Long-term follow-up evaluation of results from clinical trial using hepatocyte growth factor gene to treat severe peripheral arterial disease

Comparative Analysis of Transcriptome Profiles in Patients with Thromboangiitis Obliterans

BACKGROUND

Thromboangiitis obliterans (TAO) causes vascular insufficiency due to chronic inflammation and abrupt thrombosis of the medium and small arteries of the extremities. In our study, we aimed to determine biomarkers for the diagnosis of TAO by evaluating 15 male TAO patients with Shinoya diagnostic criteria and 5 healthy controls who did not have TAO-related symptoms in their family histories.

METHODS

The Clariom D Affymetrix platform was used to conduct microarray analysis on total RNA extracted from whole blood. A total of 477 genes (FC ≤ 5 or >5) common to the fifteen patient and five control samples were selected using comparative microarray analysis; among them, 79 genes were upregulated and 398 genes were downregulated.

RESULTS

According to FC ≤ 10 or >10, in the same TAO patient and control group, 13 genes out of 28 were upregulated, whereas 15 genes were downregulated. The 11 key genes identified according to their mean log2FC values were PLP2, RPL27A, CCL4, FMNL1, EGR1, EIF4A1, RPL9, LAMP2, RNF149, EIF4G2, and DGKZ. The genes were ranked according to their relative expression as follows: FMNL1 > RNF149 > RPL27A > EIF4G2 > EIF4A1 > LAMP2 > EGR1 > PLP2 > DGKZ > RPL9 > CCL4. Using protein-protein interaction network analysis, RPL9, RPL27A, and RPL32 were found to be closely related to EIF4G2 and EIF4A1. The Reactome pathway found pathways linked to 28 genes. These pathways included the immune system, cellular responses to stress, cytokine signaling in the immune system, and signaling by ROBO receptors.

CONCLUSIONS

By figuring out the protein expression levels of the genes that have been found to explain how TAO disease works at the molecular level, it will be possible to figure out how well these chosen transcripts can diagnose and predict the disease.

Therapeutic angiogenesis in Buerger's disease: reviewing the treatment landscape

Thromboangiitis obliterans, also known as Buerger's disease, is a rare inflammatory vasculitis that predominantly develops in smokers and characteristically affects the small- and medium-sized peripheral arteries and veins. Patients typically present with extremity claudication, but symptoms may progress to rest pain and tissue loss, especially in those unable to abstain from tobacco use. Unfortunately, traditional medical treatments are largely ineffective and due to the small caliber of affected vessels and lack of suitable distal targets or venous conduits, endovascular and open surgical approaches are often not possible. Eventually, a significant number of patients require major amputation. For these reasons, much research effort has been made in developing techniques of therapeutic angiogenesis to improve limb perfusion, both for atherosclerotic peripheral arterial disease and the smaller subset of patients with critical limb ischemia due to Buerger's disease. Neovascularization in response to ischemia relies on a complex interplay between the local tissue microenvironment and circulating stem and progenitor cells. To date, studies of therapeutic angiogenesis have therefore focused on exploiting known angiogenic factors and stem cells to induce neovascularization in ischemic tissues. This review summarizes the available clinical data regarding the safety and efficacy of various angiogenic therapies, notably injection of naked DNA plasmids, viral gene constructs, and cell-based preparations, and describes techniques for potentiating in vivo efficacy of gene- and cell-based therapies as well as ongoing developments in exosome-based cell-free approaches for therapeutic angiogenesis.

Plain Language Title and Summary

A review of available and emerging treatments for improving blood flow and wound healing in patients with Buerger's disease, a rare disorder of blood vessels Buerger's disease is a rare disorder of the small- and medium-sized blood vessels in the arms and legs that almost exclusively develops in young smokers. Buerger's disease causes inflammation in arteries and veins, which leads to blockage of these vessels and reduces blood flow to and from the extremities. Decreased blood flow to the arms and legs can lead to development of nonhealing wounds and infection for which some patients may eventually require amputation. Unfortunately, traditional medical and surgical treatments are not effective in Buerger's disease, so other methods for improving blood flow are needed for these patients. There are several different ways to stimulate new blood vessel formation, both in humans and animal models. The most common treatments involve injection of DNA or viruses that express genes related to blood vessel formation or, alternatively, stem cell-based treatments that help regenerate blood vessels and repair wound tissue. This review explores how safe and effective these various treatments are and describes recent research developments that may lead to better therapies for patients with Buerger's disease and other vascular disorders.

Combined Analysis of Clinical Data on HGF Gene Therapy to Treat Critical Limb Ischemia in Japan

OBJECTIVE

The objective of this combined analysis of data from clinical trials in Japan, using naked plasmid DNA encoding hepatocyte growth factor (HGF), was to document the safety and efficacy of intramuscular HGF gene therapy in patients with critical limb ischemia (CLI).

METHODS

HGF gene transfer was performed in 22 patients with CLI in a single-center open trial at Osaka University; 39 patients in a randomized, placebo-controlled, multi-center phase III trial, 10 patients with Buerger's disease in a multi-center open trial; and 6 patients with CLI in a multi-center open trial using 2 or 3 intramuscular injections of naked HGF plasmid at 2 or 4 mg. Resting pain on a visual analogue scale (VAS) and wound healing as primary endpoints were evaluated at 12 weeks after the initial injection. Serious adverse events caused by gene transfer were detected in 7 out of 77 patients (9.09%). Only one patient experienced peripheral edema (1.30%), in contrast to those who had undergone treatment with VEGF. At 12 weeks after gene transfer, combined evaluation of VAS and ischemic ulcer size demonstrated a significant improvement in HGF gene therapy group as compared to the placebo group (P=0.020).

RESULTS

The long-term analysis revealed a sustained decrease in the size of ischemic ulcer in HGF gene therapy group. In addition, VAS score over 50 mm at baseline (total 27 patients) demonstrated a tendency (P=0.059), but not significant enough, to improve VAS score in HGF gene therapy as compared to the placebo group.

CONCLUSION

The findings indicated that intramuscular injection of naked HGF plasmid tended to improve the resting pain and significantly decreased the size of the ischemic ulcer in the patients with CLI who did not have any alternative therapy, such as endovascular treatment (EVT) or bypass graft surgery. An HGF gene therapy product, CollategeneTM, was recently launched with conditional and time-limited approval in Japan to treat ischemic ulcer in patients with CLI. Further clinical trials would provide new therapeutic options for patients with CLI.

