Nonendothelial mesenchymal cell-derived MCP-1 is required for FGF-2-mediated therapeutic neovascularization: critical role of the inflammatory/arteriogenic pathway

Regenerative Effect of Umbilical Cord-Derived Mesenchymal Stromal Cells in a Rat Model of Established Limb Ischemia

BACKGROUND

Although regenerative cell therapy is expected to be an alternative treatment for peripheral artery disease (PAD), many regenerative cell therapies have failed to show sufficient efficacy in clinical trials. Most preclinical studies have used acute ischemia models, despite PAD being a chronic disease. In addition, aging and atherosclerosis decrease the quality of a patient's stem cells. Therefore, using a non-acute ischemic preclinical model and stem cells with high regenerative potency are important for the development of effective regenerative therapy. In this study, we assessed the tissue regenerative potential of umbilical cord-derived mesenchymal stromal cells (UCMSCs), which could potentially be an ideal cell source, in a rat model of established ischemia.

METHODS AND RESULTS

The regenerative capacity of UCMSCs was analyzed in terms of angiogenesis and muscle regeneration. In vitro analysis showed that UCMSCs secrete high amounts of cytokines associated with angiogenesis and muscle regeneration. In vivo experiments in a rat non-acute ischemia model showed significant improvement in blood perfusion after intravenous injection of UCMSCs compared with injection of culture medium or saline. Histological analysis revealed UCMSCs injection enhanced angiogenesis, with an increased number of von Willebrand factor-positive microcapillaries, and improved muscle regeneration.

CONCLUSIONS

These results suggest that intravenous administration of UCMSCs may be useful for treating patients with PAD.

Design of a dual-function agent by fusing a designed anti-VEGF-A binder and CPG-2 enzyme

Anti-VEGF therapies are common for the treatment of cancer. Carboxypeptidase G (CPG-2) enzyme is a zinc-dependent metalloenzyme that metabolizes non-toxic synthetic 'benzoic mustard prodrugs' to cytotoxic moieties in tumor cells. In this study, we designed a dual-activity agent by combining a designed anti-VEGF- and CPG-2 enzyme to convert methotrexate (MTX). VEGF-A was docked against a set of scaffolds, and suitable inverse rotamers were made. Rosetta design was used for the interface design. The top 1200 binders were chosen by flow cytometry and displayed in yeast. The activity of CPG-2 enzyme was analyzed at different temperature conditions and in the presence of the substrate, MTX. Optimal binders were selected and protein was eluted using immobilized metal affinity chromatography and size-exclusion chromatography. Both, native PAGE and on-yeast flow cytometry confirmed the binding of the binder to VEGF-A. The activity of truncated enzymes was slightly lower than that of full-length enzymes linked to VEGF-A. The method should be generally useful as a dual-activity agent for targeting VEGF-A and combination therapy with the enzyme CPG-2 for metabolizing non-toxic prodrugs to cytotoxic moieties.Communicated by Ramaswamy H. Sarma.

Overcoming ischemia in the diabetic foot: Minimally invasive treatment options

As the global burden of diabetes is rapidly increasing, the incidence of diabetic foot ulcers is continuously increasing as the mean age of the world population increases and the obesity epidemic advances. A significant percentage of diabetic foot ulcers are caused by mixed micro and macro-vascular dysfunction leading to impaired perfusion of foot tissue. Left untreated, chronic limb-threatening ischemia has a poor prognosis and is correlated with limb loss and increased mortality; prompt treatment is required. In this review, the diagnostic challenges in diabetic foot disease are discussed and available data on minimally invasive treatment options such as endovascular revascularization, stem cells, and gene therapy are examined.

VEGF-A Is Associated With the Degree of TILs and PD-L1 Expression in Primary Breast Cancer

BACKGROUND/AIM

Vascular endothelial growth factor-A (VEGF-A), an important angiogenic factor, has been reported to effect cancer growth and development. Recent reports indicated that anti-VEGF therapy has an important effect of enhancing anti-tumor immunity in various cancers. In the current study, we investigated the relationship between VEGF-A expression and immunological factors, including programmed cell death ligand 1 (PD-L1) and the degrees of stromal tumor-infiltrating lymphocytes (TILs) in breast cancer.

PATIENTS AND METHODS

This study enrolled 97 cases with invasive breast cancer who had undergone surgery without preoperative therapy. The grades of stromal-TILs were evaluated using the criteria of the International Working Group for TILs in breast cancer: low, intermediate, and high. VEGF-A and PD-L1 positivity were evaluated by immunohistochemistry. The relationship between VEGF-A expression and the expression of PD-L1 and TILs was investigated.

RESULTS

Among the 97 cases, 37 (38.1%) had positive VEGF-A expression in the breast tumor. We divided the cases in two groups based on the VEGF-A expression levels. The analysis revealed that PD-L1 positivity was significantly associated with VEGF-A expression in the breast tumor (29.7% vs. 10.0%, p=0.014). Among the cases with positive PD-L1, 36.7% of VEGF-positive cases and none of VEGF-negative cases had low TILs in the breast tumor.

CONCLUSION

VEGF-A expression in breast cancer may reflect PD-L1 expression in the tumor. VEGF-A may act as a negative biomarker of TILs in PD-L1-positive breast cancer. Our results suggest that VEGF-A may be predictive of immunological features and may serve as a useful biomarker for immuno-targeting therapy in patients with breast cancer.

Adipose-Derived Stromal Cells Seeded in Pullulan-Collagen Hydrogels Improve Healing in Murine Burns

Burn scars and scar contractures cause significant morbidity for patients. Recently, cell-based therapies have been proposed as an option for improving healing and reducing scarring after burn injury, through their known proangiogenic and immunomodulatory paracrine effects. Our laboratory has developed a pullulan-collagen hydrogel that, when seeded with mesenchymal stem cells (MSCs), improves cell viability and augments their proangiogenic capacity in vivo. Concurrently, recent research suggests that prospective isolation of cell subpopulations with desirable transcriptional profiles can be used to further improve cell-based therapies. In this study, we examined whether adipose-derived stem cell (ASC)-seeded hydrogels could improve wound healing following thermal injury using a murine contact burn model. Partial thickness contact burns were created on the dorsum of mice. On days 5 and 10 following injury, burns were debrided and received either ASC hydrogel, ASC injection alone, hydrogel alone, or no treatment. On days 10 and 25, burns were harvested for histologic and molecular analysis. This experiment was repeated using CD26⁺/CD55⁺ FACS-enriched ASCs to further evaluate the regenerative potential of ASCs in wound healing. ASC hydrogel-treated burns demonstrated accelerated time to reepithelialization, greater vascularity, and increased expression of the proangiogenic genes MCP-1, VEGF, and SDF-1 at both the mRNA and protein level. Expression of the profibrotic gene Timp1 and proinflammatory gene Tnfa was downregulated in ASC hydrogel-treated burns. ASC hydrogel-treated burns exhibited reduced scar area compared to hydrogel-treated and control wounds, with equivalent scar density. CD26⁺/CD55⁺ ASC hydrogel treatment resulted in accelerated healing, increased dermal appendage count, and improved scar quality with a more reticular collagen pattern. Here we find that ASC hydrogel therapy is effective for treating burns, with demonstrated proangiogenic, fibromodulatory, and immunomodulatory effects. Enrichment for CD26⁺/CD55⁺ ASCs has additive benefits for tissue architecture and collagen remodeling postburn injury. Research is ongoing to further facilitate clinical translation of this promising therapeutic approach. Impact statement Burns remain a significant public health burden. Stem cell therapy has gained attention as a promising approach for treating burns. We have developed a pullulan-collagen biomimetic hydrogel scaffold that can be seeded with adipose-derived stem cells (ASCs). We assessed the delivery and activity of our scaffold in a murine contact burn model. Our results suggest that localized delivery of ASC hydrogel treatment is a promising approach for the treatment of burn wounds, with the potential for rapid clinical translation. We believe our work will have broad implications for both hydrogel therapeutics and regenerative medicine and will be of interest to the general scientific community.

