Basic fibroblast growth factor stimulates angiogenesis in the hindlimb of hyperglycemic rats

bFGF alleviates diabetes-associated endothelial impairment by downregulating inflammation via S-nitrosylation pathway

Protein S-nitrosylation is a reversible protein modification implicated in both physiological and pathophysiological regulation of protein function. However, the relationship between dysregulated S-nitrosylation homeostasis and diabetic vascular complications remains incompletely understood. Here, we demonstrate that basic fibroblast growth factor (bFGF) is a key regulatory link between S-nitrosylation homeostasis and inflammation, and alleviated endothelial dysfunction and angiogenic defects in diabetes. Subjecting human umbilical vein endothelial cells (HUVECs) to hyperglycemia and hyperlipidemia significantly decreased endogenous S-nitrosylated proteins, including S-nitrosylation of inhibitor kappa B kinase β (IKKβ^C179) and transcription factor p65 (p65^C38), which was alleviated by bFGF co-treatment. Pretreatment with carboxy-PTIO (c-PTIO), a nitric oxide scavenger, abolished bFGF-mediated S-nitrosylation increase and endothelial protection. Meanwhile, nitrosylation-resistant IKKβ^C179S and p65^C38S mutants exacerbated endothelial dysfunction in db/db mice, and in cultured HUVECs subjected to hyperglycemia and hyperlipidemia. Mechanistically, bFGF-mediated increase of S-nitrosylated IKKβ and p65 was attributed to synergistic effects of increased endothelial nitric oxide synthase (eNOS) and thioredoxin (Trx) activity. Taken together, the endothelial protective effect of bFGF under hyperglycemia and hyperlipidemia can be partially attributed to its role in suppressing inflammation via the S-nitrosylation pathway.

Basic Fibroblast Growth Factor-Anchored Multilayered Mesenchymal Cell Sheets Accelerate Periosteal Bone Formation

Cell-based regenerative therapy has the potential to repair bone injuries or large defects that are recalcitrant to conventional treatment methods, including drugs and surgery. Here, we developed a multilayered cell-based bone formation system using cells coated with fibronectin-gelatin (FN-G) nanofilms. The multilayered mesenchymal cells (MLMCs) were formed after two days of culture and were shown to express higher levels of BMP-2 and VEGF compared to monolayer cultures of MCs. The MLMCs were used as a graft material in combination with a fusion protein consisting of basic fibroblast growth factor (bFGF), polycystic kidney disease (PKD) domain, and the collagen-binding domain (CBD) of Clostridium histolyticum collagenase. In femur sites grafted with the MLMCs, significantly higher levels of callus volume and bone mineral content were observed compared to the sham controls. The callus volume and bone mineral content were further increased in femur sites grafted with bFGF-PKD-CBD/MLMCs. Taken together, these results suggest that bFGF-PKD-CBD/MLMCs, which can be simply and rapidly generated in vitro, have the potential to promote bone repair when grafted into large defect sites.

Stimulation of angiogenesis and survival of endothelial cells by human monoclonal Tie2 receptor antibody

Angiopoietin-1 (Ang1) and its endothelium-specific receptor, tyrosine kinase with Ig and epidermal growth factor homology domain 2 (Tie2), play critical roles in vascular development. Although the Ang1/Tie2 system has been considered a promising target for therapeutic neovascularization, several imitations of large-scale production have hampered the development of recombinant Ang1 for therapeutics. In this study, we produced a fully human agonistic antibody against Tie2, designated 1-4h, and tested the applicability of 1-4h as an alternative to native Ang1 in therapeutic angiogenesis. 1-4h significantly enhanced the phosphorylation of Tie2 in a dose- and time-dependent manner in human Tie2-expressing HEK293 cells and human umbilical vein endothelial cells. Moreover, 1-4h induced the activation of Tie2-mediated intracellular signaling such as AKT, eNOS, MAPK, and Focal Adhesion Kinase p125(FAK). In addition, 1-4h increased the chemotactic motility and capillary-like tube formation of endothelial cells in vitro and enhanced the survival of serum-deprived endothelial cells. Taken together, our data clearly suggest that a human Tie2 agonistic antibody is a potentially useful therapeutic approach for the treatment of several ischemic diseases including delayed-wound healing and ischemic heart and limb diseases.

