhance MVD (65.0 ± 5.0/mm²vs. 54.0 ± 3.0/mm²; F = 11.929, P = 0.020) in treated ApoE-/- mice. In addition, TXL obviously increased the expression of VEGF protein determined by Western blot (F = 20.247, P = 0.004).

Conclusions:

TXL obviously improves the ApoE-/- mouse heart function from different pathways, including reduces blood fat to lessen atherosclerosis; enhances aortic impulsivity, blood supply capacity, and vessel elasticity; improves endothelium-dependent vasodilatation; restraines angiogenesis of aorta-contained plaque; and enhances MVD of heart. The molecular mechanism of MVD enhancement maybe relate with increased VEGF expression.

Impact of G-CSF on expressions of Egr-1 and VEGF in acute ischemic cerebral injury

The aim of the present study was to investigate the protective effect of granulocyte colony-stimulating factor (G-CSF) on acute ischemic cerebral injury, and its mechanism through the impact of G-CSF on early growth response-1 (Egr-1) and vascular endothelial growth factor (VEGF) expressions. Male Sprague-Dawley (SD) rats were divided them into three groups, i.e., the sham, model and G-CSF groups to measure the effect of G-CSF on the volume of cerebral infarction and level of lactate dehydrogenase (LDH) in rats. Hematoxylin and eosin (H&E) staining method was performed for histopathological examination. Reverse transcription-polymerase chain reaction (RT-PCR) and western blot analysis were used to detect the mRNA and protein expressions of Egr-1 and VEGF in different groups. Furthermore, Statistical Product and Service Solutions (SPSS) 17.0 software was applied to detect the differences in the expression of Egr-1 and VEGF between the two groups. Compared with the sham group, we found that the volume of cerebral infarction and LDH content in the model group were significantly elevated. By contrast, in the model group, those indicators in the G-CSF group were obviously decreased. H&E staining results also showed that G-CSF could decrease the necrotic area in cerebral infarction and the incidence of inflammation, and sustain the integrity of the molecular structure. Immunofluorescence staining results revealed that the protein expressions of Egr-1 and VEGF in the model group were all significantly decreased, while those in the G-CSF group were remarkably elevated. RT-PCR and western blot analysis revealed that the mRNA and protein expressions of Egr-1 and VEGF in the model group were decreased obviously, but those in the G-CSF group were elevated significantly, and the differences between the two groups showed statistical significance (P<0.05). G-CSF manifests a significant protective effect on the acute ischemic cerebral injury, which may be realized through its effect on the expressions of Egr-1 and VEGF.

Thalidomide Reduces Hemorrhage of Brain Arteriovenous Malformations in a Mouse Model

BACKGROUND AND PURPOSE

Brain arteriovenous malformation (bAVM) is an important risk factor for intracranial hemorrhage. Current treatments for bAVM are all associated with considerable risks. There is no safe method to prevent bAVM hemorrhage. Thalidomide reduces nose bleeding in patients with hereditary hemorrhagic telangiectasia, an inherited disorder characterized by vascular malformations. In this study, we tested whether thalidomide and its less toxic analog, lenalidomide, reduce bAVM hemorrhage using a mouse model.

METHODS

bAVMs were induced through induction of brain focal activin-like kinase 1 (Alk1, an AVM causative gene) gene deletion and angiogenesis in adult Alk1-floxed mice. Thalidomide was injected intraperitoneally twice per week for 6 weeks, starting either 2 or 8 weeks after AVM induction. Lenalidomide was injected intraperitoneally daily starting 8 weeks after AVM induction for 6 weeks. Brain samples were collected at the end of the treatments for morphology, mRNA, and protein analyses. The influence of Alk1 downregulation on PDGFB (platelet-derived growth factor B) expression was also studied on cultured human brain microvascular endothelial cells. The effect of PDGFB in mural cell recruitment in bAVM was explored by injection of a PDGFB overexpressing lentiviral vector to the mouse brain.

RESULTS

Thalidomide or lenalidomide treatment reduced the number of dysplastic vessels and hemorrhage and increased mural cell (vascular smooth muscle cells and pericytes) coverage in the bAVM lesion. Thalidomide reduced the burden of CD68⁺ cells and the expression of inflammatory cytokines in the bAVM lesions. PDGFB expression was reduced in ALK1-knockdown human brain microvascular endothelial cells and in mouse bAVM lesion. Thalidomide increased Pdgfb expression in bAVM lesion. Overexpression of PDGFB mimicked the effect of thalidomide.

CONCLUSIONS

Thalidomide and lenalidomide improve mural cell coverage of bAVM vessels and reduce bAVM hemorrhage, which is likely through upregulation of Pdgfb expression.

An Engineered Optogenetic Switch for Spatiotemporal Control of Gene Expression, Cell Differentiation, and Tissue Morphogenesis

The precise spatial and temporal control of gene expression, cell differentiation, and tissue morphogenesis has widespread application in regenerative medicine and the study of tissue development. In this work, we applied optogenetics to control cell differentiation and new tissue formation. Specifically, we engineered an optogenetic "on" switch that provides permanent transgene expression following a transient dose of blue light illumination. To demonstrate its utility in controlling cell differentiation and reprogramming, we incorporated an engineered form of the master myogenic factor MyoD into this system in multipotent cells. Illumination of cells with blue light activated myogenic differentiation, including upregulation of myogenic markers and fusion into multinucleated myotubes. Cell differentiation was spatially patterned by illumination of cell cultures through a photomask. To demonstrate the application of the system to controlling in vivo tissue development, the light inducible switch was used to control the expression of VEGF and angiopoietin-1, which induced angiogenic sprouting in a mouse dorsal window chamber model. Live intravital microscopy showed illumination-dependent increases in blood-perfused microvasculature. This optogenetic switch is broadly useful for applications in which sustained and patterned gene expression is desired following transient induction, including tissue engineering, gene therapy, synthetic biology, and fundamental studies of morphogenesis.

Cardiac gene therapy with adeno-associated virus-based vectors

PURPOSE OF REVIEW

Cardiac gene therapy with adeno-associated virus (AAV)-based vectors is emerging as an entirely new platform to treat, or even cure, so far intractable cardiac disorders. This review describes our current knowledge of cardiac AAV gene therapy with a particular focus on the biggest obstacle for the successful translation of cardiac AAV gene therapy into the clinic, namely the efficient delivery of the therapeutic gene to the myocardium.

RECENT FINDINGS

We summarize the significant recent progress that has been made in treating heart failure in preclinically relevant animal models with AAV gene therapy and the recent results of clinical trials with cardiac AAV gene therapy for the treatment of heart failure. We also discuss the benefits and shortcomings of the currently available delivery methods of AAV to the heart. Finally, we describe the current state of identifying novel AAV variants that have enhanced tropism for human cardiomyocytes and that show increased resistance to preexisting neutralizing antibodies.

SUMMARY

Here, we describe the successes and challenges in cardiac AAV gene therapy, a treatment modality that has the potential to transform current treatment approaches for cardiac diseases.

