Reversal of angiogenic growth factor upregulation by revascularization of lower limb ischemia

From Stress to Sick(le) and Back Again-Oxidative/Antioxidant Mechanisms, Genetic Modulation, and Cerebrovascular Disease in Children with Sickle Cell Anemia

Sickle cell anemia (SCA) is a genetic disease caused by the homozygosity of the HBB:c.20A>T mutation, which results in the production of hemoglobin S (HbS). In hypoxic conditions, HbS suffers autoxidation and polymerizes inside red blood cells, altering their morphology into a sickle shape, with increased rigidity and fragility. This triggers complex pathophysiological mechanisms, including inflammation, cell adhesion, oxidative stress, and vaso-occlusion, along with metabolic alterations and endocrine complications. SCA is phenotypically heterogeneous due to the modulation of both environmental and genetic factors. Pediatric cerebrovascular disease (CVD), namely ischemic stroke and silent cerebral infarctions, is one of the most impactful manifestations. In this review, we highlight the role of oxidative stress in the pathophysiology of pediatric CVD. Since oxidative stress is an interdependent mechanism in vasculopathy, occurring alongside (or as result of) endothelial dysfunction, cell adhesion, inflammation, chronic hemolysis, ischemia-reperfusion injury, and vaso-occlusion, a brief overview of the main mechanisms involved is included. Moreover, the genetic modulation of CVD in SCA is discussed. The knowledge of the intricate network of altered mechanisms in SCA, and how it is affected by different genetic factors, is fundamental for the identification of potential therapeutic targets, drug development, and patient-specific treatment alternatives.

Angiogenic and Microvascular Status Alterations after Endovascular Revascularization of Lower Limb Arteries among Patients with Diabetic Foot Syndrome: A Prospective 12-Month Follow-Up Study

Peripheral arterial disease (PAD)-induced ischemia is an important component of diabetic foot syndrome (DFS). The results of revascularization of the lower extremity arteries (including percutaneous transluminal angioplasty [PTA]) do not always give satisfactory long-term results, which is due to many factors. The aim of the study was to investigate the alterations in selected circulating angiogenic factors and microcirculation parameters in 41 patients with DFS following PTA and analyze their relationships with clinical outcomes during 1-year follow-up. Our study revealed a general decrease in pro-angiogenic factor levels after PTA and their subsequent stabilization during subsequent observation. The results indicated a significant association between plasma circulating FGF-2 level and poor outcomes (including the incidence of restenosis/reocclusion of treated arteries) during 12 months of observation. The perioperative changes in FGF-2 showed a significant association with LDF alterations after PTA. Follow-up 1-3 months post-intervention showed a tendency towards elevated TcpO2, VEGF-A, and VEGF-R2 levels in patients free from adverse events. These results may provide a basis for further research on the potential use of selected circulating angiogenic factors for monitoring the treatment of patients with DFS following PTA.

Limb ischemia and vessel regeneration: Is there a role for VEGF?

Vascular endothelial growth factor (VEGF), as an endothelial cell-specific mitogen, is crucial for new blood vessels formation. Atherosclerosis affecting the cardiovascular system causes ischemia and functio laesa in tissues supplied by the occluded vessels. When such a situation occurs in the lower extremities, it causes critical limb ischemia (CLI) often requiring leg amputation. Low oxygen tension leads to upregulation of hypoxia-regulated genes (i.e. VEGF), that should help to restore the impaired blood flow. In CLI these rescue mechanisms are, however, often inefficient. Moreover, there are many contradictory reports showing either induction, no changes or even down-regulation of VEGF in specimens taken from patients with CLI, as well as in samples collected from animals subjected to hindlimb ischemia. Additionally, taking into account numerous experimental and clinical data demonstrating rather insufficient therapeutic potential of VEGF, we called into question the role of this protein in limb ischemia and vessel regeneration. In this review we are also summarizing several aspects which can influence VEGF expression and its measurement in the ischemic tissues.

Urinary kallidinogenase for the treatment of cerebral arterial stenosis

Aim

Urinary kallidinogenase (UK) has shown promise in improving cerebral perfusion. This study aimed to examine how UK affects cognitive status and serum levels of amyloid betas (Aβs) 1-40 and 1-42 in patients with cerebral arterial stenosis.

