Angiogenic and cardiac functional effects of dual gene transfer of VEGF-A165 and PDGF-BB after myocardial infarction

Risk gene identification and support vector machine learning to construct an early diagnosis model of myocardial infarction

The present study aimed to identify genes associated with increased risk of myocardial infarction (MI) and construct an early diagnosis model based on support vector machine (SVM) learning. The gene expression profile data of GSE34198, containing 97 human blood samples including 49 patients with MI and 48 healthy individuals, were obtained from the Gene Expression Omnibus database. Differentially expressed gene (DEG) screening, DEG enrichment analysis, protein-protein interaction (PPI) network investigation and clustering analysis were performed. The feature genes were identified using the neighboring score algorithm. Furthermore, a recursive feature elimination (RFE) algorithm was employed to screen risk factors among feature genes. The SVM prediction model was constructed and validated using the dataset GSE61144. A total of 1,207 DEGs (724 downregulated, 483 upregulated) between the two groups were identified. PPI analysis investigated 1,083 DEGs and 46,363 edges. In total, 87 genes were selected as candidate genes, and were primarily enriched in functions including ‘G-protein coupled receptor signaling’ or pathways such as ‘focal adhesion’. Furthermore, 15 genes with a high RFE score were selected to construct an SVM prediction model. The model's average accuracy was 86%. Data set verification showed that the predictive precision reached 0.92. High expression of the genes vascular endothelial growth factor A, A-kinase anchoring protein 12 and olfactory receptor 8D2 were potential risk factors for MI. The SVM early diagnosis model constructed by candidate genes could not only predict early MI, but also provide risk probability according to the severity of MI.

Does the association between serum endostatin, an endogenous anti-angiogenic protein, and acute myocardial infarction differ by race?

Endostatin, an endogenous anti-angiogenic protein, has been linked to reduced atherosclerosis in animal models. We conducted a nested case-control study to ascertain whether decreased circulating endostatin might be associated with increased odds of acute myocardial infarction (AMI) and whether this association varied by sex or race. Cases were 211 subjects who subsequently developed AMI, and controls were 173 subjects free of cardiovascular disease matched on age, sex, race and follow-up time. In conditional logistic regression adjusting for traditional risk factors, the odds ratio of AMI per 1 SD increment in endostatin was 0.85 (95% confidence interval, 0.73-1.00). This association varied by race (but not by sex) such that a statistically significant inverse relation was found among Asians and white individuals and a significant positive relation among black individuals. Further research is needed to replicate these findings and to elucidate potential mechanisms for these race/ethnic differences.

Sequential delivery of angiogenic growth factors improves revascularization and heart function after myocardial infarction

Treatment of ischemia through therapeutic angiogenesis faces significant challenges. Growth factor (GF)-based therapies can be more effective when concerns such as GF spatiotemporal presentation, bioactivity, bioavailability, and localization are addressed. During angiogenesis, vascular endothelial GF (VEGF) is required early to initiate neovessel formation while platelet-derived GF (PDGF-BB) is needed later to stabilize the neovessels. The spatiotemporal delivery of multiple bioactive GFs involved in angiogenesis, in a close mimic to physiological cues, holds great potential to treat ischemic diseases. To achieve sequential release of VEGF and PDGF, we embed VEGF in fibrin gel and PDGF in a heparin-based coacervate that is distributed in the same fibrin gel. In vitro, we show the benefits of this controlled delivery approach on cell proliferation, chemotaxis, and capillary formation. A rat myocardial infarction (MI) model demonstrated the effectiveness of this delivery system in improving cardiac function, ventricular wall thickness, angiogenesis, cardiac muscle survival, and reducing fibrosis and inflammation in the infarct zone compared to saline, empty vehicle, and free GFs. Collectively, our results show that this delivery approach mitigated the injury caused by MI and may serve as a new therapy to treat ischemic hearts pending further examination.

High number of transplanted stem cells improves myocardial recovery after AMI in a porcine model

OBJECTIVE

The clinical data considering the bone marrow mononuclear cell (BMMNC) therapy in treatment for acute myocardial infarction (AMI) are controversial and the mechanisms remain unknown. Our objective was to study the cardiac function and changes in cytokine levels after administration of BMMNC in experimental AMI model.

