Role of Circulating Vascular Progenitors in Angiogenesis, Vascular Healing, and Pulmonary Hypertension

Potentially active compounds that improve PAD through angiogenesis: A review

Peripheral arterial disease (PAD) has been historically neglected, which has resulted in a lack of effective drugs in clinical practice. However, with the increasing prevalence of diseases like atherosclerosis and diabetes, the incidence of PAD is rising and cannot be ignored. Researchers are exploring the potential of promoting angiogenesis through exogenous compounds to improve PAD. This paper focuses on the therapeutic effect of natural products (Salidroside, Astragaloside IV, etc.) and synthetic compounds (Cilostazol, Dapagliflozin, etc.). Specifically, it examines how they can promote autocrine secretion of vascular endothelial cells, enhance cell paracrine interactions, and regulate endothelial progenitor cell function. The activation of these effects may be closely related to PI3K, AMPK, and other pathways. Overall, these exogenous compounds have promising therapeutic potential for PAD. This study aims to summarize the potential active compounds, provide a variety of options for the search for drugs for the treatment of PAD, and bring light to the treatment of patients.

Angiogenic Actions of Paeoniflorin on Endothelial Progenitor Cells and in Ischemic Stroke Rat Model

Ischemic stroke is one of the major diseases with high morbidity, mortality, and disability rate all over the world. Chinese herb-derived active components would provide valuable candidate compounds for ischemic stroke therapy. Paeoniflorin (PF) is an active ingredient from Paeoniae Radix which possesses neurovascular effect after ischemia. However, so far, few studies are reported on the efficacy and mechanism of PF from angiogenesis aspects. Results from our in vitro studies showed that the ability for proliferation, migration, and tube formation in bone marrow-derived endothelial progenitor cells (BM-EPCs) was promoted by coculturing with PF (100 [Formula: see text]M). Furthermore, to investigate the angiogenic effects of PF in vivo, we constructed an ischemic stroke model in rats and found that PF could reduce cerebral infarction, alleviate pathological injury, and increase the secretion of pro-angiogenic factors and cerebral vascular density after intraperitonially administration of 40 mg ⋅ kg[Formula: see text] ⋅ day[Formula: see text] for 14 days. Up-regulating the expression of VEGF/VEGF-R₂ might be the mechanism of PF's angiogenic action. In conclusion, the present study provides evidence that PF is an active monomer of Traditional Chinese Medicine which shows angiogenic actions on endothelial progenitor cells and in ischemic stroke rat model.

ITE promotes hypoxia-induced transdifferentiation of human pulmonary arterial endothelial cells possibly by activating transforming growth factor-β/Smads and MAPK/ERK pathways

This study aimed to investigate the transdifferentiation of human pulmonary arterial endothelial cells (HPAECs) into smooth muscle like (SM-like) cells under hypoxic conditions and reveal the role of endogenous small molecular compound 2-(1'H-indole-3'-carbonyl)-thiazole-4-carboxylicacid methyl ester (ITE) in this process. HPAECs were treated by hypoxia and hypoxia + ITE with different durations. The endothelial markers (CD31 and VE-cad) and smooth muscle markers (α-SMA, SM22α, and OPN) were investigated by immunofluorescence double staining, and their expressions, along with the differentiation regulators transforming growth factor-β (TGF-β) ligands and downstream signals including TGF-β1, bone morphogenetic protein (BMP2), BMP9, Samd2/3, ERK, and p38 MAPK, were determined by Western blot analysis. The viability and proliferation of HPAECs were detected by Cell Counting Kit-8 (CCK-8) method and bromodeoxyuridine (BrdU) assays. As a result, hypoxia induced HPAECs transdifferentiation from paving-stone-like into polygonal or spindle cells, whose number increased greatly after additional ITE stimulation for 7 days. Compared with the normoxic HPAECs, the expression of endothelial markers reduced and smooth muscle markers were enhanced with the extension of hypoxia + ITE treatment, and meanwhile the cell viability increased significantly. Hypoxia could promote expression of TGF-β1 protein rather than BMP2 and BMP9, and regulate phosphorylation levels of Samd2/3, ERK and p38 MAPK in different manners. In conclusion, ITE can promote the hypoxia-induced transdifferentiation of HPAECs into SM-like cells via TGF-β/Smads and MAPK/ERK pathways.

Carnosine Supplementation Enhances Post Ischemic Hind Limb Revascularization

High (millimolar) concentrations of the histidine containing dipeptide - carnosine (β-alanine-L-histidine) are present in the skeletal muscle. The dipeptide has been shown to buffer intracellular pH, chelate transition metals, and scavenge lipid peroxidation products; however, its role in protecting against tissue injury remains unclear. In this study, we tested the hypothesis that carnosine protects against post ischemia by augmenting HIF-1α angiogenic signaling by Fe2+ chelation. We found that wild type (WT) C57BL/6 mice, subjected to hind limb ischemia (HLI) and supplemented with carnosine (1g/L) in drinking water, had improved blood flow recovery and limb function, enhanced revascularization and regeneration of myocytes compared with HLI mice placed on water alone. Carnosine supplementation enhanced the bioavailability of carnosine in the ischemic limb, which was accompanied by increased expression of proton-coupled oligopeptide transporters. Consistent with our hypothesis, carnosine supplementation augmented HIF-1α and VEGF expression in the ischemic limb and the mobilization of proangiogenic Flk-1+/Sca-1+ cells into circulation. Pretreatment of murine myoblast (C2C12) cells with octyl-D-carnosine or carnosine enhanced HIF-1α protein expression, VEGF mRNA levels and VEGF release under hypoxic conditions. Similarly pretreatment of WT C57/Bl6 mice with carnosine showed enhanced blood flow in the ischemic limb following HLI surgery. In contrast, pretreatment of hypoxic C2C12 cells with methylcarcinine, a carnosine analog, lacking Fe2+ chelating capacity, had no effect on HIF-1α levels and VEGF release. Collectively, these data suggest that carnosine promotes post ischemic revascularization via augmentation of pro-angiogenic HIF-1α/VEGF signaling, possibly by Fe2+ chelation.

Ex vivo expansion of cord blood-derived endothelial cells using a novel xeno-free culture media

Aim

Endothelial cells (ECs), isolated from peripheral blood (PB), bone marrow (BM) and cord blood (CB), are limited in numbers and expansion has had limited success. We used a novel serum-free medium (EndoGo) to evaluate effects on ex vivo expansion of CB-derived ECs.

Materials & methods

Flow cytometry and matrigel were used to determine expansion of ECs and for determination of the EC progenitor cell.

Results

EndoGo™-containing cultures demonstrated superior expansion and stimulated proliferation of two distinct subpopulations, CD34⁺CD31⁺ and CD34^-CD31⁺, which exhibited different morphology, phenotype and function. EndoGo also expanded the CB endothelial progenitor cells from freshly isolated CB.

Conclusion

These findings demonstrate the potential of EndoGo to expand CB ECs, which could generate increased numbers of ECs for therapeutic applications.

Circulating Pro-Vascular Progenitor Cell Depletion During Type 2 Diabetes: Translational Insights Into the Prevention of Ischemic Complications in Diabetes

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This study combined ALDH activity with cell surface marker expression to develop a multiparametric flow cytometry assay to assess proangiogenic progenitor and proinflammatory cell content in the peripheral blood of patients with T2D compared with age-matched control subjects.

