Effect of basic fibroblast growth factor on angiogenesis in the infarcted porcine heart

Preparation of Cell-Seeded Heart Patch In Vitro; Co-Culture of Adipose-Derived Mesenchymal Stem Cell and Cardiomyocytes in Amnion Bilayer Patch

INTRODUCTION

Cardiovascular disease is the second killer across the globe, while coronary disease is the major cause. Cell therapy is one alternative to regenerate the infarcted heart wall.

MATERIALS AND METHODS

In this study, the cardiomyogenesis capacity of human adipose stem cells (hAdSC) and human cardiomyocytes (hCardio) cultured in a 3-D biological scaffold (decellularised amnion bilayer) for nine days in a static condition was investigated. The cardiomyogenesis capacity of hAdSC were identified using immunohistochemistry and RT-PCR. The population of the cells isolated from the heart tissue expressed cTnT-1 (13.38 ± 11.38%), cKit (7.85 ± 4.2%), ICAM (85.53 ± 8.69%), PECAM (61.63 ± 7.18%) and VCAM (35.9 ± 9.11%), while from the fat tissue expressed the mesenchymal phenotypes (CD73, CD90, CD105, but not CD45, CD34, CD11b, CD19 and HLA-DR). Two age groups of hAdSC donors were compared, the youngsters (30-40yo) and the elderly (60-70 yo).

RESULTS

The co-culture showed that after 5-day incubation, the seeded graft in the hAdSC-30 group had a tube-like appearance while the hAdSC-60 group demonstrated a disorganised pattern, despite of the MSC expressions of the hAdSC-60 were significantly higher. Initial co-culture showed no difference of ATP counts among all groups, however the hAdSC-30 group had the highest ATP count after 9 days culture (p = 0.004). After normalising to the normal myocardium, only the hAdSC-60 group expressed cTnT and MHC, very low, seen during the initial cultivation, but then disappeared. Meanwhile, the hAdSC-30 group expressed α-actinin, MHC and cTnT in the Day-5. The PPAR also was higher in the Day-5 compared to the Day-9 (p < 0.005).

CONCLUSION

Cardiomyogenesis capacity of hAdSC co-cultured with hCardio in a 3-D scaffold taken from the 30-40yo donor showed better morphology and viability than the 60-70yo group, but maintained less than 5 days in this system.

Neovascularization of engineered tissues for clinical translation: Where we are, where we should be?

One of the key challenges in engineering three-dimensional tissue constructs is the development of a mature microvascular network capable of supplying sufficient oxygen and nutrients to the tissue. Recent angiogenic therapeutic strategies have focused on vascularization of the constructed tissue, and its integration in vitro; these strategies typically combine regenerative cells, growth factors (GFs) with custom-designed biomaterials. However, the field needs to progress in the clinical translation of tissue engineering strategies. The article first presents a detailed description of the steps in neovascularization and the roles of extracellular matrix elements such as GFs in angiogenesis. It then delves into decellularization, cell, and GF-based strategies employed thus far for therapeutic angiogenesis, with a particularly detailed examination of different methods by which GFs are delivered in biomaterial scaffolds. Finally, interdisciplinary approaches involving advancement in biomaterials science and current state of technological development in fabrication techniques are critically evaluated, and a list of remaining challenges is presented that need to be solved for successful translation to the clinics.

Loss of m6A demethylase ALKBH5 promotes post-ischemic angiogenesis via post-transcriptional stabilization of WNT5A

BACKGROUND

Post-ischemic angiogenesis is critical for blood flow recovery and ischemic tissue repair. N6-methyladenosine (m6A) plays essential roles in numerous biological processes. However, the impact and connected mechanism of m6A on post-ischemic angiogenesis are not fully understood.

METHODS

AlkB homolog 5 (ALKBH5) was screened out among several methyltransferases and demethylases involved in dynamic m6A regulation. Cardiac microvascular endothelial cells (CMECs) angiogenesis and WNT family member 5A (WNT5A) stability were analyzed upon ALKBH5 overexpression with adenovirus or knockdown with small interfering RNAs in vitro. The blood flow recovery, capillary, and small artery densities were evaluated in adeno-associated virus (AAV)-ALKBH5 overexpression or ALKBH5 knockout (KO) mice in a hind-limb ischemia model. The same experiments were conducted to explore the translational value of transient silencing of ALKBH5 with adenovirus.

RESULTS

ALKBH5 was significantly upregulated in hypoxic CMECs and led to a global decrease of m6A level. ALKBH5 overexpression further reduced m6A level in normoxic and hypoxic CMECs, impaired proliferation, migration, and tube formation only in hypoxic CMECs. Conversely, ALKBH5 knockdown preserved m6A levels and promoted angiogenic phenotypes in hypoxic but not in normoxic CMECs. Mechanistically, ALKBH5 regulated WNT5A expression through post-transcriptional mRNA modulation in an m6A-dependent manner, which decreased its stability and subsequently impeded angiogenesis in hypoxic CMECs. Furthermore, ALKBH5 overexpression hindered blood flow recovery and reduced CD31 and alpha-smooth muscle actin expression in hind-limb ischemia mice. As expected, ALKBH5-KO mice exhibited improved blood flow recovery, increased capillary, and small artery densities after hind-limb ischemia, and similar beneficial effects were observed in mice with transient adenoviral ALKBH5 gene silencing.

CONCLUSION

We demonstrate that ALKBH5 is a negative regulator of post-ischemic angiogenesis via post-transcriptional modulation and destabilization of WNT5A mRNA in an m6A-dependent manner. Targeting ALKBH5 may be a potential therapeutic option for ischemic diseases, including peripheral artery disease.