Therapeutic angiogenesis for revascularization in peripheral artery disease

Therapeutic angiogenesis for peripheral artery disease (PAD), achieved by gene and cell therapy, has recently raised a great deal of hope for patients who cannot undergo standard revascularizing treatment. Although pre-clinical studies gave very promising data, still clinical trials of gene therapy have not provided satisfactory results. On the other hand, cell therapy approach, despite several limitations, demonstrated more beneficial effects but initial clinical studies must be constantly validated by larger randomized, multi-center, double-blinded, placebo-controlled trials. This review focuses on previous and recent gene and cell therapy studies for limb ischemia, including both experimental and clinical research, and summarizes some important papers published in this field. Moreover, it provides a short comment on combined gene and cell therapy approach on the example of heme oxygenase-1 overexpressing cells with therapeutic properties.

Peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α) enhances engraftment and angiogenesis of mesenchymal stem cells in diabetic hindlimb ischemia

To examine whether the peroxisome proliferator-activated receptor-γ coactivator-1α (PGC-1α), a key regulator linking angiogenesis and metabolism, could enhance the engraftment and angiogenesis of mesenchymal stem cells (MSCs) in diabetic hindlimb ischemia, we engineered the overexpression of PGC-1α within MSCs using an adenoviral vector encoding green fluorescent protein and PGC-1α, and then tested the survivability and angiogenesis of MSCs in vitro and in vivo. Under the condition of hypoxia concomitant with serum deprivation, the overexpression of PGC-1α in MSCs resulted in a higher expression level of hypoxia-inducible factor-1α (Hif-1α), a greater ratio of B-cell lymphoma leukemia-2 (Bcl-2)/Bcl-2-associated X protein (Bax), and a lower level of caspase 3 compared with the controls, followed by an increased survival rate and an elevated expression level of several proangiogenic factors. In vivo, the MSCs modified with PGC-1α could significantly increase the blood perfusion and capillary density of ischemic hindlimb of the diabetic rats, which was correlated to an improved survivability of MSCs and an increased level of several proangiogenic factors secreted by MSCs. We identified for the first time that PGC-1α could enhance the engraftment and angiogenesis of MSCs in diabetic hindlimb ischemia.

Effects of basic fibroblast growth factor on experimental diabetic neuropathy in rats

Basic fibroblast growth factor (bFGF) stimulates angiogenesis and induces neural cell regeneration. We investigated the effects of bFGF on diabetic neuropathy in streptozotocin-induced diabetic rats. Diabetic rats were treated with human recombinant bFGF as follows: 1) intravenous administration, 2) intramuscular injection into thigh and soleus muscles with cross-linked gelatin hydrogel (CGH), and 3) intramuscular injection with saline. Ten or 30 days later, the motor nerve conduction velocity (MNCV) of the sciatic-tibial and caudal nerves, sensitivity to mechanical stimuli, sciatic nerve blood flow (SNBF), and retinal blood flow (RBF) were measured. Delayed MNCV in the sciatic-tibial and caudal nerves, hypoalgesia, and reduced SNBF in diabetic rats were all ameliorated by intravenous administration of bFGF after 10, but not 30, days. Intramuscular injection of bFGF with CGH also improved sciatic-tibial MNCV, hypoalgesia, and SNBF after 10 and 30 days, but caudal MNCV was not improved. However, intramuscular injection of bFGF with saline had no significant effects. bFGF did not significantly alter RBF in either normal or diabetic rats. These observations suggest that bFGF could have therapeutic value for diabetic neuropathy and that CGH could play important roles as a carrier of bFGF.