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Patients with T2D exhibited an increased frequency of proinflammatory ALDH^hi cells with granulocyte side scatter properties and a decreased frequency of circulating monocytes with an M2 phenotype that is associated with proangiogenic and anti-inflammatory functions.

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Patients with T2D exhibited significant depletion of circulating provascular ALDH^hiCD34+ progenitor cells with primitive, migratory, endothelial, and pericyte phenotypes.

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Subgroup analyses that stratified patients with T2D according to age, duration of T2D, insulin requirement, and glycosylated hemoglobin levels revealed that only the duration of T2D correlated with vascular progenitor cell depletion.

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Flow cytometric assessment of circulating ALDH^hi cell subsets represents a promising translational approach for identifying patients with T2D at increased risk for cardiovascular comorbidities.

Detection of vascular regenerative cell exhaustion is required to combat ischemic complications during type 2 diabetes mellitus (T2D). We used high aldehyde dehydrogenase (ALDH) activity and surface marker co-expression to develop a high-throughput flow cytometry–based assay to quantify circulating proangiogenic and proinflammatory cell content in the peripheral blood of individuals with T2D. Circulating proangiogenic monocytes expressing anti-inflammatory M2 markers were decreased in patients with T2D. Individuals with longer duration of T2D exhibited reduced frequencies of circulating proangiogenic ALDH^hiCD34+ progenitor cells with primitive (CD133) and migratory (CXCR4) phenotypes. This approach consistently detected increased inflammatory cell burden and decreased provascular progenitor content in individuals with T2D.

Myeloid-Derived Suppressor Cells and Pulmonary Hypertension

Myeloid–derived suppressor cells (MDSCs) comprised a heterogeneous subset of bone marrow–derived myeloid cells, best studied in cancer research, that are increasingly implicated in the pathogenesis of pulmonary vascular remodeling and the development of pulmonary hypertension. Stem cell transplantation represents one extreme interventional strategy for ablating the myeloid compartment but poses a number of translational challenges. There remains an outstanding need for additional therapeutic targets to impact MDSC function, including the potential to alter interactions with innate and adaptive immune subsets, or alternatively, alter trafficking receptors, metabolic pathways, and transcription factor signaling with readily available and safe drugs. In this review, we summarize the current literature on the role of myeloid cells in the development of pulmonary hypertension, first in pulmonary circulation changes associated with myelodysplastic syndromes, and then by examining intrinsic myeloid cell changes that contribute to disease progression in pulmonary hypertension. We then outline several tractable targets and pathways relevant to pulmonary hypertension via MDSC regulation. Identifying these MDSC-regulated effectors is part of an ongoing effort to impact the field of pulmonary hypertension research through identification of myeloid compartment-specific therapeutic applications in the treatment of pulmonary vasculopathies.

The evaluation of circulating endothelial progenitor cells and related angiogenic markers as prognostic factors in soft-tissue tumors

INTRODUCTION

Neovascularisation is a critical step in the progression of malignant tumors. Circulating endothelial progenitor cells (cEPC) have been proposed as surrogate markers of vasculogenesis in malignancies. In this project, we studied the impact of tumor-specific therapy on cEPC and associated angiogenic factors in patients with soft tissue tumors.

MATERIALS AND METHODS

Fifty-three patients with soft tissue tumors (25 soft tissue sarcomas, 19 GIST, 9 desmoids) and 15 healthy controls were included. Blood samples were obtained at two time points, before and 8 weeks after start of tumor-specific therapy. Peripheral blood mononuclear cells (PBMCs) were isolated. cEPCs were characterised as CD34⁺, CD133⁺, CD45^dim, CD31⁺ and vascular endothelial growth factor 2 (VEGFR-2) positive cells. Serum concentrations of VEGF-A and angiopoetin-2 were determined by enzyme-linked immunosorbent assay.

RESULTS

VEGF-A and Ang-2 concentrations were significantly higher in tumor patients than in healthy controls in both samples (p < .01). Sarcoma patients with progressive disease developed a significant increase in cEPC levels between the two blood samples compared to those with stable disease (p = .002). GIST patients with progressive tumor or metastatic disease showed significant increase in VEGF-A values (p = .01).

DISCUSSION

The pre-treatment values of the angiogenic markers did not correlate with the clinical course of the disease. However, cEPCs levels were significantly higher in sarcoma patients with progressive disease compared to those with stable disease and should be further evaluated as early markers of disease progression in sarcoma patients. VEGF-A and angiopoetin-2 clearly play a role as mediators of the vasculogenesis contributing to tumor progression.

Enrichment of Scleroderma Vascular Disease-Associated Autoantigens in Endothelial Lineage Cells

OBJECTIVE

Scleroderma patients with autoantibodies to CENPs and/or interferon-inducible protein 16 (IFI-16) are at increased risk of severe vascular complications. This study was undertaken to determine whether these autoantigens are enriched in cells of the vasculature.

METHODS

Successive stages of embryoid bodies (EBs) as well as vascular progenitors were used to evaluate the expression of scleroderma autoantigens IFI-16 and CENP by immunoblotting. CD31 was included to mark early blood vessels. IFI-16 and CD31 expression were defined in paraffin-embedded skin sections from scleroderma patients and from healthy controls. IFI-16 expression was determined by flow cytometric analysis in circulating endothelial cells (CECs) and circulating hematopoietic progenitor cells.

RESULTS

Expression of CENP-A, IFI-16, and CD31 was enriched in EBs on days 10 and 12 of differentiation, and particularly in cultures enriched in vascular progenitors (IFI-16, CD31, and CENPs A and B). This pattern was distinct from that of comparator autoantigens. Immunohistochemical staining of paraffin-embedded skin sections showed enrichment of IFI-16 in CD31-positive vascular endothelial cells in biopsy specimens from scleroderma patients and normal controls. Flow cytometric analysis revealed IFI-16 expression in circulating hematopoietic progenitor cells but minimal expression in CECs.

CONCLUSION

Our findings indicate that expression of the scleroderma autoantigens IFI-16 and CENPs, which are associated with severe vascular disease, is increased in vascular progenitors and mature endothelial cells. High level, lineage-enriched expression of autoantigens may explain the striking association between clinical phenotypes and the immune targeting of specific autoantigens.

[Pulmonary arterial hypertension, bone marrow, endothelial cell precursors and serotonin]

Serotonin and bone-marrow-derived stem cells participate together in triggering pulmonary hypertension. Our work has shown that the absence of 5-HT2B receptors generates permanent changes in the composition of the blood and bone-marrow in the myeloid lineages, particularly in endothelial cell progenitors. The initial functions of 5-HT2B receptors in pulmonary arterial hypertension (PAH) are restricted to bone-marrow cells. They contribute to the differentiation/proliferation/mobilization of endothelial progenitor cells from the bone-marrow. Those bone-marrow-derived cells have a critical role in the development of pulmonary hypertension and pulmonary vascular remodeling. These data indicate that bone-marrow derived endothelial progenitors play a key role in the pathogenesis of PAH and suggest that interactions involving serotonin and bone morphogenic protein type 2 receptor (BMPR2) could take place at the level of the bone-marrow.

