Endothelin Receptor Blockade Improves Cerebral Blood Flow-Mediated Dilation in a Mouse Model of Alzheimer's Disease

INTRODUCTION

Cerebral blood flow (CBF) is reduced in patients with Alzheimer's disease (AD). Flow-mediated dilation (FMD), which plays a key role in the regulation of blood flow, is attenuated by endothelin-1. We hypothesized that endothelin receptor blockade may improve CBF in AD.

METHODS

We investigated cerebrovascular reactivity in a mouse model of AD (APP-PS1; 5-6-month-old male subjects). We assessed the in vivo response to normoxic hypercapnia and in vitro FMD in isolated cerebral and mesenteric resistance arteries before and after endothelin receptor blockade (bosentan).

RESULTS

Normoxic hypercapnia increased basilar trunk blood flow velocity (+12.3 ± 2.4%; p = 0.006, n = 6) in wild-type (WT) mice but reduced blood flow in APP-PS1 mice (-11.4 ± 1.2%; p < 0.0001, n = 8). Bosentan (50 mg/kg, acute intraperitoneal injection) restored cerebrovascular reactivity in APP-PS1 mice (+10.2 ± 2.2%; p < 0.0001, n = 8) but had no effect in WT. FMD was reduced in the posterior cerebral artery of APP-PS1 compared to WT and was normalized by bosentan (1 μmol/L, 30 min, or 50 mg/kg/day for 28 days). FMD was similar in the mesenteric artery of APPS-PS1 and WT.

CONCLUSION

APP-PS1 mice exhibited cerebrovascular endothelial dysfunction. Acute and chronic blockade of endothelin receptors restored endothelial vasomotor function, suggesting a promising therapeutic approach to restoring cerebral vasoreactivity in AD.

Renin Angiotensin Blockers and Cardiac Protection: From Basis to Clinical Trials

Despite a similar beneficial effect on blood pressure lowering observed with angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin II type 1 receptor (AT1R) blocker (ARBs), several clinical trials and meta-analyses have reported higher cardiovascular mortality and lower protection against myocardial infarction with ARBs when compared with ACEIs. The European guidelines for the management of coronary syndromes and European guidelines on diabetes recommend using ARBs in patients who are intolerant to ACEIs. We reviewed the main pharmacological differences between ACEIs and ARBs, which could provide insights into the differences in the cardiac protection offered by these 2 drug classes. The effect of ACEIs on the tissue and plasma levels of bradykinin and on nitric oxide production and bioavailability is specific to the mechanism of action of ACEIs; it could account for the different effects of ACEIs and ARBs on endothelial function, atherogenesis, and fibrinolysis. Moreover, chronic blockade of AT1 receptors by ARBs induces a significant and permanent increase in plasma angiotensin II and an overstimulation of its still available receptors. In animal models, AT4 receptors have vasoconstrictive, proliferative, and inflammatory effects. Moreover, in models with kidney damage, atherosclerosis, and/or senescence, activation of AT2 receptors could have deleterious fibrotic, vasoconstrictive, and hypertrophic effects and seems prudent and reasonable to reserve the use of ARBs for patients who have presented intolerance to ACE inhibitors.

Renin-angiotensin system blockers and severe acute respiratory syndrome coronavirus 2

Severe acute respiratory syndrome coronavirus 2, which is responsible for the current coronavirus disease 2019 pandemic, uses angiotensin-converting enzyme 2 as a gateway into host cells. In this review, we summarise the biology of this enzyme, which plays a key role in cardiovascular homeostasis. Blockers of the renin–angiotensin system modify the expression and activity of angiotensin-converting enzyme 2 in different ways. The effects of angiotensin-converting enzyme inhibitors and angiotensin receptor blockers on the expression and enzyme activity of angiotensin-converting enzyme 2 are reviewed, and the consequences of these treatments for the severity of coronavirus disease 2019 infection are discussed.

High Systolic Blood Pressure Induces Cerebral Microvascular Endothelial Dysfunction, Neurovascular Unit Damage, and Cognitive Decline in Mice

A chronic and gradual increase in pulse pressure (PP) is associated with cognitive decline and dementia in older individuals, but the mechanisms remain ill-defined. We hypothesized that a chronic elevation of PP would cause brain microvascular endothelial mechanical stress, damage the neurovascular unit, and ultimately induce cognitive impairment in mice, potentially contributing to the progression of vascular dementia and Alzheimer disease. To test our hypothesis, male control wild-type mice and Alzheimer disease model APP/PS1 (amyloid precursor protein/presenilin 1) mice were exposed to a transverse aortic constriction for 6 weeks, creating a PP overload in the right carotid (ipsilateral). We show that the transverse aortic constriction procedure associated with high PP induces a cascade of vascular damages in the ipsilateral parenchymal microcirculation: in wild-type mice, it impairs endothelial dilatory and blood brain barrier functions and causes microbleeds, a reduction in microvascular density, microvascular cell death by apoptosis, leading to severe hypoperfusion and parenchymal cell senescence. These damages were associated with brain inflammation and a significant reduction in learning and spatial memories. In APP/PS1 mice, that endogenously display severe cerebral vascular dysfunctions, microbleeds, parenchymal inflammation and cognitive dysfunction, transverse aortic constriction-induced high PP further aggravates cerebrovascular damage, Aβ (beta-amyloid) accumulation, and prevents learning. Our study, therefore, demonstrates that brain microvessels are vulnerable to a high PP and mechanical stress associated with transverse aortic constriction, promoting severe vascular dysfunction, disruption of the neurovascular unit, and cognitive decline. Hence, chronic elevated amplitude of the PP could contribute to the development and progression of vascular dementia including Alzheimer disease.

Vascular legacy beyond blood pressure control: benefits of perindopril/indapamide combination in hypertensive patients with diabetes

OBJECTIVES

Much of the chronic care of patients with type 2 diabetes mellitus and hypertension involves the prevention of diabetic complications. Renin-angiotensin system inhibitors are recommended as first-line therapies because of their nephroprotective properties. Their combination with metabolically neutral diuretics is recommended to reduce blood pressure, morbidity and mortality. Our objective was to review the mechanisms by which the combination of the angiotensin-converting enzyme inhibitor, perindopril, and metabolically neutral thiazide-like diuretic, indapamide, targets the pathways involved in microvascular and macrovascular diabetic complications.