[Diabetes and peripheral arterial occlusive disease: therapeutic potential and pro-angiogenic strategies]

Cardiovascular complications are the leading cause of morbidity and mortality in patients with diabetes mellitus; up to 80% of deaths in patients with diabetes are closely associated with vascular disease. The ability of the organism to form a collateral network of blood vessels constitutes an important response to vascular occlusive disease and determines to a large part the clinical consequences and severity of tissue ischemia. The development of new vessels is significantly reduced in diabetic patients with coronary or peripheral artery disease. This probably contributes to the severe course of limb ischemia in diabetic patients, in which peripheral artery disease often results in foot ulceration and lower extremity amputation. Diabetic retinopathy remains one of the major causes of acquired blindness in developed nations. This is true despite the development of laser treatment, which can prevent blindness in the majority of those who develop macular edema or proliferative diabetic retinopathy. The hallmark of diabetic retinopathy is the lack of microvessels in the macula, leading to hypoxia, associated with peripheral retinal neovascularization that may ultimately cause severe vitreous cavity bleeding and/or retinal detachment. The factors that stimulate retinal blood vessel growth have not been fully defined, but there is accumulating evidence that the renin-angiotensin-bradykinin system may be involved in a number of retinal vascular disorders, including retinopathy of prematurity and proliferative diabetic retinopathy. Only a few studies have specifically evaluated the effect of diabetes on angiogenesis in ischemic vascular disease and in the retina. Moreover, the mechanisms by which diabetes could both limit the formation of new blood vessels in most organs and simultaneously induce proliferative diabetic retinopathy remain largely undefined. In the present review, we aimed to briefly describe the main molecular mechanisms involved in the ischemia-induced angiogenesis, and their alterations in diabetes. Possible therapeutic strategies to restore angiogenesis in diabetic patients are also listed.

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.

Haptoglobin expression and activity during coronary collateralization

Coronary collateral development relies on the coordinated secretion of growth factors. However, alone they are insufficient for permanent collateral growth. We utilized proteomics to identify other important proteins in the extracellular environment that could facilitate collateralization. Chronically instrumented dogs developed coronary collaterals by the repetitive occlusion method. Subendocardial (0.19 ± 0.04, 0.27 ± 0.06, 0.48 ± 0.10, and 0.81 ± 0.11 ml·min−1·g−1 on days 1, 7, 14, and 21, respectively) and subepicardial (0.14 ± 0.01, 0.36 ± 0.06, 0.51 ± 0.07, and 0.71 ± 0.08 ml·min−1·g−1 on days 1, 7, 14, and 21, respectively) blood flow increased in animals subjected to repetitive occlusion. Sham animals exhibited no changes in blood flow. Myocardial interstitial fluid (MIF) from both groups was analyzed by two-dimensional electrophoresis with matrix-assisted laser desorption/ionization time-of-flight identification. The acute-phase protein haptoglobin was identified in the group subjected to repetitive occlusion. ELISA of MIF showed haptoglobin to be elevated at all time points of collateral development compared with sham, with maximal production on day 7. Purified haptoglobin dose dependently stimulated endothelial cells to form tubes and vascular smooth muscle cells to migrate. Purified haptoglobin did not stimulate proliferation of either cell type. The relative contribution of haptoglobin to the chemotactic properties of MIF was tested using a neutralizing antibody. Neutralized MIF could not stimulate smooth muscle cells to migrate at any time during collateral development. Endothelial cell tube formation was inhibited after the midpoint of collateralization. Therefore, the acute-phase protein haptoglobin plays a critical role during coronary collateralization.

Deep vein thrombosis resolution is not accelerated with increased neovascularization

INTRODUCTION

Deep venous thrombosis (DVT) resolution involves fibrinolysis, neovascularization, and fibrosis. We hypothesized that promoting neovascularization would accelerate DVT resolution.

