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Rationale: Paracrine secretions seem to mediate therapeutic effects of human CD34 + stem cells locally transplanted in patients with myocardial and critical limb ischemia and in animal models. Earlier, we had discovered that paracrine secretion from human CD34 + cells contains proangiogenic, membrane-bound nanovesicles called exosomes (CD34Exo). Objective: Here, we investigated the mechanisms of CD34Exo-mediated ischemic tissue repair and therapeutic angiogenesis by studying their miRNA content and uptake. Methods and Results: When injected into mouse ischemic hindlimb tissue, CD34Exo, but not the CD34Exo-depleted conditioned media, mimicked the beneficial activity of their parent cells by improving ischemic limb perfusion, capillary density, motor function, and their amputation. CD34Exo were found to be enriched with proangiogenic miRNAs such as miR-126-3p. Knocking down miR-126-3p from CD34Exo abolished their angiogenic activity and beneficial function both in vitro and in vivo. Interestingly, injection of CD34Exo increased miR-126-3p levels in mouse ischemic limb but did not affect the endogenous synthesis of miR-126-3p, suggesting a direct transfer of stable and functional exosomal miR-126-3p. miR-126-3p enhanced angiogenesis by suppressing the expression of its known target, SPRED1 , simultaneously modulating the expression of genes involved in angiogenic pathways such as VEGF (vascular endothelial growth factor), ANG1 (angiopoietin 1), ANG2 (angiopoietin 2), MMP9 (matrix metallopeptidase 9), TSP1 (thrombospondin 1), etc. Interestingly, CD34Exo, when treated to ischemic hindlimbs, were most efficiently internalized by endothelial cells relative to smooth muscle cells and fibroblasts, demonstrating a direct role of stem cell–derived exosomes on mouse endothelium at the cellular level. Conclusions: Collectively, our results have demonstrated a novel mechanism by which cell-free CD34Exo mediates ischemic tissue repair via beneficial angiogenesis. Exosome-shuttled proangiogenic miRNAs may signify amplification of stem cell function and may explain the angiogenic and therapeutic benefits associated with CD34 + stem cell therapy.

The translation of cell-based therapies for ischemic tissue repair remains limited by several factors, including poor cell survival and limited target site retention. Advances in nanotechnology enable the development of specifically designed delivery matrices to address these limitations and thereby improve the efficacy of cell-based therapies. Given the relevance of integrin signaling for cellular homeostasis, we developed an injectable, bioactive peptide-based nanofiber matrix that presents an integrin-binding epitope derived from fibronectin, and evaluated its feasibility as a supportive artificial matrix for bone marrow-derived pro-angiogenic cells (BMPACs) used as a therapy in ischemic tissue repair. Incubation of BMPACs with these peptide nanofibers in vitro significantly attenuated apoptosis while enhancing proliferation and adhesion. Pro-angiogenic function was enhanced, as cells readily formed tubes. These effects were, in part, mediated via p38, and p44/p42 MAP kinases, which are downstream pathways of focal adhesion kinase. In a murine model of hind limb ischemia, an intramuscular injection of BMPACs within this bioactive peptide nanofiber matrix resulted in greater retention of cells, enhanced capillary density, increased limb perfusion, reduced necrosis/amputation, and preserved function of the ischemic limb compared to treatment with cells alone. This self-assembling, bioactive peptide nanofiber matrix presenting an integrin-binding domain of fibronectin improves regenerative efficacy of cell-based strategies in ischemic tissue by enhancing cell survival, retention, and reparative functions.

The role of inflammation on atherosclerosis and restenosis is well established. Restenosis is thought to be a complex response to injury, which includes early thrombus formation, acute inflammation and neo-intimal growth. Inflammatory cells are likely contributors in the host response to vascular injury, via cytokines and chemokines secretion, including TNF-alpha (TNF). We have previously shown that IL-10 inhibits TNF and other inflammatory mediators produced in response to cardiovascular injuries. The specific effect of IL-10 on endothelial cell (ECs) biology is not well elucidated. Here we report that in a mouse model of carotid denudation, IL-10 knock-out mice (IL-10KO) displayed significantly delayed Re-endothelialization and enhanced neo-intimal growth compared to their WT counterparts. Exogenous recombinant IL-10 treatment dramatically blunted the neo-intimal thickening while significantly accelerating the recovery of the injured endothelium in WT mice. In vitro, IL-10 inhibited negative effects of TNF on ECs proliferation, ECs cell cycle, ECs-monocyte adhesion and ECs apoptosis. Furthermore, IL-10 treatment attenuated TNF-induced smooth muscle cells proliferation. Our data suggest that IL-10 differentially regulate endothelial and vascular smooth cells proliferation and function and thus inhibits neo-intimal hyperplasia. Thus, these results may provide insights necessary to develop new therapeutic strategies to limit vascular restenosis during percutaneous coronary intervention (PCI) in the clinics.

Neural stem cells (NSCs) differentiate into endothelial cells (ECs) and neuronal cells. Estradiol (E2) is known to exhibit proangiogenic effects on ischemic tissues via EC activation. Therefore, we hypothesized that E2 can promote the therapeutic potential of NSC transplantation for injured nerve repair via the differentiation of NSCs into ECs during neovascularization. NSCs isolated from newborn mouse brains were transplanted into injured sciatic nerves with (NSC/E2 group) or without E2-conjugated gelatin hydrogel (E2 group). The NSC/E2 group exhibited the greatest recovery in motor nerve conduction velocity, voltage amplitude, and exercise tolerance. Histological analyses revealed increased intraneural vascularity and blood perfusion as well as striking NSC recruitment to the neovasculature in the injured nerves in the NSC/E2 group. In vitro, E2 enhanced the NSC migration and proliferation inhibiting apoptosis. Fluorescence-activated cell sorting analysis also revealed that E2 significantly increased the percentage of CD31 in NSCs, and the effect of E2 was completely neutralized by the estrogen receptor antagonist ICI. The combination of E2 administration and NSC transplantation cooperatively improved the functional recovery of injured peripheral nerves, at least in part, via E2-associated NSC differentiation into ECs. These findings provide a novel mechanistic insight into both NSC biology and the biological effects of endogenous E2.

Rationale: Ischemic cardiovascular disease represents one of the largest epidemics currently facing the aging population. Current literature has illustrated the efficacy of autologous, stem cell therapies as novel strategies for treating these disorders. The CD34+ hematopoetic stem cell has shown significant promise in addressing myocardial ischemia by promoting angiogenesis that helps preserve the functionality of ischemic myocardium. Unfortunately, both viability and angiogenic quality of autologous CD34+ cells decline with advanced age and diminished cardiovascular health. Objective: To offset age- and health-related angiogenic declines in CD34+ cells, we explored whether the therapeutic efficacy of human CD34+ cells could be enhanced by augmenting their secretion of the known angiogenic factor, sonic hedgehog (Shh). Methods and Results: When injected into the border zone of mice after acute myocardial infarction, Shh-modified CD34+ cells (CD34 Shh ) protected against ventricular dilation and cardiac functional declines associated with acute myocardial infarction. Treatment with CD34 Shh also reduced infarct size and increased border zone capillary density compared with unmodified CD34 cells or cells transfected with the empty vector. CD34 Shh primarily store and secrete Shh protein in exosomes and this storage process appears to be cell-type specific. In vitro analysis of exosomes derived from CD34 Shh revealed that (1) exosomes transfer Shh protein to other cell types, and (2) exosomal transfer of functional Shh elicits induction of the canonical Shh signaling pathway in recipient cells. Conclusions: Exosome-mediated delivery of Shh to ischemic myocardium represents a major mechanism explaining the observed preservation of cardiac function in mice treated with CD34 Shh cells.

The antagonism of CXC-chemokine receptor 4 (CXCR4) with AMD3100 improves cardiac performance after myocardial infarction by augmenting the recruitment of endothelial progenitor cells (EPCs) from the bone marrow to the regenerating vasculature. We investigated whether AMD3100 may accelerate diabetes-impaired wound healing through a similar mechanism. Skin wounds were made on the backs of leptin receptor-deficient mice and treated with AMD3100 or saline. Fourteen days after treatment, wound closure was significantly more complete in AMD3100-treated mice (AMD3100: 87.0 ± 2.6%, saline: 33.1 ± 1.8%; P

Both estradiol (E2) and Sonic Hedgehog (Shh) contribute to angiogenesis and nerve regeneration. Here, we investigated whether E2 improves the recovery of injured nerves by downregulating the Shh inhibitor hedgehog-interacting protein (HIP) and increasing Shh-induced angiogenesis. Mice were treated with local injections of E2 or placebo one week before nerve-crush injury; 28 days after injury, nerve conduction velocity, exercise duration, and vascularity were significantly greater in E2-treated mice than in placebo-treated mice. E2 treatment was also associated with higher mRNA levels of Shh, the Shh receptor Patched-1, and the Shh transcriptional target Gli1, but with lower levels of HIP. The E2-induced enhancement of nerve vascularity was abolished by the Shh inhibitor cyclopamine, and the effect of E2 treatment on Shh, Gli1, and HIP mRNA expression was abolished by the E2 inhibitor ICI. Gli-luciferase activity in human umbilical-vein endothelial cells (HUVECs) increased more after treatment with E2 and Shh than after treatment with E2 alone, and E2 treatment reduced HIP expression in HUVECs and Schwann cells without altering Shh expression. Collectively, these findings suggest that E2 improves nerve recovery, at least in part, by reducing HIP expression, which subsequently leads to an increase in Shh signaling and Shh-induced angiogenesis.