METHODS

For this narrative review, extensive literature searches were performed using PubMed/Medline. Articles published in English describing clinical trials and mechanism of action studies that were relevant to the treatment of patients with perindopril and/or indapamide were included.

RESULTS

Perindopril/indapamide treatment has been shown to reduce blood pressure and to have significant beneficial effects on arterial distensibility, kidney structure and function, and endothelial function. Recent data also suggests that perindopril may reduce the deleterious accumulation of advanced glycation end products in diabetic tissue. In the Action in Diabetes and Vascular Disease: Preterax and Diamicron MR Controlled Evaluation diabetes trial, perindopril/indapamide treatment significantly reduced the relative risk of microvascular and macrovascular events by 9%, cardiovascular mortality by 18%, and all-cause mortality by 14%. Interestingly, 6 years after the end of the double-blind period, follow-up data showed that the beneficial effects on mortality continued to be significant even though differences in blood pressure and glycated hemoglobin levels had not been significant for several years. Together this data suggests that treatment with perindopril/indapamide has microvascular and macrovascular effects that extend beyond blood pressure lowering and that this treatment might confer a long-lasting beneficial vascular legacy.

CONCLUSION

Moving forward, understanding the pathophysiological bases of the effects that extend beyond those of blood pressure control will help us differentiate between anti-hypertensive choices.

Whole brain vascular imaging in a mouse model of Alzheimer's disease with two-photon microscopy

Given known correlations between vascular health and cognitive impairment, the development of tools to image microvasculature in the whole brain could help investigate these correlations. We explore the feasibility of using an automated serial two-photon microscope to image fluorescent gelatin-filled whole rodent brains in three-dimensions (3-D) with the goal of carrying group studies. Vascular density (VD) was computed using automatic segmentation combined with coregistration techniques to build a group-level vascular metric in the whole brain. Focusing on the medial prefrontal cortex, cerebral cortex, the olfactory bulb, and the hippocampal formation, we compared the VD of three age groups (2-, 4.5-, and 8-months-old), for both wild type mice and a transgenic model (APP/PS1) with pathology resembling Alzheimer's disease (AD). We report a general loss of VD caused by the aging process with a small VD increase in the diseased animals in the somatomotor and somatosensory cortical regions and the olfactory bulb, partly supported by MRI perfusion data. This study supports previous observations that AD transgenic mice show a higher VD in specific regions compared with WT mice during the early and late stages of the disease (4.5 to 8 months), extending results to whole brain mapping.

Role of ivabradine in management of stable angina in patients with different clinical profiles

In chronic stable angina, elevated heart rate contributes to the development of symptoms and signs of myocardial ischaemia by increasing myocardial oxygen demand and reducing diastolic perfusion time. Accordingly, heart rate reduction is a well-known strategy for improving both symptoms of myocardial ischaemia and quality of life (QOL). The heart rate-reducing agent ivabradine, a direct and selective inhibitor of the I_f current, decreases myocardial oxygen consumption while increasing diastolic time, without affecting myocardial contractility or coronary vasomotor tone. Ivabradine is indicated for treatment of stable angina and chronic heart failure (HF). This review examines available evidence regarding the efficacy and safety of ivabradine in stable angina, when used as monotherapy or in combination with beta-blockers, in particular angina subgroups and in patients with stable angina with left ventricular systolic dysfunction (LVSD) or HF. Trials involving more than 45 000 patients receiving treatment with ivabradine have shown that this agent has antianginal and anti-ischaemic effects, regardless of age, sex, severity of angina, revascularisation status or comorbidities. This heart rate-lowering agent might also improve prognosis, reduce hospitalisation rates and improve QOL in angina patients with chronic HF and LVSD.

Characterization of nerve and microvessel damage and recovery in type 1 diabetic mice after permanent femoral artery ligation

Neuropathy is the most common complication of the peripheral nervous system during the progression of diabetes. The pathophysiology is unclear but may involve microangiopathy, reduced endoneurial blood flow, and tissue ischemia. We used a mouse model of type 1 diabetes to study parallel alterations of nerves and microvessels following tissue ischemia. We designed an easily reproducible model of ischemic neuropathy induced by irreversible ligation of the femoral artery. We studied the evolution of behavioral function, epineurial and endoneurial vessel impairment, and large nerve myelinated fiber as well as small cutaneous unmyelinated fiber impairment for 1 month following the onset of ischemia. We observed a more severe hindlimb dysfunction and delayed recovery in diabetic animals. This was associated with reduced density of large arteries in the hindlimb and reduced sciatic nerve epineurial blood flow. A reduction in sciatic nerve endoneurial capillary density was also observed, associated with a reduction in small unmyelinated epidermal fiber number and large myelinated sciatic nerve fiber dysfunction. Moreover, vascular recovery was delayed, and nerve dysfunction was still present in diabetic animals at day 28. This easily reproducible model provides clear insight into the evolution over time of the impact of ischemia on nerve and microvessel homeostasis in the setting of diabetes. © 2015 Wiley Periodicals, Inc.

Hypertension Accelerates the Progression of Alzheimer-Like Pathology in a Mouse Model of the Disease

Cerebrovascular impairment is frequent in patients with Alzheimer disease and is believed to influence clinical manifestation and severity of the disease. Cardiovascular risk factors, especially hypertension, have been associated with higher risk of developing Alzheimer disease. To investigate the mechanisms underlying the hypertension, Alzheimer disease cross talk, we established a mouse model of dual pathology by infusing hypertensive doses of angiotensin II into transgenic APPPS1 mice overexpressing mutated human amyloid precursor and presenilin 1 proteins. At 4.5 months, at the early stage of disease progression, only hypertensive APPPS1 mice presented impairment of temporal order memory performance in the episodic-like memory task. This cognitive deficit was associated with an increased number of cortical amyloid deposits (223±5 versus 207±5 plaques/mm 2 ; P <0.05) and a 2-fold increase in soluble amyloid levels in the brain and in plasma. Hypertensive APPPS1 mice presented several cerebrovascular alterations, including a 25% reduction in cerebral microvessel density and a 30% to 40% increase in cerebral vascular amyloid deposits, as well as a decrease in vascular endothelial growth factor A expression in the brain, compared with normotensive APPPS1 mice. Moreover, the brain levels of nitric oxide synthase 1 and 3 and the nitrite/nitrate levels were reduced in hypertensive APPPS1 mice (by 49%, 34%, and 33%, respectively, compared with wild-type mice; P <0.05). Our results indicate that hypertension accelerates the development of Alzheimer disease–related structural and functional alterations, partially through cerebral vasculature impairment and reduced nitric oxide production.

