Neovascularization Of Ischemic Tissue Research Articles

Circulating Endothelial Progenitor Cells, C-Reactive Protein and Severity of Coronary Stenosis in Chinese Patients with Coronary Artery Disease

We sought to investigate whether numbers and activity of circulating endothelial progenitor cells (EPCs) correlate with severity of coronary stenosis as well as cardiovascular risk factors in patients with stable coronary artery disease (CAD). Number of circulating EPCs was analyzed in 104 consecutive patients with proven or clinically suspected CAD. Adhesive and migratory activity was also determined. The number of EPCs was lower in patients with a single diseased coronary artery (Group II, n=35, p<0.05 vs. Group I) or multiple diseased arteries (Group III, n=25, p<0.01 vs. Group I, p<0.05 vs. Group II) compared to those with normal coronary arteries (Group I, n=44). The number of EPCs was also related with angiographic Gensini score (r=-0.355, p=0.006). In addition, concentrations of C-reactive protein (CRP) were elevated in patients with CAD, and positively correlated with Gensini score (r=0.476, p=0.001). As for the risk factors, the number of EPCs was also inversely correlated with age (p=0.001), high sensitivity-CRP (p=0.012), hypertension (p=0.042) and family history of CAD (p=0.043). Most importantly, the migratory capacity of EPCs was compromised in patients with CAD, and inversely correlated with the angiographic Gensini score (r=-0.315, p=0.021). EPCs isolated from patients with CAD also showed an impaired adhesive activity (p<0.05). In conclusion, in patients with stable CAD, reduction in the number and impairment in the function of circulating EPCs were correlated with the severity of coronary stenosis. CRP may play an important role in reducing the number of EPCs and accelerating atherosclerosis. Given the important role of EPCs in neovascularization of ischemic tissue, a decrease in the number and activity of EPCs may contribute to the impaired vascularization in patients with CAD.

Structural Localization and Expression of CXCL12 and CXCR4 in Rat Heart and Isolated Cardiac Myocytes

CXCL12 (SDF-1), which binds CXCR4, is involved in several physiological and pathophysiological processes. In heart, this axis seems to play a key role in cardiogenesis and is involved in the neovascularization of ischemic tissues. Rats have three known CXCL12 mRNA isoforms, of which only alpha and gamma are present in the normal heart. However, little is known about CXCL12 protein expression and localization. We investigated the pattern of protein expression and the localization of both CXCR4 and CXCL12 in the heart, using isolated cardiomyocytes and a rat myocardial infarction model. Western blots showed that cardiomyocytes contained a specific 67-kDa CXCR4 isoform and a 12-kDa CXCL12 isoform. Confocal and electron microscopy clearly showed that CXCR4 was present at the plasmalemma and CXCL12 in continuity of the Z-line, in the proximal part of T-tubules. In conclusion, we provide the first description of the expression and fine localization of CXCR4 and CXCL12 proteins in normal rat heart and cardiomyocytes. These results suggest that the CXCL12/CXCR4 axis may be involved in cardiomyocyte calcium homeostasis regulation. Our work and the well-known chemoattraction properties of the CXCL12/CXCR4 axis highlight the importance of deciphering the function of this axis in both normal and pathological hearts.

Recombinant human granulocyte–colony‐stimulating factor–mobilized and apheresis‐collected endothelial progenitor cells: a novel blood cell component for therapeutic vasculogenesis

