CD44 Regulates Arteriogenesis in Mice and Is Differentially Expressed in Patients With Poor and Good Collateralization

CD44 promotes angiogenesis in myocardial infarction through regulating plasma exosome uptake and further enhancing FGFR2 signaling transduction

BACKGROUND

Since angiogenesis occurs as the pathological process following myocardial infarction to alleviate ischemia, therapeutic angiogenesis has been proposed to be a cardioprotective strategy. CD44 has been implicated in endothelial cell functions and its role has been well established in angiogenesis for years. Although recent studies indicate the close correlation between CD44 and exosome, as well as the two being implicated in myocardial ischemia pathological processes, the effect and the underlying mechanism of CD44 and its regulated plasma exosome in pathological angiogenesis post-myocardial infarction have not been fully elucidated.

METHODS

In this study, we used CD44 knockout mice to study the in vivo impacts of CD44 on ischemic angiogenesis in myocardial infarction. Mouse cardiac function was measured by echocardiography, histological changes were observed by Evans Blue and TTC-double staining and Masson's trichrome staining, and molecular changes were detected by immunofluorescence. In the in vitro study, CD44 knockout HUVECs were generated and CD44 inhibitor was used to study the mechanism of CD44 on angiogenesis. We performed the immunoprecipitation, proximity ligation assay, and super-resolution imaging to study the mechanistic regulation of FGFR2 signaling transduction by CD44. Importantly, we also isolated plasma exosomes from myocardial infarction model mice and studied the effect of plasma exosomes on the activation of the FGFR2 signaling pathway and the related phenotypic alterations, including exosomes uptake and angiogenic function in primary mouse microvascular endothelial cells, and further discovered the regulation mechanism of exosomal miRNAs.

RESULTS

We observed that the expression of CD44 in the border zone of the infarcted heart was tightly related to pathological angiogenesis following myocardial ischemia. The depletion of CD44 impaired angiogenesis and impacts biogenesis and proangiogenic function of plasma exosomes. Subsequently, we found that CD44 mediated the activation of the FGFR2 signaling pathway as well as the caveolin 1-dependent uptake of exosomes in vascular endothelial cells. Most importantly, the proangiogenic therapeutic effect of plasma exosomal miRNAs depended upon the participation of CD44/FGFR2 signaling transduction in vascular endothelial cells.

CONCLUSION

CD44 and its regulated plasma exosomes have crucial potent angiogenic activity. Our studies elucidate that CD44 plays a key role in plasma exosomal miRNA-enhanced angiogenic FGFR2 singling transduction and ischemic angiogenesis in the early stage of myocardial infarction.

Endothelial Hyaluronan Synthase 3 Augments Postischemic Arteriogenesis Through CD44/eNOS Signaling

Objective: The dominant driver of arteriogenesis is elevated shear stress sensed by the endothelial glycocalyx thereby promoting arterial outward remodeling. Hyaluronan, a critical component of the endothelial glycocalyx, is synthesized by 3 HAS isoenzymes (hyaluronan synthases 1-3) at the plasma membrane. Considering further the importance of HAS3 for smooth muscle cell and immune cell functions we aimed to evaluate its role in collateral artery growth. Approach and Results: Male Has3-deficient (Has3-KO) mice were subjected to hindlimb ischemia. Blood perfusion was monitored by laser Doppler perfusion imaging and endothelial function was assessed by measurement of flow-mediated dilation in vivo. Collateral remodeling was monitored by high resolution magnetic resonance angiography. A neutralizing antibody against CD44 (clone KM201) was injected intraperitoneally to analyze hyaluronan signaling in vivo. After hindlimb ischemia, Has3-KO mice showed a reduced arteriogenic response with decreased collateral remodeling and impaired perfusion recovery. While postischemic leukocyte infiltration was unaffected, a diminished flow-mediated dilation pointed towards an impaired endothelial cell function. Indeed, endothelial AKT (protein kinase B)-dependent eNOS (endothelial nitric oxide synthase) phosphorylation at Ser1177 was substantially reduced in Has3-KO thigh muscles. Endothelial-specific Has3-KO mice mimicked the hindlimb ischemia-induced phenotype of impaired perfusion recovery as observed in global Has3-deficiency. Mechanistically, blocking selectively the hyaluronan binding site of CD44 reduced flow-mediated dilation, thereby suggesting hyaluronan signaling through CD44 as the underlying signaling pathway. Conclusions: In summary, HAS3 contributes to arteriogenesis in hindlimb ischemia by hyaluronan/CD44-mediated stimulation of eNOS phosphorylation at Ser1177. Thus, strategies augmenting endothelial HAS3 or CD44 could be envisioned to enhance vascularization under pathological conditions.