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.

[Genic and cellular therapy for peripheral arterial diseases]

Late evolution of peripheral arterial disease consists in the apparition of critical limb ischemia. Surgical treatments allow to treat these patients during long time; however, in most patients, especially the diabetic ones, there a very few options and the clinical evolution is rapidly dramatic. For these reasons, the critical limb ischemia is one of the first diseases treated by genic or cellular therapies aiming to improve blood flow perfusion in the lower-limbs. In this short review, we describe the main clinical trials of genic therapy; most of them have been abandoned because serious side effects, modest effects and major risks. Different types of stem cells are now used for cell therapy: endothelial progenitor cells, early or late, activated or not, mesenchymal stem cells, embryonic stem cells and human induced pluripotent stem cells. Problems of characterization are described and the results of the most important clinical trials are reported.

Ephrin-B2-activated peripheral blood mononuclear cells from diabetic patients restore diabetes-induced impairment of postischemic neovascularization

We hypothesized that in vitro treatment of peripheral blood mononuclear cells (PB-MNCs) from diabetic patients with ephrin-B2/Fc (EFNB2) improves their proangiogenic therapeutic potential in diabetic ischemic experimental models. Diabetes was induced in nude athymic mice by streptozotocin injections. At 9 weeks after hyperglycemia, 10(5) PB-MNCs from diabetic patients, pretreated by EFNB2, were intravenously injected in diabetic mice with hindlimb ischemia. Two weeks later, the postischemic neovascularization was evaluated. The mechanisms involved were investigated by flow cytometry analysis and in vitro cell biological assays. Paw skin blood flow, angiographic score, and capillary density were significantly increased in ischemic leg of diabetic mice receiving EFNB2-activated diabetic PB-MNCs versus those receiving nontreated diabetic PB-MNCs. EFNB2 bound to PB-MNCs and increased the adhesion and transmigration of PB-MNCs. Finally, EFNB2-activated PB-MNCs raised the number of circulating vascular progenitor cells in diabetic nude mice and increased the ability of endogenous bone marrow MNCs to differentiate into cells with endothelial phenotype and enhanced their proangiogenic potential. Therefore, EFNB2 treatment of PB-MNCs abrogates the diabetes-induced stem/progenitor cell dysfunction and opens a new avenue for the clinical development of an innovative and accessible strategy in diabetic patients with critical ischemic diseases.

Towards the therapeutic use of vascular smooth muscle progenitor cells

Recent advances in the development of alternative proangiogenic and revascularization processes, including recombinant protein delivery, gene therapy, and cell therapy, hold the promise of greater efficacy in the management of cardiovascular disease in the coming years. In particular, vascular progenitor cell-based strategies have emerged as an efficient treatment approach to promote vessel formation and repair and to improve tissue perfusion. During the past decade, considerable progress has been achieved in understanding therapeutic properties of endothelial progenitor cells, while the therapeutic potential of vascular smooth muscle progenitor cells (SMPC) has only recently been explored; the number of the circulating SMPC being correlated with cardiovascular health. Several endogenous SMPC populations with varying phenotypes have been identified and characterized in the peripheral blood, bone marrow, and vascular wall. While the phenotypic entity of vascular SMPC is not fully defined and remains an evolving area of research, SMPC are increasingly recognized to play a special role in cardiovascular biology. In this review, we describe the current approaches used to define vascular SMPC. We further summarize the data on phenotype and functional properties of SMPC from various sources in adults. Finally, we discuss the role of SMPC in cardiovascular disease, including the contribution of SMPC to intimal proliferation, angiogenesis, and atherosclerotic plaque instability as well as the benefits resulting from the therapeutic use of SMPC.

Taxane-induced peripheral neuropathy has good long-term prognosis: a 1- to 13-year evaluation

Taxane-induced neuropathy is a frequent complication, in particular in women with breast cancer. The incidence can be variable and ranges from 11 to 87%, depending on the taxane used and identified risk factors, such as cumulative dose, additional neurotoxic chemotherapy agents and previous nerve fragility. However, little is known about long-term outcome and interference with daily life activities. The objective of this study was to assess clinical and electrophysiological neurological evaluation (ENMG) in a cohort of patients, 1-13 years (median 3 years) after the end of the last cure. Sixty-nine women were enrolled in the lymphology unit of Cognacq-Jay's Hospital. They were 58 ± 9 years old (mean age ± SD) and had been treated by docetexel (n = 56), paclitaxel (n = 10) or both (n = 3), 1-13 years before. Sensory neuropathy occurred in 64% and totally disappeared within months for only 14% after cessation of treatment. However, if symptoms were still present at the time of examination, they were considered as minor by almost all patients, with no interference with daily life activities (grade 2 CTCAE v.3.0). ENMG was accepted by 14 patients; it was normal in 7, and showed sensory axonal neuropathy in 5 and sensory-motor neuropathy in 2. The incidence of taxane-induced neuropathy is high, more frequent with paclitaxel than docetaxel, and is characterized by minor or moderate axonal sensory polyneuropathy. When persistent, it is extremely well tolerated by the patient. When clinical motor signs occur, the patient should be referred to a neurologist.

C/EBP homologous protein-10 (CHOP-10) limits postnatal neovascularization through control of endothelial nitric oxide synthase gene expression

BACKGROUND

C/EBP homologous protein-10 (CHOP-10) is a novel developmentally regulated nuclear protein that emerges as a critical transcriptional integrator among pathways regulating differentiation, proliferation, and survival. In the present study, we analyzed the role of CHOP-10 in postnatal neovascularization.