Nonviral Vector-Based Gene Transfection of Primary Human Skeletal Myoblasts

Low-level transgene efficiency is one of the main obstacles in ex vivo nonviral vector–mediated gene transfer into primary human skeletal myoblasts (hSkMs). We optimized the cholesterol:N-[1-(2, 3-dioleoyloxy)propyl]-N, N, N-trimethylammonium methylsulfate liposome (CD liposome) and 22-kDa polyethylenimine (PEI22)– and 25-kDa polyethylenimine (PEI25)–mediated transfection of primary hSkMs for angiogenic gene delivery. We found that transfection efficiency and cell viability of three nonviral vectors were cell passage dependent: early cell passages of hSkMs had higher transfection efficiencies with poor cell viabilities, whereas later cell passages of hSkMs had lower transfection efficiencies with better cell viabilities. Trypsinization improved the transfection efficiency by 20% to 60% compared with adherent hSkMs. Optimum gene transfection efficiency was found with passage 6 trypsinized hSkMs: transfection efficiency with CD lipoplexes was 6.99 ± 0.13%, PEI22 polyplexes was 18.58 ± 1.57%, and PEI25 polyplexes was 13.32 ± 0.88%. When pEGFP (a plasmid encoding the enhanced green fluorescent protein) was replaced with a vector containing human vascular endothelial growth factor 165 (phVEGF165), the optimized gene transfection conditions resulted in hVEGF165 expression up to Day 18 with a peak level at Day 2 after transfection. This study demonstrated that therapeutic angiogenic gene transfer through CD or PEI is feasible and safe after optimization. It could be a potential strategy for treatment of

Integrin β8 Deletion Enhances Vascular Dysplasia and Hemorrhage in the Brain of Adult Alk1 Heterozygous Mice

Brain arteriovenous malformation (bAVM), characterized by tangled dysplastic vessels, is an important cause of intracranial hemorrhage in young adults, and its pathogenesis and progression are not fully understood. Patients with haploinsufficiency of transforming growth factor-β (TGF-β) receptors, activin receptor-like kinase 1 (ALK1) or endoglin (ENG) have a higher incidence of bAVM than the general population. However, bAVM does not develop effectively in mice with the same haploinsufficiency. The expression of integrin β8 subunit (ITGB8), another member in the TGF-β superfamily, is reduced in sporadic human bAVM. Brain angiogenic stimulation results at the capillary level of vascular malformation in adult Alk1 haploinsufficient (Alk1 ^+/- ) mice. We hypothesized that deletion of Itgb8 enhances bAVM development in adult Alk1 ^+/- mice. An adenoviral vector expressing Cre recombinase (Ad-Cre) was co-injected with an adeno-associated viral vector expressing vascular endothelial growth factor (AAV-VEGF) into the brain of Alk1 ^+/-;Itgb8-floxed mice to induce focal Itgb8 gene deletion and angiogenesis. We showed that compared with Alk ^+/- mice (4.75 ± 1.38/mm²), the Alk1 ^+/-;Itgb8-deficient mice had more dysplastic vessels in the angiogenic foci (7.14 ± 0.68/mm², P = 0.003). More severe hemorrhage was associated with dysplastic vessels in the brain of Itgb8-deleted Alk1 ^+/- , as evidenced by larger Prussian blue-positive areas (1278 ± 373 pixels/mm² vs. Alk1 ^+/-  : 320 ± 104 pixels/mm²; P = 0.028). These data indicate that both Itgb8 and Alk1 are important in maintaining normal cerebral angiogenesis in response to VEGF. Itgb8 deficiency enhances the formation of dysplastic vessels and hemorrhage in Alk1 ^+/- mice.

VEGF165Amicrosphere therapy for myocardial infarction suppresses acute cytokine release and increases microvascular density but does not improve cardiac function

Angiogenesis induced by growth factor-releasing microspheres can be an off-the-shelf and immediate alternative to stem cell therapy for acute myocardial infarction (AMI), independent of stem cell yield and comorbidity-induced dysfunction. Reliable and prolonged local delivery of intact proteins such as VEGF is, however, notoriously difficult. Our objective was to create a platform for local angiogenesis in human-sized hearts, using polyethylene-glycol/polybutylene-terephthalate (PEG-PBT) microsphere-based VEGF165Adelivery. PEG-PBT microspheres were biocompatible, distribution was size dependent, and a regimen of 10 × 10615-μm microspheres at 0.5 × 106/min did not induce cardiac necrosis. Efficacy, studied in a porcine model of AMI with reperfusion rather than chronic ischemia used for most reported VEGF studies, shows that microspheres were retained for at least 35 days. Acute VEGF165Arelease attenuated early cytokine release upon reperfusion and produced a dose-dependent increase in microvascular density at 5 wk following AMI. However, it did not improve major variables for global cardiac function, left ventricular dimensions, infarct size, or scar composition (collagen and myocyte content). Taken together, controlled VEGF165Adelivery is safe, attenuates early cytokine release, and leads to a dose-dependent increase in microvascular density in the infarct zone but does not translate into changes in global or regional cardiac function and scar composition.

Inhibition of pathological brain angiogenesis through systemic delivery of AAV vector expressing soluble FLT1

The soluble vascular endothelial growth factor (VEGF) receptor 1 (sFLT1) has been tested in both animals and humans for anti-angiogenic therapies, e.g., age-related macular degeneration. We hypothesized that adeno-associated viral vector (AAV)-mediated sFLT1 expression could be used to inhibit abnormal brain angiogenesis. We tested the anti-angiogenic effect of sFLT1 and the feasibility of using AAV serotype 9 to deliver sFLT1 through intravenous injection (IV) to the brain angiogenic region. AAV vectors were packaged in AAV serotypes 1 and 2 (stereotactic injection) and 9 (IV-injection). Brain angiogenesis was induced in adult mice through stereotactic injection of AAV1-VEGF. AAV2-sFLT02 containing sFLT1 VEGF-binding domain (domain 2) was injected into the brain angiogenic region, and AAV9-sFLT1 was injected into the jugular vein at the time of or 4 weeks after AAV1-VEGF injection. We showed that AAV2-sFLT02 inhibited brain angiogenesis at both time points. Intravenous injection of AAV9-sFLT1 inhibited angiogenesis only when the vector was injected 4 weeks after angiogenic induction. Neither lymphocyte infiltration nor neuron loss was observed in AAV9-sFLT1-treated mice. Our data show that systemically delivered AAV9-sFLT1 inhibits angiogenesis in the mouse brain, which could be utilized to treat brain angiogenic diseases such as brain arteriovenous malformation.

Immobilization of FLAG-Tagged Recombinant Adeno-Associated Virus 2 onto Tissue Engineering Scaffolds for the Improvement of Transgene Delivery in Cell Transplants

The technology of virus-based genetic modification in tissue engineering has provided the opportunity to produce more flexible and versatile biomaterials for transplantation. Localizing the transgene expression with increased efficiency is critical for tissue engineering as well as a challenge for virus-based gene delivery. In this study, we tagged the VP2 protein of type 2 adeno-associated virus (AAV) with a 3×FLAG plasmid at the N-terminus and packaged a FLAG-tagged recombinant AAV2 chimeric mutant. The mutant AAVs were immobilized onto the tissue engineering scaffolds with crosslinked anti-FLAG antibodies by N-succinimidyl-3-(2-pyridyldithiol) propionate (SPDP). Cultured cells were seeded to scaffolds to form 3D transplants, and then tested for viral transduction both in vitro and in vivo. The results showed that our FLAG-tagged AAV2 exerted similar transduction efficiency compared with the wild type AAV2 when infected cultured cells. Following immobilization onto the scaffolds of PLGA or gelatin sponge with anti-FLAG antibodies, the viral mediated transgene expression was significantly improved and more localized. Our data demonstrated that the mutation of AAV capsid targeted for antibody-based immobilization could be a practical approach for more efficient and precise transgene delivery. It was also suggested that the immobilization of AAV might have attractive potentials in applications of tissue engineering involving the targeted gene manipulation in 3D tissue cultures.