Gene therapy for critical limb ischemia: Per aspera ad astra

Peripheral artery diseases remain a serious public health problem. Although there are many traditional methods for their treatment using conservative therapeutic techniques and surgery, gene therapy is an alternative and potentially more effective treatment option especially for "no option" patients. This review treats the results of many years of research and application of gene therapy as an example of treatment of patients with critical limb ischemia. Data on successful and unsuccessful attempts to use this technology for treating this disease are presented. Trends in changing the paradigm of approaches to therapeutic angiogenesis are noted: from viral vectors to non-viral vectors, from gene transfer to the whole organism to targeted transfer to cells and tissues, from single gene use to combination of genes; from DNA therapy to RNA therapy, from in vivo therapy to ex vivo therapy.

pUDK-HGF Gene Therapy to Relieve CLI Rest Pain and Ulcer: A Phase II, Double-Blind, Randomized Placebo-Controlled Trial

This phase II clinical trial investigated the efficacy and safety of intramuscular injection of plasmid pUDK-HGF, which encodes the human hepatocyte growth factor gene in patients with critical limb ischemia. Resting pain patients (n = 119) and patients with leg ulcers (n = 121) were enrolled as two cohorts and randomized to receive pUDK-HGF treatment on days 0, 14, and 28. In the resting pain cohort, the proportion of patients with complete pain relief on day 180 after receiving pUDK-HGF injection, as the primary outcome, was significantly higher than that of the placebo group on the same day (p = 0.0148). More responders with >50% pain reduction were also observed in the pUDK-HGF groups than in the placebo groups (p = 0.0168). In the ulcer cohort of patients, pUDK-HGF treatment tended to be superior to the placebo in the percentage of patients with both complete ulcer healing and >50% ulcer healing. No significant differences in the incidence of adverse events (AEs) or serious AEs were observed among the groups. The mid-dose pUDK-HGF (6 mg) was the most efficacious, and is therefore an appropriate dose for use in a phase III clinical trial. This study was approved by the China Food and Drug Administration (2013L00637), China Clinical Trial Registry URL: www.chinadrugtrials.org.cn. Unique Identifier: 20130378.

Progress of Gene Therapy in Cardiovascular Disease

Gene therapy has been extensively studied in peripheral and cardiac ischemia, heart and vein graft failure, and dyslipidemia, but most clinical trials failed to show their efficacies despite good outcomes in preclinical studies. So far, 2 gene therapies for dyslipidemia and one for critical limb ischemia in peripheral artery disease have been approved. In critical limb ischemia, gene therapy using proangiogenic factors has emerged as a novel therapeutic modality for promoting angiogenesis. Initial researches mainly focused on vascular endothelial growth factor, fibroblast growth factor, or hepatocyte growth factor. After the favorable results of basic research, several phase I and II clinical trials of these proangiogenic factors have shown promising results. However, only a phase III clinical trial of the intramuscular injection of hepatocyte growth factor plasmid DNA has shown successful outcomes, and it was recently approved in Japan for treating patients with critical limb ischemia who have ulcers and for whom no alternative therapeutic options are available. DNA vaccine is another promising modality of gene therapy. An antitumor vaccine suppressing angiogenesis through the inhibition of proangiogenic factors and an antihypertensive vaccine inhibiting the renin–angiotensin system are representative DNA vaccines. The advantage of DNA vaccine is its long-term effectiveness with a few vaccinations; however, the benefits and risks, such as adverse T-cell reaction against self-antigen or long-term side effects, of DNA vaccines should be carefully evaluated. In this review, we discuss the recent advances in proangiogenic gene therapy for critical limb ischemia and DNA vaccine for hypertension.

Double VEGF/HGF Gene Therapy in Critical Limb Ischemia Complicated by Diabetes Mellitus

Critical leg ischemia (CLI) complicated by diabetes mellitus (DM), which is a very common and dangerous disease, represents the ultimate stage of peripheral arterial disease. Patients are treated with antiplatelet drugs, statins and limb revascularization, but a significant number of patients are not candidate for revascularization. Literature shows that in such cases, gene therapy could be a perfect therapeutic option. The aim of our study was to evaluate efficacy of double vascular endothelial growth factor/hepatocyte growth factor (VEGF/HGF) gene therapy in patients with CLI complicated by DM. We observed that 90 days after administration, serum level of VEGF and ankle-brachial index increased significantly (p < 0.001) and rest pain decreased significantly compared with the control group (p < 0.002). Moreover considerable improvement in vascularization was observed in computed tomography angiography (P = 0.04). Based on the results of this study, we suggest that the therapy with pIRES/VEGF165/HGF bicistronic plasmid administration is a safe and effective method of treatment of patients with both CLI and DM. Graphical abstract.

Therapeutic Angiogenesis Using HGF Plasmid

Hepatocyte growth factor (HGF) is secreted from stromal and mesenchymal cells, and its receptor cMet is expressed on various types of cells such as smooth muscle cells, fibroblast, and endothelial cells. HGF stimulates epithelial and endothelial cell proliferation, motility, and morphogenesis in a paracrine and autocrine manner, organizing multistep of angiogenesis in many organs. In addition, HGF is recognized as a potent anti-inflammatory and anti-fibrotic growth factor, which has been proved in several animal studies, including neointimal hyperplasia and acute myocardial infarction model in rodent. Thus, as compared to other angiogenic growth factors, HGF exerts multiple effects on ischemic tissues, accompanied by the regression of tissue inflammation and fibrosis. These data suggest the therapeutic potential of the HGF for peripheral artery disease as it being accompanied with chronic tissue inflammation and fibrosis. In the present narrative review, the pleiotropic action of the HGF that differentiates it from other angiogenic growth factors is discussed first, and later, outcomes of the human clinical study with gene therapy are overviewed.

Association of Circulating Hepatocyte Growth Factor and Risk of Incident Peripheral Artery Disease: The Multi-Ethnic Study of Atherosclerosis

Higher levels of hepatocyte growth factor (HGF) have been associated with the presence of peripheral arterial disease (PAD), but prospective associations are unknown. We examined the association of circulating HGF levels with incident PAD. Between 2000 and 2002, HGF was measured in 6742 Multi-Ethnic Study of Atherosclerosis participants without PAD. Incident clinical PAD, adjudicated on the basis of a positive history for the presence of disease-related symptoms or treatment, was ascertained through 2015. Incident low ankle-brachial index (ABI), defined as an ABI < 0.9 and a decline of ≥ 0.15, was assessed among 5736 individuals who had an ABI > 0.9 at baseline and ≥1 follow-up ABI measurement 3 to 10 years later. There were 116 clinical PAD and 197 low ABI events that occurred over a median follow-up of 14 and 9 years, respectively. After adjustment for demographic and clinical variables, a standard deviation increment of HGF (303 ng/L) was associated with an increased risk of clinical PAD (hazard ratio: 1.21; 95% confidence interval [CI]: 1.05-1.39) but not a low ABI (rate ratio: 1.03; 95% CI: 0.85-1.25). In conclusion, higher HGF levels were modestly associated with an increased risk of developing clinical PAD.

Long-term follow-up and safety assessment of angiogenic gene therapy trial VIF-CAD: Transcatheter intramyocardial administration of a bicistronic plasmid expressing VEGF-A165/bFGF cDNA for the treatment of refractory coronary artery disease

There have been a number of angiogenic gene therapy trials, yielding mixed results as to efficacy, but demonstrating uniform short-term treatment safety. Data regarding long-term safety of angiogenic gene therapy are limited. Double-blind VIF-CAD trial (NCT00620217) assessed myocardial perfusion and clinical data in 52 refractory coronary artery disease (CAD) patients randomized into treatment (VIF; n = 33) and Placebo (n = 19) arms. VIF group received electromechanical system NOGA-guided intramyocardial injections of VEGF-A165/bFGF plasmid (VIF) into ischemic regions, while the Placebo group-placebo plasmid injections. Full 1-year follow-up data have been published. This study presents the results of over 10-year (median 133 months, range 95-149) safety follow-up of VIF-CAD patients. Overall, 12 (36.4%) patients died in VIF and 8 (42.1%) in Placebo group (P = .68). Cardiovascular mortality was 12/33 (36.4%) in the VIF group and 6/19 (31.6%) in Placebo group (P = .73). Two Placebo patients died due to malignancies, but no VIF patients (P = .17). The Kaplan-Meier curves of combined endpoint: cardiovascular mortality, myocardial infarction and stroke were similar for both patient groups (P = .71). Odds ratio of Placebo group increasing (reaching a worse) their CCS class versus VIF was non-significant (OR 1.28, 95% CI = 0.66-2.45; P = .47). However, CCS class improved in time irrespectively of treatment-OR of reaching a less favorable CCS class per each year of follow-up was 0.74 (95% CI 0.685-0.792; P < .0001, pooled data). There were no differences in readmission rates. Intramyocardial VEGF-A165/bFGF plasmid administration appears safe, with no evidence of an increase in the incidence of death, malignancy, myocardial infarction or stroke during 10-year follow-up in this limited patient population.

