Safety Evaluation of Clinical Gene Therapy Using Hepatocyte Growth Factor to Treat Peripheral Arterial Disease

Advancements in Gene-Based Therapeutic Angiogenesis for Chronic Limb-Threatening Ischemia

The objective of this article is to summarize the research progress and discuss the current difficulties of gene-based therapeutic angiogenesis in lower limb ischemic diseases, so as to provide new research directions for the non-invasive treatment of lower limb ischemia. The basic and clinical trials of gene-based therapeutic angiogenesis in lower limb ischemia in recent years were read and reviewed. Growth factors such as vascular endothelial growth factor, hepatocyte growth factor, and fibroblast growth factor have been extensively studied for their application in lower limb ischemic diseases. However, clinical studies across various phases have shown inconsistent efficacy endpoints. The efficacy of gene therapy remains questionable. Before exploring efficient methods of delivering pro-angiogenic genes to ischemic tissues, clarification is needed regarding whether the goal of gene therapy is to simply promote collateral circulation or create a conducive tissue microenvironment for angiogenesis. In conclusion, pre-clinical and clinical studies have demonstrated the potential of therapeutic angiogenesis, but more systematic and comprehensive research is needed to explore safer, more effective, and cost-effective treatment methods.

Recombinant Human Hepatocyte Growth Factor Plasmids for Treating Patients with Chronic Limb Threatening Ischaemia: A Systematic Review and Meta-analysis

OBJECTIVE

Recombinant human hepatocyte growth factor (HGF) plasmids are novel alternatives to salvage limbs in patients with chronic limb threatening ischaemia (CLTI). A systematic review and meta-analysis of data was conducted to assess the therapeutic efficacy of HGF plasmids in patients with CLTI.

DATA SOURCES

Randomised controlled studies evaluating HGF plasmid efficacy in patients with CLTI were identified using MEDLINE, Embase, Cochrane Database of Systematic Reviews, and ClinicalTrials.gov databases.

REVIEW METHODS

Meta-analyses of the reported relative risk (RR) or mean difference (MD) were conducted. Subgroup analyses were performed to determine the efficacy of HGF plasmids in cohorts excluding Buerger's disease. Certainty of evidence for each outcome was assessed.

RESULTS

Seven studies (n = 655 participants) were included. Based on low certainty evidence, patients treated with HGF had a significantly higher complete ulcer healing rate (RR 1.99, 95% confidence interval [CI] 1.30 - 3.04; p = .002) than patients treated with placebo. HGF treatment was associated with reduced visual analogue scale (VAS) scores of pain severity (MD -1.56, 95% CI -2.12 - -1.00; p < .001) vs. placebo in patients with CLTI assessed at three month follow up (low certainty evidence); no significant differences were observed in major amputation (RR 0.91, 95% CI 0.48 - 1.73; p = .77) (low certainty evidence) or all cause mortality rate (RR 0.93, 95% CI 0.38 - 2.27; p = .87) (low certainty evidence) between patients treated with HGF and placebo. Low certainty evidence suggested no significant differences in change in ankle brachial index at six months (MD 0.00, 95% CI -0.09 - 0.09; p = 1.0) between patients treated with HGF and placebo. The complete ulcer healing rate and improved three month VAS scores of pain severity benefits persisted in subgroup analyses (low certainty evidence).

CONCLUSION

Low certainty evidence suggested that HGF treatment is associated with an increased complete ulcer healing rate and reduced ischaemic pain in patients with CLTI.

Diffusive delivery of plasmid DNA using zwitterionic carboxyalkyl poly(1-vinylimidazole) into skeletal muscle in vivo

Zwitterionic carboxyalkyl poly(1-vinylimidazole) (CA-PVIm) polymers with imidazolium cations and carboxylate anions have been synthesized as a carrier for the in vivo delivery of plasmid DNA (pDNA) to skeletal muscle. From differential scanning calorimetry measurements, resulting CA-PVIm had intermediate water in hydration water as a biocompatible polymer. Notably, when the pDNA and resulting CA-PVIm were mixed, slight retarded bands of the pDNA were observed in agarose gel electrophoresis, suggesting the polyion complex (PIC) formation between the pDNA and CA-PVIm despite zwitterionic polymers. Resulting PICs maintained the higher-order structure of the pDNA. Using resulting pDNA PICs, the highest pDNA expression by intramuscular injection was achieved in the PIC with 7 mol% carboxymethylated PVIm, that is, CA1(7)-PVIm, observed in a widespread area by in vivo imaging system. These results suggest that the CA1(7)-PVIm/pDNA PIC is effective for the diffusive delivery of the pDNA into skeletal muscle for the treatment of serious muscle diseases.

Clinical application and potential pluripotent effects of hepatocyte growth factor in spinal cord injury regeneration

INTRODUCTION

Spinal cord injury (SCI) is a condition in which the spinal cord parenchyma is damaged by various factors. The mammalian central nervous system has been considered unable to regenerate once damaged, but recent progress in basic research has gradually revealed that injured neural cells can indeed regenerate. Drug therapy using novel agents is being actively investigated as a new treatment for SCI. One notable treatment method is regeneration therapy using hepatocyte growth factors (HGF).

AREA COVERED

HGF has pluripotent neuroregenerative actions, as indicated by its neuroprotective and regenerative effects on the microenvironment and damaged cells, respectively. This review examines these effects in various phases of SCI, from basic research to clinical studies, and the application of this treatment to other diseases.

EXPERT OPINION

In regenerative medicine for SCI, drug therapies have tended to be more likely to be developed compared to cell replacement treatment. Nevertheless, there are still challenges to be addressed for these clinical applications due to a wide variety of pathology and animal experimental models of basic study, but HGF could be an effective treatment for SCI with expanded application.

