Effect of fibroblast growth factor NV1FGF on amputation and death: a randomised placebo-controlled trial of gene therapy in critical limb ischaemia

Five-Year Outcome of Self-Expanding Covered Stents for Superficial Femoral Artery Occlusive Disease and an Analysis of Factors Predicting Failure

Purpose: To investigate the 5-year outcome of patients treated with self-expanding covered stents for superficial femoral artery (SFA) occlusive disease and identify parameters that could predict loss of primary patency. Methods: In a dual-center study, 315 consecutive patients (mean age 69.0±10.1 years; 232 men) treated for SFA occlusive disease in 334 limbs with Viabahn self-expanding covered stents between 2001 and 2014 were retrospectively analyzed. Mean lesion length was 11.7±8.8 cm, and half of the lesions were classified as TASC II C/D. Five-year patency rates were calculated, and Cox regression analyses were performed to assess potential factors affecting patency. Results: All-cause mortality at 5 years was 14.1%. Primary patency rates at 1, 3, and 5 years were 72.2%, 51.8%, and 47.6%, respectively, with secondary patency rates of 86.2%, 78.7%, and 77.5%. Parameters predicting loss of primary patency in a univariate analysis were covered stent diameter (p=0.001), the number of covered stents per lesion (p=0.015), and TASC II D classification (p=0.007). Covered stent diameter was the only parameter predicting loss of primary patency in the multivariate regression analysis (p=0.001), with 7-mm covered stents having superior performance. Conclusion: Five-year patency rates of self-expanding covered stents inserted for SFA occlusive disease are within an acceptable range. Covered stent diameter is the most relevant factor in predicting loss of primary patency, and thus, an adequate diameter of the distal landing site seems to be among the most important factors in the decision-making process. In smaller vessels, one should not use covered stents but venous conduits, as oversizing may be detrimental.

Fibroblast growth factors in cardiovascular disease: The emerging role of FGF21

Early detection of risk factors for enhanced primary prevention and novel therapies for treating the chronic consequences of cardiovascular disease are of the utmost importance for reducing morbidity. Recently, fibroblast growth factors (FGFs) have been intensively studied as potential new molecules in the prevention and treatment of cardiovascular disease mainly attributable to metabolic effects and angiogenic actions. Members of the endocrine FGF family have been shown to increase metabolic rate, decrease adiposity, and restore glucose homeostasis, suggesting a multiple metabolic role. Serum levels of FGFs have been associated with established cardiovascular risk factors as well as with the severity and extent of coronary artery disease and could be useful for prediction of cardiovascular death. Furthermore, preclinical investigations and clinical trials have tested FGF administration for therapeutic angiogenesis in ischemic vascular disease, demonstrating a potential role in improving angina and limb function. FGF21 has lately emerged as a potent metabolic regulator with multiple effects that ultimately improve the lipoprotein profile. Early studies show that FGF21 is associated with the presence of atherosclerosis and may play a protective role against plaque formation by improving endothelial function. The present review highlights recent investigations suggesting that FGFs, in particular FGF21, may be useful as markers of cardiovascular risk and may also serve as protective/therapeutic agents in cardiovascular disease.

The role of FGF2 in migration and tubulogenesis of endothelial progenitor cells in relation to pro-angiogenic growth factor production

In recent years, special attention has been paid to finding new pro-angiogenic factors which could be used in gene therapy of vascular diseases such as critical limb ischaemia (CLI). Angiogenesis, the formation of new blood vessels, is a complex process dependent on different cytokines, matrix proteins, growth factors and other pro- or anti-angiogenic stimuli. Numerous lines of evidence suggest that key mediators of angiogenesis, vascular endothelial growth factor (VEGF) and hepatocyte growth factor (HGF) together with fibroblast growth factor2 (FGF2) are involved in regulation of the normal and pathological process of angiogenesis. However, less information is available on the complex interactions between these and other angiogenic factors. The aim of this study was to characterise the effect of fibroblast growth factor2 on biological properties of human endothelial progenitor cells with respect to the expression level of other regulatory cytokines. Ectopic expression of FGF2 in EP cells stimulates their pro-angiogenic behaviour, leading to increased proliferation, migration and tube formation abilities. Moreover, we show that the expression profile of VEGF and other pro-angiogenic cytokines, such as HGF, MCP2, and interleukins, is affected differently by FGF2 in EPC. In conclusion, we provide evidence that FGF2 directly affects not only the biological properties of EP cells but also the expression pattern and secretion of numerous chemocytokines. Our results suggest that FGF2 could be applied in therapeutic approaches for CLI and other ischaemic diseases of the vascular system in vivo.

Impact of cardiovascular risk factors on severity of peripheral artery disease

OBJECTIVE

The development of peripheral artery disease is affected by the presence of cardiovascular risk factors. It is unclear, whether particular risk factors are leading to different clinical stages of peripheral artery disease. The aim of this retrospective cross-sectional study was to assess the association of cardiovascular risk factors with the presence of critical limb ischaemia.

METHODS

The study cohort was derived from a consecutive registry of patients undergoing endovascular therapy in a tertiary referral centre between January 2000 and April 2014. Patients undergoing first-time endovascular intervention for chronic peripheral artery disease of the lower extremities were included. Univariate and multivariate logistic regression models were used to assess the association of age, sex, diabetes mellitus, hypertension, dyslipidaemia, smoking, and renal insufficiency with critical limb ischaemia vs. intermittent claudication.

RESULTS

A total of 3406 patients were included in the study (mean age 71.7 ± 11.8 years, 2075 [61%] male). There was a significant association of age (OR 1.67, 95%-CI 1.53-1.82, p < 0.001), male gender (OR 1.23, 95%-CI 1.04-1.47, p = 0.016), diabetes (OR 1.99, 95%-CI 1.68-2.36, p < 0.001) and renal insufficiency (OR 1.62, 95%-CI 1.35-1.96, p < 0.001) with the likelihood of critical limb ischaemia. Smoking was associated with intermittent claudication rather than critical limb ischaemia (OR 0.78, 95%-CI 0.65-0.94, p = 0.010), while hypertension and dyslipidaemia did not show an association with critical limb ischaemia.