METHODS AND RESULTS

Ischemia was induced by right femoral artery ligation in wild-type and CHOP-10(-/-) mice. In capillary structure of skeletal muscle, CHOP-10 mRNA and protein levels were upregulated by ischemia and diabetes mellitus. Angiographic score, capillary density, and foot perfusion were increased in CHOP-10(-/-) mice compared with wild-type mice. This effect was associated with a reduction in apoptosis and an upregulation of endothelial nitric oxide synthase (eNOS) levels in ischemic legs of CHOP-10(-/-) mice compared with wild-type mice. In agreement with these results, eNOS mRNA and protein levels were significantly upregulated in CHOP-10 short interfering RNA-transfected human endothelial cells, whereas overexpression of CHOP-10 inhibited basal transcriptional activation of the eNOS promoter. Using a chromatin immunoprecipitation assay, we also showed that CHOP-10 was bound to the eNOS promoter. Interestingly, enhanced postischemic neovascularization in CHOP-10(-/-) mice was fully blunted in CHOP-10/eNOS double-knockout animals. Finally, we showed that induction of diabetes mellitus is associated with a marked upregulation of CHOP-10 that substantially inhibited postischemic neovascularization.

CONCLUSIONS

This study identifies CHOP-10 as an important transcription factor modulating vessel formation and maturation.

Neuropilin-1 is upregulated in hepatocellular carcinoma and contributes to tumour growth and vascular remodelling

BACKGROUND & AIMS

Neuropilin-1 (NRP1) is a transmembrane co-receptor for semaphorins and heparin-binding pro-angiogenic cytokines, principally members of the vascular endothelial growth factor family. Recent studies revealed an important role of NRP1 in angiogenesis and malignant progression of many cancers. The role of NRP1 in the development of hepatocellular carcinoma (HCC) is not completely understood.

METHODS

We used human tissue microarrays and a mouse transgenic model of HCC to establish the spatio-temporal patterns of NRP1 expression in HCC. To evaluate the therapeutic potential of targeting NRP1 in HCC, we treated HCC mice with peptide N, an NRP1 binding recombinant protein and competitive inhibitor of the VEGF-A(165)/NRP1 interaction.

RESULTS

We demonstrate that NRP1 is expressed in hepatic endothelial cells of both human healthy biopsies and in HCC samples, but not in normal hepatocytes. We found that increased NRP1 expression in human tumour hepatocytes is significantly associated with primary HCC. Using RT-PCR, Western blot and immunofluorescence analysis we show that NRP1 expression in the liver of transgenic HCC mice is increased with disease progression, in both vascular and tumour compartments. Blocking NRP1 function with peptide N leads to the inhibition of vascular remodelling and tumour liver growth in HCC mice.

CONCLUSIONS

Our results indicate a specific role of NRP1 in HCC growth and vascular remodelling and highlight the possibility of therapeutically targeting NRP1 for the treatment of HCC.

Small interfering RNAs induce target-independent inhibition of tumor growth and vasculature remodeling in a mouse model of hepatocellular carcinoma

RNA interference mediated by small interfering RNAs (siRNAs) has emerged as a potential therapeutic approach to treat various diseases, including cancer. Recent studies with several animal models of posttraumatic revascularization demonstrated that synthetic siRNAs may produce therapeutic effects in a target-independent manner through the stimulation of the toll-like receptor-3 (TLR3)/interferon pathway and suppression of angiogenesis. To analyze the impact of siRNAs on tumor angiogenesis, we injected transgenic mice developing hepatocellular carcinoma (HCC) with either control siRNAs or siRNA targeting neuropilin-1. We found that treatment with these siRNAs led to a comparable reduction in tumor liver volume and to inhibition of tumor vasculature remodeling. We further determined that TLR3, which recognizes double-stranded siRNA, was up-regulated in mouse HCC. Treatment of HCC mice with polyinosinic-polycytidylic acid [poly(I:C)], a TLR3 agonist, led to both a reduction of tumor liver enlargement and a decrease in hepatic arterial blood flow, indicating that TLR3 is functional and may mediate both anti-angiogenic and anti-tumor responses. We also demonstrated that siRNAs increased interferon-γ levels in the liver. In vitro, interferon-γ inhibited proliferation of endothelial cells. In addition, we found that siRNAs inhibited endothelial cell proliferation and morphogenesis in an interferon-γ-independent manner. Our results suggest that synthetic siRNAs inhibit target-independently HCC growth and angiogenesis through the activation of the innate interferon response and by directly inhibiting endothelial cell function.

Inhibition of prolyl hydroxylase domain proteins promotes therapeutic revascularization

BACKGROUND

The hypoxia-inducible transcription factor (HIF) subunits are destabilized via the O(2)-dependent prolyl hydroxylase domain proteins (PHD1, PHD2, and PHD3). We investigated whether inhibition of PHDs via upregulating HIF might promote postischemic neovascularization.

METHODS AND RESULTS

Mice with right femoral artery ligation were treated, by in vivo electrotransfer, with plasmids encoding for an irrelevant short hairpin RNA (shRNA) (shCON [control]) or specific shRNAs directed against HIF-1alpha (shHIF-1alpha), PHD1 (shPHD1), PHD2 (shPHD2), and PHD3 (shPHD3). The silencing of PHDs induced a specific and transient downregulation of their respective mRNA and protein levels at day 2 after ischemia and, as expected, upregulated HIF-1alpha. As a consequence, 2 key hypoxia-inducible proangiogenic actors, vascular endothelial growth factor-A and endothelial nitric oxide synthase, were upregulated at the mRNA and protein levels. In addition, monocyte chemotactic protein-1 mRNA levels and infiltration of Mac-3-positive macrophages were enhanced in ischemic leg of mice treated with shPHD2 and shPHD3. Furthermore, activation of HIF-1alpha-related pathways was associated with changes in postischemic neovascularization. At day 14, silencing of PHD2 and PHD3 increased vessel density by 2.2- and 2.6-fold, capillary density by 1.8- and 2.1-fold, and foot perfusion by 1.2- and 1.4-fold, respectively, compared with shCON (P<0.001). shPHD1 displayed a lower proangiogenic effect. Of interest, coadministration of shHIF-1alpha with shPHD3 abrogated shPHD3-related effects, suggesting that activation of endogenous HIF-1-dependent pathways mediated the proangiogenic effects of PHD silencing.

CONCLUSIONS

We demonstrated that a direct inhibition of PHDs, and more particularly PHD3, promoted therapeutic revascularization. Furthermore, we showed that activation of the HIF-1 signaling pathway is required to promote this revascularization.