Plasmid DNA Mono-Ion Complex for in Vivo Sustainable Gene Expression

To cleave biocompatible poly(ethylene glycol) (PEG) from the mono-ion complex (MIC) for sustainable cellular uptake in vivo, ω-amide-pentylimidazolium end-modified PEG with an ester bond, that is, APe-Im-E-PEG, has been synthesized. The hydrolysis of the resulting APe-Im-E-PEG proceeded during the incubation for 2 weeks under physiological conditions, which was confirmed by gel filtration chromatography. APe-Im-E-PEG formed the MIC with plasmid DNA (pDNA), assessed by agarose gel retardation assay. Furthermore, dynamic light scattering measurement and transmission electron microscopy observations have estimated that the particle size of the resulting MIC was approximately 30 nm, with a rather flexible structure. The APe-Im-E-PEG/pDNA MIC incubated for 2 weeks exhibited hemolytic activity at endosomal pH, presumably because the pH-sensitive carboxyl groups revealed after the hydrolysis of an ester bond of APe-Im-E-PEG. The APe-Im-E-PEG/pDNA MIC enhanced the gene expression 2 weeks after transfection in vivo by intramuscular administration in mice. Consequently, in vivo sustainable gene expression has been achieved by the molecular design of APe-Im-E-PEG for cellular uptake and endosomal escape proceeded by temporal hydrolysis of the ester bond.

Treatment of Critical Limb Ischemia by pIRES/VEGF165/HGF Administration

BACKGROUND

Prognosis of peripheral artery disease (PAD), especially critical limb ischemia (CLI), is very poor despite the development of endovascular therapy and bypass surgery. Many patients result in having leg amputation. We decided to investigate the safety and efficacy of plasmid of internal ribosome entry site/vascular endothelial growth factor (VEGF) 165/hepatocyte growth factor (HGF) gene therapy (GT) in patients suffered from CLI.

METHODS

Administration of plasmid of internal ribosome entry site/VEGF165/HGF was performed in 12 limbs of 12 patients with rest pain and ischemic ulcers due to CLI. Plasmid was injected into the muscles of the ischemic limbs. The levels of VEGF in serum and the ankle-brachial index (ABI) were measured before and after treatment.

RESULTS

Mean (±SD) plasma levels of VEGF increased nonsignificantly from 258 ± 81 pg/L to 489 ± 96 pg/L (P > 0.05) 2 weeks after therapy, and the ABI improved significantly from 0.27 ± 0.20 to 0.50 ± 0.22 (P < 0.001) 3 months after therapy. Ischemic ulcers healed in 9 limbs. Amputation was performed in 3 patients because of advanced necrosis and wound infection. However, the level of amputations was lowered below knee in these cases. Complications were limited to transient leg edema in 3 patients and fever in 2 patients.

CONCLUSIONS

Intramuscular administration of plasmid of internal ribosome entry site/VEGF165/HGF is safe, feasible, and effective for patients with critical leg ischemia.

Isolation of tissue-resident endothelial stem cells and their use in regenerative medicine

Background

During sprouting angiogenesis, stalk cells, localized behind tip cells, generate endothelial cells (ECs) for the elongation of new vessels. We hypothesized that stalk cells may have endothelial progenitor cell properties because of their highly proliferative ability. We conducted Hoechst dye DNA staining in ECs of preexisting blood vessels from hind limb muscle and found that endothelial-side population (E-SP) cells, which efflux Hoechst rapidly with abundant ABC transporters, show highly producing ability of ECs. We previously showed the existence of E-SP cells in hind limb muscle, retina, and liver, but not in other tissues such as adipose tissue, skin, and placenta.

Methods

We investigated the existence of E-SP cells and analyzed their proliferative ability among CD31⁺CD45⁻ ECs from adipose tissue, skin, and placenta of adult mice. We also analyzed the neovascular formation of E-SP cells from adipose tissue in vivo.

Results

We detected E-SP cells in all tissues examined. However, by in vitro colony formation analysis on OP9 cells, we found that E-SP cells from adipose tissue and skin, but not from placenta, have highly proliferative ability. Moreover, E-SP cells from adipose tissue could contribute to the neovascular formation in hind limb ischemia model.

Conclusion

The adipose tissue and skin are available sources to obtain endothelial stem cells for conducting therapeutic angiogenesis in regenerative medicine.

Non-viral Vector for Muscle-Mediated Gene Therapy

Non-viral gene delivery to skeletal muscle was one of the first applications of gene therapy that went into the clinic, mainly because skeletal muscle is an easily accessible tissue for local gene transfer and non-viral vectors have a relatively safe and low immunogenic track record. However, plasmid DNA, naked or complexed to the various chemistries, turn out to be moderately efficient in humans when injected locally and very inefficient (and very toxic in some cases) when injected systemically. A number of clinical applications have been initiated however, based on transgenes that were adapted to good local impact and/or to a wide physiological outcome (i.e., strong humoral and cellular immune responses following the introduction of DNA vaccines). Neuromuscular diseases seem more challenging for non-viral vectors. Nevertheless, the local production of therapeutic proteins that may act distantly from the injected site and/or the hydrodynamic perfusion of safe plasmids remains a viable basis for the non-viral gene therapy of muscle disorders, cachexia, as well as peripheral neuropathies.

Evolution of Periodontal Disease: Immune Response and RANK/RANKL/OPG System

The aim of this study was to evaluate markers of bone loss and immune response present in evolution of periodontal disease. One hundred and two Wistar rats were divided into three animals groups: PD0, without ligation and PD15 days and PD60 days, submitted to ligation placement with a sterile 3-0 silk cord in the cervical region of the upper first molar on both sides. Samples were obtained from the gingival tissue for histomorphometric analysis, immunohistochemical analysis of RANK, RANKL, OPG, characterization of the inflammatory infiltrate, quantification of nitric oxide, MCP-1, RANTES, IP10 chemokines, and expression of the TGF-b1, VEG, and bFGF. The number of inflammatory cells in gingival tissue was higher in PD60 samples. The collagen content and the area occupied by birefringent collagen fibers were lower for PD60. Differential leukocyte counting showed that there was a significantly higher polymorphonuclear influx in group PD15, while PD60 showed a greater number of lymphocytes. PD60 showed higher RANTES, IP-10, MCP-1 gene transcripts, as well as a higher nitric oxide concentration. Clinical evaluation revealed that the PD60 group presented an increase in furcal area. In conclusion, in this animal model the increase of RANK/RANKL and HGF markers is related to a specific immune response, and probably contributed to the evolution of periodontal disease. Investigating the effect of these biomarkers can help in targeted therapy for bone resorption, since blocking these can inhibit bone loss.