Novel brain arteriovenous malformation mouse models for type 1 hereditary hemorrhagic telangiectasia

Endoglin (ENG) is a causative gene of type 1 hereditary hemorrhagic telangiectasia (HHT1). HHT1 patients have a higher prevalence of brain arteriovenous malformation (AVM) than the general population and patients with other HHT subtypes. The pathogenesis of brain AVM in HHT1 patients is currently unknown and no specific medical therapy is available to treat patients. Proper animal models are crucial for identifying the underlying mechanisms for brain AVM development and for testing new therapies. However, creating HHT1 brain AVM models has been quite challenging because of difficulties related to deleting Eng-floxed sequence in Eng^2fl/2fl mice. To create an HHT1 brain AVM mouse model, we used several Cre transgenic mouse lines to delete Eng in different cell-types in Eng^2fl/2fl mice: R26CreER (all cell types after tamoxifen treatment), SM22α-Cre (smooth muscle and endothelial cell) and LysM-Cre (lysozyme M-positive macrophage). An adeno-associated viral vector expressing vascular endothelial growth factor (AAV-VEGF) was injected into the brain to induce focal angiogenesis. We found that SM22α-Cre-mediated Eng deletion in the embryo caused AVMs in the postnatal brain, spinal cord, and intestines. Induction of Eng deletion in adult mice using R26CreER plus local VEGF stimulation induced the brain AVM phenotype. In both models, Eng-null endothelial cells were detected in the brain AVM lesions, and formed mosaicism with wildtype endothelial cells. However, LysM-Cre-mediated Eng deletion in the embryo did not cause AVM in the postnatal brain even after VEGF stimulation. In this study, we report two novel HHT1 brain AVM models that mimic many phenotypes of human brain AVM and can thus be used for studying brain AVM pathogenesis and testing new therapies. Further, our data indicate that macrophage Eng deletion is insufficient and that endothelial Eng homozygous deletion is required for HHT1 brain AVM development.

Induction of brain arteriovenous malformation in the adult mouse

Brain arteriovenous malformations (bAVM) are tangles of abnormal, dilated vessels that directly shunt blood between the arteries and veins. The pathogenesis of bAVM is currently unknown. Patients with hereditary hemorrhagic telangiectasia (HHT) have a higher prevalence of bAVM than the general population. Animal models are important tools for dissecting the disease etiopathogenesis and for testing new therapies. Here, we introduce a method that induces the bAVM phenotype through regional deletion of activin-like kinase 1 (Alk1, the causal gene for HHT2) and vascular endothelial growth factor (VEGF) stimulation.

MSCs transplantation with application of G-CSF reduces apoptosis or increases VEGF in rabbit model of myocardial infarction

The purpose of this study was to test whether mesenchymal stem cells (MSCs) transplantation with application of granulocyte colony-stimulating factor (G-CSF) would have beneficial effects on damaged heart in a rabbit model of myocardial infarction (MI). MI was created by ligation of the left anterior descending coronary artery. After induction of MI, 40 New Zealand white rabbits were randomly divided into 8 groups: (1) MSCs injection at 3 days after MI; (2) G-CSF injection at 3 days after MI; (3) MSCs + G-CSF (20 u/kg/day) injection at 3 days after MI; (4) PBS injection at 3 days after MI; (5) MSCs injection at 7 days after MI; (6) G-CSF injection at 7 days after MI; (7) MSCs + G-CSF (20 u/kg/day) injection 7 days after MI; and (8) PBS injection 7 days after MI. TUNEL analysis showed that the apoptotic cells were distributed in the marginal area of MI. In both 3 and 7 days after MI groups, there were less apoptotic cells in the MSCs and MSCs + G-CSF groups as compared with the PBS group (P < 0.05). However, no decrease in apoptosis was observed in the G-CSF only group (P > 0.05). Immunohistochemistry analysis demonstrated that the expression level of vascular endothelial growth factor was higher in the MSCs, MSCs + G-CSF and G-CSF groups as compared with the PBS group. The present study demonstrated a beneficial effect of MSCs transplantation with application of G-CSF in the treatment of rabbit MI.

An emerging adeno-associated viral vector pipeline for cardiac gene therapy

The naturally occurring adeno-associated virus (AAV) isolates display diverse tissue tropisms in different hosts. Robust cardiac transduction in particular has been reported for certain AAV strains. Successful applications of these AAV strains in preclinical and clinical settings with a focus on treating cardiovascular disease continue to be reported. At the same time, these studies have highlighted challenges such as cross-species variability in AAV tropism, transduction efficiency, and immunity. Continued progress in our understanding of AAV capsid structure and biology has provided the rationale for designing improved vectors that can possibly address these concerns. The current report provides an overview of cardiotropic AAV, existing gaps in our knowledge, and newly engineered AAV strains that are viable candidates for the cardiac gene therapy clinic.

Vascular-targeted therapies for Duchenne muscular dystrophy

Duchenne muscular dystrophy (DMD) is the most common muscular dystrophy and an X-linked recessive, progressive muscle wasting disease caused by the absence of a functional dystrophin protein. Dystrophin has a structural role as a cytoskeletal stabilization protein and protects cells against contraction-induced damage. Dystrophin also serves a signaling role through mechanotransduction of forces and localization of neuronal nitric oxide synthase (nNOS), which produces nitric oxide (NO) to facilitate vasorelaxation. In DMD, the signaling defects produce inadequate tissue perfusion caused by functional ischemia due to a diminished ability to respond to shear stress induced endothelium-dependent dilation. Additionally, the structural defects seen in DMD render myocytes with an increased susceptibility to mechanical stress. The combination of both defects is necessary to generate myocyte damage, which induces successive rounds of myofiber degeneration and regeneration, loss of calcium homeostasis, chronic inflammatory response, fibrosis, and myonecrosis. In individuals with DMD, these processes inevitably cause loss of ambulation shortly after the first decade and an abbreviated life with death in the third or fourth decade due to cardio-respiratory anomalies. There is no known cure for DMD, and although the culpable gene has been identified for more than twenty years, research on treatments has produced few clinically relevant results. Several recent studies on novel DMD therapeutics are vascular targeted and focused on attenuating the inherent functional ischemia. One approach improves vasorelaxation capacity through pharmaceutical inhibition of either phosphodiesterase 5 (PDE5) or angiotensin-converting enzyme (ACE). Another approach increases the density of the underlying vascular network by inducing angiogenesis, and this has been accomplished through either direct delivery of vascular endothelial growth factor (VEGF) or by downregulating the VEGF decoy-receptor type 1 (VEGFR-1 or Flt-1). The pro-angiogenic approaches also seem to be pro-myogenic and could resolve the age-related decline in satellite cell (SC) quantity seen in mdx models through expansion of the SC juxtavascular niche. Here we review these four vascular targeted treatment strategies for DMD and discuss mechanisms, proof of concept, and the potential for clinical relevance associated with each therapy.