Methods

Ninety patients with cerebral arterial stenosis were enrolled, of whom 45 patients received UK + conventional treatment (UK group), and 45 patients received conventional treatment alone as control group. Cognitive status and Aβ1-40 and Aβ1-42 serum levels were determined before treatment and at 4 weeks and 8 weeks after treatment.

Results

At 4 weeks after treatment, cognitive status in patients treated with UK clearly improved accompanied by Aβ1-40 serum levels decreasing while there was no change of Aβ1-42. Cognitive status in patients receiving UK continued to improve, Aβ1-40 serum levels declined further as well as Aβ1-42 serum levels began to decrease dramatically at 8 weeks after treatment.

Conclusion

UK could improve cognitive status and decrease both Aβ1-40 and Aβ1-42 serum levels to prevent ischemic cerebral injury, which represents a good option for patients with cerebral arterial stenosis.

Human Urinary Kallidinogenase Promotes Angiogenesis and Cerebral Perfusion in Experimental Stroke

Angiogenesisis a key restorative mechanism in response to ischemia, and pro-angiogenic therapy could be beneficial in stroke. Accumulating experimental and clinical evidence suggest that human urinary kallidinogenase (HUK) improves stroke outcome, but the underlying mechanisms are not clear. The aim of current study was to verify roles of HUK in post-ischemic angiogenesis and identify relevant mediators. In rat middle cerebral artery occlusion (MCAO) model, we confirmed that HUK treatment could improve stroke outcome, indicated by reduced infarct size and improved neurological function. Notably, the ¹⁸F-FDG micro-PET scan indicated that HUK enhanced cerebral perfusion in rats after MCAO treatment. In addition, HUK promotespost-ischemic angiogenesis, with increased vessel density as well as up-regulated VEGF andapelin/APJ expression in HUK-treated MCAO mice. In endothelial cell cultures, induction of VEGF and apelin/APJ expression, and ERK1/2 phosphorylation by HUK was further confirmed. These changes were abrogated by U0126, a selective ERK1/2 inhibitor. Moreover, F13A, a competitive antagonist of APJ receptor, significantly suppressed HUK-induced VEGF expression. Furthermore, angiogenic functions of HUK were inhibited in the presence of selective bradykinin B1 or B2 receptor antagonist both in vitro and in vivo. Our findings indicate that HUK treatment promotes post-ischemic angiogenesis and cerebral perfusion via activation of bradykinin B1 and B2 receptors, which is potentially due to enhancement expression of VEGF and apelin/APJ in ERK1/2 dependent way.

Mesenchymal stem cell-based HSP70 promoter-driven VEGFA induction by resveratrol promotes angiogenesis in a mouse model

Several studies of stem cell-based gene therapy have indicated that long-lasting regeneration following vessel ischemia may be stimulated through VEGFA gene therapy and/or MSC transplantation for reduction of ischemic injury in limb ischemia and heart failure. The therapeutic potential of MSC transplantation can be further improved by genetically modifying MSCs with genes which enhance angiogenesis following ischemic injury. In the present study, we aimed to develop an approach in MSC-based therapy for repair and mitigation of ischemic injury and regeneration of damaged tissues in ischemic disease. HSP70 promoter-driven VEGFA expression was induced by resveratrol (RSV) in MSCs, and in combination with known RSV biological functions, the protective effects of our approach were investigated by using ex vivo aortic ring coculture system and a 3D scaffolds in vivo model. Results of this investigation demonstrated that HSP promoter-driven VEGFA expression in MSC increased approximately 2-fold over the background VEGFA levels upon HSP70 promoter induction by RSV. Exposure of HUVEC cells to medium containing MSC in which VEGFA had been induced by cis-RSV enhanced tube formation in the treated HUVEC cells. RSV-treated MSC cells differentiated into endothelial-like phenotypes, exhibiting markedly elevated expression of endothelial cell markers. These MSCs also induced aortic ring sprouting, characteristic of neovascular formation from pre-existing vessels, and additionally promoted neovascularization at the MSC transplantation site in a mouse model. These observations support a hypothesis that VEGFA expression induced by cis-RSV acting on the HSP70 promoter in transplanted MSC augments the angiogenic effects of stem cell gene therapy. The use of an inducible system also vastly reduces possible clinical risks associated with constitutive VEGFA expression.