CONCLUSIONS

In peripheral artery disease patients undergoing first-time endovascular treatment, age, male gender, diabetes, and renal insufficiency were the strongest predictors for the presence of critical limb ischaemia.

Fucoidan Stimulates Monocyte Migration via ERK/p38 Signaling Pathways and MMP9 Secretion

Critical limb ischemia (CLI) induces the secretion of paracrine signals, leading to monocyte recruitment and thereby contributing to the initiation of angiogenesis and tissue healing. We have previously demonstrated that fucoidan, an antithrombotic polysaccharide, promotes the formation of new blood vessels in a mouse model of hindlimb ischemia. We examined the effect of fucoidan on the capacity of peripheral blood monocytes to adhere and migrate. Monocytes negatively isolated with magnetic beads from peripheral blood of healthy donors were treated with fucoidan. Fucoidan induced a 1.5-fold increase in monocyte adhesion to gelatin (p < 0.05) and a five-fold increase in chemotaxis in Boyden chambers (p < 0.05). Fucoidan also enhanced migration 2.5-fold in a transmigration assay (p < 0.05). MMP9 activity in monocyte supernatants was significantly enhanced by fucoidan (p < 0.05). Finally, Western blot analysis of fucoidan-treated monocytes showed upregulation of ERK/p38 phosphorylation. Inhibition of ERK/p38 phosphorylation abrogated fucoidan enhancement of migration (p < 0.01). Fucoidan displays striking biological effects, notably promoting monocyte adhesion and migration. These effects involve the ERK and p38 pathways, and increased MMP9 activity. Fucoidan could improve critical limb ischemia by promoting monocyte recruitment.

Generating induced pluripotent stem cell derived endothelial cells and induced endothelial cells for cardiovascular disease modelling and therapeutic angiogenesis

Standard therapy for atherosclerotic coronary and peripheral arterial disease is insufficient in a significant number of patients because extensive disease often precludes effective revascularization. Stem cell therapy holds promise as a supplementary treatment for these patients, as pre-clinical and clinical research has shown transplanted cells can promote angiogenesis via direct and paracrine mechanisms. Induced pluripotent stem cells (iPSCs) are a novel cell type obtained by reprogramming somatic cells using exogenous transcription factor cocktails, which have been introduced to somatic cells via viral or plasmid constructs, modified mRNA or small molecules. IPSCs are now being used in disease modelling and drug testing and are undergoing their first clinical trial, but despite recent advances, the inefficiency of the reprogramming process remains a major limitation, as does the lack of consensus regarding the optimum transcription factor combination and delivery method and the uncertainty surrounding the genetic and epigenetic stability of iPSCs. IPSCs have been successfully differentiated into vascular endothelial cells (iPSC-ECs) and, more recently, induced endothelial cells (iECs) have also been generated by direct differentiation, which bypasses the pluripotent intermediate. IPSC-ECs and iECs demonstrate endothelial functionality in vitro and have been shown to promote neovessel growth and enhance blood flow recovery in animal models of myocardial infarction and peripheral arterial disease. Challenges remain in optimising the efficiency, safety and fidelity of the reprogramming and endothelial differentiation processes and establishing protocols for large-scale production of clinical-grade, patient-derived cells.

Association of the Derived Neutrophil-Lymphocyte Ratio With Critical Limb Ischemia

Neutrophil and leukocyte counts are laboratory parameters that reflect the systemic inflammatory response in patients with atherosclerotic diseases. Based on the means of these parameters, the derived neutrophil-lymphocyte ratio (dNLR) can be calculated. We investigated a possible association of critical limb ischemia (CLI) and the dNLR in patients with peripheral arterial disease (PAD). We performed a retrospective data analysis including 1995 patients with PAD treated at our department in the years 2005 to 2010. The cohort was divided into tertiles according to dNLR. Higher dNLR values were associated with an increased CLI rate. In the tertile with lowest dNLR, the CLI rate was 20.4%, in the second tertile the CLI rate was 26.1%, and in the third tertile the CLI rate was 36.1%. Statistical significance was shown using a Jonckheere-Terpstra test (P < .001). A high dNLR is associated with an increased rate of CLI in patients with PAD. This might be a useful parameter to highlight patients at increased risk of CLI.

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.

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.

pCMV-vegf165 Intramuscular Gene Transfer is an Effective Method of Treatment for Patients With Chronic Lower Limb Ischemia

Effective treatment of chronic lower limb ischemia is one of the most challenging issues confronting vascular surgeons. There are a number of choices available to the vascular surgeon. Open or endovascular revascularization is the treatment of choice when applicable. Current pharmacological therapies play an auxiliary role and cannot prevent disease progression. Therefore, new methods of treatment are needed. We conducted a phase 2b/3 multicenter randomized controlled clinical trial of the intramuscular transfer of a plasmid DNA encoding vascular endothelial growth factor (VEGF) 165 with cytomegalovirus promotor (CMV) in patients with atherosclerotic lower limb ischemia. A total of 100 patients were enrolled in the study, that is, 75 patients were randomized into the test group and received 2 intramuscular injections of 1.2 mg of pCMV-vegf165, 14 days apart together with standard pharmacological treatment. In all, 25 patients were randomized into the control group and received standard treatment only. The following end points were evaluated within the first 6 months of the study and during a 1.5-year additional follow-up period: pain-free walking distance (PWD), ankle-brachial index (ABI), and blood flow velocity (BFV). The pCMV-vegf165 therapy appeared to be significantly more effective than standard treatment. The PWD increased in the test group by 110.4%, 167.2%, and 190.8% at 6 months, 1 year, and 2 years after treatment, respectively. The pCMV-vegf165 intramuscular transfer caused a statistically significant increase in ABI and BFV. There were no positive results in the control group. Thus, pCMV-vegf165 intramuscular gene transfer is an effective method of treatment of moderate to severe claudication due to chronic lower limb ischemia.

