Stromal cell-derived factor-1 enhances pro-angiogenic effect of granulocyte-colony stimulating factor

Advances for the treatment of lower extremity arterial disease associated with diabetes mellitus

Lower extremity arterial disease (LEAD) is a major vascular complication of diabetes. Vascular endothelial cells dysfunction can exacerbate local ischemia, leading to a significant increase in amputation, disability, and even mortality in patients with diabetes combined with LEAD. Therefore, it is of great clinical importance to explore proper and effective treatments. Conventional treatments of diabetic LEAD include lifestyle management, medication, open surgery, endovascular treatment, and amputation. As interdisciplinary research emerges, regenerative medicine strategies have provided new insights to treat chronic limb threatening ischemia (CLTI). Therapeutic angiogenesis strategies, such as delivering growth factors, stem cells, drugs to ischemic tissues, have also been proposed to treat LEAD by fundamentally stimulating multidimensional vascular regeneration. Recent years have seen the rapid growth of tissue engineering technology; tissue-engineered biomaterials have been used to study the treatment of LEAD, such as encapsulation of growth factors and drugs in hydrogel to facilitate the restoration of blood perfusion in ischemic tissues of animals. The primary purpose of this review is to introduce treatments and novel biomaterials development in LEAD. Firstly, the pathogenesis of LEAD is briefly described. Secondly, conventional therapies and therapeutic angiogenesis strategies of LEAD are discussed. Finally, recent research advances and future perspectives on biomaterials in LEAD are proposed.

Treating ischemia via recruitment of antigen-specific T cells

Ischemic diseases are a leading cause of mortality and can result in autoamputation of lower limbs. We explored the hypothesis that implantation of an antigen-releasing scaffold, in animals previously vaccinated with the same antigen, can concentrate T_H2 T cells and enhance vascularization of ischemic tissue. This approach may be clinically relevant, as all persons receiving childhood vaccines recommended by the Centers for Disease Control and Prevention have vaccines that contain aluminum, a T_H2 adjuvant. To test the hypothesis, mice with hindlimb ischemia, previously vaccinated with ovalbumin (OVA) and aluminum, received OVA-releasing scaffolds. Vaccinated mice receiving OVA-releasing scaffolds locally concentrated antigen-specific T_H2 T cells in the surrounding ischemic tissue. This resulted in local angiogenesis, increased perfusion in ischemic limbs, and reduced necrosis and enhanced regenerating myofibers in the muscle. These findings support the premise that antigen depots may provide a treatment for ischemic diseases in patients previously vaccinated with aluminum-containing adjuvants.

CD4 T-cells regulate angiogenesis and myogenesis

Ischemic diseases, such as peripheral artery disease, affect millions of people worldwide. While CD4+ T-cells regulate angiogenesis and myogenesis, it is not understood how the phenotype of these adaptive immune cells regulate these regenerative processes. The secreted factors from different types of CD4+ T-cells (Th1, Th2, Th17, and Treg) were utilized in a series of in vitro assays and delivered from an injectable alginate biomaterial into a murine model of ischemia to study their effects on vascular and skeletal muscle regeneration. Conditioned medium from Th2 and Th17  T-cells enhanced angiogenesis in vitro and in vivo, in part by directly stimulating endothelial sprouting. Th1 conditioned medium induced vascular regression in vitro and provided no benefit to angiogenesis in vivo. Th1, Th2, and Th17 conditioned medium, to varying extents, enhanced muscle precursor cell proliferation and inhibited their differentiation in vitro, and prolonged early stages of muscle regeneration in vivo. Treg conditioned medium had a moderate or no effect on these processes in vitro and no discernible effect in vivo. These findings suggest that Th2 and Th17 T-cells may enhance angiogenesis and myogenesis in ischemic injuries, which may be useful in the design of immunomodulatory biomaterials to treat these diseases.

Targeted release of stromal cell-derived factor-1α by reactive oxygen species-sensitive nanoparticles results in bone marrow stromal cell chemotaxis and homing, and repair of vascular injury caused by electrical burns

Rapid repair of vascular injury is an important prognostic factor for electrical burns. This repair is achieved mainly via stromal cell-derived factor (SDF)-1α promoting the mobilization, chemotaxis, homing, and targeted differentiation of bone marrow mesenchymal stem cells (BMSCs) into endothelial cells. Forming a concentration gradient from the site of local damage in the circulation is essential to the role of SDF-1α. In a previous study, we developed reactive oxygen species (ROS)-sensitive PPADT nanoparticles containing SDF-1α that could degrade in response to high concentration of ROS in tissue lesions, achieving the goal of targeted SDF-1α release. In the current study, a rat vascular injury model of electrical burns was used to evaluate the effects of targeted release of SDF-1α using PPADT nanoparticles on the chemotaxis of BMSCs and the repair of vascular injury. Continuous exposure to 220 V for 6 s could damage rat vascular endothelial cells, strip off the inner layer, significantly elevate the local level of ROS, and decrease the level of SDF-1α. After injection of Cy5-labeled SDF-1α-PPADT nanoparticles, the distribution of Cy5 fluorescence suggested that SDF-1α was distributed primarily at the injury site, and the local SDF-1α levels increased significantly. Seven days after injury with nanoparticles injection, aggregation of exogenous green fluorescent protein-labeled BMSCs at the injury site was observed. Ten days after injury, the endothelial cell arrangement was better organized and continuous, with relatively intact vascular morphology and more blood vessels. These results showed that SDF-1α-PPADT nanoparticles targeted the SDF-1α release at the site of injury, directing BMSC chemotaxis and homing, thereby promoting vascular repair in response to electrical burns.