Kinin receptor agonism restores hindlimb postischemic neovascularization capacity in diabetic mice

Limb ischemia is a major complication of thromboembolic diseases. Diabetes worsens prognosis by impairing neovascularization. Genetic or pharmacological inactivation of the kallikrein-kinin system aggravates limb ischemia in nondiabetic animals, whereas angiotensin I-converting enzyme/kininase II inhibition improves outcome. The role of kinins in limb ischemia in the setting of diabetes is not documented. We assessed whether selective activation of kinin receptors by pharmacological agonists can influence neovascularization in diabetic mice with limb ischemia and have a therapeutic effect. Selective pseudopeptide kinin B1 or B2 receptor agonists resistant to peptidase action were administered by osmotic minipumps at a nonhypotensive dosage for 14 days after unilateral femoral artery ligation in mice previously rendered diabetic by streptozotocin. Comparison was made with ligatured, nonagonist-treated nondiabetic and diabetic mice. Diabetes reduced neovascularization, assessed by microangiography and histologic capillary density analysis, by roughly 40%. B1 receptor agonist or B2 receptor agonist similarly restored neovascularization in diabetic mice. Neovascularization in agonist-treated diabetic mice was indistinguishable from nondiabetic mice. Both treatments restored blood flow in the ischemic hindfoot, measured by laser-Doppler perfusion imaging. Macrophage infiltration increased 3-fold in the ischemic gastrocnemius muscle during B1 receptor agonist or B2 receptor agonist treatment, and vascular endothelial growth factor (VEGF) level increased 2-fold. Both treatments increased, by 50-100%, circulating CD45/CD11b-positive monocytes and CD34(+)/VEGFR2(+) progenitor cells. Thus, selective pharmacological activation of B1 or B2 kinin receptor overcomes the effect of diabetes on postischemic neovascularization and restores tissue perfusion through monocyte/macrophage mobilization. Kinin receptors are potential therapeutic targets in limb ischemia in diabetes.

The vascular endothelium and human diseases

Alterations of endothelial cells and the vasculature play a central role in the pathogenesis of a broad spectrum of the most dreadful of human diseases, as endothelial cells have the key function of participating in the maintenance of patent and functional capillaries. The endothelium is directly involved in peripheral vascular disease, stroke, heart disease, diabetes, insulin resistance, chronic kidney failure, tumor growth, metastasis, venous thrombosis, and severe viral infectious diseases. Dysfunction of the vascular endothelium is thus a hallmark of human diseases. In this review the main endothelial abnormalities found in various human diseases such as cancer, diabetes mellitus, atherosclerosis, and viral infections are addressed.

Kallikrein gene transfer induces angiogenesis and further improves regional cerebral blood flow in the early period after cerebral ischemia/reperfusion in rats

AIMS

The aims of this study were to find out whether kallikrein could induce angiogenesis and affect the cerebral blood flow (rCBF) in the early period after cerebral ischemia/reperfusion (CI/R).

METHODS

The adenovirus carried human tissue kallikrein (HTK) gene was administrated into the periinfarction region after CI/R. At 12, 24, and 72 h after treatments, neurological deficits were evaluated; expression of HTK and vascular endothelial growth factor (VEGF) were detected by immunohistochemistry staining; the infarction volume was measured; and rCBF was examined by( 14) C-iodoantipyrine microtracing technique.

RESULTS

The expression of VEGF was enhanced significantly in pAdCMV-HTK group than controls over all time points (P < 0.05). Furthermore, the rCBF in pAdCMV-HTK group increased markedly than controls at 24 and 72 h after treatment (P < 0.05), and the improved neurological deficit was accompanied by reduced infarction volume in pAdCMV-HTK group 24 and 72 h posttreatment.

CONCLUSION

In the early period after CI/R, kallikrein could induce the angiogenesis and improve rCBF in periinfarction region, and further reduce the infarction volume and improve the neurological deficits.

