Identification of CD8+ T cell PRDM1 in high-risk human plaques and its regulatory role in murine lesion development

Funding Acknowledgements

Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Fritz Thyssen Stiftung

T cells have a prominent role in the pathogenesis of atherosclerosis, although their function in atherosclerotic plaques is only partly understood. In this study, we utilize the advantages of high-throughput techniques and data analytic strategies to compare the inherent biological changes of T cells during plaque transition from a stable, non-haemorrhaged (low-risk) to a rupture-prone, haemorrhaged (high-risk) phenotype.

We classified 43 human carotid arterial lesions into high- and low-risk plaques based on the presence/absence of intraplaque hemorrhages. RNA from these lesions was isolated and microarray gene expression data was obtained and analyzed by Weighted Gene Co-expression Network Analysis. A strong T cell signalling signature was identified in high- versus low-risk plaques, influencing angiogenesis and interferon-related processes. Bayesian network inference, cell type deconvolution and single-cell RNA sequencing analysis revealed that the T cell-associated gene program was linked to effector-memory cytotoxic, CD8+ T cells. This gene program appeared driven by CD8+ T cell-related transcription factors, including RUNX3, IRF7 and most importantly PRDM1. To validate these findings, we demonstrated in a murine model that T cell PRDM1 plays a key role in plaque formation, as atherosclerotic mice with a T cell specific Prdm1 deficiency developed larger and more advanced atherosclerotic plaques compared to control mice.

In conclusion, our study unveils a clear PRDM1-regulated effector-memory cytotoxic CD8+ T cell footprint in plaque development and the shift from low- to high-risk plaques, thereby revealing CD8+ T cells and PRMD1 as potential targets for intervention in adverse T cell responses in human atherosclerotic lesions.

Live Observation of Atherosclerotic Plaque Disruption in Apolipoprotein E-Deficient Mouse

AIM

The actual occurrence of spontaneous plaque rupture in mice has been a matter of debate. We report on an in vivo observation of the actual event of possible plaque disruption in a living ApoE(-/-) mouse.

METHODS AND RESULTS

During live contrast-enhanced ultrasonography of a 50-week-old ApoE(-/-) male mouse, symptoms suggesting plaque disruption in the brachiocephalic artery were observed. Histological analysis confirmed the presence of advanced atherosclerotic lesions with dissections and intraplaque hemorrhage in the affected brachiocephalic trunk, pointing towards plaque rupture as the cause of the observed event. However, we did not detect a luminal thrombus or cap rupture, which is a key criterion for plaque rupture in human atherosclerosis.

CONCLUSION

This study reports the real-time occurrence of a possible plaque rupture in a living ApoE(-/-) mouse.

Intracranial Vessel Wall MRI: Principles and Expert Consensus Recommendations of the American Society of Neuroradiology

Intracranial vessel wall MR imaging is an adjunct to conventional angiographic imaging with CTA, MRA, or DSA. The technique has multiple potential uses in the context of ischemic stroke and intracranial hemorrhage. There remain gaps in our understanding of intracranial vessel wall MR imaging findings and research is ongoing, but the technique is already used on a clinical basis at many centers. This article, on behalf of the Vessel Wall Imaging Study Group of the American Society of Neuroradiology, provides expert consensus recommendations for current clinical practice.

Phase-based vascular input function: Improved quantitative DCE-MRI of atherosclerotic plaques

PURPOSE

Quantitative pharmacokinetic modeling of dynamic contrast-enhanced (DCE)-MRI can be used to assess atherosclerotic plaque microvasculature, which is an important marker of plaque vulnerability. Purpose of the present study was (1) to compare magnitude- versus phase-based vascular input functions (m-VIF vs ph-VIF) used in pharmacokinetic modeling and (2) to perform model calculations and flow phantom experiments to gain more insight into the differences between m-VIF and ph-VIF.

METHODS

Population averaged m-VIF and ph-VIFs were acquired from 11 patients with carotid plaques and used for pharmacokinetic analysis in another 17 patients. Simulations, using the Bloch equations and the MRI scan geometry, and flow phantom experiments were performed to determine the effect of local blood velocity on the magnitude and phase signal enhancement.