ObjectivesThis study was designed to compare the effectiveness of Sonic hedgehog (Shh) gene transfer, AMD3100induced progenitor-cell mobilization, and Shh-AMD3100 combination therapy for treatment of surgically induced myocardial infarction (MI) in mice. BackgroundShh gene transfer improves myocardial recovery by up-regulating angiogenic genes and enhancing the incorporation of bone marrow‐derived progenitor cells (BMPCs) in infarcted myocardium. Here, we investigated whether the effectiveness of Shh gene therapy could be improved with AMD3100-induced progenitor-cell mobilization. MethodsGene expression and cell function were evaluated in cells cultured with medium collected from fibroblasts transfected with plasmids encoding human Shh (phShh). MI was induced in wild-type mice, in matrix metalloproteinase (MMP)-9 knockout mice, and in mice transplanted with bone marrow that expressed green-fluorescent protein. Mice were treated with 100!g of phShh (administered intramyocardially), 5 mg/kg of AMD3100 (administered subcutaneously), or both; cardiac function was evaluated echocardiographically, and fibrosis, capillary density, and BMPC incorporation were evaluated immunohistochemically. Results phShh increased vascular endothelial growth factor and stromal cell‐derived factor 1 expression in fibroblasts; the medium from phShh-transfected fibroblasts increased endothelial-cell migration and the migration, proliferation, and tube formation of BMPCs. Combination therapy enhanced cardiac functional recovery (i.e., left ventricular ejection fraction) in wild-type mice, but not in MMP-9 knockout mice, and was associated with less fibrosis, greater capillary density and smooth muscle‐containing vessel density, and enhanced BMPC incorporation. ConclusionsCombination therapy consisting of intramyocardial Shh gene transfer and AMD3100-induced progenitor-cell mobilization improves cardiac functional recovery after MI and is superior to either individual treatment for promoting therapeutic neovascularization. (J Am Coll Cardiol 2011;57:2444‐52) © 2011 by the American College of Cardiology Foundation Recent investigations suggest that the effectiveness of angiogenic gene therapy may be increased by combining it with treatments that mobilize progenitor cells from the bone marrow. Kawamoto et al. (1) combined gene transfer of vascular endothelial growth factor (VEGF) with progenitor-cell mobilization in animal models of acute and chronic myocardial infarction, revealing that the combination therapy was more effective than either treatment alone. However, these promising results were not reproduced in a phase I clinical study that combined intramyocardial injection of VEGF-A plasmid and progenitor-cell mobilization in patients with severe chronic ischemic heart disease (2); both of these investigations mobilized stem cells via the administration of granulocyte colony-stimulating factor, which has been associated with an increased risk of restenosis in 1 report (3). Previously we demonstrated that myocardial infarction (MI) reactivates the Hedgehog signaling pathway in adult mammals and that Sonic hedgehog (Shh) up-regulates the

Rationale: The mobilization of bone marrow (BM) progenitor cells (PCs) is largely governed by interactions between stromal cell–derived factor (SDF)-1 and CXC chemokine receptor (CXCR)4. Ischemic injury disrupts the SDF-1–CXCR4 interaction and releases BM PCs into the peripheral circulation, where the mobilized cells are recruited to the injured tissue and contribute to vessel growth. BM PCs can also be mobilized by the pharmacological CXCR4 antagonist AMD3100, but the other components of the SDF-1–CXCR4 signaling pathway are largely unknown. c-kit, a membrane-bound tyrosine kinase and the receptor for stem cell factor, has also been shown to play a critical role in BM PC mobilization and ischemic tissue repair. Objective: To investigate the functional interaction between SDF-1–CXCR4 signaling and c-kit activity in BM PC mobilization. Methods and Results: AMD3100 administration failed to mobilize BM PCs in mice defective in c-kit kinase activity or in mice transplanted with BM cells that expressed a constitutively active c-kit mutant. Furthermore, BM levels of phosphorylated (phospho)–c-kit declined after AMD3100 administration and after CXCR4 deletion. In cells adhering to culture plates coated with vascular cell adhesion molecule 1, SDF-1 and stem cell factor increased phospho–c-kit levels, and AMD3100 treatment suppressed SDF-1–induced, but not SCF-induced, c-kit phosphorylation. SDF-1–induced c-kit phosphorylation also required the activation of Src nonreceptor tyrosine kinase: pretreatment of cells with a selective Src inhibitor blocked both c-kit phosphorylation and the interaction between c-kit and phospho-Src. Conclusions: These findings indicate that the regulation of BM PC trafficking by SDF-1 and CXCR4 is dependent on Src-mediated c-kit phosphorylation.

The morphogen Sonic hedgehog (Shh) promotes neovascularization in adults by inducing pro-angiogenic cytokine expression in fibroblasts; however, the direct effects of Shh on endothelial cell (EC) function during angiogenesis are unknown. Our findings indicate that Shh promotes capillary morphogenesis (tube length on Matrigel™ increased to 271 ± 50% of the length in untreated cells, p = 0.00003), induces EC migration (modified Boyden chamber assay, 191 ± 35% of migration in untreated cells, p = 0.00009), and increases EC expression of matrix metalloproteinase 9 (MMP-9) and osteopontin (OPN) mRNA (real-time RT-PCR), which are essential for Shh-induced angiogenesis both in vitro and in vivo . Shh activity in ECs is mediated by Rho, rather than through the “classic” Shh signaling pathway, which involves the Gli transcription factors. The Rho dependence of Shh-induced EC angiogenic activity was documented both in vitro , with dominant-negative RhoA and Rho kinase (ROCK) constructs, and in vivo , with the ROCK inhibitor Y27632 in the mouse corneal angiogenesis model. Finally, experiments performed in MMP-9- and OPN-knockout mice confirmed the roles of the ROCK downstream targets MMP-9 and OPN in Shh-induced angiogenesis. Collectively, our results identify a “nonclassical” pathway by which Shh directly modulates EC phenotype and angiogenic activity.

Background— Aging is a risk factor for coronary and peripheral artery disease. Tumor necrosis factor-α (TNF-α), a proinflammatory cytokine, is expressed in ischemic tissue and is known to modulate angiogenesis. Little is known about the role of TNF-α receptors (TNFR1/p55 and TNFR2/p75) in angiogenic signaling. Methods and Results— We studied neovascularization in the hindlimb ischemia model in young and old TNFR2/p75 knockout (p75KO) and wild-type age-matched controls. Between days 7 to 10 after hindlimb surgery, 100% of old p75KOs experienced autoamputation of the operated limbs, whereas none of the age-matched wild-type mice exhibited hindlimb necrosis. Poor blood flow recovery in p75KO mice was associated with increased endothelial cell apoptosis, decreased capillary density, and significant reductions in the expression of vascular endothelial growth factor and basic fibroblast growth factor-2 mRNA transcripts in ischemic tissue and in circulating endothelial progenitor cells. The number of circulating bone marrow–derived endothelial progenitor cells was significantly reduced in p75KO mice. Transplantation of wild-type bone marrow mononuclear cells into irradiated old p75KO mice 1 month before hindlimb surgery prevented limb loss. Conclusions— Our present study suggests that ischemia-induced endothelial progenitor cell–mediated neovascularization is dependent, at least in part, on p75 TNF receptor expressed in bone marrow–derived cells. Specifically, endothelial cell/endothelial progenitor cell survival, vascular endothelial growth factor expression, endothelial progenitor cell mobilization from bone marrow, endothelial progenitor cell differentiation, and ultimately ischemia-induced collateral vessel development are dependent on signaling through TNFR2/p75. Furthermore, because TNFR2/p75 becomes an age-related limiting factor in postischemic recovery, it may be a potential gene target for therapeutic interventions in adult vascular diseases.

Axonal guidance and vascular patterning share several guidance cues, including proteins in the netrin family. We demonstrate that netrins stimulate proliferation, migration, and tube formation of human endothelial cells in vitro and that this stimulation is independent of known netrin receptors. Suppression of netrin1a messenger RNA in zebrafish inhibits vascular sprouting, implying a proangiogenic role for netrins during vertebrate development. We also show that netrins accelerate neovascularization in an in vivo model of ischemia and that they reverse neuropathy and vasculopathy in a diabetic murine model. We propose that the attractive vascular and neural guidance functions of netrins offer a unique therapeutic potential.