Infusion of endothelial progenitor cells ameliorates liver injury in mice after haematopoietic stem cell transplantation

BACKGROUND & AIMS

Injury to liver sinusoidal endothelial cells (LSECs) is thought to be the initial factor for Hepatic veno-occlusive disease, a severe complication after haematopoietic stem cell transplantation (HSCT). Endothelial progenitor cells (EPCs) have the capacity to differentiate into endothelial cells and play a critical role in vasculogenesis, tissue regeneration and repair. Whether EPCs infusion ameliorates LSECs injury remains unclear. The aim of this study was to evaluate the effects of EPCs on liver injury in mice after HSCT.

METHODS

Mice received HSCT without or with EPCs infusion (HSCT + EPCs). Untreated mice were used as control. Liver and whole blood were collected post HSCT and used for the analysis of pathology of liver sinusoidal endothelial cells (LSECs) and hepatocytes, liver ultrastructure, function, level of IL-6, TNF-α and platelet activation.

RESULTS

Severe LSECs injury, hepatocyte damage, abnormal liver function was observed in HSCT group. In addition, increased P-selectin expression and secretion of IL-6, TNF-α was also found. However, all the above changes were alleviated in HSCT + EPCs at all the time points and normalized at the endpoint. Meanwhile, EPCs-induced repair of LSECs and hepatocytes was totally inhibited by the addition of anti-VE-cadherin antibody.

CONCLUSIONS

EPCs infusion ameliorated the damage to LSECs and hepatocytes as well as reduced secretion of IL-6, TNF-α and inhibited platelet activation after HSCT, leading to improved liver function, suggesting EPCs might be a new therapeutic strategy in the prophylaxis of liver injury after HSCT.

Heart valve tissue engineering: how far is the bedside from the bench?

Heart disease, including valve pathologies, is the leading cause of death worldwide. Despite the progress made thanks to improving transplantation techniques, a perfect valve substitute has not yet been developed: once a diseased valve is replaced with current technologies, the newly implanted valve still needs to be changed some time in the future. This situation is particularly dramatic in the case of children and young adults, because of the necessity of valve growth during the patient's life. Our review focuses on the current status of heart valve (HV) therapy and the challenges that must be solved in the development of new approaches based on tissue engineering. Scientists and physicians have proposed tissue-engineered heart valves (TEHVs) as the most promising solution for HV replacement, especially given that they can help to avoid thrombosis, structural deterioration and xenoinfections. Lastly, TEHVs might also serve as a model for studying human valve development and pathologies.

Increasing HDL levels by inhibiting cholesteryl ester transfer protein activity in rabbits with hindlimb ischemia is associated with increased angiogenesis

BACKGROUND

High density lipoprotein (HDL) infusions increase new blood vessel formation (angiogenesis) in rodents with ischemic injury. This study asks if increasing HDL levels by inhibiting cholesteryl ester transfer protein (CETP) activity increases angiogenesis in New Zealand White (NZW) rabbits with hindlimb ischemia.

METHODS AND RESULTS

NZW rabbits were maintained for 6weeks on chow or chow supplemented with 0.07% or 0.14% (wt/wt) of the CETP inhibitor, des-fluoro-anacetrapib. The left femoral artery was ligated after 2weeks of des-fluoro-anacetrapib treatment. The animals were sacrificed 4weeks after femoral artery ligation. Treatment with 0.07% and 0.14% (wt/wt) des-fluoro-anacetrapib reduced CETP activity by 63±12% and 81±8.6%, increased plasma apoA-I levels by 1.3±0.1- and 1.4±0.1-fold, and increased plasma HDL-cholesterol levels by 1.4±0.1- and 1.7±0.2-fold, respectively. Treatment with 0.07% and 0.14% (wt/wt) des-fluoro-anacetrapib increased the number of collateral arteries by 60±16% and 84±27%, and arteriole wall area in the ischemic hindlimbs by 84±16% and 94±13%, respectively. Capillary density in the ischemic hindlimb adductor muscle increased from 1.1±0.2 (control) to 2.1±0.3 and 2.2±0.4 in the 0.07% and 0.14% (wt/wt) des-fluoro-anacetrapib-treated animals, respectively. Incubation of HDLs from des-fluoro-anacetrapib-treated animals with human coronary artery endothelial cells at apoA-I concentrations comparable with their plasma levels increased tubule network formation. These effects were abolished by knockdown of scavenger receptor-B1 (SR-B1) and PDZK1, and pharmacological inhibition of PI3K/Akt.

CONCLUSION

Increasing HDL levels by inhibiting CETP activity is associated with increased collateral blood vessel formation in NZW rabbits with hindlimb ischemia in an SR-B1- and PI3K/Akt-dependent manner.

Oxidized high-density lipoprotein impairs endothelial progenitor cells' function by activation of CD36-MAPK-TSP-1 pathways

AIMS

High-density lipoprotein (HDL) levels inversely correlate with cardiovascular events due to the protective effects on vascular wall and stem cells, which are susceptible to oxidative modifications and then lead to potential pro-atherosclerotic effects. We proposed that oxidized HDL (ox-HDL) might lead to endothelial progenitor cells (EPCs) dysfunction and investigated underlying mechanisms.

RESULTS

ox-HDL was shown to increase apoptosis and intracellular reactive oxygen species levels, but to reduce migration, angiogenesis, and cholesterol efflux of EPCs in a dose-dependent manner. p38 mitogen-activated protein kinase (MAPK) and NF-κB were activated after ox-HDL stimulation, which also upregulated thrombospondin-1 (TSP-1) expression without affecting vascular endothelial growth factor. Effects caused by ox-HDL could be significantly attenuated by pretreatment with short hairpin RNA-mediated CD36 knockdown or probucol. Data of in vivo experiments and the inverse correlation of ox-HDL and circulating EPC numbers among patients with coronary artery diseases (CAD) or CAD and type 2 diabetes also supported it. Meanwhile, HDL separated from such patients could significantly increase cultured EPC's caspase 3 activity, further supporting our proposal.

INNOVATION

This is the most complete study to date of how ox-HDL would impair EPCs function, which was involved with activation of CD36-p38 MAPK-TSP-1 pathways and proved by not only the inverse relationship between ox-HDL and circulating EPCs in clinic but also pro-apoptotic effects of HDL separated from patients' serum.

CONCLUSION

Activation of CD36-p38 MAPK-TSP-1 pathways contributes to the pathological effects of ox-HDL on EPCs' dysfunction, which might be one of the potential etiological factors responsible for the disturbed neovascularization in chronic ischemic disease.

N-Acetylcysteine Ameliorates Experimental Autoimmune Myocarditis in Rats via Nitric Oxide

BACKGROUND

Oxidative stress may play an important role in the development of myocarditis. We investigated the effects of N-acetylcysteine (NAC), a potent antioxidant, on experimental autoimmune myocarditis (EAM) in rats.

METHODS AND RESULTS

A rat model of porcine myosin-induced EAM was used. After the immunization with myosin, NAC (20 mg/kg/d) or saline was injected intraperitoneally on days 1 to 21. Additional myosin-immunized rats treated with NAC were orally given 25 mg/kg/d of N(G)-nitro-l-arginine methylester (l-NAME), an inhibitor of nitric oxide (NO) synthase, and N(G)-nitro-d-arginine methylester (d-NAME), an inactive enantiomer. The NAC treatment improved cardiac pathology associated with reduced superoxide production. In the EAM rats treated with NAC associated with oral l-NAME, but not with oral d-NAME, the severity of myocarditis was not reduced. Expression of intercellular adhesion molecule 1 was reduced by NAC treatment. Myocardial c-kit(+) cells were demonstrated only in the NAC-treated group. Hemodynamic study showed that the increased left ventricular mass produced by myocardial inflammation tended to be reduced by NAC treatment.