DESIGN

Unlabeled or Super-Paramagnetic-Iron-Oxide-labeled BMMNCs or saline was injected into myocardium of 31 pigs after circumflex artery occlusion. Ejection fraction (EF) was measured preoperatively, postoperatively and at 21 days by echocardiography. Cardiac MRI was performed postoperatively and after 21 days in 7 BMMNC animals. Serum cytokine levels were measured at baseline, 24 h and 21 days. Cellular homing was evaluated comparing MRI and histology.

RESULTS

From baseline to 21 days EF decreased less in BMMNC group (EF mean control -19 SD 12 vs. BMMNC -4 SD 15 percentage points p = 0.02). Cytokine concentrations showed high variability between the animals. MRI correlated with histology in cell detection and revealed BMMNCs in the infarction area. By MRI, EF improved 11 percentage points. The improvement in EF was associated with the number of transplanted BMMNCs detected in the myocardium.

CONCLUSION

BMMNC injection after AMI improved cardiac function. Quantity of transplanted BMMNCs correlated with the improvement in cardiac function after AMI.

Peptide-loaded nanoparticles and radionuclide imaging for individualized treatment of myocardial ischemia

PURPOSE

To determine whether chitosan hydrogel nanoparticles loaded with vascular endothelial growth factor (VEGF) peptides (81-91 fragments) capable of targeting the ischemic myocardium enhance angiogenesis and promote therapeutic effects and whether radionuclide image-guided dosage control is feasible.

MATERIALS AND METHODS

Experimental procedures and protocols were approved by the Institutional Animal Care and Use Committee. Rats (n = 32, eight per group) were subjected to myocardial ischemia (control group) and received chitosan hydrogel nanoparticles with VEGF165 proteins (chitosan VEGF) or VEGF81-91 peptides (chitosan peptides) via apical puncture. Ischemic hearts receiving chitosan without angiogenic factors served as the chitosan control. Myocardial perfusion was examined 7 days after surgery by using technetium 99m ((99m)Tc) tetrofosmin (37 MBq) autoradiography, and changes in vascular density with immunohistochemical staining were reviewed. Kruskal-Wallis test and Bonferroni corrected Mann-Whitney U test were used for multiple comparisons. Wilcoxon signed rank test was used to compare myocardial retention of (99m)Tc chitosan.

RESULTS

Thirty minutes of myocardial ischemia resulted in perfusion defects (median, 54%; interquartile range [IQR], 41%-62%). Chitosan VEGF decreased perfusion defect extent (median, 68%; IQR, 63%-73%; P = .006 vs control) and increased vascular density (median, 81 vessels per high-power field; IQR, 72-100; P = .009 vs control). Administration of chitosan peptides reduced the degree of perfusion defects (median, 66%; IQR, 62%-73%; P = .006 vs control) and increased vascular density (median, 82 vessels; IQR, 78-92; P = .006 vs control). The effects of chitosan peptides on perfusion and vascular density were comparable to those seen with chitosan VEGF proteins (P = .713 and P = .833, respectively). Chitosan radiolabeled with (99m)Tc was administered twice at reperfusion with a 1-hour interval to determine whether image-guided dosage control is feasible. The hearts initially retained 4.6% (IQR, 4.1%-5.0%) of (99m)Tc chitosan administered and 9.2% (IQR, 6.6%-12.7%; P = .068) with subsequent injection.

CONCLUSION

VEGF peptides have angiogenic potential and resulted in therapeutic effectiveness. Adjunct use of single photon emission computed tomography was also demonstrated for individualized treatment of myocardial ischemia by further tailoring the therapeutic dosing. Online supplemental material is available for this article.

Sustaining neovascularization of a scaffold through staged release of vascular endothelial growth factor-A and platelet-derived growth factor-BB