RESULTS

Simulations and flow phantom experiments revealed that flow within the lumen can lead to severe underestimation of m-VIF, while this is not the case for the ph-VIF. In line, the peak concentration of the m-VIF is significantly lower than ph-VIF (p < 0.001), in vivo. Quantitative model parameters for m- and ph-VIF differed in absolute values but were moderate to strongly correlated with each other [K(trans) Spearman's ρ > 0.93 (p < 0.001) and vp Spearman's ρ > 0.58 (p < 0.05)].

CONCLUSIONS

m-VIF is strongly influenced by local blood velocity, which leads to underestimation of the contrast medium concentration. Therefore, it is advised to use ph-VIF for DCE-MRI analysis of carotid plaques for accurate quantification.

Intraplaque Hemorrhage and the Plaque Surface in Carotid Atherosclerosis: The Plaque At RISK Study (PARISK)

BACKGROUND AND PURPOSE

An important characteristic of vulnerable plaque, intraplaque hemorrhage, may predict plaque rupture. Plaque rupture can be visible on noninvasive imaging as a disruption of the plaque surface. We investigated the association between intraplaque hemorrhage and disruption of the plaque surface.

MATERIALS AND METHODS

We selected the first 100 patients of the Plaque At RISK study, an ongoing prospective noninvasive plaque imaging study in patients with mild-to-moderate atherosclerotic lesions in the carotid artery. In carotid artery plaques, disruption of the plaque surface (defined as ulcerated plaques and/or fissured fibrous cap) and intraplaque hemorrhage were assessed by using MDCTA and 3T MR imaging, respectively. We used a χ(2) test and multivariable logistic regression to assess the association between intraplaque hemorrhage and disrupted plaque surface.

RESULTS

One hundred forty-nine carotid arteries in 78 patients could be used for the current analyses. Intraplaque hemorrhage and plaque ulcerations were more prevalent in symptomatic compared with contralateral vessels (hemorrhage, 38% versus 11%; P < .001; and ulcerations, 27% versus 7%; P = .001). Fissured fibrous cap was more prevalent in symptomatic compared with contralateral vessels (13% versus 4%; P = .06). After adjustment for age, sex, diabetes mellitus, and degree of stenosis, intraplaque hemorrhage was associated with disrupted plaque surface (OR, 3.13; 95% CI, 1.25-7.84) in all vessels.

CONCLUSIONS

Intraplaque hemorrhage is associated with disruption of the plaque surface in patients with a carotid artery stenosis of <70%. Serial studies are needed to investigate whether intraplaque hemorrhage indeed increases the risk of plaque rupture and subsequent ischemic stroke during follow-up.

Imaging the intracranial atherosclerotic vessel wall using 7T MRI: initial comparison with histopathology

BACKGROUND AND PURPOSE

Several studies have attempted to characterize intracranial atherosclerotic plaques by using MR imaging sequences. However, dedicated validation of these sequences with histology has not yet been performed. The current study assessed the ability of ultra-high-resolution 7T MR imaging sequences with different image contrast weightings to image plaque components, by using histology as criterion standard.

MATERIALS AND METHODS

Five specimens of the circle of Wills were imaged at 7T with 0.11 × 0.11 mm in-plane-resolution proton attenuation-, T1-, T2-, and T2*-weighted sequences (through-plane resolution, 0.11-1 mm). Tissue samples from 13 fiducial-marked locations (per specimen) on MR imaging underwent histologic processing and atherosclerotic plaque classification. Reconstructed MR images were matched with histologic sections at corresponding locations.

RESULTS

Forty-four samples were available for subsequent evaluation of agreement or disagreement between plaque components and image contrast differences. Of samples, 52.3% (n = 23) showed no image contrast heterogeneity; this group comprised solely no lesions or early lesions. Of samples, 25.0% (n = 11, mostly advanced lesions) showed good correlation between the spatial organization of MR imaging heterogeneities and plaque components. Areas of foamy macrophages were generally seen as proton attenuation-, T2-, and T2*- hypointense areas, while areas of increased collagen content showed more ambiguous signal intensities. Five samples showed image-contrast heterogeneity without corresponding plaque components on histology; 5 other samples showed contrast heterogeneity based on intima-media artifacts.

CONCLUSIONS

MR imaging at 7T has the image contrast capable of identifying both focal intracranial vessel wall thickening and distinguishing areas of different signal intensities spatially corresponding to plaque components within more advanced atherosclerotic plaques.