Visfatin: An emerging adipocytokine bridging the gap in the evolution of cardiovascular diseases

Visfatin/nicotinamide phosphoribosyltransferase (NAMPT) is an adipokine expressed predominately in visceral fat tissues. High circulating levels of visfatin/NAMPT have been implicated in vascular remodeling, vascular inflammation, and atherosclerosis, all of which pose increased risks of cardiovascular events. In this context, increased levels of visfatin have been correlated with several upregulated pro-inflammatory mediators, such as IL-1, IL-1Ra, IL-6, IL-8, and TNF-α. Furthermore, visfatin is associated with leukocyte recruitment by endothelial cells and the production of adhesion molecules such as vascular cell adhesion molecule 1, intercellular cell adhesion molecule 1, and E-selectin, which are well known to mediate the progression of atherosclerosis. Moreover, diverse angiogenic factors have been found to mediate visfatin-induced angiogenesis. These include matrix metalloproteinases, vascular endothelial growth factor, monocyte chemoattractant protein 1, and fibroblast growth factor 2. This review aims to provide a comprehensive overview of the pro-inflammatory and angiogenic actions of visfatin, with a focus on the pertinent signaling pathways whose dysregulation contributes to the pathogenesis of atherosclerosis. Most importantly, some hypotheses regarding the integration of the aforementioned factors with the plausible atherogenic effect of visfatin are put forth for consideration in future studies. The pharmacotherapeutic potential of modulating visfatin's roles could be important in the management of cardiovascular disease, which continues to be the leading cause of death worldwide.

Fibroblast growth factor 2 exacerbates inflammation in adipocytes through NLRP3 inflammasome activation

Chronic inflammation in adipose tissue is the hallmark of obesity and a major risk factor for the development of obesity-induced insulin resistance. NLRP3 inflammasome regulates the maturation and secretion of pro-inflammatory cytokines, such as IL-1β and IL-18, and was recently discovered to be involved in obesity-related metabolic diseases. Fibroblast growth factors (FGFs) such as FGF1, FGF10, and FGF21 are adipokines that regulate adipocyte development and metabolism, but reports on the effect of other FGFs on adipocytes are lacking. In the present study, the novel role of FGF2 in NLRP3 inflammasome activation was elucidated. Our results showed that FGF2 levels were increased during adipocyte differentiation and in the adipose tissue of high-fat diet (HFD)-induced obese mice. Recombinant FGF2 treatment upregulated inflammasome markers such as NLRP3, which was further exaggerated by TNF-ɑ treatment. Interestingly, β-Klotho, a co-receptor of FGF21, was significantly decreased by FGF2 treatment. Results from mice confirmed the positive correlation between FGF2 and NLRP3 expression in epididymal and subcutaneous adipose tissue, while exercise training effectively reversed HFD-induced NLRP3 expression as well as FGF2 levels in both adipose depots. Our results suggest that FGF2 is an adipokine that may exacerbate the inflammatory response in adipocytes through NLRP3 inflammasome activation.

Limb functional recovery is impaired in fibroblast growth factor-2 (FGF2) deficient mice despite chronic ischaemia-induced vascular growth

FGF2 is a potent stimulator of vascular growth; however, even with a deficiency of FGF2 (Fgf2-/-), developmental vessel growth or ischaemia-induced revascularization still transpires. It remains to be elucidated as to what function, if any, FGF2 has during ischaemic injury. Wildtype (WT) or Fgf2-/- mice were subjected to hindlimb ischaemia for up to 42 days. Limb function, vascular growth, inflammatory- and angiogenesis-related proteins, and inflammatory cell infiltration were assessed in sham and ischaemic limbs at various timepoints. Recovery of ischaemic limb function was delayed in Fgf2-/- mice. Yet, vascular growth response to ischaemia was similar between WT and Fgf2-/- hindlimbs. Several angiogenesis- and inflammatory-related proteins (MCP-1, CXCL16, MMPs and PAI-1) were increased in Fgf2-/- ischaemic muscle. Neutrophil or monocyte recruitment/infiltration was elevated in Fgf2-/- ischaemic muscle. In summary, our study indicates that loss of FGF2 induces a pro-inflammatory microenvironment in skeletal muscle which exacerbates ischaemic injury and delays functional limb use.

Therapeutic Angiogenesis

Myocardial ischemia and peripheral vascular disease persist as significant clinical problems despite improved medical, surgical, and endovascular therapies. Advances in our understanding of the biological mechanisms that govern capillary neovascularization and collateral artery growth have enabled molecular therapies for revascularizing ischemic tissues. Generally known as therapeutic angiogenesis, this review summarizes the essential pre-clinical research and the major clinical trials of molecular therapies for ischemic disease. Early clinical experience has established the proof of principle, however, inconsistent and modest improvements in clinical outcomes have exposed the complexity of neovascularization and problems with transitioning basic science to clinical applicability.

Tissue Engineering of the Microvasculature

The ability to generate new microvessels in desired numbers and at desired locations has been a long-sought goal in vascular medicine, engineering, and biology. Historically, the need to revascularize ischemic tissues nonsurgically (so-called therapeutic vascularization) served as the main driving force for the development of new methods of vascular growth. More recently, vascularization of engineered tissues and the generation of vascularized microphysiological systems have provided additional targets for these methods, and have required adaptation of therapeutic vascularization to biomaterial scaffolds and to microscale devices. Three complementary strategies have been investigated to engineer microvasculature: angiogenesis (the sprouting of existing vessels), vasculogenesis (the coalescence of adult or progenitor cells into vessels), and microfluidics (the vascularization of scaffolds that possess the open geometry of microvascular networks). Over the past several decades, vascularization techniques have grown tremendously in sophistication, from the crude implantation of arteries into myocardial tunnels by Vineberg in the 1940s, to the current use of micropatterning techniques to control the exact shape and placement of vessels within a scaffold. This review provides a broad historical view of methods to engineer the microvasculature, and offers a common framework for organizing and analyzing the numerous studies in this area of tissue engineering and regenerative medicine. © 2019 American Physiological Society. Compr Physiol 9:1155-1212, 2019.

VEGF-A/VEGFR-2 and FGF-2/FGFR-1 but not PDGF-BB/PDGFR-β play important roles in promoting immature and inflammatory intraplaque angiogenesis

Various angiogenic factors have been shown to play important roles in intraplaque angiogenesis, while little is known about the dynamic expression change and interplay between various angiogenic factors and intraplaque angiogenesis under high cholesterol conditions. New Zealand rabbits underwent balloon injury of the abdominal artery and then were assigned to a control group (n = 15, normal chow) or high cholesterol group (n = 25, 1% high cholesterol diet). At weeks 4, 6, 8, 10, and 12 after acclimation, rabbits (high cholesterol group, n = 5; control group, n = 3) were euthanized. No lesions were observed in the control group. From week 4 to week 12, the expression of vascular endothelial growth factor A (VEGF-A), VEGF receptor 2 (VEGFR-2), fibroblast growth factor 2 (FGF-2), FGF receptor 1 (FGFR-1), platelet-derived growth factor-BB (PDGF-BB), and tumor necrosis factor alpha (TNF-α), the vulnerability index (VI) and the microvessel density (MVD) were significantly elevated in the high cholesterol group; however, PDGF receptor β (PDGFR-β) expression showed little change. Analysis by double-label immunofluorescence (CD31 and Ng2) and FITC-dextran indicated that the neovessels within the plaque were leaky due to a lack of pericytes. As indicated by Pearson’s correlation analysis, there was a highly positive correlation between the VI, MVD, macrophage content, and TNF-α level, and the levels of VEGF-A/VEGFR-2 and FGF-2/FGFR-1. However, no correlations were observed between PDGFR-β levels and the VI or MVD. High expression of VEGF-A/VEGFR-2 and FGF-2/FGFR-1 but not of PDGF-BB/PDGFR-β may contribute to immature and inflammatory intraplaque angiogenesis and plaque instability in a rabbit model of atherosclerosis.