METHODS

A rat model of stasis DVT was produced with proximal ligation of the inferior vena cava (IVC) and all visible tributaries. One microg of interferon inducible protein (IP-10; angiostatic chemokine), basic fibroblast growth factor (bFGF; pro-angiogenic cytokine), epithelial neutrophil activating protein (ENA-78; pro-angiogenic chemokine), or saline solution control was injected into the IVC after ligation, and then via tail vein injection daily until sacrifice at either 4 or 8 days. Peripheral blood counts were measured, and thrombus weight was recorded at sacrifice. Laser Doppler in vivo imaging was used to estimate post-thrombotic IVC blood flow. Immunohistologic assessment of the thrombosed IVC for polymorphonuclear neutrophils (PMNs), monocytes (ED-1), and laminin (neovascular channels) was performed or the thrombus was separated from the IVC and assayed for keratinocyte cytokine (KC), monocyte chemotactic protein-1 (MCP-1), bFGF with enzyme-linked immunosorbent assay (ELISA), and total collagen with a direct colorimetric assay.

RESULTS

Peripheral blood and intrathrombus PMNs and monocytes were not significantly different in the treated or control rats. There were no differences in any measure at 4 days. At 8 days, thrombus neovascularity, but not weight or collagen content, was increased in rats treated with bFGF or ENA-78 compared with control rats (17.6 +/- 0.93, 16.2 +/- 0.97 vs 13.2 +/- 0.79; channels/5 high-power fields (hpf; n = 6-10; P <.05). Post DVT IVC blood flow was significantly increased in bFGF-treated rats but not in rats treated with IP-10 or ENA-78, as compared with control rats. Rats treated with ENA-78 had increased intrathrombus bFGF compared with control rats (85 +/- 27 pg/mg protein vs 20 +/- 6 pg/mg protein; n = 6; P <.05), but other mediators were not significantly different in treated rats compared with control rats.

CONCLUSION

Pro-angiogenic compounds increase thrombus neovascularization, but this does not correlate with smaller or less fibrotic DVT. Mechanisms other than neovascularization may be more important to hasten DVT dissolution. Clinical relevance Improved therapy for deep venous thrombosis (DVT) will ideally increase the rate of thrombus dissolution and eliminate the bleeding risks of anticoagulation. This study evaluated promoting DVT neovascularization with angiogenic chemokines, and, while successful by experimental measures, this did not translate into smaller DVT. Solely promoting thrombus neovascularization will not likely speed resolution.

Microvascular remodeling and accelerated hyperemia blood flow restoration in arterially occluded skeletal muscle exposed to ultrasonic microbubble destruction

We showed previously that microbubble destruction with pulsed 1-MHz ultrasound creates a bioeffect that stimulates arteriogenesis and a chronic increase in hyperemia blood flow in normal rat muscle. Here we tested whether ultrasonic microbubble destruction can be used to create a microvascular remodeling response that restores hyperemia blood flow to rat skeletal muscle affected by arterial occlusion. Pulsed ultrasound (1 MHz) was applied to gracilis muscles in which the lateral feed artery was occluded but the medial feed artery was left intact. Control muscles were similarly occluded but did not receive ultrasound, microbubbles, or both. Hyperemia blood flow and number of smooth muscle (SM) alpha-actin-positive vessels, >30-mum arterioles, and capillaries per fiber were determined 7, 14, and 28 days after treatment. In ultrasound-microbubble-treated muscles, lateral region hyperemia blood flow was increased at all time points and restored to normal at day 28. The number of SM alpha-actin vessels per fiber was increased over control in this region at days 7 and 14 but decreased by day 28, when larger-diameter arterioles became more prevalent in the medial region. The number of capillaries per fiber was increased over control only at day 7 in the lateral region and only at days 7 and 14 in the medial region, indicating that the angiogenesis response was transient and likely did not contribute significantly to flow restoration at day 28. We conclude that ultrasonic microbubble destruction can be tailored to stimulate an arteriogenesis response that restores hyperemia blood flow to skeletal muscle in a rat model of arterial occlusion.

Therapeutic Angiogenesis in Peripheral Arterial Disease: Can Biotechnology Produce an Effective Collateral Circulation?