CONCLUSION

Treatment with NAC ameliorated myocardial injury via NO system in a rat model of myocarditis.

PDGFRβ triggered by bFGF promotes the proliferation and migration of endothelial progenitor cells via p-ERK signalling

We have examined the effects of bFGF (basic fibroblast growth factor) on p-ERK (phosphorylated extracellular signal-regulated kinase) through PDGFRβ (platelet-derived growth factor receptor β) in the proliferation and migration of EPCs (endothelial progenitor cells). EPC migration was detected using the Transwell system. The expression of PDGFRβ mRNA and protein, total ERK and p-ERK proteins was respectively assessed by real-time PCR and Western blottings. bFGF promote the proliferation and migration of EPCs, the effects of bFGF being implemented by activating ERK signalling through the expression of PDGFRβ, whereas an anti-bFGF antibody and inhibitor of PDGF (platelet-derived growth factor) receptor kinase (AG1296) could respectively decrease the expression of PDGFRβ mRNA and protein and p-ERK protein. Total ERK protein did not change under the same experimental conditions, and an inhibitor of p-ERK (PD98059) inhibited the proliferation and migration of EPCs. The findings strongly suggest that a PDGFRβ/p-ERK signalling pathway triggered by bFGF plays an important role in the proliferation and migration of EPCs.

Zoledronate attenuates angiogenic effects of angiotensin II-stimulated endothelial progenitor cells via RhoA and MAPK signaling

BACKGROUND

New vessel formation plays a pivotal role in the pathogenesis of neovascular-related diseases. Endothelial progenitor cells (EPCs) were found to contribute to neovascular-related diseases and interference with EPC neovascularization may be a novel target for these diseases. Zoledronate (Zol) was reported to exhibit anti-angiogenic effect. Basing on these evidences, we proposed that Zol may affect EPC function to exert novel anti-angiogenic effect. In this study, we therefore investigated the effects of Zol on multiple aspects of EPC function and explored the underlying mechanisms involved.

METHODOLOGY/PRINCIPAL FINDINGS

EPCs were cultured from bone marrow derived mononuclear cells. The potential effects of Zol on Angiotensin II (Ang II)-stimulated EPC proliferation, migration, adhesion, in vitro tube formation were investigated. The results showed that Ang II (1 µM) enhanced EPC migration, adhesion, in vitro tube formation but had no effect on cell proliferation. Zol (75 and 100 µM) inhibited proliferation of EPCs and 50 µM geranylgeranyol (GGOH) could reverse the decrease of EPC proliferation. We found for the first time that Zol (50-100 µM) dose dependently attenuated migration, adhesion, and in vitro tube formation of EPCs stimulated by Ang II. GGOH could reverse the attenuation of EPC function induced by Zol. However, Zol did not induce EPC apoptosis. In addition, the underlying mechanisms were determined. The results revealed that Zol markedly down-regulated active RhoA stimulated by Ang II and inhibited the phosphorylation of Erk1/2 and JNK. Moreover, RhoA silencing resulted in a notable inhibition of EPC in vitro tube formation, suggesting that RhoA suppression played a pivotal role in Zol antiangiogenic effect.

CONCLUSIONS/SIGNIFICANCE

These findings suggested that Zol attenuated the promotion of EPC function stimulated by Ang II and exhibited novel antiangiogenic effect via RhoA and MAPK signaling. Thus, Zol may be served as a novel therapeutic agent for neovascular-related diseases treatment.

Understanding vascular development

The vasculature of an organism has the daunting task of connecting all the organ systems to nourish tissue and sustain life. This complex network of vessels and associated cells must maintain blood flow, but constantly adapt to acute and chronic changes within tissues. While the vasculature has been studied for over a century, we are just beginning to understand the processes that regulate its formation and how genetic hierarchies are influenced by mechanical and metabolic cues to refine vessel structure and optimize efficiency. As we gain insights into the developmental mechanisms, it is clear that the processes that regulate blood vessel development can also enable the adult to adapt to changes in tissues that can be elicited by exercise, aging, injury, or pathology. Thus, research in vessel development has provided tremendous insights into therapies for vascular diseases and disorders, cancer interventions, wound repair and tissue engineering, and in turn, these models have clearly impacted our understanding of development. Here we provide an overview of the development of the vascular system, highlighting several areas of active investigation and key questions that remain to be answered.

Differential effects of fondaparinux and bemiparin on angiogenic and vasculogenesis-like processes

INTRODUCTION

Conventional therapy for venous thromboembolism or acute coronary syndrome involves the administration of glycoanticoagulants (heparins) or oligosaccharides (fondaparinux). We evaluated the effects of such drugs on angiogenesis and vasculogenesis-like models.

MATERIALS AND METHODS

Human umbilical vein endothelial cells or human endothelial progenitor cells were treated with bemiparin, fondaparinux or unfractionated heparin, at concentrations reflecting the doses used in clinical practice. After 24h, cell viability, proliferation, tubule formation and angiogenic molecular mechanisms, such as activation of the serine/threonine kinase AKT, were assessed. In vivo angiogenesis was studied using a Matrigel sponge assay in mice.

RESULTS

Bemiparin gave a significant decrease of in vitro angiogenesis as shown by the reduction of endothelial cell tubule network, while both fondaparinux and unfractionated heparin did not show any significant effect. In assays of Matrigel sponge invasion in mice, unfractionated heparin was able to stimulate angiogenesis and, conversely, bemiparin inhibited angiogenesis. Furthermore, both bemiparin and fondaparinux caused a significant reduction in an in vitro vasculogenesis-like model, as demonstrated by the decrease of tubule network after co-seeding of endothelial progenitor cells and human umbilical vein endothelial cells. In addition, unfractionated heparin but not bemiparin was able to increase AKT phosphorylation.

CONCLUSIONS

In in vitro experiments, bemiparin was the only drug to show an anti-angiogenic and vasculogenic-like effect, unfractionated heparin showed only a trend to increase in angiogenesis assay and fondaparinux affected only the vasculogenesis-like model. Notably, the in vivo experiments corroborated these data. Such results are important for the choice of a patient-tailored therapy.

Therapeutical potential of autologous peripheral blood mononuclear cell transplantation in patients with type 2 diabetic critical limb ischemia

AIM

The aim was to evaluate the therapeutic effectiveness of granulocyte colony-stimulating factor (G-CSF) mobilized peripheral blood mononuclear cells (PBMNCs) in critical limb ischemia (CLI) of type 2 diabetic patients.

METHOD

Forty diabetic patients with CLI were enrolled and randomized to treatment and control groups. In the treatment group, the patients received subcutaneous injections of recombinant human G-CSF (30 MU/day) for 5 days to mobilize stem cells. PBMNCs were collected and transplanted by multiple intramuscular injections of 1 ml in 1-1.5-cm depth into ischemic limbs.