Induction of extracranial arteriogenesis by an arteriovenous fistula in a pig model

BACKGROUND AND AIMS

Arteriogenesis, the positive outward remodeling and growth of pre-existent collateral vessels, holds potential as a novel treatment for ischemic vascular disease. An extracranial arteriogenesis model in a pig will allow us to study molecular changes in a complex arteriolar network in a more clinically relevant large-animal model. To increase fluid shear stress in the brain, an experimental carotid arteriovenous fistula (AVF model) in minipigs was established, providing high flow through the extracranial rete mirabile. The aim of the study was to examine whether creation of a carotid AVF can induce extracranial arteriogenesis in the pig.

METHODS

Angiography was performed to demonstrate blood flow diversion. Animals were sacrificed after 0, 3 and 14 days post-surgery and both retia mirabilia were removed. Immunohistochemical analysis was performed to analyze cell proliferation and accumulation of mononuclear cells in the vessel wall.

RESULTS

After 3 days of high-flow conditions, increases in vascular cell proliferation (approximately 1.5-fold; p = 0.143) and monocyte invasion (approximately 6-fold; p = 0.057) were observed when compared to animals sacrificed immediately after AVF formation. Quantitative PCR (RT-qPCR) analysis from rete mirabile tissue samples 3 days post-surgery revealed that monocyte chemoattractant protein (MCP)-1 and tissue inhibitor of metalloproteinases (TIMP)-1 were highly upregulated. Expression of the pro-arteriogenic marker, CD44, reached maximum expression level 14 days post-surgery.

CONCLUSIONS

In response to high levels of shear stress produced in the pig AVF model, the onset of the arteriogenic process can be induced. This was demonstrated by enhanced cell proliferation, monocyte invasion and vascular remodeling.

Novel molecular targets for coronary angiogenesis and ischemic heart disease

Coronary artery disease (CAD) is the number one cause of death among men and women in the USA. Genetic predisposition and environmental factors lead to the development of atherosclerotic plaques in the vessel walls of the coronary arteries, resulting in decreased myocardial perfusion. Treatment includes a combination of revascularization procedures and medical therapy. Because of the high surgical risk of many of the patients undergoing revascularization procedures, medical therapies to reduce ischemic disease are an area of active research. Small molecule, cytokine, endothelial progenitor cell, stem cell, gene, and mechanical therapies show promise in increasing the collateral growth of blood vessels, thereby reducing myocardial ischemia.

Delivering therapeutics in peripheral artery disease: challenges and future perspectives

Targeted and sustained delivery of biologicals to improve neovascularization has been focused on stimulation angiogenesis. The formation of collaterals however is hemodynamically much more efficient, but as a target of therapy has been under-utilized. Although there is good understanding of the molecular processes involving collateral formation and there are interesting drugable candidates, the need for targeting and sustained delivery is still an obstacle towards safe and effective treatment. Molecular targeting with nanoparticles of liposomes is promising and so are peri-vascularly delivered polymer-based protein reservoirs. These developments will lead to future arteriogenesis strategies that are adjunct to current revascularization.

Nanoparticle drug delivery systems and their use in cardiac tissue therapy

Cardiovascular diseases make up one of the main causes of death today, with myocardial infarction and ischemic heart disease contributing a large share of the deaths reported. With mainstream clinical therapy focusing on palliative medicine following myocardial infarction, the structural changes that occur in the diseased heart will eventually lead to end-stage heart failure. Heart transplantation remains the only gold standard of cure but a shortage in donor organs pose a major problem that led to clinicians and researchers looking into alternative strategies for cardiac repair. This review will examine some alternative methods of treatment using chemokines and drugs carried by nanoparticles as drug delivering agents for the purposes of treating myocardial infarction through the promotion of revascularization. We will also provide an overview of existing studies involving such nanoparticulate drug delivery systems, their reported efficacy and the challenges facing their translation into ubiquitous clinical use.

Evaluation of the clinical relevance and limitations of current pre-clinical models of peripheral artery disease

Peripheral artery disease (PAD) has recognized treatment deficiencies requiring the discovery of novel interventions. This article describes current animal models of PAD and discusses their advantages and disadvantages. There is a need for models which more directly simulate the characteristics of human PAD, such as acute-on-chronic presentation, presence of established risk factors and impairment of physical activity.

Angiogenic gene therapy for refractory angina

INTRODUCTION

Stimulation of coronary collateral vessel growth by therapeutic angiogenesis (TA) offers an alternative treatment option for patients with refractory angina. Several TA modalities, including delivery to the heart of angiogenic growth factors (proteins or genes) and cells have been tested in clinical trials in the past two decades, but so far none of them resulted in significant therapeutic efficacy in large scale studies. This review attempts to identify the main obstacles hindering clinical success and recommends measures to overcome them in the future.

AREAS COVERED

After stating the medical need and rational for TA, and listing and briefly discussing past and current TA clinical trials, three main areas of obstacles are described: conceptual questions, technical limitations and clinical design uncertainties. Based on scientific and technical advances and lessons learned in past clinical trials, potential solutions to overcome some of these obstacles are proposed.

EXPERT OPINION

Several success criteria are identified, which apply to any TA approach of choice. It is emphasized, that each of these criteria needs to be met in future clinical trials to have a chance of therapeutic success.

Mechanisms of Amplified Arteriogenesis in Collateral Artery Segments Exposed to Reversed Flow Direction

OBJECTIVE

Collateral arteriogenesis, the growth of existing arterial vessels to a larger diameter, is a fundamental adaptive response that is often critical for the perfusion and survival of tissues downstream of chronic arterial occlusion(s). Shear stress regulates arteriogenesis; however, the arteriogenic significance of reversed flow direction, occurring in numerous collateral artery segments after femoral artery ligation, is unknown. Our objective was to determine if reversed flow direction in collateral artery segments differentially regulates endothelial cell signaling and arteriogenesis.

APPROACH AND RESULTS

Collateral segments experiencing reversed flow direction after femoral artery ligation in C57BL/6 mice exhibit increased pericollateral macrophage recruitment, amplified arteriogenesis (30% diameter and 2.8-fold conductance increases), and remarkably permanent (12 weeks post femoral artery ligation) remodeling. Genome-wide transcriptional analyses on human umbilical vein endothelial cells exposed to reversed flow conditions mimicking those occurring in vivo yielded 10-fold more significantly regulated transcripts, as well as enhanced activation of upstream regulators (nuclear factor κB [NFκB], vascular endothelial growth factor, fibroblast growth factor-2, and transforming growth factor-β) and arteriogenic canonical pathways (protein kinase A, phosphodiesterase, and mitogen-activated protein kinase). Augmented expression of key proarteriogenic molecules (Kruppel-like factor 2 [KLF2], intercellular adhesion molecule 1, and endothelial nitric oxide synthase) was also verified by quantitative real-time polymerase chain reaction, leading us to test whether intercellular adhesion molecule 1 or endothelial nitric oxide synthase regulate amplified arteriogenesis in flow-reversed collateral segments in vivo. Interestingly, enhanced pericollateral macrophage recruitment and amplified arteriogenesis was attenuated in flow-reversed collateral segments after femoral artery ligation in intercellular adhesion molecule 1(-/-) mice; however, endothelial nitric oxide synthase(-/-) mice showed no such differences.