The physiological processes of angiogenesis, vasculogenesis and arteriogenesis contribute to the growth of collateral vessels in response to obstructive arterial disease causing lower limb or myocardial ischaemia, but in clinical practice the endogenous angiogenic response is often suboptimal or impaired, e.g. by factors such as ageing, diabetes or drug therapies. Therapeutic angiogenesis is an application of biotechnology to stimulate new vessel formation via local administration of pro-angiogenic growth factors in the form of recombinant protein or gene therapy, or by implantation of endothelial progenitor cells that will synthesize multiple angiogenic cytokines. Numerous experimental and clinical studies have sought to establish 'proof of concept' for therapeutic angiogenesis in PAD and myocardial ischaemia using different treatment modalities, but the results have been inconsistent. This review summarises the mechanisms of angiogenesis and the results of recent trials evaluating the efficacy and safety of different gene therapy, recombinant protein and cellular-based treatment approaches to enhance collateral vessel formation.

Using gene expression profiling to identify the molecular basis of the synergistic actions of hepatocyte growth factor and vascular endothelial growth factor in human endothelial cells

Hepatocyte growth factor (HGF) and vascular endothelial cell growth factor (VEGF) are two potent endothelial mitogens with demonstrated angiogenic activities in animal models of therapeutic angiogenesis. Several recent studies suggest that these growth factors may act synergistically, although the mechanism of this interaction is not understood. Changes in the gene expression profile of human umbilical vein endothelial cells treated with HGF, VEGF or the combination of the two were analyzed with high-density oligonucleotide arrays, representing approximately 22000 genes. Notably, the genes significantly up- and downregulated by VEGF versus HGF exhibited very little overlap, indicating distinct signal transduction pathways. The combination of HGF and VEGF markedly increased the number of significantly up- and downregulated genes. At 4 h, the combination of the two growth factors induced a number of chemokine and cytokines and their receptors (IL-8, IL-6, IL-11, CCR6, CXCR1,CXC1 and IL17RC), numerous genes involved in growth factor signal transduction (egr-1, fosB, grb10, grb14,MAP2K3,MAP3K8, MAPKAP2,MPK3, DUSP4 and DUSP6), as well as a number of other growth factors (PDGFA, BMP2, Hb-EGF, FGF16, heuregulin beta 1, c-kit ligand, angiopoietin 2 and angiopoietin 4 and VEGFC). In addition, the VEGF receptors neuropilin-1 and flt-1 were also upregulated. At 24 h, a clear 'cell cycle' signature is noted, with the upregulated expression of various cell cycle control proteins and gene involved in the regulation of mitosis and mitotic spindle assembly. The receptor for HGF, c-met, is also upregulated. These data are consistent with the hypothesis that the combination of HGF and VEGF results in the cooperative upregulation of a number of different molecular pathways leading to a more robust proliferative response, that is, growth factor(s), receptors, molecules involved in growth factor signal transduction, as well as, at later time points, upregulation of the necessary cellular proteins required for cells to escape cell cycle arrest and enter the cell cycle.

Abnormal angiogenesis in diabetes mellitus

The adverse long-term effects of diabetes mellitus have been well described and involve many organ systems. While diabetes management has largely focused on control of hyperglycemia, the presence of abnormalities of angiogenesis may cause or contribute to many of the clinical manifestations of diabetes. When compared with non-diabetic subjects, diabetics demonstrate vascular abnormalities of the retina, kidneys, and fetus. Diabetics have impaired wound healing, increased risk of rejection of transplanted organs, and impaired formation of coronary collaterals. In each of these conditions, and possibly in diabetic neuropathy as well, abnormalities of angiogenesis can be implicated in the pathogenesis. A perplexing feature of the aberrant angiogenesis is that excessive and insufficient angiogenesis can occur in different organs in the same individual. In this review, the clinical features, molecular mechanisms, and potential therapeutic options of abnormal angiogenesis in diabetes will be reviewed.

