Visualization of cell death in mice with focal cerebral ischemia using fluorescent annexin A5, propidium iodide, and TUNEL staining.

To monitor stroke-induced brain damage and assess neuroprotective therapies, specific imaging of cell death after cerebral ischemia in a noninvasive manner is highly desirable. Annexin A5 has been suggested as a marker for imaging cell death under various disease conditions including stroke. In this study, C57BL6/N mice received middle cerebral artery occlusion (MCAO) and were injected intravenously with either active or inactive Cy5.

Site-specific labeling of 'second generation' annexin V with 99mTc(CO)3 for improved imaging of apoptosis in vivo.

In this study 'second generation' AnxV was specifically labeled with (99m)Tc in three different ways outside the binding region of the protein to obtain an improved target-to-background activity ratio. The compounds were tested in vitro and in vivo in normal mice and in a model of hepatic apoptosis (anti-Fas mAb). The apoptosis binding was most prominent for the HIS-tagged 'second generation' AnxV labeled with (99m)Tc(CO)(3) in comparison to (99m)Tc-HYNIC-cys-AnxV and (99m)Tc(CO)(3)-DTPA-cys-AnxV.

Syndecan-1 amplifies angiotensin II-induced cardiac fibrosis.

Syndecan-1 (Synd1) is a transmembrane heparan sulfate proteoglycan that functions as a coreceptor for various growth factors and modulates signal transduction. The present study investigated whether Synd1, by affecting growth factor signaling, may play a role in hypertension-induced cardiac fibrosis and dysfunction. Expression of Synd1 was increased significantly in mouse hearts with angiotensin II-induced hypertension, which was spatially related to cardiac fibrosis.

Myocardial remodeling after infarction: the role of myofibroblasts.

Myofibroblasts have characteristics of fibroblasts and smooth muscle cells: they produce extracellular matrix and are able to contract. In so doing, they can contribute to tissue replacement and interstitial fibrosis following cardiac injury. The scar formed after myocardial injury is no longer considered to be passive tissue; it is an active playground where myofibroblasts play a role in collagen turnover and scar contraction.

Transfection efficiency of lipoplexes for site-directed delivery.

Targeted gene delivery is a promising strategy to cure disease on its basic level at the site of interest. The ultrastructure, internalization, and transfection efficiency of lipoplexes was investigated. We found that at a charge ratio (rho) of 4.

Dual molecular imaging for targeting metalloproteinase activity and apoptosis in atherosclerosis: molecular imaging facilitates understanding of pathogenesis.

Background: Macrophage apoptosis and MMP activity contribute to vulnerability of atherosclerotic plaques to rupture. By employing molecular imaging techniques, we investigated if apoptosis and MMP release are interlinked.

Methods: Atherosclerosis was produced in rabbits receiving high-cholesterol diet (HC), who underwent dual radionuclide imaging with (99m)Tc-labeled matrix metalloproteinase inhibitor (MPI) and (111)In-labeled annexin A5 (AA5) using micro-SPECT/CT.

Hypoxia induces dilated cardiomyopathy in the chick embryo: mechanism, intervention, and long-term consequences.

Background: Intrauterine growth restriction is associated with an increased future risk for developing cardiovascular diseases. Hypoxia in utero is a common clinical cause of fetal growth restriction. We have previously shown that chronic hypoxia alters cardiovascular development in chick embryos.

Macrophage depletion in hypertensive rats accelerates development of cardiomyopathy.

Inflammation contributes to the process of ventricular remodeling after acute myocardial injury. To investigate the role of macrophages in the chronic process of cardiac remodeling, they were selectively depleted by intravenous administration of liposomal clodronate in heart failure-prone hypertensive Ren-2 rats from the age of 7 until 13 weeks. Plain liposomes were used for comparison.

Extracellular annexin A5: functions of phosphatidylserine-binding and two-dimensional crystallization.

In normal healthy cells phosphatidylserine is located in the inner leaflet of the plasma membrane. However, on activated platelets, dying cells and under specific circumstances also on various types of viable leukocytes phosphatidylserine is actively externalized to the outer leaflet of the plasma membrane. Annexin A5 has the ability to bind in a calcium-dependent manner to phosphatidylserine and to form a membrane-bound two-dimensional crystal lattice.

Broad and specific caspase inhibitor-induced acute repression of apoptosis in atherosclerotic lesions evaluated by radiolabeled annexin A5 imaging.

Objectives: The purpose of this study was to evaluate the role of caspase inhibitors on acute resolution of apoptosis in atherosclerotic lesions as evaluated by imaging with annexin A5.

Background: Extensive apoptosis of macrophages has been reported at the site of plaque rupture in patients dying of acute coronary syndrome.

Methods: Of 31 New Zealand White atherosclerotic rabbits, 6 received broad caspase, 3 received caspase-1, 3 received caspase-3, 3 received caspase-8, and 4 received caspase-9 inhibitors; 12 animals did not receive any caspase inhibitors (treatment control group).