Transplantation of novel vascular endothelial growth factor gene delivery system manipulated skeletal myoblasts promote myocardial repair

BACKGROUND

Skeletal myoblast (SkM) transplantation combined with vascular endothelial growth factor (VEGF) gene delivery has been proposed as a promising therapy for cardiac repair. Nevertheless, the defective gene vectors and unregulable VEGF expression in vivo hinder its application. Therefore, the search for an economical, effective, controllable gene delivery system is quite necessary.

METHODS

In our study, hyperbranched polyamidoamine (h-PAMAM) dendrimer was synthesized as a novel gene delivery vector using a modified method. And hypoxia-regulated human VEGF-165 plasmids (pHRE-hVEGF165) were constructed for controllable VEGF gene expression. The efficiency and feasibility of h-PAMAM-HRE-hVEGF165 gene delivery system manipulated SkM transplantation for cardiac repair were investigated in myocardial infarction models.

RESULTS

The h-PAMAM encapsulated pHRE-hVEGF165 could resist nuclease digestion for over 120 min. In primary SkMs, h-PAMAM-pHRE-hVEGF165 gene delivery system showed high transfection efficiency (43.47 ± 2.22%) and minor cytotoxicity (cell viability = 91.38 ± 0.48%). And the transfected SkMs could express hVEGF165 for 18 days under hypoxia in vitro. For myocardial infarction models, intramyocardial transplantation of the transfected SkMs could result in reduction of apoptotic myocardiocytes, improvement of grafted cell survival, decrease of infarct size and interstitial fibrosis, and increase of blood vessel density, which inhibited left ventricle remodeling and improved heart function at the late phase following infarction.

CONCLUSIONS

These results indicate that h-PAMAM based pHRE-hVEGF165 gene delivery into SkMs is feasible and effective, and may serve as a novel and promising gene therapy strategy in ischemic heart disease.

Minimal homozygous endothelial deletion of Eng with VEGF stimulation is sufficient to cause cerebrovascular dysplasia in the adult mouse

BACKGROUND

Brain arteriovenous malformations (bAVMs) represent a high risk for hemorrhagic stroke, leading to significant neurological morbidity and mortality in young adults. The etiopathogenesis of bAVM remains unclear. Research progress has been hampered by the lack of animal models. Hereditary Hemorrhagic Telangiectasia (HHT) patients with haploinsufficiency of endoglin (ENG, HHT1) or activin receptor-like kinase 1 (ALK1, HHT2) have a higher incidence of bAVM than the general population. We previously induced cerebrovascular dysplasia in the adult mouse that resembles human bAVM through Alk1 deletion plus vascular endothelial growth factor (VEGF) stimulation. We hypothesized that Eng deletion plus VEGF stimulation would induce a similar degree of cerebrovascular dysplasia as the Alk1-deleted brain.

METHODS

Ad-Cre (an adenoviral vector expressing Cre recombinase) and AAV-VEGF (an adeno-associated viral vector expressing VEGF) were co-injected into the basal ganglia of 8- to 10-week-old Eng(2f/2f) (exons 5 and 6 flanked by loxP sequences), Alk1(2f/2f) (exons 4-6 flanked by loxP sequences) and wild-type (WT) mice. Vascular density, dysplasia index, and gene deletion efficiency were analyzed 8 weeks later.

RESULTS

AAV-VEGF induced a similar degree of angiogenesis in the brain with or without Alk1- or Eng-deletion. Abnormally patterned and dilated dysplastic vessels were found in the viral vector-injected region of Alk1(2f/2f) and Eng(2f/2f) brain sections, but not in WT. Alk1(2f/2f) mice had about 1.8-fold higher dysplasia index than Eng(2f/2f) mice (4.6 ± 1.9 vs. 2.5 ± 1.1, p < 0.05). However, after normalization of the dysplasia index with the gene deletion efficiency (Alk1(2f/2f): 16% and Eng(2f/2f): 1%), we found that about 8-fold higher dysplasia was induced per copy of Eng deletion (2.5) than that of Alk1 deletion (0.3). ENG-negative endothelial cells were detected in the Ad-Cre-treated brain of Eng(2f/2f) mice, suggesting homozygous deletion of Eng in the cells. VEGF induced more severe vascular dysplasia in the Ad-Cre-treated brain of Eng(2f/2f) mice than that of Eng(+/-) mice.

CONCLUSIONS

(1) Deletion of Eng induces more severe cerebrovascular dysplasia per copy than that of Alk1 upon VEGF stimulation. (2) Homozygous deletion of Eng with angiogenic stimulation may be a promising strategy for development of a bAVM mouse model. (3) The endothelial cells that have homozygous causal gene deletion in AVM could be crucial for lesion development.

Bevacizumab attenuates VEGF-induced angiogenesis and vascular malformations in the adult mouse brain

BACKGROUND AND PURPOSE

Vascular endothelial growth factor (VEGF) expression is elevated in human brain arteriovenous malformations (bAVM). We have developed a bAVM model in the adult mouse by focal Alk1 gene deletion and human VEGF stimulation. We hypothesized that once the abnormal vasculature has been established, tonic VEGF stimulation is necessary to maintain the abnormal phenotype, and VEGF antagonism by bevacizumab (Avastin) would reduce vessel density and attenuate the dysplastic vascular phenotype.

METHODS

Angiogenesis and bAVM were induced by injection of adeno-associated viral vector expressing human VEGF alone into the brain of wild-type mice or with adenoviral vector expressing Cre recombinase (Ad-Cre) into Alk1(2f/2f) mice. Six weeks later, bevacizumab or trastuzumab (Herceptin, bevacizumab control) was administered. Vessel density, dysplasia index, vascular cell proliferation and apoptosis, and human IgG were assessed (n=6/group).

RESULTS

Compared with trastuzumab (15 mg/kg), administration of 5, 10, and 15 mg/kg of bevacizumab to adeno-associated viral vector expressing human VEGF treated wild-type mice reduced focal vessel density (P<0.05); administration of 5 mg/kg bevacizumab decreased proliferating vascular cells (P=0.04) and increased TUNEL-positive vascular cells (P=0.03). More importantly, bevacizumab (5 mg/kg) treatment reduced both vessel density (P=0.01) and dysplasia index (P=0.02) in our bAVM model. Human IgG was detected in the vessel wall and in the parenchyma in the angiogenic foci of bevacizumab-treated mice.

CONCLUSIONS

We provide proof-of-principle that, once abnormal AVM vessels have formed, VEGF antagonism may reduce the number of dysplastic vessels and should be evaluated further as a therapeutic strategy for the human disease.

Coexpression of angiopoietin-1 with VEGF increases the structural integrity of the blood-brain barrier and reduces atrophy volume

Vascular endothelial growth factor (VEGF)-induced neovasculature is immature and leaky. We tested if coexpression of angiopoietin-1 (ANG1) with VEGF improves blood-brain barrier (BBB) integrity and VEGF neuroprotective and neurorestorative effects using a permanent distal middle cerebral artery occlusion (pMCAO) model. Adult CD-1 mice were injected with 2 × 10(9) virus genomes of adeno-associated viral vectors expressing VEGF (AAV-VEGF) or ANG1 (AAV-ANG1) individually or together in a 1:1 ratio into the ischemic penumbra 1 hour after pMCAO. AAV-LacZ was used as vector control. Samples were collected 3 weeks later. Compared with AAV-LacZ, coinjection of AAV-VEGF and AAV-ANG1 reduced atrophy volume (46%, P=0.004); injection of AAV-VEGF or AAV-ANG1 individually reduced atrophy volume slightly (36%, P=0.08 and 33%, P=0.09, respectively). Overexpression of VEGF reduced tight junction protein expression and increased Evans blue extravasation. Compared with VEGF expression alone, coexpression of ANG1 with VEGF resulted in upregulation of tight junction protein expression and reduction of Evans blue leakage (AAV-ANG1/AAV-VEGF: 1.4 ± 0.3 versus AAV-VEGF: 2.8 ± 0.7, P=0.001). Coinjection of AAV-VEGF and AAV-ANG1 induced a similar degree of angiogenesis as injection of AAV-VEGF alone (P=0.85). Thus, coexpression of ANG1 with VEGF improved BBB integrity and resulted in better neuroprotection compared with VEGF expression alone.