Coadministration of endothelial and smooth muscle progenitor cells enhances the efficiency of proangiogenic cell-based therapy

Cell-based therapy is a promising approach designed to enhance neovascularization and function of ischemic tissues. Interaction between endothelial and smooth muscle cells regulates vessels development and remodeling and is required for the formation of a mature and functional vascular network. Therefore, we assessed whether coadministration of endothelial progenitor cells (EPCs) and smooth muscle progenitor cells (SMPCs) can increase the efficiency of cell therapy. Unilateral hindlimb ischemia was surgically induced in athymic nude mice treated with or without intravenous injection of EPCs (0.5 x 10(6)), SMPCs (0.5 x 10(6)) and EPCs+SMPCs (0.25 x 10(6)+0.25 x 10(6)). Vessel density and foot perfusion were increased in mice treated with EPCs+SMPCs compared to animals receiving EPCs alone or SMPCs alone (P<0.001). In addition, capillary and arteriolar densities were enhanced in EPC+SMPC-treated mice compared to SMPC and EPC groups (P<0.01). We next examined the role of Ang-1/Tie2 signaling in the beneficial effect of EPC and SMPC coadministration. Small interfering RNA directed against Ang-1-producing SMPCs or Tie2-expressing EPCs blocked vascular network formation in Matrigel coculture assays, reduced the rate of incorporated EPCs within vascular structure, and abrogated the efficiency of cell therapy. Production of Ang-1 by SMPCs activates Tie2-expressing EPCs, resulting in increase of EPC survival and formation of a stable vascular network. Subsequently, the efficiency of EPC- and SMPC-based cotherapy is markedly increased. Therefore, coadministration of different types of vascular progenitor cells may constitute a novel therapeutic strategy for improving the treatment of ischemic diseases.

Chronic hypoxia-induced angiogenesis normalizes blood pressure in spontaneously hypertensive rats

We hypothesized that activation of angiogenesis by chronic hypoxia may affect vascular resistance and, subsequently, blood pressure levels in spontaneously hypertensive rats (SHRs). Five-week-old prehypertensive SHRs and age-matched normotensive Wistar-Kyoto (WKY) rats (n=8 per group) were maintained under normobaric normoxic or hypoxic (10% O(2)) conditions for 8 weeks. Three weeks later, the systolic blood pressure was lower by 26% in hypoxic SHRs compared to normoxic SHRs (P<0.05) and remained at the normoxic WKY level. Total peripheral vascular resistance, calculated as the mean arterial pressure/cardiac output (assessed by ultrasound imaging and Doppler), was 30% lower in hypoxic than in normoxic SHRs (P<0.001) and returned to WKY levels. Interestingly, chronic hypoxia also significantly reduced systolic blood pressure in adult 12-week-old SHRs with established hypertension; blood pressure was normalized (versus normoxic WKY rats) after 4 weeks of hypoxia. Changes in hemodynamic parameters were associated with activation of proangiogenic pathways. Protein levels of vascular endothelial growth factor (VEGF)-A in the skeletal muscles were increased by 2.2-fold in hypoxic compared to normoxic SHRs (P<0.001). At the end of the hypoxic period, capillary density in the quadriceps muscle was 1.2-fold higher in hypoxic than in normoxic SHRs (P<0.001). Myocardial capillary density and VEGF-A protein contents were also 1.2- and 2.1-fold higher in hypoxic compared to normoxic SHRs (P<0.001 and P<0.05, respectively). Moreover, treatment with neutralizing VEGF-A antibody abrogated the hypoxia-induced angiogenesis and subsequently worsened arterial hypertension. Therefore, our results suggest that chronic normobaric hypoxia (1) activates VEGF-A-induced angiogenesis and thereafter (2) prevents the occurrence of hypertension in young prehypertensive SHRs and (3) normalizes blood pressure in adult SHRs with established hypertension.

Hypertension impairs postnatal vasculogenesis: role of antihypertensive agents

We analyzed the effect of hypertension on postischemic vasculogenesis. Ischemia was induced by right femoral artery ligature in Wistar Kyoto rats (WKY) or spontaneously hypertensive rats (SHR) treated with or without angiotensin-converting enzyme inhibitor (Perindopril, 0.76 mg/kg/d) and angiotensin type 1 receptor blocker (losartan, 30 mg/kg/d). Basal postischemic neovascularization was reduced in SHR compared to WKY (P<0.05, n=8). Treatment with ACE inhibitor or angiotensin type 1 receptor blocker decreased blood pressure levels by 1.4- and 1.3-fold (P<0.001), respectively and restored vessel growth in SHR to WKY levels. Interestingly, 14 days after bone-marrow mononuclear cell (BM-MNC) transfusion, angiographic scores, capillary density, and foot perfusion were decreased by 1.4-, 1.5-, and 1.2-fold, respectively in SHR transfused with BM-MNCs isolated from SHR compared to those receiving BM-MNCs of WKY (P<0.05, n=6). Alteration in BM-MNCs proangiogenic potential was likely related to the reduction in their ability to mobilize into peripheral circulation, as revealed by the 2.9-fold decrease in number of circulating CD34+/CD117+ cells (P<0.001) and to differentiate into cells with endothelial phenotype, as revealed by the 2.1-fold reduction in percentages of DilLDL/BS-1 lectin positive cells (P<0.001). In addition, reactive oxygen species (ROS) levels were increased by 2.2-fold in SHR BM-MNCs compared to WKY BM-MNCs (P<0.01), as assessed by L-012 luminescence. Cotreatment with ACE inhibitor, angiotensin type 1 receptor blocker, or antioxidants (NAC 3 mmol/L, Apocynin 200 micromol/L) reduced ROS levels, improved the number of DilLDL/BS-1 lectin-positive cells by around 1.5-fold, and restored BM-MNCs proangiogenic effects in ischemic hindlimb. In conclusion, alteration in progenitor cell proangiogenic function may participate to the hypertension-induced impairment in postischemic revascularization.