Application of Cell, Tissue, and Biomaterial Delivery in Cardiac Regenerative Therapy

Cardiovascular diseases (CVD) are the leading cause of death around the world, being responsible for 31.8% of all deaths in 2017 (Roth, G. A. et al. The Lancet 2018, 392, 1736-1788). The leading cause of CVD is ischemic heart disease (IHD), which caused 8.1 million deaths in 2013 (Benjamin, E. J. et al. Circulation 2017, 135, e146-e603). IHD occurs when coronary arteries in the heart are narrowed or blocked, preventing the flow of oxygen and blood into the cardiac muscle, which could provoke acute myocardial infarction (AMI) and ultimately lead to heart failure and death. Cardiac regenerative therapy aims to repair and refunctionalize damaged heart tissue through the application of (1) intramyocardial cell delivery, (2) epicardial cardiac patch, and (3) acellular biomaterials. In this review, we aim to examine these current approaches and challenges in the cardiac regenerative therapy field.

Delivery of drugs, growth factors, genes and stem cells via intrapericardial, epicardial and intramyocardial routes for sustained local targeted therapy of myocardial disease

INTRODUCTION

Local myocardial delivery (LMD) of therapeutic agents is a promising strategy that aims to treat various myocardial pathologies. It is designed to deliver agents directly to the myocardium and minimize their extracardiac concentrations and side effects. LMD aims to enhance outcomes of existing therapies by broadening their therapeutic window and to utilize new agents that could not be otherwise be implemented systemically. Areas covered: This article provides a historical overview of six decades LMD evolution in terms of the approaches, including intrapericardial, epicardial, and intramyocardial delivery, and the wide array of classes of agents used to treat myocardial pathologies. We examines delivery of pharmaceutical compounds, targeted gene transfection and cell implantation techniques to produce therapeutic effects locally. We outline therapeutic indications, successes and failures as well as technical approaches for LMD. Expert opinion: While LMD is more complicated than conventional oral or intravenous administration, given recent advances in interventional cardiology, it is safe and may provide better therapeutic outcomes. LMD is complex as many factors impact pharmacokinetics and biologic result. The choice between routes of LMD is largely driven not only by the myocardial pathology but also by the nature and physicochemical properties of the therapeutic agents.

The bottleneck stent model for chronic myocardial ischemia and heart failure in pigs

A large animal model of chronic myocardial ischemia and heart failure is crucial for the development of novel therapeutic approaches. In this study we developed a novel percutaneous one- and two-vessel model for chronic myocardial ischemia using a stent coated with a polytetrafluoroethylene tube formed in a bottleneck shape. The bottleneck stent was implanted in the proximal left anterior descending (LAD) or proximal circumflex artery (LCX), or in both proximal LCX and mid LAD 1 wk later (2-vessel model), and pigs were followed for 4–5 wk. Ejection fraction (EF), infarct size, collateral growth, and myocardial perfusion were assessed. Pigs were given antiarrhythmic medication to prevent sudden death. The occlusion time of the bottleneck stent and the timing of myocardial infarction could be modulated by the duration of antiplatelet medication. Fractional flow reserve measurements and positron emission tomography imaging showed severe ischemia after bottleneck stenting covering over 50% of the left ventricle in the proximal LAD model. Complete coronary occlusion was necessary for significant collateral growth, which mostly had occurred already during the first wk after the stent occlusion. Dynamic and competitive collateral growth patterns were observed. EF declined from 64 to 41% in the LCX model and to 44% in the LAD model 4 wk after stenting with 12 and 21% infarcted left ventricle in the LCX and LAD models, respectively. The mortality was 32 and 37% in the LCX and LAD models but very (71%) high in the two-vessel disease model. The implantation of a novel bottleneck stent in the proximal LAD or LCX is a novel porcine model of reversible myocardial ischemia (open stent) and ischemic heart failure (occluded stent) and is feasible for the development of new therapeutic approaches.

Angiogenesis in the infarcted myocardium

SIGNIFICANCE

Proangiogenic therapy appeared a promising strategy for the treatment of patients with acute myocardial infarction (MI), as de novo formation of microvessels, has the potential to salvage ischemic myocardium at early stages after MI, and is also essential to prevent the transition to heart failure through the control of cardiomyocyte hypertrophy and contractility.

RECENT ADVANCES

Exciting preclinical studies evaluating proangiogenic therapies for MI have prompted the initiation of numerous clinical trials based on protein or gene transfer delivery of growth factors and administration of stem/progenitor cells, mainly from bone marrow origin. Nonetheless, these clinical trials showed mixed results in patients with acute MI.

CRITICAL ISSUES

Even though methodological caveats, such as way of delivery for angiogenic growth factors (e.g., protein vs. gene transfer) and stem/progenitor cells or isolation/culture procedure for regenerative cells might partially explain the failure of such trials, it appears that delivery of a single growth factor or cell type does not support angiogenesis sufficiently to promote cardiac repair.

FUTURE DIRECTIONS

Optimization of proangiogenic therapies might include stimulation of both angiogenesis and vessel maturation and/or the use of additional sources of stem/progenitor cells, such as cardiac progenitor cells. Experimental unraveling of the mechanisms of angiogenesis, vessel maturation, and endothelial cell/cardiomyocyte cross talk in the ischemic heart, analysis of emerging pathways, as well as a better understanding of how cardiovascular risk factors impact endogenous and therapeutically stimulated angiogenesis, would undoubtedly pave the way for the development of novel and hopefully efficient angiogenesis targeting therapeutics for the treatment of acute MI.