Peripheral inflammatory response in people after acute ischaemic stroke and isolated spontaneous cervical artery dissection

The systemic inflammatory response following acute ischaemic stroke remains incompletely understood. We characterised the circulating inflammatory profile in 173 acute ischaemic stroke patients by measuring 65 cytokines and chemokines in plasma. Participants were grouped based on their inflammatory response, determined by high-sensitivity C-reactive protein levels in the acute phase. We compared stroke patients' profiles with 42 people experiencing spontaneous cervical artery dissection without stroke. Furthermore, variations in cytokine levels among stroke aetiologies were analysed. Follow-up samples were collected in a subgroup of ischaemic stroke patients at three and twelve months. Ischaemic stroke patients had elevated plasma levels of HGF and SDF-1α, and lower IL-4 levels, compared to spontaneous cervical artery dissection patients without stroke. Aetiology-subgroup analysis revealed reduced levels of nine cytokines/chemokines (HGF, SDF-1α, IL-2R, CD30, TNF-RII, IL-16, MIF, APRIL, SCF), and elevated levels of IL-4 and MIP-1β, in spontaneous cervical artery dissection (with or without ischaemic stroke as levels were comparable between both groups) compared to other aetiologies. The majority of cytokine/chemokine levels remained stable across the study period. Our research indicates that stroke due to large artery atherosclerosis, cardioembolism, and small vessel occlusion triggers a stronger inflammatory response than spontaneous cervical artery dissection.

Exercise Therapy in the Management of Peripheral Arterial Disease

The incidence and prevalence of peripheral artery disease (PAD) are increasing globally and have a marked economic burden in the United States. The American Heart Association/American College of Cardiology guidelines recommend exercise therapy as a Class 1A, but its utilization remains suboptimal. This state-of-the-art review aims to provide a comprehensive review of the most updated information available on PAD, along with its risk factors, management options, outcomes, economic burden, and the role of exercise therapy in managing PAD.

Angiogenesis-related proteins as biomarkers for peripheral artery disease

Background

Angiogenesis plays an important role in peripheral artery disease (PAD) and angiogenesis-related proteins may act as prognostic biomarkers. This study assesses the potential for angiogenesis-related proteins to predict adverse events associated with PAD.

Methods

This was a case-control study. Patients with PAD (n = 250) and without PAD (n = 125) provided blood samples and were followed prospectively for three years. Concentrations of 17 angiogenesis-related proteins were measured in plasma. The incidence of major adverse limb event (MALE), defined as a composite of major amputation or vascular intervention, was the primary outcome. Worsening PAD status, defined as a drop in ankle brachial index ≥ 0.15, was the secondary outcome. Multivariable regression adjusted for baseline characteristics was conducted to determine the prognostication value of angiogenesis-related proteins in predicting MALE.

Findings

Relative to patients without PAD, 8 proteins related to angiogenesis were expressed differentially in PAD patients. Worsening PAD status and MALE were observed in 52 (14%) and 83 (22%) patients, respectively. Hepatocyte growth factor (HGF) was the most reliable predictor of MALE (adjusted HR 0.79, 95% CI 0.15-0.86). Compared to individuals with high HGF, patients with low HGF had a decreased three-year freedom from MALE [66% vs 88%, p = 0.001], major amputation [93% vs 98%, p = 0.023], vascular intervention [68% vs 88%, p = 0.001], and worsening PAD status [81% vs 91%, p = 0.006].

Interpretation

Measuring plasma levels of HGF in individuals with PAD can assist in identifying patients at elevated risk of adverse events related to PAD who may benefit from additional evaluation or treatment.

Hepatocyte growth factor-modified hair follicle stem cells ameliorate cerebral ischemia/reperfusion injury in rats

BACKGROUND

Hair follicle stem cells (HFSCs) are considered as a promising cell type in the stem cell transplantation treatment of neurological diseases because of their rich sources, easy access, and the same ectoderm source as the nervous system. Hepatocyte growth factor (HGF) is a pleiotropic cytokine that shows neuroprotective function in ischemic stroke. Here we assessed the therapeutic effects of HFSCs on ischemic stroke injury and the synthetic effect of HGF along with HFSCs.

METHODS

Rat HFSCs were intravenously transplanted into a middle cerebral artery ischemia/reperfusion (I/R) rat model. Neurological scoring and TTC staining were performed to assess the benefits of HFSC transplantation. Inflammatory cytokines, blood-brain barrier integrity and angiogenesis within penumbra were estimated by Western blot and immunohistochemistry. The differentiation of HFSCs was detected by immunofluorescence method 2 weeks after transplantation.

RESULTS

HFSC transplantation could significantly inhibit the activation of microglia, improve the integrity of blood-brain barrier and reduce brain edema. Moreover, the number of surviving neurons and microvessels density in the penumbra were upregulated by HFSC transplantation, leading to better neurological score. The combination of HFSCs and HGF could significantly improve the therapeutic benefit.

CONCLUSION

Our results indicate for the first time that HGF modified HFSCs can reduce I/R injury and promote the neurological recovery by inhibiting inflammatory response, protecting blood-brain barrier and promoting angiogenesis.