Surface functionalization of electrospun scaffolds using recombinant human decorin attracts circulating endothelial progenitor cells

Decorin (DCN) is an important small leucine-rich proteoglycan present in the extracellular matrix (ECM) of many organs and tissues. Endothelial progenitor cells (EPCs) are able to interact with the surrounding ECM and bind to molecules such as DCN. Here, we recombinantly produced full-length human DCN under good laboratory practice (GLP) conditions, and after detailed immunological characterization, we investigated its potential to attract murine and human EPCs (mEPCs and hECFCs). Electrospun polymeric scaffolds were coated with DCN or stromal cell-derived factor-1 (SDF-1α) and were then dynamically cultured with both cell types. Cell viability was assessed via imaging flow cytometry. The number of captured cells was counted and compared with the non-coated controls. To characterize cell-scaffold interactions, immunofluorescence staining and scanning electron microscopy analyses were performed. We identified that DCN reduced T cell responses and attracted innate immune cells, which are responsible for ECM remodeling. A significantly higher number of EPCs attached on DCN- and SDF-1α-coated scaffolds, when compared with the uncoated controls. Interestingly, DCN showed a higher attractant effect on hECFCs than SDF-1α. Here, we successfully demonstrated DCN as promising EPC-attracting coating, which is particularily interesting when aiming to generate off-the-shelf biomaterials with the potential of in vivo cell seeding.

Stromal derived factor-1 and granulocyte-colony stimulating factor treatment improves regeneration of Pax7-/- mice skeletal muscles

BACKGROUND

The skeletal muscle has the ability to regenerate after injury. This process is mediated mainly by the muscle specific stem cells, that is, satellite cells. In case of extensive damage or under pathological conditions, such as muscular dystrophy, the process of muscle reconstruction does not occur properly. The aim of our study was to test whether mobilized stem cells, other than satellite cells, could participate in skeletal muscle reconstruction.

METHODS

Experiments were performed on wild-type mice and mice lacking the functional Pax7 gene, that is, characterized by the very limited satellite cell population. Gastrocnemius mice muscles were injured by cardiotoxin injection, and then the animals were treated by stromal derived factor-1 (Sdf-1) with or without granulocyte-colony stimulating factor (G-CSF) for 4 days. The muscles were subjected to thorough assessment of the tissue regeneration process using histological and in vitro methods, as well as evaluation of myogenic factors' expression at the transcript and protein levels.

RESULTS

Stromal derived factor-1 alone and Sdf-1 in combination with G-CSF significantly improved the regeneration of Pax7-/- skeletal muscles. The Sdf-1 and G-CSF treatment caused an increase in the number of mononucleated cells associated with muscle fibres. Further analysis showed that Sdf-1 and G-CSF treatment led to the rise in the number of CD34+ and Cxcr4+ cells and expression of Cxcr7.

CONCLUSIONS

Stromal derived factor-1 and G-CSF stimulated regeneration of the skeletal muscles deficient in satellite cells. We suggest that mobilized CD34+, Cxcr4+, and Cxcr7+ cells can efficiently participate in the skeletal muscle reconstruction and compensate for the lack of satellite cells.

Ultrasound-induced microbubble destruction promotes targeted delivery of adipose-derived stem cells to improve hind-limb ischemia of diabetic mice

This study aimed to investigate whether ultrasound-induced microbubble destruction was able to promote targeted delivery of adipose-derived stem cells (ASCs) to improve hind-limb ischemia of diabetic mice. Ischemia was induced in the lower limb of db/db mice which were then randomly divided into 5 groups: PBS group, Sham group, ultrasound + microbubble group (US+MB), US+MB+ASCs group and ASCs group. Contrast-enhanced ultrasound perfusion imaging showed the ratio of blood flow in ischemic hind-limb to that in contralateral limb increased over time in five groups. A significant enhancement in US+MB+ASCs group was observed compared with US+MB group (P<0.01). Immunofluorescence microscopy of hind-limb muscle showed the microvessel density (microvessels/skeletal muscle fibers) and arteriolar density in US+MB+ASCs group were higher than in US+MB group, and significantly higher than in other control groups (P<0.01). Masson staining indicated the degree of muscle fibrosis in US+MB+ASCs group was lower than in US+MB. 3 and 7 days after therapy, ELISA and RT-PCR showed the expression of VEGF, P-selectin, ICAM-1 and SDF-1 in US+MB+ASCs group was higher than in US+MB group, and dramatically increased as compared to other groups (P<0.01). 3 and 7 days after therapy, Western blot assay showed the protein expression of P-P13K, P-AKT, VEGF, P-selectin, ICAM-1 and SDF-1 in US+MB+ASCs group was higher than US+MB group (P<0.01). The bioeffects of ultrasound-induced microbubble cavitation is able to up-regulate the expression of pro-inflammatory cytokines, which may improve the targeted delivery, adhesion and paracrine of ASCs, attenuating the hind-limb ischemia in diabetic mice.

Profound Actions of an Agonist of Growth Hormone-Releasing Hormone on Angiogenic Therapy by Mesenchymal Stem Cells

OBJECTIVE

The efficiency of cell therapy is limited by poor cell survival and engraftment. Here, we studied the effect of the growth hormone-releasing hormone agonist, JI-34, on mesenchymal stem cell (MSC) survival and angiogenic therapy in a mouse model of critical limb ischemia.

APPROACH AND RESULTS

Mouse bone marrow-derived MSCs were incubated with or without 10(-8) mol/L JI-34 for 24 hours. MSCs were then exposed to hypoxia and serum deprivation to detect the effect of preconditioning on cell apoptosis, migration, and tube formation. For in vivo tests, critical limb ischemia was induced by femoral artery ligation. After surgery, mice received 50 μL phosphate-buffered saline or with 1×10(6) MSCs or with 1×10(6) JI-34-reconditioned MSCs. Treatment of MSCs with JI-34 improved MSC viability and mobility and markedly enhanced their capability to promote endothelial tube formation in vitro. These effects were paralleled by an increased phosphorylation and nuclear translocation of signal transducer and activator of transcription 3. In vivo, JI-34 pretreatment enhanced the engraftment of MSCs into ischemic hindlimb muscles and augmented reperfusion and limb salvage compared with untreated MSCs. Significantly more vasculature and proliferating CD31(+) and CD34(+) cells were detected in ischemic muscles that received MSCs treated with JI-34.