Promoting blood vessel growth in ischemic diseases: challenges in translating preclinical potential into clinical success

Angiogenic therapy, which involves the use of an exogenous stimulus to promote blood vessel growth, is an attractive approach for the treatment of ischemic diseases. It has been shown in animal models that the stimulation of blood vessel growth leads to the growth of the whole vascular tree, improvement of ischemic tissue perfusion and improved muscle aerobic energy metabolism. However, very few positive results have been gained from Phase 2 and 3 clinical angiogenesis trials. Many reasons have been given for the failures of clinical trials, including poor transgene expression (in gene-therapy trials) and instability of the vessels induced by therapy. In this Review, we discuss the selection of preclinical models as one of the main reasons why clinical translation has been unsuccessful thus far. This issue has received little attention, but could have had dramatic implications on the expectations of clinical trials. We highlight crucial differences between human patients and animal models with regards to blood flow and pressure, as well as issues concerning the chronic nature of ischemic diseases in humans. We use these as examples to demonstrate why the results from preclinical trials might have overestimated the efficacy of angiogenic therapies developed to date. We also suggest ways in which currently available animal models of ischemic disease could be improved to better mimic human disease conditions, and offer advice on how to work with existing models to avoid overestimating the efficacy of new angiogenic therapies.

Therapeutical potential of autologous peripheral blood mononuclear cell transplantation in patients with type 2 diabetic critical limb ischemia

AIM

The aim was to evaluate the therapeutic effectiveness of granulocyte colony-stimulating factor (G-CSF) mobilized peripheral blood mononuclear cells (PBMNCs) in critical limb ischemia (CLI) of type 2 diabetic patients.

METHOD

Forty diabetic patients with CLI were enrolled and randomized to treatment and control groups. In the treatment group, the patients received subcutaneous injections of recombinant human G-CSF (30 MU/day) for 5 days to mobilize stem cells. PBMNCs were collected and transplanted by multiple intramuscular injections of 1 ml in 1-1.5-cm depth into ischemic limbs.

RESULTS

At the end of 12 weeks of follow-up, the baseline and end point results in transplant group were as follows: Fontaine score improved from 3.8±03 to 3±0.5 (P=.0001), ankle brachial pressure index increased from 0.68±0.24 to 0.87±024 (P=.001), transcutaneous oxygen increased from 33±14 mmHg to 44±10 mmHg (P=.0001), and 6-min walking distance improved from 280±82 m to 338±98 m (P=.0001). Pain score decreased from 8.2±1.3 to 5.63±1.6 (P=.001), and the number of patients with limb ulcers was reduced from 9/20 (45%) to 3/20 (15%) (P=.031). In the control group, Fontaine score, 6-min walking distance, and pain score were improved; ankle brachial pressure index and transcutaneous oxygen pressure were not improved. The number of patients with limb ulcers did not change in the control group. There are improvement in amputation rates, collateral vessel development, and number of limb ulcers healed.

CONCLUSIONS

These results indicate that the autologous transplantation of G-CSF that mobilized PBMNCs in CLI diabetic patients is safe and effective in patient compliant reduction and improved perfusion.

Vascular regeneration by local growth factor release is self-limited by microvascular clearance

BACKGROUND

The challenge of angiogenesis science is that stable sustained vascular regeneration in humans has not been realized despite promising preclinical findings. We hypothesized that angiogenic therapies powerfully self-regulate by dynamically altering tissue characteristics. Induced neocapillaries increase drug clearance and limit tissue retention and subsequent angiogenesis even in the face of sustained delivery.

METHODS AND RESULTS

We quantified how capillary flow clears fibroblast growth factor after local epicardial delivery. Fibroblast growth factor spatial loading was significantly reduced with intact coronary perfusion. Penetration and retention decreased with transendothelial permeability, a trend diametrically opposite to intravascular delivery, in which factor delivery depends on vascular leak, but consistent with a continuum model of drug transport in perfused tissues. Model predictions of fibroblast growth factor sensitivity to manipulations of its diffusivity and transendothelial permeability were validated by conjugation to sucrose octasulfate. Induction of neocapillaries adds pharmacokinetic complexity. Sustained local fibroblast growth factor delivery in vivo produced a burst of neovascularization in ischemic myocardium but was followed by drug washout and a 5-fold decrease in fibroblast growth factor penetration depth.

CONCLUSIONS

The very efficacy of proangiogenic compounds enhances their clearance and abrogates their pharmacological benefit. This self-limiting property of angiogenesis may explain the failures of promising proangiogenic therapies.

Rapid endothelial turnover in atherosclerosis-prone areas coincides with stem cell repair in apolipoprotein E-deficient mice

BACKGROUND

Recently, it has been shown that stem/progenitor cells may repair damaged/lost endothelial cells in vein grafts and wire-injured arteries. In the present study, we investigated endothelial cell turnover and regeneration in apolipoprotein E (apoE)(-/-)/transgenic mice carrying LacZ genes driven by an endothelial TIE2 promoter.