RESULTS

At the end of 12 weeks of follow-up, the baseline and end point results in transplant group were as follows: Fontaine score improved from 3.8±03 to 3±0.5 (P=.0001), ankle brachial pressure index increased from 0.68±0.24 to 0.87±024 (P=.001), transcutaneous oxygen increased from 33±14 mmHg to 44±10 mmHg (P=.0001), and 6-min walking distance improved from 280±82 m to 338±98 m (P=.0001). Pain score decreased from 8.2±1.3 to 5.63±1.6 (P=.001), and the number of patients with limb ulcers was reduced from 9/20 (45%) to 3/20 (15%) (P=.031). In the control group, Fontaine score, 6-min walking distance, and pain score were improved; ankle brachial pressure index and transcutaneous oxygen pressure were not improved. The number of patients with limb ulcers did not change in the control group. There are improvement in amputation rates, collateral vessel development, and number of limb ulcers healed.

CONCLUSIONS

These results indicate that the autologous transplantation of G-CSF that mobilized PBMNCs in CLI diabetic patients is safe and effective in patient compliant reduction and improved perfusion.

Serotonin 5-HT2B receptors are required for bone-marrow contribution to pulmonary arterial hypertension

Pulmonary arterial hypertension (PAH) is a progressive disease characterized by lung endothelial dysfunction and vascular remodeling. Recently, bone marrow progenitor cells have been localized to PAH lungs, raising the question of their role in disease progression. Independently, serotonin (5-HT) and its receptors have been identified as contributors to the PAH pathogenesis. We hypothesized that 1 of these receptors, 5-HT(2B), is involved in bone marrow stem cell mobilization that participates in the development of PAH and pulmonary vascular remodeling. A first study revealed expression of 5-HT(2B) receptors by circulating c-kit(+) precursor cells, whereas mice lacking 5-HT(2B) receptors showed alterations in platelets and monocyte-macrophage numbers, and in myeloid lineages of bone marrow. Strikingly, mice with restricted expression of 5-HT(2B) receptors in bone marrow cells developed hypoxia or monocrotaline-induced increase in pulmonary pressure and vascular remodeling, whereas restricted elimination of 5-HT(2B) receptors on bone marrow cells confers a complete resistance. Moreover, ex vivo culture of human CD34(+) or mice c-kit(+) progenitor cells in the presence of a 5-HT(2B) receptor antagonist resulted in altered myeloid differentiation potential. Thus, we demonstrate that activation of 5-HT(2B) receptors on bone marrow lineage progenitors is critical for the development of PAH.

Tricuspid regurgitant velocity elevation in a three-year old child with sickle cell anemia and recurrent acute chest syndromes reversed not by hydroxyurea but by bone marrow transplantation

Elevated Tricuspid Regurgitant Velocity (TRV) has been related to higher mortality in adults and to hemolysis, lower oxygen saturation during 6-minute walk test and acute chest syndrome (ACS) in children with sickle cell disease (SCD). Hydroxyurea (HU) has reduced TRV value in children and adults. We describe a three year old HbSS child with recurrent ACS, hypoperfusion of the left lung, mild hemolysis and persistent TRV elevation. TRV did not normalize after HU, despite improvement in clinical conditions and in baseline laboratory parameters related to hemolysis and blood viscosity, but normalized after bone marrow transplantation (BMT). Our experience suggests that in young patients, TRV reduction can be a positive concomitant effect of BMT.

Ion channels and transporters in cancer. 6. Vascularizing the tumor: TRP channels as molecular targets

Tumor vascularization is a critical process that determines tumor growth and metastasis. In the last decade new experimental evidence obtained from in vitro and in vivo studies have challenged the classical angiogenesis model forcing us to consider new scenarios for tumor neovascularization. In particular, the genetic stability of tumor-derived endothelial cells (TECs) has been recently questioned in several studies, which show that TECs, as well as pericytes, differ significantly from their normal counterparts at genetic and functional levels. In addition to such an epigenetic action of tumor microenvironment on endothelial cells (ECs) commitment, the distinct characteristics of TECs could be due to differences in their origin compared with preexisting differentiated ECs. Intracellular Ca(2+) signals are involved at different critical phases in the regulation of the complex process of angiogenesis and tumor progression. These signals are generated by a wide variety of intrinsic and extrinsic factors. Several key components of Ca(2+) signaling including Ca(2+) channels in the plasma membrane, endoplasmic reticulum, calcium pumps, and mitochondria contribute to the generation, amplitude, and frequency of these Ca(2+) change. In particular, several members of the transient receptor potential (TRP) family of calcium-permeable channels have profound effects on the function of ECs. Because of its multifaceted role in the control of cell function, proliferation, and motility, TRP channels have been suggested as a potential molecular target for control of tumor neovascularization. Since plasma membrane Ca(2+) channels are easily and directly accessible via the bloodstream, they are potential targets for a number of pharmacological and antibody-targeted therapeutic strategies, with specificity being the main limitation. In this review we discuss recent advances in understanding the role of Ca(2+) channels, with specific reference to TRP channels, in tumor vascularization process.

The impact of bioactive lipids on cardiovascular development

Lysophospholipids comprise a group of bioactive molecules with multiple biological functions. The cardinal members of this signalling molecule group are sphingosylphosphorylcholine (SPC), lysophosphatidic acid (LPA), and sphingosine 1-phosphate (S1P) which are, at least in part, homologous to each other. Bioactive lipids usually act via G-protein coupled receptors (GPCRs), but can also function as direct intracellular messengers. Recently, it became evident that bioactive lipids play a role during cellular differentiation development. SPC induces mesodermal differentiation of mouse ES cells and differentiation of promyelocytic leukemia cells, by a mechanism being critically dependent on MEK-ERK signalling. LPA stimulates the clonal expansion of neurospheres from neural stem/progenitor cells and induces c-fos via activation of mitogen- and stress-activated protein kinase 1 (MSK1) in ES cells. S1P acts on hematopoietic progenitor cells as a chemotactic factor and has also been found to be critical for cardiac and skeletal muscle regeneration. Furthermore, S1P promotes cardiogenesis and similarly activates Erk signalling in mouse ES cells. Interestingly, S1P may also act to maintain human stem cell pluripotency. Both LPA and S1P positively regulate the proliferative capacity of murine ES cells. In this paper we will focus on the differential and developmental impact of lysophospholipids on cardiovascular development.

Musashi-1 expression in atherosclerotic arteries and its relevance to the origin of arterial smooth muscle cells: histopathological findings and speculations

The origin of smooth muscle cells in developing atherosclerotic lesions is a controversial topic with accumulating evidence indicating that at least some arterial smooth muscle cells might originate from bone marrow-derived smooth muscle cell precursors circulating in the blood. The stem cell markers currently used for the identification of stem cells in the arterial intima can be expressed by a number of different cell types residing in the arterial wall, such as mast cells, endothelial cells and dendritic cells, which can make interpretation of the data obtained somewhat ambiguous. In the present study we examined whether the putative intestinal stem cell marker Musashi-1 is expressed in the arterial wall. Using a multiplexed tandem polymerase chain reaction method (MT-PCR) and immunohistochemistry, Musashi-1 expression was revealed in human coronary arterial wall tissue segments, and this finding was followed by the demonstration of significantly higher expression levels of Musashi-1 in atherosclerotic plaques compared with those in undiseased intimal sites. Double immunohistochemistry demonstrated that in the arterial wall Musashi-1 positive cells either did not display any specific markers of cells that are known to reside in the arterial intima or Musashi-1 was co-expressed by smooth muscle α-actin positive cells. Some Musashi-1 positive cells were found along the luminal surface of arteries as well as within microvessels formed in atherosclerotic plaques by neovascularization, which supports the possibility that Musashi-1 positive cells might intrude into the arterial wall from the blood and might even represent circulating smooth muscle cell precursors.