CONCLUSIONS

Our studies demonstrate a novel role for JI-34 to markedly improve therapeutic angiogenesis in hindlimb ischemia by increasing the viability and mobility of MSCs. These findings support additional studies to explore the full potential of growth hormone-releasing hormone agonists to augment cell therapy in the management of ischemia.

A new method of wound treatment: targeted therapy of skin wounds with reactive oxygen species-responsive nanoparticles containing SDF-1α

Objective

To accelerate wound healing through promoting vascularization by using reactive oxygen species (ROS)-responsive nanoparticles loaded with stromal cell-derived factor-1α(SDF-1α).

Methods

The ROS-reactive nanomaterial poly-(1,4-phenyleneacetone dimethylene thioketal) was synthesized, and its physical and chemical properties were characterized. ROS-responsive nanoparticles containing SDF-1α were prepared through a multiple emulsion solvent evaporation method. The loading capacity, stability, activity of the encapsulated protein, toxicity, and in vivo distribution of these nanoparticles were determined. These nanoparticles were administered by intravenous infusion to mice with full-thickness skin defects to study their effects on the directed chemotaxis of bone marrow mesenchymal stem cells, wound vascularization, and wound healing.

Results

The synthesized ROS-reactive organic polymer poly-(1,4-phenyleneacetone dimethylene thioketal) possessed a molecular weight of approximately 11.5 kDa with a dispersity of 1.97. ROS-responsive nanoparticles containing SDF-1α were prepared with an average diameter of 110 nm and a drug loading capacity of 1.8%. The encapsulation process showed minimal effects on the activity of SDF-1α, and it could be effectively released from the nanoparticles in the presence of ROS. Encapsulated SDF-1α could exist for a long time in blood. In mice with full-thickness skin defects, SDF-1α was effectively released and targeted to the wounds, thus promoting the chemotaxis of bone marrow mesenchymal stem cells toward the wound and its periphery, inducing wound vascularization, and accelerating wound healing.

The mRNA expressions and immunohistochemistry of factors involved in angiogenesis and lymphangiogenesis in the early stage of rat skin incision wounds

Wound healing evaluation is important in forensic pathology, in which angiogenesis plays an important role. We have already shown that vascular endothelial growth factor A (VEGF) is produced in the rat skin incision wounds by neutrophils, endothelial cells, and fibroblasts. In this study, we assessed the changes in the mRNA expressions of various factors possibly involved in angiogenesis including angiopoietin (ANGPT) 1 and 2, cadherin 5 (CDH5), granulocyte-macrophage colony stimulating factor (CSF2/GM-CSF), granulocyte colony stimulating factor (CSF3/G-CSF), chemokine (C-X-C motif) ligand 2 (CXCL2), chemokine (C-X-C motif) ligand12 (CXCL12/SDF1), endothelin 1 (ET1), fibroblast growth factor 1 (FGF 1), hepatocyte growth factor (HGF), hypoxia inducible factor 1 alpha (HIF1a), leptin, matrix metallopepitidase 9 (MMP9), serpine/plasminogen activator inhibitor1 (PAI1), platelet-derived growth factor-A (PDGF-A), transforming growth factor alpha and beta 1 (TGFa and b1), tenomodulin (TNMD), and troponin I type 2 (TNNI2) in the early stage of the rat skin incision wounds by real time RT-PCR. Factors reported to be involved in lymphangiogenesis such as fibroblast growth factor 2 (FGF 2), c-fos induced growth factor (FIGF/VEGF-D), forkhead box C2 (FOXC2), and prospero homeobox 1 (PROX1) were also studied. One and 3 days after the dorsal skin incisions, wounds on male Sprague-Dawley rats showed the statistically significant increases in the mRNA expressions for CXCL2, CSF3, MMP9, PAI1, and CSF2, whereas TGFa, TNNI2, FGF1, TNMD, leptin, and CXCL12 showed the statistically significant decreases. Interestingly, lymphgangiogenic factors FOXC2, PROX1, and FGF2 also showed the statistically significant decreases. In situ hybridization and immunohistochemistry showed the mRNA and protein positivity in endothelial cells, fibroblasts, and some leukocytes at the bottom of the wound tissue for PAI1, CSF3, and MMP9, 1 day after the skin incisions. Our novel findings show the possible involvement of several factors involved in angiogenesis and lymphangiogenesis in the early stage of wound healing process, which may be useful for forensic wound evaluations.

Influence of growth factors and cytokines on angiogenic function of endothelial progenitor cells: a review of in vitro human studies

Growth factors and cytokines released at sites of injury and inflammation play an important role in stimulating endothelial progenitor cell (EPC) migration to these sites. A comparative analysis of the literature shows under neutral in vitro conditions (pH 7.4), several growth factors and cytokines influenced favorably indices of EPC angiogenic function. They included SDF-1, VEGF, PlGF, FGF-2, NGF and IL-1β. Others, e.g. TNF-α, have an unfavorable influence. SDF-1 and VEGF in combination increased chemotactic cell migration and reduced apoptosis caused by serum starvation. Under acidic conditions (pH 6.5), the biological activity of certain growth factors may be impaired, although TPO, SCF and IL-3 were each able to rescue EPCs from acidic exposure apoptosis, a combination of these three factors stimulated cell proliferation and prevented apoptosis. Possible combinations of growth factors and cytokines together with EPC transplantation may provide for a greater extent of vessel repair and new vessel formation.

