Anna-Pia Papageorgiou

Macrophage MicroRNA-155 Promotes Cardiac Hypertrophy and Failure

Background— Cardiac hypertrophy and subsequent heart failure triggered by chronic hypertension represent major challenges for cardiovascular research. Beyond neurohormonal and myocyte signaling pathways, growing evidence suggests inflammatory signaling pathways as therapeutically targetable contributors to this process. We recently reported that microRNA-155 is a key mediator of cardiac inflammation and injury in infectious myocarditis. Here, we investigated the impact of microRNA-155 manipulation in hypertensive heart disease. Methods and Results— Genetic loss or pharmacological inhibition of the leukocyte-expressed microRNA-155 in mice markedly reduced cardiac inflammation, hypertrophy, and dysfunction on pressure overload. These alterations were macrophage dependent because in vivo cardiomyocyte-specific microRNA-155 manipulation did not affect cardiac hypertrophy or dysfunction, whereas bone marrow transplantation from wild-type mice into microRNA-155 knockout animals rescued the hypertrophic response of the cardiomyocytes and vice versa. In vitro, media from microRNA-155 knockout macrophages blocked the hypertrophic growth of stimulated cardiomyocytes, confirming that macrophages influence myocyte growth in a microRNA-155-dependent paracrine manner. These effects were at least partly mediated by the direct microRNA-155 target suppressor of cytokine signaling 1 (Socs1) because Socs1 knockdown in microRNA-155 knockout macrophages largely restored their hypertrophy-stimulating potency. Conclusions— Our findings reveal that microRNA-155 expression in macrophages promotes cardiac inflammation, hypertrophy, and failure in response to pressure overload. These data support the causative significance of inflammatory signaling in hypertrophic heart disease and demonstrate the feasibility of therapeutic microRNA targeting of inflammation in heart failure.

MicroRNA Profiling Identifies MicroRNA-155 as an Adverse Mediator of Cardiac Injury and Dysfunction During Acute Viral Myocarditis

Rationale: Viral myocarditis results from an adverse immune response to cardiotropic viruses, which causes irreversible myocyte destruction and heart failure in previously healthy people. The involvement of microRNAs and their usefulness as therapeutic targets in this process are unknown. Objective: To identify microRNAs involved in viral myocarditis pathogenesis and susceptibility. Methods and Results: Cardiac microRNAs were profiled in both human myocarditis and in Coxsackievirus B3-injected mice, comparing myocarditis-susceptible with nonsusceptible mouse strains longitudinally. MicroRNA responses diverged depending on the susceptibility to myocarditis after viral infection in mice. MicroRNA-155, -146b, and -21 were consistently and strongly upregulated during acute myocarditis in both humans and susceptible mice. We found that microRNA-155 expression during myocarditis was localized primarily in infiltrating macrophages and T lymphocytes. Inhibition of microRNA-155 by a systemically delivered LNA-anti-miR attenuated cardiac infiltration by monocyte-macrophages, decreased T lymphocyte activation, and reduced myocardial damage during acute myocarditis in mice. These changes were accompanied by the derepression of the direct microRNA-155 target PU.1 in cardiac inflammatory cells. Beyond the acute phase, microRNA-155 inhibition reduced mortality and improved cardiac function during 7 weeks of follow-up. Conclusions: Our data show that cardiac microRNA dysregulation is a characteristic of both human and mouse viral myocarditis. The inflammatory microRNA-155 is upregulated during acute myocarditis, contributes to the adverse inflammatory response to viral infection of the heart, and is a potential therapeutic target for viral myocarditis.

Searching for new mechanisms of myocardial fibrosis with diagnostic and/or therapeutic potential

Myocardial fibrosis is the result of excessive fibrillar collagen synthesis and deposition without reciprocally balanced degradation. It causes cardiac dysfunction, arrhythmias, and ischaemia, and thereby determines the clinical course and outcome of cardiac patients even when adequately treated. Therefore, further research is needed to identify and better understand the factors that trigger and maintain the myocardial fibrotic response against different injuries in a variety of cardiac diseases. Here, we will focus on the following major areas of research: molecules that stimulate the differentiation of fibroblasts into myofibroblasts and subsequently alter collagen turnover (e.g. cardiotrophin‐1, galectin‐3, NADPH oxidases, and neutrophil gelatinase‐associated lipocalin), microRNA‐induced alterations of collagen gene expression, and matricellular protein‐ and lysyl oxidase‐mediated alterations of collagen cross‐linking and deposition.