AAV vectors for cardiac gene transfer: experimental tools and clinical opportunities

Since the first demonstration of in vivo gene transfer into myocardium there have been a series of advancements that have driven the evolution of cardiac gene delivery from an experimental tool into a therapy currently at the threshold of becoming a viable clinical option. Innovative methods have been established to address practical challenges related to tissue-type specificity, choice of delivery vehicle, potency of the delivered material, and delivery route. Most importantly for therapeutic purposes, these strategies are being thoroughly tested to ensure safety of the delivery system and the delivered genetic material. This review focuses on the development of recombinant adeno-associated virus (rAAV) as one of the most valuable cardiac gene transfer agents available today. Various forms of rAAV have been used to deliver "pre-event" cardiac protection and to temper the severity of hypertrophy, cardiac ischemia, or infarct size. Adeno-associated virus (AAV) vectors have also been functional delivery tools for cardiac gene expression knockdown studies and successfully improving the cardiac aspects of several metabolic and neuromuscular diseases. Viral capsid manipulations along with the development of tissue-specific and regulated promoters have greatly increased the utility of rAAV-mediated gene transfer. Important clinical studies are currently underway to evaluate AAV-based cardiac gene delivery in humans.

Overexpression of vascular endothelial growth factor 165 (VEGF165) protects cardiomyocytes against doxorubicin-induced apoptosis

Doxorubicin (Dox) has been employed in cancer chemotherapy for a few decades. However its clinical application became restricted because of dose-dependent cardiomyopathy. Recent studies suggest that Dox-induced cardiomyocyte apoptosis is a primary cause of cardiac damage. Vascular endothelial growth factor (VEGF) is a major factor for endothelial cell survival and angiogenesis. We have previously shown that VEGF165 significantly attenuates oxidative stress-induced cardiomyocytes apoptosis. We hypothesized that VEGF165 will protect the cardiomyocytes from Dox-induced apoptosis. to evaluate our hypothesis, we transfected cardiomyocytes H9c2 with adenovirus expressing VEGF165 24 hours before the cells were challenged with Dox at a concentration of 2 µm. Cardiomyocyte apoptosis was evaluated by Annexin V-FITC staining and by Western blot detection of cleaved caspase-3. The hypothesis was confirmed, and the protective mechanisms involve the inhibition of death receptor-mediated apoptosis and up-regulation of the prosurvival Akt/Nf-κb/bcl-2 signaling pathway.

Arteriovenous malformation in the adult mouse brain resembling the human disease

OBJECTIVE

Brain arteriovenous malformations (bAVMs) are an important cause of hemorrhagic stroke. The underlying mechanisms are not clear. No animal model for adult bAVM is available for mechanistic exploration. Patients with hereditary hemorrhagic telangiectasia type 2 (HHT2) with activin receptor-like kinase 1 (ALK1; ACVRL1) mutations have a higher incidence of bAVM than the general population. We tested the hypothesis that vascular endothelial growth factor (VEGF) stimulation with regional homozygous deletion of Alk1 induces severe dysplasia in the adult mouse brain, akin to human bAVM.

METHODS

Alk1(2f/2f) (exons 4-6 flanked by loxP sites) and wild-type (WT) mice (8-10 weeks old) were injected with adenoviral vector expressing Cre recombinase (Ad-Cre; 2 × 10(7) plaque forming units [PFU]) and adeno-associated viral vectors expressing VEGF (AAV-VEGF; 2 × 10(9) genome copies) into the basal ganglia. At 8 weeks, blood vessels were analyzed.

RESULTS

Gross vascular irregularities were seen in Alk1(2f/2f) mouse brain injected with Ad-Cre and AAV-VEGF. The vessels were markedly enlarged with abnormal patterning resembling aspects of the human bAVM phenotype, displayed altered expression of the arterial and venous markers (EphB4 and Jagged-1), and showed evidence of arteriovenous shunting. Vascular irregularities were not seen in similarly treated WT mice.

INTERPRETATION

Our data indicate that postnatal, adult formation of the human disease, bAVM, is possible, and that both genetic mutation and angiogenic stimulation are necessary for lesion development. Our work not only provides a testable adult mouse bAVM model for the first time, but also suggests that specific medical therapy can be developed to slow bAVM growth and potentially stabilize the rupture-prone abnormal vasculature.

Adeno-associated viral vector mediated and cardiac-specific delivery of CD151 gene in ischemic rat hearts

Our previous studies demonstrated that CD151 gene promoted neovascularization in ischemic heart model. To improve the delivery efficacy and target specificity of CD151 gene to ischemic heart, we generated an adeno-associated virus (AAV) vector in which CD151 expression was controlled by the myosin light chain (MLC-2v) promoter to achieve the cardiac-specific expression of CD151 gene in ischemic myocardium and to limit unwanted CD151 expression in extracardiac organs. The function of this vector was examined in rat ischemic myocardium model. The protein expression of CD151 in the ischemic myocardium areas, liver and kidney was confirmed by using Western blot, while the microvessels within ischemic myocardium areas were detected by using immunohistochemistry. The results showed that MLC-2v significantly enhanced the expression of CD151 in ischemic myocardium, but attenuated its expression in other organs. The forced CD151 expression could increase the number of microvessels in the ischemic myocardium. This study demonstrates the AAV-mediated and MLC-2v regulated CD151 gene is highly expressed in the ischemic myocardium and cardiac-specific delivery that is more efficiently targets CD151 to the ischemia myocardium after myocardial infarction.

Adeno associated viral vector-delivered and hypoxia response element-regulated CD151 expression in ischemic rat heart

AIM

The aim of this study was to improve the delivery efficacy and target specificity of the pro-angiogenic gene CD151 to the ischemic heart.

METHODS

To achieve the inducible expression of adeno-associated viral (AAV)-delivered CD151 gene in only the ischemic myocardium, we generated an AAV construct in which CD151 expression can be controlled by the hypoxia response element (HRE) sequence from the human Enolase gene. The function of this vector was examined in rat H9C2 cardiac myoblasts and in ischemic rat myocardium. The expression of CD151 in the areas of ischemic myocardium was confirmed at the mRNA level by real-time PCR and on the protein level by Western blot, whereas the CD151 expression in the microvessels within the areas of ischemic myocardium was detected by immunohistochemistry.

RESULTS

HRE significantly enhances the expression of CD151 under hypoxic conditions or in the ischemic myocardium, and forced CD151 expression increases the number of microvessels in the ischemic myocardium.