METHODS AND RESULTS

To assess cell proliferation on the surface of aortas in apoE(-/-) mice and wild-type controls, BrdU was injected into the tail vein and labeled on en face preparation. BrdU-positive cells on the aortas were observed occasionally in wild-type mice and frequently at sites prone to lesion development in apoE(-/-) mice (0.18+/-0.1% versus 1.12+/-0.2%; P<0.001). Endothelial integrity tests demonstrated that the areas with high rate of cell turnover displayed Evans blue leakage, low levels of VE-cadherin expression, and increased cell attachment, as evidenced by Evans blue dye injection, immunostaining, and scanning electron microscopy, respectively. Furthermore, immunostaining for CD34, Sca-1, Flk-1, and CD133 indicated that approximately 3% to 5% of total cells on the aorta were positive in apoE(-/-) mice. En face double labeling using Ki-67 and progenitor markers revealed that 30% to 50% of progenitor(+) cells expressed Ki-67, indicating a state of proliferation. To clarify the origin of endothelial progenitor cells participating in endothelial repair in apoE(-/-) mice, a chimeric mouse model was created by bone marrow transplantation between apoE(-/-) and LacZ(+/+)/apoE(-/-) mice. Ten months after bone marrow transplantation, approximately 3% to 4% of total cells in the lesion-prone areas were beta-gal positive in apoE(-/-) with apoE(-/-)/TIE2-LacZ bone marrow mice. When cells of aortas from chimeric mice were cultivated on Matrigel-coated plates, a capillary-like structure was found, which showed beta-gal/CD31 or beta-gal/von Willebrand factor double positivity. By a combined analysis of laser dissection microscopy and nest reverse transcription polymerase chain reaction, it was found that beta-gal(+) cells were mainly expressing CD31 and CD144.

CONCLUSIONS

Our findings provide the first quantitative data on endothelial turnover and repair by progenitor cells that are, at least in part, derived from bone marrow during development of atherosclerosis in apoE(-/-) mice.

Application of bFGF and BDNF to Improve Angiogenesis and Cardiac Function

BACKGROUND

Brain-derived neurotrophic factor (BDNF) is a survival factor for endothelial cells and expresses in the ischemic myocytes. The purpose of this study was to assess whether the simultaneous application of basic fibroblast growth factor (bFGF) and BDNF incorporating gelatin hydrogels improves angiogenesis and cardiac function in ischemic myocardium compared with bFGF applied alone.

MATERIALS AND METHODS

Direct intramyocardial injection of 100 microg of bFGF plus 25 microg of BDNF, 100 microg of bFGF, or saline were performed in canine infarct model. Colored microspheres were injected to assess the regional myocardial blood flow. Cardiac function was evaluated by cine magnetic resonance imaging (MRI). Immunohistochemical staining and enzyme linked immunosorbent assay (ELISA) were used to observe the localization and expression of bFGF and BDNF protein, and myocardial microvessel density was assessed by von Willebrand factor staining.

RESULTS

Left ventricular ejection fraction (LVEF) was higher in bFGF plus BDNF group than in saline or bFGF group. Blood flow of the peri-infarct region was increased by bFGF plus BDNF treatment. The distribution of bFGF and BDNF-positive cardiomyocytes was similar in three groups. The expression of bFGF and BDNF protein and microvessel density in bFGF plus BDNF group was higher than in the other two groups.

CONCLUSIONS

This study indicates that the sustained dual release of bFGF and BDNF incorporating gelatin hydrogels can improve angiogenesis and left ventricular function in the ischemic myocardium compared with bFGF applied alone. bFGF plus BDNF administration may be a promising therapeutic strategy for the treatment of ischemic myocardium.

Normalization of coronary blood flow in the infarct-related artery after intracoronary progenitor cell therapy: intracoronary Doppler substudy of the TOPCARE-AMI trial

BACKGROUND

Coronary microvascular dysfunction contributes to infarct extension and poor prognosis after an acute myocardial infarction (AMI). Recently, progenitor cell application has been demonstrated to improve neovascularization and myocardial function after experimental myocardial infarction. Therefore, we investigate coronary blood flow regulation in patients after AMI treated with intracoronary progenitor cell therapy.

METHODS AND RESULTS

In the TOPCARE-AMI trial, patients received either bone marrow-derived or circulating progenitor cells into the infarct-related artery 3-7 days after AMI. The present substudy investigates in 40 patients coronary blood flow regulation at the time of progenitor cell therapy and at 4-month follow-up by i.c. Doppler in the infarct artery as well as a reference vessel. At the initial measurement, coronary flow reserve (CFR) was reduced in the infarct artery compared to the reference vessel (median 2.5 vs. 3.4, p<0.001). At 4-month follow-up, intracoronary progenitor cell therapy was associated with a normalization of CFR in the infarct artery (median 3.9 vs. reference vessel 3.8, p=0.15). CFR also improved in the reference vessel, but mechanisms were different: reference vessel increase in CFR was secondary to an increased basal vascular resistance, probably due to reduced need for hypercontractility. In contrast, in the infarct artery, adenosine-induced minimal vascular resistance profoundly decreased, indicating an increased maximal coronary vascular conductance capacity. In addition, in a non-randomized matched control group (n=8), minimal vascular resistance in the infarct artery was significantly elevated compared to progenitor cell treated patients 4 months after AMI (p=0.012).

CONCLUSIONS

Intracoronary progenitor cell therapy after AMI is associated with complete restoration of coronary flow reserve due to a substantial improvement of maximal coronary vascular conductance capacity. The clinical importance of improved microcirculation by progenitor cell therapy in patients after AMI has to be established in further randomized trials.