Platelet neuropeptide Y is critical for ischemic revascularization in mice

We previously reported that the sympathetic neurotransmitter neuropeptide Y (NPY) is potently angiogenic, primarily through its Y2 receptor, and that endogenous NPY is crucial for capillary angiogenesis in rodent hindlimb ischemia. Here we sought to identify the source of NPY responsible for revascularization and its mechanisms of action. At d 3, NPY(-/-) mice demonstrated delayed recovery of blood flow and limb function, consistent with impaired collateral conductance, while ischemic capillary angiogenesis was reduced (~70%) at d 14. This biphasic temporal response was confirmed by 2 peaks of NPY activation in rats: a transient early increase in neuronally derived plasma NPY and increase in platelet NPY during late-phase recovery. Compared to NPY-null platelets, collagen-activated NPY-rich platelets were more mitogenic (~2-fold vs. ~1.6-fold increase) for human microvascular endothelial cells, and Y2/Y5 receptor antagonists ablated this difference in proliferation. In NPY(+/+) mice, ischemic angiogenesis was prevented by platelet depletion and then restored by transfusion of platelets from NPY(+/+) mice, but not NPY(-/-) mice. In thrombocytopenic NPY(-/-) mice, transfusion of wild-type platelets fully restored ischemia-induced angiogenesis. These findings suggest that neuronally derived NPY accelerates the early response to femoral artery ligation by promoting collateral conductance, while platelet-derived NPY is critical for sustained capillary angiogenesis.

Cellular and subcellular localization of CXCL12 and CXCR4 in rat nociceptive structures: physiological relevance

Initial studies implicated the chemokine CXC motif ligand 12 (CXCL12) and its cognate CXC motif receptor 4 (CXCR4) in pain modulation. However, there has been no description of the distribution, transport and axonal sorting of CXCL12 and CXCR4 in rat nociceptive structures, and their direct participation in nociception modulation has not been demonstrated. Here, we report that acute intrathecal administration of CXCL12 induced mechanical hypersensitivity in naive rats. This effect was prevented by a CXCR4-neutralizing antibody. To determine the morphological basis of this behavioural response, we used light and electron microscopic immunohistochemistry to map CXCL12- and CXCR4-immunoreactive elements in dorsal root ganglia, lumbar spinal cord, sciatic nerve and skin. Light microscopy analysis revealed CXCL12 and CXCR4 immunoreactivity in calcitonin gene related peptide-containing peptidergic primary sensory neurons, which were both conveyed to central and peripheral sensory nerve terminals. Electron microscopy clearly demonstrated CXCL12 and CXCR4 immunoreactivity in primary sensory nerve terminals in the dorsal horn; both were sorted into small clear vesicles and large dense-core vesicles. This suggests that CXCL12 and CXCR4 are trafficked from nerve cell bodies to the dorsal horn. Double immunogold labelling for CXCL12 and calcitonin gene related peptide revealed partial vesicular colocalization in axonal terminals. We report, for the first time, that CXCR4 receptors are mainly located on the neuronal plasma membrane, where they are present at pre-synaptic and post-synaptic sites of central terminals. Receptor inactivation experiments, behavioural studies and morphological analyses provide strong evidence that the CXCL12/CXCR4 system is involved in modulation of nociceptive signalling.

Endothelial dysfunction and diabetes: effects on angiogenesis, vascular remodeling, and wound healing

Diabetes mellitus (DM) is a chronic metabolic disorder characterized by inappropriate hyperglycemia due to lack of or resistance to insulin. Patients with DM are frequently afflicted with ischemic vascular disease or wound healing defect. It is well known that type 2 DM causes amplification of the atherosclerotic process, endothelial cell dysfunction, glycosylation of extracellular matrix proteins, and vascular denervation. These complications ultimately lead to impairment of neovascularization and diabetic wound healing. Therapeutic angiogenesis remains an attractive treatment modality for chronic ischemic disorders including PAD and/or diabetic wound healing. Many experimental studies have identified better approaches for diabetic cardiovascular complications, however, successful clinical translation has been limited possibly due to the narrow therapeutic targets of these agents or the lack of rigorous evaluation of pathology and therapeutic mechanisms in experimental models of disease. This paper discusses the current body of evidence identifying endothelial dysfunction and impaired angiogenesis during diabetes.

Mechanisms of hepatoprotective effect of immobilized granulocyte colony-stimulating factor

The effect of immobilized granulocyte CSF on morphological characteristics and functional state of the liver was studied during chronic toxic hepatitis. The mechanisms of the therapeutic action of this agent were evaluated. The product had a strong hepatoprotective effect and exhibited the antiinflammatory and antisclerotic properties. The mechanism of activation of reserve systems for cell renewal (involved in restoration of the liver tissue) is probably related to an increase in proliferative activity of early precursor cells in the bone marrow, mobilization of these cells into the peripheral circulation, and directed homing into the liver tissue where they activate local regenerative mechanisms and prevent hepatocyte destruction. It should be emphasized that the concentration of SDF-1 increases in the liver tissue, but decreases in the bone marrow. These changes create the concentration gradient, which determines the migration of undifferentiated precursor cells to the liver.