Tissue regeneration into a three-dimensional scaffold requires the stimulation of blood vessel ingrowth. We have employed a freely interconnecting porous scaffold developed by us to determine the utility of a covalently bound heparin surface coating for the delivery of vascular endothelial growth factor (VEGF) and platelet-derived growth factor BB (PDGF-BB) in vivo. The heparin surface was shown to release VEGF far more rapidly than PDGF-BB in vitro (VEGF: 75 ng/h for 24 h; PDGF-BB: 86 pg/h for >7 days). In rat subcutaneous implants, at 10 days the heparin surface alone increased vessel ingrowth substantially (p<0.05 vs. unmodified scaffold), release of VEGF resulted in a further increase (p<0.05 vs. heparinized scaffold), whereas PDGF-BB had no additional effect. The increase induced by the combination of growth factors was similar to VEGF alone. After 2 months, PDGF-BB, but not VEGF delivery, resulted in a substantial increase in vascularization above that induced by heparin (p<0.05). At the longer time point the combination of growth factors was similar to PDGF-BB. However, only the combination of growth factors significantly elevated the number of ingrowing arterioles (p<0.05 vs. heparinized scaffold). Thus, the covalent modification of a porous scaffold with heparin allows for the differential release of VEGF and PDGF-BB that results in both a rapid and sustained increase in scaffold vascularization.

The paracrine effect: pivotal mechanism in cell-based cardiac repair

Cardiac cell therapy has emerged as a controversial yet promising therapeutic strategy. Both experimental data and clinical applications in this field have shown modest but tangible benefits on cardiac structure and function and underscore that transplanted stem-progenitor cells can attenuate the postinfarct microenvironment. The paracrine factors secreted by these cells represent a pivotal mechanism underlying the benefits of cell-mediated cardiac repair. This article reviews key studies behind the paracrine effect related to the cardiac reparative effects of cardiac cell therapy.

Stem cell therapy with overexpressed VEGF and PDGF genes improves cardiac function in a rat infarct model

Background

Therapeutic potential was evaluated in a rat model of myocardial infarction using nanofiber-expanded human cord blood derived hematopoietic stem cells (CD133+/CD34+) genetically modified with VEGF plus PDGF genes (VIP).

Methods and Findings

Myocardial function was monitored every two weeks up to six weeks after therapy. Echocardiography revealed time dependent improvement of left ventricular function evaluated by M-mode, fractional shortening, anterior wall tissue velocity, wall motion score index, strain and strain rate in animals treated with VEGF plus PDGF overexpressed stem cells (VIP) compared to nanofiber expanded cells (Exp), freshly isolated cells (FCB) or media control (Media). Improvement observed was as follows: VIP>Exp> FCB>media. Similar trend was noticed in the exercise capacity of rats on a treadmill. These findings correlated with significantly increased neovascularization in ischemic tissue and markedly reduced infarct area in animals in the VIP group. Stem cells in addition to their usual homing sites such as lung, spleen, bone marrow and liver, also migrated to sites of myocardial ischemia. The improvement of cardiac function correlated with expression of heart tissue connexin 43, a gap junctional protein, and heart tissue angiogenesis related protein molecules like VEGF, pNOS3, NOS2 and GSK3. There was no evidence of upregulation in the molecules of oncogenic potential in genetically modified or other stem cell therapy groups.

Conclusion

Regenerative therapy using nanofiber-expanded hematopoietic stem cells with overexpression of VEGF and PDGF has a favorable impact on the improvement of rat myocardial function accompanied by upregulation of tissue connexin 43 and pro-angiogenic molecules after infarction.

Effect of traditional Chinese medicine Shu-mai-tang on angiogenesis, arteriogenesis and cardiac function in rats with myocardial ischemia

Ischemic heart disease is one of the leading causes of morbidity and mortality worldwide. Shu-mai-tang (SMT) is a traditional Chinese medicine for the treatment of ischemic heart disease. To better understand the underlying cardioprotection mechanisms of SMT on myocardial ischemia (MI), the effect of SMT on angiogenesis, arteriogenesis and cardiac function was investigated in a rat model of MI, as well as the potential mechanism. Rats with a ligated left anterior descending coronary artery (MI model) were randomized (24 rats/group) to receive SMT/LY294002 [phosphatidylinositol 3-kinase (PI3K) inhibitor], SMT or no treatment. A sham-operation group was included. It was demonstrated that 2 and 4 weeks after treatment the oral administration of SMT significantly increased capillaries and arterioles, suppressed myocardial fibrosis, as well as significantly increased cardiac phosphorylation of Akt, vascular endothelial growth factor (VEGF) and platelet-derived growth factor (PDGF-BB) levels and functional improvement. PI3K inhibitor down-regulated SMT-induced angiogenesis and arteriogenesis. These novel therapeutic properties of SMT to induce the reconstitution of stable blood supply networks, reverse LV remodeling may offer an alternative therapy for the treatment of ischemic heart disease. The potential mechanism may be that SMT promotes VEGF and PDGF-BB-mediated angiogenesis and arteriogenesis through the PI3K/Akt signaling pathway.