Plaque at RISK (PARISK): Prospective Multicenter Study to Improve Diagnosis of High-Risk Carotid Plaques

Background

Patients with symptomatic carotid artery stenosis are at high risk for recurrent stroke. To date, the decision to perform carotid endarterectomy in patients with a recent cerebrovascular event is mainly based on degree of stenosis of the ipsilateral carotid artery. However, additional atherosclerotic plaque characteristics might be better predictors of stroke, allowing for more precise selection of patients for carotid endarterectomy.

Aims and hypothesis

We investigate the hypothesis that the assessment of carotid plaque characteristics with magnetic resonance imaging, multidetector-row computed tomography angiography, ultrasonography, and transcranial Doppler, either alone or in combination, may improve identification of a subgroup of patients with <70% carotid artery stenosis with an increased risk of recurrent stroke.

Methods

The Plaque At RISK (PARISK) study is a prospective multicenter cohort study of patients with recent (<3 months) neurological symptoms due to ischemia in the territory of the carotid artery and < 70% ipsilateral carotid artery stenosis who are not scheduled for carotid endarterectomy or stenting. At baseline, 300 patients will undergo magnetic resonance imaging, multidetector-row computed tomography angiography, and ultrasonography examination of the carotid arteries. In addition, magnetic resonance imaging of the brain, ambulatory transcranial Doppler recording of the middle cerebral artery and blood withdrawal will be performed. After two-years, imaging will be repeated in 150 patients. All patients undergo a follow-up brain magnetic resonance imaging, and there will be regular clinical follow-up until the end of the study. Study outcomes The combined primary end-point contains ipsilateral recurrent ischemic stroke or transient ischemic attack or new ipsilateral ischemic brain lesions on follow-up brain magnetic resonance imaging.

Genetic loss of Gas6 induces plaque stability in experimental atherosclerosis

The growth arrest-specific gene 6 (Gas6) plays a role in pro-atherogenic processes such as endothelial and leukocyte activation, smooth muscle cell migration and thrombosis, but its role in atherosclerosis remains uninvestigated. Here, we report that Gas6 is expressed in all stages of human and mouse atherosclerosis, in plaque endothelial cells, smooth muscle cells and macrophages. Gas6 expression is most abundant in lesions containing high amounts of macrophages, ie thin fibrous cap atheroma and ruptured plaque. Genetic loss of Gas6 does not affect the number and size of initial and advanced plaques in ApoE(-/-) mice, but alters its plaque composition. Compared to Gas6(+/+): ApoE(-/-) mice, initial and advanced plaques of Gas6(-/-): ApoE(-/-) mice contained more smooth muscle cells and more collagen and developed smaller lipid cores, while the expression of TGFbeta was increased. In addition, fewer macrophages were found in advanced plaques of Gas6(-/-): ApoE(-/-) mice. Hence, loss of Gas6 promotes the formation of more stable atherosclerotic lesions by increasing plaque fibrosis and by attenuating plaque inflammation. These findings identify a role for Gas6 in plaque composition and stability.

Anti-oxLDL antibody isotype levels, as potential markers for progressive atherosclerosis in APOE and APOECD40L mice

In humans and animal models of atherosclerosis, antibodies against oxidized LDL have been associated with atherosclerotic lesion development. It has been suggested that IgM anti-oxLDL antibodies are anti-atherogenic, whereas IgG anti-oxLDL antibodies are pro-atherogenic. In this study, we examined the relation between IgM and IgG antibody levels and atherosclerosis severity in APOE(-/-)CD40L(-/-) mice, which are deficient for IgG and develop moderate advanced atherosclerosis, and compared results with mice developing severe (APOE(-/-)) or no atherosclerosis (C57Bl/6). Mice were followed in time for anti-oxLDL antibodies while on high-fat diet or normal chow. Anti-oxLDL antibody levels were determined by ELISA. Results revealed that 24-week-old APOE(-/-)CD40L(-/-) mice had enhanced IgM anti-oxLDL antibody levels when compared with wild-type mice, but similar levels to those of APOE(-/-) mice. As expected, IgG anti-oxLDL antibody levels were almost absent in APOE(-/-)CD40L(-/-) mice. The transition from early to advanced lesions in APOE(-/-) mice was reflected by elevated IgM anti-oxLDL antibody levels. IgM anti-oxLDL levels did not further increase during progression to more advanced lesions. No relation was found between IgG anti-oxLDL levels and atherosclerosis severity. In conclusion, the severity of advanced atherosclerosis in mice is not reflected by IgM and/or IgG anti-oxLDL antibody levels. Furthermore, less advanced atherosclerotic lesion development in APOE(-/-)CD40L(-/-) mice does not seem to be the result of higher levels of protective IgM anti-oxLDL antibodies. Therefore, our study does not support the idea that the previously observed inconsistency in the relation between anti-oxLDL and atherosclerosis severity is due to differences in antibody isotypes.