CONCLUSION

The AAV-mediated, HRE regulated delivery of the CD151 gene shows higher expression in the ischemic myocardium and more efficiently targets CD151 to the hypoxic regions after myocardial infarction.

Coexpression of VEGF and angiopoietin-1 promotes angiogenesis and cardiomyocyte proliferation reduces apoptosis in porcine myocardial infarction (MI) heart

VEGF and angiopoietin-1 (Ang1) are two major angiogenic factors being investigated for the treatment of myocardial infarction (MI). Targeting VEGF and Ang1 expression in the ischemic myocardium can increase their local therapeutic effects and reduce possible adverse effects. Adeno-associated viral vectors (AAVs) expressing cardiac-specific and hypoxia-inducible VEGF [AAV-myosin light chain-2v (MLC)VEGF] and Ang1 (AAV-MLCAng1) were coinjected (VEGF/Ang1 group) into six different sites of the porcine myocardium at the peri-infarct zone immediately after ligating the left descending coronary artery. An identical dose of AAV-Cytomegalovirus (CMV)LacZ or saline was injected into control animals. AAV genomes were detected in the liver in addition to the heart. RT-PCR, Western blotting, and ELISA analyses showed that VEGF and Ang1 were predominantly expressed in the myocardium in the infarct core and border of the infarct heart. Gated single-photon emission computed tomography analyses showed that the VEGF/Ang1 group had better cardiac function and myocardial perfusion at 8 wk than at 2 wk after vector injection. Compared with the saline and LacZ controls, the VEGF/Ang1 group expressed higher phosphorylated Akt and Bcl-xL, less Caspase-3 and Bad, and had higher vascular density, more proliferating cardiomyocytes, and less apoptotic cells in the infarct and peri-infarct zones. Thus, cardiac-specific and hypoxia-induced coexpression of VEGF and Ang1 improves the perfusion and function of porcine MI heart through the induction of angiogenesis and cardiomyocyte proliferation, activation of prosurvival pathways, and reduction of cell apoptosis.

Adeno-associated virus vector delivery to the heart

Cardiac gene transfer may serve as a novel therapeutic approach in the treatment of heart disease. For it to reach its full potential, methods for highly efficient cardiac gene transfer must be available to investigators so that informative preclinical data can be collected and evaluated. We have recently optimized AAV-mediated cardiac gene transfer protocols in both the mouse and rat. In the mouse, we have developed a procedure for intrapericardial delivery of vector in the neonate and successfully applied intravenous injections in adult animals. In the rat, we have developed a procedure for direct injection of vector into the myocardium in adults and established a protocol for vector delivery into the left ventricular anterior wall by ultrasound-targeted destruction of microbubbles loaded with AAV. Each protocol can be used to achieve safe and efficient cardiac gene transfer in the model of choice.

Robust cardiomyocyte-specific gene expression following systemic injection of AAV: in vivo gene delivery follows a Poisson distribution

Newly-isolated serotypes of AAV readily cross the endothelial barrier to provide efficient transgene delivery throughout the body. However, tissue-specific expression is preferred in most experimental studies and gene therapy protocols. Previous efforts to restrict gene expression to the myocardium often relied on direct injection into heart muscle or intracoronary perfusion. Here, we report an AAV vector system employing the cardiac troponin T promoter (cTnT). Using luciferase and eGFP, the efficiency and specificity of cardiac reporter gene expression using AAV serotype capsids: AAV-1, 2, 6, 8 or 9 were tested after systemic administration to 1 week old mice. Luciferase assays showed that the cTnT promoter worked in combination with each of the AAV serotype capsids to provide cardiomyocyte-specific gene expression, but AAV-9 followed closely by AAV-8 was the most efficient. AAV9-mediated gene expression from the cTnT promoter was 640-fold greater in the heart compared to the next highest tissue (liver). eGFP fluorescence indicated a transduction efficiency of 96% using AAV-9 at a dose of only 3.15×10¹⁰ viral particles per mouse. Moreover, the intensity of cardiomyocyte eGFP fluorescence measured on a cell-by-cell basis revealed that AAV-mediated gene expression in the heart can be modeled as a Poisson distribution; requiring an average of nearly two vector genomes per cell to attain an 85% transduction efficiency.

Reduced expression of integrin alphavbeta8 is associated with brain arteriovenous malformation pathogenesis

Brain arteriovenous malformations (BAVMs) are a rare but potentially devastating hemorrhagic disease. Transforming growth factor-beta signaling is required for proper vessel development, and defective transforming growth factor-beta superfamily signaling has been implicated in BAVM pathogenesis. We hypothesized that expression of the transforming growth factor-beta activating integrin, alphavbeta8, is reduced in BAVMs and that decreased beta8 expression leads to defective neoangiogenesis. We determined that beta8 protein expression in perivascular astrocytes was reduced in human BAVM lesional tissue compared with controls and that the angiogenic response to focal vascular endothelial growth factor stimulation in adult mouse brains with local Cre-mediated deletion of itgb8 and smad4 led to vascular dysplasia in newly formed blood vessels. In addition, common genetic variants in ITGB8 were associated with BAVM susceptibility, and ITGB8 genotypes associated with increased risk of BAVMs correlated with decreased beta8 immunostaining in BAVM tissue. These three lines of evidence from human studies and a mouse model suggest that reduced expression of integrin beta8 may be involved in the pathogenesis of sporadic BAVMs.

Angiogenesis induced by hVEGF165 gene controlled by hypoxic response elements in rabbit ischemia myocardium

Hypoxic response element (HRE) offers satisfactory control over expression of hVEGF(165) in cell levels. However, the characteristics of regenerated blood vessels induced by long-term expression of transferred hVEGF(165) under control of HRE in vivo remain unknown. This study aims to investigate the effect of HRE on control of long-term expression of rAAV-delivered hVEGF(165) gene to ischemic myocardium and evaluate characteristics of angiogenesis induced by hVEGF(165) in vivo. Rabbit ischemic heart models were established surgically, rAAV-9HRE-hVEGF(165) was transfected to ischemia hearts subjected to 12 week ischemia. Molecular biological and immunohistochemistry were employed to determine expressions of HIF-1alpha and hVEGF(165). Microvessel densities of CD31(+) and alpha-SMA(+) regenerated vessels were also evaluated. Expressions of both hVEGF(165) mRNA and protein were upregulated following over-expression of endogenous HIF-1alpha early after ischemia, peaked at 4-6 weeks post-MI, declined, and approached pre-ischemia level at the end of 12 weeks of ischemia (P < 0.01). The significantly upregulated CD31 in hVEGF(165)-treated hearts presented from 8 to 12 weeks of ischemia compared with the control (P < 0.01). However, alpha-SMA expression was rapidly downregulated after ischemia and remained lower than the control level by the end of 12 weeks post-MI (P < 0.01). Overexpression of hVEGF(165) controlled by HIF-1alpha-HRE system shows a stably regional angiogenic efficacy in vivo. But, VEGF, as an early angiogenic cytokine, is inadequate for mediating histologically mature vessels in ischemia myocardium.

Combining angiogenic gene and stem cell therapies for myocardial infarction

BACKGROUND

Transplantation of stem cells from various sources into infarcted hearts has the potential to promote myocardial regeneration. However, the regenerative capacity is limited partly as a result of the low survival rate of the transplanted cells in the ischemic myocardium. In the present study, we tested the hypothesis that combining cell and angiogenic gene therapies would provide additive therapeutic effects via co-injection of bone marrow-derived mesenchymal stem cells (MSCs) with an adeno-associated viral vector (AAV), MLCVEGF, which expresses vascular endothelial growth factor (VEGF) in a cardiac-specific and hypoxia-inducible manner.