Defective CXCR4 expression in aged bone marrow cells impairs vascular regeneration

The chemokine stromal cell-derived factor-1 (SDF-1) plays a critical role in mobilizing precursor cells in the bone marrow and is essential for efficient vascular regeneration and repair. We recently reported that calcium augments the expression of chemokine receptor CXCR4 and enhances the angiogenic potential of bone marrow derived cells (BMCs). Neovascularization is impaired by aging therefore we suggested that aging may cause defects of CXCR4 expression and cellular responses to calcium. Indeed we found that both the basal and calcium-induced surface expression of CXCR4 on BMCs was significantly reduced in 25-month-old mice compared with 2-month-old mice. Reduced Ca-induced CXCR4 expression in BMC from aged mice was associated with defective calcium influx. Diminished CXCR4 surface expression in BMC from aged mice correlated with diminished neovascularization in an ischemic hindlimb model with less accumulation of CD34⁺ progenitor cells in the ischemic muscle with or without local overexpression of SDF-1. Intravenous injection of BMCs from old mice homed less efficiently to ischemic muscle and stimulated significantly less neovascularization compared with the BMCs from young mice. Transplantation of old BMCs into young mice did not reconstitute CXCR4 functions suggesting that the defects were not reversible by changing the environment. We conclude that defects of basal and calcium-regulated functions of the CXCR4/SDF-1 axis in BMCs contribute significantly to the age-related loss of vasculogenic responses.

How safe and how good are drug-eluting stents?

Percutaneous transluminal coronary angioplasty revolutionized therapy for coronary artery disease. This early promise of a viable alternative to surgical treatment of coronary artery disease was thwarted by the high rates of angiographic restenosis. The advent of stenting reduced the rates of restenosis, although it was hindered by the new problem of in-stent restenosis. It was demonstrated that in-stent restenosis was the result of a new pathology in the form of neointimal hyperplasia, which was a maladaptive healing response to bare-metal stent implantation. Recently, the introduction of drug-eluting stents (DES) technology has offered a new solution to the problem of restenosis. Current evidence suggests that although DES have reduced restenosis rates, important concerns have been raised regarding increased stent thrombosis, myocardial infarction and death. The purpose of this article is to examine the efficacy and safety data of DES as highlighted in recent publications and to further discuss the biomolecular mechanisms of accelerated endothelization and stent thrombosis. In addition, we will examine some of the newer stent technologies available.

Augmentation of neovascularization in murine hindlimb ischemia by combined therapy with simvastatin and bone marrow-derived mesenchymal stem cells transplantation

Objectives

We postulated that combining high-dose simvastatin with bone marrow derived-mesenchymal stem cells (MSCs) delivery may give better prognosis in a mouse hindlimb ischemia model.

Methods

Mouse hindlimb ischemia model was established by ligating the right femoral artery. Animals were grouped (n = 10) to receive local injection of saline without cells (control and simvastatin groups) or with 5 × 10⁶ MSCs (MSCs group).Animals received either simvastatin (20 mg/kg/d, simvastatin and combination groups) or saline(control and MSCs group) gavages for continual 21 days. The blood flow was assessed by laser Doppler imaging at day 0,10 and 21 after surgery, respectively. Ischemic muscle was harvested for immunohistological assessments and for VEGF protein detection using western blot assay at 21 days post-surgery. In vitro, MSCs viability was measured by MTT and flow cytometry following culture in serum-free medium for 24 h with or without simvastatin. Release of VEGF by MSCs incubated with different doses of simvastatin was assayed using ELISA.

Results

Combined treatment with simvastatin and MSCs induced a significant improvement in blood reperfusion, a notable increase in capillary density, a highest level of VEGF protein and a significant decrease in muscle cell apoptosis compared with other groups. In vitro, simvastatin inhibited MSCs apoptosis and increased VEGF release by MSCs.

Conclusions

Combination therapy with high-dose simvastatin and bone marrow-derived MSCs would augment functional neovascularization in a mouse model of hindlimb ischemia.

Zinc supplementation results in improved therapeutic potential of bone marrow-derived mesenchymal stromal cells in a mouse ischemic limb model

BACKGROUND AIMS

We wanted to determine whether zinc supplementation can inhibit bone marrow-derived mesenchymal stromal cell (MSC) apoptosis and enhance their tissue regenerative potential a in mouse ischemic hindlimb model.

METHODS

Rat bone marrow cells were cultured and the resulting MSC were passaged for 3-7 generations. The proliferation and apoptosis of MSC was examined by 3-[4,5-dimethyl-2-thiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) assay and flow cytometry analysis. The activation of protein kinases B (Akt) was determined by Western blots. Vascular endothelial growth factor (VEGF) levels were examined by enzyme-linked immunosorbent assay. The mouse hindlimb ischemic model was established by ligating the right femoral artery. Mice received MSC, zinc-treated MSC or vehicle. The blood flow was assessed by laser Doppler imaging. The survival rate of donor cells was quantified by real-time polymerase chain reaction for the sex-determining region of the Y-chromosome (Sry). Angiogenesis was assessed by histochemical staining and immunofluoresence staining.

RESULTS

Supplementation with physiologic amounts of zinc caused a marked attenuation of cell apoptosis, enhanced cell viabilities, increased VEGF release and up-regulated Akt activation. Zinc-treated MSC delivered into ischemic hindlimbs resulted in significant improvements in limb blood perfusion by increased implanted MSC survival and stimulated angiogenesis.

CONCLUSIONS

This study demonstrates the potential of zinc supplement to enhance survival of engrafted MSC and ameliorate their tissue regenerative potential in a mouse ischemic hindlimb model.

Expression of stem cell factor/c-kit signaling pathway components in diabetic fibrovascular epiretinal membranes

PURPOSE

Stem cell factor (SCF)/c-kit signaling promotes recruitment of endothelial progenitor cells and contributes to ischemia-induced new vessel formation. We investigated the expression of the components of this pathway, including c-kit, SCF, granulocyte colony-stimulating factor (G-CSF), endothelial nitric oxide synthase (eNOS), and the chemokine receptor CXCR4, in proliferative diabetic retinopathy (PDR) epiretinal membranes.

METHODS

Membranes from eight patients with active PDR and 12 patients with inactive PDR were studied by immunohistochemistry.