Gene Therapy of Chronic Limb-Threatening Ischemia: Vascular Medical Perspectives

A decade ago, gene therapy seemed to be a promising approach for the treatment of chronic limb-threatening ischemia, providing new perspectives for patients without conventional, open or endovascular therapeutic options by potentially enabling neo-angiogenesis. Yet, until now, the results have been far from a safe and routine clinical application. In general, there are two approaches for inserting exogenous genes in a host genome: transduction and transfection. In case of transduction, viral vectors are used to introduce genes into cells, and depending on the selected strain of the virus, a transient or stable duration of protein production can be achieved. In contrast, the transfection of DNA is transmitted by chemical or physical processes such as lipofection, electro- or sonoporation. Relevant risks of gene therapy may be an increasing neo-vascularization in undesired tissue. The risks of malignant transformation and inflammation are the potential drawbacks. Additionally, atherosclerotic plaques can be destabilized by the increased angiogenesis, leading to arterial thrombosis. Clinical trials from pilot studies to Phase II and III studies on angiogenic gene therapy show mainly a mixed picture of positive and negative final results; thus, the role of gene therapy in vascular occlusive disease remains unclear.

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.

Title: Gene transfer by pyro-drive jet injector is a novel therapeutic approach for muscle diseases

The angiogenic gene therapy is an attractive approach for the treatment of ischemic muscle diseases, including peripheral arterial disease and ischemic heart diseases. Although a variety of gene transfer methods have been developed, the efficiency of gene transfer is still limited. We have been developing the needleless high-energy bioinjector device, Pyro-drive Jet Injector (PJI), based on pyrotechnics using a combination of ignition powder and gunpowder, however, the utility of PJI in gene transfer into muscle tissues remains unclear. pcDNA3.1 plasmid containing Flag was injected to the thigh muscles of C57BL/6J mice using PJI or needle, as a control. Histological analysis demonstrated that the protein expression of Flag was observed in a wider range in PJI group than in needle group. To assess the validity of PJI for gene therapy, pcDNA3.1-human fibroblast growth factor 2 (FGF2), which has angiogenic activity and tissue protective properties, was injected into the ischemic thigh muscles with PJI or needle. ELISA assay revealed that the protein expression of FGF2 was increased in the thigh muscle tissues by PJI-mediated gene delivery. Significantly, histological analyses revealed that muscle fiber cross-sectional area and the number of endothelial marker CD31 (+) cells was increased in ischemic hind-limb tissues of the PJI-FGF2 group but not in those of needle-FGF2 group. To expand the applicability of the PJI-mediated gene transfer, pcDNA3.1-venus plasmid was injected into murine hearts with PJI or needle. PJI method was successful in gene transfer into murine hearts, especially into cardiomyocytes, with high efficiency when compared to needle method. Collectively, the non-needle, non-liposomal and non-viral gene transfer by PJI could be a novel therapeutic approach for muscle diseases.

Structure-Activity Relationship of Mono-Ion Complexes for Plasmid DNA Delivery by Muscular Injection

The structure-activity relationship of mono-ion complexes (MICs) for plasmid DNA (pDNA) delivery by muscular injection is demonstrated. MICs were formed between pDNA and monocationic poly(ethylene glycol) (PEG) macromolecules. As monocationic PEGs, the ω-amide-pentylimidazolium (APe-Im) end-modified PEGs with a stable amide (Am) and hydrolytic ester (Es) bond, that is, APe-Im-Am-PEG and APe-Im-Es-PEG, respectively, are synthesized. The difference between the APe-Im-Am-PEG and APe-Im-Es-PEG was only a spacer structure between a terminal cation and a PEG chain. The resulting pDNA MICs with APe-Im-Am-PEG at a charge ratio (+/-) of 32 or 64 were more stable than those with APe-Im-Es-PEG in the presence of serum proteins. The highest gene expression by muscular injection was achieved using the APe-Im-Am-PEG/pDNA MIC at a charge ratio (+/-) of 32 with a smaller particle diameter of approximately 50 nm, as compared to that charge ratio of 64. Consequently, the pDNA MIC with the monocationic PEG with a stable amide spacer, as compared to a hydrolytic ester spacer, is considered to be suitable for the highest gene expression by muscular injection.

Noncorrelative relation between in vitro and in vivo for plasmid DNA transfection by succinylated polyethylenimine muscular injection

The polyion complexes (PICs) between plasmid DNA (pDNA) and succinylated branched polyethylenimine (bPEI-Et-COOH) were formed for in vivo pDNA delivery by muscular injection. Transmission electron microscopy (TEM) observation revealed that the PIC between pDNA and bPEI-Et-COOH with higher succinylated degree formed the particle structure with corona-like shell. Furthermore, confocal laser scanning microscopy (CLSM) observation revealed that pDNAs were successfully delivered inside the cells and that the pDNAs were colocalized with the nuclei of the cells after endosomal escape. Although the pDNA/bPEI-Et-COOH PICs mediated significant gene expression in vitro, the PICs did not mediate gene expression in vivo muscular injection. Consequently, the pDNA transfection by bPEI-Et-COOH was noncorrelative between in vitro and in vivo in spite of low toxicity by succinylation both in vitro and in vivo. The noncorrelative relation between in vitro and in vivo for pDNA transfection by bPEI-Et-COOH muscular injection would be considerable design for pDNA carriers in vivo.

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.

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.

A Randomized, Double-Blind, Placebo-Controlled Phase II Study of Hepatocyte Growth Factor in the Treatment of Critical Limb Ischemia

NL003 is a plasmid engineered to simultaneously express two isoforms of hepatocyte growth factor. This phase II study was performed to assess the clinical safety and efficacy of intramuscular injection of NL003 in critical limb ischemia (CLI) patients for 6 months. Two hundred patients (Rutherford scale 4-5) were randomly assigned: placebo (n = 50), low-dose NL003 (n = 50), middle-dose NL003 (n = 50), or high-dose NL003 (n = 50). The drug was administered in the affected limb of 197 patients on days 0, 14, and 28. No significant differences in the incidence of adverse events (AEs) or serious AEs were found among the groups. At 6 months, pain severity was significantly reduced in all NL003 groups, but not in the placebo group (p < 0.05). The proportion of patients with complete ulcer healing in the high-dose group was significantly higher than that of the placebo group (p = 0.0095). There were no statistically significant differences in transcutaneous oxygen pressure (TcPO2), ankle-brachial index (ABI), or toe-brachial index (TBI) value among the four groups throughout the study period. These results provide the first effective evidence of significant improvements in total healing of ulcers in treated legs, complete pain relief without analgesics, and safety for NL003 in patients with Rutherford stage 4-5.