Combination of the angiotensin-converting enzyme inhibitor perindopril and the diuretic indapamide activate postnatal vasculogenesis in spontaneously hypertensive rats

Cardiovascular risk factors are associated with reduction in both the number and function of vascular progenitor cells. We hypothesized that 1) hypertension abrogates postnatal vasculogenesis, and 2) antihypertensive treatment based on the combination of perindopril (angiotensin-converting enzyme inhibitor) and indapamide (diuretic) may counteract hypertension-induced alteration in progenitor cell-related effects. Postischemic neovascularization was significantly lower in untreated spontaneously hypertensive rats (SHRs) compared with Wistar Kyoto (WKY) rats (p < 0.05). Treatment of SHRs with perindopril and the combination of perindopril/indapamide reduced the blood pressure levels and normalized vessel growth in ischemic area. Cotreatment with perindopril and indapamide increased vascular endothelial growth factor and endothelial nitric-oxide synthase protein contents, two key proangiogenic factors. It is interesting to note that 14 days after bone marrow mononuclear cell (BM-MNC) transplantation, revascularization was significantly lower in ischemic SHRs receiving BM-MNCs isolated from SHRs compared with those receiving BM-MNCs isolated from WKY rats (p < 0.05). Alteration in proangiogenic potential of SHR BM-MNCs was probably related to the reduction in their ability to differentiate into endothelial progenitor cells in vitro. Furthermore, the number of circulating endothelial progenitor cells (EPCs) was reduced by 3.1-fold in SHRs compared with WKY rats (p < 0.001). Treatments with perindopril or perindopril/indapamide restored the ability of BM-MNCs to differentiate in vitro into EPCs, increased the number of circulating EPCs, and re-established BM-MNC proangiogenic effects. Therefore, hypertension is associated with a decrease in the number of circulating progenitor cells and in the BM-MNC proangiogenic potential, probably leading to vascular complications in this setting. The combination of perindopril and indapamide counteracts hypertension-induced alterations in progenitor cell-related effects and restores blood vessel growth.

RhoA activation and interaction with Caveolin-1 are critical for pressure-induced myogenic tone in rat mesenteric resistance arteries

OBJECTIVE

Myogenic tone, which has a major role in the regulation of local blood flow, refers to the ability of vascular smooth muscle to adapt its contractility to changes in transmural pressure. Although Rho-kinase is involved in myogenic tone, the pathway involved remains unclear, especially concerning translocation to the plasma membrane and activation of RhoA. As caveolae have a key role in the signal transduction of membrane-bound proteins, we tested the hypothesis that RhoA might be activated by pressure and that its activation might involve caveolin-1, which has been shown to be involved in vascular functions.

METHODS

Myogenic tone was studied in isolated rat mesenteric resistance arteries (118+/-15 microm internal diameter with a pressure of 75 mmHg) submitted to pressure steps (25, 75, and 150 mmHg). Pharmacological blockade of caveolae or RhoA-Rho-kinase pathway was assessed by confocal microscopy in pressurized arteries to analyze protein co-localization and by co-immunoprecipitation in order to confirm protein interactions. Caveolin-1-deficient mice were used to confirm the role of the protein in myogenic tone.

RESULTS

Pressure-induced myogenic tone was significantly reduced by RhoA inactivation with TAT-C3 (90.5% inhibition at 150 mmHg) and by the Rho-kinase inhibitor Y27632 (91.8% inhibition at 150 mmHg). In arteries pressurized at 150 mmHg, RhoA was localized to the plasma membrane (localization by confocal microscopy and increased quantity of RhoA in the membrane fraction after protein extraction). Thus, translocation of RhoA to the plasma membrane was associated with pressure-induced tone. In addition, caveolae disruption with methyl-beta-cyclodextrin reduced myogenic tone by 66% at 150 mmHg. Further, myogenic tone was significantly reduced to 24% of control in caveolin-1-deficient mice (active tone was 32.3+/-2.8 microm and 9.1+/-3.7 microm in +/+ and -/- mice, respectively, n = 5 per group), suggesting a key role of caveolin-1 in myogenic tone. Finally, RhoA and caveolin-1 co-immunoprecipitation and co-localization significantly increased when myogenic tone developed at 150 mmHg (co-localization showed 26+/-13% merging at 25 mmHg versus 97+/-21% at 150 mmHg, n = 5). Co-immunoprecipitation was prevented by TAT-C3 and by methyl beta-cyclodextrin.

CONCLUSION

RhoA activation is critical for the development of myogenic tone in resistance arteries. This activation induced translocation of RhoA to the plasma membrane within caveolae, where the interaction of RhoA with caveolin-1 leads selectively to the activation of a Rho-kinase-dependent force development.

Increase in vascular permeability and vasodilation are critical for proangiogenic effects of stem cell therapy

BACKGROUND

Proangiogenic cell therapy based on administration of bone marrow-derived mononuclear cells (BMCs) or endothelial progenitor cells (EPCs) is now under investigation in humans for the treatment of ischemic diseases. However, mechanisms leading to the beneficial effects of BMCs and EPCs remain unclear.

METHODS AND RESULTS

BMC- and CD34+-derived progenitor cells interacted with ischemic femoral arteries through SDF-1 and CXCR4 signaling and released nitric oxide (NO) via an endothelial nitric oxide synthase (eNOS)-dependent pathway. BMC-induced NO production promoted a marked vasodilation and disrupted vascular endothelial-cadherin/beta-catenin complexes, leading to increased vascular permeability. NO-dependent vasodilation and hyperpermeability were critical for BMC infiltration in ischemic tissues and their proangiogenic potential in a model of hindlimb ischemia in mice.

CONCLUSIONS

Our results propose a new concept that proangiogenic progenitor cell activity does not rely only on their ability to differentiate into endothelial cells but rather on their capacity to modulate the function of preexisting vessels.

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

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

Tetrapeptide AcSDKP Induces Postischemic Neovascularization Through Monocyte Chemoattractant Protein-1 Signaling

BACKGROUND

We investigated the putative proangiogenic activity and molecular pathway(s) of the tetrapeptide acetyl-N-Ser-Asp-Lys-Pro (AcSDKP) in a model of surgically induced hindlimb ischemia.

METHODS AND RESULTS

Hindlimb ischemia was induced by femoral artery ligature and an osmotic minipump was implanted subcutaneously to deliver low (0.12 mg/kg per day) or high (1.2 mg/kg per day) doses of AcSDKP, for 7 or 21 days. Angiography scores, arteriole density, capillary number, and foot perfusion were increased at day 21 in the high-dose AcSDKP-treated mice (by 1.9-, 1.8-, 1.3-, and 1.6-fold, respectively) compared with control animals (P<0.05, P<0.01, P<0.01, respectively). AcSDKP treatment for 24 hours upregulated the monocyte chemoattractant protein-1 (MCP-1) mRNA and protein levels by 1.5-fold in cultured endothelial cells (P<0.01). In the ischemic hindlimb model, administration of AcSDKP also enhanced MCP-1 mRNA levels by 90-fold in ischemic leg (P<0.001) and MCP-1 plasma levels by 3-fold (P<0.001 versus untreated ischemic control mice). MCP-1 levels upregulation were associated with a 2.3-fold increase in the number of Mac3-positive cells in ischemic area of AcSDKP-treated mice (P<0.001 versus untreated animals). Interestingly, AcSDKP-induced monocyte/macrophage infiltration and postischemic neovascularization was fully blunted in MCP-1-deficient animals.