RESULTS

Blood vessels expressed c-kit, SCF, G-CSF, eNOS, and CXCR4 in 18, 15, 19, 20, and 20 out of 20 membranes, respectively. Significant correlations were detected between the number of blood vessels expressing CD34 and the number of blood vessels expressing SCF (r=0.463; p=0.04), G-CSF (r=0.87; p<0.001), eNOS (r=0.864; p<0.001), and CXCR4 (r=0.864; p<0.001). Stromal cells expressed c-kit, SCF, eNOS, and CXCR4 in 19, 15, 20, and 20 membranes, respectively. The numbers of blood vessels expressing CD34 (p=0.005), c-kit (p=0.03), G-CSF (p=0.007), eNOS (p=0.001), and CXCR4 (p=0.018) and stromal cells expressing c-kit (p=0.013), SCF (p<0.001), eNOS (p=0.048), and CXCR4 (p=0.003) were significantly higher in active membranes than in inactive membranes.

CONCLUSIONS

SCF/c-kit signaling might contribute to neovascularization in PDR.

Safety and efficacy of therapeutic angiogenesis as a novel treatment in patients with critical limb ischemia

BACKGROUND

In some patients with critical limb ischemia (CLI) the possibility of revascularizing treatment does not exist. In this case therapeutic angiogenesis (TA) using autologous endothelial progenitor cell (EPC) transplantation could be an alternative. The objective of our study was to evaluate the safety and efficacy of TA using EPC.

METHODS

Twenty-eight patients with CLI who were not candidates for surgical or endovascular revascularization were included in a prospective study. To mobilize EPCs from the bone marrow, granulocyte colony-stimulating growth factor was injected subcutaneously at doses of 5 microg/kg/day for 5 days. Apheresis was performed, obtaining 50 mL of blood with a high rate of EPCs (CD34(+) and CD133(+) cells were counted). EPCs were implanted in the ischemic limb by intramuscular injections. Primary end points were the safety and feasibility of the procedure and limb salvage rate for amputation at 12 months. Other variables studied were improvement in rest pain, healing of ulcers, ankle-brachial pressure index (ABI), and digital plethysmography. All procedures were done pretreatment and every 3 months for a year on average. Postransplantation arteriography was done in selected cases.

RESULTS

No adverse effects were observed. Mean follow-up was 14 months. Before treatment, mean basal ABI was 0.35+/-0.2 and at 18 months postimplantation, 0.72+/-0.51 (p=0.009). There was a mean decrease of five points in pain scale: basal 8.7+/-1, after TA 3.8+/-2.9 (p=0.01). Seven patients required major amputation. Kaplan-Meier analysis revealed a limb salvage rate of 74.4% after 1 year.

CONCLUSION

Implantation of EPCs in CLI is a safe alternative, improves tissue perfusion, and obtains high amputation-free rates. Nevertheless, this is a small cohort and results should be tested with long randomized trials.

Combination stem cell therapy for heart failure

Patients with congestive heart failure (CHF) that are not eligible for transplantation have limited therapeutic options. Stem cell therapy such as autologous bone marrow, mobilized peripheral blood, or purified cells thereof has been used clinically since 2001. To date over 1000 patients have received cellular therapy as part of randomized trials, with the general consensus being that a moderate but statistically significant benefit occurs. Therefore, one of the important next steps in the field is optimization. In this paper we discuss three ways to approach this issue: a) increasing stem cell migration to the heart; b) augmenting stem cell activity; and c) combining existing stem cell therapies to recapitulate a "therapeutic niche". We conclude by describing a case report of a heart failure patient treated with a combination stem cell protocol in an attempt to augment beneficial aspects of cord blood CD34 cells and mesenchymal-like stem cells.

Granulocyte colony-stimulating factor activating HIF-1alpha acts synergistically with erythropoietin to promote tissue plasticity

Stroke and peripheral limb ischemia are serious clinical problems with poor prognosis and limited treatment. The cytokines erythropoietin (EPO) and granulocyte-colony stimulating factor (G-CSF) have been used to induce endogenous cell repair and angiogenesis. Here, we demonstrated that the combination therapy of EPO and G-CSF exerted synergistic effects on cell survival and functional recovery from cerebral and peripheral limbs ischemia. We observed that even under normoxic conditions, G-CSF activates hypoxia-inducible factor-1alpha (HIF-1alpha), which then binds to the EPO promoter and enhances EPO expression. Serum EPO level was significantly increased by G-CSF injection, with the exception of Tg-HIF-1alpha(+f/+f) mice. The neuroplastic mechanisms exerted by EPO combined with G-CSF included enhanced expression of the antiapoptotic protein of Bcl-2, augmented neurotrophic factors synthesis, and promoted neovascularization. Further, the combination therapy significantly increased homing and differentiation of bone marrow stem cells (BMSCs) and intrinsic neural progenitor cells (INPCs) into the ischemic area. In summary, EPO in combination with G-CSF synergistically enhanced angiogenesis and tissue plasticity in ischemic animal models, leading to greater functional recovery than either agent alone.

SDF-1alpha/CXCL12 enhances GABA and glutamate synaptic activity at serotonin neurons in the rat dorsal raphe nucleus