Is peroxisome proliferator-activated receptor gamma (PPARγ) a therapeutic target for the treatment of pulmonary hypertension?

Pulmonary hypertension (PH), a progressive disorder associated with significant morbidity and mortality, is caused by complex pathways that culminate in structural and functional alterations of the pulmonary circulation and increases in pulmonary vascular resistance and pressure. Diverse genetic, pathological, or environmental triggers stimulate PH pathogenesis culminating in vasoconstriction, cell proliferation, vascular remodeling, and thrombosis. We conducted a thorough literature review by performing MEDLINE searches via PubMed to identify articles pertaining to PPARγ as a therapeutic target for the treatment of PH. This review examines basic and preclinical studies that explore PPARγ and its ability to regulate PH pathogenesis. Despite the current therapies that target specific pathways in PH pathogenesis, including prostacyclin derivatives, endothelin-receptor antagonists, and phosphodiesterase type 5 inhibitors, morbidity and mortality related to PH remain unacceptably high, indicating the need for novel therapeutic approaches. Consequently, therapeutic targets that simultaneously regulate multiple pathways involved in PH pathogenesis have gained attention. This review focuses on peroxisome proliferator-activated receptor gamma (PPARγ), a member of the nuclear hormone receptor superfamily of ligand-activated transcription factors. While the PPARγ receptor is best known as a master regulator of lipid and glucose metabolism, a growing body of literature demonstrates that activation of PPARγ exerts antiproliferative, antithrombotic, and vasodilatory effects on the vasculature, suggesting its potential efficacy as a PH therapeutic target.

Pulmonary vascular disease related to hemodynamic stress in the pulmonary circulation

Hemodynamic stress in the pulmonary vessel is directly linked to the development of vascular remodeling and dysfunction, ultimately leading to pulmonary hypertension. Recently, some advances have been made in our molecular understanding of the exogenous upstream stimuli that initiate hemodynamic pertubations as well as the downstream vasoactive effectors that control these responses. However, much still remains unknown regarding how these complex signaling pathways connect in order to result in these characteristic pathophysiological changes. This chapter will describe our current understanding of and needed areas of research into the clinical, physiological, and molecular changes associated with pressure/volume overload in the pulmonary circulation.

Progenitor cells in pulmonary vascular remodeling

Pulmonary hypertension is characterized by cellular and structural changes in the walls of pulmonary arteries. Intimal thickening and fibrosis, medial hypertrophy and fibroproliferative changes in the adventitia are commonly observed, as is the extension of smooth muscle into the previously non-muscularized vessels. A majority of these changes are associated with the enhanced presence of α-SM-actin+ cells and inflammatory cells. Atypical abundances of functionally distinct endothelial cells, particularly in the intima (plexiform lesions), and also in the perivascular regions, are also described. At present, neither the origin(s) of these cells nor the molecular mechanisms responsible for their accumulation, in any of the three compartments of the vessel wall, have been fully elucidated. The possibility that they arise from either resident vascular progenitors or bone marrow-derived progenitor cells is now well established. Resident vascular progenitor cells have been demonstrated to exist within the vessel wall, and in response to certain stimuli, to expand and express myofibroblastic, endothelial or even hematopoietic markers. Bone marrow-derived or circulating progenitor cells have also been shown to be recruited to sites of vascular injury and to assume both endothelial and SM-like phenotypes. Here, we review the data supporting the contributory role of vascular progenitors (including endothelial progenitor cells, smooth muscle progenitor cells, pericytes, and fibrocytes) in vascular remodeling. A more complete understanding of the processes by which progenitor cells modulate pulmonary vascular remodeling will undoubtedly herald a renaissance of therapies extending beyond the control of vascular tonicity and reduction of pulmonary artery pressure.

PPARgamma as a potential therapeutic target in pulmonary hypertension

Pulmonary hypertension (PH) is a progressive disorder of the pulmonary circulation associated with significant morbidity and mortality. The pathobiology of PH involves a complex series of derangements causing endothelial dysfunction, vasoconstriction and abnormal proliferation of pulmonary vascular wall cells that lead to increases in pulmonary vascular resistance and pressure. Recent evidence indicates that the ligand-activated transcription factor, peroxisome proliferator-activated receptor gamma (PPARgamma) can have a favorable impact on a variety of pathways involved in the pathogenesis of PH. This review summarizes PPARgamma biology and the emerging evidence that therapies designed to activate this receptor may provide novel approaches to the treatment of PH. Mediators of PH that are regulated by PPARgamma are reviewed to provide insights into potential mechanisms underlying therapeutic effects of PPARgamma ligands in PH.

T-type ca(2+) channel blockers increase smooth muscle progenitor cells and endothelial progenitor cells in bone marrow stromal cells in culture by suppression of cell death

OBJECTIVE

To examine the expression patterns and roles of voltage-dependent Ca2+ channels in bone marrow stromal cells (BMSCs).

MATERIALS AND METHODS

Ca(2+) currents of BMSCs were measured by the whole-cell patch clamp method. The number and percentage of deaths of BMSCs cultured for 14 days with or without Ca(2+) channel blockers were evaluated using a MTT assay and an LDH assay, respectively.

RESULTS

T-type Ca(2+) channel current was recorded in 0, 2, 10, and 4% of BMSCs on days 3, 10, 17, and 24 in culture, respectively. L-type Ca(2+) channel current was first recorded on day 24 in 6% of BMSCs. Addition of the T-type Ca(2+) channel blocker mibefradil but not the L-type Ca(2+) channel blocker nifedipine significantly increased the cell count. Immunocytochemical analysis revealed increases in the counts of smooth muscle progenitor cells (SMPCs) and endothelial progenitor cells (EPCs). Mibefradil but not nifedipine significantly decreased the rate of cell death.

CONCLUSION

T-type Ca(2+) channel blockers increased the numbers of SMPCs and EPCs in cultured BMSCs, partly through suppression of cell death. Thus, T-type Ca(2+) channel blockers may have the potential to provide an increased number of both BMSC-derived SMCs and ECs of potential use in cell and gene therapy.

A phosphodiesterase-5 inhibitor vardenafil enhances angiogenesis through a protein kinase G-dependent hypoxia-inducible factor-1/vascular endothelial growth factor pathway

OBJECTIVE

We examined whether phosphodiesterase-5 (PDE5) inhibition can promote ischemia-induced angiogenesis.