FAK-dependent regulation of myofibroblast differentiation

Fibroblasts and myofibroblasts both participate in wound healing. Transforming growth factor beta (TGFbeta) induces fibroblasts to differentiate into myofibroblasts, whereas fibroblast growth factor and heparin (FGF/h) induce myofibroblasts to "de-differentiate" into fibroblasts. TGFbeta induces expression of smooth muscle alpha actin (SMalphaA) and incorporation into in stress fibers, a phenotype of differentiated myofibroblasts. Additionally, TGFbeta induces the expression of fibronectin and fibronectin integrins. Fibronectin-generated signals contribute to the TGFbeta-mediated myofibroblast differentiation. Because fibronectin signals are transmitted through focal adhesion kinase (FAK), it was predicted that FAK would be essential to TGFbeta-mediated myofibroblast differentiation. To determine whether the FAK signaling pathway is required for myofibroblast differentiation, we used two approaches to decrease FAK in mouse embryo fibroblasts (MEFs): 1) FAK +/+ MEFs, in which FAK protein expression was greatly decreased by short hairpin RNA (shRNA), and 2) FAK -/- MEFs, which lack FAK. In both cases, the majority of cells were myofibroblasts, expressing SMalphaA in stress fibers even after treatment with FGF/h. Furthermore, both the surface expression of FGFRs and FGF signaling were greatly reduced in FAK -/- [corrected]MEFs. We conclude that FAK does not contribute to TGFbeta-dependent myofibroblast differentiation. Instead, FAK was necessary for FGF/h signaling in down-regulating expression of SMalphaA, which is synonymous with myofibroblast differentiation. FAK activation could contribute to regulating myofibroblast differentiation, thereby ameliorating fibrosis.

Combination of enoxaparin and fibroblast growth factor-1 increases myocardial blood flow and capillary density after myocardial infarction in rabbits

OBJECTIVE

The effect of enoxaparin and fibroblast growth factor-1 (FGF-1) on post-infarction capillary density and regional myocardial blood flow (RMBF) was examined.

METHODS

New Zealand White rabbits received an intramyocardial injection of either physiological saline, FGF-1 + enoxaparin, FGF-1 or enoxaparin directly after ligation of the left anterior descending artery. RMBF and capillary density were investigated using fluorescent microspheres and histological examination.

RESULTS

One week after infarction a significant difference in the number of capillaries could be demonstrated within the FGF-1 + enoxaparin group (p < 0.001 versus the control group), the FGF-1 group (p < 0.01) and the enoxaparin group (p < 0.05). Treatment with FGF-1 + enoxaparin resulted in a significantly increased number of capillaries compared to treatment with FGF-1 (p < 0.05) and enoxaparin (p < 0.05) alone. Additionally, all groups treated with FGF-1 and/or enoxaparin showed a significant increase of microvessel density in the treated ischemic border zone compared to the non-treated ischemic border zone (p < 0.001 for FGF-1 + enoxaparin, p < 0.01 for FGF-1, p < 0.05 for enoxaparin). RMBF was significantly increased within the FGF-1 + enoxaparin group compared to the control group (p < 0.05). Moreover, perfusion rates within the FGF-1 + enoxaparin-treated area did not significantly differ from the pre-infarction values.

CONCLUSION

Treatment with either enoxaparin or FGF-1 or FGF-1 + enoxaparin resulted in increased microvessel growth. However, only the combination of enoxaparin with FGF-1 promotes capillary growth and RMBF. Thus, we conclude that enoxaparin enhances the angiogenic potential of intramyocardially injected FGF-1 in the acutely infarcted rabbit heart.

A percutaneous swine model of myocardial infarction

INTRODUCTION

The aim of this study was to develop a percutaneous, low risk, and reproducible technique of MI that simulates human disease.

METHODS

MI was induced in 44 swine (32.8+/-7.2 kg) by percutaneous embolization coil deployment in the left anterior descending coronary artery. Hemodynamic measurements, left heart catheterization, and echocardiography were performed pre, post, and 30 days after MI. 3D NOGA viability mapping was performed at baseline and 30 days. Excised hearts were examined histologically.

RESULTS

Pre-MI mortality was 6.8% and 24 h mortality was 13.6%. All pigs that survived 24 h after MI remained alive at 30 days. The mean left ventricular ejection fraction decreased from 58.4% to 42.1% (p<0.001) at 30 days. The average thrombolysis in myocardial infarction score was 3, 0, and 1.5 at baseline, post-MI, and 30 days, respectively. At 30 days, the end diastolic diameter, end diastolic volume, end systolic volume, and wall motion index increased from 3.76 to 3.89 cm, 32.5 to 50.0 ml, 14.9 to 27.0 ml, and 1.01 to 1.38, respectively (all p<0.05), while the ejection fraction decreased from 56.5% to 49.4% (p<0.01). Additionally, at 30 days, statistically significant reductions in both unipolar and bipolar voltage in the mid and apical regions of the left ventricle were observed. Postmortem pathology showed a transmural scar in the apical anteroseptal regions with fibrosis in the MI region, which accounted for 14.8% and 14.2% of the total left and right ventricular myocardial area and volume, respectively.

DISCUSSION

This model of MI is reliable, reproducible, has a pathophysiology similar to humans, and a lower mortality and ventricular fibrillation rates compared to other models. This model may be used to evaluate the effects of pharmacologics, gene therapy, and stem cell transplantation for the treatment of cardiovascular disease as well as studying mechanisms of cardiac remodeling.

Regulation of reactive oxygen species-induced endothelial cell-cell and cell-matrix contacts by focal adhesion kinase and adherens junction proteins

Oxidants, generated by activated neutrophils, have been implicated in the pathophysiology of vascular disorders and lung injury; however, mechanisms of oxidant-mediated endothelial barrier dysfunction are unclear. Here, we have investigated the role of focal adhesion kinase (FAK) in regulating hydrogen peroxide (H2O2)-mediated tyrosine phosphorylation of intercellular adhesion proteins and barrier function in endothelium. Treatment of bovine pulmonary artery endothelial cells (BPAECs) with H2O2increased tyrosine phosphorylation of FAK, paxillin, β-catenin, and vascular endothelial (VE)-cadherin and decreased transendothelial electrical resistance (TER), an index of cell-cell adhesion and/or cell-matrix adhesion. To study the role of FAK in H2O2-induced TER changes, BPAECs were transfected with vector or FAK wild-type or FAK-related non-kinase (FRNK) plasmids. Overexpression of FRNK reduced FAK expression and attenuated H2O2-mediated tyrosine phosphorylation of FAK, paxillin, β-catenin, and VE-cadherin and cell-cell adhesion. Additionally, FRNK prevented H2O2-induced distribution of FAK, paxillin, β-catenin, or VE-cadherin toward focal adhesions and cell-cell adhesions but not actin stress fiber formation. These results suggest that activation of FAK by H2O2is an important event in oxidant-mediated VE barrier function regulated by cell-cell and cell-matrix contacts.