The serotonin (5-hydroxytryptamine; 5-HT) system has a well-characterized role in depression. Recent reports describe comorbidities of mood-immune disorders, suggesting an immunological component may contribute to the pathogenesis of depression as well. Chemokines, immune proteins which mediate leukocyte trafficking, and their receptors are widely distributed in the brain, mediate neuronal patterning, and modulate various neuropathologies. The purpose of this study was to investigate the neuroanatomical relationship and functional impact of the chemokine stromal cell-derived factor-1alpha/CXCL12 and its receptor, CXCR4, on the serotonin dorsal raphe nucleus (DRN) system in the rat using anatomical and electrophysiological techniques. Immunohistochemical analysis indicates that over 70% of 5-HT neurons colocalize with CXCL12 and CXCR4. At a subcellular level, CXCL12 localizes throughout the cytoplasm whereas CXCR4 concentrates to the outer membrane and processes of 5-HT neurons. CXCL12 and CXCR4 also colocalize on individual DRN cells. Furthermore, electrophysiological studies demonstrate CXCL12 depolarization of 5-HT neurons indirectly via glutamate synaptic inputs. CXCL12 also enhances the frequency of spontaneous inhibitory and excitatory postsynaptic currents (sIPSC and sEPSC). CXCL12 concentration-dependently increases evoked IPSC amplitude and decreases evoked IPSC paired-pulse ratio selectively in 5-HT neurons, effects blocked by the CXCR4 antagonist AMD3100. These data indicate presynaptic enhancement of GABA and glutamate release at 5-HT DRN neurons by CXCL12. Immunohistochemical analysis further shows CXCR4 localization to DRN GABA neurons, providing an anatomical basis for CXCL12 effects on GABA release. Thus, CXCL12 indirectly modulates 5-HT neurotransmission via GABA and glutamate synaptic afferents. Future therapies targeting CXCL12 and other chemokines may treat serotonin related mood disorders, particularly depression experienced by immune-compromised individuals.

Prevascularization of cardiac patch on the omentum improves its therapeutic outcome

The recent progress made in the bioengineering of cardiac patches offers a new therapeutic modality for regenerating the myocardium after myocardial infarction (MI). We present here a strategy for the engineering of a cardiac patch with mature vasculature by heterotopic transplantation onto the omentum. The patch was constructed by seeding neonatal cardiac cells with a mixture of prosurvival and angiogenic factors into an alginate scaffold capable of factor binding and sustained release. After 48 h in culture, the patch was vascularized for 7 days on the omentum, then explanted and transplanted onto infarcted rat hearts, 7 days after MI induction. When evaluated 28 days later, the vascularized cardiac patch showed structural and electrical integration into host myocardium. Moreover, the vascularized patch induced thicker scars, prevented further dilatation of the chamber and ventricular dysfunction. Thus, our study provides evidence that grafting prevascularized cardiac patch into infarct can improve cardiac function after MI.

Chemokines and angiogenesis in rheumatoid arthritis

In rheumatoid arthritis, chemokines mediate the migration of inflammatory leukocytes into the synovium. Among the four known chemokine families, CXC, CC chemokines and fractalkine seem to be of outstanding importance in this process. Angiogenesis, the formation of new vessels, is also important during the perpetuation of inflammation underlying rheumatoid arthritis. In this review, authors discuss the role of the most important chemokines and chemokine receptors in arthritis-associated neovascularization. The process and regulation of angiogenesis are described in this context as well. Apart from discussing the pathogenic role of chemokines and chemokine receptors in arthritic vessel formation, authors also review the important relevance of chemokines and angiogenesis for therapeutic intervention.

Extracellular calcium increases CXCR4 expression on bone marrow-derived cells and enhances pro-angiogenesis therapy

Cell surface receptors play major roles in the mobilization and homing of progenitor cells from the bone marrow to peripheral tissues. CXCR4 is an important receptor that regulates homing of leucocytes and endothelial progenitors in response to the chemokine stromal cell-derived factor-1 (SDF-1). Ionic calcium is also known to regulate chemotaxis of selective bone marrow cells (BMCs) through the calcium-sensing receptor, CaR. Here we show that calcium regulates CXCR4 expression and BMC responses to SDF-1. CaCl₂ treatment of BMC induced a time- and dose-dependent increase in both the transcription and cell surface expression of CXCR4. BMC subpopulations expressing VEGFR2⁺, CD34⁺ and cKit⁺/Sca-1⁺ were especially sensitive to calcium. The effects were blocked by calcium influx inhibitors, anti-CaR antibody and the protein synthesis inhibitor cycloheximide, but not by the CXCR4 antagonist AMD3100. Calcium treatment also enhanced SDF-1-mediated CXCR4 internalization. These changes were reflected in significantly improved chemotaxis by SDF-1, which was abolished by AMD3100 and by antibody against CXCR4. Calcium pre-treatment improved homing of CD34⁺ BMCs to ischemic muscle in vivo, and enhanced revascularization in ischemic mouse hindlimbs. Our results identify calcium as a positive regulator of CXCR4 expression that promotes stem cell mobilization, homing and therapy.

A novel CXCR4 antagonist derived from human SDF-1beta enhances angiogenesis in ischaemic mice

AIMS

The effects on angiogenesis of a novel CXC chemokine receptor 4 (CXCR4) antagonist, SDF-1betaP2G, derived from human stromal cell-derived factor-1beta (SDF-1beta), were examined in a model of hind limb ischaemia in mice.

METHODS AND RESULTS

The antagonistic activities of SDF-1betaP2G against CXCR4 were evaluated in vitro and in vivo and compared with phosphate-buffered saline and AMD3100 (a small bicyclam antagonist of SDF-1). Angiogenesis, muscle regeneration and the expression of pro-angiogenic factors were evaluated in ischaemic gastrocnemius muscles. Distant toxic effects of SDF-1betaP2G were evaluated by inflammatory and apoptotic markers. SDF-1betaP2G induced CXCR4 internalization and competitively inhibited the chemotaxis of SDF-1beta but did not mediate migration, calcium influx, or the phosphorylation of Akt and extracellular signal-regulated kinase in cultured T-lymphoblastic leukaemia cells or H9C2 cells. SDF-1betaP2G enhanced blood flow, angiogenesis, and muscle regeneration in ischaemic hind limbs, and the enhancement was significantly better than that of AMD3100. Markers of angiogenesis and progenitor cell migration, including phosphorylated Akt, vascular endothelial growth factor (VEGF), SDF-1 and CXCR4, were up-regulated by SDF-1betaP2G and co-localized with CD31-positive cells. Neutralization of VEGF with its specific antibody abolished SDF-1betaP2G-induced blood reperfusion and angiogenesis. No apparent inflammatory and apoptotic effects were found in heart, liver, kidneys, and testes after SDF-1betaP2G administration.