Regenerative therapies for diabetic microangiopathy

Hyperglycaemia occurring in diabetes is responsible for accelerated arterial remodeling and atherosclerosis, affecting the macro- and the microcirculatory system. Vessel injury is mainly related to deregulation of glucose homeostasis and insulin/insulin-precursors production, generation of advanced glycation end-products, reduction in nitric oxide synthesis, and oxidative and reductive stress. It occurs both at extracellular level with increased calcium and matrix proteins deposition and at intracellular level, with abnormalities of intracellular pathways and increased cell death. Peripheral arterial disease, coronary heart disease, and ischemic stroke are the main causes of morbidity/mortality in diabetic patients representing a major clinical and economic issue. Pharmacological therapies, administration of growth factors, and stem cellular strategies are the most effective approaches and will be discussed in depth in this comprehensive review covering the regenerative therapies of diabetic microangiopathy.

Role of human tissue kallikrein in gastrointestinal stromal tumour invasion

BACKGROUND

Human tissue kallikrein (hK1) generates vasodilator kinins from kininogen and promotes angiogenesis by kinin-dependent and kinin-independent mechanisms. Here, we investigate the expression and functional relevance of hK1 in human gastrointestinal stromal tumour (GIST).

METHODS

Vascularisation and hK1 expression of GIST samples were assessed by immunohistochemistry. In two GIST cell lines, hK1 expression was assessed by PCR, and hK1 protein levels and activity were measured by ELISA and an amidolytic assay, respectively. The effect of hK1 silencing, inhibition or overexpression on GIST cell proliferation, migration and paracrine induction of angiogenesis was studied. Finally, local and systemic levels of hK1 were assessed in mice injected with GIST cells.

RESULTS

Human tissue kallikrein was detected in 19 out of 22 human GIST samples. Moreover, GIST cells express and secrete active hK1. Titration of hK1 demonstrated its involvement in GIST invasive behaviour, but not proliferation. Furthermore, hK1 released by GIST cells promoted endothelial cell migration and network formation through kinin-dependent mechanisms. Gastrointestinal stromal tumour implantation in nude mice resulted in local and systemic hK1 expression proportional to tumour dimension.

CONCLUSIONS

Human tissue kallikrein is produced and released by GIST and participates in tumour invasion. Further studies are needed to validate hK1 as a diagnostic biomarker and therapeutic target in GIST.

Does endothelial dysfunction contribute to the clinical status of patients with peripheral arterial disease?

Peripheral arterial disease leads to lower extremity ischemia and limb loss, and is linked to cardiovascular events. The anatomical extent of lower extremity atherosclerosis fails to fully explain ischemic symptoms or predict the development of critical limb ischemia. Endothelial dysfunction is known to contributed to the pathogenesis and clinical expression of coronary artery disease, but the importance of endothelial dysfunction in peripheral arterial disease remains incompletely understood. Endothelial dysfunction could contribute to lower extremity ischemia by impairing blood flow responses to ischemia, collateral formation and arterial remodelling, and by promoting vasospasm, thrombosis, plaque rupture and lesion progression. There is a need for additional studies examining the contribution of endothelial dysfunction to the pathogenesis of peripheral arterial disease, and the potential role of endothelial dysfunction as a surrogate marker with utility in the management of patients.

VEGF: a surrogate marker for peripheral vascular disease

This study aims to evaluate the value of VEGF as a surrogate marker for peripheral vascular disease (PVD). Prior to treatment, serum VEGF levels were evaluated by enzyme-linked immunosorbent assay (ELISA) in 293 PVD patients. Risk factors and clinical parameters of PVD were documented. Twenty-six age-matched healthy volunteers served as controls. Serum VEGF values strongly correlated with Fontaine stages (p<0.006, stage IV vs. controls). High VEGF values prior to treatment were associated with poor outcome. Serum VEGF appears to indicate the severity of PVD and might serve as a surrogate indicator of disease severity.

Effect of training on the response of plasma vascular endothelial growth factor to exercise in patients with peripheral arterial disease