The role of CD44 in pathological angiogenesis

Angiogenesis is required for normal development and occurs as a pathological step in a variety of disease settings, such as cancer, ocular diseases, and ischemia. Recent studies have revealed the role of CD44, a widely expressed cell surface adhesion molecule, in promoting pathological angiogenesis and the development of its associated diseases through its regulation of diverse function of endothelial cells, such as proliferation, migration, adhesion, invasion, and communication with the microenvironment. Conversely, the absence of CD44 expression or inhibition of its function impairs pathological angiogenesis and disease progression. Here, we summarize the current understanding of the roles of CD44 in pathological angiogenesis and the underlying cellular and molecular mechanisms.

Localized SDF-1α Delivery Increases Pro-Healing Bone Marrow-Derived Cells in the Supraspinatus Muscle Following Severe Rotator Cuff Injury

To examine how the chemotactic agent stromal cell-derived factor-1alpha (SDF-1α) modulates the unique cellular milieu within rotator cuff muscle following tendon injury, we developed an injectable, heparin-based microparticle platform to locally present SDF-1α within the supraspinatus muscle following severe rotator cuff injury. SDF-1α loaded, degradable, N-desulfated heparin-based microparticles were fabricated, injected into a rat model of severe rotator cuff injury, and were retained for up to 7 days at the site. The resultant inflammatory cell and mesenchymal stem cell populations were analyzed compared to uninjured contralateral controls and, after 7 days, the fold-change in anti-inflammatory, M2-like macrophages (CD11b+CD68+CD163+, 4.3X fold-change) and mesenchymal stem cells (CD29+CD44+CD90+, 3.0X, respectively) was significantly greater in muscles treated with SDF-1α loaded microparticles than unloaded microparticles or injury alone. Our results indicate that SDF-1α loaded microparticles may be a novel approach to shift the cellular composition within the supraspinatus muscle and create a more pro-regenerative milieu, which may provide a platform to improve muscle repair following rotator cuff injury in the future.

Induction of extracranial arteriogenesis by an arteriovenous fistula in a pig model

BACKGROUND AND AIMS

Arteriogenesis, the positive outward remodeling and growth of pre-existent collateral vessels, holds potential as a novel treatment for ischemic vascular disease. An extracranial arteriogenesis model in a pig will allow us to study molecular changes in a complex arteriolar network in a more clinically relevant large-animal model. To increase fluid shear stress in the brain, an experimental carotid arteriovenous fistula (AVF model) in minipigs was established, providing high flow through the extracranial rete mirabile. The aim of the study was to examine whether creation of a carotid AVF can induce extracranial arteriogenesis in the pig.

METHODS

Angiography was performed to demonstrate blood flow diversion. Animals were sacrificed after 0, 3 and 14 days post-surgery and both retia mirabilia were removed. Immunohistochemical analysis was performed to analyze cell proliferation and accumulation of mononuclear cells in the vessel wall.

RESULTS

After 3 days of high-flow conditions, increases in vascular cell proliferation (approximately 1.5-fold; p = 0.143) and monocyte invasion (approximately 6-fold; p = 0.057) were observed when compared to animals sacrificed immediately after AVF formation. Quantitative PCR (RT-qPCR) analysis from rete mirabile tissue samples 3 days post-surgery revealed that monocyte chemoattractant protein (MCP)-1 and tissue inhibitor of metalloproteinases (TIMP)-1 were highly upregulated. Expression of the pro-arteriogenic marker, CD44, reached maximum expression level 14 days post-surgery.

CONCLUSIONS

In response to high levels of shear stress produced in the pig AVF model, the onset of the arteriogenic process can be induced. This was demonstrated by enhanced cell proliferation, monocyte invasion and vascular remodeling.

Molecular controls of arterial morphogenesis

Formation of arterial vasculature, here termed arteriogenesis, is a central process in embryonic vascular development as well as in adult tissues. Although the process of capillary formation, angiogenesis, is relatively well understood, much remains to be learned about arteriogenesis. Recent discoveries point to the key role played by vascular endothelial growth factor receptor 2 in control of this process and to newly identified control circuits that dramatically influence its activity. The latter can present particularly attractive targets for a new class of therapeutic agents capable of activation of this signaling cascade in a ligand-independent manner, thereby promoting arteriogenesis in diseased tissues.