Local pharmacological induction of angiogenesis: Drugs for cells and cells as drugs

The past decades have seen significant advances in pro-angiogenic strategies based on delivery of molecules and cells for conditions such as coronary artery disease, critical limb ischemia and stroke. Currently, three major strategies are evolving. Firstly, various pharmacological agents (growth factors, interleukins, small molecules, DNA/RNA) are locally applied at the ischemic region. Secondly, preparations of living cells with considerable bandwidth of tissue origin, differentiation state and preconditioning are delivered locally, rarely systemically. Thirdly, based on the notion, that cellular effects can be attributed mostly to factors secreted in situ, the cellular secretome (conditioned media, exosomes) has come into the spotlight. We review these three strategies to achieve (neo)angiogenesis in ischemic tissue with focus on the angiogenic mechanisms they tackle, such as transcription cascades, specific signalling steps and cellular gases. We also include cancer-therapy relevant lymphangiogenesis, and shall seek to explain why there are often conflicting data between in vitro and in vivo. The lion's share of data encompassing all three approaches comes from experimental animal work and we shall highlight common technical obstacles in the delivery of therapeutic molecules, cells, and secretome. This plethora of preclinical data contrasts with a dearth of clinical studies. A lack of adequate delivery vehicles and standardised assessment of clinical outcomes might play a role here, as well as regulatory, IP, and manufacturing constraints of candidate compounds; in addition, completed clinical trials have yet to reveal a successful and efficacious strategy. As the biology of angiogenesis is understood well enough for clinical purposes, it will be a matter of time to achieve success for well-stratified patients, and most probably with a combination of compounds.

Hepatocyte Growth Factor-Secreting Mesothelial Cell Sheets Suppress Progressive Fibrosis in a Rat Model of CKD

BACKGROUND

Although hepatocyte growth factor (HGF) has antifibrotic effects and is involved in angiogenesis and vasodilation, systemic administration of HGF to prevent kidney fibrosis is not a feasible strategy for suppressing interstitial fibrosis in patients with CKD.

METHODS

We investigated a novel therapy involving HGF transgenic cell sheets grown in culture from human mesothelial cells and administered to rats with unilateral ureteral obstruction (UUO). We compared progression of fibrosis in rats with UUO that received one of five interventions: HGF-transgenic mesothelial cell sheets transplanted to the kidney surface, HGF-transgenic mesothelial cell sheets transplanted to thigh, mesotherial cell sheets transplanted to kidney, no sheets, or HGF injections.

RESULTS

HGF transgenic cell sheets transplanted to the kidney strongly suppressed the induction of myofibroblasts and collagen in the kidney for 28 days; other interventions did not. Additionally, the HGF-secreting cell sheets ameliorated loss of peritubular capillaries and maintained renal blood flow.

CONCLUSIONS

These findings suggest that cell sheet therapy is a novel and promising strategy for inhibiting progressive fibrosis in CKD.

Impact of Dental Pulp Stem Cells Overexpressing Hepatocyte Growth Factor after Cerebral Ischemia/Reperfusion in Rats

Hepatocyte growth factor (HGF) has neuroprotective effects against ischemia-induced injuries. Dental pulp stem cell (DPSC) transplantation attenuates tissue injury in the brain of rats with post-transient middle cerebral artery occlusion. We sought to determine whether DPSCs that overexpress HGF can enhance their therapeutic effects on brain damage post-ischemia/reperfusion injury. Treatment with DPSCs overexpressing HGF reduced infarct volumes compared to unmodified DPSC treatment at 3 and 7 days post-transient middle cerebral artery occlusion. The use of unmodified DPSCs and DPSCs overexpressing HGF was associated with improved motor function compared to that with administration of vehicle at 7 days post-transient middle cerebral artery occlusion. DPSCs overexpressing HGF significantly inhibited microglial activation and pro-inflammatory cytokine production along with suppression of neuronal degeneration. Post-reperfusion, DPSCs overexpressing HGF attenuated the decreases in tight junction proteins, maintained blood-brain barrier integrity, and increased microvessel density in peri-infarct areas. The administration of DPSCs overexpressing HGF during the acute phase of stroke increased their neuroprotective effects by modulating inflammation and blood-brain barrier permeability, thereby promoting improvements in post-ischemia/reperfusion brain injury.

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.

Controlled release of basic fibroblast growth factor for angiogenesis using acoustically-responsive scaffolds

The clinical translation of pro-angiogenic growth factors for treatment of vascular disease has remained a challenge due to safety and efficacy concerns. Various approaches have been used to design spatiotemporally-controlled delivery systems for growth factors in order to recapitulate aspects of endogenous signaling and thus assist in translation. We have developed acoustically-responsive scaffolds (ARSs), which are fibrin scaffolds doped with a payload-containing, sonosensitive emulsion. Payload release can be controlled non-invasively and in an on-demand manner using focused, megahertz-range ultrasound (US). In this study, we investigate the in vitro and in vivo release from ARSs containing basic fibroblast growth factor (bFGF) encapsulated in monodispersed emulsions. Emulsions were generated in a two-step process utilizing a microfluidic device with a flow focusing geometry. At 2.5 MHz, controlled release of bFGF was observed for US pressures above 2.2 ± 0.2 MPa peak rarefactional pressure. Superthreshold US yielded a 12.6-fold increase in bFGF release in vitro. The bioactivity of the released bFGF was also characterized. When implanted subcutaneously in mice, ARSs exposed to superthreshold US displayed up to 3.3-fold and 1.7-fold greater perfusion and blood vessel density, respectively, than ARSs without US exposure. Scaffold degradation was not impacted by US. These results highlight the utility of ARSs in both basic and applied studies of therapeutic angiogenesis.