Targeting of matrix metalloproteinase activation for noninvasive detection of vulnerable atherosclerotic lesions.

Inflammation plays an important role in vulnerability of atherosclerotic plaques to rupture and hence acute coronary events. The monocyte-macrophage infiltration in plaques leads to upregulation of cytokines and metalloproteinase enzymes. Matrix metalloproteinases result in matrix dissolution and consequently expansive remodeling of the vessel.

In vitro measurement of cell death with the annexin A5 affinity assay.

One of the hallmarks of cell death is the cell surface-expression of phosphatidylserine. Expression of phosphatidylserine at the cell surface can be measured in vitro with the phosphatidylserine-binding protein annexin A5 conjugated to fluorochromes. This measurement can be made by flow cytometry or by confocal scanning-laser microscopy.

Noninvasive detection of programmed cell loss with 99mTc-labeled annexin A5 in heart failure.

Unlabelled: Apoptosis, or programmed cell death (PCD), contributes to the decline in ventricular function in heart failure. Because apoptosis comprises a programmed cascade of events, it is potentially reversible, and timely intervention should delay the development of cardiomyopathy. (99m)Tc-Labeled annexin A5 has successfully been used for the noninvasive detection of PCD in myocardial infarction and heart transplant rejection.

cNGR: a novel homing sequence for CD13/APN targeted molecular imaging of murine cardiac angiogenesis in vivo.

Objective: Previously, the peptide sequence cNGR has been shown to home specifically to CD13/APN (aminopeptidase N) on tumor endothelium. Here, we investigated the feasibility of selective imaging of cardiac angiogenesis using the cNGR-CD13/APN system.

Methods And Results: CD13/APN induction and cNGR homing were studied in the murine myocardial infarction (MI) model.

Annexin A5 inhibits engulfment through internalization of PS-expressing cell membrane patches.

Apoptosis and subsequent clearance of apoptotic cells are important for the prevention of diseases. Therefore, it is essential to understand the mechanisms underlying the biology of phagocytic clearance of apoptotic cells. The best characterized "eat me" signal on the surface of apoptotic cells is phosphatidylserine (PS).

Resolution of apoptosis in atherosclerotic plaque by dietary modification and statin therapy.

Unlabelled: Although apoptosis within atherosclerotic plaques is associated with plaque vulnerability and rupture, the role of inhibition of the apoptotic process is not clear. We evaluated the impact of dietary modification and statin therapy (measures known to favorably influence outcomes in coronary disease) on the incidence of apoptosis in experimental atherosclerotic lesions.

Methods: A total of 30 animals were studied; 1 group of 6 animals served as the controls (group 1), and the remaining 24 animals were subjected to balloon de-endothelialization of the abdominal aorta and a high-cholesterol diet.

Partial cell fusion: a newly recognized type of communication between dedifferentiating cardiomyocytes and fibroblasts.

Objective: Fibroblasts have been shown to couple to neonatal cardiomyocytes in heterocellular cultures through functional gap junctions. Our objective was to provide evidence for an additional type of heterocellular communication between fibroblasts and adult cardiomyocytes in vitro and in vivo.

Methods: The contact areas in heterocellular co-cultures were evaluated by specific labeling and the intercellular communication was studied using preloading of fibroblasts with tracer molecules.

Myocyte apoptosis in heart failure.

Human heart failure is preceded by a process termed cardiac remodeling in which heart chambers progressively enlarge and contractile function deteriorates. Programmed cell death (apoptosis) of cardiac muscle cells has been identified as an essential process in the progression to heart failure. The execution of the apoptotic program entails complex interactions between and execution of multiple molecular subprograms.

Abdominal aortic aneurysm screening during transthoracic echocardiography in an unselected population.

Objective: We sought to investigate the echocardiographic prevalence of abdominal aortic aneurysm (AAA) in an unselected group of patients referred for regular transthoracic echocardiography (TTE).

Methods: Prospectively, during a 3-month period, a limited ultrasound examination of the infrarenal aorta was performed. AAA was defined as a diameter of 30 mm or more.

Annexin A5 down-regulates surface expression of tissue factor: a novel mechanism of regulating the membrane receptor repertoir.

Phosphatidylserine (PtdSer) is exposed on the external leaflet of the plasma membrane during apoptosis. The protein annexin A5 (anxA5) shows high affinity for PtdSer. When anxA5 binds to the PtdSer-expressing membranes during apoptosis, it crystallizes as an extended two-dimensional network and activates thereby a novel portal of cell entry that results in the internalization of the PtdSer-expressing membrane patches.

Cell surface-expressed phosphatidylserine and annexin A5 open a novel portal of cell entry.

Expression of phosphatidylserine (PtdSer) at the cell surface is part of the membrane dynamics of apoptosis. Expressed phosphatidylserine functions as an "eat me" flag toward phagocytes. Here, we report that the expressed phosphatidylserine forms part of a hitherto undescribed pinocytic pathway.