Endothelial progenitor cells (EPCs) have been identified among hematopoietic tissue-derived progenitor cells that are mobilized into the peripheral blood (PB) as a result of tissue injury. It therefore seems likely that circulating EPCs have therapeutic potential by aiding in the neovascularization of ischemic tissue. This study provides clinical data on the availability of circulating EPCs at steady state and after recombinant human granulocyte-colony-stimulating factor (rHuG-CSF) mobilization and their collection by leukapheresis. Eight healthy donors underwent rHuG-CSF treatment over 4 days, followed by leukapheresis. Blood samples taken before rHuG-CSF treatment and before apheresis as well as apheresis-collected samples were analyzed by flow cytometry and by real time reverse transcription-polymerase chain reaction for cells expressing EPC-specific surface markers and tissue markers, respectively, and for EPC colony-forming cells. The median PB concentration of CD34+133+ vascular endothelial growth factor receptor-2 (VEGFR-2)-+ EPCs increased 8-fold from steady state to mobilized, and the concentration of CD34+133-VEGFR-2+ EPCs increased by 10-fold. This mobilization pattern was similar to that of hematopoietic CD34+, CD133+, and CD34+117+ progenitor cells. The increase in the median circulating colony-forming unit EPC concentration was 10-fold over baseline. The median absolute number of CD34+133+VEGFR-2+ cells collected by large-volume leukapheresis was 0.8 x 10(6) per kg of body weight. In addition, a small subset of immature CD133+34- cells coexpressing VEGFR-2 was identified in mobilized PB and in the apheresis collection. EPC-specific cells contained in the apheresis product were also identified as expressing mRNA for the CD31 antigen, Tie-2, and VEGFR-2. Circulating EPCs represent a novel blood cell component that can be collected by apheresis in large quantities and can be used clinically, either unmanipulated or EPC-selected, for therapeutic vasculogenesis.

Identification of Sokotrasterol Sulfate As a Novel Proangiogenic Steroid

The potential to promote neovascularization in ischemic tissues using exogenous agents has become an exciting area of therapeutics. In an attempt to identify novel small molecules with angiogenesis promoting activity, we screened a library of natural products and identified a sulfated steroid, sokotrasterol sulfate, that induces angiogenesis in vitro and in vivo. We show that sokotrasterol sulfate promotes endothelial sprouting in vitro, new blood vessel formation on the chick chorioallantoic membrane, and accelerates angiogenesis and reperfusion in a mouse hindlimb ischemia model. We demonstrate that sulfation of the steroid is critical for promoting angiogenesis, as the desulfated steroid exhibited no endothelial sprouting activity. We thus developed a chemically synthesized sokotrasterol sulfate analog, 2beta,3alpha,6alpha-cholestanetrisulfate, that demonstrated equivalent activity in the hindlimb ischemia model and resulted in the generation of stable vessels that persisted following cessation of therapy. The function of sokotrasterol sulfate was dependent on cyclooxygenase-2 activity and vascular endothelial growth factor induction, as inhibition of either cyclooxygenase-2 or vascular endothelial growth factor blocked angiogenesis. Surface expression of alpha(v)beta(3) integrin was also necessary for function, as neutralization of alpha(v)beta(3) integrin, but not beta(1) integrin, binding abrogated endothelial sprouting and antiapoptotic activity in response to sokotrasterol sulfate. Our findings indicate that sokotrasterol sulfate and its analogs can promote angiogenesis in vitro and in vivo and could potentially be used for promoting neovascularization to relieve the sequelae of vasoocclusive diseases.

Oxidative Stress on Progenitor and Stem Cells in Cardiovascular Diseases

There is accumulating evidence that reactive oxygen species (ROS) play major roles in the initiation and progression of cardiovascular dysfunction associated with diseases such as hyperlipidemia, diabetes mellitus, hypertension, ischemic heart disease, and chronic heart failure. ROS produced by migrating inflammatory cells as well as vascular cells (endothelial cells, vascular smooth muscle cells, and adventitial fibroblasts) have distinct functional effects on each cell type. These effects include cell growth, apoptosis, migration, inflammatory gene expression and matrix regulation. ROS, through regulating vascular cell function, can play a central role in normal vascular physiology, and contribute substantially to the development of cardiovascular diseases. Excessive production of ROS is an essential mechanism underlying the pathogenesis of endothelial dysfunction and cardiovascular disease. Stem cells hold great promise for tissue repair and regenerative medicine, and endothelial progenitor cells (EPC) play a significant role in neovascularization of ischemic tissue. Recent studies have shown that cardiovascular risk factors such as hypertension, hypercholesterolemia, diabetes and cigarette smoking are inversely correlated with EPC number and function. Understanding the mechanisms, that regulate EPC function may provide new insights into the pathogenesis of vasculogenesis and may promote development of specific therapies to prevent ROS production and ultimately correct EPC dysfunction. We have demonstrated the angiotensin II receptor blockers improve EPC dysfunction through antioxidative mechanisms. In the present review, we describe our current understanding of the contributions of oxidative stress to progenitor and stem cell dysfunction in cardiovascular disease and focus on the potential mechanisms that underlie oxidative stress-induced damage of progenitor and stem cells.