Disruption of hedgehog signalling in ApoE - /- mice reduces plasma lipid levels, but increases atherosclerosis due to enhanced lipid uptake by macrophages

Embryonic pathways are often re-expressed in adult pathology. Here we investigated the role of the morphogen hedgehog (hh), which we found to be re-expressed in atherosclerotic plaques. Male ApoE - /- mice were treated for 12 weeks with an anti-hh antibody (5E1) or a control IgG (1E6) starting at the age of 6 or 18 weeks. Inhibition of hh signalling induced a significant increase in total plaque area in the aortic arch, a result of an increase (54% and 36%, respectively) in the area of advanced plaques (atheromata). In mice treated with anti-hh, plaques contained large (18-35% > ctrl), lipid-filled, sometimes multinucleated macrophage foam cells. Plasma cholesterol levels decreased after anti-hh treatment. In bone marrow-derived macrophages, foam cell formation was enhanced after inhibition of hh signalling. Anti-hh treatment caused a 54-75% increase in early oxLDL uptake (10-240 min), which was scavenger receptor-mediated. After 3-24 h of oxLDL incubation, intense Oil red O staining as well as increased amounts of cholesterol esters were present in these macrophages after anti-hh treatment. Activation of the HH-signalling cascade by recombinant Shh induced a decrease in oxLDL uptake. Here we show that the hh-signalling pathway is one of the morphogenic pathways that regulate plasma lipid levels and atherosclerosis development and progression.

Animal models to study plaque vulnerability

The need to identify and characterize vulnerable atherosclerotic lesions in humans has lead to the development of various animal models of plaque vulnerability. In this review, current concepts of the vulnerable plaque as it leads to an acute coronary event are described, such as plaque rupture, erosion, intraplaque hemorrhage and neovascularization. Recently developed animal models that have attempted to reproduce these concepts are described and evaluated based on their suitability in the study of vulnerable plaques. Although certain features of plaque vulnerability have been reported in animal models, a model encompassing all aspects of the vulnerable plaque is lacking.

Gene profiling of cathepsin K deficiency in atherogenesis: profibrotic but lipogenic

Recently, we showed that cathepsin K deficiency reduces atherosclerotic plaque progression, induces plaque fibrosis, but aggravates macrophage foam cell formation in the ApoE -/- mouse. To obtain more insight into the molecular mechanisms by which cathepsin K disruption evokes the observed phenotypic changes, we used microarray analysis for gene expression profiling of aortic arches of CatK -/-/ApoE -/- and ApoE -/- mice on a mouse oligo microarray. Out of 20 280 reporters, 444 were significantly differentially expressed (p-value of < 0.05, fold change of > or = 1.4 or < or = - 1.4, and intensity value of > 2.5 times background in at least one channel). Ingenuity Pathway Analysis and GenMAPP revealed upregulation of genes involved in lipid uptake, trafficking, and intracellular storage, including caveolin - 1, - 2, - 3 and CD36, and profibrotic genes involved in transforming growth factor beta (TGFbeta) signalling, including TGFbeta2, latent TGFbeta binding protein-1 (LTBP1), and secreted protein, acidic and rich in cysteine (SPARC), in CatK -/-/ApoE -/- mice. Differential gene expression was confirmed at the mRNA and protein levels. In vitro modified low density lipoprotein (LDL) uptake assays, using bone marrow derived macrophages preincubated with caveolae and scavenger receptor inhibitors, confirmed the importance of caveolins and CD36 in increasing modified LDL uptake in the absence of cathepsin K. In conclusion, we suggest that cathepsin K deficiency alters plaque phenotype not only by decreasing proteolytic activity, but also by stimulating TGFbeta signalling. Besides this profibrotic effect, cathepsin K deficiency has a lipogenic effect owing to increased lipid uptake mediated by CD36 and caveolins.