METHODS

MSCs isolated from transgenic mice expressing green fluorescent protein and MLCVEGF packaged in AAV serotype 1 capsid were injected into mouse hearts at the border of ischemic area, immediately after occlusion of the left anterior descending coronary, individually or together. Engrafted cells were detected and quantified by real-time polymerase chain reaction and immunostaining. Angiogenesis and infarct size were analyzed on histological and immunohistochemical stained sections. Cardiac function was analyzed by echocardiography.

RESULTS

We found that co-injection of AAV1-MLCVEGF with MSCs reduced cell loss. Although injection of MSCs and AAV1-MLCVEGF individually improved cardiac function and reduced infarct size, co-injection of MSC and AAV1-MLCVEGF resulted in the best improvement in cardiac function as well as the smallest infarct among all groups. Moreover, injection of AAV1-MLCVEGF induced neovasculatures. Nonetheless, injection of MSCs attracted endogenous stem cell homing and increased scar thickness.

CONCLUSIONS

Co-injection of MLCVEGF and MSCs in ischemic hearts can result in better cardiac function and MSC survival, compared to their individual injections, as a result of the additive effects of each therapy.

Analysis of angiogenesis induced by local IGF-1 expression after myocardial infarction using microSPECT-CT imaging

Insulin-like growth factor-1 (IGF-1) has been found to exert favorable effects on angiogenesis in prior animal studies. This study explored the long-term effect of IGF-1 on angiogenesis using microSPECT-CT in infarcted rat hearts after delivering human IGF-1 gene by adeno-associated virus (AAV). Myocardial infarction (MI) was induced in Sprague-Dawley rats by ligation of the proximal anterior coronary artery and a total of 10(11) AAV-CMV-lacZ (control) or IGF-1 vectors were injected around the peri-infarct area. IGF-1 expression by AAV stably transduced heart muscle for up to 16 weeks post-MI and immunohistochemistry revealed a remarkable increase in capillary density. A (99m)Tc-labeled RGD peptide (NC100692, GE Healthcare) was used to assess temporal and regional alpha(v) integrin activation. Rats were injected with NC100692 followed by (201)Tl chloride and in vivo microSPECT-CT imaging was performed. After imaging, hearts were excised and cut for quantitative gamma-well counting (GWC). NC100692 retention was significantly increased in hypoperfused regions of both lacZ and IGF-1 rats at 4 and 16 weeks post-MI. Significantly higher activation of alpha(v) integrin was observed in IGF-1 rats at 4 weeks after treatment compared with control group, although the activation was lower in the IGF-1 group at 16 weeks. Local IGF-1 gene delivery by AAV can render a sustained transduction and improve cardiac function post-MI. IGF-1 expression contributes to enhanced alpha(v) integrin activation which is linked to angiogenesis. MicroSPECT-CT imaging with (99m)Tc-NC100692 and quantitative GWC successfully assessed differences in alpha(v) integrin activation between IGF-1-treated and control animals post-MI.

Attenuation of brain response to vascular endothelial growth factor-mediated angiogenesis and neurogenesis in aged mice

BACKGROUND AND PURPOSE

Alterations of neuroangiogenic response play important roles in the development of aging-related neurodisorders and affect gene-based therapies. We tested brain response to vascular endothelial growth factor (VEGF) in aged mice.

METHODS

Adeno-associated viral vector (AAV)-VEGF, an adeno-associated viral vector expressing VEGF, was injected into the brain of 3-, 12-, and 24-month-old mice. AAV-LacZ-injected mice were used as controls (n=6). Before euthanasia at 6 weeks after vector injection, the mice were intraperitoneally injected with 5-bromodeoxyuridine for 3 consecutive days. The vascular density and the number of neuroprogenitors were analyzed.

RESULTS

Injection of AAV-VEGF increased the vascular density in the brain of 3-, 12-, and 24-month-old mice by 22%+/-7% (AAV-VEGF: 320+/-15 per 10x field versus AAV-LacZ: 263+/-8, P<0.05), 20%+/-8 (AAV-VEGF: 300+/-9 versus AAV-LacZ: 250+/-11, P<0.05), and 7%+/-16% (AAV-VEGF: 257+/-27 versus AAV-LacZ: 236+/-13, P=0.283), respectively. There were more VEGF receptor-positive neuroprogenitors in the subventricular zone of AAV-VEGF-injected 3- (22+/-2) and 12-month-old mice (21+/-5) than that of 24-month-old mice (7+/-1). More 5-bromodeoxyuridine-positive endothelial cells and neuroprogenitors were detected around the injection site and subventricular zone of 3- (13+/-4) and 12-month-old mice (14+/-5) than that of 24-month-old mice (1+/-1). VEGF receptor 2 was upregulated in AAV-VEGF-injected brains of 3- and 12-month-old mice, but not in 24-month-old mice.

CONCLUSIONS

The angiogenic and neurogenic response to VEGF stimulation is attenuated in the aged mouse brain, which may be due to reduced VEGF receptor activity.

Chronic hypoxia attenuates VEGF signaling and angiogenic responses by downregulation of KDR in human endothelial cells

Coronary artery disease results in progressive vascular stenosis associated with chronic myocardial ischemia. Vascular endothelial growth factor (VEGF) stimulates endothelial cell angiogenic responses to revascularize ischemic tissues; however, the effect of chronic hypoxia on the responsiveness of endothelial cells to VEGF remains unclear. We, therefore, investigated whether hypoxia alters VEGF-stimulated signaling and angiogenic responses in primary human coronary artery endothelial (HCAE) cells. Exposure of HCAE cells to hypoxia (1% O(2)) for 24 h decreased VEGF-stimulated endothelial cell migration ( approximately 82%), proliferation ( approximately 30%), and tube formation. Hypoxia attenuated VEGF-stimulated activation of endothelial nitric oxide (NO) synthase (eNOS) ( approximately 72%) and reduced NO production in VEGF-stimulated cells from 237 +/- 38.8 to 61.3 +/- 28.4 nmol/l. Moreover, hypoxia also decreased the ratio of phosphorylated eNOS to total eNOS in VEGF-stimulated cells by approximately 50%. This effect was not observed in thrombin-stimulated cells, suggesting that hypoxia specifically inhibited VEGF signaling upstream of eNOS phosphorylation. VEGF-induced activation of Akt, ERK1/2, p38, p70S6 kinases, and S6 ribosomal protein was also attenuated in hypoxic cells. Moreover, VEGF-stimulated phosphorylation of VEGF receptor-2 (KDR) at Y996 and Y1175 was decreased by hypoxia. This decrease correlated with a 70 +/- 12% decrease in KDR protein expression. Analysis of mRNA from these cells showed that hypoxia reduced steady-state levels of KDR mRNA by 52 +/- 16% and decreased mRNA stability relative to normoxic cells. Our findings demonstrate that chronic hypoxia attenuates VEGF-stimulated signaling in HCAE cells by specific downregulation of KDR expression. These data provide a novel explanation for the impaired angiogenic responses to VEGF in endothelial cells exposed to chronic hypoxia.