Critical Roles of Muscle-Secreted Angiogenic Factors in Therapeutic Neovascularization

The discovery of bone marrow-derived endothelial progenitors in the peripheral blood has promoted intensive studies on the potential of cell therapy for various human diseases. Accumulating evidence has suggested that implantation of bone marrow mononuclear cells effectively promotes neovascularization in ischemic tissues. It has also been reported that the implanted cells are incorporated not only into the newly formed vessels but also secrete angiogenic factors. However, the mechanism by which cell therapy improves tissue ischemia remains obscure. We enrolled 29 "no-option" patients with critical limb ischemia and treated ischemic limbs by implantation of peripheral mononuclear cells. Cell therapy using peripheral mononuclear cells was very effective for the treatment of limb ischemia, and its efficacy was associated with increases in the plasma levels of angiogenic factors, in particular interleukin-1beta (IL-1beta). We then examined an experimental model of limb ischemia using IL-1beta-deficient mice. Implantation of IL-1beta-deficient mononuclear cells improved tissue ischemia as efficiently as that of wild-type cells. Both wild-type and IL-1beta-deficient mononuclear cells increased expression of IL-1beta and thus induced angiogenic factors in muscle cells of ischemic limbs to a similar extent. In contrast, inability of muscle cells to secrete IL-1beta markedly reduces induction of angiogenic factors and impairs neovascularization by cell implantation. Implanted cells do not secret angiogenic factors sufficient for neovascularization but, instead, stimulate muscle cells to produce angiogenic factors, thereby promoting neovascularization in ischemic tissues. Further studies will allow us to develop more effective treatments for ischemic vascular disease.

LFA-1 and VLA-4 involved in human high proliferative potentialendothelial progenitor cells homing to ischemic tissue

Cumulative evidences have revealed that endothelial progenitor cell (EPC) transplantation can promote the neovascularization in ischemic tissue, but the mechanism of EPCs homing to the site of ischemia is poorly understood. In this study, to investigate the mechanism of human umbilical cord blood-derived high proliferative potential-endothelial progenitor cells (HPP-EPCs) homing to ischemic tissue we evaluated the expression of lymphocyte function-associated antigen-1 (LFA-1, or CD11a/CD18) and very late antigen-4 (VLA-4, or CD49d/CD29) in EPCs and the changes of expression level of their ligands, intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1), in ischemic tissue and performed the adhesion and migration assays to analyze the interaction between the receptors and ligands. Furthermore, we studied the roles of LFA-1 and VLA-4 in EPC homing in an ischemic model of mice. The results show that LFA-1 andVLA-4 were expressed in HPPEPCs and ICAM-1 and VCAM-1 were expressed in vessel endothelium in ischemic tissues. The pre-incubation of HPP-EPCs with neutralizing antibodies against CD11a or CD49d reduced adhesion and migration of HPP-EPCs in vitro and reduced recovery of hind-limb blood flow, capillary density and incorporation of HPP-EPC into ischemic tissues in vivo. Furthermore, the pre-incubation of HPP-EPCs with the combination of CD11a and CD49d antibodies led to synergistically negative effects on adhesion and transmigration of HPP-EPCs in vitro, and on the homing of HPP-EPCs to ischemic tissue and on neovascularization capacity in vivo. These results indicate that LFA-1 andVLA-4 are involved in HPP-EPC homing to ischemic tissues.

RhG-CSF Mobilized and Apheresis-Collected Endothelial Progenitor Cells for Therapeutic Vasculogenesis.