METHODS AND RESULTS

Unilateral hindlimb ischemia was generated by resecting right femoral artery in wild-type C3H/He mice, treated with either vehicle or a PDE5 inhibitor vardenafil (10 mg/kg per day). Four weeks after surgery, vardenafil significantly enhanced blood flow recovery and augmented capillary collateral formation in ischemic muscle (blood flow ratios of ischemic/nonischemic leg: 0.52+/-0.17 [vehicle] versus 0.92+/-0.09 [vardenafil], P<0.01). Vardenafil upregulated protein expression of vascular endothelial growth factor and hypoxia-inducible factor (HIF)-1 alpha in ischemic muscle and enhanced mobilization of Sca-1/Flk-1-positive endothelial progenitor cells (EPCs) in peripheral blood and bone marrow, contributing to neovascularization. Vardenafil also promoted capillary-like tube formation of human umbilical vein endothelial cells and increased the number of human blood mononuclear cell-derived EPCs in vitro. Furthermore, reporter assays showed that vardenafil and cGMP activated the transactivation activity of HIF-1 under hypoxia. These effects of vardenafil were markedly inhibited by genetic ablation of endothelial nitric oxide synthase, a soluble guanylate cyclase inhibitor, and a protein kinase G inhibitor, respectively.

CONCLUSIONS

Our results suggest that PDE5 inhibition enhances ischemia-induced angiogenesis with mobilization of EPCs through a protein kinase G-dependent HIF-1/vascular endothelial growth factor pathway. PDE5 inhibition may have a therapeutic potential to treat ischemic cardiovascular diseases.

Multipotent mesenchymal progenitor cells are present in endarterectomized tissues from patients with chronic thromboembolic pulmonary hypertension

Factors contributing to the development of a fibrotic vascular scar and pulmonary vascular remodeling leading to chronic thromboembolic pulmonary hypertension (CTEPH) are still unknown. This study investigates the potential contribution of multipotent progenitor cells and myofibroblasts to the development and progression of CTEPH. Histological examination of endarterectomized tissues from patients with CTEPH identified significant neointimal formation. Morphological heterogeneity was observed in cells isolated from these tissues, including a network-like growth pattern and the formation of colony-forming unit-fibroblast-like colonies (CFU-F). Cells typically coexpressed intermediate filaments vimentin and smooth muscle alpha-actin. Cells were characterized by immunofluorescence and quantitated by fluorescent-activated cell sorting (FACS) for the presence of cell surface markers typical of mesenchymal progenitor cells; cells were >99% CD44(+) CD73(+), CD90(+), CD166(+); >80% CD29(+); 45-99% CD105(+); CD34(-) and CD45(-). Cells were capable of adipogenic and osteogenic differentiation, determined by Oil Red O and Alizarin Red staining, respectively. Additionally, a population of Stro-1(+) cells, a marker of bone marrow-derived stromal cells (4.2%), was sorted by FACS and also capable of adipogenic and osteogenic differentiation. In conclusion, this study is the first to identify a myofibroblast cell phenotype to be predominant within endarterectomized tissues, contributing extensively to the vascular lesion/clot. This cell may arise from transdifferentiation of adventitial fibroblasts or differentiation of mesenchymal progenitor cells. The unique microenvironment created by the stabilized clot is likely a factor in stimulating such cellular changes. These findings will be critical in establishing future studies in the development of novel and much needed therapeutic approaches for pulmonary hypertension.

Stem/Progenitor Cells, Atherosclerosis and Cardiovascular Regeneration

Regenerative cell based therapy has potential to become effective adjuvant treatment for patients with atherosclerotic disease. Although data from animal studies support this notion, clinical studies undertaken in patients with acute and chronic coronary artery disease do not conclusively demonstrate benefits of such therapy. There are many questions on the stem cell translational roadmap. The basic mechanisms of stem cell-dependent tissue regeneration are not well understood. There is a debate regarding characterization of specific cell types conferring therapeutic effects. In particular, the role of endothelial progenitor cells as a specific reparative cell subtype is questioned, and the role of myeloid cell linage in fostering of vasculo- and angiogenesis is being increasingly appreciated. Intense discussions surround the place of stem/progenitor cells in atherosclerosis progression, plaque destabilization and vessel remodeling. This paper summarizes the current knowledge on the regenerative stem/progenitor cell definitions, mechanisms of stem cell trafficking, homing and their involvement in atherosclerosis progression.

Stem/Progenitor cells, atherosclerosis and cardiovascular regeneration

Regenerative cell based therapy has potential to become effective adjuvant treatment for patients with atherosclerotic disease. Although data from animal studies support this notion, clinical studies undertaken in patients with acute and chronic coronary artery disease do not conclusively demonstrate benefits of such therapy. There are many questions on the stem cell translational roadmap. The basic mechanisms of stem cell-dependent tissue regeneration are not well understood. There is a debate regarding characterization of specific cell types conferring therapeutic effects. In particular, the role of endothelial progenitor cells as a specific reparative cell subtype is questioned, and the role of myeloid cell linage in fostering of vasculo- and angiogenesis is being increasingly appreciated. Intense discussions surround the place of stem/progenitor cells in atherosclerosis progression, plaque destabilization and vessel remodeling. This paper summarizes the current knowledge on the regenerative stem/progenitor cell definitions, mechanisms of stem cell trafficking, homing and their involvement in atherosclerosis progression.

Donor and recipient contribution to transplant vasculopathy in chronic renal transplant dysfunction

BACKGROUND

Chronic transplant dysfunction is the leading cause of long-term renal allograft loss. One of the histologic hallmarks of chronic transplant dysfunction is transplant vasculopathy characterized by accumulation of smooth muscle cells (SMCs) in the arterial subendothelial space, leading to ischemic graft failure. Currently, no therapy is available for transplant vasculopathy, and knowledge of the origin (donor vs. recipient) of neointimal cells may contribute to develop adequate strategies.

METHODS

Origin of neointimal SMCs, endothelial, and tubular cells was determined in four nephrectomy samples from male recipients transplanted with a female kidney. Recipient-derived cells were detected using X- and Y-chromosome-specific fluorescent in situ hybridization combined with immunofluorescent staining. Specificity and sensitivity of fluorescent in situ hybridization were determined with corresponding controls.

RESULTS

No Y-chromosome-positive cells were detected in the female to female graft, whereas approximately 31% of nucleated cells in male to male grafts had a detectable Y-chromosome. In female to male grafts, a recipient-derived population of neointimal alpha-smooth muscle actin-positive SMCs were detected (6%, range 3%-11%). Percentages of recipient-derived arterial endothelial cells, glomerular endothelial cells, and tubular epithelial cells were 14% (range 4%-32%), 19% (range 7%-31%) and 3% (range 2%-5%), respectively.

CONCLUSIONS

Both donor- and recipient-derived cells contribute to vascular remodeling in clinical renal transplantation. The presence of alpha-smooth muscle actin in donor- and recipient-derived cells supports a constructive role for these cells in neointimal formation. However, the predominance of donor-derived cells in the neointima points to these cells as the likely therapeutic target.