Background— Recent data have indicated that estradiol can modulate the kinetics of endothelial progenitor cells (EPCs) via endothelial nitric oxide synthase (eNOS)–dependent mechanisms. We hypothesized that estradiol could augment the incorporation of bone marrow (BM)–derived EPCs into sites of ischemia-induced neovascularization, resulting in protection from ischemic injury. Methods and Results— Myocardial infarction (MI) was induced by ligation of the left coronary artery in ovariectomized mice receiving either 17β-estradiol or placebo. Estradiol induced significant increases in circulating EPCs 2 and 3 weeks after MI in estradiol-treated animals, and capillary density was significantly greater in estradiol-treated animals. Greater numbers of BM-derived EPCs were observed at ischemic sites in estradiol-treated animals than in placebo-treated animals 1 and 4 weeks after MI. In eNOS-null mice, the effect of estradiol on mobilization of EPCs was lost, as was the functional improvement in recovery from acute myocardial ischemia. A decrease was found in matrix metalloproteinase-9 (MMP-9) expression in eNOS-null mice under basal and estradiol-stimulated conditions after MI, the mobilization of EPCs by estradiol was lost in MMP-9–null mice, and the functional benefit conferred by estradiol treatment after MI in wild-type mice was significantly attenuated. Conclusions— Estradiol preserves the integrity of ischemic tissue by augmenting the mobilization and incorporation of BM-derived EPCs into sites of neovascularization by eNOS-mediated augmentation of MMP-9 expression in the BM. Moreover, these data have broader implications with regard to our understanding of the role of EPCs in post-MI recovery and on the sex discrepancy in cardiac events.

Delayed reendothelialization contributes to restenosis after angioplasty and stenting in diabetes. Prior data have shown that bone marrow (BM)-derived endothelial progenitor cells (EPCs) contribute to endothelial recovery after arterial injury. We investigated the hypothesis that the EPC contribution to reendothelialization may be impaired in diabetes, resulting in delayed reendothelialization. Reendothelialization was significantly reduced in diabetic mice compared with nondiabetic mice in a wire-induced carotid denudation model. The EPC contribution to neoendothelium was significantly reduced in Tie2/LacZ BM-transplanted diabetic versus nondiabetic mice. BM from diabetic and nondiabetic mice was transplanted into nondiabetic mice, revealing that reendothelialization was impaired in the recipients of diabetic BM. To examine the relative roles of denuded artery versus EPCs in diabetes, we injected diabetic and nondiabetic EPCs intravenously after arterial injury in diabetic and nondiabetic mice. Diabetic EPCs recruitment to the neoendothelium was significantly reduced, regardless of the diabetic status of the recipient mice. In vitro, diabetic EPCs exhibited decreased migration and adhesion activities. Vascular endothelial growth factor and endothelial NO synthase expressions were also significantly reduced in diabetic EPCs. Notably, thrombospondin-1 mRNA expression was significantly upregulated in diabetic EPCs, associating with the decreased EPC adhesion activity in vitro and in vivo. Reendothelialization is impaired by malfunctioning EPCs in diabetes. Diabetic EPCs have phenotypic differences involving thrombospondin-1 expression compared with nondiabetic EPCs, revealing potential novel mechanistic insights and therapeutic targets to improve reendothelialization and reduce restenosis in diabetes.

Previous studies have shown that local angiogenic gene therapy acts, in part, by recruiting endothelial progenitor cells (EPCs) to ischemic tissue. Recent data indicate that patients with the most severe vascular disease may have insufficient or deficient EPCs and the poorest response to angiogenic therapy. Accordingly, we hypothesized that combining human CD34(+) cell implantation with local vascular endothelial growth factor 2 (phVEGF2) gene therapy might overcome these deficiencies. The addition of VEGF2 to EPC cultures resulted in significant and dose-dependent decreases in EPC apoptosis. Phosphorylated Akt (p-Akt) was increased in VEGF2-treated EPCs. In vivo, myocardial infarction (MI) was induced by ligation of the left anterior descending coronary artery in 34 immunodeficient rats. The animals were then randomized to one of four treatment groups: cell therapy alone with human CD34(+) cells; VEGF2 gene therapy alone; combination therapy with CD34(+) cells plus phVEGF2; or CD34(-) cells and 50 microg empty plasmid. Four weeks after MI, animals treated with combination therapy showed improved fractional shortening, increased capillary density, and reduced infarct size compared with the other three groups. Combination therapy was also associated with an increased number of circulating EPCs 1 week after MI. Combined subtherapeutic doses of cell and gene therapy result in a significant therapeutic effect compared to monotherapy. This approach may overcome therapeutic failures (e.g. inability of certain patients to mobilize sufficient EPCs) and may also offer safety advantages by allowing lower dosing strategies.

The cell surface receptor alpha4 integrin plays a critical role in the homing, engraftment, and maintenance of hematopoietic progenitor cells (HPCs) in the bone marrow (BM). Down-regulation or functional blockade of alpha4 integrin or its ligand vascular cell adhesion molecule-1 mobilizes long-term HPCs. We investigated the role of alpha4 integrin in the mobilization and homing of BM endothelial progenitor cells (EPCs). EPCs with endothelial colony-forming activity in the BM are exclusively alpha4 integrin-expressing cells. In vivo, a single dose of anti-alpha4 integrin antibody resulted in increased circulating EPC counts for 3 d. In hindlimb ischemia and myocardial infarction, systemically administered anti-alpha4 integrin antibody increased recruitment and incorporation of BM EPCs in newly formed vasculature and improved functional blood flow recovery and tissue preservation. Interestingly, BM EPCs that had been preblocked with anti-alpha4 integrin ex vivo or collected from alpha4 integrin-deficient mice incorporated as well as control cells into the neovasculature in ischemic sites, suggesting that alpha4 integrin may be dispensable or play a redundant role in EPC homing to ischemic tissue. These data indicate that functional disruption of alpha4 integrin may represent a potential angiogenic therapy for ischemic disease by increasing the available circulating supply of EPCs.

Haplosporidium sp. is described from rock oysters Saccostrea cuccullata Born, 1778 experiencing epizootics on the northwestern coast of Western Australia. All stages were observed as focal infections in the connective tissue of the gills, or as disseminated infections in the mantle and around digestive diverticulae. Haplosporidium sp. occurred between epithelial cells of the gut, in focal lesions in the gills, but not in the epithelium of the digestive diverticulae, and sporulation was confined to the connective tissue. Plasmodia developed into sporonts and sporocysts in a loose syncytium that gave rise to binucleate and uninucleate sporoblasts from which spores developed. Spores were flask-shaped, 5.6-6.7 x 3.3-4.0 microm, with a characteristic operculum, a few filamentous wrappings and rod-like structures in the posterior sporoplasm. Mature spores had a wall comprising inner (90 nm wide), middle (30 nm wide) and outer (130 nm wide) layers, and a surface coat of microtubules giving them a furry appearance. Oysters with empty gonad follicles were most heavily infected, and oyster condition and mortality appeared to be related to degree of infection.

Aims The E2F transcription factors are best characterized for their roles in cell-cycle regulation, cell growth, and cell death. Here we investigated the potential role of E2F1 in cardiac neovascularization. Methods and results We induced myocardial infarction (MI) by ligating the left anterior descending artery in wild-type (WT) and E2F1−/− mice. E2F1−/− mice demonstrated a significantly better cardiac function and smaller infarct sizes than WT mice. At infarct border zone, capillary density and endothelial cell (EC) proliferation were greater, apoptotic ECs were fewer, levels of VEGF and placental growth factor (PlGF) were higher, and p53 level was lower in E2F1−/− than in WT mice. Blockade of VEGF receptor 2 (VEGFR2) signalling with the selective inhibitor SU5416 or with the VEGFR2-blocking antibody DC101 abolished the differences between E2F1−/− mice and WT mice in cardiac function, infarct size, capillary density, EC proliferation, and EC apoptosis. In vitro , hypoxia-induced VEGF and PlGF up-regulation was significantly greater in E2F1−/− than in WT cardiac fibroblasts, and E2F1 overexpression suppressed PlGF up-regulation in both WT and p53−/− cells; however, VEGF up-regulation was suppressed only in WT cells. E2F1 interacted with and stabilized p53 under hypoxic conditions, and both E2F1 : p53 binding and the E2F1-induced suppression of VEGF promoter activity were absent in cells that expressed an N-terminally truncated E2F1 mutant. Conclusion E2F1 limits cardiac neovascularization and functional recovery after MI by suppressing VEGF and PlGF up-regulation through p53-dependent and -independent mechanisms, respectively.