Endothelial progenitor cells (EPCs) have been identified as part of hematopoietic tissue-derived progenitor cells that are mobilized into the peripheral blood (PB) as a result of tissue injury. It therefore seems likely that circulating EPCs have therapeutic potential by aiding in the neovascularization of ischemic tissue. It was the purpose of this study to provide clinical data on the availability of circulating EPCs at steady-state and after rhG-CSF mobilization, and their collection by leukapheresis. Eight healthy donors underwent rhG-CSF (10 μg/kg) treatment over 4 days. Continuous-flow leukapheresis (COBE Spectra, Version 4.7) was performed on the fourth day of rhG-CSF treatment. Blood samples were drawn before starting rhG-CSF treatment, before apheresis, and from the apheresis collection bag. The total cell numbers collected per apheresis were based on processing a median of 17 L [10.7–20.1] blood volume or approximately three times the donor's total blood volume. Blood and apheresis samples were analyzed by flow cytometry for EPC surface markers CD34, CD133, VEGFR-2, and by forming EPC colonies (CFU-EPC). The Wilcoxon matched-pairs signed-ranks test was used to compare the distributions at various sampling points.All CD133 subsets were CD14 negative to exclude differentiated monocytes or macrophages. The median steady-state PB concentrations of circulating CD34+CD133+VEGFR-2+ cells was 0.9/μl [0–3], or 1.7/μl [0.9–4] for CD34+133−VEGFR-2+ EPCs. After 4 days of rhG-CSF mobilization treatment the PB CD34+CD133+VEGFR-2+ subset concentration increased by a median of 8-fold [p 0.01], and the CD34+133−VEGFR-2+ subset concentration by a median of 10-fold [p 0.01] over baseline. The median PB concentration of circulating CFU-EPCs increased by 10-fold [p 0.02]. The median absolute number of CD34+CD133+VEGFR-2+ and CD34+CD133-VEGFR-2+ cells collected by leukapheresis per kg of body weight was 0.845 x 106 [0.12–2.55] and 1.54 x 106 [0.06–2.4], respectively. A small population of CD133+34− VEGFR-2+ cells was identified in steady state and mobilized PB, and in the apheresis collect (0.11 x 106/kg [0–0.26]). CD34− progenitor cells expressing CD133 are believed to represent a primitive progenitor cell population containing SCID-repopulating cells. VEGFR-2 coexpression of those immature cells may define a circulating cell population that contributes to vasculogenesis.Our data suggest that clonogenic circulating EPCs can be mobilized by rhG-CSF and collected by continuous-flow leukapheresis generating large numbers of EPCs, specifically in the range of 60 x 106 EPCs per leukapheresis procedure for a 70 kg individual. Circulating EPCs represent a novel blood cell component that can be clinically used in large quantities, either unmanipulated or EPC-selected, for therapeutic vasculogenesis.

How to Explain the Differences Between Renin Angiotensin System Modulators

Angiotensin II (Ang II) plays important roles in the development of cardiovascular diseases including hypertension, renal diseases, cardiac hypertrophy, congestive heart failure, and ischemic heart disease. Angiotensin II exerts classic hemodynamic and renal effects, but it is also a local biologically active mediator with direct effects on endothelial and smooth muscle cells. Two subtypes of Ang II receptors, type 1 (AT(1)) and type 2 (AT(2)), have been identified. Their roles have been investigated in depth in vivo and in vitro, although few data are available concerning the role of the AT(2) receptors in the adult circulation in humans. The two receptors, both of which belong to the superfamily of G-protein-coupled receptors, have different signaling pathways and different functions. The AT(1) receptor subtype is expressed ubiquitously and is involved in most of the well-known biological functions of Ang II. The AT(1) receptor transactivates growth pathways and mediates major Ang II effects such as vasoconstriction, increased cardiac contractility, renal tubular sodium reabsorption, cell proliferation, vascular and cardiac hypertrophy, inflammatory responses, and oxidative stress. In contrast to AT(1), the physiologic role of AT(2) receptors has long remained an enigma. The AT(2) receptors are highly expressed in fetal tissues, although their expression dramatically decreases after birth, being restricted to a few organs, including the cardiovascular system. The AT(2) receptor is re-expressed in the adult animal after cardiac and vascular injury and during wound healing, suggesting a role for this receptor in tissue remodeling, growth, or development. Recent and concordant data suggested that overstimulation of AT(2) receptors might be implied in cardiac and vascular hypertrophic processes. Both Ang II receptors are involved in hypoxia-induced neovascularization. A large set of experimental evidence suggests that activation of the AT(1) receptor results in proangiogenic effects, whereas AT(2) receptors mediate apoptosis and thus antiangiogenic effects. Furthermore, bradykinin through its B(1) or B(2) receptors is a potent activator of experimental hypoxia-induced neovascularization. Thus, pharmacologic blockade of the AT(1) receptor and resulting overactivation of AT(2) receptors could impair or delay neovascularization in ischemic tissues in patients receiving chronic treatment with angiotensin receptor blockers. In contrast, increased tissue bradykinin resulting from inhibition of converting enzyme could help to restore functional vascularization in ischemic tissues. These basic concepts deserve a second reading and reevaluation to discuss differences in vascular protection in large clinical trials with different classes of drugs acting on the renin-angiotensin system.