Expansion of the capillary network, or angiogenesis, occurs following endurance training. This process, which is reliant on the presence of VEGF (vascular endothelial growth factor), is an adaptation to a chronic mismatch between oxygen demand and supply. Patients with IC (intermittent claudication) experience pain during exercise associated with an inadequate oxygen delivery to the muscles. Therefore the aims of the present study were to examine the plasma VEGF response to acute exercise, and to establish whether exercise training alters this response in patients with IC. In Part A, blood was collected from patients with IC (n=18) before and after (+20 and +60 min post-exercise) a maximal walking test to determine the plasma VEGF response to acute exercise. VEGF was present in the plasma of patients (45.11+/-29.96 pg/ml) and was unchanged in response to acute exercise. Part B was a training study to determine whether exercise training altered the VEGF response to acute exercise. Patients were randomly assigned to a treatment group (TMT; n=7) that completed 6 weeks of high-intensity treadmill training, or to a control group (CON; n=6). All patients completed a maximal walking test before and after the intervention, with blood samples drawn as for Part A. Training had no effect on plasma VEGF at rest or in response to acute exercise, despite a significant increase in maximal walking time in the TMT group (915+/-533 to 1206+/-500 s; P=0.009) following the intervention. The absence of a change in plasma VEGF may reflect altered VEGF binding at the endothelium, although this cannot be confirmed by the present data.

Therapeutic Arteriogenesis by Ultrasound-Mediated VEGF 165 Plasmid Gene Delivery to Chronically Ischemic Skeletal Muscle

Current methods of gene delivery for therapeutic angiogenesis are invasive, requiring either intraarterial or intramuscular administration. A noninvasive method of gene delivery has been developed using ultrasound-mediated destruction of intravenously administered DNA-bearing carrier microbubbles during their microcirculatory transit. Here we show that chronic ischemia could be markedly improved by ultrasound-mediated destruction of microbubbles bearing vascular endothelial growth factor-165 (VEGF(165)) plasmid DNA. Using a model of severe chronic hindlimb ischemia in rats, we demonstrated that ultrasound mediated VEGF(165)/green fluorescent protein (GFP) plasmid delivery resulted in a significant improvement in microvascular blood flow by contrast-enhanced ultrasound, and an increased vessel density by fluorescent microangiography, with minimal changes in control groups. The improvement in tissue perfusion was attributed predominantly to increases in noncapillary blood volume or arteriogenesis, with perfusion peaking at 14 days after delivery, followed by a partial regression of neovascularization at 6 weeks. Transfection was localized predominantly to the vascular endothelium of arterioles in treated ischemic muscle. RT-PCR confirmed the presence of VEGF(165)/GFP mRNA within treated ischemic muscle, being highest at day 3 postdelivery, and subsequently decreasing, becoming almost undetectable by 6 weeks. We found a modulation of endogenous growth factor expression in VEGF-treated ischemic muscle, consistent with a biologic effect of ultrasound mediated gene delivery. The results of our study demonstrate the utility of ultrasonic destruction of plasmid-bearing microbubbles to induce therapeutic arteriogenesis in the setting of severe chronic ischemia.

Therapeutic angiogenesis: Translating experimental concepts to medically relevant goals

Angiogenesis is central to many physiological and pathological phenomena. In physiological angiogenesis, new vessels are well shaped and their growth is finely tuned to match the metabolic needs of tributary tissues. Accordingly, neovascularization is activated by physical exercise and destabilized by non-use. In contrast, pathological blood vessels that are observed in retinal neovascularization, cancer or in ischemic tissues are leaky, irregularly shaped, and tend to form arterial-venous fistulae. A great deal of attention is focused on new approaches for medical manipulation of vascular growth. These methods are aimed at facilitating the reperfusion of ischemic tissues or eradicating pathological vasculature. In this position paper, we challenge the rationale of therapeutic angiogenesis for the cure of myocardial and peripheral ischemia. Therapeutic angiogenesis aims at combating the insufficiency of, or insensitivity to angiogenic factors in the setting of atherosclerotic-induced arterial occlusion. However, clinical evidence indicates that such a defect is not common among patients with ischemic disease, as a whole. Genetic and environmental factors could account for the great heterogeneity in the expression of the master angiogenic factors. Future improvements in the strategy would require the introduction of in vitro assays and in vivo imaging systems for assessing human angiogenesis. Finally, the promise is to find individualized angiogenesis-based therapies for a genuine cure of ischemia and prevention of organ failure.

Cardioprotective mechanisms of the kallikrein-kinin system in diabetic cardiopathy

PURPOSE OF REVIEW

Multiple pathogenic mechanisms contribute to the development of diabetic cardiopathy, including intramyocardial inflammation, cardiac fibrosis, abnormal intracellular Ca handling, microangiopathy and endothelial dysfunction. Moreover, the cardiac kallikrein-kinin system is thought to be altered under diabetic conditions and an improvement of this peptide system, e.g. by gene therapeutic approaches, has also been associated with an amelioration of the diabetic heart. In this review, we will discuss the hypothesis that the stimulation of the kallikrein-kinin system could be a promising target for the treatment of diabetic cardiopathy.