Deafness can result from a variety of gene defects1. Some genes involved in the physiology of hearing encode membrane transporters that regulate the ionic composition of the fluid bathing the inner ear. The endolymph is an extracellular fluid with an atypical composition that resembles the intracellular milieu, high in K+ and low in Na+. Recent studies have emphasized the prominent role of K+ channels in endolymph secretion2,3,4 and mechanical transduction5. Coupled electroneutral transport of Na+, K+ and Cl- is mediated by two isoforms of the Na-K-2Cl co-transporter: the absorptive isoform BSC1 (also called NKCC2, encoded by Slc12a1 in mouse) that is exclusively expressed in kidney; and BSC2/NKCC1 (encoded by Slc12a2 in mouse), the secretory isoform which has a wider pattern of expression including epithelia, muscle cells, neurons and red blood cells6,7. These co-transporters share 57% homology at the amino acid level8,9,10,11 and are pharmacologically inhibited by loop diuretics. There is functional12,13,14 and histochemical15,16,17 evidence for the presence of the secretory isoform of the Na-K-2Cl co-transporter in gerbil, rat and rabbit inner ear. We disrupted mouse Slc12a2 and report here that Slc12a2-/- mice are deaf and exhibit classic shaker/waltzer behaviour, indicative of inner-ear defects. We localized the co-transporter to key secreting epithelia of the mouse inner ear and show that absence of functional co-transporter leads to structural damages in the inner ear consistent with a decrease in endolymph secretion.

A species of Haplosporidium is described from 6 of 105 pearl oyster (Pinctada maxima) spat from a hatchery at Carnarvon in north Western Australia. Presporulation and sporulation stages occurred in the connective tissue surrounding the digestive gland and were common in mantle connective tissue, but only light to moderate infections were observed in the heart, gills, foot, and adductor muscle. No stages were observed in epithelia, and the gut and diverticulae remained intact. Ultrastructurally, sporoblasts were binucleate with the two nuclei either closely apposed to form a diplokaryon or separated, with the cytoplasm containing round to pyriform haplosporosomes. In spores the sporoplasm contained a basal, or sometimes equatorial, nucleus, dense ovoid vesicles that appeared to develop to ovoid haplosporosomes with an internal axehead-shaped membrane, and spherical haplosporosomes. Apparently senescent spores with a dense content were also present and they, and normal spores, were ornamented with filaments placing the parasite in the genus Haplosporidium. Copyright 1998 Academic Press. Copyright 1998 Academic Press

The Slc12a2 gene encodes a widely expressed bumetanide-sensitive Na+-K+-2Cl−cotransporter that participates in various functions such as Cl−secretion and cell volume regulation. We isolated and characterized 75 kilobases of the murine gene encoding the cotransporter. The cotransport protein is encoded by 27 exons. Ribonuclease protection assay and primer extension demonstrated tissue-specific transcription initiation sites located within 270 base pairs upstream of the start codon. Nucleotide sequence analysis of the proximal 5′-flanking region revealed the presence of a weak TATA box, multiple Sp1/GC consensus sites, and the consensus sequence of a putative transcriptional initiator. Transfection of luciferase reporter gene constructs in mouse inner medullary collecting duct (mIMCD-3) cells confirmed the location of the minimal promoter within a 120-base pair fragment upstream of the cDNA. We also report the identification of an alternatively spliced variant of the cotransporter, expressed primarily in brain. This new spliced variant lacks exon 21, which encodes a 16-amino acid peptide located in the COOH-terminal tail of the protein. The absence of this exon causes the loss of the single protein kinase A consensus site of the cotransport protein.

Introduction: Locally transplanted human CD34 + stem cells have been shown to improve exercise tolerance in patients with myocardial ischemia and promote angiogenesis in animal models. Recently we have demonstrated that CD34 + cells secrete exosomes, membrane bound nano-vesicles, as a major component of their paracrine secretion which induces angiogenesis. We hypothesize that cell-free exosomes from CD34 + cells (CD34 Exo) mimic the beneficial effects of cells, and promote myocardial revascularization and repair via transfer of pro-angiogenic microRNAs, possibly to endothelial cells. Methods and Results: Therapeutic potential of CD34 Exo isolated from equal number of adult human peripheral blood-derived CD34 + cells was evaluated in a murine model of myocardial ischemia (MI). Similar to cells, treatment with CD34 Exo resulted in significant improvement in ischemia compared to treatment with PBS (ejection fraction, 42±4 v 22±6%; capillary density, 113±7 v 66±6/HPF; fibrosis 27±2 v 48±7%, p Conclusion: CD34 + exosomes transfer miR126 to endothelial cells to induce angiogenesis and myocardial repair. The functional benefits associated with CD34 + cell therapy may be mediated by exosomes-mediated transfer of angiogenic microRNAs to endothelial cells.

We have shown previously that estrogen (estradiol, E2) supplementation enhances voluntary alcohol consumption in ovariectomized female rodents and that increased alcohol consumption impairs ischemic hind limb vascular repair. However, the effect of E2-induced alcohol consumption on post-infarct myocardial repair and on the phenotypic/functional properties of endothelial progenitor cells (EPCs) is not known. Additionally, the molecular signaling of alcohol-estrogen interactions remains to be elucidated. This study examined the effect of E2-induced increases in ethanol consumption on post-infarct myocardial function/repair. Ovariectomized female mice, implanted with 17β-E2 or placebo pellets were given access to alcohol for 6 weeks and subjected to acute myocardial infarction. Left ventricular functions were consistently depressed in mice consuming ethanol compared with those receiving only E2. Alcohol-consuming mice also displayed significantly increased infarct size and reduced capillary density. Ethanol consumption also reduced E2-induced mobilization and homing of EPCs to injured myocardium compared with the E2-alone group. In vitro, exposure of EPCs to ethanol suppressed E2-induced proliferation, survival, and migration and markedly altered E2-induced estrogen receptor-dependent cell survival signaling and gene expression. Furthermore, ethanol-mediated suppression of EPC biology was endothelial nitric oxide synthase-dependent because endothelial nitric oxide synthase-null mice displayed an exaggerated response to post-acute myocardial infarction left ventricular functions. These data suggest that E2 modulation of alcohol consumption, and the ensuing EPC dysfunction, may negatively compete with the beneficial effects of estrogen on post-infarct myocardial repair.

Background— CXC-chemokine receptor 4 (CXCR4) regulates the retention of stem/progenitor cells in the bone marrow (BM), and the CXCR4 antagonist AMD3100 improves recovery from coronary ligation injury by mobilizing stem/progenitor cells from the BM to the peripheral blood. Thus, we investigated whether AMD3100 also improves recovery from ischemia/reperfusion injury, which more closely mimics myocardial infarction in patients, because blood flow is only temporarily obstructed. Methods and Results— Mice were treated with single subcutaneous injections of AMD3100 (5 mg/kg) or saline after ischemia/reperfusion injury. Three days later, histological measurements of the ratio of infarct area to area at risk were smaller in AMD3100-treated mice than in mice administered saline, and echocardiographic measurements of left ventricular function were greater in the AMD3100-treated mice at week 4. CXCR4 + cells were mobilized for just 1 day in both groups, but the mobilization of sca1 + /flk1 + cells endured for 7 days in AMD3100-treated mice compared with just 1 day in the saline-treated mice. AMD3100 upregulated BM levels of endothelial nitric oxide synthase (eNOS) and 2 targets of eNOS signaling, matrix metalloproteinase-9 and soluble Kit ligand. Furthermore, the loss of BM eNOS expression abolished the benefit of AMD3100 on sca1 + /flk1 + cell mobilization without altering the mobilization of CXCR4 + cells, and the cardioprotective effects of AMD3100 were retained in eNOS-knockout mice that had been transplanted with BM from wild-type mice but not in wild-type mice with eNOS-knockout BM. Conclusions— AMD3100 prolongs BM progenitor mobilization and improves recovery from ischemia/reperfusion injury, and these benefits appear to occur through a previously unidentified link between AMD3100 and BM eNOS expression.

Introduction: Locally transplanted human CD34+ hematopoietic stem cells have stimulated neovascularization in preclinical studies and have been associated with functional improvements in phase I and II clinical trials of patients with ischemic cardiovascular diseases. Recently, we have demonstrated that membrane-bound nano-vesicles called exosomes are one of the primary pro-angiogenic components of human CD34+ cell paracrine secretion that induced angiogenesis independently of the cells. Here, we hypothesize that the functional benefits associated with CD34+ cell therapy are primarily mediated by the secretion of exosomes (Exo), and that CD34+ Exo transfer pro-angiogenic microRNAs to promote angiogenesis and ischemic tissue repair. Methods and Results: Therapeutic potential of CD34+ Exo isolated from adult human peripheral blood-derived CD34+ cells was evaluated in a mouse model of hind limb ischemia (HLI). Similar to CD34+ cells, administration of CD34+ Exo from equal number of cells induced angiogenesis and tissue repair; it significantly improved perfusion (ratio: 1.01±0.04 v 0.57±0.1, P Conclusion: CD34+ exosomes transfer the pro-angiogenic miR-126 to endothelial cells in the ischemic tissues to induce angiogenesis and ischemic tissue repair. Our study illustrates a mechanism of stem cell communication involving intercellular traffic of miRNAs via exosomes to induce functional recovery.