CONCLUSIONS

AcSDKP stimulates postischemic neovascularization through activation of a proinflammatory MCP-1-related pathway.

Comparative effect of aspirin and clopidogrel on arterial function in CHF

BACKGROUND

By inhibiting prostaglandins, aspirin may be deleterious in congestive heart failure (CHF) and/or partially counteract the efficacy of angiotensin-converting enzyme inhibitors (ACEI). Conversely, clopidogrel has no effect on prostaglandin metabolism. The aim of this study was to prospectively investigate the effect of aspirin and clopidogrel on arterial functional properties in CHF patients treated with ACEI.

METHODS

Forty-five patients with stable NYHA class II-IV CHF (64.0+/-15.5 years), ejection fraction <40%, were included in this prospective double-blind study and randomized to receive aspirin 325 mg/day or clopidogrel 75 mg/day for 14 days. Reflected wave assessed by radial applanation tonometry and pulse wave velocity (PWV) were measured at day 0 and day 14.

RESULTS

Aspirin resulted in an increase in the augmentation index of the reflected wave (Delta=+3.5+/-5.2%, p=0.005) and the height above the shoulder of the reflected wave (Delta=+1.7+/-3.1 mm Hg, p=0.023), without statistically variation in PWV. Conversely, clopidogrel had no effect on the same parameters (p=0.512, p=0.677 and 0.801, respectively). Overall, variations in the augmentation index of reflected wave significantly differed when compared aspirin with clopidogrel (p=0.0261).

CONCLUSION

This study demonstrates the existence of a negative effect of aspirin 325 mg/day when compared to clopidogrel 75 mg/day on arterial functional properties in CHF patients treated with ACEI.

Circadian Fluctuations of Macular Edema in Patients with Morning Vision Blurring: Correlation with Arterial Pressure and Effect of Light Deprivation

PURPOSE

This study explored the causes of vision fluctuations in patients with chronic macular edema.

METHODS

Fifteen patients (16 eyes) with vision blurring at awakening due to post-central retinal vein occlusion (CRVO) macular edema underwent three examination sessions over 24 hours (at 7 PM, immediately after awakening at 7 AM, and at 7 PM), which comprised assessment of Early Treatment Diabetic Retinopathy Study score and measurement of macular thickness (MT) by optical coherence tomography. Ocular perfusion pressure was calculated from ambulatory arterial pressure measurement. In addition, after the 7 AM measurements, the patients were randomly selected for monocular light deprivation during the day to evaluate the role of retinal illumination in these fluctuations.

RESULTS

Circadian fluctuation of MT was documented in all patients. At 7 AM, mean visual acuity (VA) was worse (mean +/- SD of the difference: 6.5 +/- 7.2 points; P < 0.002) and mean MT was higher (57.4 +/- 34 microm; P < 0.001) than at 7 PM. Fluctuations of MT were correlated to fluctuation of arterial pressure (P = 0.05), but were not influenced by monocular light deprivation.

CONCLUSIONS

In most patients complaining of visual fluctuations due to macular edema secondary to CRVO, MT and VA were found to undergo a circadian cycle. These short-term anatomic and functional variations were associated with arterial pressure variations (that is, macular thickening was inversely correlated to the arterial pressure drop during the night), but were not due to light deprivation.

Systolodiastolic variations of blood flow during central retinal vein occlusion: exploration by dynamic angiography

BACKGROUND/AIM

In patients with acute central retinal vein occlusion (CRVO), dynamic angiography may reveal the presence of pulsatile flow (termed here pulsatile venular outflow, PVO) within first order veins (that is, the large veins). The main goal of this study was to investigate the mechanism underlying PVO.

METHODS

10 patients with CRVO and PVO were included. Quantitative and qualitative analysis of venous flow on dynamic angiograms allowed the correlation, temporally, of second and first order vein flow on the one hand, and venous flow and systolic cycle on the other.

RESULTS

Analysis of the time-velocity curve showed that (1) the onset of arterial systole preceded the onset of PVO by less than 0.08 seconds (n = 5); (2) PVO onset was simultaneous to the time of onset of minimal flow (Vmin) in first order veins (n = 10); (3) the time of onset of maximal flow (Vmax) in first order veins occurred 0.20-0.44 seconds after the onset of PVO (n = 6).

CONCLUSIONS

During CRVO with severe reduction in blood flow, the presence of PVO is the result of the existence of a distinct haemodynamic regimen in first and second order veins. These data support the hypothesis that second order veins flow is synchronous with the arterial flow, while the delayed peak flow in first order veins may reflect the consequences of the delayed IOP curve and/or of intermittent venous compression.

Involvement of RhoA/Rho kinase pathway in myogenic tone in the rabbit facial vein

Myogenic tone (MT), a fundamental stretch-sensitive vasoconstrictor property of resistance arteries and veins, is a key determinant of local blood flow regulation. We evaluated the pathways involved in MT development. The role of the RhoA/Rho kinase, p38 MAP kinase, and HSP27 in MT was investigated in the rabbit facial vein (RFV), previously shown to possess MT at a pressure level equivalent to 20 mm Hg. Venous MT is poorly understood, although venous diseases affect a large proportion of the population. Stretched RFV are characterized by a temperature-sensitive MT, which is normal at 39 degrees C but fails to develop at 33 degrees C. This allows for the discrimination of the pathways involved in MT from the multiple pathways activated by stretch. Isolated RFV segments were mounted in organ baths and stretched. Temperature was then set at 33 degrees C or 39 degrees C. MT was associated to the translocation of RhoA to the plasma membrane and the Rho kinase inhibitor Y27632 decreased stretch-induced MT by 93.1+/-4.9%. MT was also associated to an increase in p38 (131.0+/-12.5% at 39 degrees C versus 100% at 33 degrees C) and HSP27 phosphorylation (196.1+/-13.3% versus 100%), and the p38 MAP kinase inhibitor SB203580 decreased MT by 36.5+/-8.1%. (39 degrees C, compared with RFV stretched at 33 degrees C). Finally, phosphorylation of p38 was blocked by Y27632 and HSP27 phosphorylation was inhibited by SB203580 and Y27632. Thus, MT and the associated p38 and HSP27 phosphorylation seem to depend on RhoA/Rho kinase activation in stretch RFV.