Effects of Ebola virus glycoproteins on endothelial cell activation and barrier function

Ebola virus causes severe hemorrhagic fever with high mortality rates in humans and nonhuman primates. Vascular instability and dysregulation are disease-decisive symptoms during severe infection. While the transmembrane glycoprotein GP(1,2) has been shown to cause endothelial cell destruction, the role of the soluble glycoproteins in pathogenesis is largely unknown; however, they are hypothesized to be of biological relevance in terms of target cell activation and/or increase of endothelial permeability. Here we show that virus-like particles (VLPs) consisting of the Ebola virus matrix protein VP40 and GP(1,2) were able to activate endothelial cells and induce a decrease in barrier function as determined by impedance spectroscopy and hydraulic conductivity measurements. In contrast, the soluble glycoproteins sGP and delta-peptide did not activate endothelial cells or change the endothelial barrier function. The VLP-induced decrease in barrier function was further enhanced by the cytokine tumor necrosis factor alpha (TNF-alpha), which is known to induce a long-lasting decrease in endothelial cell barrier function and is hypothesized to play a key role in Ebola virus pathogenesis. Surprisingly, sGP, but not delta-peptide, induced a recovery of endothelial barrier function following treatment with TNF-alpha. Our results demonstrate that Ebola virus GP(1,2) in its particle-associated form mediates endothelial cell activation and a decrease in endothelial cell barrier function. Furthermore, sGP, the major soluble glycoprotein of Ebola virus, seems to possess an anti-inflammatory role by protecting the endothelial cell barrier function.

Beyond angiogenesis: the cardioprotective potential of fibroblast growth factor-2

In the field of cardiovascular research, a number of independent approaches have been explored to protect the heart from acute and chronic ischemic damage. Fibroblast growth factor-2 (FGF-2) recently has received considerable attention with respect to its angiogenic potential. While therapeutic angiogenesis may serve to salvage chronically ischemic myocardium, more acute treatments are in demand to increase cardiac resistance to injury (preconditioning) and to guard against secondary injury after an acute ischemic insult. Here, we look beyond the angiogenic potential of FGF-2 and examine its acute cardioprotective activity as demonstrated under experimental conditions, both as an agent of a preconditioning-like response and for secondary injury prevention at the time of reperfusion. Factors to consider in moving to the clinical setting will be discussed, including issues of dosage, treatment duration, and routes of administration. Finally, issues of safety and clinical trial design will be considered. The prospect of such a multipotent growth factor having clinical usefulness opens the door to effective treatment of both acute and chronic ischemic heart disease, something well worth the attention of the cardiovascular community.

Biopolymeric delivery matrices for angiogenic growth factors

The development of new therapeutic approaches that aim to help the body exert its natural mechanisms for vascularized tissue growth (therapeutic angiogenesis) has become one of the most active areas of tissue engineering. Through basic research, several growth factor families and cytokines that are capable to induce physiological blood vessel formation have been identified. Indeed, preclinical and clinical investigations have indicated that therapeutic administration of angiogenic factors, such as the prototypic vascular endothelial growth factor (VEGF) or basic fibroblast growth factor (bFGF), to sites of ischemia in the heart or the limb can improve regional blood flow. For new and lasting tissue vascularization, prolonged tissue exposure to these factors could be critical. Furthermore, as shown for VEGF, dosage must be tightly controlled, as excess amounts of VEGF can cause severe vascular leakage and hypotension. This review emphasizes natural and synthetic polymer matrices with respect to their development as vehicles for local and controlled delivery of angiogenic proteins, such as VEGF and bFGF, and their clinical applicability. In the dawn of experimental vascular engineering, new biomaterial schemes for clinical growth factor administration that take better account of biological principles of angiogenic growth factor function and the cell biological basis necessary to produce functional vasculature are evolving. Alongside their base function as protective embedment for angiogenic growth factors, these new classes of bioactive polymers are engineered with additional functionalities that better preserve growth factor activity and more closely mimic the in vivo release mechanisms and profiles of angiogenic growth factors from the extracellular matrix (ECM). Consequently, the preparation of both natural or completely synthetic materials with biological characteristics of the ECM has become central to many tissue engineering approaches that aim to deliver growth factors in a therapeutically efficient mode. Another promising venue to improve angiogenic performance is presented by biomaterials that allow sequential delivery of growth factors with complementary roles in blood vessel initiation and stabilization.

Potential role for antiangiogenic proteins in the myocardial infarction repair process

OBJECTIVE

Although angiogenic proteins have been identified as positive modulators of myocardial revascularization following acute myocardial infarction, little if anything is known regarding the role that antiangiogenic proteins have in myocardial revascularization. We explored the temporospatial distribution of endothelial-monocyte activating polypeptide (EMAP) II to determine whether antiangiogenic proteins have a role in the repair of myocardial tissue following infarction.

METHODS

A rat model of myocardial infarction was utilized to examine EMAP II distribution (in situ hybridization) and protein expression (Western analysis) over a 6-week period.