Delivery of growth factor-based therapeutics in vascular diseases: Challenges and strategies

Either cardiovascular or peripheral vascular diseases have become the major cause of morbidity and mortality worldwide. Recently, growth factors therapeutics, whatever administrated in form of exogenous growth factors or their relevant genes have been discovered to be an effective strategy for the prevention and therapy of vascular diseases, because of their promoting angiogenesis. Besides, as an alternative, stem cell-based therapy has been also developed in view of their paracrine-mediated effect or ability of differentiation toward angiogenesis-related cells under assistance of growth factors. Despite of being specific and potent, no matter growth factors or stem cells-based therapy, their full clinical transformation is limited from bench to bedside. In this review, the potential choices of therapeutic modes based on types of different growth factors or stem cells were firstly summarized for vascular diseases. The confronted various challenges such as lack of non-invasive delivery method, the physiochemical challenge, the short half-life time, and poor cell survival, were carefully analyzed for these therapeutic modes. Various strategies to overcome these limitations are put forward from the perspective of drug delivery. The expertised design of a suitable delivery form will undoubtedly provide valuable insight into their clinical application in the regenerative medicine.

Trimodal rescue of hind limb ischemia with growth factors, cells, and nanocarriers: fundamentals to clinical trials

Peripheral artery disease is a severe medical condition commonly characterized by critical or acute limb ischemia. Gradual accumulation of thrombotic plaques in peripheral arteries of the lower limb may lead to intermittent claudication or ischemia in muscle tissue. Ischemic muscle tissue with lesions may become infected, resulting in a non-healing wound. Stable progression of the non-healing wound associated with severe ischemia might lead to functional deterioration of the limb, which, depending on the severity, can result in amputation. Immediate rescue of ischemic muscles through revascularization strategies is considered the gold standard to treat critical limb ischemia. Growth factors offer multiple levels of protection in revascularization of ischemic tissue. In this review, the basic mechanism through which growth factors exert their beneficial properties to rescue the ischemic limb is extensively discussed. Moreover, clinical trials based on growth factor and stem cell therapy to treat critical limb ischemia are considered. The clinical utility of stem cell therapy for the treatment of limb ischemia is explained and recent advances in nanocarrier technology for selective growth factor and stem cell supplementation are summarized.

Interleukin-7 and Immunosenescence

The age of an individual is an important, independent risk factor for many of the most common diseases afflicting modern societies. Interleukin-7 (IL-7) plays a central, critical role in the homeostasis of the immune system. Recent studies support a critical role for IL-7 in the maintenance of a vigorous healthspan. We describe the role of IL-7 and its receptor in immunosenescence, the aging of the immune system. An understanding of the role that IL-7 plays in aging may permit parsimonious preventative or therapeutic solutions for diverse conditions. Perhaps IL-7 might be used to "tune" the immune system to optimize human healthspan and longevity.

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.

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.

Angiogenic gene therapy does not cause retinal pathology

BACKGROUND

The potential negative influence of angiogenic gene therapy on the development or progression of retinal pathologies such as diabetic retinopathy (DR) or age-related macular degeneration (AMD) has led to the systematic exclusion of affected patients from trials. We investigated the role of nonviral fibroblast factor 1 (NV1FGF) in two phase II, multinational, double-blind, randomized, placebo-controlled, gene therapy trials (TALISMAN 201 and 211).

METHODS

One hundred and fifty-two subjects with critical limb ischemia or claudication were randomized to receive eight intramuscular injections of 2.5 ml of NV1FGF at 0.2 mg/ml or 0.4 mg/dl or placebo. One hundred and fifty-two patients received a plasmid dose of NV1FGF of up to 32 mg or placebo. All patients underwent a systematic ophthalmologic examination at baseline and at 3, 6 or 12 months following gene therapy. Twenty-six of these patients (Münster subgroup) received a retinal fluorescence angiography at baseline and at final examination.

RESULTS

Among those 26 patients, four of nine patients with diabetes suffered from nonproliferative DR. Three patients showed non-exsudative AMD. No change of retinal morphology or function was observed in Münster subgroup of both TALISMAN trials independent of the intramuscular NV1FGF dosage applied.

CONCLUSIONS

Angiogenic gene therapy using NV1FGF is safe even in diabetics.

Safety and efficacy of sustained release of basic fibroblast growth factor using gelatin hydrogel in patients with critical limb ischemia

As a form of therapeutic angiogenesis, we sought to investigate the safety and efficacy of a sustained-release system of basic fibroblast growth factor (bFGF) using biodegradable gelatin hydrogel in patients with critical limb ischemia (CLI). We conducted a phase I-IIa study that analyzed 10 CLI patients following a 200-μg intramuscular injection of bFGF-incorporated gelatin hydrogel microspheres into the ischemic limb. Primary endpoints were safety and transcutaneous oxygen pressure (TcO2) at 4 and 24 weeks after treatment. During the follow-up, there was no death or serious procedure-related adverse event. After 24 weeks, TcO2 (28.4 ± 8.4 vs. 46.2 ± 13.0 mmHg for pretreatment vs after 24 weeks, p < 0.01) showed significant improvement. Regarding secondary endpoints, the distance walked in 6 min (255 ± 105 vs. 318 ± 127 m, p = 0.02), the Rutherford classification (4.4 ± 0.5 vs. 3.1 ± 1.4, p = 0.02), the rest pain scale (1.7 ± 1.0 vs. 1.2 ± 1.3, p = 0.03), and the cyanotic scale (2.0 ± 1.1 vs. 0.9 ± 0.9, p < 0.01) also showed improvement. The blood levels of bFGF were within the normal range in all patients. A subanalysis of patients with arteriosclerosis obliterans (n = 7) or thromboangiitis obliterans (Buerger's disease) (n = 3) revealed that TcO2 had significantly improved in both subgroups. TcO2 did not differ between patients with or without chronic kidney disease. The sustained release of bFGF from biodegradable gelatin hydrogel may offer a safe and effective form of angiogenesis for patients with CLI.