CONCLUSIONS

Reversed flow leads to a broad amplification of proarteriogenic endothelial signaling and a sustained intercellular adhesion molecule 1-dependent augmentation of arteriogenesis. Further investigation of the endothelial mechanotransduction pathways activated by reversed flow may lead to more effective and durable therapeutic options for arterial occlusive diseases.

Anticancer effect of rapamycin on MCF-7 via downregulation of VEGF expression

The importance of mTOR signaling in tumor biology is widely accepted and a number of agents that selectively target mTOR are being developed in cancer therapy. On the other hand, it has been demonstrated that mTOR can act as an angiogenic agent. Thus, we hypothesized that the mTOR inhibitor-induced anticancer effect is affected by expression of a key angiogenic factor, vascular endothelial growth factor (VEGF) and investigated the anticancer effect underlying mTOR using an in vitro assay. The mTOR inhibitor rapamycin dose-dependently reduced the cell viability of the breast cancer cell line, MCF-7, but did not reduce the cell viability of the colon cancer cell line, HT-29. Rapamycin reduced the VEGF expression in the culture medium of MCF-7, while rapamycin did not contribute VEGF expression in the culture medium of HT-29. VEGF stimulated cell viability and VEGF inhibition reduced cell viability of MCF-7, and rapamycin dose-dependently restored the cell viability of MCF-7 reduced by rapamycin. These findings suggest that mTOR acts as a direct anticancer agent and that the mTOR-inhibitor-induced anticancer effect involved the reduced expression of VEGF in MCF-7. Our results imply that mTOR regulates the expression of VEGF and is involved in breast cancer progression.

Adequate Selection of a Therapeutic Site Enables Efficient Development of Collateral Vessels in Angiogenic Treatment With Bone Marrow Mononuclear Cells

Background

Induction of angiogenic mechanisms to promote development of collateral vessels is considered promising for the treatment of peripheral arterial diseases. Collateral vessels generally develop from preexisting arteriolar connections, bypassing the diseased artery. We speculated that induction of angiogenic mechanisms should be directed to such arteriolar connections to achieve efficient collateral development. The aim of this study was to verify this hypothesis using autologous transplantation of bone marrow mononuclear cells in the rabbit model of chronic limb ischemia.

Methods and Results

The left femoral artery was excised to induce limb ischemia in male rabbits. In this model, arteriolar connections in the left coccygeofemoral muscle tend to develop into collateral vessels, although this transformation is insufficient to alleviate the limb ischemia. In contrast, arteriolar connections in the closely located adductor muscle do not readily develop into collateral vessels. At 21 days after ischemia initiation, a sufficient number of automononuclear cells were selectively injected in the left coccygeofemoral muscle (coccygeo group) or left adductor muscle (adductor group). Evaluation of calf blood pressure ratios, blood flow in the left internal iliac artery, and angiographic scores at day 28 after injection revealed that collateral development and improvement of limb ischemia were significantly more efficient in the coccygeo group than in the adductor group. Morphometric analysis of the coccygeofemoral muscle at day 14 showed similar results.

Conclusions

Specific delivery of mononuclear cells to the coccygeofemoral but not the adductor muscle effectively improves collateral circulation in the rabbit model of limb ischemia and suggests that adequate site selection can facilitate therapeutic angiogenesis.

CXCL14 and MCP1 are potent trophic factors associated with cell migration and angiogenesis leading to higher regenerative potential of dental pulp side population cells

Introduction

The release of trophic factors from mesenchymal stem cells (MSCs) is critical for tissue regeneration. A systematic investigation of the regenerative potential of trophic factors from different MSCs, however, has not been performed. Thus, in the present study, the regenerative potential of conditioned medium (CM) from dental pulp, bone marrow, and adipose tissue-derived CD31⁻ side population (SP) cells from an individual source was compared in an ectopic tooth transplantation model.

Methods

The tooth root transplantation in an ectopic site model was used for investigation of the regenerative potential and trophic effects in vivo. Either pulp CD31⁻ SP cell populations (1×10⁶ cells) at the third to fourth passage or 5 μg/ml of CM from dental pulp, bone marrow, and adipose stem cells from four different individuals were injected into the root with collagen TE. Each root was transplanted subcutaneously in 5-week-old severe combined immunodeficiency mice. Each root with surrounding tissue was harvested for histology on days 7, 21, and 28 and for Western blot analysis and real-time reverse transcription-polymerase chain reaction (RT-PCR) analysis on day 28. Furthermore, the trophic factors responsible for the regenerative potential were identified as the upregulated genes present in pulp CD31⁻ SP cells when compared with the genes in both bone marrow and adipose CD31⁻ SP cells by using microarray analysis, real-time RT-PCR, and Western blot analysis.

Results

Transplantation of pulp CM yielded increased volume of pulp regeneration, more bromodeoxyuridine (BrdU)-positive migrated cells, and fewer caspase 3-positive cells in the regenerated pulp compared with the others. Pulp CM also demonstrated significantly increased cell migration, anti-apoptosis, and angiogenesis in C2C12 cells. Higher expression of CXCL14 and MCP1 in pulp SP cells suggested candidate trophic factors. The stimulatory effects on both migration and angiogenesis of CXCL14 and MCP1 were demonstrated in vitro. In the regenerated tissue, BrdU-positive migrated cells expressed CXCR4 and CCR2, receptors for CXCL14 and MCP1, respectively.

Conclusions

The higher regenerative potential of pulp SP cells may be due to potent trophic factors, including CXCL14 and MCP1, which promote migration and angiogenesis.

Therapeutic site selection is important for the successful development of collateral vessels

BACKGROUND

Induction of collateral development to improve tissue perfusion is a promising approach for the treatment of arterial occlusive diseases. Several growth factors and cells have been reported to increase collateral circulation; however, the appropriate site for the delivery of these factors and cells is unclear. In this study, we identified the delivery site for growth factor in a rabbit model of limb ischemia and evaluated whether specific delivery of basic fibroblast growth factor (bFGF) to this site enhanced collateral augmentation.

METHODS

The left femoral artery of Japanese white rabbits was excised to induce limb ischemia. Twenty-eight days thereafter, angiograms were obtained to identify the typical pattern of collateral development in this model. Subsequently, bFGF (100 μg) was selectively injected into the left coccygeofemoral muscle (coccygeo group) or adductor muscle (adductor group), major thigh muscles in proximity. Collateral development was evaluated at 28 days after injection, and its mechanism was assessed by immunologic and morphometric analyses of muscle samples.

