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Abstract-Angiogenesis, an essential component of a variety of physiological and pathological processes, offers attractive opportunities for therapeutic regulation. We hypothesized that matrix metalloproteinase-9 genetic deficiency (MMP-9 Ϫ/Ϫ ) will impair angiogenesis triggered by tissue ischemia, induced experimentally by femoral artery ligation in mice.To investigate the role of MMP-9, we performed a series of biochemical and histological analyses, including zymography, simultaneous detection of perfused capillaries, MMP-9 promoter activity, MMP-9 protein, and macrophages in MMP-9 Ϫ/Ϫ and wild-type (WT) mice. We found that ischemia resulted in doubling of capillary density in WT and no change in the MMP-9 Ϫ/Ϫ ischemic tissues, which translated into increased (39%) perfusion capacity only in the WT at 14 days after ligation. We also confirmed that capillaries in the MMP-9 Ϫ/Ϫ presented significantly (PϽ0.05) less points of capillary intersections, interpreted by us as decreased branching. The combined conclusions from simultaneous localizations of MMP-9 expression, capillaries, and macrophages suggested that macrophage MMP-9 participates in capillary branching. Transplantation of WT bone marrow into the MMP-9 Ϫ/Ϫ , restored capillary branching, further supporting the contribution of bone marrow-derived macrophages in supplying the necessary MMP-9. Our study indicates that angiogenesis triggered by tissue ischemia requires MMP-9, which may be involved in capillary branching, a potential novel role for this MMP that could be exploited to control angiogenesis. Key Words: angiography Ⅲ macrophage Ⅲ imaging Ⅲ microvessels Ⅲ bone-marrow transplantation A ngiogenesis, the growth of new capillaries from existing ones, is a process necessary for regulation and repair during wound healing and after ischemic injury of tissue. However, angiogenesis also facilitates grave pathological processes such as tumor progression and metastasis, 1 macular degeneration, 2 and atheroma progression toward plaque instability. 3 Oxygen deprivation, or tissue ischemia, is a potent stimulus of angiogenesis through both humoral and inflammatory processes. 4 Angiogenesis is a complex process that involves the activation of vascular cells through a balance of pro-and antiangiogenic factors. 4 The growth of new capillaries is thought to occur mainly through capillary splitting, also known as intussusception, or capillary budding leading to branching. 5 As growth of capillaries likely necessitates invasion of existing tissues, the potential enabling action of matrix metalloproteinases (MMPs), a family of enzymes capable of degrading the extracellular matrix components, has come under scrutiny. 6 In fact, the antiangiogenic action of nonspecific MMP inhibitors in vivo 7 and in vitro 8 is thought to be of major importance for their anticancer activity. 9 However, these chemical agents have also undesirable effects. 10 Two members of the MMP family, MMP-2 and MMP-9, known to degrade nonfibrillar collagens, a major component of the basement membrane...

Background-Although multiple pathological processes have been associated with oxidative stress, the causative relation between oxidative stress and arterial lesion progression remains unclear.

Macrophage-derived foam cells in developing atherosclerotic lesions may potentially originate either from recruitment of circulating monocytes or from migration of resident tissue macrophages. In this study, we have determined the source of intimal macrophages in the apoE-knockout mouse flow-cessation/hypercholesterolemia model of atherosclerosis using a bone marrow transplantation approach. We also examined the time course and spatial distribution of intercellular adhesion molecule-1 and vascular cell adhesion molecule-1 expression to assess whether endothelial adhesion molecules were involved in recruitment of either circulating monocytes or resident macrophages. We used allelic variants of the mouse common leukocyte antigen (CD45) to distinguish host-derived and donor-derived white blood cells (WBCs) both in blood and in macrophage-rich carotid lesions. We found that the distribution of CD45 isoforms in lesions is similar to that of circulating WBCs, whereas the host-type CD45 isoform is more prevalent in resident adventitial macrophages. These data indicate that macrophage-derived foam cells in the lesion derive mainly from circulating precursors rather than from resident macrophages. The corresponding time course of intercellular adhesion molecule-1 and vascular cell adhesion molecule-1 expression suggests that recruitment of circulating WBCs by endothelial adhesion molecules is likely to be more important during lesion initiation than during the later phase of rapid lesion growth. Both in experimental models of atherosclerosis and in human disease, infiltration of macrophages into the arterial intima constitutes one of the earliest cellular events in the development of atherosclerotic lesions. 1-3 Macrophages in the lesion may be derived either from cells already resident in the arterial wall 4 or from circulating monocytes that have undergone diapedesis. Because the mechanisms of cellular recruitment and/or activation are likely to differ depending on the source of the inflammatory cells, determining the relative contribution to lesion growth of cells from these two sources may have important implications in devising successful strategies to slow the growth of lesions.Although much convincing evidence demonstrates the importance of blood-borne monocytes in early lesion development, 1,5,6 the potential contribution of resident macrophages has been more difficult to assess. Experiments involving injection of labeled tracer monocytes can provide estimates for the rate of recruitment of circulating inflammatory cells but do not directly address the issue of mobilization of macrophages already present in arterial tissue. Moreover, alterations in adhesion molecule expression that can occur during monocyte isolation and labeling may modify the interaction between circulating monocytes and the vascular wall. The recent development of a polymerase chain reaction-based method of quantifying monocyte recruitment has shown promise of improved sensitivity and ease of quantitation compared to more traditional approach...