RESULTS

At baseline, EMAP II protein and mRNA are minimally expressed with transcription products localizing predominately to the perivascular stroma region in the normal rat myocardium. Six hours following myocardial infarction, EMAP II changes its distribution from the perivascular stroma to an invading inflammatory cell population. This is associated with a 2-fold (P < 0.0009) increase in EMAP II protein and its transcription primarily localized to the infarct region. EMAP II protein expression remains elevated throughout the weeks following the infarction with transcription limited to the infarct region and a notable decrease in EMAP II transcription products noted in the viable vasculature surrounding the infarct zone. Six weeks following myocardial infarction, EMAP II protein is elevated above control, changes its location of transcription from the inflammatory cell population to that of the fibroblasts located in the relative avascular scar tissue, and has resumed its perivascular stromal distribution in the viable periinfarct tissue.

CONCLUSIONS

Thus, the temporospatial distribution of this antiangiogenic protein suggests that negative vascular modulators may have a function in the revascularization process following acute myocardial infarction.

Insulin-dependent diabetes impairs the inflammatory response and delays angiogenesis following Achilles tendon injury

Although impaired wound healing associated with type 1 diabetes mellitus has been well studied in skin tissue, the influence of this metabolic disorder on tendon healing and recovery has not been extensively investigated. Because tendons are known to have limited repair potential, we studied the tendon-healing process by using a diabetic rat tendonitis model. We tested the hypothesis that diabetes influences the inflammatory response, cell proliferation, and angiogenesis in injured Achilles tendons. Diabetes was induced by injecting streptozotocin at 45 mg/kg body wt. Non-diabetic rats as well as diabetic and insulin-treated diabetic animals were then injected with collagenase. The accumulation of inflammatory cells was quantified in transversal sections of Achilles tendon by using immunohistochemical staining at days 0, 1, 3, 7, 14, and 28 posttrauma. The number of proliferative cells and the extent of neovascularization was also quantified in the paratenon and the core of the tendon at days 0, 3, 7, 14, and 28 posttrauma. Relative to nondiabetic and insulin-treated diabetic animals, the numbers of accumulated neutrophils and ED1(+) and ED2(+) macrophages in diabetic rats decreased by 46, 43, and 52%, respectively, in the first 3 days after injury compared with levels in nondiabetic and insulin-treated diabetic animals. The density of newly formed blood vessels decreased by 35 and 29% in the paratenon and the core of tendon, respectively, at days 3 and 7 after injury. Lastly, the concentration of proliferative cells decreased by 34% in the paratenon at day 7 posttrauma in injured tendons from diabetic rats relative to nondiabetic rats. These results indicate that alterations in inflammatory, angiogenic, and proliferative processes occurred in the diabetic state that might eventually perturb tendon healing and remodeling.

A pig model of chronic heart failure by intracoronary embolization with gelatin sponge

BACKGROUND

We produced a large-animal model of left ventricular (LV) failure induced by transcatheter embolization of the left coronary artery using a gelatin sponge.

METHODS

Fourteen male pigs underwent transcatheter embolization of the left anterior descending artery (LAD) using gelatin sponge to produce anteroapical myocardial infarction. Coronary angiography was performed 1 week after the coronary embolization. The animals were followed up with echocardiography and LV pressure-volume study for the subsequent 8 weeks, and the data were compared with those of the control group (n = 13).

RESULTS

The procedure mortality was 2 of 14 (14%). Coronary angiography revealed the occluded LAD was recanalized with poor run-off. The LV end-diastolic dimension progressively increased (control versus myocardial infarction: 39 +/- 2 mm versus 49 +/- 4 mm, p < 0.001 at week 4; and 40 +/- 2 mm versus 57 +/- 6 mm, p < 0.001 at week 8). Fractional area change decreased over 8 weeks (77% +/- 10% versus 43% +/- 6%, p < 0.001 at week 4; and 77% +/- 10% versus 40% +/- 8%, p < 0.001 at week 8). End-systolic elastance progressively decreased over 8 weeks (3.04 +/- 0.73 mm Hg/mL versus 1.54 +/- 0.51 mm Hg/mL, p < 0.0001 at week 4; and 2.88 +/- 0.44 mm Hg/mL versus 1.05 +/- 0.21 mm Hg/mL, p < 0.001 at week 8). The plasma levels of brain natriuretic peptide were significantly higher in the study group (543 +/- 131 pg/mL versus 1,321 +/- 364 pg/mL, p < 0.001 at week 4; and 610 +/- 152 pg/mL versus 1,523 +/- 232 pg/mL, p < 0.001 at week 8).

CONCLUSIONS

This pig model of chronic heart failure is reliable, reproducible, and amenable to investigate other surgical procedures.

Effect of fucoidan on fibroblast growth factor-2-induced angiogenesis in vitro

Fucoidans are sulfated polysaccharides extracted from brown marine algae. A purified fucoidan fraction exhibits the same venous antithrombotic activity as heparin in rabbits, but with a lower anticoagulant effect. Because of its heparin-like structure, we postulated that fucoidan might modulate heparin-binding angiogenic growth factor activity. We thus studied its effect, at antithrombotic concentrations, on fibroblast growth factor (FGF)-2-induced proliferation and differentiation of human umbilical vein endothelial cells. The fucoidan effect on endothelial cell differentiation was evaluated by studying the expression of surface proteins (i.e. integrin, adhesion molecule) known to be modulated by FGF-2 and involved in angiogenesis, and by quantifying closed areas delimited by vascular tubes formed on reconstituted basement membrane. Fucoidan had no modulatory effect on the mitogenic activity of FGF-2, but significantly increased tubular structure density induced by FGF-2. Fucoidan alone increased alpha(6) integrin subunit expression with only partially organized tubular structure. In the presence of FGF-2, fucoidan enhanced alpha(6), beta(1) and PECAM-1 and inhibited alpha(v)beta(3) integrin expression. Heparin had no effect in these systems. The most striking effect of fucoidan was observed on alpha(6) expression and tube formation was abolished by monoclonal anti-alpha(6) antibodies. Fucoidan plus FGF-2 effect on alpha(6) expression was markedly decreased by monoclonal anti-FGF-2 antibodies, indicating that fucoidan acts mainly via FGF-2. These results show that, at antithrombotic concentrations, contrary to heparin, fucoidan can enhance vascular tube formation induced by FGF-2 with a modulation of the expression of surface proteins (mainly alpha(6)) involved in angiogenesis.