Correlation between increasing tissue ischemia and circulating levels of angiogenic growth factors in peripheral artery disease

INTRODUCTION

The aim of the present study was to assess the circulating levels of vascular endothelial growth factor (VEGF) and other suggested therapeutic growth factors with the degree of ischemia in patients with different clinical manifestations of peripheral arterial disease (PAD) according to the Rutherford grades.

METHODS

The study cohort consists of 226 consecutive patients admitted to a Department of Vascular Surgery for elective invasive procedures. PAD patients were grouped according to the Rutherford grades after a clinical assessment. Ankle-brachial pressure indices (ABI) and absolute toe pressure (TP) values were measured. Serum levels of circulating VEGF, hepatocyte growth factor (HGF), basic fibroblast growth factor (bFGF), and platelet derived growth factor (PDGF) were measured from serum and analysed against Rutherford grades and peripheral hemodynamic measurements.

RESULTS

The levels of VEGF (P = 0.009) and HGF (P < 0.001) increased significantly as the ischaemic burden became more severe according to the Rutherford grades. PDGF behaved in opposite manner and declined along increasing Rutherford grades (P = 0.004). A significant, inverse correlations between Rutherford grades was detected as follows; VEGF (Pearson's correlation = 0.183, P = 0.004), HGF (Pearson's correlation = 0.253, P < 0.001), bFGF (Pearson's correlation = 0.169, P = 0.008) and PDGF (Pearson's correlation = 0.296, P < 0.001). In addition, VEGF had a clear direct negative correlation with ABI (Pearson's correlation -0.19, P = 0.009) and TP (Pearson's correlation -0.20, P = 0.005) measurements.

CONCLUSIONS

Our present observations show that the circulating levels of VEGF and other suggested therapeutic growth factors are significantly increased along with increasing ischemia. These findings present a new perspective to anticipated positive effects of gene therapies utilizing VEGF, HGF, and bFGF, because the levels of these growth factors are endogenously high in end-stage PAD.

Gene-Therapeutic Strategies Targeting Angiogenesis in Peripheral Artery Disease

The World Health Organization announced that cardiovascular disease is the number one cause of death globally, representing 31% of all global deaths. Coronary artery disease (CAD) affects approximately 5% of the US population aged 40 years and older. With an age-adjusted prevalence of approximately 12%, peripheral artery disease (PAD) affects at least 8 to 12 million Americans. Both CAD and PAD are caused by mainly atherosclerosis, the hardening and narrowing of arteries over the years by lipid deposition in the vascular bed. Despite the significant advances in interventions for revascularization and intensive medical care, patients with CAD or PAD who undergo percutaneous transluminal angioplasty have a persistent high rate of myocardial infarction, amputation, and death. Therefore, new therapeutic strategies are urgently needed for these patients. To overcome this unmet need, therapeutic angiogenesis using angiogenic growth factors has evolved in an attempt to stimulate the growth of new vasculature to compensate for tissue ischemia. After nearly 20 years of investigation, there is growing evidence of successful or unsuccessful gene therapy for ischemic heart and limb disease. This review will discuss basic and clinical data of therapeutic angiogenesis studies employing angiogenic growth factors for PAD patients and will draw conclusions on the basis of our current understanding of the biological processes of new vascularization.

Angiogenesis in peripheral arterial disease

Peripheral arterial disease (PAD) refers to narrowing of the peripheral arteries and atherosclerosis is the most important cause. In patients with PAD, revascularization is the preferred therapeutic strategy; nonetheless several patients are not deemed candidates for it due to advanced disease or several comorbidities. The main target of therapeutic angiogenesis is to promote development of new arterial vessels and improve perfusion of ischemic tissue. Angiogenic growth factors such as vascular endothelial growth factor (VEGF), fibroblast growth factor (FGF), hepatocyte growth factor (HGF), administered intramuscularly or intra-arterially, have been shown to promote angiogenesis and development of collateral vasculature in preclinical studies. However, clinical studies failed to confirm their efficacy in ulcer healing and prevention of amputation, among patients with claudication or critical limb ischemia (CLI). Autologous progenitor cell therapy with bone marrow or adipose-derived progenitor cells administered intra-arterially or intra-muscularly, was shown to improve claudication symptoms and ankle-brachial index in small studies. However, subsequent randomized controlled studies did not demonstrate any beneficial effects of stem cell therapy on amputation rates and survival. Although, therapeutic angiogenesis remains an area of interest in PAD with several ongoing studies of investigational therapies, so far the use of these strategies in clinical practice has not been successful.

Hepatocyte Growth Factor Prevented High-Fat Diet-Induced Obesity and Improved Insulin Resistance in Mice

Obesity and its associated chronic inflammation in adipose tissue initiate insulin resistance, which is related to several pathologies including hypertension and atherosclerosis. Previous reports demonstrated that circulating hepatocyte growth factor (HGF) level was associated with obesity and type 2 diabetes. However, its precise role in obesity and related-pathology is unclear. In this experiment, cardiac-specific over-expression of human HGF in mice (HGF-Tg mice) which showed 4–5 times higher serum HGF levels than wild-type mice were used. While body weight in wild-type mice fed with high fat diet (HFD) for 14 weeks was significantly increased accompanied with insulin resistance, HGF-Tg mice prevented body weight gain and insulin resistance. The accumulation of macrophages and elevated levels of inflammatory mediators in adipose tissue were significantly inhibited in HGF-Tg mice as compared to wild-type mice. The HFD-induced obesity in wild-type mice treated with HGF-neutralizing antibody showed an exacerbated response to the glucose tolerance test. These gain-of-function and loss-of-function studies demonstrated that the elevated HGF level induced by HFD have protective role against obesity and insulin resistance.

Elevated Levels of Adhesion Proteins Are Associated With Low Ankle-Brachial Index

Inflammation plays a pivotal role in peripheral artery disease (PAD). Cellular adhesion proteins mediate the interaction of leukocytes with endothelial cells during inflammation. To determine the association of cellular adhesion molecules with ankle-brachial index (ABI) and ABI category (≤1.0 vs >1.0) in a diverse population, 15 adhesion proteins were measured in the Multi-Ethnic Study of Atherosclerosis (MESA). To assess multivariable associations of each protein with ABI and ABI category, linear and logistic regression was used, respectively. Among 2364 participants, 23 presented with poorly compressible arteries (ABI > 1.4) and were excluded and 261 had ABI ≤ 1.0. Adjusting for traditional risk factors, elevated levels of soluble P-selectin, hepatocyte growth factor, and secretory leukocyte protease inhibitor were associated with lower ABI ( P = .0004, .001, and .002, respectively). Per each standard deviation of protein, we found 26%, 20%, and 19% greater odds of lower ABI category ( P = .001, .01, and .02, respectively). Further investigation into the adhesion pathway may shed new light on biological mechanisms implicated in PAD.