Therapeutic Potential of Endothelial Progenitor Cells in Cardiovascular Diseases

Endothelial dysfunction and cell loss are prominent features in cardiovascular disease. Endothelial progenitor cells (EPCs) originating from the bone marrow play a significant role in neovascularization of ischemic tissues and in re-endothelialization of injured blood vessels. Several studies have shown the therapeutic potential of EPC transplantation in rescue of tissue ischemia and in repair of blood vessels and bioengineering of prosthetic grafts. Recent small-scale trials have provided preliminary evidence of feasibility, safety, and efficacy in patients with myocardial and critical limb ischemia. However, several studies have shown that age and cardiovascular disease risk factors reduce the availability of circulating EPCs (CEPCs) and impair their function to varying degrees. In addition, the relative scarcity of CEPCs limits the ability to expand these cells in sufficient numbers for some therapeutic applications. Priority must be given to the development of strategies to enhance the number and improve the function of CEPCs. Furthermore, alternative sources of EPC such as chord blood need to be explored. Strategies for improvement of cell adhesion, survival, and prevention of cell senescence are also essential to ensure therapeutic viability. Genetic engineering of EPCs may be a useful approach to developing these cells into efficient therapeutic tools. In the clinical arena there is pressing need to standardize the protocols for isolation, culture, and therapeutic application of EPC. Large-scale multi-center randomized trials are required to evaluate the long-term safety and efficacy of EPC therapy. Despite these hurdles, the outlook for EPC-based therapy for cardiovascular disease is promising.

Granulocyte-Colony Stimulating Factor Augments Neovascularization Induced by Bone Marrow Transplantation in Rat Hindlimb Ischemia

Because granulocyte-colony stimulating factor (G-CSF) mobilizes bone marrow cells including endothelial progenitor cells, we examined whether G-CSF augments angiogenesis and collateral vessel formation induced by bone marrow-mononuclear cells transplantation (BMT). Unilateral hindlimb ischemia was surgically induced in Lewis rats. One week after surgery, administration of 100 mg/kg per day G-CSF significantly increased the laser Doppler blood perfusion index (LDBPI), number of angiographically detectable collateral vessels (angiographic score), and capillary density determined by alkaline phosphatase staining. In the BMT group (1 × 107 cells/rat) and the group with combined G-CSF treatment and BMT, LDBPI was significantly increased compared with that in the vehicle-treated group. In the BMT group, neovascularization was significantly increased as evidenced by the angiographic score and capillary density compared with the vehicle-treated group. Furthermore, the combination of G-CSF treatment and BMT augmented neovascularization compared with BMT alone, as evidenced by the angiographic score and capillary density. Moreover, G-CSF significantly increased vascular endothelial growth factor mRNA and fibroblast growth factor-2 mRNA in hindlimb muscle. In conclusion, G-CSF was found to augment neovascularization in rat hindlimb ischemia. Combined use of G-CSF treatment and BMT may be a useful strategy for therapeutic neovascularization in ischemic tissues.

Implantation of bone marrow mononuclear cells using injectable fibrin matrix enhances neovascularization in infarcted myocardium