Under-reporting of venous and arterial thrombotic events in randomized clinical trials: a meta-analysis

For the detection of unwanted outcomes of new interventions, physicians rely on adverse event reporting. We attempt to quantify the reported incidence of venous thromboembolism (VTE) and arterial thrombosis (AT) in randomized clinical trials (RCTs), and evaluate the extent of under-reporting. We selected all therapeutic RCTs published in the four highest-impact general medicine journals between January 2011 and July 2011. Patients were categorized according to VTE risk. The occurrences of VTE and AT, either as predefined outcome or adverse event, were assessed. We identified 131 RCTs. VTE and AT were not reported in 89 and 70 % of these studies, respectively. The raw-unweighted reported incidence in the 3 studies with predefined outcomes for VTE was 8.4 (7.8-9.1) per 1,000 person-years. In the 128 studies without predefined outcomes for VTE, (consisting of 322,029 individuals, including patients with cancer, inflammatory disease, cardiovascular disease, surgery, adding up to a follow-up >500,000 person-years), an incidence of 0.4 (0.4-0.5) per 1,000 person-years was found. The reported incidence of AT in 18 studies in which AT was part of predefined outcomes was 25.6 (24.9-26.3) per 1,000 person-years. In 92 studies without predefined outcomes for AT (231,638 individuals, follow-up >200,000 person-years,), the incidence was 2.5 (2.3-2.7) per 1,000 person-years. The incidence of VTE and AT in RCTs is highly under-reported. Uniform registration of adverse events, even when unlikely to be related to the intervention, is necessary to be able to inform physicians about the potential toxicities of new therapeutic strategies.

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.

Current Phase II drugs under investigation for the treatment of limb ischemia

INTRODUCTION

More than 20 million people in Europe suffer from peripheral arterial disease and nearly 3% develop critical limb ischemia (CLI). Without any medical treatment, CLI has poor prognosis, resulting in limb loss and high mortality rate. Until today, no systemic drug is available for the treatment of CLI and the gold standard method of treatment includes risk factor modification and open surgical or endovascular revascularization. Endovascular local drug delivery devices and novel antithrombotic agents, currently under investigation, aim to improve outcomes of revascularization procedures. The pioneering concept of therapeutic angiogenesis induced by gene and stem cell therapy has been proposed, in an attempt to increase ischemic tissue perfusion.

AREAS COVERED

This review summarizes local and systemic pharmacological treatment of CLI using endovascular or pharmaco-biological therapy and focuses on Phase II trials available for these drugs.

EXPERT OPINION

Novel endovascular technologies combining angioplasty and local drug-delivery continuously improve and will come to be standard of practice for the management of limb ischemia, while new antithrombotic agents will further improve outcomes. Therapeutic angiogenesis represents a safe and promising treatment option. The combination of revascularization with microcirculation improvement induced by gene or stem cell therapy could enhance limb salvage.

Drug-eluting balloon versus standard balloon angioplasty for infrapopliteal arterial revascularization in critical limb ischemia: 12-month results from the IN.PACT DEEP randomized trial

BACKGROUND

Drug-eluting balloons (DEB) may reduce infrapopliteal restenosis and reintervention rates versus percutaneous transluminal angioplasty (PTA) and improve wound healing/limb preservation.

OBJECTIVES

The goal of this clinical trial was to assess the efficacy and safety of IN.PACT Amphirion drug-eluting balloons (IA-DEB) compared to PTA for infrapopliteal arterial revascularization in patients with critical limb ischemia (CLI).

METHODS

Within a prospective, multicenter, randomized, controlled trial with independent clinical event adjudication and angiographic and wound core laboratories 358 CLI patients were randomized 2:1 to IA-DEB or PTA. The 2 coprimary efficacy endpoints through 12 months were clinically driven target lesion revascularization (CD-TLR) and late lumen loss (LLL). The primary safety endpoint through 6 months was a composite of all-cause mortality, major amputation, and CD-TLR.

RESULTS

Clinical characteristics were similar between the 2 groups. Significant baseline differences between the IA-DEB and PTA arms included mean lesion length (10.2 cm vs. 12.9 cm; p = 0.002), impaired inflow (40.7% vs. 28.8%; p = 0.035), and previous target limb revascularization (32.2% vs. 21.8%; p = 0.047). Primary efficacy results of IA-DEB versus PTA were CD-TLR of 9.2% versus 13.1% (p = 0.291) and LLL of 0.61 ± 0.78 mm versus 0.62 ± 0.78 mm (p = 0.950). Primary safety endpoints were 17.7% versus 15.8% (p = 0.021) and met the noninferiority hypothesis. A safety signal driven by major amputations through 12 months was observed in the IA-DEB arm versus the PTA arm (8.8% vs. 3.6%; p = 0.080).

CONCLUSIONS

In patients with CLI, IA-DEB had comparable efficacy to PTA. While primary safety was met, there was a trend towards an increased major amputation rate through 12 months compared to PTA. (Study of IN.PACT Amphirion™ Drug Eluting Balloon vs. Standard PTA for the Treatment of Below the Knee Critical Limb Ischemia [INPACT-DEEP]; NCT00941733).

Bilateral administration of autologous CD133+ cells in ambulatory patients with refractory critical limb ischemia: lessons learned from a pilot randomized, double-blind, placebo-controlled trial

BACKGROUND AIMS

CD133+ cells confer angiogenic potential and may be beneficial for the treatment of critical limb ischemia (CLI). However, patient selection, blinding methods and end points for clinical trials are challenging. We hypothesized that bilateral intramuscular administration of cytokine-mobilized CD133+ cells in ambulatory patients with refractory CLI would be feasible and safe.

METHODS

In this double-blind, randomized sham-controlled trial, subjects received subcutaneous injections of granulocyte colony-stimulating factor (10 μg/kg per day) for 5 days, followed by leukapheresis, and intramuscular administration of 50-400 million sorted CD133+ cells delivered into both legs. Control subjects received normal saline injections, sham leukapheresis and intramuscular injection of placebo buffered solution. Subjects were followed for 1 year. An aliquot of CD133+ cells was collected from each subject to test for genes associated with cell senescence.

RESULTS

Seventy subjects were screened, of whom 10 were eligible. Subject enrollment was suspended because of a high rate of mobilization failure in subjects randomly assigned to treatment. Of 10 subjects enrolled (7 randomly assigned to treatment, 3 randomly assigned to control), there were no differences in serious adverse events at 12 months, and blinding was preserved. There were non-significant trends toward improved amputation-free survival, 6-minute walk distance, walking impairment questionnaire and quality of life in subjects randomly assigned to treatment. Successful CD133+ mobilizers expressed fewer senescence-associated genes compared with poor mobilizers.