RESULTS

Angiographic evaluation of this model revealed that after femoral artery excision, collateral vessels generally developed in the left coccygeofemoral muscle, whereas few collateral vessels were detected in the left adductor muscle. At 28 days after injection, calf blood pressure ratio, defined as left pressure to right pressure, was significantly higher in the coccygeo group than in the adductor group (0.85 ± 0.05 vs 0.69 ± 0.05, respectively; P < .01). Similar results were observed in blood flow through the internal iliac artery (resting: 24.6 ± 6.1 vs 17.4 ± 8.0 mL/min, P < .01; maximum: 47.4 ± 12.3 vs 33.2 ± 10.7 mL/min, P < .01) and in the angiographic score (0.67 ± 0.13 vs 0.39 ± 0.11; P < .01). Immunologic analyses of the coccygeofemoral muscle at day 3 showed marked expressions of Ki-67, monocyte chemotactic protein 1, and FGF receptor 1 in the coccygeo group compared with the adductor group. Morphometric analyses of the same muscle at day 14 also revealed that collateral vessel density and wall thickness were significantly increased in the coccygeal group compared with the adductor group.

CONCLUSIONS

These findings demonstrated that selective bFGF delivery to the coccygeofemoral muscle markedly improved collateral development and limb perfusion compared with delivery to the adductor muscle, suggesting that site selection is important in increasing therapeutic efficacy.

PHD2 regulates arteriogenic macrophages through TIE2 signalling

Occlusion of the main arterial route redirects blood flow to the collateral circulation. We previously reported that macrophages genetically modified to express low levels of prolyl hydroxylase domain protein 2 (PHD2) display an arteriogenic phenotype, which promotes the formation of collateral vessels and protects the skeletal muscle from ischaemic necrosis. However, the molecular mechanisms underlying this process are unknown. Here, we demonstrate that femoral artery occlusion induces a switch in macrophage phenotype through angiopoietin-1 (ANG1)-mediated Phd2 repression. ANG blockade by a soluble trap prevented the downregulation of Phd2 expression in macrophages and their phenotypic switch, thus inhibiting collateral growth. ANG1-dependent Phd2 repression initiated a feed-forward loop mediated by the induction of the ANG receptor TIE2 in macrophages. Gene silencing and cell depletion strategies demonstrate that TIE2 induction in macrophages is required to promote their proarteriogenic functions, enabling collateral vessel formation following arterial obstruction. These results indicate an indispensable role for TIE2 in sustaining in situ programming of macrophages to a proarteriogenic, M2-like phenotype, suggesting possible new venues for the treatment of ischaemic disorders.

Angiogenic therapy for cardiac repair based on protein delivery systems

Cardiovascular diseases remain the first cause of morbidity and mortality in the developed countries and are a major problem not only in the western nations but also in developing countries. Current standard approaches for treating patients with ischemic heart disease include angioplasty or bypass surgery. However, a large number of patients cannot be treated using these procedures. Novel curative approaches under investigation include gene, cell, and protein therapy. This review focuses on potential growth factors for cardiac repair. The role of these growth factors in the angiogenic process and the therapeutic implications are reviewed. Issues including aspects of growth factor delivery are presented in relation to protein stability, dosage, routes, and safety matters. Finally, different approaches for controlled growth factor delivery are discussed as novel protein delivery platforms for cardiac regeneration.

DVC1-0101 to treat peripheral arterial disease: a Phase I/IIa open-label dose-escalation clinical trial

We here report the results of a Phase I/IIa open-label four dose-escalation clinical study assessing the safety, tolerability, and possible therapeutic efficacy of a single intramuscular administration of DVC1-0101, a new gene transfer vector based on a nontransmissible recombinant Sendai virus (rSeV) expressing the human fibroblast growth factor-2 (FGF-2) gene (rSeV/dF-hFGF2), in patients with peripheral arterial disease (PAD). Gene transfer was done in 12 limbs of 12 patients with rest pain, and three of them had ischemic ulcer(s). No cardiovascular or other serious adverse events (SAEs) caused by gene transfer were detected in the patients over a 6-month follow-up. No infectious viral particles, as assessed by hemagglutination activity, were detected in any patient during the study. No representative elevation of proinflammatory cytokines or plasma FGF-2 was seen. Significant and continuous improvements in Rutherford category, absolute claudication distance (ACD), and rest pain were observed (P < 0.05 to 0.01). To the best of our knowledge, this is the first clinical trial of the use of a gene transfer vector based on rSeV. The single intramuscular administration of DVC1-0101 to PAD patients was safe and well tolerated, and resulted in significant improvements of limb function. Larger pivotal studies are warranted as a next step.

Exercise training and peripheral arterial disease

Peripheral arterial disease (PAD) is a common vascular disease that reduces blood flow capacity to the legs of patients. PAD leads to exercise intolerance that can progress in severity to greatly limit mobility, and in advanced cases leads to frank ischemia with pain at rest. It is estimated that 12 to 15 million people in the United States are diagnosed with PAD, with a much larger population that is undiagnosed. The presence of PAD predicts a 50% to 1500% increase in morbidity and mortality, depending on severity. Treatment of patients with PAD is limited to modification of cardiovascular disease risk factors, pharmacological intervention, surgery, and exercise therapy. Extended exercise programs that involve walking approximately five times per week, at a significant intensity that requires frequent rest periods, are most significant. Preclinical studies and virtually all clinical trials demonstrate the benefits of exercise therapy, including improved walking tolerance, modified inflammatory/hemostatic markers, enhanced vasoresponsiveness, adaptations within the limb (angiogenesis, arteriogenesis, and mitochondrial synthesis) that enhance oxygen delivery and metabolic responses, potentially delayed progression of the disease, enhanced quality of life indices, and extended longevity. A synthesis is provided as to how these adaptations can develop in the context of our current state of knowledge and events known to be orchestrated by exercise. The benefits are so compelling that exercise prescription should be an essential option presented to patients with PAD in the absence of contraindications. Obviously, selecting for a lifestyle pattern that includes enhanced physical activity prior to the advance of PAD limitations is the most desirable and beneficial.

Role of fibroblast growth factor signaling in vascular formation and maintenance: orchestrating signaling networks as an integrated system

The vascular system has begun to be perceived as a dynamic organ actively controlling a wide variety of physiological processes. The structural and functional integrity of blood vessels, regulated by signaling activities finely modulating cell-cell and cell-matrix interactions, is crucial for vessel physiology, as well as basic functionality of the tissue. Throughout the process of new vessel formation, while blood vessels are actively reorganized and remodeled with migration and proliferation of vascular cells, maintenance of vascular barrier function is essentially important. These conflicting properties, i.e., dynamic cellular mobilization and maintenance of barrier integrity, are simultaneously achieved through the interaction of highly organized signaling networks governing coordinated cell-cell interplay. Recent evidence suggests that the fibroblast growth factor (FGF) system plays a regulatory role in several physiological conditions in the vascular system. In this article, we will attempt to summarize current knowledge in order to understand the mechanism of this coordination and evaluate the pivotal role of FGF signaling in integrating a diverse range of signaling events in vascular growth and maintenance.

PEG-albumin plasma expansion increases expression of MCP-1 evidencing increased circulatory wall shear stress: an experimental study

Treatment of blood loss with plasma expanders lowers blood viscosity, increasing cardiac output. However, increased flow velocity by conventional plasma expanders does not compensate for decreased viscosity in maintaining vessel wall shear stress (WSS), decreasing endothelial nitric oxide (NO) production. A new type of plasma expander using polyethylene glycol conjugate albumin (PEG-Alb) causes supra-perfusion when used in extreme hemodilution and is effective in treating hemorrhagic shock, although it is minimally viscogenic. An acute 40% hemodilution/exchange-transfusion protocol was used to compare 4% PEG-Alb to Ringer's lactate, Dextran 70 kDa and 6% Hetastarch (670 kDa) in unanesthetized CD-1 mice. Serum cytokine analysis showed that PEG-Alb elevates monocyte chemotactic protein-1 (MCP-1), a member of a small inducible gene family, as well as expression of MIP-1α, and MIP-2. MCP-1 is specific to increased WSS. Given the direct link between increased WSS and production of NO, the beneficial resuscitation effects due to PEG-Alb plasma expansion appear to be due to increased WSS through increased perfusion and blood flow rather than blood viscosity.