Neovascularization may improve cardiac function and prevent further scar tissue formation in infarcted myocardium. A number of studies have demonstrated that bone marrow-derived cells have the potential to induce neovascularization in ischemic tissues. In this study, we hypothesized that implantation of bone marrow mononuclear cells (BMMNCs) using injectable fibrin matrix further enhances neovascularization in infarcted myocardium compared to BMMNC implantation without matrix. To test this hypothesis, infarction was induced in rat myocardium by cryoinjury. Three weeks later, rat BMMNCs were mixed with fibrin matrix and injected into the infarcted myocardium. Injection of either BMMNCs or medium alone into infarcted myocardium served as controls. Eight weeks after the treatments, histological analyses indicated that implantation of BMMNCs using fibrin matrix resulted in more extensive tissue regeneration in the infarcted myocardium compared to BMMNC implantation without matrix. Examination with fluorescence microscopy revealed that cells labeled with a fluorescent dye prior to implantation survived in the infarcted myocardium at 8 weeks of implantation. Importantly, implantation of BMMNCs using fibrin matrix resulted in much more extensive neovascularization in infarcted myocardium than BMMNC implantation without matrix. The microvessel density in infarcted myocardium was significantly higher ( p<0.05) when BMMNCs were implanted using fibrin matrix (350±22 microvessels/mm 2) compared to BMMNC implantation without matrix (262±13 microvessels/mm 2) and medium injection (76±9 microvessels/mm 2). In addition, average internal diameter of microvessels was significantly larger ( p<0.05) in BMMNC implantation with fibrin matrix group (14.6±1.2 μm) than BMMNC implantation without matrix group (10.2±0.7 μm) and medium injection group (7.3±0.5 μm). These results suggest that fibrin matrix could serve as a cell implantation matrix that enhances neovascularization efficacy for myocardial infarction treatment.

Ex vivo differentiated endothelial and smooth muscle cells from human cord blood progenitors home to the angiogenic tumor vasculature.

Recent studies have provided increasing evidence that postnatal neovascularization does not rely exclusively on sprouting of preexisting vessels, but also involves bone marrow-derived circulating endothelial precursors (BM-EPCs). Animal studies revealed that neovascularization of ischemic tissue can be enhanced by BM-EPCs transplantation. But a possible limitation to the use of vascular precursors for therapeutic angiogenesis is the relatively low number of these cells. In this study, we demonstrate that ex vivo expanded differentiated endothelial cells (ECs) and smooth muscle cells (SMCs), may home to the tumor vasculature allowing targeting of transgene expression to the neoangiogenic site. Mononuclear cells (MNCs) or CD34+ -enriched cells were purified from cord blood. We have defined culture conditions in which we observed two types of clones easily differentiated according to their morphology: cobblestone or spindle-shaped. Phenotypic characterization was assessed by immunocytochemistry, flow cytometry analysis and polymerase reaction with reverse transcription. Formation of capillary-like network in vitro was studied in three-dimensional collagen culture. And recruitment of these cells to a tumoral neoangiogenic site was assessed into tumor-bearing Severe Combined Immunodeficient (SCID) mouse model. The cobblestone cells uniformly positive for CD31, VE-cadherin, vWF, VEGF R1 and R2, ecNOS and incorporating acetylated LDL were ECs. Spindle-shaped cells expressed alpha-smooth muscle actin (alpha-SMA), Smooth Muscle Heavy Chain (SMHC), SM22 and calponin. They also displayed a carbachol-induced contractility in a medium containing IGF1. So we concluded that spindle-shaped cells were SMCs. ECs and SMCs interacted with each other to form a capillary like network in three-dimensional type I collagen culture. Moreover, these ex vivo differentiated cells are able to home to the tumor vasculature. We provide evidence that progenitors for ECs and SMCs circulate in human cord blood and differentiate into functional ECs and SMCs. These differentiated cells could provide a biomaterial for vascular cell therapy, because of their homing capacity to the neovascularization site.

Plasticity of human adipose lineage cells toward endothelial cells: physiological and therapeutic perspectives.

Adipose tissue development and remodeling are closely associated with the growth of vascular network. We hypothesized that adipose tissue may contain progenitor cells with angiogenic potential and that therapy based on adipose tissue-derived progenitor cells administration may constitute a promising cell therapy in patients with ischemic disease. In mice, cultured stromal-vascular fraction (SVF) cells from adipose tissue have a great proangiogenic potential, comparable to that of bone marrow mononuclear cells in the mouse ischemic hindlimb model. Similarly, cultured human SVF cells differentiate into endothelial cells, incorporate into vessels, and promote both postischemic neovascularization in nude mice and vessel-like structure formation in Matrigel plug. In vitro, these cells represent a homogeneous population of CD34- and CD13-positive cells, which can spontaneously express the endothelial cell markers CD31 and von Willebrand factor when cultured in semisolid medium. Interestingly, dedifferentiated mature human adipocytes have the potential to rapidly acquire the endothelial phenotype in vitro and to promote neovascularization in ischemic tissue and vessel-like structure formation in Matrigel plug, suggesting that cells of endothelial and adipocyte phenotypes may have a common precursor. This study demonstrates, for the first time, that adipocytes and endothelial cells have a common progenitor. Such adipose lineage cells participate in vascular-like structure formation in Matrigel plug and enhance the neovascularization reaction in ischemic tissue. These results also highlight the concept that adipose lineage cells represent a suitable new cell source for therapeutic angiogenesis in ischemic disease.