Autologous bone marrow cell implantation as therapeutic angiogenesis for ischemic hindlimb in diabetic rat model

The angiogenic effect induced by autologous bone marrow cell implantation (BMCI) was examined in the ischemic hindlimbs of diabetic and nondiabetic rats. Diabetes mellitus was induced by the systemic administration of streptozotocin. We investigated the production of angiogenic factors and endothelial differentiation from bone marrow cells and the native recovery of blood flow in the ischemic hindlimbs. To observe the angiogenic effect induced by BMCI treatment, 6 x 10(7) bone marrow cells were injected intramuscularly at six points into the ischemic limbs, and regional perfusion recovery was evaluated with colored microspheres 2 wk later. No difference was found between diabetic and nondiabetic rats in the release of angiogenic factors or endothelial differentiation from bone marrow cells in vitro. The levels of nitric oxide in plasma were significantly lower, and native perfusion recovery in the ischemic hindlimbs was significantly slower in the diabetic rats than in the nondiabetic rats. However, although perfusion recovery was achieved in the ischemic hindlimbs, there was no significant increase in systemic VEGF after BMCI treatment in either the diabetic or nondiabetic rats. Therefore, therapeutic angiogenesis induced by BMCI could be a safe and effective treatment for ischemic limb disease in diabetic patients.

Therapeutic angiogenesis for critical limb ischemia: invited commentary

Lower extremity arterial occlusive disease results in tissue ischemia of the legs and is relatively common in the elderly. Clinically, it may be asymptomatic, cause muscle pain during exercise, or progress to a severe degree of ischemia that may result in limb loss. Although bypass surgery and angioplasty have increased the rate of limb salvage in these patients, amputation of the affected limb remains a common outcome for many patients. Therapeutic angiogenesis is the administration of angiogenic factors, or genes encoding these factors, to promote neovascularization and thereby increase blood flow to the ischemic leg. We have developed an animal model of hindlimb ischemia in which to study therapeutic angiogenesis. We chose nitric oxide as the angiogenic factor for our experiments because of its ability to induce angiogenesis, vasodilation, and inhibit inflammation. In this review, we will discuss our experience with our model of hindlimb ischemia, as well as discuss our results of gene therapy for therapeutic angiogenesis using nitric oxide.

Functional outcome of new blood vessel growth into ischemic skeletal muscle

PURPOSE

The administration of angiogenic growth factors and the transfer of well-vascularized tissues have been shown to induce development of new blood vessels in ischemic muscle. The functional significance of these new vessels is unknown. The hypothesis of this study is that the transfer of vascularized muscle and the local infusion of basic fibroblast growth factor (bFGF) synergistically improve contractile function of ischemic skeletal muscle.

METHODS

Twenty-six rabbits were divided into four groups. An ischemic hindlimb was created in each by ligating the right common iliac artery. The flap + bFGF group (n = 6) had transposition of a contralateral rectus muscle flap onto the thigh. Additionally, bFGF (3 ng/h) was continuously infused at the flap-thigh interface. In the flap group (n = 6), a similar muscle flap was created, but carrier solution was infused at the interface. In the bFGF group (n = 6), no muscle flap was created; instead, bFGF (3 ng/h) was infused into the external iliac artery of the ischemic limb. In the control group (n = 8), carrier solution was infused into the external iliac artery (no flap, no bFGF). After 1 week, the soleus muscle was isolated and stimulated. Maximum twitch tension, the fatigue index (force of contraction after 2 minutes of continuous stimulation/initial force of contraction), maximum recovery, and the number of limbs recovered (ie, limbs that achieve a force of contraction during the recovery period of > 75% of the force of the initial contraction at the start of continuous stimulation) were recorded. Blood vessel density (number of vessels per ***) was determined by immunostaining the soleus muscle with anti-alpha-actin antibody.

RESULTS

All values were indexed to the contralateral normal limb. The flap + bFGF group showed significant improvement versus the control group in maximum twitch tension (1.07 +/- 0.13 vs 0.63 +/- 0.12, P < .05), maximum recovery (0.94 +/- 0.05 vs 0.58 +/- 0.05, P < .05), and the number of limbs recovered (5/5 vs 0/6, P < .05). This improved function correlated with increased vessel density (flap + bFGF group, 1.44 +/- 0.11 vs control group, 0.72 +/- 0.01, P < .05).