RECENT FINDINGS

The kallikrein-kinin system has cardioprotective properties, which may be particularly important under diabetic conditions. For example, its potential for endothelium-dependent vasodilation, and for improvement of glucose transport and utilization, make bradykinin an important mediator for reducing the consequences of diabetes-related oxidative stress on both the myocardium and vessels.

SUMMARY

The different synergistic cardioprotective effects of the kallikrein-kinin system in the diabetic heart suggest that the stimulation of the kallikrein-kinin system might open new avenues for the treatment of diabetic cardiopathy.

Changing the logic of therapeutic angiogenesis for ischemic disease

The worldwide epidemic of ischemic disease urgently requires innovative treatments. Recently, therapeutic angiogenesis has emerged as a noninvasive supply-side approach, aimed at promoting neovascularization in underperfused tissues through the local delivery of angiogenic growth factors. Successful preclinical studies paved the way for the first clinical trials, with single growth factors given as recombinant proteins or genes. However, clinical results have not matched the initial promises. Our opinion is that the logic of therapeutic angiogenesis needs profound revision. Here, we introduce the concept that pleiotropic agents can stimulate the healing of all the components of ischemic tissue. We also propose prophylactic interventions to delay vascular senescence. The optimization of therapeutic angiogenesis will open unprecedented opportunities for the care of life-threatening ischemic disease.

Marriage of resistance and conduit arteries breeds critical limb ischemia

Atherosclerosis in a major leg artery leads to impaired blood supply, which normally progresses to critical limb ischemia. Atherosclerosis produces substantial alterations of structure and endothelial function in the large conduit arteries. Pressure unloading and ischemia in the distal vasculature bring about alterations in microvascular function. Resistance arteries undergo significant wall thinning and changes in their contractile regulation. Optimization of large artery dimensions by the small arteries through flow-mediated vasodilation is impaired. Angiogenesis is stimulated, which can result in the formation of major collateral feeder vessels in addition to small nutritive blood vessels. However, angiogenesis can also contribute to instability of atherosclerotic plaques, which ultimately leads to further deterioration in blood supply. Surgical bypass grafting to restore blood supply to the distal leg generates a sudden increase of pressure in the weakened resistance vasculature, leading to uncontrolled changes in capillary hydrostatic pressure, extravasation of fluid, and tissue edema. This review aims to highlight the importance of the resistance vasculature in critical limb ischemia and the interdependence of pathophysiological changes in the large conduit and small resistance arteries. The major unresolved question is why the physiological mechanisms that regulate vascular structure and function ultimately break down, leading to circulatory failure within the distal limb.

Increased circulating levels of tissue kallikrein in systemic sclerosis correlate with microvascular involvement

BACKGROUND

In systemic sclerosis (SSc) the lack of an angiogenic response to hypoxia may be due to inappropriate synthesis of angiogenic and angiostatic factors. Tissue kallikrein (t-kallikrein), regulating the kallikrein-kinin system and acting on the microcirculation, is a potent angiogenic agent, and kallistatin is its natural inhibitor.

OBJECTIVE

To evaluate, in patients with SSc, t-kallikrein and kallistatin levels and their correlation with clinical features and measures of microvascular involvement.

PATIENTS AND METHODS

Serum levels of t-kallikrein and kallistatin (ELISA) and t-kallikrein skin expression (immunohistochemistry) were studied in patients with SSc, and evaluated for subset (dSSc or lSSc), clinical and immunological features, and microvascular involvement (ulcers, telangiectasias, nailfold videocapillaroscopy).

RESULTS

Circulating levels of t-kallikrein were higher in SSc than in controls (p<0.001). T-kallikrein did not differ between lSSc and dSSc, although it was higher in lSSc than in controls (p<0.001).T-kallikrein levels were higher in patients with early and active capillaroscopic pattern than in those with late pattern (p = 0.019 and 0.023). Patients with giant capillaries and capillary microhaemorrhages had higher t-kallikrein concentrations than patients with architectural derangement (p = 0.04). No differences in kallistatin levels were detected between patients with SSc and controls, or between lSSc and dSSc. In early SSc skin, the presence of t-kallikrein was found in endothelial and in perivascular inflammatory cells, while no staining in skin of advanced SSc was detected.