CONCLUSIONS

Bilateral administration of autologous CD133+ cells in ambulatory CLI subjects was safe, and blinding was preserved. However, poor mobilization efficiency combined with high CD133+ senescence suggests futility in this approach.

Transcutaneous oxygen tension measurements following peripheral transluminal angioplasty procedure has more specificity and sensitivity than ankle brachial index

OBJECTIVE

To evaluate the superiority of transcutaneous oxygen pressure (TcPO2) before, during and after peripheral transluminal angioplasty (PTA) in comparison with ankle brachial index (ABI) in patients with diabetes.

METHODS

40 consecutive patients with diabetes treated by PTA where included. This study shows results before, during and after PTA and their progression for 8 weeks.

RESULTS

The TcPO2 increased from 28.11 ± 8.1 to 48.03 ± 8.4 mmHg, 8 weeks after PTA (p < 0.001). The ABI increased from 0.48 ± 0.38 to 0.77 ± 0.39 after PTA (p < 0.001). After PTA, the stenosis of the vessel decreased from 58.33 ± 20.07% to 21.87 ± 13.57% (p < 0.001). TcPO2 was determined in all the patients, but ABI could not be determined in all patients. Furthermore, we determined patients with "false negatives" with an improvement in ABI and "false positives" in 12.5% of patients. Additionally, in this study, we monitored TcPO2 while performing PTA, revealing variations in each phase of the radiological procedure.

CONCLUSION

The increase in TcPO2 measurements following PTA procedure has more specificity and sensitivity than does ABI. The use of TcPO2 may represent a more accurate alternative than traditional methods (ABI) used in assessing PTA results. The TcPO2 also allows the radiologist to assess changes in tissue oxygenation during PTA, allowing changes to the procedure and subsequent treatment.

ADVANCES IN KNOWLEDGE

This is the first time that a graph is shown with TcPO2 results during PTA performance in many patients.

Deletion of prolyl hydroxylase domain proteins (PHD1, PHD3) stabilizes hypoxia inducible factor-1 alpha, promotes neovascularization, and improves perfusion in a murine model of hind-limb ischemia

BACKGROUND

There is an emerging focus on investigating innovative therapeutic molecules that can potentially augment neovascularization in order to treat peripheral arterial disease (PAD). Although prolyl hydroxylase domain proteins 1 and 3 (PHD1 and PHD3) may modulate angiogenesis via regulation of hypoxia inducible factor-1α (HIF-1α), there has been no study directly addressing their roles in ischemia-induced vascular growth. We hypothesize that PHD1(-/-) or PHD3(-/-) deficiency might promote angiogenesis in the murine hind-limb ischemia (HLI) model.

STUDY DESIGN

Wild type (WT), PHD1(-/-) and PHD3(-/-) male mice aged 8-12weeks underwent right femoral artery ligation. Post-procedurally, motor function assessment and laser Doppler imaging were periodically performed. The mice were euthanized after 28days and muscles were harvested. Immunohistochemical analysis was performed to determine the extent of angiogenesis by measuring capillary and arteriolar density. VEGF expression was quantified by enzyme-linked immunosorbent assay (ELISA). Bcl-2 and HIF-1α were analyzed by immunofluorescence. Fibrosis was measured by picrosirius red staining.

RESULTS

PHD1(-/-) and PHD3(-/-) mice showed significantly improved recovery of perfusion and motor function score when compared to WT after femoral artery ligation. These mice also exhibited increased capillary and arteriolar density, capillary/myocyte ratio along with decreased fibrosis compared to WT. VEGF, Bcl-2 and HIF-1α expression increased in PHD1(-/-) and PHD3(-/-) mice compared to WT.

CONCLUSIONS

Taken together these results suggest that PHD1 and PHD3 deletions promote angiogenesis in ischemia-injured tissue, and may present a promising therapeutic strategy in treating PAD.

Chronic critical ischaemia of the legs

Chronic critical ischaemia of the lower limb is the most severe form of peripheral arterial occlusive disease. It is characterised by acral rest pain and an ankle arterial pressure <50 mmHg and a toe arterial pressure of <30 mmHg for at least two weeks. If trophic lesions are present, then an ankle pressure <70 mmHg and a toe pressure < 50 mmHg are already sufficient for diagnosis of chronic critical ischaemia. The aim of treatment is limb preservation and a reduction in the cardiovascular mortality and morbidity. For this to be achieved, the time to diagnosis and the time to revascularisation must be as short as possible. It is therefore important that patients with foot pain at rest undergo angiological work-up as rapidly as possible, especially if they also have risk factors for critical ischaemia (diabetes, renal failure). The same applies to patients with trophic skin lesions (fissure, ulcer) that do not heal within three weeks.

Revascularisation is the most important therapeutic measure. Inhibition of platelet aggregation, optimum analgesia and early use of antibiotics if signs of an infection are present, are further important measures in addition to the treatment of cardiovascular risk factors. Amputation is the last therapeutic option.

What can I do with a patient with diabetes and critically impaired limb perfusion who cannot be revascularized?

A patient with limb-threatening diabetic foot syndrome in whom relevant peripheral arterial occlusive disease is proven should receive arterial revascularization as soon as possible to avoid major amputation. However, 3 conditions may make it impossible to effectively restore limb perfusion: the patient will not profit from arterial revascularization owing to excessive tissue loss or sepsis ("too late"), the patient cannot be revascularized due to severe comorbidities ("too sick"), and arterial reconstruction is impossible because of technical and anatomical shortcomings in a patient who is otherwise fit for operation ("nonreconstructible limb perfusion"). This review outlines the therapeutic options specifically in the third group of patients in whom no technical option for surgical or endovascular revascularization exists.