Neovascularization of ischemic tissues by gene delivery of the extracellular matrix protein Del-1

Neovascularization of ischemic tissues by gene delivery of the extracellular matrix protein Del-1

Neovascularization of ischemic tissues by gene delivery of the extracellular matrix protein Del-1.

The ECM protein Del-1 is one of several novel ECM proteins that accumulate around angiogenic blood vessels in embryonic and tumor tissue and promote angiogenesis in the absence of exogenous growth factors. Del-1 expressed in mouse or rabbit ischemic hind-limb muscle by gene transfer rapidly promotes new blood vessel formation and restores muscle function. This angiogenic ECM protein initiates angiogenesis by binding to integrin alphavbeta5 on resting endothelium, thereby resulting in expression of the transcription factor Hox D3 and integrin alphavbeta3. Hox D3 converts resting endothelium to angiogenic endothelium by inducing expression of proangiogenic molecules such as integrin alphavbeta3. These findings provide evidence for an angiogenic switch that can be initiated in the absence of exogenous growth factors and indicate that the angiogenic matrix protein Del-1 may be a useful tool for the therapy of ischemic disease.

Adenoviral VEGF-A gene transfer induces angiogenesis and promotes bone formation in healing osseous tissues.

Vascular endothelial growth factor (VEGF) is a key regulator of angiogenesis. VEGF has been safely and efficiently applied to stimulate neovascularization in ischemic tissues in atherosclerotic patients. VEGF has an important role in bone repair by promoting angiogenesis and by stimulating major skeletal cell populations, chondrocytes, osteoblasts and osteoclasts. We studied the effect of VEGF-A on the recovery of bone drilling defects in rat femur delivered with first-generation adenoviral vector. The virus was injected into the muscle layer surrounding the bone defect made by drilling and the healing was followed for 1, 2, and 4 weeks. The VEGF effect was first demonstrated with an increased number of FVIII-related antigen-positive blood vessels in the defect area 1 week after the procedure. The proportional area of remaining reparative tissue was significantly reduced in the VEGF-treated animals 2 weeks after the injury suggesting favorable effect on bone healing. Increased periosteal cartilage was seen at the early phases of healing suggesting endochondral ossification. VEGF overexpression, however, completed the endochondral phase earlier compared with the control condition. Bone mineral content was enhanced in the VEGF-treated femurs measured with peripheral quantitative computed tomography at a 2-week time point. Our data confirm the important role of VEGF in bone healing. We show for the first time that adenoviral VEGF-A gene transfer may modify bone defect healing in a rodent model.

Effect of intrahepatic omental implantation on angiogenesis in rat liver with hepatic artery ligation.

Despite early surgical intervention, the results of treating hepatic artery thrombosis remain poor. The use of omental flaps is well documented for its angiogenic potential in promoting neovascularization in ischemic tissues. This experimental study evaluated the formation of new blood-vessels after omental implantation (OI) in rats after ligation of the hepatic artery. Wistar rats were used and divided into the following groups: I OI with HAL, II OI without HAL, III hepatic artery ligation (HAL). For angiography, measurements were made of liver tissue blood flow by the laser Doppler method and of hepatic artery flow by the colored microsphere method (CMS), and immunohistochemical study was done for vascular endothelial growth factor (VEGF). The rats were killed at 1, 3, 7 or 30 days after laparotomy. Relative arterial hepatic blood flow in the implanted lobe of group I, as determined by CMS, reached 50% of control values 7 days after surgery. Angiography and microscopic studies of the excised liver revealed distinct angiogenesis surrounding the omental implant in the liver for 7 days postoperatively. The formation of new blood-vessels after OI was not observed in livers without HAL. Omental implantation appears to be useful in preventing organ anoxia after hepatic artery thrombosis.