Medical Therapy in Peripheral Artery Disease and Critical Limb Ischemia

OPINION STATEMENT

Peripheral artery disease (PAD) comprises atherosclerosis of the aorta and lower extremities. Many patients with PAD are asymptomatic, while others present with intermittent claudication (IC) or critical limb ischemia (CLI). Defined as rest pain or tissue loss that persists for >2 weeks, CLI represents the most severe clinical manifestation of PAD and is associated with an increased risk of limb loss and death. Patients with PAD, including those with CLI, are underdiagnosed and undertreated. In addition to smoking cessation, medical therapy with an antiplatelet agent and statin is recommended for all patients with PAD. Regular exercise has been shown to improve walking distance and quality of life in patients with symptomatic PAD and should be incorporated into each patient's treatment plan. In patients who have CLI and in those with persistent lifestyle-limiting claudication despite optimal medical therapy and an exercise program, revascularization is indicated for limb salvage and symptom relief, respectively. Consensus guidelines currently support an endovascular first approach to revascularization in the majority of cases. Surgical procedures provide an alternative to endovascular therapy in select cases.

Partial correction of the dwarf phenotype by non-viral transfer of the growth hormone gene in mice: Treatment age is critical

Non-viral transfer of the growth hormone gene to different muscles of immunodeficient dwarf (lit/scid) mice is under study with the objective of improving phenotypic correction via this particular gene therapy approach. Plasmid DNA was administered into the exposed quadriceps or non-exposed tibialis cranialis muscle of lit/scid mice followed by electroporation, monitoring several growth parameters. In a 6-month bioassay, 50μg DNA were injected three times into the quadriceps muscle of 80-day old mice. A 50% weight increase, with a catch-up growth of 21%, together with a 16% increase for nose-to-tail and tail lengths (catch-up=19-21%) and a 24-28% increase for femur length (catch-up=53-60%), were obtained. mIGF1 serum levels were ~7-fold higher than the basal levels for untreated mice, but still ~2-fold lower than in non-dwarf scid mice. Since treatment age was found to be particularly important in a second bioassay utilizing 40-day old mice, these pubertal mice were compared in a third bioassay with adult (80-day old) mice, all treated twice with 50μg DNA injected into each tibialis cranialis muscle, via a less invasive approach. mIGF1 concentrations at the same level as co-aged scid mice were obtained 15days after administration in pubertal mice. Catch-up growth, based on femur length (77%), nose-to-tail (36%) and tail length (39%) increases was 40 to 95% higher than those obtained upon treating adult mice. These data pave the way for the development of more effective pre-clinical assays in pubertal dwarf mice for the treatment of GH deficiency via plasmid-DNA muscular administration.

Novel Applications of Radionuclide Imaging in Peripheral Vascular Disease

Peripheral vascular disease (PVD) is a progressive atherosclerotic disease that leads to stenosis or occlusion of blood vessels supplying the lower extremities. Current diagnostic imaging techniques commonly focus on evaluation of anatomy or blood flow at the macrovascular level and do not permit assessment of the underlying pathophysiology associated with disease progression or treatment response. Molecular imaging with radionuclide-based approaches can offer novel insight into PVD by providing noninvasive assessment of biological processes such as angiogenesis and atherosclerosis. This article discusses emerging radionuclide-based imaging approaches that have potential clinical applications in the evaluation of PVD progression and treatment.

Endothelial sprouting and network formation in collagen- and fibrin-based modular microbeads

A modular tissue engineering approach may have advantages over current therapies in providing rapid and sustained revascularization of ischemic tissue. In this study, modular protein microbeads were prepared from pure fibrin (FIB) and collagen-fibrin composites (COL-FIB) using a simple water-in-oil emulsification technique. Human endothelial cells and fibroblasts were embedded directly in the microbead matrix. The resulting microbeads were generally spheroidal with a diameter of 100-200μm. Cell viability was high (75-80% viable) in microbeads, but was marginally lower than in bulk hydrogels of corresponding composition (85-90% viable). Cell proliferation was significantly greater in COL-FIB microbeads after two weeks in culture, compared to pure FIB microbeads. Upon embedding of microbeads in a surrounding fibrin hydrogel, endothelial cell networks formed inside the microbead matrix and extended into the surrounding matrix. The number of vessel segments, average segment length, and number of branch points was higher in FIB samples, compared to COL-FIB samples, resulting in significantly longer total vessel networks. Anastomosis of vessel networks from adjacent microbeads was also observed. These studies demonstrate that primitive vessel networks can be formed by modular protein microbeads containing embedded endothelial cells and fibroblasts. Such microbeads may find utility as prevascularized tissue modules that can be delivered minimally invasively as a therapy to restore blood flow to ischemic tissues.

STATEMENT OF SIGNIFICANCE

Vascularization is critically important for tissue engineering and regenerative medicine, and materials that support and/or promote neovascularization are of value both for translational applications and for mechanistic studies and discovery-based research. Therefore, we fabricated small modular microbeads formulated from pure fibrin (FIB) and collagen-fibrin (COL-FIB) containing endothelial cells and supportive fibroblasts. We explored how cells encapsulated within these materials form microvessel-like networks both within and outside of the microbeads when embedded in larger 3D matrices. FIB microbeads were found to initiate more extensive sprouting into the surrounding ECM in vitro. These results represent an important step towards our goal of developing injectable biomaterial modules containing preformed vascular units that can rapidly restore vascularization to an ischemic tissue in vivo.

Cellular and molecular mechanisms of HGF/Met in the cardiovascular system

Met tyrosine kinase receptor, also known as c-Met, is the HGF (hepatocyte growth factor) receptor. The HGF/Met pathway has a prominent role in cardiovascular remodelling after tissue injury. The present review provides a synopsis of the cellular and molecular mechanisms underlying the effects of HGF/Met in the heart and blood vessels. In vivo, HGF/Met function is particularly important for the protection of the heart in response to both acute and chronic insults, including ischaemic injury and doxorubicin-induced cardiotoxicity. Accordingly, conditional deletion of Met in cardiomyocytes results in impaired organ defence against oxidative stress. After ischaemic injury, activation of Met provides strong anti-apoptotic stimuli for cardiomyocytes through PI3K (phosphoinositide 3-kinase)/Akt and MAPK (mitogen-activated protein kinase) cascades. Recently, we found that HGF/Met is also important for autophagy regulation in cardiomyocytes via the mTOR (mammalian target of rapamycin) pathway. HGF/Met induces proliferation and migration of endothelial cells through Rac1 (Ras-related C3 botulinum toxin substrate 1) activation. In fibroblasts, HGF/Met antagonizes the actions of TGFβ1 (transforming growth factor β1) and AngII (angiotensin II), thus preventing fibrosis. Moreover, HGF/Met influences the inflammatory response of macrophages and the immune response of dendritic cells, indicating its protective function against atherosclerotic and autoimmune diseases. The HGF/Met axis also plays an important role in regulating self-renewal and myocardial regeneration through the enhancement of cardiac progenitor cells. HGF/Met has beneficial effects against myocardial infarction and endothelial dysfunction: the cellular and molecular mechanisms underlying repair function in the heart and blood vessels are common and include pro-angiogenic, anti-inflammatory and anti-fibrotic actions. Thus administration of HGF or HGF mimetics may represent a promising therapeutic agent for the treatment of both coronary and peripheral artery disease.