Expression of cardiac function genes in adult stem cells is increased by treatment with nitric oxide agents

Mesenchymal stem cells (MSCs) have received special attention for cardiomyoplasty because several studies have shown that they differentiate into cardiomyocytes both in vitro and in vivo. Nitric oxide (NO) is a free radical signaling molecule that regulates several differentiation processes including cardiomyogenesis. Here, we report an investigation of the effects of two NO agents (SNAP and DEA/NO), able to activate both cGMP-dependent and -independent pathways, on the cardiomyogenic potential of bone marrow-derived mesenchymal stem cells (BM-MSCs) and adipose tissue-derived stem cells (ADSCs). The cells were isolated, cultured and treated with NO agents. Cardiac- and muscle-specific gene expression was analyzed by indirect immunofluorescence, flow cytometry, RT-PCR and real-time PCR. We found that untreated (control) ADSCs and BM-MSCs expressed some muscle markers and NO-derived intermediates induce an increased expression of some cardiac function genes in BM-MSCs and ADSCs. Moreover, NO agents considerably increased the pro-angiogenic potential mostly of BM-MSCs as determined by VEGF mRNA levels.

Contribution of bone marrow-derived cells associated with brain angiogenesis is primarily through leukocytes and macrophages

OBJECTIVE

We investigated the role of bone marrow-derived cells (BMDCs) in an angiogenic focus, induced by VEGF stimulation.

METHODS AND RESULTS

BM from GFP donor mice was isolated and transplanted into lethally irradiated recipients. Four weeks after transplantation, groups of mice received adeno-associated viral vector (AAV)-VEGF or AAV-lacZ gene (control) injection and were euthanized at 1 to 24 weeks. BMDCs were characterized by double-labeled immunostaining. The function of BMDCs was further examined through matrix metalloproteinase (MMP)-2 and -9 activity. We found that capillary density increased after 2 weeks, peaked at 4 weeks (P<0.01), and sustained up to 24 weeks after gene transfer. GFP-positive BMDCs infiltration in the angiogenic focus began at 1 week, peaked at 2 weeks, and decreased thereafter. The GFP-positive BMDCs were colocalized with CD45 (94%), CD68 (71%), 5% Vimentin (5%), CD31/von Willebrand factor (vWF) (1%), and alpha-smooth muscle actin (alpha -SMA, 0.5%). Infiltrated BMDCs expressed MMP-9. MMP-9 KO mice confirmed the dependence of the angiogenic response on MMP-9 availability.

CONCLUSIONS

Nearly all BMDCs in the angiogenic focus showed expression for leukocytes/macrophages, indicating that BMDCs minimally incorporated into the neovasculature. Colocalization of MMPs with GFP suggests that BMDCs play a critical role in VEGF-induced angiogenic response through up-regulation of MMPs.

Permanent coronary artery occlusion: cardiovascular MR imaging is platform for percutaneous transendocardial delivery and assessment of gene therapy in canine model

PURPOSE

To provide evidence that vascular endothelial growth factor (VEGF) genes delivered transendocardially with magnetic resonance (MR) imaging guidance may neovascularize or improve vascular recruitment in occlusive infarction.

MATERIALS AND METHODS

All experimental procedures received approval from the institutional committee on animal research. Dogs with permanent coronary artery occlusion were imaged twice (3 days after occlusion for assessment of acute infarction; a mean of 50 days after occlusion +/- 3 [standard error of the mean] for assessment of chronic infarction). A mixture of plasmid VEGF and plasmid LacZ (n = 6, treated animals) or plasmid LacZ and sprodiamide (n = 6, placebo control animals) was delivered to four sites. MR fluoroscopy was used to target and monitor delivery of genes. The effectiveness of this delivery approach was determined by using MR imaging methods to assess perfusion, left ventricular (LV) function, myocardial viability, and infarct resorption. Histologic evaluation of neovascularization was then performed.

RESULTS

MR fluoroscopic guidance of injectates was successful in both groups. Treated animals with chronic, but not those with acute, infarction showed the following differences compared with control animals: (a) steeper mean maximum upslope perfusion (200 sec(-1) +/- 32 vs 117 sec(-1) +/- 15, P = .02), (b) higher peak signal intensity (1667 arbitrary units +/- 100 vs 1132 arbitrary units +/- 80, P = .002), (c) increased ejection fraction (from 27.9% +/- 1.2 to 35.3% +/- 1.6, P = .001), (d) smaller infarction size (as a percentage of LV mass) at MR imaging (8.5% +/- 0.9 vs 11.3% +/- 0.9, P = .048) and triphenyltetrazolium chloride staining (9.4% +/- 1.5 vs 12.7% +/- 0.4, P = .05), and (e) higher vascular density (as number of vessels per square millimeter) at the border (430 +/- 117 vs 286 +/- 19, P = .0001) and core (307 +/- 112 vs 108 +/- 17, P = .0001).

CONCLUSION

The validity of plasmid VEGF gene delivered with MR fluoroscopic guidance into occlusive infarction was confirmed by neovascularization associated with improved perfusion, LV function, and infarct resorption.

Overexpression of netrin-1 induces neovascularization in the adult mouse brain

Netrin-1 is a critical molecule for axonal pathfinding during embryo development, and because of its structural homology to the endothelial mitogens, it may share its effects on vascular network formation. Using an adeno-associated viral netrin-1 vector (AAV-NT-1) gene transfer, we demonstrated that netrin-1 was able to stimulate the proliferation and migration of human cerebral endothelial cells (HCECs) and human aortic smooth muscle cells (HASMCs) compared with the control (P<0.05), and could also promote HCEC tube formation on matrigel (P<0.05) in vitro. Moreover, netrin-1 hyperstimulation could promote focal neovascularization (P<0.05) in the adult brain in vivo. Unlike VEGF-induced microvessel increase, netrin-1-induced newly formed vessels showed an artery-like phenotype, with an intact endothelial cell monolayer surrounded by multiple cell layers, including smooth muscle cells and an astrocyte-connected outer layer. Our findings suggest that netrin-1 plays an important role in promoting blood vessel formation in the adult rodent central nervous system, and could have broad implication in cerebrovascular development and remodeling.

Treatment of chronical myocardial ischemia by adenovirus-mediated hepatocyte growth factor gene transfer in minipigs

Growth factor gene transfer-induced therapeutic angiogenesis has become a novel approach for the treatment of myocardial ischemia. In order to provide a basis for the clinical application of an adenovirus with hepatocyte growth factor gene (Ad-HGF) in the treatment of myocardial ischemia, we established a minipig model of chronically ischemic myocardium in which an Ameroid constrictor was placed around the left circumflex branch of the coronary artery (LCX). A total of 18 minipigs were randomly divided into 3 groups: a surgery control group, a model group and an Ad-HGF treatment group implanted with Ameroid constrictor. Ad-HGF or the control agent was injected directly into the ischemic myocardium, and an improvement in heart function and blood supply were evaluated. The results showed that myocardial perfusion remarkably improved in the Ad-HGF group compared with that in both the control and model groups. Four weeks after the treatment, the density of newly formed blood vessels was higher and the number of collateral blood vessels was greater in the Ad-HGF group than in the model group. The area of myocardial ischemia reduced evidently and the left ventricular ejection fraction improved significantly in the Ad-HGF group. These results suggest that HGF gene therapy may become a novel approach in the treatment of chronically ischemic myocardium.