Non-mitogenic form of acidic fibroblast growth factor protects against graft-versus-host disease without accelerating leukemia

Acid fibroblast growth factor (aFGF) has been shown to prevent epithelial damage under various conditions, suggesting its potential to inhibit GVHD. However, because aFGF receptors are expressed on tumor cells, it may possibly offset the graft-vs.-tumor (GVT) effects of allogeneic bone marrow transplantation (allo-BMT). Here, we addressed these questions in a B6→B6D2F1 allo-BMT model. Although aFGF administration attenuated GVHD in non-leukemic recipients, aFGF treatment markedly accelerated death in mice that received recipient-type tumor (P815) cells along with allo- or syngeneic-BMT. Similar protection against GVHD was achieved by administration of a non-mitogenic form of aFGF (naFGF). Importantly, GVT effects were fully preserved in naFGF-treated recipients. Furthermore, aFGF, but not naFGF, significantly enhanced P815 cell proliferation both in vitro and in vivo. Our data indicate that the tumor-promoting, but not GVHD-protecting, effect of aFGF largely depends on its mitogenic activity, and suggest that naFGF may provide a safer approach to inhibiting GVHD in patients with malignancies.

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.

Biochemical and immunomorphological evaluation of hepatocyte growth factor and c-Met pathway in patients with critical limb ischemia

OBJECTIVES

Hepatocyte growth factor (HGF), the c-Met receptor, and hypoxia-inducible factor (HIF) are crucial for regenerative processes including ischemic wound healing. The aims of the present study are (a) to analyze the tissue c-Met and HIF-1α expression in skin from patients with critical limb ischemia (CLI); (b) to compare the serum HGF levels of CLI and control subjects.

METHODS

This is a prospective, controlled, single-center study. Thirty-seven patients were enrolled. A skin sample adjacent to the ischemic lesion was taken from 20 patients with CLI; skin samples were taken from the surgical wounds of 17 patients surgically treated for abdominal aortic aneurysm as healthy controls. Serum samples were taken in all cases. Samples were formalin fixed, paraffin embedded, and routinely processed. Tissue inflammation was histologically assessed. Immunohistochemistry was performed with antibodies against total c-Met receptor, activated Met (p-Met), and HIF-1α. RT-polymerase chain reaction was used to quantify HIF-1α mRNA. The enzyme-linked immunosorbent assay was performed to evaluate serum HGF levels.

RESULTS

With immunohistochemistry, while total c-Met was unchanged, different patterns of p-Met positivity were observed between CLI and control cases (p < .001). In particular, CLI skin showed a total negativity or membrane positivity for p-Met (19/20 cases), while control skin mainly showed cytoplasmic positivity in the epidermal basal layer (16/17 cases). HIF-1α was diffusely lost in CLI, but HIF-1α mRNA was threefold higher than in controls. Finally, mean serum HGF levels were 590.5 pg/mL and 2380.0 pg/mL in CLI and control groups respectively (p < .001).

CONCLUSIONS

In CLI patients a significant decrease in serum HGF levels, concomitant with a loss of skin HIF-1α stabilization and a lack of c-Met phosphorylation were seen, probably driving a decrease in wound-healing functions. The next hypothesis is that HGF application might reactivate the c-Met receptor, stabilizing the normal wound healing process.

Clinical Effectiveness of Gene Therapy on Critical Limb Ischemia

Therapeutic angiogenesis using gene therapy is a novel strategy for the treatment of critical limb ischemia (CLI). We conducted a meta-analysis to evaluate the efficacy and safety of gene therapy for the treatment of CLI with no option of revascularization. Randomized placebo controlled trials of gene therapy on CLI were identified by searching PubMed (from 1990 to October 2013) and EMBASE (from 1990 to October 2013). Five eligible studies were selected for the meta-analysis. Among these studies, a total of 425 patients received gene therapy of either fibroblast growth factor 1 or hepatocyte growth factor, and 365 patients were given placebo. No statistical differences were observed between the 2 groups in major amputation or death at 1 year (risk ratio [RR], 0.83; 95% confidence interval [CI], 0.51-1.39; P = .48) and wound healing at 6 months (RR, 1.55; 95% CI, 0.73-3.28; P = .25). Gene therapy had similar occurrence of serious adverse events as control (RR, 1.05; 95% CI, 0.97-1.14; P = .23).

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.

A Network Map of FGF-1/FGFR Signaling System

Fibroblast growth factor-1 (FGF-1) is a well characterized growth factor among the 22 members of the FGF superfamily in humans. It binds to all the four known FGF receptors and regulates a plethora of functions including cell growth, proliferation, migration, differentiation, and survival in different cell types. FGF-1 is involved in the regulation of diverse physiological processes such as development, angiogenesis, wound healing, adipogenesis, and neurogenesis. Deregulation of FGF-1 signaling is not only implicated in tumorigenesis but also is associated with tumor invasion and metastasis. Given the biomedical significance of FGFs and the fact that individual FGFs have different roles in diverse physiological processes, the analysis of signaling pathways induced by the binding of specific FGFs to their cognate receptors demands more focused efforts. Currently, there are no resources in the public domain that facilitate the analysis of signaling pathways induced by individual FGFs in the FGF/FGFR signaling system. Towards this, we have developed a resource of signaling reactions triggered by FGF-1/FGFR system in various cell types/tissues. The pathway data and the reaction map are made available for download in different community standard data exchange formats through NetPath and NetSlim signaling pathway resources.

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.

Potential Vascular Mechanisms of Ramipril Induced Increases in Walking Ability in Patients With Intermittent Claudication

Rationale:

We recently reported that ramipril more than doubled maximum walking times in patients with peripheral artery disease with intermittent claudication.

Objective:

Our aim was to conduct exploratory analyses of the effects of ramipril therapy on circulating biomarkers of angiogenesis/arteriogenesis, thrombosis, inflammation, and leukocyte adhesion in patients with intermittent claudication.