Elevated survivin expression in peripheral blood mononuclear cells is central to collateral formation in coronary chronic total occlusion

Survivin is essential to angiogenesis and revascularization, but its role in coronary collateral formation remains unclear. The role of survivin in peripheral blood mononuclear cells (PBMCs) of coronary chronic total occlusion (CTO) patients was investigated. Coronary CTO patients (n=46; mean age 60.1±8.5, male 54.3%) (CTO group) and normal control patients (n=18; mean age 58.0±10.0, male 55.6%) underwent angiographic collateral vessel grading by Rentrop classification (C0 - C3) and provided peripheral blood between June 2006 and February 2007. Rat hind limb ischemia models were constructed using four equal groups of Sprague-Dawley rats (n=36): normal control, sham operation, operation and granulocyte macrophage colony-stimulating factor (GM-CSF). PBMC numbers and characteristics, collateral vessels, survivin, CD4, CD8, CD44, vascular endothelial growth factor (VEGF) and intercellular adhesion molecule-1 (ICAM-1) expression were determined using RT-PCR, flow cytometry, immunocytochemistry and western blot analysis. PBMC survivin mRNA and protein expression levels were higher in patients with good collateral circulation (C2 + C3) than in patients with no collateral flow (C0) (all P<0.05). Survivin single-positive and survivin and CD8, VEGF and ICAM-1 double-positive percentages were elevated in patients with good collateral circulation compared to those with normal and no collateral flow (all P<0.05), consistent with the rat model results, wherein higher survivin levels produced significantly larger and more visible collateral vessels. In conclusion, elevated survivin expression in PBMCs, particularly survivin and CD8, VEGF, and ICAM-1 double-positive PBMCs, may be crucial for good collateral formation in patients with coronary CTO, as confirmed by assessment of a rat model.

Genes related to suppression of malignant phenotype induced by Maitake D-Fraction in breast cancer cells

It is already known that the Maitake (D-Fraction) mushroom is involved in stimulating the immune system and activating certain cells that attack cancer, including macrophages, T-cells, and natural killer cells. According to the U.S. National Cancer Institute, polysaccharide complexes present in Maitake mushrooms appear to have significant anticancer activity. However, the exact molecular mechanism of the Maitake antitumoral effect is still unclear. Previously, we have reported that Maitake (D-Fraction) induces apoptosis in breast cancer cells by activation of BCL2-antagonist/killer 1 (BAK1) gene expression. At the present work, we are identifying which genes are responsible for the suppression of the tumoral phenotype mechanism induced by Maitake (D-Fraction) in breast cancer cells. Human breast cancer MCF-7 cells were treated with and without increased concentrations of Maitake D-Fraction (36, 91, 183, 367 μg/mL) for 24 h. Total RNA were isolated and cDNA microarrays were hybridized containing 25,000 human genes. Employing the cDNA microarray analysis, we found that Maitake D-Fraction modified the expression of 4068 genes (2420 were upmodulated and 1648 were downmodulated) in MCF-7 breast cancer cells in a dose-dependent manner during 24 h of treatment. The present data shows that Maitake D-Fraction suppresses the breast tumoral phenotype through a putative molecular mechanism modifying the expression of certain genes (such as IGFBP-7, ITGA2, ICAM3, SOD2, CAV-1, Cul-3, NRF2, Cycline E, ST7, and SPARC) that are involved in apoptosis stimulation, inhibition of cell growth and proliferation, cell cycle arrest, blocking migration and metastasis of tumoral cells, and inducing multidrug sensitivity. Altogether, these results suggest that Maitake D-Fraction could be a potential new target for breast cancer chemoprevention and treatment.

Evidence for the interaction of fibroblast growth factor-2 with the lymphatic endothelial cell marker LYVE-1