CONCLUSION

Reperfusion of an ischemic limb with a well-vascularized muscle flap and local bFGF infusion promoted increased blood vessel density in distal ischemic muscle. This increased vascularity was associated with restoration of otherwise impaired muscle function. Improved function occurred rapidly (1 week). A transposed muscle flap provided a functional blood supply to the site of maximum ischemia; this could be used to salvage otherwise nonreconstructible ischemic limbs.

Administration of adenoviral vectors induces gangrene in acutely ischemic rat hindlimbs: role of capsid protein-induced inflammation

PURPOSE

The initial purpose of this study was to determine the effects of intravascular adenoviral vector-mediated gene transfer of endothelial nitric oxide synthase (AdeNOS) on experimental hindlimb ischemia in the rat. Unexpectedly, administration of AdeNOS immediately after induction of acute limb ischemia led to limb gangrene. We subsequently sought to define the molecular mechanisms responsible for this unusual effect and to devise adenoviral gene transfer strategies to prevent the development of gangrene in acutely ischemic limbs.

METHODS

Phosphate-buffered saline or adenoviral vectors containing the bovine endothelial nitric oxide synthase gene (AdeNOS) or no transgene (Ad-E1) were injected intra-arterially into the hindlimb of a rat under vascular isolation immediately after surgical induction of severe ischemia. Hematoxylin and eosin staining was performed on muscle sections to evaluate inflammation. A separate group of animals was injected with an adenovirus containing a nontranscribable genome, treated with cyclosporine, or received delayed administration of the adenoviral vector. Gene expression after delayed adenoviral gene transfer was assessed with immunohistochemistry, Western blotting, and nitric oxide synthase (NOS) activity assay.

RESULTS

Both AdeNOS and Ad-E1 caused gangrene of the entire hindlimb within 12 days in a dose-dependent manner, at a threshold concentration of 1 x 10(9) plaque-forming unit/mL. Adenoviral delivery was associated with more inflammation and edema compared with phosphate-buffered saline histologically. Inactivation of adenoviral DNA transcription did not affect induction of gangrene. However, gangrene was prevented by concurrent immunosuppression with cyclosporine or delayed administration of the vector. Delayed administration allowed adenoviral gene expression as determined by immunohistochemistry, NOS protein levels, and an assay of NOS enzyme activity.

CONCLUSION

Intra-arterial administration of adenoviral vectors, under vascular isolation, immediately after induction of acute ischemia causes inflammation and subsequent limb gangrene. The inflammatory response is unrelated to the expression of the recombinant transgene or the adenoviral genome and is likely due to the adenoviral capsid proteins. However, administration of cyclosporine or delayed injection of the adenoviral vector is a method that can be used for adenoviral mediated gene transfer in limb ischemia.

Gene therapy for therapeutic angiogenesis in critically ischaemic lower limb - on the way to the clinic

Currently, no effective pharmacological treatment is available for vascularisation defects in lower limbs. Many patients presenting with persistent pain and ischaemic ulcers are not suitable candidates for surgical or endovascular approaches. Further refinement of the available methods will undoubtedly lead to a more active approach towards treatment of peripheral arterial occlusive disease (PAOD). Recently, therapeutic angiogenesis, in the form of recombinant growth factor administration or gene therapy, has emerged as a novel tool to treat these patients. However, improved gene transfer methods and better understanding of blood vessel formation are required to bring therapeutic angiogenesis to clinical practice. Here we review the clinical problem (PAOD), mechanisms of blood vessel formation (angiogenesis, vasculogenesis and arteriogenesis), experimental evidence and clinical trials for therapeutic angiogenesis in critically ischaemic lower limbs. Also, angiogenic growth factors, including vascular endothelial growth factors (VEGFs) and fibroblast growth factors (FGFs), delivery methods, and vectors for gene transfer in skeletal muscle, are discussed. In addition to vascular growth, gene transfer of growth factors may enhance regeneration, survival, and innervation of ischaemic skeletal muscle. Nitric oxide (NO) appears to be a key mediator in vascular homeostasis and growth, and a reduction in its production by age, hypercholesterolemia or diabetes leads to the impairment of ischaemic disorders.