Augmentation of postnatal neovascularization with autologous bone marrow transplantation.

Endothelial progenitor cells (EPCs) have been identified in adult human peripheral blood. Because circulating EPCs should originate from bone marrow (BM), we examined whether BM mononuclear cells (BM-MNCs) can give rise to functional EPCs and whether transplantation of autologous BM-MNCs might augment angiogenesis and collateral vessel formation in a rabbit model of hindlimb ischemia. Rabbit BM-MNCs were isolated by centrifugation through a Histopaque density gradient and cultured on fibronectin. EPCs developed from BM-MNCs in vitro, as assessed by acetylated LDL incorporation, nitric oxide (NO) release, and expression of von Willebrand factor and lectin binding. Unilateral hindlimb ischemia was surgically induced in rabbits (n=8), and fluorescence-labeled autologous BM-MNCs were transplanted into the ischemic tissues. Two weeks after transplantation, fluorescence microscopy revealed that transplanted cells were incorporated into the capillary network among preserved skeletal myocytes. In contrast, transplanted autologous BM-fibroblasts did not participate in EC capillary network formation (n=5). Then, in an additional 27 rabbits, saline (control; n=8), autologous BM-MNCs (n=13; 6.9+/-2.2x10(6) cells/animal), or BM-fibroblasts (n=6; 6.5+/-1.5x10(6) cells/animal) were injected into the ischemic tissues at postoperative day 7. Four weeks after transplantation, the BM-MNC-transplanted group had more angiographically detectable collateral vessels (angiographic score: 1.5+/-0.34 versus 0.94+/-0.26 and 1.1+/-0.14; P:<0.05), a higher capillary density (23+/-5.8 versus 10+/-1.9 and 11+/-0.8 per field; P:<0.001), and a greater laser Doppler blood perfusion index (505+/-155 versus 361+/-35 and 358+/-22 U; P:<0.05) than the control and BM-fibroblast-transplanted groups. Direct local transplantation of autologous BM-MNCs seems to be a useful strategy for therapeutic neovascularization in ischemic tissues in adults, consistent with "therapeutic vasculogenesis."

Adenovirus-mediated VEGF(121) gene transfer stimulates angiogenesis in normoperfused skeletal muscle and preserves tissue perfusion after induction of ischemia.

Administration of angiogenic factors stimulates neovascularization in ischemic tissues. However, there is no evidence that angiogenesis can be induced in normoperfused skeletal muscles. We tested the hypothesis that adenovirus-mediated intramuscular (IM) gene transfer of the 121-amino-acid form of vascular endothelial growth factor (AdCMV.VEGF(121)) could stimulate neovascularization in nonischemic skeletal muscle and consequently attenuate the hemodynamic deficit secondary to surgically induced ischemia. Rabbits and rats received IM injections of AdCMV.VEGF(121), AdCMV.Null, or saline in the thigh, 4 weeks (rabbits) or 2 weeks (rats) before femoral artery removal in the injected limb. In unoperated rats, at the site of injection of AdCMV.VEGF(121), we found 96% and 29% increases in length density of arterioles and capillaries, respectively. Increased tissue perfusion (TP) to the ischemic limb in the AdCMV.VEGF(121) group was documented, as early as day 1 after surgery, by improved blood flow to the ischemic gastrocnemius muscle measured by radioactive microspheres (AdCMV.VEGF(121)=5.69+/-0.40, AdCMV.Null=2.97+/-0.50, and saline=2.78+/-0.43 mL x min(-1) x 100 g(-1), P<0.001), more angiographically recognizable collateral vessels (angioscore) (AdCMV. VEGF(121)=50.58+/-1.48, AdCMV.Null=29.08+/-4.22, saline=11.83+/-1.90, P<0.0001), and improvement of the bioenergetic reserve of the gastrocnemius muscle as assessed by (31)P NMR spectroscopy. Follow-up studies showed that superior TP to the ischemic limb in the AdCMV.VEGF(121) group persisted until it was equalized by spontaneous collateral vessel development in untreated animals. IM administration of AdCMV.VEGF(121) stimulates angiogenesis in normoperfused skeletal muscles, and the newly formed vessels preserve TP after induction of ischemia.