LYVE-1 (lymphatic vessel endothelial hyaluronan receptor-1) is a homolog of the hyaluronan receptor CD44, and one of the most widely used markers of lymphatic endothelial cells in normal and tumor tissues. However, the physiologic role of LYVE-1 in the lymphatic system still remains unclear. It is well established that fibroblast growth factor 2 (FGF2) induces lymphangiogenesis. Based on the known interaction between FGF2 and CD44 and based on the structural similarity of CD44 and LYVE-1, we investigated whether FGF2 might interact with LYVE-1. We found that FGF2 is able to bind LYVE-1 using AlphaScreen, or after surface-immobilization or in solution. FGF2 binds to LYVE-1 with a higher affinity than any other known LYVE-1–binding molecules, such as hyaluronan or PDGF-BB. Glycosylation of LYVE-1 is important for FGF2 binding. Furthermore, FGF2 interacts with LYVE-1 when overexpressed in CHO cells. Soluble LYVE-1 and knockdown of LYVE-1 in lymphatic endothelial cells impaired FGF2 signaling and functions. In addition, FGF2 but not VEGF-C-induced in vivo lymphangiogenesis, was also inhibited. Conversely, FGF2 also modulates LYVE-1 expression in cells and ex vivo. Thus, our data demonstrate a functional relationship to the interaction between FGF2 and LYVE-1.

Characteristics of CD44 alternative splice pattern in the course of human colorectal adenocarcinoma progression

BACKGROUND

CD44 is considered as 'a' metastasis associated gene, despite the fact that it is an umbrella term for a group of molecules produced from a single gene by alternative splicing. However, little consideration is given to the above in the literature of colorectal carcinomas as well as other tumour types, leading to confusion and contradictory results about its possible role in tumour progression.

METHODS

We compared the CD44 alternative splice pattern (ASP) of three genetically different human colorectal cancer cell lines (HT25, HT29, HCT116) using a series of PCR reactions and next- generation sequencing method, as well as identified a colorectal adenocarcinoma specific CD44 ASP. This ASP was further investigated in terms of its qualitative and quantitative stability in our experimental iso- and xenograft mouse models for colorectal cancer progression. A complex preclinical experimental set-up was established to separately test the different steps of tumour progression and the role of tumour microenvironment, respectively, focusing on the role of 'CD44' in this process.

RESULTS

We managed to present a colorectal cancer-specific CD44 ASP, which remained unchanged from cell lines throughout primary tumour formation and metastatic progression. Furthermore, we report a unique roster of all expressed CD44 variant isoforms characteristic to colorectal cancer. Finally, on quantitative assessment of the variable exons v3 and v6, higher co-expression levels were found to be characteristic to metastatically potent tumour cells.

CONCLUSION

Particular CD44 variant isoforms seem to act as "metastasis genes" via tumour microenvironment-driven shifts in v3 and v6 expressions. However, this function may just affect a minority of tumour subclones. This fact and the huge potential number of different CD44 splice variants that can contain v3 and v6 domains can explain incoherence of clinical studies regarding functional asessment of CD44 variants, as well as diminish the chances of using CD44 variants for predictive purpose.

Selective gene expression analysis of muscular and vascular components in hearts using laser microdissection method

Background. The heart consists of various kinds of cell components. However, it has not been feasible to separately analyze the gene expression of individual components. The laser microdissection (LMD) method, a new technology to collect target cells from the microscopic regions, has been used for malignancies. We sought to establish a method to selectively collect the muscular and vascular regions from the heart sections and to compare the marker gene expressions with this method. Methods and Results. Frozen left ventricle sections were obtained from Wistar-Kyoto rats (WKY) and stroke-prone spontaneously hypertensive rats (SHR-SP) at 24 weeks of age. Using the LMD method, the muscular and vascular regions were selectively collected under microscopic guidance. Real-time RT-PCR analysis showed that brain-type natriuretic peptide (BNP), a marker of cardiac myocytes, was expressed in the muscular samples, but not in the vascular samples, whereas α-smooth muscle actin, a marker of smooth muscle cells, was detected only in the vascular samples. Moreover, SHR-SP had significantly greater BNP upregulation than WKY (P < 0.05) in the muscular samples. Conclusions. The LMD method enabled us to separately collect the muscular and vascular samples from myocardial sections and to selectively evaluate mRNA expressions of the individual tissue component.

Arterial occlusion induces systemic changes in leucocyte composition

BACKGROUND

Lack of tissue perfusion because of arterial occlusion can result in mortality and morbidity. In response to local tissue ischaemia, extravasation of leucocytes into the region at risk is initiated to facilitate matrix remodelling and subsequent perfusion recovery. However, it is unknown if local tissue ischaemia also induces a more generalized response of leucocyte trafficking and compartmentalization. This study was designed to gain insight into the temporal changes in circulating and bone marrow-derived leucocyte fractions following peripheral arterial occlusion in mice.

MATERIALS AND METHODS

Mouse peripheral blood and bone marrow samples were collected at baseline and subsequently at day 1, 2, 3, 4 and 7 after femoral artery ligation. Leucocyte and bone marrow cell subsets were quantified using flow cytometry.