Ex vivo nanofiber expansion and genetic modification of human cord blood-derived progenitor/stem cells enhances vasculogenesis

The stem cell therapy for treating ischemic diseases is promising; however, the limited availability and compromised quality of progenitor cells in aged and diseased patients limit its therapeutic use. Here we report a nanofiber-based ex vivo stem cell expansion technology and proangiogenic growth factors overexpression of human umbilical cord blood (UCB)-derived progenitor cells to enhance angiogenic potential of therapeutic stem cells. The progenitor cells were expanded approximately 225-fold on nanofiber-based serum-free ex vivo expansion culture technique without inducing differentiation. The expanded cells express high levels of stem cell homing receptor, CXCR4, and adhesion molecule, LFA-1. The nanofiber-expanded stem cells uptake AcLDL effectively, and migrate efficiently in an in vitro transmigration assay. These expanded cells can also differentiate into endothelial and smooth muscle cells in vitro. In a NOD/SCID mouse hind limb vascular injury model, nanofiber-expanded cells were more effective in blood flow restoration and this effect was further augmented by VEGF(164) and PDGF-BB, growth factor overexpression. The data indicate that nanofiber-based ex vivo expansion technology can provide an essential number of therapeutic stem cells. Additionally, proangiogenic growth factors overexpression in progenitor cells can potentially improve autologous or allogeneic stem cell therapy for ischemic diseases.

Design of biodegradable hydrogel for the local and sustained delivery of angiogenic plasmid DNA

PURPOSE

To attain the effective local and sustained delivery of plasmid DNA (pDNA) encoding for a growth factor.

METHODS

We hypothesized that controlling the degradation rate of biomaterials encapsulating pDNA via concurrent physical dissociation of the cross-linked structure and hydrolytic chain breakage of polymers would allow one to significantly broaden the range of pDNA release rate. This hypothesis was examined using ionically cross-linked polysaccharide hydrogels which were previously designed to rapidly degrade via engineering of ionic cross-linking junction and partial oxidation of polysaccharide chains.

RESULTS

The hydrogel degradation rates were varied over the broad range, and pDNA release correlated with the gel degradation rate. Degradable hydrogels were used for the local and sustained delivery of a pDNA encoding for vascular endothelial growth factor (VEGF) in the ischemic hindlimbs of mice, and local pDNA release significantly improved the recovery of blood perfusion as compared with a bolus injection of VEGFencoding pDNA.

CONCLUSION

This strategy to control the hydrogel degradation rate may be useful in regulating the delivery of a broad array of macromolecular drugs, and subsequently improve their therapeutic efficacy.

Intramyocardial injection of vascular endothelial growth factor gene improves cardiac performance and inhibits cardiomyocyte apoptosis

BACKGROUND

Previous studies suggest that vascular endothelial growth factor (VEGF) is a regulator of naturally occurring angiogenesis. However, whether VEGF plays a role in cardiomyocyte apoptosis is not known.

AIM

To investigate the effects of intramyocardial injection of VEGF165 cDNA on cardiac performance and cardiomyocyte apoptosis in a rat model of acute myocardial infarction.

METHODS

Forty male Sprague-Dawley rats underwent left coronary artery ligation and were randomised to receive VEGF165 cDNA (treated group) or pcDNA3.1 (control), injected directly into the border zone of the ischaemic myocardium. Twenty rats underwent thoracotomy and injection of pcDNA3.1, without coronary ligation (sham group). Haemodynamic and apoptotic parameters were measured two weeks after injection.

RESULTS

Three sham, eight control, and five treated animals died. Haemodynamic parameters and microvessel counts in the treated group were significantly better than in the control (P<0.05 to 0.01). Apoptotic index in the treated group was less than in the control (P<0.01). Caspase-3 activation and mitochondrial cytochrome c release in the treated group were also lower than in the control (P<0.01). VEGF165 cDNA treatment significantly inhibited p53, Fas, Bax, and increased VEGF and Bcl-2 expression in the myocardium.

CONCLUSION

Intramyocardial injection of VEGF165 cDNA significantly improved cardiac performance, stimulated angiogenesis and reduced cardiomyocyte apoptosis, in a rat model of acute myocardial infarction.