Genome-Wide Expression Studies of Atherosclerosis

During the past 6 years, gene expression profiling of atherosclerosis has been used to identify genes and pathways relevant in vascular (patho)physiology. This review discusses some critical issues in the methodology, analysis, and interpretation of the data of gene expression studies that have made use of vascular specimens from animal models and humans. Analysis of gene expression studies has evolved toward the genome-wide expression profiling of large series of individual samples of well-characterized donors. Despite the advances in statistical and bioinformatical analysis of expression data sets, studies have not yet fully exploited the potential of gene expression data sets to obtain novel insights into the molecular mechanisms underlying atherosclerosis. To assess the potential of published expression data, we compared the data of a CC chemokine gene cluster between 18 murine and human gene expression profiling articles. Our analysis revealed that an adequate comparison is mainly hindered by the incompleteness of available data sets. The challenge for future vascular genomic profiling studies will be to further improve the experimental design, statistical, and bioinformatical analysis and to make data sets freely accessible.

Disruption of the cathepsin K gene reduces atherosclerosis progression and induces plaque fibrosis but accelerates macrophage foam cell formation

BACKGROUND

Cathepsin K (catK), a lysosomal cysteine protease, was identified in a gene-profiling experiment that compared human early plaques, advanced stable plaques, and advanced atherosclerotic plaques containing a thrombus, where it was highly upregulated in advanced stable plaques.

METHODS AND RESULTS

To assess the function of catK in atherosclerosis, catK(-/-)/apolipoprotein (apo) E(-/-) mice were generated. At 26 weeks of age, plaque area in the catK(-/-)/apoE(-/-) mice was reduced (41.8%) owing to a decrease in the number of advanced lesions as well as a decrease in individual advanced plaque area. This suggests an important role for catK in atherosclerosis progression. Advanced plaques of catK(-/-)/apoE(-/-) mice showed an increase in collagen content. Medial elastin fibers were less prone to rupture than those of apoE(-/-) mice. Although the relative macrophage content did not differ, individual macrophage size increased. In vitro studies of bone marrow derived-macrophages confirmed this observation. Scavenger receptor-mediated uptake (particularly by CD36) of modified LDL increased in the absence of catK, resulting in an increased macrophage size because of increased cellular storage of cholesterol esters, thereby enlarging the lysosomes.

CONCLUSIONS

A deficiency of catK reduces plaque progression and induces plaque fibrosis but aggravates macrophage foam cell formation in atherosclerosis.

Is there more than C-reactive protein and fibrinogen? The prognostic value of soluble CD40 ligand, interleukin-6 and oxidized low-density lipoprotein with respect to coronary and cerebral vascular disease

Incidence of atherosclerosis and atherosclerosis-related complications will increase significantly in the coming decennia. Research identified many serum and plasma markers that are associated with cardiovascular disease. However, little is known about the prognostic value of these markers to identify patients at risk for future cardiovascular events. Therefore, we aimed to investigate the prognostic value of three of these markers (soluble CD40 ligand (sCD40L), interleukin-6 (IL-6) and oxidized low-density lipoprotein (oxLDL)) with respect to coronary vascular disease and stroke. For this reason the Medline database was searched for the period January 1999-January 2005. To be selected in our study, concentration of the marker had to be determined at baseline, follow-up period had to be longer than 3 months and an estimate of relative risk had to be available. Based on these criteria, 4 studies for sCD40L, 10 for IL-6 and 2 for oxLDL were selected. Relative risk estimates adjusted for potential confounders varied between 1.9 and 2.8 for sCD40L, between 1.1 and 3.1 for IL-6 and between 1.9 and 3.2 for oxLDL. In conclusion, this systematic review shows that sCD40L, IL-6 and oxLDL are associated with an increased relative risk of developing cardiovascular disease.

Leukocyte CD40L deficiency affects the CD25+ CD4 T cell population but does not affect atherosclerosis

Inhibition of CD40-CD40L interactions results in a reduction of innate regulatory T cells (Tregs) in CD40(-/-) mice and induces a stable plaque phenotype in atherosclerosis-prone mouse strains. Here we investigated the effects of leukocyte CD40L on the Treg population and on atherosclerosis. LDLR(-/-) mice were reconstituted with wild-type or CD40L(-/-) bone marrow (BM). These BM chimeras were analysed by flow cytometry for the presence of innate Tregs (CD45RB(low) CD25(+) CD4) in lymphoid organs and peripheral blood. As in CD40(-/-) mice, the CD45RB(high):CD45RB(low) CD4 T cell ratio significantly increased and the CD25(+) CD4(+) subpopulation significantly decreased in LDLR(-/-) mice receiving CD40L(-/-) BM compared to LDLR(-/-) mice receiving wild-type BM. However, atherosclerotic plaque progression and plaque phenotype did not change in LDLR(-/-) mice reconstituted with CD40L(-/-) BM. In conclusion, the present study shows that CD40-CD40L interactions on leukocytes are essential for the size of the CD45RB(low) CD25(+) CD4 Treg subpopulation. Nevertheless, CD40L deficiency on hemopoietic cells did not affect atherosclerosis, implying that CD40L expressing leukocytes alone are not responsible for the stable plaque phenotype observed after total CD40L blockade.