Background— Critical limb ischemia portends a risk of major amputation of 25% to 35% within 1 year of diagnosis. Preclinical studies provide evidence that intramuscular injection of autologous CD34+ cells improves limb perfusion and reduces amputation risk. In this randomized, double-blind, placebo-controlled pilot study, we evaluated the safety and efficacy of intramuscular injections of autologous CD34+ cells in subjects with moderate or high-risk critical limb ischemia, who were poor or noncandidates for surgical or percutaneous revascularization (ACT34-CLI). Methods and Results— Twenty-eight critical limb ischemia subjects were randomized and treated: 7 to 1×10 5 (low-dose) and 9 to 1×10 6 (high-dose) autologous CD34+ cells/kg; and 12 to placebo (control). Intramuscular injections were distributed into 8 sites within the ischemic lower extremity. At 6 months postinjection, 67% of control subjects experienced a major or minor amputation versus 43% of low-dose and 22% of high-dose cell-treated subjects ( P =0.137). This trend continued at 12 months, with 75% of control subjects experiencing any amputation versus 43% of low-dose and 22% of high-dose cell-treated subjects ( P =0.058). Amputation incidence was lower in the combined cell-treated groups compared with control group (6 months: P =0.125; 12 months: P =0.054), with the low-dose and high-dose groups individually showing trends toward improved amputation-free survival at 6 months and 12 months. No adverse safety signal was associated with cell administration. Conclusions— This study provides evidence that intramuscular administration of autologous CD34+ cells was safe in this patient population. Favorable trends toward reduced amputation rates in cell-treated versus control subjects were observed. These findings warrant further exploration in later-phase clinical trials. Clinical Trial Registration— URL: http://www.clinicaltrials.gov . Unique identifier: NCT00616980

Local transplantation of human CD34+ hematopoietic stem cells has been shown to promote neovascularization in pre-clinical studies in models of myocardial and limb ischemia. In early phase clinical trials, transplantation of CD34+ cells has been associated with reduced angina, improved exercise time and reduced amputation rates. Several studies have suggested that paracrine effects by these pro-angiogenic cells mediate the effects induced by cell transplantation. We hypothesized that CD34+ cells secrete exosomes (Exo), which mediate at least a part of the therapeutic function of the cells. Methods and Results: We isolated Exo from the conditioned media of adult human peripheral blood (PB) CD34+ cells. The angiogenic and therapeutic potency of CD34+ Exo was compared with the intact CD34+ cells and also with PB mononuclear cell (MNC) Exo. Exo from both CD34+ cells and MNC are 50–90nm in size, have cup shaped morphology, and carry known Exo-marker proteins such as CD63, TSG101 and Annexin V as shown by electron microscopy, Western blot and flow cytometry. Compared to CD34+ cells or MNC Exo, CD34+ Exo significantly induces in vitro angiogenic activities such as viability, proliferation and tube formation of HUVECs on matrigel- in a dose dependent manner. In vivo, CD34+ Exo stimulated significant neovascularization in mouse corneal angiogenesis assay (14±4 mm v MNC Exo, 4±1 mm, p Conclusions: These data demonstrate that CD34+ Exo induce angiogenic activity and ischemic tissue repair in the absence of CD34+ cells, and suggest that Exo represent important mediators of the therapeutic effects associated with CD34+ cell therapy. We speculate that Exo derived from CD34+ cells may represent a significant component of the paracrine effect of progenitor-cell transplantation for therapeutic angiogenesis.

Background: Hypertrophy associated heart failure remain the leading cause of death worldwide. Inflammatory cytokines play critical role in adverse cardiac remodeling and heart failure. Therefore, approaches geared towards inhibiting cardiac inflammation may provide therapeutic benefits. Thus, we tested the hypothesis that anti-inflammatory cytokine, IL-10, therapy might inhibit pressure overload-induced cardiac remodeling. Methods and Results: Cardiac hypertrophy was induced in Wild-type (WT) and IL-10-knockout (KO) mice by isoproterenol (ISO; 45mg/kg b.wt./day, 14 days) infusion through mini-osmotic pumps. Control groups mice received saline. ISO-induced increase in heart weight/tibia length ratio in WT was further increased in KO mice. ISO-mediated cardiac dysfunction (%EF and %FS) in WT mice were exaggerated in KO mice. KO mice displayed higher expression of fetal genes (ANP and BNP) and inflammatory cytokines (TNFα and IL-1β). ISO-treated KO mice had notably higher fibrosis and apoptosis than the WT. Interestingly, systemic recombinant IL-10 administration markedly attenuated effects of ISO and improved left ventricle function, reversed fetal gene expression, fibrosis and apoptosis both in WT and in KO mice. To further understand the mechanism of IL-10 protection, NRCM and H9C2 cells were treated with ISO (10µM) and/or IL-10 (20ng/mL), in vitro . ISO significantly increased the mRNA expression of ANP and BNP as well as of inflammatory cytokines which was markedly reduced by IL-10. ISO treatment also induced the activation of p38, ERK1/2 MAP kinases and of NFkB while it inhibited STAT-3 phosphorylation. Interestingly, co-treatment with IL-10 suppressed p38 and ERK1/2 phosphorylation while enhancing STAT-3 phosphorylation. Interestingly, ISO-induced nuclear translocation of NFkB was mimicked by STAT3 specific inhibitor cucurbitacin, suggesting STAT3 as the downstream target of IL-10 effects. Conclusion: Our studies suggest that IL-10 treatment not only inhibits the progression but also reverses the pressure overload-induced adverse cardiac remodeling. Ongoing investigations will further provide a better understanding on the mechanistic and therapeutic aspects of IL-10 on hypertrophic remodeling and heart failure.

Rationale: Transplantation of human CD34 + stem cells to ischemic tissues has been associated with reduced angina, improved exercise time, and reduced amputation rates in phase 2 clinical trials and has been shown to induce neovascularization in preclinical models. Previous studies have suggested that paracrine factors secreted by these proangiogenic cells are responsible, at least in part, for the angiogenic effects induced by CD34 + cell transplantation. Objective: Our objective was to investigate the mechanism of CD34 + stem cell–induced proangiogenic paracrine effects and to examine if exosomes, a component of paracrine secretion, are involved. Methods and Results: Exosomes collected from the conditioned media of mobilized human CD34 + cells had the characteristic size (40 to 90 nm; determined by dynamic light scattering), cup-shaped morphology (electron microscopy), expressed exosome-marker proteins CD63, phosphatidylserine (flow cytometry) and TSG101 (immunoblotting), besides expressing CD34 + cell lineage marker protein, CD34. In vitro, CD34 + exosomes replicated the angiogenic activity of CD34 + cells by increasing endothelial cell viability, proliferation, and tube formation on Matrigel. In vivo, the CD34 + exosomes stimulated angiogenesis in Matrigel plug and corneal assays. Interestingly, exosomes from CD34 + cells but not from CD34 + cell–depleted mononuclear cells had angiogenic activity. Conclusions: Our data demonstrate that human CD34 + cells secrete exosomes that have independent angiogenic activity both in vitro and in vivo. CD34 + exosomes may represent a significant component of the paracrine effect of progenitor cell transplantation for therapeutic angiogenesis.

Aging is a risk factor for coronary and peripheral artery disease. The role of TNF-α receptors (TNFR1/p55 and TNFR2/p75) in post-acute myocardial infarction (post-AMI) recovery is not well understood. We hypothesized that TNF signaling through its receptors p55 and p75 may be essential in post-AMI regeneration in adult heart. To test our hypothesis we evaluated post-AMI survival, cardiac function, apoptosis, and angiogenesis in AMI model (LAD ligation) in age-matched young (4–8 weeks old) and old (9–14 months old) WT, p75KO, and p55KO mice. In old WTs there was significant fourfold age-associated increase in post-AMI mortality. In young p75KOs post-AMI mortality was approaching mortality in old WTs (35% vs. 45%) whereas >1/2 of old p75KOs (60%) died within 7 days post-AMI. No post-AMI mortality was observed in young p55KOs, and in old p55KOs post-AMI mortality was lower than in young WTs (10% vs. 15%). Compared to young WT, between days 7 and 28 post-AMI functional recovery (% left ventricular (LV) fractional shortening (FS)) was 10% lower in old WTs and young p75KOs (p

We hypothesized that a small molecule CXCR4 antagonist, AMD3100 (AMD), could augment the mobilization of bone marrow (BM)-derived endothelial progenitor cells (EPCs), thereby enhancing neovascularization and functional recovery after myocardial infarction. Single-dose AMD injection administered after the onset of myocardial infarction increased circulating EPC counts and myocardial vascularity, reduced fibrosis, and improved cardiac function and survival. In mice transplanted with traceable BM cells, AMD increased BM-derived cell incorporation in the ischemic border zone. In contrast, continuous infusion of AMD, although increasing EPCs in the circulation, worsened outcome by blocking EPC incorporation. In addition to its effects as a CXCR4 antagonist, AMD also up-regulated VEGF and matrix metalloproteinase 9 (MMP-9) expression, and the benefits of AMD were not observed in the absence of MMP-9 expression in the BM. These findings suggest that AMD3100 preserves cardiac function after myocardial infarction by enhancing BM-EPC–mediated neovascularization, and that these benefits require MMP-9 expression in the BM, but not in the ischemic region. Our results indicate that AMD3100 could be a potentially useful therapy for the treatment of myocardial infarction.