RESULTS

After arterial occlusion, peripheral blood leucocyte numbers did not vary significantly over time. However, significant intrinsic temporal changes in cell numbers were observed for monocytes, lymphocytes, neutrophils and their subsets with fluctuations of > 50%. Granulocytes, for example, showed an initial upregulation, while monocytes and lymphocytes numbers initially decreased. These variations in the circulation were largely preceded by changes in the corresponding bone marrow lineages. Progenitor cells of the myeloid and lymphoid lineage in the bone marrow were upregulated after the decrease in the numbers of their progeny in the peripheral blood.

CONCLUSIONS

Local arterial occlusion results in an orchestrated systemic response of leucocyte trafficking. This response substantiates the pivotal role of leucocytes as mediators of processes leading to perfusion recovery and tissue remodelling.

The role of imprinted genes in fetal growth abnormalities

Epigenetics, and in particular imprinted genes, have a critical role in the development and function of the placenta, which in turn has a central role in the regulation of fetal growth and development. A unique characteristic of imprinted genes is their expression from only one allele, maternal or paternal and dependent on parent of origin. This unique expression pattern may have arisen as a mechanism to control the flow of nutrients from the mother to the fetus, with maternally expressed imprinted genes reducing the flow of resources and paternally expressed genes increasing resources to the fetus. As a result, any epigenetic deregulation affecting this balance can result in fetal growth abnormalities. Imprinting-associated disorders in humans, such as Beckwith-Wiedemann and Angelman syndrome, support the role of imprinted genes in fetal growth. Similarly, assisted reproductive technologies in animals have been shown to affect the epigenome of the early embryo and the expression of imprinted genes. Their role in disorders such as intrauterine growth restriction appears to be more complex, in that imprinted gene expression can be seen as both causative and protective of fetal growth restriction. This protective or compensatory effect needs to be explored more fully.

Vascular growth in ischemic limbs: a review of mechanisms and possible therapeutic stimulation

Stimulation of vascular growth to treat limb ischemia is promising, and early results obtained from uncontrolled clinical trials using angiogenic agents, e.g., vascular endothelial growth factor, led to high expectations. However, negative results from recent placebo-controlled trials warrant further research. Here, current insights into mechanisms of vascular growth in the adult, in particular the role of angiogenic factors, the immune system, and bone marrow, were reviewed, together with modes of its therapeutic stimulation and results from recent clinical trials. Three concepts of vascular growth have been described to date-angiogenesis, vasculogenesis, and arteriogenesis (collateral artery growth)-which represent different aspects of an integrated process. Stimulation of arteriogenesis seems clinically most relevant and has most recently been attempted using autologous bone marrow transplantation with some beneficial results, although the mechanism of action is not completely understood. Better understanding of the highly complex molecular and cellular mechanisms of vascular growth may yet lead to meaningful clinical applications.

Interferon-β Signaling Is Enhanced in Patients With Insufficient Coronary Collateral Artery Development and Inhibits Arteriogenesis in Mice

Stimulation of collateral artery growth in patients has been hitherto unsuccessful, despite promising experimental approaches. Circulating monocytes are involved in the growth of collateral arteries, a process also referred to as arteriogenesis. Patients show a large heterogeneity in their natural arteriogenic response on arterial obstruction. We hypothesized that circulating cell transcriptomes would provide mechanistic insights and new therapeutic strategies to stimulate arteriogenesis. Collateral flow index was measured in 45 patients with single-vessel coronary artery disease, separating collateral responders (collateral flow index, >0.21) and nonresponders (collateral flow index, ≤0.21). Isolated monocytes were stimulated with lipopolysaccharide or taken into macrophage culture for 20 hours to mimic their phenotype during arteriogenesis. Genome-wide mRNA expression analysis revealed 244 differentially expressed genes (adjusted P , <0.05) in stimulated monocytes. Interferon (IFN)-β and several IFN-related genes showed increased mRNA levels in 3 of 4 cellular phenotypes from nonresponders. Macrophage gene expression correlated with stimulated monocytes, whereas resting monocytes and progenitor cells did not display differential gene regulation. In vitro, IFN-β dose-dependently inhibited smooth muscle cell proliferation. In a murine hindlimb model, perfusion measured 7 days after femoral artery ligation showed attenuated arteriogenesis in IFN-β–treated mice compared with controls (treatment versus control: 31.5±1.2% versus 41.9±1.9% perfusion restoration, P <0.01). In conclusion, patients with differing arteriogenic response as measured with collateral flow index display differential transcriptomes of stimulated monocytes. Nonresponders show increased expression of IFN-β and its downstream targets, and IFN-β attenuates proliferation of smooth muscle cells in vitro and hampers arteriogenesis in mice. Inhibition of IFN-β signaling may serve as a novel approach for the stimulation of collateral artery growth.