Current therapies and investigational drugs for peripheral arterial disease

Peripheral artery disease (PAD) is associated with elevated morbidity and mortality with cardiovascular (CV) disease. The guideline recommends smoking cessation and antiplatelet/antithrombotic drugs for asymptomatic and symptomatic PAD patients. It also recommends that PAD patients with critical limb ischemia (CLI) should be considered to receive endovascular and open surgical treatment for limb salvage. Although PAD patients with CLI receive these treatments, they are sometimes unable to deliver sufficient blood flow to eliminate their symptoms. Thus specific strategies are needed to promote enough blood flow. To establish the effective method, many investigations have been performed using cell-based therapy. Endothelial progenitor cells, mononuclear cells and mesenchymal stem cells have been well investigated in clinical settings. To induce angiogenesis, vascular endothelial growth factor, fibroblast growth factor and hepatocyte growth factor (HGF) have also been transfected in PAD patients. Among them, HGF is the most promising factor because it can induce angiogenesis without the induction of vascular inflammation and increased permeability. In this review article, we summarize current treatments and investigational drugs of PAD.

Clinical Safety and Preliminary Efficacy of Plasmid pUDK-HGF Expressing Human Hepatocyte Growth Factor (HGF) in Patients with Critical Limb Ischemia

OBJECTIVE

Critical limb ischemia (CLI) is the most severe form of peripheral arterial disease and a major unmet public health care need. This phase I clinical study was performed to assess the safety and preliminary efficacy of naked plasmid DNA (pUDK-HGF) expressing human hepatocyte growth factor (HGF) in patients with critical limb ischemia (CLI).

DESIGN

Twenty-one patients with CLI were enrolled and randomly divided into four dose groups (4-16 mg) to receive local injection of pUDK-HGF into ischemic calf and/or thigh muscles twice on days 1 and 15. Safety, including adverse events and physiological parameters, and preliminary efficacy, including pain severity score (VAS), ulcer size, transcutaneous oxygen pressure (TcPO2), and ankle brachial index (ABI), were evaluated throughout a 3 month follow up period.

RESULTS

All doses of pUDK-HGF were well tolerated by the patients. None of the adverse effects was considered to be related to pUDK-HGF injection. Two significant clinical results were observed after pUDK-HGF administration. The mean VAS value of all patients decreased from 4.52 at baseline to 0.30 (p < .01), and pain had disappeared in 14 out of 17 evaluable patients by day 91. Two of four ulcers had completely healed, with the other two patients having more than 25% ulcer size reduction in the long axis diameter. Of five patients with gangrene, one gangrenous wound had healed completely and two patients showed marked size reduction by day 91. The mean hemodynamic parameters (ABI, TcPO2) were also improved.

CONCLUSION

Intramuscular injection of pUDK-HGF is safe, and may provide symptomatic relief for CLI patients. A larger, randomized, double blinded phase II trial will provide more information on safety and efficacy.

Modulating the vascular response to limb ischemia: angiogenic and cell therapies

The age-adjusted prevalence of peripheral arterial disease in the US population has been estimated to approach 12%. The clinical consequences of occlusive peripheral arterial disease include pain on walking (claudication), pain at rest, and loss of tissue integrity in the distal limbs; the latter may ultimately lead to amputation of a portion of the lower extremity. Surgical bypass techniques and percutaneous catheter-based interventions may successfully reperfuse the limbs of certain patients with peripheral arterial disease. In many patients, however, the anatomic extent and distribution of arterial occlusion is too severe to permit relief of pain and healing of ischemic ulcers. No effective medical therapy is available for the treatment of such patients, for many of whom amputation represents the only hope for alleviation of symptoms. The ultimate failure of medical treatment and procedural revascularization in significant numbers of patients has led to attempts to develop alternative therapies for ischemic disease. These strategies include administration of angiogenic cytokines, either as recombinant protein or as gene therapy, and more recently, to investigations of stem/progenitor cell therapy. The purpose of this review is to provide an outline of the preclinical basis for angiogenic and stem cell therapies, review the clinical research that has been done, summarize the lessons learned, identify gaps in knowledge, and suggest a course toward successfully addressing an unmet medical need in a large and growing patient population.

Gene therapy in peripheral artery disease

INTRODUCTION

Despite the remarkable progress of medicine and endovascular procedures for revascularization, patients with critical limb ischemia (CLI) remain at high risk for amputation and often have a low quality of life due to pain and ulcers in the ischemic leg. Thus, a novel strategy for generating new blood vessels in CLI patients without treatment options is vital. Pre-clinical studies and Phase I clinical trials using VEGF and fibroblast growth factor (FGF) demonstrated promising results; however, more rigorous Phase II and III clinical trials failed to demonstrate benefits for CLI patients. Recently, two multicenter, double-blind, placebo-controlled clinical trials in Japan (Phase III) and the USA (Phase II) showed the benefits of hepatocyte growth factor (HGF) gene therapy for CLI patients. Although the number of patients included in these trials was relatively small, these results imply a distinct beneficial function for HGF over other angiogenic growth factors in a clinical setting.

AREAS COVERED

In this review, data from Phase I-III clinical trials of gene therapy for patients with peripheral artery disease (PAD) are examined. In addition, the potential mechanisms behind the success or failure of clinical trials are discussed.

EXPERT OPINION

Compared with VEGF and FGF, HGF has a unique molecular effect on inflammation, fibrosis and cell senescence under pathological conditions. These features may explain the clinical benefits of HGF in PAD patients.

An engineered dimeric fragment of hepatocyte growth factor is a potent c-MET agonist

Hepatocyte growth factor (HGF), through activation of the c-MET receptor, mediates biological processes critical for tissue regeneration; however, its clinical application is limited by protein instability and poor recombinant expression. We previously engineered an HGF fragment (eNK1) that possesses increased stability and expression yield and developed a c-MET agonist by coupling eNK1 through an introduced cysteine residue. Here, we further characterize this eNK1 dimer and show it elicits significantly greater c-MET activation, cell migration, and proliferation than the eNK1 monomer. The efficacy of the eNK1 dimer was similar to HGF, suggesting its promise as a c-MET agonist.

Hepatocyte Growth Factor Isoforms in Tissue Repair, Cancer, and Fibrotic Remodeling

Hepatocyte growth factor (HGF), also known as scatter factor (SF), is a pleotropic factor required for normal organ development during embryogenesis. In the adult, basal expression of HGF maintains tissue homeostasis and is up-regulated in response to tissue injury. HGF expression is necessary for the proliferation, migration, and survival of epithelial and endothelial cells involved in tissue repair in a variety of organs, including heart, lung, kidney, liver, brain, and skin. The administration of full length HGF, either as a protein or using exogenous expression methodologies, increases tissue repair in animal models of tissue injury and increases angiogenesis. Full length HGF is comprised of an N-terminal hairpin turn, four kringle domains, and a serine protease-like domain. Several naturally occurring alternatively spliced isoforms of HGF were also identified. The NK1 variant contains the N-terminal hairpin and the first kringle domain, and the NK2 variant extends through the second kringle domain. These alternatively spliced forms of HGF activate the same receptor, MET, but they differ from the full length protein in their cellular activities and their biological functions. Here, we review the species-specific expression of the HGF isoforms, their regulation, the signal transduction pathways they activate, and their biological activities.

Pharmacodynamic change in plasma angiogenic proteins: a dose-escalation phase 1 study of the multi-kinase inhibitor lenvatinib

Background

Lenvatinib (E7080), an oral multi-kinase inhibitor, has inhibitory action on tumor cell proliferation and tumor angiogenesis in preclinical models. We evaluated correlations between pharmacodynamic (PD) biomarkers with patient clinical outcomes in a lenvatinib phase 1 dose-escalation study.