CONCLUSION

Our findings indicate that the novel CXCR4 antagonist, SDF-1betaP2G, can efficiently enhance ischaemic angiogenesis, blood flow restoration, and muscle regeneration without apparent adverse effects, most likely through a VEGF-dependent pathway.

Effect of L-arginine on circulating endothelial progenitor cells in hypercholesterolemic rabbits

The cardiovascular disease risk factors result in endothelial cells apoptosis and injury. Recently, endothelial progenitor cells (EPCs) have been shown to participate in ongoing endothelial repair. Nitric Oxide (NO) is essential for mobilization and functional activity of EPCs. We hypothesized that L-arginine (NO precursor) supplementation may increase EPCs number in hypercholesterolemic rabbits. EPCs, plasma levels of nitrite, von Willebrand Factor (vWF) and Intima-Media thickness ratio were determined in rabbits feeding high-cholesterol diet or high-cholesterol diet with L-arginine(3% in drinking water). L-arginine supplementation had a significant effect on the nitrite levels, and EPC numbers, and inhibited vWF increment and atherosclerosis progression (p<0.05). Our results suggest that the beneficial effect of L-arginine in prevention of atherosclerosis may be due to the modulation of EPC levels.

Effects of intramyocardial injection of platelet-rich plasma on the healing process after myocardial infarction

OBJECTIVE

Platelet activation and subsequent release of granules containing a variety of growth factors, at the site of injury, is crucial for the wound healing process. We postulated that a platelet-mediated paracrine effect may accelerate the healing process after myocardial infarction.

METHODS

Allogenic platelet-rich and platelet-poor plasma (PRP and PPP) were collected from 15 healthy male Wistar rats. After thrombin activation, the level of vascular endothelial growth factor (VEGF) in PRP and PPP was measured by enzyme-linked immunosorbent assay. A rat model of myocardial infarction was induced by permanent ligation of the left anterior descending artery, and thrombin-activated PRP and PPP, respectively, were injected into the ischemic region. Seven days and 28 days after operation, surviving rats were killed. Ex-vivo left ventricular pressure-volume relationship was performed to evaluate passive diastolic function. Collagen analysis was performed by picrosirius red staining plus polarized microscopy. Angiogenesis and arteriogenesis were evaluated by immunofluorescent staining.

RESULTS

After thrombin activation, VEGF level in PRP was significantly higher than that in PPP (187.5+/-45.5 vs. 30.1+/-7.8 pg/ml, P<0.01). Injection of thrombin-activated PRP into the infarcted area resulted in improvement of ventricular remodeling and accelerated healing, as demonstrated by limitation of ventricular expansion, attenuation of myocardial hypertrophy in the noninfarct region, facilitation of angiogenesis and arteriogenesis in the infarct.

CONCLUSION

Injection of thrombin-activated PRP could modulate favorably the postinfarction remodeling process. Platelet-released VEGF may participate in this protective effect.

Biofunctionalization of biomaterials for accelerated in situ endothelialization: a review

The higher patency rates of cardiovascular implants, including vascular bypass grafts, stents, and heart valves are related to their ability to inhibit thrombosis, intimal hyperplasia, and calcification. In native tissue, the endothelium plays a major role in inhibiting these processes. Various bioengineering research strategies thereby aspire to induce endothelialization of graft surfaces either prior to implantation or by accelerating in situ graft endothelialization. This article reviews potential bioresponsive molecular components that can be incorporated into (and/or released from) biomaterial surfaces to obtain accelerated in situ endothelialization of vascular grafts. These molecules could promote in situ endothelialization by the mobilization of endothelial progenitor cells (EPC) from the bone marrow, encouraging cell-specific adhesion (endothelial cells (EC) and/or EPC) to the graft and, once attached, by controlling the proliferation and differentiation of these cells. EC and EPC interactions with the extracellular matrix continue to be a principal source of inspiration for material biofunctionalization, and therefore, the latest developments in understanding these interactions will be discussed.

Multiple circulating proangiogenic factors induced by sunitinib malate are tumor-independent and correlate with antitumor efficacy

Cancer patients treated with antiangiogenic multitargeted receptor tyrosine kinase (RTK) inhibitors show increased levels of plasma VEGF and placental growth factor and decreased levels of soluble VEGF receptor-2, thus implicating these overall changes as a possible class effect of such drugs and raising the possibility of their exploitation as surrogate biomarkers for pharmacodynamic drug activity/exposure and patient benefit. A postulated mechanism for these changes is that they are tumor-dependent, resulting from drug-induced decreases in vascular function, increases in tumor hypoxia, and changes in hypoxia-regulated genes. However, here we report that an identical pattern of change is observed in normal nontumor-bearing mice treated with SU11248/sunitinib, a small-molecule inhibitor of VEGF and PDGF RTKs. The changes were dose-dependent, plateaued after 4 days of consecutive treatment, reversed after discontinuation of therapy, and correlated with antitumor activity. Altered protein expression was found in a broad variety of tissues, and dose-dependent elevations were observed of several plasma proteins previously unassociated with this class of inhibitor, including G-CSF, SDF-1alpha, SCF, and osteopontin. Our results suggest that observed sunitinib-induced molecular plasma changes, including those both directly and indirectly targeted by drug, represent a systemic tumor-independent response to therapy and may correlate with the most efficacious antitumor doses, potentially having utility for defining the optimal biologic dose range for this drug class but not as predictive markers of tumor response or clinical benefit. They may also be relevant to drug-associated toxicities, drug resistance, and observed rapid tumor (re)growth seen after cessation of therapy.