Background-Recent observations associate plaque instability with expansive arterial remodeling, suggesting a common driving mechanism. Methods and Results-To demonstrate that macrophages, a characteristic of vulnerable plaques, also assist in expansive remodeling, we compared carotid artery remodeling due to formation of experimental macrophage-rich and macrophage-poor lesions in the flow cessation model in hypercholesterolemic apolipoprotein E knockout (ApoE KO) and wild type (WT) mice. After ligation, macrophages started to rapidly accumulate in ApoE KO but not in WT carotid artery lesions. Macrophage-rich ApoE KO intimal lesions grew fast, typically occluding within 14 days, despite a tripling of the vessel area. Outward remodeling of macrophage-rich ApoE KO arteries positively correlated with macrophage area (r 2 ϭ0.600, PϽ0.001). To investigate potential mechanisms of macrophage-enabled expansive remodeling, we compared levels of matrix metalloproteinases in homogenates of macrophage-rich and macrophage-poor carotid arteries. Gelatinolytic activity of macrophage-rich lesions increased faster and reached maximal levels several fold higher than in the macrophage-poor WT lesions. Conclusions-Our results suggest that macrophages facilitate expansive arterial remodeling through increased matrix degradation by matrix metalloproteinases. This initially favorable remodeling action may eventually increase the vulnerability of macrophage-rich atherosclerotic plaques.

Inflammation-mediated endothelial cell (EC) dysfunction likely contributes to the pathogenesis of several vascular diseases including atherosclerosis. We found that stimulation of human umbilical vein ECs with lipopolysaccharide induced secretion of cyclophilin (CyPA) an intracellular protein belonging to the immunophilin family. We then found that when added exogenously CyPA has direct effects on ECs in vitro. At low concentrations (10 to 100 ng/ml) CyPA increased EC proliferation, migration, invasive capacity, and tubulogenesis. Gelatin zymography indicated increased secretion of active matrix metalloproteinase-2, a mediator of cell migration and angiogenesis. At high concentrations (eg, 2 g/ml) CyPA had opposite effects, decreasing EC migration and viability, possibly in relation to induction of Toll-like receptor-4 expression, detected by immunocytochemistry and flow cytometry. In vivo CyPA expression was not detectable in the luminal ECs of normal mouse carotid arteries but was rapidly induced after systemic lipopolysaccharide injection. In an experimental mouse model of atherosclerosis, CyPA expression was detected in the ECs of neocapillaries of carotid artery lesions, supporting its association with pathological angiogenesis suggested by our in vitro results. In conclusion, we found that CyPA has a biphasic activity on ECs in vitro and is up-regulated in vivo in ECs under pathological states. Our results suggest that CyPA is a novel paracrine and autocrine modulator of EC functions in immune-mediated vascular disease.

Significant challenges remain in targeting drugs to diseased vasculature; most important being rapid blood flow with high shear, limited availability of stable targets, and heterogeneity and recycling of cellular markers. We developed nanoparticles (NPs) to target degraded elastic lamina, a consistent pathological feature in vascular diseases. In-vitro organ and cell culture experiments demonstrated that these NPs were not taken up by cells, but instead retained within the extracellular space; NP binding was proportional to the extent of elastic lamina damage. With three well-established rodent models of vascular diseases such as aortic aneurysm (calcium chloride mediated aortic injury in rats), atherosclerosis (fat-fed apoE−/− mice), and vascular calcification (warfarin + vitamin K injections in rats), we show precise NPs spatial targeting to degraded vascular elastic lamina while sparing healthy vasculature when NPs were delivered systemically. Nanoparticle targeting degraded elastic lamina is attractive to deliver therapeutic or imaging agents to the diseased vasculature.

In this work, we use the vapor‐sorption equilibrium data to show the degree of solvent upturn in each solvent‐polymer system. For this purpose, 20 isothermal data sets for five polymer + solvent binaries have been used in the temperature range of 298–413 K. Solvents studied are benzene, pentane, hexane, toluene, and chlorobenzene. Homopolymers studied are: polystyrene, poly(vinyl acetate), polyisobutylene, and polyethylene. According to these data sets, solvent weight fraction in the polymer is plotted against solvent vapor activity that is calculated assuming an ideal gas phase of pure solvent vapor neglecting the vapor pressure of the polymer. We use the Flory‐Huggins theory to obtain dimensionless interaction parameter, χ. Also the Zimm‐Lundberg clustering theory and non‐ideality thermodynamic factor, Γ are used to interpret the equilibrium data. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010