Methods and Results:

One hundred sixty-five patients with intermittent claudication (mean, 65.3 [SD, 6.7] years) were administered ramipril 10 mg per day (n=82) or matching placebo (n=83) for 24 weeks in a randomized, double-blind study. Plasma biomarkers of angiogenesis/arteriogenesis (vascular endothelial growth factor-A, fibroblast growth factor-2), thrombosis (D-dimer, von Willebrand factor, thrombin-antithrombin III), inflammation (high-sensitivity C-reactive protein, osteopontin), and leukocyte adhesion (soluble vascular cell adhesion molecule-1, soluble intracellular adhesion molecule-1) were measured at baseline and 24 weeks. Relative to placebo, ramipril was associated with increases in vascular endothelial growth factor-A by 38% (95% confidence interval [CI], 34%–42%) and fibroblast growth factor-2 by 64% (95% CI, 44–85%; P <0.001 for both), and reductions in D-dimer by 24% (95% CI, −30% to −18%), von Willebrand factor by 22% (95% CI, −35% to −9%), thrombin-antithrombin III by 16% (95% CI, −19% to −13%), high-sensitivity C-reactive protein by 13% (95% CI, −14% to −9%), osteopontin by 12% (95% CI, −14% to −10%), soluble vascular cell adhesion molecule-1 by 14% (95% CI, −18% to −10%), and soluble intracellular adhesion molecule-1 by 15% (95% CI, −17% to −13%; all P <0.001). With the exception of von Willebrand factor, all the above changes correlated significantly with the change in maximum walking time ( P =0.02−0.001) in the group treated with ramipril.

Conclusions:

Ramipril is associated with an increase in the biomarkers of angiogenesis/arteriogenesis and reduction in the markers of thrombosis, inflammation, and leukocyte adhesion. This study informs strategies to improve mobility in patients with intermittent claudication.

Clinical Trial Registration Information:

URL: http://clinicaltrials.gov . Unique identifier: NCT00681226.

Casein kinase 1 regulates Sprouty2 in FGF-ERK signaling

Sprouty2 (SPRY2) is a potent negative regulator of receptor tyrosine kinase signaling, and is implicated as a tumor suppressor. SPRY2 inhibits FGF-RAS-ERK signaling by binding to growth factor receptor bound protein 2 (GRB2) during fibroblast growth factor receptor (FGFR) activation, disrupting the GRB2-SOS (son of sevenless) complex that transduces signals from FGFR to RAS. SPRY2 binding to GRB2 is modulated by phosphorylation but the key regulatory kinase(s) are not known. Prior studies identified the frequent presence of CK1 phosphorylation motifs on SPRY2. We therefore tested if CK1 has a role in SPRY2 phosphorylation and function. Loss of CK1 binding and inhibition of CK1 activity by two structurally distinct small molecules abrogated SPRY2 inhibition of FGF-ERK signaling, leading to decreased SPRY2 interaction with GRB2. Moreover, CK1 activity and binding are necessary for SPRY2 inhibition of FGF-stimulated neurite outgrowth in PC12 cells. Consistent with its proposed role as an inhibitor of FGF signaling, we find that CSNK1E transcript abundance negatively correlates with FGF1/FGF7 message in human gastric cancer samples. Modulation of CK1 activity may be therapeutically useful in the treatment of FGF/SPRY2-related diseases.

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.

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.

A phase I study of human cord blood-derived mesenchymal stem cell therapy in patients with peripheral arterial occlusive disease

BACKGROUND AND OBJECTIVES

Half of patients with critical limb ischemia (CLI) are ineligible for revascularization at diagnosis. The aim of this study was to assess the safety and feasibility of intramuscular human umbilical cord blood-derived mesenchymal stem cell (hUCB-MSC) therapy in patients with CLI due to atherosclerosis obliterans (ASO) or thromboangiitis obliterans (TAO).

METHODS AND RESULTS

A total of eight patients (all male, median age 52 years, range 31∼77) with CLI were enrolled in this phase I trial. All patients were considered ineligible for further revascularization to improve CLI. We injected 1×10(7) hUCB-MSCs per single dose intramuscularly into the affected limb. The primary end points of safety were occurrence of adverse events (procedure-related complication, allergic reaction to hUCB-MSCs, graft-versus-host disease, cardiovascular and cerebrovascular events) and improvement of symptoms/clinical parameters (healing of foot ulcer, ankle-brachial index, and pain-free walking distance). Angiogenesis was measured with conventional angiography and scored by an independent reviewer. There were four adverse events in three patients. One patient, developed whole body urticaria after injection on treatment day, which disappeared after one day of antihistamine treatment. The other adverse events included diarrhea, oral ulceration, and elevation of serum creatinine level; all conditions improved without treatment. Abnormal results of laboratory parameters were not detected in any patients. Three of four ulcerations (75%) healed completely. Angiographic scores increased in three of eight patients.

CONCLUSIONS

This phase I study demonstrates that intramuscular hUCB-MSC injection is a safe and well tolerated treatment for patients with end-stage CLI due to ASO and TAO.

Updating on understanding and managing chronic wound

The art of healing wounds is quite complex. It requires the patient's local condition in conjunction with their systemic condition to provide the most ideal wound environment. As wound care is expanding with advances in technology, we are facing a variety of different wound care products based on an assortment of bioengineered skin substances, growth factors, oxygen therapies, low frequency ultrasound and even low energy light. While these emerging evidence-based treatments prove to be promising in improving clinical outcomes and quality of life, it challenges providers to provide cost-effective treatment plans. The goal of this paper is to introduce a discussion regarding practical clinical application of various forms of advanced wound technologies in order to optimize the art of wound healing.

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.

Overcoming disease-induced growth factor resistance in therapeutic angiogenesis using recombinant co-receptors delivered by a liposomal system

Current treatment options for ischemia include percutaneous interventions, surgical bypass or pharmacological interventions aimed at slowing the progression of vascular disease. Unfortunately, while each of these treatment modalities provides some benefit for patients in the short-term, many patients have resistant or recurrent disease that is poorly managed by these therapies. A highly appealing strategy for treating ischemic disease is to stimulate the revascularization of the tissue to restore blood flow. While many techniques have been explored in this regard, clinically effective angiogenic therapies remain elusive. Here, we hypothesized that the presence of co-morbid disease states inherently alters the ability of the body to respond to angiogenic therapies. Using a mouse model of diabetes and obesity, we examined alterations in the major components for the signaling pathways for FGF-2, VEGF-A and PDGF under normal and high fat dietary conditions. In skeletal muscle, a high fat diet increased levels of growth factor receptors and co-receptors including syndecan-1, syndecan-4 and PDGFR-α in wild-type mice. These increases did not occur in Ob/Ob mice on a high fat diet and there was a significant decrease in protein levels for neuropilin-1 and heparanase in these mice. With the aim of increasing growth factor effectiveness in the context of disease, we examined whether local treatment with alginate gel-delivered FGF-2 and syndecan-4 proteoliposomes could overcome the growth factor resistance in these mice. This treatment enhanced the formation of new blood vessels in Ob/Ob mice by 6 fold in comparison to FGF-2 delivered alone. Our studies support that disease states cause a profound shift in growth factor signaling pathways and that co-receptor-based therapies have potential to overcome growth factor resistance in the context of disease.