FGF-dependent regulation of VEGF receptor 2 expression in mice

Numerous studies have suggested a link between the angiogenic FGF and VEGF signaling pathways; however, the nature of this link has not been established. To evaluate this relationship, we investigated VEGF signaling in ECs with disrupted FGF signaling in vitro and in vivo. ECs lacking FGF signaling became unresponsive to VEGF, caused by downregulation of VEGF receptor 2 (VEGFR2) expression after reduced Vegfr2 enhancer activation. FGF mediated VEGFR2 expression via activation of Erk1/2. Transcriptional analysis revealed that Ets transcription factors controlled VEGFR2 expression in an FGF- and Erk1/2-dependent manner. Mice with defective FGF signaling exhibited loss of vascular integrity and reduced vascular morphogenesis. Thus, basal FGF stimulation of the endothelium is required for maintenance of VEGFR2 expression and the ability to respond to VEGF stimulation and accounts for the hierarchic control of vascular formation by FGFs and VEGF.

Intramural coronary lipid injection induces atheromatous lesions expressing proinflammatory chemokines: implications for the development of a porcine model of atherosclerosis

BACKGROUND

Intramural delivery of lipids into the coronaries of pigs fed high-cholesterol diet results in the formation of localized atherosclerotic-like lesions within 12 weeks. These lesions are located in positively remodeled vessels and are associated to the development of abundant adventitial vasa vasorum and mononuclear cell infiltrate. In this study, we aimed to analyze the degree of expression of various inflammatory chemokines within the developed lesions compared with control segments injected with saline.

METHODS

Balloon injury was performed in 15 coronary arteries of pigs fed high-cholesterol diet for 12 weeks. Two weeks after procedure, 60 coronary segments were randomized to either intramural injections of complex lipids (n=30) or normal saline (n=30). Neovessel density in the lesions was analyzed by lectin stain. Segments were processed for RNA expression of inflammatory chemokines such as monocyte chemoattractant protein-1 and vascular endothelial growth factor.

RESULTS

At 12 weeks, the percentage area of stenosis seen in histological sections was modest in both groups (lipids: 17.3±15 vs. saline: 32.4±22.8, P=.017). The lipid group showed higher vasa vasorum (VV) quantity (saline: 18.2±14.9 VV/section vs. lipids: 30.6±21.6 VV/section, P<.05) and vasa vasorum density (saline: 7.3±4.6 VV/mm(2) vs. lipids: 16.5±9 VV/mm(2), P<.001). In addition, monocyte chemoattractant protein-1 expression was higher in the lipid group (1.5±1.12) compared with saline control group (0.83±0.34, P<.01). Vascular endothelial growth factor expression was also higher in the lipid group (1.36±0.9) compared with saline group (0.87±0.33, P<.05).

CONCLUSION

The intramural injection of complex lipids into the coronary arteries of pigs maintained in a high-cholesterol diet results in focal lesions located in positively remodeled vessels that have a high neovessel count and express proinflammatory chemokines.

Leptin augments cerebral hemodynamic reserve after three-vessel occlusion: distinct effects on cerebrovascular tone and proliferation in a nonlethal model of hypoperfused rat brain

The adipocytokine leptin has distinct functions regulating vascular tone, inflammation, and collateral artery growth. Arteriogenesis is an inflammatory process and provides a mechanism to overcome the effects of vascular obstruction. We, therefore, tested the effects of leptin in hypoperfused rat brain (three-vessel occlusion). Systemic leptin administration for 1 week after occlusion surgery increased cerebral hemodynamic reserve similar to granulocyte-macrophage colony-stimulating factor (GM-CSF), as indicated by improved CO(2) reactivity (vehicle 0.53%±0.26% versus leptin 1.05%±0.6% per mm Hg arterial pCO(2), P<0.05). Infusion of microspheres under maximal vasodilation failed to show a positive effect of leptin on cerebral perfusion (vehicle 64.9%±4.5% versus leptin 66.3%±7.0%, occluded/nonoccluded hemisphere). Acute treatment with GM-CSF led to a significant increased CO(2) reactivity and cerebral perfusion (79.2%±8.1% versus 64.9%±4.5%, P<0.05). Vasoconstrictive response of isolated rat carotid artery rings, after phenylephrine was attenuated at 24  hours following preincubation with leptin, was unaffected by removal of endothelium but abrogated by coculture with N-(omega)-nitro-L-arginine methylester, pointing toward an inducible nitric oxide synthase-mediated mechanism. In chronic cerebral hypoperfusion, acute leptin treatment restored the hemodynamic reserve of the cerebral vasculature through its effects on vascular tone, while leaving vascular outward remodeling unaffected. Our results, for the first time, reveal a protective role of leptin on vascular function in hemodynamically compromised brain tissue.

Chemokines in angiogenesis

Chemokines are a family of small heparin-binding proteins, mostly known for their role in inflammation and immune surveillance, which have emerged as important regulators of angiogenesis. Chemokines influence angiogenesis either through recruitment of pro-angiogenic immune cells and endothelial progenitors to the neo-vascular niche or via direct regulation of endothelial function downstream of activation of G-protein coupled chemokine receptors. The dual function of chemokines in regulating immune response and angiogenesis confers a central role in modulating the tissue microenvironment. Therefore, chemokines may constitute attractive targets for therapeutic intervention in several pathological disorders. This review will summarize the current understanding of the role of chemokines in angiogenesis, and give an overview of angiostatic and angiogenic chemokines and their crosstalk with other angiogenic factors.

Overexpression of integrin beta 5 enhances the paracrine properties of circulating angiogenic cells via Src kinase-mediated activation of STAT3

OBJECTIVE

To determine the intracellular mechanisms mediating the angiogenic effects of integrin alpha v beta 5 overexpression in circulating angiogenic cells (CACs).

METHODS AND RESULTS

Integrin alpha v beta 5 is expressed on angiogenic endothelial cells, and integrin alpha v beta 5 activation was shown to improve the reparative functions of endothelial progenitors within the cardiovascular system. CACs were transiently transfected with the full-length cDNA of human integrin beta 5 (CAC-ITGB5) or control-vector (CAC-vector). Integrin beta 5 overexpression was confirmed using flow cytometry, Western blot, and PCR analysis; it enhanced the angiogenic capacities of CACs in vitro (spheroid and Matrigel angiogenesis assay) and stimulated new vessel formation in vivo (murine hind limb ischemia model). Overexpression of ITGB5 resulted in integrin alpha v beta 5 phosphorylation and activation of Src kinase and signal transducer and activator of transcription (STAT) 3. Furthermore, elevated mRNA and protein expression of the CXC chemokine CXCL8 and the CC chemokine CCL2 was detected in CAC-ITGB5, and conditioned medium from CAC-ITGB5 enhanced the sprouting of coincubated human endothelial cells in a STAT3-, CXCL8-, and CCL2-dependent manner.

CONCLUSIONS

Src kinase-mediated activation of STAT3 and subsequent angiogenic gene expression mediate the effects of integrin alpha v beta 5 and may be exploited to enhance the paracrine activities of CACs.