Prolonged inflammatory response is associated with left ventricular (LV) dysfunction and adverse remodeling following myocardial infarction (MI). IL-10 inhibits inflammation by suppressing HuR-mediated mRNA stabilization of proinflammatory cytokines. Here we report that following MI, IL-10−/− mice showed exaggerated LV dysfunction, fibrosis, and cardiomyocyte apoptosis. Short-hairpin RNA (shRNA)-mediated knockdown of HuR in the myocardium significantly reversed MI-induced LV dysfunctions and LV remodeling. HuR knockdown significantly reduced MI-induced cardiomyocyte apoptosis concomitant with reduced p53 expression. Moreover, HuR knockdown significantly reduced infarct size and fibrosis area, which in turn was associated with decreased TGF-β expression. In vitro, stable knockdown of HuR in mouse macrophage cell line RAW 264.7 corroborated in vivo data and revealed reduced mRNA expression of TNF-α, TGF-β, and p53 following LPS challenge, which was associated with a marked reduction in the mRNA stability of these genes. Taken together, our studies suggest that HuR is a direct target of IL-10, and HuR knockdown mimics anti-inflammatory effects of IL-10.—Krishnamurthy, P., Lambers, E., Verma, S., Thorne, T., Qin, G., Losordo, D. W., Kishore, R. Myocardial knockdown of mRNA-stabilizing protein HuR attenuates post-MI inflammatory response and left ventricular dysfunction in IL-10-null mice.

Telomere homolog oligonucleotides (T-oligos) activate an innate telomere-based program that leads to multiple anticancer effects. T-oligos act at telomeres to initiate signaling through the Werner protein and ATM kinase. We wanted to determine if T-oligos have antiangiogenic effects. We found that T-oligo-treated human melanoma (MM-AN) cells had decreased expression of vascular endothelial growth factor (VEGF), VEGF receptor 2, angiopoeitin-1 and -2 and decreased VEGF secretion. T-oligos activated the transcription factor E2F1 and inhibited the activity of the angiogenic transcription factor, HIF-1α. T-oligos inhibited EC tubulogenesis and total tumor microvascular density matrix invasion by MM-AN cells and ECs in vitro. In melanoma SCID xenografts, two systemic T-oligo injections decreased by 60% (P<.004) total tumor microvascular density and the functional vessels density by 80% (P<.002). These findings suggest that restriction of tumor angiogenesis is among the host's innate telomere-based anticancer responses and provide further evidence that T-oligos may offer a powerful new approach for melanoma treatment.

BackgroundWe have shown that the Sonic Hedgehog (Shh) embryonic signalling pathway can be reactivated in myocardial infarction (MI) in adults inducing expression of pro-angiogenic factors. We hypothesized that combining Shh gene therapy and endothelial BM-derived pro-angiogenic cell mobilization by a CXCR4 antagonist, AMD3100 (AMD), could exert synergistic effects and would be superior to either single strategy for the treatment of MI.Methods/resultsIn vivo, MI was induced in WT and GFP-bone marrow (BM) transplanted mice randomly assigned in 4 treatment groups: control; AMD (single dose, 5mg/kg s.c.); Shh (intramyocardial; 100μg Shh plasmid DNA at time of MI surgery); AMD+Shh group. Left ventricular ejection fraction (LVEF) was evaluated by echo up to 4 weeks post MI. AMD+Shh group exhibited the best LV function. Furthermore, combination of AMD with sub-therapeutic dose of Shh resulted in a significant improvement of cardiac function recovery compared to monotherapy, highlighting its synergistic effect (P

Rationale : The Gli transcription factors are mediators of Hedgehog (Hh) signaling and have been shown to play critical roles during embryogenesis. Previously, we have demonstrated that the Hh pathway is reactivated by ischemia in adult mammals, and that this pathway can be stimulated for therapeutic benefit; however, the specific roles of the Gli transcription factors during ischemia-induced Hh signaling have not been elucidated. Objective : To investigate the role of Gli3 in ischemic tissue repair. Methods and Results : Gli3-haploinsufficient (Gli3 +/− ) mice and their wild-type littermates were physiologically similar in the absence of ischemia; however, histological assessments of capillary density and echocardiographic measurements of left ventricular ejection fractions were reduced in Gli3 +/− mice compared to wild-type mice after surgically induced myocardial infarction, and fibrosis was increased. Gli3-deficient mice also displayed reduced capillary density after induction of hindlimb ischemia and an impaired angiogenic response to vascular endothelial growth factor in the corneal angiogenesis model. In endothelial cells, adenovirus-mediated overexpression of Gli3 promoted migration (modified Boyden chamber), small interfering RNA–mediated downregulation of Gli3 delayed tube formation (Matrigel), and Western analyses identified increases in Akt phosphorylation, extracellular signal-regulated kinase (ERK)1/2 activation, and c-Fos expression; however, promoter–reporter assays indicated that Gli3 overexpression does not modulate Gli-dependent transcription. Furthermore, the induction of endothelial cell migration by Gli3 was dependent on Akt and ERK1/2 activation. Conclusions : Collectively, these observations indicate that Gli3 contributes to vessel growth under both ischemic and nonischemic conditions and provide the first evidence that Gli3 regulates angiogenesis and endothelial cell activity in adult mammals.

Rationale and Objectives The morphogen Sonic Hedgehog (Shh) is known to promote neovascularization in adults via indirect induction of pro-angiogenic cytokine expression by fibroblasts. Direct effects of Shh on endothelial cell (EC) function and angiogenesis, however, have not been characterized. Accordingly, we performed a series of in vitro and in vivo studies to evaluate the direct effects of Shh on EC and to investigate certain mechanisms by which Shh modulates angiogenesis. Methods and Results Our data disclose that Shh promotes capillary morphogenesis (tube length on Matrigel™ increased to 271±50 % of the length in untreated cells), induces EC migration (191±35 %) and increases EC expression of matrix metalloproteinase 9 (MMP-9) and osteopontin (OPN), which are shown to be essential for Shh-induced angiogenesis both in vitro and in vivo. Shh effects in ECs, however, occur while Gli-dependent transcription is not modulated. Furthemore, our studies show that changes in gene expression and EC migration are mediated by Shh induction of Rho. The Rho dependence of Shh-induced EC angiogenic activity is documented in vitro using dominant negative constructs for RhoA and Rho kinase (ROCK), showing that RhoA and ROCK blockade attenuates Shh induced migration and tube formation, as well as the Shh induced expression of MMP-9 and OPN. In vivo in the mouse corneal angiogenesis model pharmacologic inhibition of ROCK blocks Shh induced angiogenesis, confirming the ROCK dependence of this process. Furthermore, in MMP-9 and OPN null mice Shh induced angiogenesis also blocked, indicating that Shh induced angiogenesis is also dependent on MMP-9 and OPN expression Conclusion These data elucidate an entirely novel, “nonclassical” pathway by which Shh directly modulates EC phenotype and angiogenic activity.

Background: Prior data indicate that estradiol (E2) favorably affects neovascularization in injured tissue, and that Sonic Hedgehog (Shh)-induced neovascularization is critical for nerve regeneration; however, little is known about the relationship between E2 and Shh signaling. We tested the hypothesis that E2 potentiates nerve regeneration via Shh-activated neoangiogen-esis. Methods and Results: Ovariectomized mice were subjected to unilateral sciatic nerve crush injury and treated with either E2 (via locally administered biodegradable polymer) or placebo (polymer alone). E2 treatment resulted in greater functional recovery of the nerve as evaluated by both exercise duration (P Conclusions: E2 accelerates the functional recovery of injured nerves by enhancing angiogenesis. We propose that these effects occur in part through the inhibition of the Shh inactivator HIP, thereby preserving Shh activity after nerve injury. These findings may have identified a novel regulatory mechanism for nerve repair via E2-enhaced, Shh-mediated angiogenesis.

Gli transcription factors are mediators of hedgehog signaling and have been shown to be critical in several steps during development. We have shown that the Hedgehog pathway is reactivated in the adult cardiovascular system under ischemic conditions, however the specific role of Gli3 has not been elucidated. Adenoviral mediated overexpression of Gli3 promotes HUVEC migration (250±58% of control, p+/− (Gli3 +/XtJ ) mice, a well established model of reduced Gli3 expression. VEGF-induced corneal angiogenesis was impaired in Gli3 +/− mice compared to WT. The role of Gli3 in angiogenesis was then confirmed in two ischemia models. Hind-limb ischemia (HLI) was induced by resection of the left femoral artery. Capillary density was reduced by a mean of 48.40±12.08% in Gli3 +/− mice vs. WT 7, 14 and 28 days. Myocardial infarction (MI) was induced by ligation of the LAD. 28 days after MI, left ventricular function assessed by echo and histological analysis revealed that Gli3 +/− mice exhibit reduced ejection fraction (27.92±4.49% versus 37.56±7.02% for the WT, p=0.004), increased fibrosis area (33.65±9.73% versus 19.81±5.40% for the WT, p=0.007) and a decrease capillary density in the ischemic and border zones. These data indicate that Gli3 deficiency leads to impaired angiogenesis in both ischemic and non ischemic conditions. Moreover, the impairment in ischemia induced neovascularization is associated with more severe impairment of cardiac function after MI. The mechanism of Gli3’s effects was then investigated in vitro . Promoter reporter assays revealed that Gli3 overexpression inhibits Gli-dependent transcription, while Western analysis show increased Akt phosphorylation, activation of the ERK1/2 and increased c-Fos expression. Using a dominant negative Akt expressing virus and a MEK1/2 inhibitor, we show that Gli3 induced-EC migration is dependent on Akt and ERK1/2. These studies provide the first evidence that the Gli3 transcription factor regulates angiogenesis and EC phenotype.