Medical management of critical limb ischaemia: where do we stand today?

Critical limb ischaemia (CLI) is a severe form of peripheral arterial disease (PAD). CLI often causes disabling symptoms of pain and can lead to loss of the affected limb. It is also associated with increased risk of myocardial infarction, stroke and death from cardiovascular disease. The aims of management in patients with CLI are to relieve ischaemic pain, heal ulcers, prevent limb loss, improve function and quality of life and prolong survival. Here, current evidence regarding the medical management of CLI is reviewed. Cardiovascular risk factors should be assessed in all patients with CLI; smoking cessation and treatment of hypertension, hyperlipidaemia and diabetes all reduce the mortality rate in those with PAD. Antiplatelet agents (either aspirin or clopidogrel) are recommended to reduce both the incidence of cardiovascular events and risk of arterial occlusion. By contrast, routine use of anticoagulation (either warfarin or heparin) is not recommended. Treatment of the limbs themselves is often more challenging. Prostanoids may have some efficacy for treating rest pain and for ulcer healing, and iloprost shows favourable results in reducing the risk of major amputations, but long-term follow-up data regarding disease progression are lacking. There is insufficient evidence to support the use of naftidrofuryl or cilostazol, and pentoxifylline is not beneficial. Furthermore, there is no evidence of proven benefit of hyperbaric oxygen. A number of angiogenic growth factors have been studied in Phase I studies and randomized controlled trials (RCTs). They appear to be safe, but efficacy results have been mixed. Treatment with stem cells also shows some potential from early trials, but further larger RCTs are needed to demonstrate clear benefit. Thrombolysis may be an alternative for patients who develop acute limb ischaemia and are unsuitable for surgical intervention. However, newer endovascular techniques are likely to have a greater role in the future.

Secretoneurin gene therapy improves blood flow in an ischemia model in type 1 diabetic mice by enhancing therapeutic neovascularization

Deficient angiogenesis after ischemia may contribute to worse outcome of peripheral arterial disease in patients with diabetes mellitus. Based on our previous work where we demonstrated that Secretoneurin (SN) is up-regulated under hypoxic conditions and enhances angiogenesis, we analyzed the therapeutic potential of SN gene therapy using a model of severe hind limb ischemia in streptozotocin-induced diabetic mice (STZ-DM). After induction of hind limb ischemia, blood flow was assessed by means of laser Doppler perfusion imaging (LDPI) and increased blood perfusion in the SN-treated animal group was observed. These results were complemented by the clinical observation of reduced necrosis and by an increased number of capillaries and arterioles in the SN-treated animal group. In vitro, we found that SN is capable of promoting proliferation and chemotaxis and reduces apoptosis in HUVECs cultured under hyperglycemic conditions. Additionally, SN activated ERK, eNOS and especially AKT as well as EGF-receptor in hyperglycemic HUVECs. In conclusion, we show that SN gene therapy improves post-ischemic neovascularization in diabetic mice through stimulation of angiogenesis and arteriogenesis indicating a possible therapeutic role of this factor in ischemia-related diseases in diabetic patients.

Characterization of mesenchymal stem cells of "no-options" patients with critical limb ischemia treated by autologous bone marrow mononuclear cells

Background

Application of autologous bone marrow mononuclear cells to “no option” patients with advanced critical limb ischemia (CLI) prevented major limb amputation in 73% patients during the 6-month follow-up. We examined which properties of bone marrow stromal cells also known as bone-marrow derived mesenchymal stem cells of responding and non-responding patients are important for amputation-free survival.

Methods and Findings

Mesenchymal stem cells of 41 patients with CLI unsuitable for revascularisation were isolated from mononuclear bone marrow concentrate used for their treatment. Based on the clinical outcome of the treatment, we divided patients into two groups: responders and non-responders. Biological properties of responders’ and non-responders’ mesenchymal stem cells were characterized according to their ability to multiply, to differentiate invitro, quantitative expression of cell surface markers, secretion of 27 cytokines, chemokines and growth factors, and to the relative expression of 15 mesenchymal stem cells important genes. Secretome comparison between responders (n=27) and non-responders (n=14) revealed significantly higher secretion values of IL-4, IL-6 and MIP-1b in the group of responders. The expression of cell markers CD44 and CD90 in mesenchymal stem cells from responders was significantly higher compared to non-responders (p<0.01). The expression of mesenchymal stem cells surface markers that was analyzed in 22 patients did not differ between diabetic (n=13) and non-diabetic (n=9) patient groups. Statistically significant higher expression of E-cadherin and PDX-1/IPF1 genes was found in non-responders, while expression of Snail was higher in responders.

Conclusions

The quality of mesenchymal stem cells shown in the expression of cell surface markers, secreted factors and stem cell genes plays an important role in therapeutic outcome. Paracrine mechanisms are main drivers in the induction of reparatory processes in CLI patients. Differences in mesenchymal stem cells properties are discussed in relation to their involvement in the reparatory process.

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.