Gene and stem cell therapy in peripheral arterial occlusive disease

Abstract

Peripheral arterial occlusive disease (PAOD) is a manifestation of systemic atherosclerosis strongly associated with a high risk of cardiovascular morbidity and mortality. In a considerable proportion of patients with PAOD, revascularization either by endovascular means or by open surgery combined with best possible risk factor modification does not achieve limb salvage or relief of ischaemic rest pain. As a consequence, novel therapeutic strategies have been developed over the last two decades aiming to promote neovascularization and remodelling of collaterals. Gene and stem cell therapy are the main directions for clinical investigation concepts. For both, preclinical studies have shown promising results using a wide variety of genes encoding for growth factors and populations of adult stem cells, respectively. As a consequence, clinical trials have been performed applying gene and stem cell-based concepts. However, it has become apparent that a straightforward translation into humans is not possible. While several trials reported relief of symptoms and functional improvement, other trials did not confirm this early promise of efficacy. Ongoing clinical trials with an improved study design are needed to confirm the potential that gene and cell therapy may have and to prevent the gaps in our scientific knowledge that will jeopardize the establishment of angiogenic therapy as an additional medical treatment of PAOD. This review summarizes the experimental background and presents the current status of clinical applications and future perspectives of the therapeutic use of gene and cell therapy strategies for PAOD.

Stimulation of collateral artery growth: a potential treatment for peripheral artery disease

In the course of peripheral artery occlusive disease, blood flow to peripheral tissue progressively decreases in a substantial portion of patients, leading to insufficient oxygenation and to the occurrence of claudication or critical limb ischemia. Arteriogenesis (collateral artery growth) is a powerful natural mechanism by which large conductance vessels develop that circumvent sites of obstruction. Promising experimental data on both hypoxia-driven angiogenesis as well as monocyte-orchestrated arteriogenesis have raised high hopes for clinical application. Both endothelial growth factors to stimulate angiogenesis (i.e., capillary growth) and monocyte-attracting or -activating substances to stimulate arteriogenesis, have been proposed as potential new therapeutic agents. However, transferring the promising experimental results into clinical practice has been more cumbersome than initially anticipated. Some recent clinical studies are now focusing more specifically on the stimulation of arteriogenesis. This review will critically evaluate the results of preclinical and clinical investigations on the stimulation of vascular growth, focusing specifically on the peripheral circulation.

CD44 regulates myoblast migration and differentiation

CD44 is a transmembrane protein that plays a role in cell-cell interactions and motility in a number of cell types. Cell-cell interactions are critical for myoblast differentiation and fusion but whether CD44 regulates myogenesis is unknown. Here, we show that CD44 plays a functional role in early myogenesis. Analyses of myofiber cross-sectional area, after local injury in mouse tibialis anterior (TA) muscles, revealed that growth was transiently delayed in the absence of CD44. A muscle-intrinsic role for CD44 is suggested as primary myoblasts from CD44(-/-) mice displayed attenuated differentiation and subsequent myotube formation at early times in a differentiation-inducing in vitro environment. Chemotaxis of CD44(-/-) myoblasts toward hepatocyte growth factor (HGF) and basic fibroblast growth factor (bFGF) was totally abrogated, although expression of their respective receptors did not appear to differ from wild-type. Furthermore, motility of CD44(-/-) myoblasts was decreased at early stages of differentiation as determined by time-lapse microscopy. Wild-type myoblasts contained two subpopulations of slow- and fast-migrating cells, whereas CD44(-/-) myoblasts were composed predominantly of the slower migrating subpopulation. Taken together, these data suggest that myoblast migration and differentiation are closely linked and CD44 is a key regulator.