Hepatocyte growth factor and Met in drug discovery

Activation of the hepatocyte growth factor (HGF)-Met pathway evokes dynamic biological responses that support the morphogenesis, regeneration and survival of cells and tissues. A characterization of conditional Met knockout mice indicates that the HGF-Met pathway plays important roles in the regeneration, protection and homeostasis of cells such as hepatocytes, renal tubular cells and neurons. Preclinical studies in disease models have indicated that recombinant HGF protein and expression plasmid for HGF are biological drug candidates for the treatment of patients with diseases or injuries that involve impaired tissue function. The phase-I and phase-I/II clinical trials of the intrathecal administration of HGF protein for the treatment of patients with amyotrophic lateral sclerosis and spinal cord injury, respectively, are ongoing. Biological actions of HGF that promote the dynamic movement, morphogenesis and survival of cells also closely participate in invasion-metastasis and resistance to the molecular-targeted drugs in tumour cells. Different types of HGF-Met pathway inhibitors are now in clinical trials for treatment of malignant tumours. Basic research on HGF and Met has lead to drug discoveries in regenerative medicine and tumour biology.

Gene-Activated Matrix Comprised of Atelocollagen and Plasmid DNA Encoding BMP4 or Runx2 Promotes Rat Cranial Bone Augmentation

To date, therapeutic method for in vivo gene delivery has not been established on bone engineering though its potential usefulness has been suggested. For clinical applications, an effective condition should be developed to transfer the genes in vivo without any transfection reagents or virus vectors. In this study, to facilitate the clinical setting of this strategy, particularly aimed at atrophic bone repair, we simply investigated whether manufactured gene-activated matrix (GAM) with atelocollagen containing a certain amount of plasmid (p) DNA encoding osteogenic proteins could augment the cranial bone in rat. GAMs were manufactured by mixing 0.02, 0.1, or 1 mg of AcGFP plasmid vectors harboring cDNA of BMP4 (pBMP4) or Runx2 (pRunx2) with 2% bovine atelocollagen and β-tricalcium phosphate granules. Before manufacturing GAMs, to determine the biological activity of generated pDNAs, we confirmed GFP expression and increased level of alkaline phosphatase activities in MC3T3-E1 cells transfected with pBMP4 or pRunx2 during culture. Then, GAMs were lyophilized and transplanted to onlay placement on the cranium. At 2 weeks of transplantation, GFP-expressing cells could be detectable in only GAMs containing 1 mg of AcGFP plasmid vectors. Then, at 4 weeks, significant bone formation was recognized in GAMs containing 1 mg of pDNAs encoding BMP4 or Runx2 but not in 0.02 or 0.1 mg of GAMs. These newly formed bone tissues surrounded by osteocalcin-stained area were augmented markedly until 8 weeks after transplantation. In contrast, minimal bone formation was observed in GAMs without harboring cDNA of osteogenic proteins. Meanwhile, when GAMs were transplanted to the cranial bone defect, bone formation was detectable in specimens containing 1 mg of pBMP4 or pRunx2 at 8 weeks as well. Thus, atelocollagen-based GAM reliably could form the engineered bone even for the vertical augmentation when containing a certain amount of plasmid vectors encoding osteogenic proteins. This study supports facilitating the clinical application of GAM for bone engineering.

HGF-Met Pathway in Regeneration and Drug Discovery

Hepatocyte growth factor (HGF) is composed of an α-chain and a β-chain, and these chains contain four kringle domains and a serine protease-like structure, respectively. Activation of the HGF–Met pathway evokes dynamic biological responses that support morphogenesis (e.g., epithelial tubulogenesis), regeneration, and the survival of cells and tissues. Characterizations of conditional Met knockout mice have indicated that the HGF–Met pathway plays important roles in regeneration, protection, and homeostasis in various cells and tissues, which includes hepatocytes, renal tubular cells, and neurons. Preclinical studies designed to address the therapeutic significance of HGF have been performed on injury/disease models, including acute tissue injury, chronic fibrosis, and cardiovascular and neurodegenerative diseases. The promotion of cell growth, survival, migration, and morphogenesis that is associated with extracellular matrix proteolysis are the biological activities that underlie the therapeutic actions of HGF. Recombinant HGF protein and the expression vectors for HGF are biological drug candidates for the treatment of patients with diseases and injuries that are associated with impaired tissue function. The intravenous/systemic administration of recombinant HGF protein has been well tolerated in phase I/II clinical trials. The phase-I and phase-I/II clinical trials of the intrathecal administration of HGF protein for the treatment of patients with amyotrophic lateral sclerosis and spinal cord injury, respectively, are ongoing.

Tissue-engineered lymphatic graft for the treatment of lymphedema

BACKGROUND

Lymphedema is a chronic debilitating condition and curative treatment is yet to be found. Tissue engineering approach, which combines cellular components, scaffold, and molecular signals hold great potential in the treatment of secondary lymphedema with the advent of lymphatic graft to reconstruct damaged collecting lymphatic vessel. This review highlights the ideal characteristics of lymphatic graft, the limitation and challenges faced, and the approaches in developing tissue-engineered lymphatic graft.