Methods

Plasma angiogenic proteins were evaluated as potential PD biomarkers of response to lenvatinib in a dose-escalation phase 1 study. Lenvatinib was administered to 27 patients by twice-daily dosing in 3-week cycles; 2 weeks of treatment followed by 1 week of rest until discontinuation. Blood samples for plasma proteins were collected on days 1 (baseline), 8, and 15 of cycle 1, and days 1, 8, and 15 of cycle 2. Selected clinical outcomes, including tumor shrinkage and adverse events (AEs), were used for correlative analyses of pharmacokinetic parameters and PD biomarkers.

Results

Tumor shrinkage and changes in PD biomarkers (increased vascular endothelial growth factor [VEGF] and stromal cell-derived factor 1 alpha [SDF1α] levels and decreased soluble VEGF receptor 2 [sVEGFR2] levels) significantly correlated with increasing lenvatinib exposure. Observed changes in levels of VEGF, SDF1α, and sVEGFR2 were maintained on day 15 of cycle 1, but returned to baseline during the 1-week rest period, and similar changes were induced by reinstitution of treatment in cycle 2. The worst grades of hypertension, proteinuria, and fatigue were associated with changes in VEGF and HGF at day 8 of cycle 1. Maximum tumor shrinkage was correlated with increased SDF1α levels. Decreased sVEGFR2 level was also correlated with tumor shrinkage and frequency of hypertension, proteinuria, and fatigue. Tumor shrinkage significantly correlated with the worst grade of proteinuria, but not with hypertension or fatigue.

Conclusion

PD biomarker changes observed in plasma angiogenic proteins are correlated with lenvatinib-induced tumor shrinkage and AEs. Our findings warrant further assessment of plasma proteins associated with angiogenesis as potential biomarkers of lenvatinib activity.

Trial registration

ClinicalTrial.gov: NCT00280397 (January 20, 2006).

Gene therapy for peripheral arterial disease

INTRODUCTION

Gene therapy has emerged as a novel therapy to promote angiogenesis in patients with critical limb ischemia (CLI) caused by peripheral artery disease. Researchers working in this area have focused on pro-angiogenic factors, such as VEGF, fibroblast growth factor (FGF) and hepatocyte growth factor (HGF). Based on the elaborate studies and favorable results of basic research using naked plasmid DNA (pDNA) encoding these growth factors, some clinical Phase I and Phase II trials have been performed. The results of these studies demonstrate the safety of these approaches and their potential for symptomatic improvement in CLI patients. However, the Phase III clinical trials have so far been limited to HGF gene therapy. Because one pitfall of the Phase III trials has been the limited transgene expression achieved using naked pDNA alone, the development of more efficient gene transfer systems, such as ultrasound microbubbles and the needleless injector, as well as the addition of other genes will make these novel therapies more effective and ease the symptoms of CLI.

AREAS COVERED

This study reviews the previously published basic research and clinical trials that have studied VEGF, FGF and HGF gene therapies for the treatment of CLI. Adjunctive therapies, such as the addition of prostacyclin synthase genes and the development of more efficient gene transfer techniques for pDNA, are also reviewed.

EXPERT OPINION

To date, clinical studies have demonstrated the safety of gene therapy in limb ischemia but the effectiveness of this treatment has not been determined. Larger clinical studies, as well as the development of more effective gene therapy, are needed to achieve and confirm beneficial effects.

Hepatocyte growth factor in dampening liver immune-mediated pathology in acute viral hepatitis without compromising antiviral activity

BACKGROUND AND AIM

Hepatocyte growth factor (HGF) is a pleiotropic cytokine related with cell proliferation and survival; however, its role in viral hepatitis is not elucidated. In this study, we studied HGF immune role in viral hepatitis.

METHODS

Mice received hydrodynamically delivered HGF plasmid or control plasmid and then infected with adenovirus, and parameters of immune-mediated liver damage were evaluated. We studied dendritic cell (DC) activation in the presence of HGF. T cells collected from infected mice were restimulated with virally infected DC to measure cytokine production in vitro.

RESULTS

HGF ameliorated the liver inflammation during viral hepatitis as alanine transferase, intrahepatic lymphocytes, and splenocyte counts were diminished by HGF. Lower histological scores of liver pathology were observed in the HGF group. DC from the HGF group expressed reduced CD40. The hepatic expression and serum concentration of IL-12p40 were diminished in HGF-transfected mice. In vitro experiments with DC confirmed that HGF diminished CD40 expression and IL-12p40 production. The expression and serum levels of IFN-γ, IL-6 and CXCL9 were significantly decreased in the HGF group. HGF overexpression diminished the expression and concentration of IL-10 and TGF-β. The frequency of PD-1(+) Tim-3(+) in CD8 T cells was decreased by HGF overexpression. Moreover, T cells in the HGF group at day 14 secreted more IFN-γ and TNF-α than those in the control group when restimulated with virally infected DC.

CONCLUSION

HGF modulated DC activation and T cell priming, thereby limiting the immune-mediated damage in the liver. However, viral clearance was not compromised by HGF.

Therapeutic Angiogenesis by Gene Therapy for Critical Limb Ischemia: Choice of Biological Agent

Peripheral artery disease (PAD) is caused by atherosclerosis, hardening and narrowing arteries over time due to buildup of fatty deposit in vascular bed called plaque. Severe blockage of an artery of the lower extremity markedly reduce blood flow, resulting in critical limb ischemia (CLI) manifested by a variety of clinical syndromes including rest pain in the feet or toes, ulcer and gangrene with infection. Despite significant advances in clinical care and interventions for revascularization, patients with CLI remain at high risk for amputation and cardiovascular death. To overcome this unmet need, therapeutic angiogenesis using angiogenic growth factors has evolved in an attempt to increase blood flow in ischemic limb. Initial animal studies and phase I clinical trials with vascular endothelial growth factor (VEGF) or fibroblast growth factor (FGF) demonstrated promising results, inspiring scientists to progress forward. However, more rigorous phase II and III clinical trials have failed to demonstrate beneficial effects of these angiogenic growth factors to date. Recently, two multicenter, double-blind, placebo-controlled clinical trials in Japan (phase III) and US (phase II) demonstrated that hepatocyte growth factor (HGF) gene therapy for CLI significant improved primary end points and tissue oxygenation up to two years in comparison to placebo. These clinical results implicate a distinct action of HGF on cellular processes involved in vascular remodeling under pathological condition. This review presents data from phase I-III clinical trials of therapeutic angiogenesis by gene therapy in patients with PAD. Further, we discuss the potential explanation for the success or failure of clinical trials in the context of the biological mechanisms underlying angiogenesis and vascular remodeling, including cellular senescence, inflammation, and tissue fibrosis.