Determinants and prognostic significance of collaterals in patients undergoing coronary revascularization

There is evidence that coronary collaterals improve the prognosis in patients with acute myocardial infarction (MI). However, there is limited clinical information on the protective role of collaterals in patients with stable coronary artery disease. This information may help risk stratification and the development of novel therapies, such as arteriogenesis and angiogenesis. The relation between collaterals and cardiac death or MI at 1 year after coronary revascularization was studied in 561 patients who were enrolled in a randomized study that compared stent implantation with bypass grafting. Collaterals were assessed on an angiogram using Rentrop's classification and considered present with a Rentrop grade >1. Unadjusted and adjusted odds ratios for cardiac death or MI at 1 year were calculated using univariate and multivariate regression analyses. In addition, determinants of collaterals were assessed using univariate and multivariate analyses. Collaterals were present in 176 patients (31%). The adjusted odds ratio of cardiac death or infarction was 0.18 (95% confidence interval 0.04 to 0.78) in the presence of collaterals. Independent determinants of collaterals were age (odds ratio 0.97, 95% confidence interval 0.95 to 0.99), multivessel disease (odds ratio 1.60, 95% confidence interval 1.02 to 2.51), impaired ventricular function (odds ratio 1.85, 95% confidence interval 1.04 to 3.29), type C lesion (odds ratio 3.72, 95% confidence interval 2.33 to 5.95), and stenosis severity >90% (odds ratio 9.08, 95% confidence interval 4.65 to 17.73). In conclusion, in patients with a low risk profile, the presence of collaterals protects against cardiac death and MI at 1 year after coronary revascularization. Variables that reflect the duration and severity of the atherosclerotic and ischemic burden determine their presence.

A potential evidence to explain the reason behind the devastating prognosis of coronary artery disease in uraemic patients: renal insufficiency is associated with poor coronary collateral vessel development

The potential of individuals to develop coronary collateral circulation is often neglected but is of potential major importance in myocardial vulnerability. Likewise, the effect of chronic kidney disease (CKD) on collateral vessel development is not known. The purpose of this study was to evaluate the effect of CKD on collateral development in patients with advanced coronary artery disease. A total of 171 uraemic patients (serum creatinine > or = 1.5 mg/dl, creatinine clearance < 80 mL)/min) who underwent coronary angiography were evaluated in this study. A total of 134 patients met the criteria for the uraemic group and 134 consecutive non-uraemic patients who constituted the control group. The collateral score (CS) was graded according to the Rentrop classification and the collateral score was calculated by summing the Rentrop numbers of every patient. Collateral vessels have also been categorized according to their anatomic locations and collateral connection grades (CC). CC2 collaterals were observed less frequently in the uraemic patients than in the control subjects (11% versus 26%, p=0.03) and CC0 more frequently (31% versus 22%, p<0.05). Epicardial pathway was detected more frequently in the control subjects than in the uraemic patients (31% versus 12%, p=0.03) and septal pathway less frequently (37% versus 54%). There was a significant negative correlation between CS and creatinine (r=-0.68, p<0.01). The mean CS in the uraemic group was significantly lower than the non-uraemic group (1.29+/-0.88 versus 2.18+/-1.3, p<0.001). These results altogether showed that besides the quantity, quality (functional, haemodynamic and anatomic features) of the uraemic collaterals and a network that they constitute is also impaired and different from the collaterals of the patient with normal renal function.

Experimental models of arteriogenesis: differences and implications

Cardiovascular and cerebrovascular disease represent the two most common causes of mortality and morbidity in western countries, and the treatment for these is generally by the mechanical restoration of blood flow in the affected tissues. Stimulation of collateral artery growth (arteriogenesis) provides a potential alternative option for the treatment of patients suffering from occlusive artery disease. Therefore, researchers have established several angiogenesis and arteriogenesis animal models to investigate basic mechanisms and pharmacological modulation of collateral artery growth. The authors highlight the most important aspects of vascular growth, discuss different methods and techniques for examining the process, and review the advantages and disadvantages associated with the animal models available for studying this phenomenon.

Angiogenesis in the human heart: gene and cell therapy

The concept of therapeutic angiogenesis -- stimulation of new vessels growth to restore blood supply to ischemic tissue has been studied in a number of clinical trials in patients with advanced coronary and peripheral arterial disease. This review discusses the main biological processes underlying new vessel growth and addresses applications of growth factor and cell therapy based on the stimulation of angiogenesis. While still very young and controversial, cell therapy has an enormous potential that is yet to be explored. Multiple questions remain unanswered including the choice of the best cell type, patient selection and the mechanism of action. Nevertheless, much should be expected in this area in the next decade with the likely emergence of new therapies for treatment of ischemic diseases.