Acute lung injury but not sepsis is associated with increased colony formation by peripheral blood mononuclear cells

Acute lung injury (ALI) and severe sepsis are common critical illnesses associated with the mobilization of bone marrow-derived cells into the circulation. By identifying and determining these cells' functional characteristics, unique prognostic biomarkers can be developed to help investigators understand the mechanisms underlying the pathophysiology of these disorders. We previously demonstrated an increased colony-forming unit (CFU) ability of circulating peripheral blood mononuclear cells (PBMCs) in patients with ALI, compared with healthy control subjects, that also correlated with improved survival. Here we hypothesized that the increased CFUs in ALI are associated with lung injury, and therefore ALI will result in an increased number of CFUs compared with patients exhibiting severe sepsis. To test this, blood was collected from 80 patients (63 with ALI, and 17 with severe sepsis) within 72 hours of diagnosis, and from 5 healthy control subjects. A CFU assay was performed on isolated PBMCs. Lung injury scores and the need for mechanical ventilation were greater in patients with ALI than in patients with severe sepsis (P < 0.0001 for each). CFU numbers were highest in patients with ALI compared with patients manifesting severe sepsis or control subjects (median CFU number [25-75% quartiles] of 61 [13-104] versus 17 [3-34] versus 5 [2-13], P < 0.0005). A trend toward improved survival was demonstrated in patients with high (> or = 48) CFUs (P = 0.06). No relationship between CFUs and mechanical ventilation was evident. Our findings suggest that increased colony-forming ability by PBMCs in ALI results from lung injury, independent of sepsis and mechanical ventilation. Factors contributing to colony formation by PBMCs in ALI, and the role PBMCs play in its pathogenesis remain to be fully established.

Sustained hypoxia promotes the development of a pulmonary artery-specific chronic inflammatory microenvironment

Recent studies demonstrate that sustained hypoxia induces the robust accumulation of leukocytes and mesenchymal progenitor cells in pulmonary arteries (PAs). Since the factors orchestrating hypoxia-induced vascular inflammation are not well-defined, the goal of this study was to identify mediators potentially responsible for recruitment to and retention and differentiation of circulating cells within the hypoxic PA. We analyzed mRNA expression of 44 different chemokine/chemokine receptor, cytokine, adhesion, and growth and differentiation genes in PAs obtained via laser capture microdissection in adjacent lung parenchyma and in systemic arteries by RT-PCR at several time points of hypoxic exposure (1, 7, and 28 days) in Wistar-Kyoto rats. Analysis of inflammatory cell accumulation and protein expression of selected genes was concomitantly assessed by immunochemistry. We found that hypoxia induced progressive accumulation of monocytes and dendritic cells in the vessel wall with few T cells and no B cells or neutrophils. Upregulation of stromal cell-derived factor-1 (SDF-1), VEGF, growth-related oncogene protein-alpha (GRO-alpha), C5, ICAM-1, osteopontin (OPN), and transforming growth factor-beta (TGF-beta) preceded mononuclear cell influx. With time, a more complex pattern of gene expression developed with persistent upregulation of adhesion molecules (ICAM-1, VCAM-1, and OPN) and monocyte/fibrocyte growth and differentiation factors (TGF-beta, endothelin-1, and 5-lipoxygenase). On return to normoxia, expression of many genes (including SDF-1, monocyte chemoattractant protein-1, C5, ICAM-1, and TGF-beta) rapidly returned to control levels, changes that preceded the disappearance of monocytes and reversal of vascular remodeling. In conclusion, sustained hypoxia leads to the development of a complex, PA-specific, proinflammatory microenvironment capable of promoting recruitment, retention, and differentiation of circulating monocytic cell populations that contribute to vascular remodeling.

Hemin promotes proliferation and differentiation of endothelial progenitor cells via activation of AKT and ERK

Increased neovascularization is commonly observed in hemorrhagic plaques and associated with rupture of atherosclerotic lesions. This study aims to investigate whether hemin accumulated at the site of hematoma promotes neovascularization through affecting the growth and function of endothelial progenitor cells (EPCs) and the possible mechanism involved. Here we demonstrated that hemin promoted a significant increase in neovessel formation in matrigel plugs embedded in vivo and enhanced the proliferation and endothelial gene expression in EPCs in vitro. VEGF-induced migration response and the capability to incorporate into the vascular networks were markedly enhanced in hemin-treated EPCs. Hemin induced the phosphorylation of ERK and AKT but not p38 or JNK. The inhibition of AKT or ERK activation significantly attenuated the effect of hemin on cell proliferation. However, the enhanced migration response induced by hemin was significantly suppressed by the inhibition of AKT but not ERK. Hemin induced significant increase in reactive oxygen species (ROS) production and hemin-induced angiogenic response of EPCs was substantially reduced by treatment with N-acetylcysteine. Collectively, these data support that hemin-induced ROS mediates the activation of AKT and ERK signaling pathways, which in turn promotes the cell proliferation and function of EPCs. J. Cell. Physiol. 219: 617-625, 2009. (c) 2009 Wiley-Liss, Inc.

p66ShcA modulates oxidative stress and survival of endothelial progenitor cells in response to high glucose

AIMS

A close relationship exists between hyperglycaemia, oxidative stress, and diabetic complications. In fact, high glucose (HG) determines the overproduction of reactive oxygen species (ROS) by the mitochondria. p66ShcA is a gene that regulates the apoptotic responses to oxidative stress. Indeed, p66ShcA knockout (ko) mice display decreased ROS production and increased resistance to ROS-induced cell death in a variety of pathophysiological settings. Reduced endothelial progenitor cell (EPC) number, differentiation, and function are relevant components of the angiogenesis impairment observed in diabetic patients. We examined the role of p66ShcA in the EPC deficit induced by HG.

METHODS AND RESULTS

Mouse bone marrow-derived c-kit+ cells differentiate in endothelial-like cells when plated on fibronectin (BM-derived EPCs). We found that cell culture in the presence of HG up-regulated p66ShcA protein expression and that HG exposure markedly decreased the number of BM-derived EPCs. Conversely, p66ShcA ko BM-derived EPCs were not sensitive to HG inhibition. Indeed, the resistance of p66ShcA ko BM-derived EPCs to HG was associated with reduced levels of both apoptosis and oxidative stress. To functionally link the HG response to ROS production, p66ShcA ko BM-derived EPCs were reconstituted either with p66ShcA wild-type (wt) or with a p66ShcA allele (p66ShcA qq) that was devoid of its ROS-generating function. We found that only p66ShcA wt and not the qq mutant rescued p66ShcA ko cell sensitivity to HG. One major feature of oxidative stress is its ability to reduce the bio-availability of nitric oxide (NO) that, in turn, plays a crucial role in endothelial differentiation and function. We found that the p66ShcA deletion prevented the HG-induced increase of nitrotyrosine, and that the resistance to HG of p66ShcA ko BM-derived EPCs was prevented by NO synthase inhibition. With a reciprocal approach, the treatment of p66ShcA wt cells with a NO donor prevented the HG-induced deficit. Finally, using a Matrigel plug angiogenesis assay, we demonstrated that p66ShcA ko prevented diabetic impairment of angiogenesis in vivo.

CONCLUSION

p66ShcA deletion rescues the BM-derived EPCs defect induced by HG, indicating p66ShcA as a potential therapeutic target in diabetic vasculopathy.

MicroRNAs as novel regulators of angiogenesis

MicroRNAs are short noncoding RNAs that function as negative regulators of gene expression. Posttranscriptional regulation by miRNAs is important for many aspects of development, homeostasis, and disease. Endothelial cells are key regulators of different aspects of vascular biology, including the formation of new blood vessels (angiogenesis). Here, we review the approaches and current experimental evidence for the involvement of miRNAs in the regulation of the angiogenic process and their potential therapeutic applications for vascular diseases associated with abnormal angiogenesis.