Short hairpin RNA gene silencing of prolyl hydroxylase-2 with a minicircle vector improves neovascularization of hindlimb ischemia

In this study, we target the hypoxia inducible factor-1 alpha (HIF-1-alpha) pathway by short hairpin RNA interference therapy targeting prolyl hydroxylase-2 (shPHD2). We use the minicircle (MC) vector technology as an alternative for conventional nonviral plasmid (PL) vectors in order to improve neovascularization after unilateral hindlimb ischemia in a murine model. Gene expression and transfection efficiency of MC and PL, both in vitro and in vivo, were assessed using bioluminescence imaging (BLI) and firefly luciferase (Luc) reporter gene. C57Bl6 mice underwent unilateral electrocoagulation of the femoral artery and gastrocnemic muscle injection with MC-shPHD2, PL-shPHD2, or phosphate-buffered saline (PBS) as control. Blood flow recovery was monitored using laser Doppler perfusion imaging, and collaterals were visualized by immunohistochemistry and angiography. MC-Luc showed a 4.6-fold higher in vitro BLI signal compared with PL-Luc. BLI signals in vivo were 4.3×10(5)±3.3×10(5) (MC-Luc) versus 0.4×10(5)±0.3×10(5) (PL-Luc) at day 28 (p=0.016). Compared with PL-shPHD2 or PBS, MC-shPHD2 significantly improved blood flow recovery, up to 50% from day 3 until day 14 after ischemia induction. MC-shPHD2 significantly increased collateral density and capillary density, as monitored by alpha-smooth muscle actin expression and CD31(+) expression, respectively. Angiography data confirmed the histological findings. Significant downregulation of PHD2 mRNA levels by MC-shPHD2 was confirmed by quantitative polymerase chain reaction. Finally, Western blot analysis confirmed significantly higher levels of HIF-1-alpha protein by MC-shPHD2, compared with PL-shPHD2 and PBS. This study provides initial evidence of a new potential therapeutic approach for peripheral artery disease. The combination of HIF-1-alpha pathway targeting by shPHD2 with the robust nonviral MC plasmid improved postischemic neovascularization, making this approach a promising potential treatment option for critical limb ischemia.

Proteomic profiling of salivary gland after nonviral gene transfer mediated by conventional plasmids and minicircles

In this study, we compared gene transfer efficiency and host response to ultrasound-assisted, nonviral gene transfer with a conventional plasmid and a minicircle vector in the submandibular salivary glands of mice. Initially, we looked at gene transfer efficiency with equimolar amounts of the plasmid and minicircle vectors, corroborating an earlier report showing that minicircle is more efficient in the context of a physical method of gene transfer. We then sought to characterize the physiological response of the salivary gland to exogenous gene transfer using global proteomic profiling. Somewhat surprisingly, we found that sonoporation alone, without a gene transfer vector present, had virtually no effect on the salivary gland proteome. However, when a plasmid vector was used, we observed profound perturbations of the salivary gland proteome that compared in magnitude to that seen in a previous report after high doses of AAV. Finally, we found that gene transfer with a minicircle induces only minor proteomic alterations that were similar to sonoporation alone. Using mass spectrometry, we assigned protein IDs to 218 gel spots that differed between plasmid and minicircle. Bioinformatic analysis of these proteins demonstrated convergence on 68 known protein interaction pathways, most notably those associated with innate immunity, cellular stress, and morphogenesis.

Gene therapy and cell-based therapies for therapeutic angiogenesis in peripheral artery disease

Gene therapy and cell-based therapy have emerged as novel therapies to promote therapeutic angiogenesis in critical limb ischemia (CLI) caused by peripheral artery disease (PAD). Although researchers initially focused on gene therapy using proangiogenic factors, such as vascular endothelial growth factor (VEGF), fibroblast growth factor (FGF), and hepatocyte growth factors (HGF), cell therapy using bone marrow mononuclear cells (BMMNCs), mesenchymal stem cells (BMMSCs), G-CSF-mobilized peripheral blood mononuclear cells (M-PBMNCs), and endothelial progenitor cells (EPCs) have also been extensively studied. Based on the elaborate studies and favorable results of basic research, some clinical phase I/II trials have been performed, and the results demonstrate the safety of these approaches and their potential for symptomatic improvement in CLI. However, the phase 3 clinical trials have thus far been limited to gene therapy using the HGF gene. Further studies using well-designed larger placebo-controlled and long-term randomized control trials (RCTs) will clarify the effectiveness of gene therapy and cell-based therapy for the treatment of CLI. Furthermore, the development of efficient gene transfer systems and effective methods for keeping transplanted cells healthy will make these novel therapies more effective and ease the symptoms of CLI.

Quantitative optical imaging of vascular response in vivo in a model of peripheral arterial disease

The mouse hind limb ischemia (HLI) model is well established for studying collateral vessel formation and testing therapies for peripheral arterial disease, but there is a lack of quantitative techniques for intravitally analyzing blood vessel structure and function. To address this need, non-invasive, quantitative optical imaging techniques were developed to assess the time-course of recovery in the mouse HLI model. Hyperspectral imaging and optical coherence tomography (OCT) were used to non-invasively image hemoglobin oxygen saturation and microvessel morphology plus blood flow, respectively, in the anesthetized mouse after induction of HLI. Hyperspectral imaging detected significant increases in hemoglobin saturation in the ischemic paw as early as 3 days after femoral artery ligation (P < 0.01), and significant increases in distal blood flow were first detected with OCT 14 days postsurgery (P < 0.01). Intravital OCT images of the adductor muscle vasculature revealed corkscrew collateral vessels characteristic of the arteriogenic response to HLI. The hyperspectral imaging and OCT data significantly correlated with each other and with laser Doppler perfusion imaging (LDPI) and tissue oxygenation sensor data (P < 0.01). However, OCT measurements acquired depth-resolved information and revealed more sustained flow deficits following surgery that may be masked by more superficial measurements (LDPI, hyperspectral imaging). Therefore, intravital OCT may provide a robust biomarker for the late stages of ischemic limb recovery. This work validates non-invasive acquisition of both functional and morphological data with hyperspectral imaging and OCT. Together, these techniques provide cardiovascular researchers an unprecedented and comprehensive view of the temporal dynamics of HLI recovery in living mice.

High concentration but low activity of hepatocyte growth factor in periodontitis

BACKGROUND

High levels of hepatocyte growth factor (HGF), a healing factor with regenerative and cytoprotective effects, are associated with inflammatory diseases, including periodontitis. HGF biologic activity requires binding to its receptors, the proto-oncogene c-Met and heparan sulfate proteoglycan (HSPG). This study investigates HGF expression and its relationship to subgingival microbiota in medically healthy individuals with and without periodontitis.

METHODS

Saliva, gingival crevicular fluid (GCF), and blood samples from 30 patients with severe periodontitis and 30 healthy controls were analyzed for HGF concentration using enzyme-linked immunosorbent assay and binding affinity for HSPG and c-Met using surface plasmon resonance. The regenerative effects of saliva from three patients and controls were analyzed in an in vitro model of cell injury. Subgingival plaques were analyzed for the presence of 18 bacterial species.

RESULTS

Patients with periodontitis showed higher HGF concentrations in saliva, GCF, and serum (P <0.001); however, the binding affinities for HSPG and c-Met were reduced in GCF and saliva (P <0.002). In contrast to the controls, saliva from patients showed no significant regenerative effect over time on gingival epithelial cells. Compared with controls, patients had a higher prevalence of periodontally related bacteria.

CONCLUSIONS

Higher circulatory HGF levels indicate a systemic effect of periodontitis. However, the HGF biologic activity at local inflammation sites was reduced, and this effect was associated with the amount of periodontal bacteria. Loss of function of healing factors may be an important mechanism in degenerative processes in periodontally susceptible individuals.