An Autocrine Linkage Between Matrix Metalloproteinase-14 and Tie-2 Via Ectodomain Shedding Modulates Angiopoietin-1–Dependent Function in Endothelial Cells

Objective— The angiopoietin (Ang)–Tie-2 system plays a critical role during fetal and adult angiogenesis. Herein, we explored the Tie-2 shedding–related molecular mechanisms and the pathophysiological significance.

Methods and Results— By using a mouse hindlimb ischemia model, we observed dissociated expression between the full-length Tie-2 (fTie-2) protein and Tie-2 mRNA in thigh muscles 1 day after an ischemic operation, suggesting that fTie-2 expression was modified through the posttranscriptional regulation in vivo. A soluble form of Tie-2 produced in human umbilical vein endothelial cells was dramatically suppressed by treatment with siRNA–matrix metalloproteinase (MMP) 14 or tissue inhibitor of metalloproteinase 3, resulting in an increase in cellular fTie-2 and thereby enhancing Ang-1–dependent Akt phosphorylation and Akt-dependent endothelial functions, such as Ang-2 downregulation or an increase of endothelial viability. Phorbol-12-myristate-13 acetate (PMA) upregulates MMP-14 mRNA via protein kinase C–extracellular signal–regulated kinase pathways, and enhanced soluble Tie-2 production in an MMP-14–dependent manner, resulting in a reduction of cellular fTie-2. In addition, the PMA-induced soluble Tie-2 was mediated by the protein kinase C–extracellular signal–regulated kinase signaling pathways. Finally, downregulation of tissue inhibitor of metalloproteinase 3 and upregulation of MMP-14 mRNA were confirmed in ischemic thigh muscles 1 day after the operation.

Conclusion— An autocrine linkage between the endothelial protein kinase C–MMP-14 axis and Tie-2 shedding was shown to be a novel regulatory mechanism for the Ang–Tie-2 system and may play a role in modulating endothelial function during angiogenesis.

Regulation of the expression balance of angiopoietin-1 and angiopoietin-2 by Shh and FGF-2

Sonic hedgehog (Shh) is a typical morphogen to regulate epithelial-mesenchymal interactions during embryonic development. Shh is also an indirect angiogenic agent upregulating other angiogenic factors, including angiopoietin-1 (Ang-1). Recent studies revealed that angiogenesis induced by Shh is characterized by distinct large-diameter vessels with less branching. Ang-1 promotes blood vessel maturation, and angiopoietin-2 (Ang-2) counteracts Ang-1 activity and regulates vascular branching. Thus, we hypothesized that Shh-induced angiogenesis is affected by expression of Ang-1 and Ang-2, and we investigated the regulatory system of angiopoietins by Shh in vitro. Shh enhanced Ang-1 expression but did not enhance vascular endothelial growth factor in fibroblasts. The upregulation of Ang-1 expression by Shh was significantly decreased by fibroblast growth factor-2 (FGF-2), a potent angiogenic factor. Furthermore, FGF-2 increased the expression of Ang-2 in endothelial cells. These findings suggest that Shh and FGF-2 regulate the expression balance of vascular morphogens Ang-1 and Ang-2 and are involved in angiogenesis.

Dual delivery of VEGF and MCP-1 to support endothelial cell transplantation for therapeutic vascularization

Transplantation of endothelial cells (EC) for therapeutic vascularization is a promising approach in tissue engineering but has yet to be proven effective in clinical trials. This cell-based therapy is hindered by significant apoptosis of EC upon transplantation as well as poor recruitment of host mural cells to stabilize nascent vessels. Here, we address these deficiencies by augmenting endothelial cell transplantation with dual delivery of vascular endothelial growth factor (VEGF) - to improve survival of transplanted EC - and monocyte chemotactic protein-1 (MCP-1) - to induce mural cell recruitment. We produced alginate microparticles that deliver VEGF and MCP-1 with distinct release kinetics and that can be integrated into a collagen/fibronectin (protein) gel construct for delivery of EC. Combined delivery of VEGF and MCP-1 increased functional vessel formation from transplanted EC and also led to a higher number of smooth muscle cell-invested vessels than did EC therapy alone. Despite the well-known role of MCP-1 in inflammation, these beneficial effects were accomplished without a long-term increase in monocyte/macrophage recruitment or a shift to a pro-inflammatory (M1) macrophage phenotype. Overall, these data suggest a potential benefit of combined delivery of MCP-1 and VEGF from EC-containing hydrogels as a strategy for therapeutic vascularization.

Autocrine loop between vascular endothelial growth factor (VEGF)-C and VEGF receptor-3 positively regulates tumor-associated lymphangiogenesis in oral squamoid cancer cells

Numerous past studies have suggested a critical role of the paracrine effect between tumor vascular endothelial growth factor (VEGF)-C and lymphatic FLT-4 in solid tumor-associated lymphangiogenesis. In contrast, the pathophysiological role of tumor cell-associated FLT-4 in tumor progression remains to be elucidated. Here, we investigated this role using a tumor implantation model. SAS cells, an oral squamous carcinoma cell line expressing both VEGF-C and FLT-4 but neither FLK-1/KDR nor VEGF-D were adopted for experiments. Stable transformants of dominant-negative (dn) SAS cells were established in which the cytoplasmic domain-deleted FLT-4 was exogenously overexpressed, which can lead to inactivation of endogenous FLT-4 through competitive antagonism and is associated with down-activation of endogenous FLT-4-related intracellular signals. In vitro and in vivo proliferation assays showed lower proliferative activity of dn-SAS cells. An immunohistochemical study revealed that the tumor lymphangiogenesis was significantly suppressed, and the level of human VEGF-C mRNA was significantly lower in dn-SAS cell-derived tumor tissues. Moreover, in vitro studies demonstrated that the significant suppression of VEGF-C and VEGF-A expression was evident in dn-SAS cells or wild-type SAS cells treated with either the FLT-4 kinase inhibitor MAZ51 or the inhibitor of FLT-4-related signals. These findings together suggested that the VEGF-C/FLT-4 autocrine loop in tumor cells was a potential enhancer system to promote cancer progression, and FLT-4 in tumor tissue might become an effective target for cancer therapy.

Selective and sustained delivery of basic fibroblast growth factor (bFGF) for treatment of peripheral arterial disease: results of a phase I trial

OBJECTIVES

The aim of this study was to evaluate the safety of selective and sustained delivery of basic fibroblast growth factor (bFGF) using acidic gelatine hydrogel microspheres (AGHMs) for the treatment of peripheral arterial disease (PAD).

MATERIALS AND METHODS

We conducted a non-randomised and uncontrolled trial involving prospective observation of eight patients (eight limbs) with PAD - five limbs with arteriosclerosis obliterans and three limbs with thromboangiitis obliterans, five limbs (three arms and two legs) with critical limb ischaemia (CLI) and three limbs with intermittent claudication (IC) - who were followed up for 6 months or more. AGHM suspension containing 100 microg bFGF was infused into the artery of the affected limb. Besides evaluation of safety and changes in symptoms, resting ankle-brachial pressure index measurement and transcutaneous PO(2) (tcPO(2)), angiography were conducted at baseline and then at various time points. Skin perfusion pressure as an index of CLI and claudication distance as an index of IC were also used to assess clinical improvement and limb perfusion.

RESULTS

No serious adverse events were observed. All cases showed improvement in symptoms, although this was temporary in some patients.

CONCLUSION

Selective delivery of bFGF using AGHMs was suggested to be safe and well-tolerated in patients with PAD.