CONCLUSION

T-kallikrein levels are increased in patients with SSc, particularly in lSSc, and are associated with early and active capillaroscopic patterns. T-kallikrein may play a part in SSc microvascular changes.

Dual Effect of Angiotensin-Converting Enzyme Inhibition on Angiogenesis in Type 1 Diabetic Mice

OBJECTIVE

We analyzed the beneficial therapeutic effect of angiotensin converting enzyme inhibitor (ACEI) on both retinal and hind limb neovascularization in diabetic mice.

METHODS AND RESULTS

Diabetic mice (streptozotocin, 40 mg/kg) were treated with or without ACEI (Perindopril, 3 mg/kg per day) or AT1 receptor blocker (Candesartan, 20 mg/kg) for 4 months. Hind limb ischemia was then induced by right femoral artery ligature for 1 additional month. In the ischemic leg, angiographic score, capillary density, and foot perfusion were increased by 2.7, 2.0-fold, and 1.6-fold, respectively, in ACEI-treated diabetic mice compared with untreated diabetic animals (P<0.01). ACEI also raised vascular endothelial growth factor (VEGF) protein level by 1.4-fold in ischemic diabetic leg. This ACEI pro-angiogenic effect was totally blunted in diabetic bradykinin B2 receptor-deficient animals, suggesting that it was mediated by the bradykinin pathway. In the diabetic retina, angiotensinogen and ACE mRNA levels were increased by 2.8-fold and 4.1-fold, respectively (P<0.01 versus nondiabetic mice), highlighting a local activation of renin-angiotensin system. Diabetes also raised VEGF protein level by 1.5-fold (P<0.05 versus nondiabetic mice). Treatments with ACEI and AT1 receptor blocker hampered diabetes-induced VEGF upregulation and retinal neovascularization.

CONCLUSIONS

ACE inhibition improved neovascularization in the diabetic ischemic leg through activation of bradykinin signaling, whereas it reduced vessel growth in the diabetic retina through inhibition of overacting Ang II pathway.

Akt/Protein Kinase B and Endothelial Nitric Oxide Synthase Mediate Muscular Neovascularization Induced by Tissue Kallikrein Gene Transfer

Background— Angiogenesis gene therapy with human tissue kallikrein (hTK) has shown promise for ischemic disease. The present study was undertaken to (1) assess an optimal gene transfer modality, (2) clarify hTK angiogenic pathways, and (3) discount possible side effects.

Methods and Results— The hTK gene was transferred to murine adductors by increasing doses of an adenovirus (Ad.hTK). Heterologous protein production was evaluated by ELISA and immunohistochemistry. Structural and functional characteristics of hTK-induced neovascularization were assessed. Muscular endothelial nitric oxide synthase (eNOS) and vascular endothelial growth factor (VEGF)-A mRNA and protein content were evaluated by real-time polymerase chain reaction and Western blotting. The ability of hTK to phosphorylate-activate Akt/protein kinase B (Akt-B) and VEGF receptor 2 (VEGF-R2) was also determined. Implication of the aforementioned mechanisms in Ad.hTK-induced neovascularization was challenged by blocking Akt-B with a dominant-negative Akt construct; NOS with N G -nitro- l -arginine methyl ester; and VEGF-A with neutralizing antibody, VEGF-R2 antagonist, or Ad carrying soluble VEGF-R1 gene. We found that 10 7 PFU Ad.hTK led to peak increases in capillary and arteriole density. Newly developed arterioles persisted for up to 8 weeks. Ad.hTK did not change microvascular permeability. Ad.hTK upregulated eNOS mRNA and protein and activated Akt-B through Ser-473 phosphorylation. Inhibitory studies documented that these biochemical events were instrumental to Ad.hTK-induced neovascularization. In contrast, Ad.hTK neither affected VEGF-A and VEGF-R2 levels nor increased VEGF-R2 phosphorylation. Consistently, Ad.hTK-induced neovascularization was not disturbed by any of the different approaches used to block VEGF-A.