METHODS

Literature on tissue engineering of lymphatic system and lymphatic tissue biology was reviewed.

RESULTS

The prime challenge in the design and manufacturing of this graft is producing endothelialized conduit with intraluminal valves. Suitable scaffold material is needed to ensure stability and functionality of the construct. Endothelialization of the construct can be enhanced via biofunctionalization and nanotopography, which mimics extracellular matrix. Nanocomposite polymers with improved performance over existing biomaterials are likely to benefit the development of lymphatic graft.

CONCLUSIONS

With the in-depth understanding of tissue engineering, nanotechnology, and improved knowledge on the biology of lymphatic regeneration, the aspiration to develop successful lymphatic graft is well achievable.

Lower extremity amputation in peripheral artery disease: improving patient outcomes

Peripheral artery disease affects over eight million Americans and is associated with an increased risk of mortality, cardiovascular disease, functional limitation, and limb loss. In its most severe form, critical limb ischemia, patients are often treated with lower extremity (LE) amputation (LEA), although the overall incidence of LEA is declining. In the US, there is significant geographic variation in the performing of major LEA. The rate of death after major LEA in the US is approximately 48% at 1 year and 71% at 3 years. Despite this significant morbidity and mortality, the use of diagnostic testing (both noninvasive and invasive testing) in the year prior to LEA is low and varies based on patient, provider, and regional factors. In this review we discuss the significance of LEA and methods to reduce its occurrence. These methods include improved recognition of the risk factors for LEA by clinicians and patients, strong advocacy for noninvasive and/or invasive imaging prior to LEA, improved endovascular revascularization techniques, and novel therapies.

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.

Hepatocyte growth factor as potential cardiovascular therapy

Hepatocyte growth factor is a mesenchyme-derived pleiotropic factor that regulates the growth, motility and morphogenesis of various types of cells, and is also a member of the angiogenic growth factors. Hepatocyte growth factor is secreted by vascular endothelial cells and smooth muscle cells, and the hepatocyte growth factor receptor, c-met, was also observed in these vascular cells. Treatment of human aortic endothelial cells with recombinant hepatocyte growth factor resulted in a significant increase in cell proliferation, accompanied by mitogen-activated protein kinase and Akt/protein kinase B phosphorylation. Recently, a novel therapeutic strategy for ischemic diseases using angiogenic growth factors to augment collateral artery development has been proposed. As preclinical study of gene therapy using hepatocyte growth factor to treat peripheral arterial disease, naked hepatocyte growth factor plasmid was intramuscularly injected into the ischemic hind limb of rabbits in order to evaluate its angiogenic activity. Intramuscular injection of hepatocyte growth factor plasmid once on day 10 following surgery, produced significant augmentation of collateral vessel development in the ischemic limb on day 30. In the clinical setting, the authors further investigated the safety and efficacy of hepatocyte growth factor plasmid DNA in patients with critical limb ischemia, in a prospective open-labeled trial. Intramuscular injection of naked plasmid DNA was performed in the ischemic limbs of six patients with critical limb ischemia with arteriosclerosis obliterans (n = 3) or Buerger disease (n = 3) graded as Fontaine III or IV. In the efficacy evaluation, a reduction of pain scale of more than 1 cm on a visual analog pain scale was observed in five out of six patients. An increase in ankle pressure index of more than 0.1 was observed in five out of five patients. The long diameter of eight out of 11 ischemic ulcers in four patients was reduced by more than 25%. Intramuscular injection of naked hepatocyte growth factor plasmid is safe, feasible and can achieve successful improvement of ischemic limbs. Although the present data were obtained to demonstrate safety in a Phase I/early Phase II trial, the initial clinical outcome with hepatocyte growth factor gene transfer seems to indicate its usefulness as sole therapy for critical limb ischemia. Randomized placebo-controlled clinical trials of alternative dosing regimens of gene therapy will be required to define the efficiency of this therapy.

Postischemic revascularization: from cellular and molecular mechanisms to clinical applications

After the onset of ischemia, cardiac or skeletal muscle undergoes a continuum of molecular, cellular, and extracellular responses that determine the function and the remodeling of the ischemic tissue. Hypoxia-related pathways, immunoinflammatory balance, circulating or local vascular progenitor cells, as well as changes in hemodynamical forces within vascular wall trigger all the processes regulating vascular homeostasis, including vasculogenesis, angiogenesis, arteriogenesis, and collateral growth, which act in concert to establish a functional vascular network in ischemic zones. In patients with ischemic diseases, most of the cellular (mainly those involving bone marrow-derived cells and local stem/progenitor cells) and molecular mechanisms involved in the activation of vessel growth and vascular remodeling are markedly impaired by the deleterious microenvironment characterized by fibrosis, inflammation, hypoperfusion, and inhibition of endogenous angiogenic and regenerative programs. Furthermore, cardiovascular risk factors, including diabetes, hypercholesterolemia, hypertension, diabetes, and aging, constitute a deleterious macroenvironment that participates to the abrogation of postischemic revascularization and tissue regeneration observed in these patient populations. Thus stimulation of vessel growth and/or remodeling has emerged as a new therapeutic option in patients with ischemic diseases. Many strategies of therapeutic revascularization, based on the administration of growth factors or stem/progenitor cells from diverse sources, have been proposed and are currently tested in patients with peripheral arterial disease or cardiac diseases. This review provides an overview from our current knowledge regarding molecular and cellular mechanisms involved in postischemic revascularization, as well as advances in the clinical application of such strategies of therapeutic revascularization.