[The importance of microcirculation and tissue perfusion in hypertension]

The importance of abnormalities observed in the microcirculation of hypertensive subjects is being increasingly recognised. These microvascular changes may be central to the development of end-organ damage brought about by hypertension, including ischaemic heart disease. The primary function of the microcirculation is to supply oxygen and nutrients to myocardial tissue, and it also has an important role in regulating coronary blood flow. Some 70-90% of the overall peripheral resistance of the circulatory system arises at the level of the microcirculation. In hypertension, thickening of the microvascular walls occur, with narrowing of the lumen, so that eventually the vessel is functionally occluded. The result is a reduction in the number of arterioles or capillaries in a given vascular bed. Such changes have been seen in the structure and density of the microvasculature of heart muscle, the conjunctiva and retina, and in the kidneys. In hypertension a vicious circle occurs, with an increase in blood pressure producing a rise in resistance in the microcirculation, leading to further elevation of blood pressure. New techniques for exploring the coronary microcirculation have shown that microvascular damage results in reductions of coronary vasodilator reserve, an important predictor of clinical deterioration and death. With studies showing that impairment of microcirculation occurs early in patients with hypertension, there would seem to be a need for new therapeutic perspectives in hypertension, concentrating on preventing or reversing changes to the microvasculature of affected organs.

Flow-Dependent Dilation Mediated by Endogenous Kinins Requires Angiotensin AT2Receptors

The vascular kallikrein-kinin system contributes to about one third of flow-dependent dilation in mice carotid arteries, by activating bradykinin B2 receptors coupled to endothelial nitric oxide (NO) release. Because the bradykinin/NO pathway may mediate some of the effects of angiotensin II AT2 receptors, we examined the possible contribution of AT2 receptors to the kinin-dependent response to flow. Changes in outer diameter after increases in flow rate were evaluated in perfused arteries from wild-type animals (TK+/+) and in tissue kallikrein-deficient mice (TK-/-) in which the presence of AT2 receptor expression was verified. Saralasin, a nonselective angiotensin II receptor antagonist, impaired significantly flow-induced dilation in TK+/+, whereas it had no effect in TK-/- mice. In both groups, blockade of AT1 receptors with losartan or candesartan did not affect the response to flow. Inhibition of AT2 receptors with PD123319 reduced significantly flow-induced dilation in TK+/+ mice, but had no significant effect in TK-/- mice. Combining PD123319 with the bradykinin B2 receptor antagonist HOE-140 had no additional effect to AT2 receptor blockade alone in TK+/+ arteries. Flow-dependent-dilation was also impaired in AT2 receptor deficient mice (AT2-/-) when compared with wild-type littermates. Furthermore, HOE-140 significantly reduced the response to flow in the AT2+/+, but not in AT2-/- mice. In conclusion, this study demonstrates that the presence of functional AT2 receptors is necessary to observe the contribution of the vascular kinin-kallikrein system to flow-dependent dilation.

Impairment in ischemia-induced neovascularization in diabetes: bone marrow mononuclear cell dysfunction and therapeutic potential of placenta growth factor treatment

Mechanisms that hinder ischemia-induced neovascularization in diabetes remain poorly understood. We hypothesized that endogenous bone marrow mononuclear cell (BM-MNC) dysfunction may contribute to the abrogated postischemic revascularization reaction associated with diabetes. We first analyzed the effect of diabetes (streptozotocin, 40 mg/kg) on BM-MNC pro-angiogenic potential in a model of surgically induced hindlimb ischemia. In nondiabetic animals, transplantation of BM-MNCs isolated from nondiabetic animals raised the ischemic/nonischemic angiographic score, capillary number, and blood flow recovery by 1.8-, 2.7-, and 2.2-fold, respectively, over that of PBS-injected nondiabetic animals (P < 0.05). Administration of diabetic BM-MNCs also improved the neovascularization reaction in ischemic hindlimbs of nondiabetic mice but to a lesser extent from that observed with nondiabetic BM-MNC transplantation. In diabetic mice, injection of nondiabetic BM-MNCs was still more efficient than that of diabetic BM-MNCs. Such BM-MNC dysfunction was associated with the impairment of diabetic BM-MNC capacity to differentiate into endothelial progenitor cells (EPCs) in vitro and to participate in vascular-like structure formation in a subcutaneous Matrigel plug. Placenta growth factor (PlGF) administration improved by sixfold the number of EPCs differentiated from diabetic BM-MNCs in vitro and enhanced ischemic/nonischemic angiographic score, capillary number and blood flow recovery by 1.9-, 1.5- and 1.6-fold, respectively, over that of untreated diabetic animals (P < 0.01). Endogenous BM-MNC pro-angiogenic potential was affected in diabetes. Therapeutic strategy based on PlGF administration restored such defects and improved postischemic neovascularization in diabetic mice.

Minimally Invasive, In Vivo Exploration of Mouse Small Artery Reactivity

The aim of the study was to investigate in vivo arterial reactivity in the mouse hind limb using Orthogonal Polarisation Spectral (OPS) imaging, which delivers high-contrast images of vascular beds by visualizing red blood cells. After minimal skin invasion of anesthetized mice, the OPS probe was placed on the hind limb continuously superfused with physiological saline solution. Then, the response of the saphenous artery (average luminal diameter 127 +/- 3 microm; n = 15) to topical application of increasing concentrations of acetylcholine or phenylephrine was examined. Mean carotid arterial blood pressure was unaffected during the experiment. The basal diameter decreased by 70% during exposure to phenylephrine (pD2: 5.65 +/- 0.08; n = 9), while acetylcholine augmented basal diameter up to 199% (pD2: 6.55 +/- 0.12; n = 6). Application of sodium nitroprusside did not further increase arterial diameter following acetylcholine exposure. After washing out, arterial luminal diameters returned to initial values. Second exposure to vasoactive agents demonstrated that changes in diameter were reproducible with time and not different between left and right saphenous arteries. Thus, OPS imaging is an in vivo dye-free, simple and minimally invasive approach, which provides unique information regarding the behavior of vascular network within conditions of cellular and physiological homeostasis.