Stretch-Induced Activation of the Transcription Factor Activator Protein-1 Controls Monocyte Chemoattractant Protein-1 Expression During Arteriogenesis

Cerebral, coronary, and peripheral artery diseases combined represent the most frequent cause of death in developed nations. The underlying progressive occlusion of large conductance arteries can partially be compensated for by transformation of preexisting collateral arterioles to small artery bypasses, a process referred to as arteriogenesis. Because biomechanical forces have been implicated in the initiation of arteriogenesis, we have investigated the mechanosensitive expression of a pivotal proarteriogenic molecule, monocyte chemoattractant protein (MCP)-1, which governs the recruitment of circulating monocytes to the wall of the remodeling collateral arterioles. Using a new ear artery ligation model and the classic hindlimb ischemia model in mice, we noted that MCP-1 expression is significantly increased in collateral arterioles undergoing arteriogenesis already 24 hours after its onset. By mimicking proarteriogenic perfusion conditions in small mouse arteries, we observed that MCP-1 expression is predominantly upregulated in the smooth muscle cells, which solely sense changes in circumferential wall tension or stretch. Subsequent analyses of cultured endothelial and smooth muscle cells confirmed that cyclic stretch but not shear stress upregulates MCP-1 expression in these cells. Blockade of the mechanosensitive transcription factor activator protein-1 by using a specific decoy oligodeoxynucleotide abolished this stretch-induced MCP-1 expression. Likewise, topical administration of the decoy oligodeoxynucleotide to the mouse ear abrogated arteriogenesis through downregulation of MCP-1 expression and monocyte recruitment. Collectively, these findings point toward a stretch-induced activator protein-1–mediated rise in MCP-1 expression in vascular smooth muscle cells as a critical determinant for the initiation of arteriogenesis.

Recombinant Human Bone Morphogenetic Protein-2 as an Osteoinductive Biomaterial and a Biodegradable Carrier in a Rabbit Ulnar Defect Model

We investigated early local changes induced by recombinant human bone morphogenetic protein (rhBMP)-2 and a novel carrier, poly[L-lactide-co-glycolide] copolymer-coated gelatin sponge (PGS). A 1.5 cm segmental bone defect was created in the diaphysis of the right ulna of male Japanese white rabbit. Defects received PGS with or without rhBMP-2 (0, 0.4, or 1 mg/cm3) and were harvested at 3, 7, 14, 21, or 28 days post implantation for histological examination. Immuno-staining for vascular endothelial growth factor (VEGF) was also performed. Spindle-shaped cells were observed in the rhBMP-2-treated groups 3 and 7 days after implantation. Bone regeneration was detected after 14 days in the rhBMP-2-treated groups and the bone area increased with time and dose. Expression of VEGF was observed in all groups at 3 days and was maintained by 14 days only in the defects treated with rhBMP-2 at a dose of 1 mg. These results indicate that rhBMP-2 exert its osteo-inductive activities via the promotion of osteogenic cell mobilization, and possibly via angiogenesis based on VEGF induction. Foreign-body reactions to the implanted PGS were similar to those observed when either poly[L-lactide-co-glycolide] copolymer or gelatin was individually implanted. These results indicate that the PGS is a useful and safe carrier for rhBMP-2.

Fibroblast growth factor regulation of neovascularization

PURPOSE OF REVIEW

Fibroblast growth factors are potent angiogenic inducers; however, their precise roles in angiogenesis have not been well understood. In this review, we will focus on specific roles played by fibroblast growth factors in neovascularization.

RECENT FINDINGS

Although fibroblast growth factors promote a strong angiogenic response, it has been suggested that FGF-induced angiogenesis requires activation of the vascular endothelial growth factor system. Recent findings have endorsed the view of indirect contribution of fibroblast growth factor signaling to vascular development. A study using embryoid bodies demonstrated a nonimmediate role played by fibrobalst growth factor receptor 1 in vasculogenesis as vascular endothelial growth factor supplementation was sufficient to promote vascular development in Fgfr1-/- embryoid bodies. Moreover, another line of evidence indicated that myocardial fibroblast growth factor signaling is essential for mouse coronary development. The key role of fibroblast growth factor signaling in this process is Hedgehog activation, which induces vascular endothelial growth factor expression and formation of the coronary vasculature. In addition to vascular endothelial growth factor interaction, fibroblast growth factors can control neovascularization by influencing other growth factors and chemokines such as platelet-derived growth factor, hepatocyte growth factor and monocyte chemoattractant protein-1, contributing to development of mature vessels and collateral arteries.

SUMMARY

Although fibroblast growth factors are potent angiogenic factors, they may indirectly control neovascularization in concert with other growth factors. Thus, the unique role played by fibroblast growth factors might be organization of various angiogenic pathways and coordination of cell-cell interactions in this process.

Statins restore ischemic limb blood flow in diabetic microangiopathy via eNOS/NO upregulation but not via PDGF-BB expression

3-Hydroxy-3-methyl-glutaryl CoA reductase inhibitors, or statins, have pleiotropic effects and can protect the vasculature in a manner independent of their lipid-lowering effect. The effectiveness of statins in reducing the risk of coronary events has been shown even in patients with diabetes, and their effects on diabetic complications have been reported. Using a model of severe hindlimb ischemia in streptozotocin-induced diabetic mice (STZ-DM), we investigated the effects and mechanisms of statin therapy in diabetic angiopathy in ischemic hindlimbs. As a result, STZ-DM mice frequently lost their hindlimbs after induced ischemia, whereas non-DM mice did not. Supplementation with statins significantly prevented autoamputation. We previously showed that diabetic vascular complications are caused by impaired expression of PDGF-BB, but statin therapy did not enhance PDGF-BB expression. Statins helped enhance endogenous endothelial nitric oxide (NO) synthase (eNOS) expression. Furthermore, the inhibition of NO synthesis by the administration of Nω-nitro-l-arginine methyl ester impaired the ability of statins to prevent STZ-DM mouse limb autoamputation, indicating that the therapeutic effect of statins in hindlimb ischemia in STZ-DM mice occurs via the eNOS/NO pathway. A combination therapy of statins and PDGF-BB gene supplementation was more effective for diabetic angiopathy than either therapy alone. In conclusion, these findings indicate that statin therapy might be useful for preventing intractable diabetic foot disease in patients with diabetic angiopathy.

Role of ephrinB2 expression in endothelial cells during arteriogenesis: impact on smooth muscle cell migration and monocyte recruitment

Expression of the arterial marker molecule ephrinB2 in endothelial cells is a prerequisite for adequate remodeling processes of the developing or angiogenic vasculature. Although its role in these processes has been extensively studied, the impact of ephrinB2 on the remodeling of adult arteries is largely unknown. To this end, we analyzed its expression during a biomechanically induced arteriolar remodeling process known as arteriogenesis and noted a significant increase in ephrinB2 expression under these conditions. By examining those biomechanical forces presumed to drive arteriogenesis, we identified cyclic stretch as a critical inducer of ephrinB2 expression in endothelial cells. Subsequent functional analyses in vitro revealed that endothelial cells expressing ephrinB2 limit the migration of smooth muscle cells, thereby enhancing segregation of both cell types. Moreover, MCP-1 induced transmigration of monocytes through a monolayer of endothelial cells overexpressing a truncated variant of ephrinB2 was clearly impeded. Taken together, these data suggest that expression of ephrinB2 in adult endothelial cells is up-regulated during arterial remodeling and controlled by cyclic stretch, a well-known inducer of such processes. This stretch-induced ephrinB2 expression may be pivotal for arteriogenesis as it limits smooth muscle cell migration within defined borders and controls monocyte extravasation.