Clinical application of vascular regenerative therapy for peripheral artery disease

Prognosis of peripheral artery disease (PAD), especially critical limb ischemia, is very poor despite the development of endovascular therapy and bypass surgery. Many patients result in leg amputation and, therefore, vascular regenerative therapy is expected in this field. Gene therapy using vascular endothelial growth factor is the first step of vascular regenerative therapy, but did not confirm effectiveness in a large-scale randomized comparative study. Based on animal experiments, bone marrow mononuclear cells (MNCs), peripheral blood MNCs were used as the cell source for regenerative therapy. Those cells were confirmed to be effective to decrease rest pain and ulcer size, but its effect was not fully satisfied. Mesenchymal stem cells (MSCs) are expected as an effective cell source for vascular regeneration and clinical studies are ongoing, because the cells are able to differentiate into various cell types and produce a significant amount of vascular growth factors. Of vascular regeneration therapy, peripheral MNCs and bone marrow MNCs were recognized as advanced medical technology but do not attain to the standard therapy. However, clinical use of MSCs have already started, and induced pluripotent stem cells are surely promising tool for vascular regeneration therapy although further basic studies are required for clinical application.

Lymphedema and therapeutic lymphangiogenesis

Lymphedema is a disorder of the lymphatic vascular system characterized by impaired lymphatic return and swelling of the extremities. Lymphedema is divided into primary and secondary forms based on the underlying etiology. Despite substantial advances in both surgical and conservative techniques, therapeutic options for the management of lymphedema are limited. Although rarely lethal, lymphedema is a disfiguring and disabling condition with an associated decrease in the quality of life. The recent impressive expansion of knowledge on the molecular mechanisms governing lymphangiogenesis provides new possibilities for the treatment of lymphedema. This review highlights the lymphatic biology, the pathophysiology of lymphedema, and the therapeutic lymphangiogenesis using hepatocyte growth factor.

Kallikrein gene-modified EPCs induce angiogenesis in rats with ischemic hindlimb and correlate with integrin αvβ3 expression

Background

Human tissue kallikrein (hTK) plays an essential role in the physiological and pathological mechanisms of blood vessels. This study aimed to determine whether angiogenesis induced by endothelial progenitor cells (EPCs) transduced with the adenovirus-mediated hTK gene could improve blood flow in rat hindlimb ischemia in vivo and to establish a promising mechanism in vitro.

Methods

EPCs transduced with adenovirus encoding hTK-162 (i.e., Ad/hTK-transduced EPCs or Ad/GFP-transduced EPCs) were administered to Wister rats with hindlimb ischemia through therapeutic neovascularization. Muscular capillary density (MCD), blood flow (BF), and the number of myofibers were measured at days 7, 14, and 21 after treatment. Expressions of integrin αvβ3 and endothelial nitric oxide synthase (eNOS) were detected on the surface of EPCs.

Results

MCD, BF, and the number of myofibers in rats with Ad/hTK-transduced EPCs remarkably increased at day 21 after treatment compared with rats with Ad/GFP-transduced EPCs or the control group (P<0.01). Expressions of integrin αvβ3 and eNOS protein on the surface of EPCs also increased in rats with Ad/hTK-transduced EPCs. The levels of integrin αvβ3 expression were reduced by PI3K and eNOS blockade, and the inhibitor of integrin αvβ3 abrogated the migration and adhesion of hTK-transduced EPCs (P<0.05).

Conclusion

hTK gene delivery in vivo improves the natural angiogenic response to ischemia. The ability of hTK gene-transduced EPCs can be enhanced in vitro, in which integrin αvβ3 plays a role in the process.

Transfection of human hepatocyte growth factor gene inhibits advancing pulmonary arterial hypertension induced by shunt flow in a rabbit model

We investigated gene transfer with human hepatocyte growth factor (HGF) to suppress pulmonary arterial hypertension (PAH) produced by an arteriovenous shunt in a rabbit model. The rabbit model of advanced PAH was used to show that HGF targets pulmonary arteriolar endothelial cells and inhibits disease progression. In the PAH rabbit model transfected with the HGF gene, hemodynamic abnormalities and right ventricular hypertrophy were prevented, as confirmed by invasive measurements and electrocardiographic examinations. In addition to augmented expression of HGF, an increased number of pulmonary arterioles were detected by immunohistochemical analysis. Western Blot and real-time reverse transcriptase-polymerase chain reaction indicated increased protein and mRNA levels of HGF and endothelial nitricoxide synthase (eNOS) in lungs after HGF transfection. Notably, exogenous HGF reduced lung expression of endothelin-1 (ET-1), which was critically involved in PAH-related pathologic changes. Our results suggested that HGF transfection suppresses PAH induced by shunt flow through enhanced expression of HGF with subsequent regulation of the concentrations of eNOS and ET-1 secreted by endothelial cells thereby promoting angiogenesis in injured lung tissue.

Therapeutic angiogenesis in critical limb ischemia

Critical limb ischemia (CLI) is a severe form of peripheral artery disease associated with high morbidity and mortality. The primary therapeutic goals in treating CLI are to reduce the risk of adverse cardiovascular events, relieve ischemic pain, heal ulcers, prevent major amputation, and improve quality of life (QoL) and survival. These goals may be achieved by medical therapy, endovascular intervention, open surgery, or amputation and require a multidisciplinary approach including pain management, wound care, risk factors reduction, and treatment of comorbidities. No-option patients are potential candidates for the novel angiogenic therapies. The application of genetic, molecular, and cellular-based modalities, the so-called therapeutic angiogenesis, in the treatment of arterial obstructive diseases has not shown consistent efficacy. This article summarizes the current status related to the management of patients with CLI and discusses the current findings of the emerging modalities for therapeutic angiogenesis.