Changes in Vascular Distensibility during Angiotensin-Converting Enzyme Inhibition Involve Bradykinin Type 2 Receptors

Changes in arterial stiffness and structure occur during cardiovascular diseases and can be modified by angiotensin-converting enzyme (ACE) inhibitors. In the present study we investigated the role of membrane-bound ACE (t-ACE) in the regulation of arterial structure and mechanics. Large and small arteries of t-ACE-/- mice were isolated to determine the passive pressure-diameter relationship. We observed that t-ACE-/- mice exhibit a reduced arterial distensibility compared to t-ACE+/+ mice. This reduced arterial distensibility was also observed after 9 weeks of captopril treatment (80 mg/kg/ day). We hypothesized that bradykinin type 2 receptor (BK(2)) stimulation might be involved in the regulation of arterial stiffness. t-ACE-/- and t-ACE+/+ mice were treated with Hoe 140 (1 mg/kg/day) for 14 days. After Hoe 140 treatment, both the structural and mechanical changes observed in the t-ACE-/- carotid artery were abolished. Although Hoe 140 administration increased blood pressure in both groups by approximately 10 mm Hg, the pressure difference between the two groups did not change. Thus, t-ACE is involved in the regulation of arterial distensibility. The changes observed in t-ACE-/- mice are not caused by an altered fetal development. Moreover, it is likely that the regulation of arterial distensibility by ACE involves stimulation of the BK(2) receptor.

Accumulation of ultrasmall superparamagnetic particles of iron oxide in human atherosclerotic plaques can be detected by in vivo magnetic resonance imaging

BACKGROUND

One of the features of high-risk atherosclerotic plaques is a preponderance of macrophages. Experimental studies with hyperlipidemic rabbits have shown that ultrasmall superparamagnetic particles of iron oxide (USPIOs) accumulate in plaques with a high macrophage content and that this induces magnetic resonance (MR) signal changes. The purpose of our study was to investigate whether USPIO-enhanced MRI can also be used for in vivo detection of macrophages in human plaques.

METHODS AND RESULTS

MRI was performed on 11 symptomatic patients scheduled for carotid endarterectomy before and 24 (n=11) and 72 (n=5) hours after administration of USPIOs (Sinerem) at a dose of 2.6 mg Fe/kg. Histological and electron microscopical analyses of the plaques showed USPIOs primarily in macrophages within the plaques in 10 of 11 patients. Histological analysis showed USPIOs in 27 of 36 (75%) of the ruptured and rupture-prone lesions and 1 of 14 (7%) of the stable lesions. Of the patients with USPIO uptake, signal changes in the post-USPIO MRI were observed by 2 observers in the vessel wall in 67 of 123 (54%) and 19 of 55 (35%) quadrants of the T2*-weighted MR images acquired after 24 and 72 hours, respectively. For those quadrants with changes, there was a significant signal decrease of 24% (95% CI, 33% to 15%) in regions of interest in the images acquired after 24 hours, whereas no significant signal change was found after 72 hours.

CONCLUSIONS

Accumulation of USPIOs in macrophages in predominantly ruptured and rupture-prone human atherosclerotic lesions caused signal decreases in the in vivo MR images.

Mechanisms of cell death in acute myocardial infarction: pathophysiological implications for treatment

The purpose of this review is to draw attention to the growing list of pathophysiological phenomena occurring in blood, the vessel wall and cardiac tissue during myocardial infarction. A further aim is to point to the complexity of factors, contributing to cardiac dysfunction and the implications for therapy, aimed at limiting myocardial cell death. Not all pathophysiological mechanisms have been elucidated yet, indicating the necessity for further research in this area. In addition we describe interventions which have shown promise in animal studies, those which may show promise in humans, and those which are accepted as therapies of choice.