The morphogen Sonic Hedgehog (Shh) is known to promote neovascularization in adults via indirect induction of pro-angiogenic cytokine expression by fibroblasts. Direct effects of Shh on endothelial cell (EC) function and angiogenesis, however, have not been characterized. Accordingly, we performed a series of in vitro and in vivo studies to evaluate the direct effects of Shh on EC and to investigate certain mechanisms by which Shh modulates angiogenesis. Our data disclose that Shh promotes capillary morphogenesis (tube length on Matrigel ™ increased to 271±50% of the length in untreated cells), induces EC migration (191±35%) and increases EC expression of matrix metalloproteinase 9 (MMP-9) and osteopontin (OPN), which are shown to be essential for Shh-induced angiogenesis both in vitro and in vivo . Shh effects in ECs, however, occur while Gli-dependent transcription is not modulated. Furthemore, our studies show that changes in gene expression and EC migration are mediated by Shh induction of Rho. The Rho dependence of Shh-induced EC angiogenic activity is documented in vitro using dominant negative constructs for RhoA and Rho kinase (ROCK), showing that RhoA and ROCK blockade attenuates Shh induced migration and tube formation, as well as the Shh induced expression of MMP-9 and OPN. In vivo in the mouse corneal angiogenesis model pharmacologic inhibition of ROCK blocks Shh induced angiogenesis, confirming the ROCK dependence of this process. Furthermore, in MMP-9 and OPN null mice Shh induced angiogenesis also blocked, indicating that Shh induced angiogenesis is also dependent on MMP-9 and OPN expression. These data elucidate an entirely novel, “non-classical” pathway by which Shh directly modulates EC phenotype and angiogenic activity

Gli transcription factors are mediators of hedgehog signaling and have been shown to be critical in several steps during development. In addition, Gli transcription factors have also been implicated as potent oncogenes. We have shown that the Hedgehog pathway is reactivated in the adult cardiovascular system under ischemic conditions and that the hedgehog pathway can be exploited therapeutically in ischemic disease; however the role and expression of the Gli transcription factors in the response to injury following ischemia have not been characterized. We induced hind-limb ischemia by resection of the left femoral artery of FVB mice and found that Gli2 and Gli3 mRNA were overexpressed in the ischemic tissue up to 4-fold and 9-fold respectively while Gli1 expression was not modulated. Immunostaining revealed that several cell types overexpressed Gli2 and Gli3 including myocytes and endothelial cells (ECs). To investigate the role and mechanism of action of Gli2 and Gli3, in vitro experiments were first performed. Overexpression of Gli2 and Gli3 promotes myoblast survival and proliferation. In ECs, overexpression of Gli2 and Gli3 promote survival and migration as well as induce expression of proteins involved in angiogenesis such as MMP-9 and osteopontin. To confirm the hypothesis of a favorable role of Gli2 and Gli3 in neovascularization and tissue repair following ischemic injury, adenovirus encoding LacZ, Gli2 and Gli3 were administrated locally in the tibialis anterior muscle, 2 days before hind limb ischemia surgery was performed. Both Ad-Gli2 and Ad-Gli3 treated mice exhibited higher proliferation in the regenerating muscle 7 days after ischemia. Moreover, Ad-Gli3 treated mice display higher capillary density (38.9±10.2 vessels/HPF vs. 26.1±6.1 in the control mice, p=0.012) and limb perfusion (the ratio of the perfusion of the ischemic leg vs. the control leg was 1.07±0.20 vs. 0.62±0,16 for the control mice, p=0.0003) 7 and 14 day after ischemia respectively. These data indicate that Gli2 and Gli3, transcription factors of the hedgehog pathway, are overexpressed in ischemic tissue and participate in tissue repair by promoting both neovascularization and proliferation and survival of myoblasts.

The oocyte-independent source for the generation of pluripotent stem cells is among the ultimate goals in regenerative medicine. We report that on exposure to mouse embryonic stem cell (mESC) extracts, reversibly permeabilized NIH3T3 cells undergo dedifferentiation followed by stimulus-induced redifferentiation into multiple lineage cell types. Genome-wide expression profiling revealed significant differences between NIH3T3 control and ESC extract–treated NIH3T3 cells including the reactivation of ESC-specific transcripts. Epigenetically, ESC extracts induced CpG demethylation of Oct4 promoter, hyperacetylation of histones 3 and 4, and decreased lysine 9 (K-9) dimethylation of histone 3. In mouse models of surgically induced hindlimb ischemia or acute myocardial infarction transplantation of reprogrammed NIH3T3 cells significantly improved postinjury physiological functions and showed anatomic evidence of engraftment and transdifferentiation into skeletal muscle, endothelial cell, and cardiomyocytes. These data provide evidence for the generation of functional multipotent stem-like cells from terminally differentiated somatic cells without the introduction of retroviral mediated transgenes or ESC fusion.

Background: Clinical trials of autologous stem/progenitor cell transplantation in ischemic heart diseases are now on-going. Simultaneously, mounting evidence suggests that age related decreases in EPC number or function may limit this therapeutic approach. We tested the hypothesis that gene modification of aged EPCs, using the embryonic signaling molecule, sonic hedgehog (Shh), may ameliorate aging induced dysfunction of EPCs and thereby enhance the reparative effect of autologous EPCs. Methods and Results: EPCs from aged mice (24 m.o.), previously shown to exhibit impaired potency, were used and compared to EPCs from young (3 m.o.) mice. Shh gene transfer significantly improved proliferation and anti-apoptosis activities vs. empty vector transfected (EV) aged EPCs, up to a similar level of EV young EPCs. Next, we evaluated the therapeutic effect of Shh-gene-modified aged EPCs (Shh-EPC) vs. EV aged EPCs (EV-EPC) vs. PBS (Ctrl) injection in a mouse AMI model. Shh-EPCs or EV-EPCs (1000 cells) or PBS was injected into the ischemic myocardium immediately following MI. Scar length in the infarcted LV 14 days after surgery was significantly reduced in the Shh-EPC group compared to the EV-EPC group and the PBS group associated with increased capillary density in the peri-infarct area. In addition, Ki67 positive cardiomyocytes were observed with increased frequency in the Shh-EPC group. In Tie2-LacZ BMT mice, beta-gal positive-endogenous BM-derived EPC recruitment was significantly greater in ischemic myocardium in the Shh-EPC group than that in the EV-EPC group. Differentiation of recruited EPCs into endothelial cells or cardiomyocytes was also observed more frequently in the Shh-EPC group compared to the EV-EPC group. These data suggest that cardiac repair was induced by a small number of transplanted Shh gene modified aged EPCs with the increased paracrine effects following MI. Conclusion: Shh gene transfer to aged EPCs ameliorates aging-induced EPC dysfunction. Intramyocardial transplantation of Shh-gene-modified aged EPCs augments therapeutic efficacy for myocardial repair following MI by promoting endogenous EPC recruitment. Shh gene modified EPCs may represent a second-generation EPC-based therapeutic strategy in ischemic heart disease.

E2F transcription factors play critical roles in cell cycle regulation but their cardiovascular specific functions are not well defined. Recent studies have revealed a polymorphism in Endothelin Converting Enzyme-1b (ECE-1b) promoter (C-338A), located within E2F consensus site, which is strongly associated with blood pressure (BP) values in hypertensive women. ECE-1, with four isoforms ECE-1a/b/c/d expressed by the use of alternative promoters, is the major enzyme that catalyzes the biogenesis of the potent vessel-constricting peptide endothelin-1 (ET-1) from its inactive precursor Big-ET-1. The role of E2Fs in ECE-1 bioactivity and BP regulation, however, is unknown. Here we provide evidence that E2F2- but not E2F1-deficient mice display an elevated arterial BP. Loss of E2F2 leads to an aortic artery hypercontractility in response to Big-ET-1, indicating an increased ECE-1 bioactivity. ECE-1b promoter-reporter assays, combined with either E2F2 overexpression or knockdown, confirm that E2F2 regulates ECE-1b transcription. The incorporation of C-338A polymorphism in the promoter confers a higher basal level of the promoter activity and blunts the induction of ECE-1b by E2F2. Among all four isoforms, ECE-1b has been suggested to localize in the late endosome and heterodimerize with cell surface ECE-1a/c/d isoforms for lysosomal degradation, thereby down-regulating their activities. Indeed, we found that knockdown of E2F2 leads to a reduced cytosolic however an increased plasma membrane ECE-1 immunoactivity, corroborating with the hypercontractility of E2F2-deficient vessels. These data indicate that in the normal “non-proliferating” vessels, E2F2 plays a critical role in the maintenance of vascular tone. Deregulated E2F2 activity may contribute to the pathogenesis of hypertension.