Conclusions— Our findings provide new information on the pathway involved in hTK-induced neoangiogenesis and represent an advancement toward clinical applications with Ad.hTK.

Circulating Tissue Kallikrein Levels Correlate With Severity of Carotid Atherosclerosis

Background— Vascular growth factors are upregulated in stroke patients, but it remains unknown if they correlate with carotid atherosclerosis.

Methods and Results— A case-control study was conducted to determine: (1) possible association between biomarkers of angiogenesis or inflammation and carotid stenosis; and (2) the impact of revascularization on the same biomarkers. Circulating vascular endothelial growth factor (VEGF), basic fibroblast GF (bFGF), tissue kallikrein (tK), and high-sensitivity C-reactive protein (hs-CRP) were measured in 89 patients with carotid obstruction and 45 age-matched controls. Patients were stratified as <50% carotid stenosis (CAS; n=16); 50% to 69% CAS (n=12); 70% to 99% CAS (n=43); and carotid occlusion (CAO; n=18). No association was found between VEGF, bFGF, or hs-CRP and obstruction grading. TK augmented from 360±30 in <50% CAS ( P =NS versus controls) to 509±72 in moderate CAS ( P <0.05), 1159±178 in high-grade CAS ( P <0.02), and 1616±403 pg/mL in CAO ( P <0.01). A threshold of 508 pg/mL provided the maximized predictive value of high-grade obstruction. After revascularization, tK decreased from 1410±352 to 782±86 pg/mL ( P <0.01), whereas no change was detected in nonoperated cases. Hs-CRP was unaffected by revascularization.

Conclusions— Angiogenic factors are heterogeneously expressed in patients with carotid atherosclerosis. The tK measurement may be useful for the diagnosis and monitoring of atherosclerotic disease.

Preclinical models of human peripheral arterial occlusive disease: implications for investigation of therapeutic agents

Peripheral arterial occlusive disease (PAOD) is now recognized as a combination of clinical syndromes that are associated with significant morbidity and mortality. The primary pathophysiology of PAOD is impaired perfusion to the lower extremity. Effective pharmacotherapy designed to increase perfusion in PAOD is lacking, and revascularization options are suboptimal. New and more efficacious therapies that improve blood flow are definitely needed, and thus designing, describing, and validating these new therapies in preclinical PAOD models will be essential. This study describes the various preclinical PAOD models presently in use, correlates the models to human PAOD, and reviews the available end points that can be used to detect a response to therapy.

Branching out: a molecular fingerprint of endothelial differentiation into tube-like structures generated by Affymetrix oligonucleotide arrays

The process of endothelial differentiation into a network of tube-like structures with patent lumens requires an integrated program of gene expression. To identify genes upregulated in endothelial cells during the process of tube formation, RNA was prepared from several different time points (0, 4, 8, 24, 40, and 48 hours) and from three different experimental models of human endothelial tube formation: in collagen gels and fibrin gels driven by the combination of PMA (80), bFGF (40 ng/ml) and bFGF (40 ng/ml) or in collagen gels driven by the combination of HGF (40 ng/ml) and VEGF (40 ng/ml). Gene expression was evaluated using Affymetrix Gene Chip oligonucleotide arrays. Over 1000 common genes were upregulated greater than twofold over baseline at one or more time points in the three different models. In the present study, we discuss the identified genes that could be assigned to major functional classes: apoptosis, cytoskeleton, proteases, matrix, and matrix turnover, pumps and transporters, membrane lipid turnover, and junctional molecules or adhesion proteins.

Prevention of diabetes-induced microangiopathy by human tissue kallikrein gene transfer

BACKGROUND

Microvascular insufficiency represents a major cause of end-organ failure among diabetics.

METHODS AND RESULTS

In streptozotocin-induced diabetic mice, we evaluated the potential of human tissue kallikrein (hTK) gene as a sole therapy against peripheral microangiopathy. Local delivery of hTK gene halted the progression of microvascular rarefaction in hindlimb skeletal muscle by inhibiting apoptosis, thus ensuring an improved hemodynamic recovery in case of supervening vascular occlusion. The curative action of hTK did not necessitate insulin supplementation. Application of gene therapy at a stage of established microangiopathy stimulated vascular regeneration.

CONCLUSIONS

Our studies indicate that hTK may represent a useful tool for the treatment of microvascular complications in diabetics.