Vascular Wall Maturation and Prolonged Angiogenic Effect by Endothelial-Specific Platelet-Derived Growth Factor Expression

BACKGROUND

The implementation of angiogenic gene therapy at clinics is hindered by the transience of the therapeutic effect. Recruiting vascular wall smooth muscle cells, a process termed 'maturation', can stabilize newly formed vessels.

OBJECTIVE

To induce angiogenesis followed by vessel maturation in a murine ischemic limb model by endothelial cell-specific promoter regulated expression of vascular endothelial growth factor (VEGF) and platelet-derived growth factor-BB (PDGF-BB).

METHODS

We constructed adenoviral vectors containing angiogenic factors VEGF and PDGF-B regulated by a modified preproendothelin-1 (PPE-1-3x) promoter and investigated their angiogenic effect in a murine ischemic limb model.

RESULTS

VEGF gene therapy increased perfusion and the vessel density in the limb shortly after expression with PPE-1-3x promoter or cytomegalovirus (CMV) promoter vectors, but only PPE-1-3xVEGF treatment exhibited a sustained effect. Expression of PDGF-B by PPE-1-3x promoter resulted in morphological maturation of the vasculature and further increased the perfusion, while nonspecific expression of PDGF-B with CMV promoter had no therapeutic effect. Regulation of dual therapy with VEGF and PDGF-B by PPE-1-3x promoter resulted in an early-onset, sustained angiogenic effect accompanied by vessel maturation.

CONCLUSIONS

Systemic gene therapy with the angiogenic factors VEGF and PDGF-B under angiogenic- endothelial cell-specific regulation was effective in inducing functionally and morphologically mature vasculature.

Plasmid-mediated VEGF gene transfer induces cardiomyogenesis and reduces myocardial infarct size in sheep

We have recently reported that in pigs with chronic myocardial ischemia heart transfection with a plasmid encoding the 165 isoform of human vascular endothelial growth factor (pVEGF165) induces an increase in the mitotic index of adult cardiomyocytes and cardiomyocyte hyperplasia. On these bases we hypothesized that VEGF gene transfer could also modify the evolution of experimental myocardial infarct. In adult sheep pVEGF165 (3.8 mg, n=7) or empty plasmid (n=7) was injected intramyocardially 1 h after coronary artery ligation. After 15 days infarct area was 11.3+/-1.3% of the left ventricle in the VEGF group and 18.2+/-2.1% in the empty plasmid group (P<0.02). The mechanisms involved in infarct size reduction (assessed in additional sheep at 7 and 10 days after infarction) included an increase in early angiogenesis and arteriogenesis, a decrease in peri-infarct fibrosis, a decrease in myofibroblast proliferation, enhanced cardiomyoblast proliferation and mitosis of adult cardiomyocytes with occasional cytokinesis. Resting myocardial perfusion (99mTc-sestamibi SPECT) was higher in VEGF-treated group than in empty plasmid group 15 days after myocardial infarction. We conclude that plasmid-mediated VEGF gene transfer reduces myocardial infarct size by a combination of effects including neovascular proliferation, modification of fibrosis and cardiomyocyte regeneration.

alphaB-crystallin is phosphorylated during myocardial infarction: involvement of platelet-derived growth factor-BB

alphaB-crystallin is the most abundant low-molecular-weight heat shock protein in heart and recent studies have demonstrated that it plays a cardioprotective role during myocardial infarction both in vivo and in vitro. On the other hand, platelet-derived growth factor (PDGF), a potent serum mitogen, has been reported to improve cardiac function after myocardial infarction. In the present study, using a mouse myocardial infarction model, we investigated whether alphaB-crystallin is phosphorylated during myocardial infarction and the implication of PDGF-BB. Phosphorylation of alphaB-crystallin at Ser-59 was time dependently induced and plasma PDGF-BB levels were concomitantly increased. Moreover, PDGF-BB-stimulated phosphorylation of alphaB-crystallin was suppressed by SB203580, a specific inhibitor of p38 mitogen-activated protein (MAP) kinase, in primary cultured cardiac myocytes. Our results indicate that PDGF-BB induces phosphorylation of alphaB-crystallin via p38 MAP kinase during myocardial infarction.