START Trial: a pilot study on STimulation of ARTeriogenesis using subcutaneous application of granulocyte-macrophage colony-stimulating factor as a new treatment for peripheral vascular disease

BACKGROUND

Granulocyte-macrophage colony-stimulating factor (GM-CSF) was recently shown to increase collateral flow index in patients with coronary artery disease. Experimental models showed beneficial effects of GM-CSF on collateral artery growth in the peripheral circulation. Thus, in the present study, we evaluated the effects of GM-CSF in patients with peripheral artery disease.

METHODS AND RESULTS

A double-blinded, randomized, placebo-controlled study was performed in 40 patients with moderate or severe intermittent claudication. Patients were treated with placebo or subcutaneously applied GM-CSF (10 microg/kg) for a period of 14 days (total of 7 injections). GM-CSF treatment led to a strong increase in total white blood cell count and C-reactive protein. Monocyte fraction initially increased but thereafter decreased significantly as compared with baseline. Both the placebo group and the treatment group showed a significant increase in walking distance at day 14 (placebo: 127+/-67 versus 184+/-87 meters, P=0.03, GM-CSF: 126+/-66 versus 189+/-141 meters, P=0.04) and at day 90. Change in walking time, the primary end point of the study, was not different between groups. No change in ankle-brachial index was found on GM-CSF treatment at day 14 or at day 90. Laser Doppler flowmetry measurements showed a significant decrease in microcirculatory flow reserve in the control group (P=0.03) and no change in the GM-CSF group.

CONCLUSIONS

The present study does not support the use of GM-CSF for treatment of patients with moderate or severe intermittent claudication. Issues that need to be addressed are dosing, the selection of patients, and potential differences between GM-CSF effects in the coronary and the peripheral circulation.

Structural remodeling of mouse gracilis artery after chronic alteration in blood supply

The goals of this study were to determine the time course and spatial dependence of structural diameter changes in the mouse gracilis artery after a redistribution of blood flow and to compare the observations with predictions of computational models for structural adaptation. Diameters were measured 1, 2, 7, 14, 21, 28, and 56 days after resection of one of the two blood supplies to the artery. Overall average diameter, normalized with respect to diameters in untreated vessels, increased slightly during the first 7 days, then increased more rapidly, reaching a peak around day 21, and then decreased. This transient increase in diameter was spatially nonuniform, being largest toward the point of resection. A previously developed theoretical model, in which diameter varies in response to stimuli derived from local metabolic and hemodynamic conditions, was extended to include effects of time-delayed remodeling stimuli in regions of reduced perfusion. Predictions of this model were consistent with observed diameter changes, including the transient increase in diameters near the point of resection, when a remodeling stimulus with a time delay of approximately 7 days was included. The results suggest that delayed stimuli significantly influence the dynamic characteristics of vascular remodeling resulting from reduced blood supply.

Role of Coronary Collaterals in Off-Pump and On-Pump Coronary Bypass Surgery

BACKGROUND

Collaterals limit infarct size, preserve viability, and reduce mortality in patients with acute myocardial infarction. In patients with stable coronary disease, collaterals are associated with less angina and ischemia during angioplasty and fewer ischemic events during follow-up. The role of collaterals has not been studied in patients undergoing off-pump or on-pump bypass surgery.

METHODS AND RESULTS

The population consisted of the 281 patients randomized to off-pump or on-pump CABG in the Octopus Study. Collaterals were defined on the baseline angiogram with the Rentrop score and were present in 49% and 51% of the patients in the off-pump and on-pump group, respectively. Perioperative myocardial infarction was defined by a creatine kinase-MB to CK ratio >10% and occurred in 18.2% in the off-pump group and 32.5% in the on-pump group. The unadjusted OR of perioperative myocardial infarction in the presence of collaterals was 0.31 (95% CI 0.17 to 0.84) in the off-pump group and 1.06 (95% CI 0.29 to 3.85) in the on-pump group After adjustment for age, gender, hypertension, hypercholesterolemia, diabetes, multivessel disease, ventricular dysfunction, incomplete revascularization, and ischemic time, the OR was 0.34 (95% CI 0.14 to 0.84) in the off-pump group and 1.28 (95% CI 0.30 to 5.40) in the on-pump group, respectively. Kaplan-Meier estimates of event-free survival at 1 year were 87% in patients with and 69% in those without collaterals after off-pump CABG. These estimates were 66% and 63%, respectively, after on-pump CABG.

CONCLUSIONS

Collaterals protect against perioperative myocardial infarction during off-pump surgery but not during on-pump surgery and are associated with a better 1-year event-free survival.