The oocyte-independent generation of multipotent stem cells is one of the goals in regenerative medicine. We report that upon exposure to mouse ES cell (ESC) extracts, reversibly permeabilized NIH3T3 cells undergo de-differentiation followed by stimulus-induced re-differentiation into multiple lineage cell types. Genome-wide expression profiling revealed significant differences between NIH3T3 and ESC-extract treated NIH3T3 cells including re-activation of ESC specific transcripts. Epigenetically, ESC extracts induced CpG de-methylation of Oct4 promoter, hyper-acetylation of histones 3 and 4 and decreased lysine 9 (K-9) dimethylation of histone 3. In mouse models of surgically-induced hind limb ischemia (HLI) or acute myocardial infarction (AMI) transplantation of reprogrammed NIH3T3 cells significantly improved post-injury physiological functions and showed antomical evidence of engraftment and trans-differentiation into skeletal muscle, endothelial cell and cardiomyocytes. These data provide evidence for the generation of functional multi-potent stem like cells from terminally differentiated somatic cells without the introduction of trans-genes or ESC fusion.

Background— A growing population of patients with coronary artery disease experiences angina that is not amenable to revascularization and is refractory to medical therapy. Preclinical studies have indicated that human CD34 + stem cells induce neovascularization in ischemic myocardium, which enhances perfusion and function. Methods and Results— Twenty-four patients (19 men and 5 women aged 48 to 84 years) with Canadian Cardiovascular Society class 3 or 4 angina who were undergoing optimal medical treatment and who were not candidates for mechanical revascularization were enrolled in a double-blind, randomized (3:1), placebo-controlled dose-escalating study. Patients received granulocyte colony-stimulating factor 5 μg · kg −1 · d −1 for 5 days with leukapheresis on the fifth day. Selection of CD34 + cells was performed with a Food and Drug Administration–approved device. Electromechanical mapping was performed to identify ischemic but viable regions of myocardium for injection of cells (versus saline). The total dose of cells was distributed in 10 intramyocardial, transendocardial injections. Patients were required to have an implantable cardioverter-defibrillator or to temporarily wear a LifeVest wearable defibrillator. No incidence was observed of myocardial infarction induced by mobilization or intramyocardial injection. The intramyocardial injection of cells or saline did not result in cardiac enzyme elevation, perforation, or pericardial effusion. No incidence of ventricular tachycardia or ventricular fibrillation occurred during the administration of granulocyte colony-stimulating factor or intramyocardial injections. One patient with a history of sudden cardiac death/ventricular tachycardia/ventricular fibrillation had catheter-induced ventricular tachycardia during mapping that required cardioversion. Serious adverse events were evenly distributed. Efficacy parameters including angina frequency, nitroglycerine usage, exercise time, and Canadian Cardiovascular Society class showed trends that favored CD34 + cell–treated patients versus control subjects given placebo. Conclusions— A randomized trial of intramyocardial injection of autologous CD34 + cells in patients with intractable angina was completed that provides evidence for feasibility, safety, and bioactivity. A larger phase IIb study is currently under way to further evaluate this therapy.

Impaired wound healing is a common complication of diabetes. Although it is well known that both macrophages and blood vessels are critical to wound repair, the role of wound-associated lymphatic vessels has not been well investigated. We report that both the presence of activated macrophages and the formation of lymphatic vessels are rate-limiting to the healing of diabetic wounds. We have previously shown that macrophages contribute to the lymphatic vessels that form during the acute phase of corneal wound healing. We now demonstrate that this is a general phenomenon; cells that co-stain for the macrophage marker F4/80 and the lymphatic markers LYVE-1 (lymphatic vascular endothelium hyaluronate receptor) and podoplanin contribute to lymphatic vessels in full-thickness wounds. LYVE-1-positive lymphatic vessels and CD31-positive blood vessels were significantly reduced in corneal wound healing in diabetic mice (db/db) (P0.02) compared with control (db/+) mice. Glucose treatment of control macrophages led to the down-regulation of the lymphatic-specific receptor VEGFR3 and its ligands, vascular endothelial growth factor-C and -D (VEGF-C, -D). Interleukin-1beta stimulation rescued diabetic macrophage function; application of interleukin-1beta-treated db/db-derived macrophages to wounds in db/db mice induced lymphatic vessel formation and accelerated wound healing. These observations suggest a potential therapeutic approach for healing wounds in diabetic patients.

Background—Estradiol (E2) modulates the kinetics of circulating endothelial progenitor cells (EPCs) and favorably affects neovascularization after ischemic injury. However, the roles of estrogen receptors α (ERα) and β (ERβ) in EPC biology are largely unknown.Methods and Results—In response to E2, migration, tube formation, adhesion, and estrogen-responsive element–dependent gene transcription activities were severely impaired in EPCs obtained from ERα-knockout mice (ERαKO) and moderately impaired in ERβKO EPCs. The number of ERαΚΟ EPCs (42.4±1.5;PP=0.03) incorporated into the ischemic border zone was reduced as compared with wild-type (WT) EPCs (72.5±1.3). In bone marrow transplantation (BMT) models, the number of mobilized endogenous EPCs in E2-treated mice was significantly reduced in ERαKO BMT (WT mice transplanted with ERαKO bone marrow) (2.03±0.18%;P=0.004 versus WT BMT) and ERβKO BMT (2.62±0.07%;P=0.02 versus WT) compared with WT BMT (2.87±0.13%) (WT to WT BMT as control) mice. Capillary density at the border zone of ischemic myocardium also was significantly reduced in ERαKO BMT and ERβKO BMT compared with WT mice (WT BMT, 1718±75/mm2; ERαKO BMT, 1107±48/mm2; ERβKO BMT, 1567±50/mm2). ERα mRNA was expressed more abundantly on EPCs compared with ERβ. Moreover, vascular endothelial growth factor was significantly downregulated on ERαKO EPCs compared with WT EPCs both in vitro and in vivo.Conclusions—Both ERα and ERβ contribute to E2-mediated EPC activation and tissue incorporation and to preservation of cardiac function after myocardial infarction. ERα plays a more prominent role in this process. Moreover, ERα contributes to upregulation of vascular endothelial growth factor, revealing possible mechanisms of an effect of E2on EPC biology. Finally, these data provide additional evidence of the importance of bone marrow–derived EPC phenotype in ischemic tissue repair.

Inflammation plays an essential role in vascular injury and repair. Mononuclear phagocytes are important contributors in these processes, in part, via adhesive interactions and secretion of proinflammatory cytokines. The antiinflammatory cytokine interleukin (IL)-10 suppresses such responses via deactivation of monocytes/macrophages and repression of inflammatory cytokine expression. The mechanisms of IL-10's suppressive action are, however, incompletely characterized. Here, we report that systemic IL-10 treatment after carotid artery denudation in mice blunts inflammatory cell infiltration and arterial tumor necrosis factor (TNF) expression. At the molecular level, in a human monocytic cell line, U937 IL-10 suppressed LPS-induced mRNA expression of a number of inflammatory cytokines, mainly via posttranscriptional mRNA destabilization. Detailed studies on IL-10 regulation of TNF-alpha mRNA expression identified AU-rich elements (ARE) in the 3' untranslated region as a necessary determinant of IL-10-mediated TNF-alpha mRNA destabilization. IL-10 sensitivity to TNF depends on the ability of IL-10 to inhibit the expression and mRNA-stabilizing protein HuR and via IL-10 mediated repression of p38 mitogen-activated protein (MAP) kinase activation. Because IL-10 function and signaling are important components for control of inflammatory responses, these results may provide insights necessary to develop strategies for modulating vascular repair and other accelerated arteriopathies, including transplant vasculopathy and vein graft hyperplasia.

The transcription factor E2F1 is known to regulate cell proliferation and has been thought to modulate tumorigenesis via this mechanism alone. Here we show that mice deficient in E2F1 exhibit enhanced angiogenesis. The proangiogenic phenotype in E2F1 deficiency is the result of overproduction of vascular endothelial growth factor (VEGF) and is prevented by VEGF blockade. Under hypoxic conditions, E2F1 down-regulates the expression of VEGF promoter activity by associating with p53 and specifically down-regulating expression of VEGF but not other hypoxia-inducible genes, suggesting a promoter structure context-dependent regulation mechanism. We found that the minimum VEGF promoter mediating transcriptional repression by E2F1 features an E2F1- binding site with four Sp-1 sites in close proximity. These data disclose an unexpected function of endogenous E2F1: regulation of angiogenic activity via p53-dependent transcriptional control of VEGF expression.