Adenosine therapy: a new approach to chronic heart failure

Both the prevention and attenuation of chronic heart failure (CHF) are important issues for cardiologists. There are three different strategies to prevent patients from deleterious sequels. The first strategy is to remove the causes of CHF if possible; the second is to attenuate the events that may lead to CHF, such as myocardial ischaemia and reperfusion injury, cardiomyopathy and myocarditis, cardiac hypertrophy and ventricular remodelling; the third is to prevent or attenuate the progression of CHF. Adenosine has a number of actions which merit it as a possible cardioprotective and therapeutic agent for CHF. Firstly, adenosine induces collateral circulation via inducing growth factors and triggering ischaemic preconditioning, both of which induce ischaemic tolerance in advance. Adenosine is also known to reduce the release of noradrenaline, production of endothelin and attenuate the activation of renin-angiotensin system all of which are believed to cause cardiac hypertrophy and remodelling. Secondly, exogenous adenosine is known to reduce the severity of ischaemia and reperfusion injury. Thirdly, adenosine is reported to counteract neurohumoral factors, i.e., cytokine systems, known to be related to the pathophysiology of CHF. Recently, we revealed that adenosine metabolism is changed in patients with CHF and increases in adenosine levels may aid to reduce the severity of CHF. Thus, there are many potential mechanisms for cardioprotection attributable to adenosine and we postulate the use of adenosine therapy will be beneficial in patients with CHF.

Expression of perlecan proteoglycan in the infarct zone of mouse myocardial infarction

Perlecan, a basal lamina proteoglycan, has been shown to interact with other extracellular matrix (ECM) components, especially type IV collagen, and is thus involved in ECM formation. Perlecan has also been postulated to promote growth factor-receptor interactions, including the binding of basic fibroblast growth factor (bFGF) to its receptor, and to enhance mitogenesis and angiogenesis. To test our hypothesis that perlecan is increased in the myocardial infarct zone, we examined perlecan expression after experimentally induced myocardial infarction in BALb/c mice by the methods of in situ hybridization, Northern blotting, and immunohistochemistry. In situ hybridization revealed mRNA signals for perlecan in the infarct marginal zone on day 2 and in the infarct interior zone around infarct granulation tissue on day 7. On day 14 the signals were observed at the center point of the infarct. The signals were detected in spindle-shaped mesenchymal cells (fibroblasts and myofibroblasts). Some surviving myocytes in the infarct marginal zone also showed positive signals. The sequential changes in the perlecan mRNA signal distribution paralleled those for type IV collagen mRNA. Northern blotting demonstrated increased expression of perlecan consistent with the observations of in situ hybridization. Immunopositive staining for perlecan was observed in the infarct zone around granulation tissue on day 7 and in the entire infarct zone on days 14-28. Immunostaining for bFGF was localized surrounding the infarct granulation tissue on day 7 and overlapped with perlecan immunostaining. The present results demonstrated the expression of perlecan by spindle-shaped mesenchymal cells (fibroblasts and myofibroblasts) and some surviving myocytes in the myocardial infarct, indicating the contribution of perlecan to the pathological course of myocardial infarction.

It is time to ask what adenosine can do for cardioprotection

Prevention and attenuation of ischemia and reperfusion injury in patients with acute coronary syndrome are critically important for cardiologists. To save these patients from deleterious ischemic insults, there are three different strategies. The first strategy is to increase ischemic tolerance before the onset of myocardial ischemia; the second is to attenuate the ischemia and reperfusion injury when an irreversible process of myocardial cellular injury occurs; the third is to treat the ischemic chronic heart failure that is caused by acute myocardial infarction. Adenosine, which is known to be cardioprotective against ischemia and reperfusion injury, may merit being used for these three cardioprotection strategies. First of all, adenosine induces collateral circulation via induction of growth factors, and triggers ischemic preconditioning, both of which induce ischemic tolerance in advance. Secondly, endogenous adenosine may mediate the infarct size-limiting effect of ischemic preconditioning, and exogenous adenosine is known to attenuate ischemia and reperfusion injury. Thirdly, we also revealed that adenosine metabolism is changed in patients with chronic heart failure, and increases in adenosine levels may attenuate the severity of ischemic heart failure. Therefore, adenosine therapy may improve the pathophysiology of ischemic chronic heart failure. Taking these factors together, we hereby propose potential tools for cardioprotection attributable to adenosine in ischemic hearts, and we postulate the use of adenosine therapy before, during, and after the onset of acute myocardial infarction.

Combination TMR and gene therapy

Transmyocardial laser revascularization is a promising surgical technique that relieves angina and improves subendocardial perfusion in patients with chronic ischemic heart disease refractory to medical management and not amenable to conventional revascularization techniques. We detail our laboratory experience at the Brigham and Women's Hospital with transmyocardial laser revascularization and discuss the potential clinical applications of this work.