Therapeutics targeting angiogenesis: genetics and epigenetics, extracellular miRNAs and signaling networks (Review)

Angiogenesis is a process of neovascular formation from pre-existing blood vessels, which consists of sequential steps for vascular destabilization, angiogenic sprouting, lumen formation and vascular stabilization. Vascular endothelial growth factor (VEGF), fibroblast growth factor (FGF), angiopoietin, Notch, transforming growth factor-β (TGF-β), Hedgehog and WNT signaling cascades orchestrate angiogenesis through the direct or indirect regulation of quiescence, migration and the proliferation of endothelial cells. Small-molecule compounds and human/humanized monoclonal antibodies interrupting VEGF signaling have been developed as anti-angiogenic therapeutics for cancer and neovascular age-related macular degeneration (AMD). Gene or protein therapy delivering VEGF, FGF2 or FGF4, as well as cell therapy using endothelial progenitor cells (EPCs), mesenchymal stem cells (MSCs) or induced pluripotent stem cells (iPSCs) have been developed as pro-angiogenic therapeutics for ischemic heart disease and peripheral vascular disease. Anti-angiogenic therapy for cancer and neovascular AMD is more successful than pro-angiogenic therapy for cardiovascular diseases, as VEGF-signal interruption is technically feasible compared with vascular re-construction. Common and rare genetic variants are detected using array-based technology and personal genome sequencing, respectively. Drug and dosage should be determined based on personal genotypes of VEGF and other genes involved in angiogenesis. As epigenetic alterations give rise to human diseases, polymer-based hydrogel film may be utilized for the delivery of drugs targeting epigenetic processes and angiogenesis as treatment modalities for cardiovascular diseases. Circulating microRNAs (miRNAs) in exosomes and microvesicles are applied as functional biomarkers for diagnostics and prognostics, while synthetic miRNAs in polymer-based nanoparticles are applicable for therapeutics. A more profound understanding of the spatio-temporal interactions of regulatory signaling cascades and advances in personal genotyping and miRNA profiling are required for the optimization of targeted therapy.

From bench to bedside: review of gene and cell-based therapies and the slow advancement into phase 3 clinical trials, with a focus on Aastrom's Ixmyelocel-T

There is a large body of preclinical research demonstrating the efficacy of gene and cellular therapy for the potential treatment of severe (limb-threatening) peripheral arterial disease (PAD), including evidence for growth and transcription factors, monocytes, and mesenchymal stem cells. While preclinical research has advanced into early phase clinical trials in patients, few late-phase clinical trials have been conducted. The reasons for the slow progression of these therapies from bench to bedside are as complicated as the fields of gene and cellular therapies. The variety of tissue sources of stem cells (embryonic, adult bone marrow, umbilical cord, placenta, adipose tissue, etc.); autologous versus allogeneic donation; types of cells (hematopoietic, mesenchymal stromal, progenitor, and mixed populations); confusion and stigmatism by the public and patients regarding gene, protein, and stem cell therapy; scaling of manufacturing; and the changing regulatory environment all contribute to the small number of late phase (Phase 3) clinical trials and the lack of Food and Drug Administration (FDA) approvals. This review article provides an overview of the progression of research from gene therapy to the cellular therapy field as it applies to peripheral arterial disease, as well as the position of Aastrom's cellular therapy, ixmyelocel-T, within this field.

TIE2-expressing monocytes/macrophages regulate revascularization of the ischemic limb

A third of patients with critical limb ischemia (CLI) will eventually require limb amputation. Therapeutic neovascularization using unselected mononuclear cells to salvage ischemic limbs has produced modest results. The TIE2-expressing monocytes/macrophages (TEMs) are a myeloid cell subset known to be highly angiogenic in tumours. This study aimed to examine the kinetics of TEMs in patients with CLI and whether these cells promote neovascularization of the ischemic limb. Here we show that there are 10-fold more circulating TEMs in CLI patients, and removal of ischemia reduces their numbers to normal levels. TEM numbers in ischemic muscle are two-fold greater than normoxic muscle from the same patient. TEMs from patients with CLI display greater proangiogenic activity than TIE2-negative monocytes in vitro. Using a mouse model of hindlimb ischemia, lentiviral-based Tie2 knockdown in TEMs impaired recovery from ischemia, whereas delivery of mouse macrophages overexpressing TIE2, or human TEMs isolated from CLI patients, rescued limb ischemia. These data suggest that enhancing TEM recruitment to the ischemic muscle may have the potential to improve limb neovascularization in CLI patients.

Meta-analysis of contemporary short- and long-term mortality rates in patients diagnosed with critical leg ischaemia

BACKGROUND

Critical leg ischaemia (CLI) has been associated with high mortality rates. There is a lack of contemporary data on both short- and long-term mortality rates in patients diagnosed with CLI.

METHODS

This was a systematic literature search for studies prospectively reporting mortality in patients diagnosed with CLI. Meta-analysis and meta-regression models were developed to determine overall mortality rates and specific patient-related factors that were associated with death.

RESULTS

A total of 50 studies were included in the analysis The estimated probability of all-cause mortality in patients with CLI was 3·7 per cent at 30 days, 17·5 per cent at 1 year, 35·1 per cent at 3 years and 46·2 per cent at 5 years. Men had a statistically significant survival benefit at 30 days and 3 years. The presence of ischaemic heart disease, tissue loss and older age resulted in a higher probability of death at 3 years.

CONCLUSION

Early mortality rates in patients diagnosed with CLI have improved slightly compared with previous historical data, but long-term mortality rates are still high.

Angiogenic cytokines in renovascular disease: do they have potential for therapeutic use?

Experimental and clinical studies suggest that the damage of the renal microvascular function and architecture may participate in the early steps of renal injury in chronic renal disease, irrespective of the cause. This supporting evidence has provided the impetus to targeting the renal microvasculature as an attempt to interfere with the progressive nature of the disease process. Chronic renovascular disease is often associated with renal microvascular dysfunction, damage, loss, and defective renal angiogenesis associated with progressive renal dysfunction and damage. It is possible that damage of the renal microvasculature in renovascular disease constitutes an initiating event for renal injury and contributes towards progressive and later on irreversible renal injury. Recent studies have suggested that protection of the renal microcirculation can slow or halt the progression of renal injury in this disease. This brief review will focus on the therapeutic potential and feasibility of using angiogenic cytokines to protect the kidney microvasculature in chronic renovascular disease. There is limited but provocative evidence showing that stimulation of vascular proliferation and repair using vascular endothelial growth factor or hepatocyte growth factor can slow the progression of renal damage, stabilize renal function, and protect the renal parenchyma. Such interventions may potentially constitute a sole strategy to preserve renal function and/or a co-adjuvant tool to improve the success of current therapeutic approaches in renovascular disease.

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

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