Osteoglycin Prevents Cardiac Dilatation and Dysfunction After Myocardial Infarction Through Infarct Collagen Strengthening

Rationale: To maintain cardiac mechanical and structural integrity after an ischemic insult, profound alterations occur within the extracellular matrix. Osteoglycin is a small leucine-rich proteoglycan previously described as a marker of cardiac hypertrophy. Objective: To establish whether osteoglycin may play a role in cardiac integrity and function after myocardial infarction (MI). Methods and Results: Osteoglycin expression is associated with collagen deposition and scar formation in mouse and human MI. Absence of osteoglycin in mice resulted in significantly increased rupture-related mortality with tissue disruption, intramyocardial bleeding, and increased cardiac dysfunction, despite equal infarct sizes. Surviving osteoglycin null mice had greater infarct expansion in comparison with wild-type mice because of impaired collagen fibrillogenesis and maturation in the infarcts as revealed by electron microscopy and collagen polarization. Absence of osteoglycin did not affect cardiomyocyte hypertrophy in the remodeling remote myocardium. In cultured fibroblasts, osteoglycin knockdown or supplementation did not alter transforming growth factor-&bgr; signaling. Adenoviral overexpression of osteoglycin in wild-type mice significantly improved collagen quality, thereby blunting cardiac dilatation and dysfunction after MI. In osteoglycin null mice, adenoviral overexpression of osteoglycin was unable to prevent rupture-related mortality because of insufficiently restoring osteoglycin protein levels in the heart. Finally, circulating osteoglycin levels in patients with heart failure were significantly increased in the patients with a previous history of MI compared with those with nonischemic heart failure and correlated with survival, left ventricular volumes, and other markers of fibrosis. Conclusions: Increased osteoglycin expression in the infarct scar promotes proper collagen maturation and protects against cardiac disruption and adverse remodeling after MI. In human heart failure, osteoglycin is a promising biomarker for ischemic heart failure.

Thrombospondin-2 prevents cardiac injury and dysfunction in viral myocarditis through the activation of regulatory T-cells

AIMS Thrombospondin-2 (TSP-2) modulates matrix integrity and myocyte survival in the hypertensive or ageing heart. Whether TSP-2 may affect cardiac inflammation and injury, in particular during acute viral myocarditis, is completely unknown. METHODS AND RESULTS Therefore, mortality, cardiac inflammation, and function were assessed in TSP-2-null (KO) and wild-type (WT) mice in human Coxsackie virus B3 (CVB3)-induced myocarditis. TSP-2 KO had an increased mortality when compared with WT mice during viral myocarditis. The absence of TSP-2 resulted in increased cardiac inflammation and injury at 14 days, which resulted in depressed systolic function [fractional shortening (FS); 34 ± 2.6 in WT vs. 24 ± 1.8 in KO mice, P< 0.05] and increased cardiac dilatation (end-diastolic dimensions, mm; 3.7 ± 0.09 in WT vs. 4.8 ± 0.06 in KO mice, P< 0.05) 35 days post-infection. Lack of TSP-2 resulted in a decreased activation of the anti-inflammatory T-regulatory cells, as indicated by a lower number of CD25-positive T-cells, and significantly decreased gene expression of regulatory T-cell markers, Foxp3 and CTLA-4. Finally, overexpression of TSP-2 in WT hearts using cardiotropic vectors derived from adeno-associated virus serotype 9 (AAV9) inhibited cardiac inflammation and injury at 14 days and improved cardiac function at 35 days post-CVB3 infection when compared with control AAV9. CONCLUSION TSP-2 has a protective role against cardiac inflammation, injury, and dysfunction in acute viral myocarditis.

RNA Profiling in Human and Murine Transplanted Hearts: Identification and Validation of Therapeutic Targets for Acute Cardiac and Renal Allograft Rejection

Acute cellular rejection (ACR) is the adverse response of the recipients immune system against the allogeneic graft. Using human surveillance endomyocardial biopsies (EMBs) manifesting ACR and murine allogeneic grafts, we profiled implicated microRNAs (miRs) and mRNAs. MiR profiling showed that miR‐21, ‐142‐3p, ‐142‐5p, ‐146a, ‐146b, ‐155, ‐222, ‐223, and ‐494 increased during ACR in humans and mice, whereas miR‐149‐5p decreased. mRNA profiling revealed 70 common differentially regulated transcripts, all involved in immune signaling and immune‐related diseases. Interestingly, 33 of 70 transcripts function downstream of IL‐6 and its transcription factor spleen focus forming virus proviral integration oncogene (SPI1), an established target of miR‐155, the most upregulated miR in human EMBs manifesting rejection. In a mouse model of cardiac transplantation, miR‐155 absence and pharmacological inhibition attenuated ACR, demonstrating the causal involvement and therapeutic potential of miRs. Finally, we corroborated our miR signature in acute cellular renal allograft rejection, suggesting a nonorgan specific signature of acute rejection. We concluded that miR and mRNA profiling in human and murine ACR revealed the shared significant dysregulation of immune genes. Inflammatory miRs, for example miR‐155, and transcripts, in particular those related to the IL‐6 pathway, are promising therapeutic targets to prevent acute allograft rejection.

The microRNA-221/-222 cluster balances the antiviral and inflammatory response in viral myocarditis.

AIMS Viral myocarditis (VM) is an important cause of heart failure and sudden cardiac death in young healthy adults; it is also an aetiological precursor of dilated cardiomyopathy. We explored the role of the miR-221/-222 family that is up-regulated in VM. METHODS AND RESULTS Here, we show that microRNA-221 (miR-221) and miR-222 levels are significantly elevated during acute VM caused by Coxsackievirus B3 (CVB3). Both miRs are expressed by different cardiac cells and by infiltrating inflammatory cells, but their up-regulation upon myocarditis is mostly exclusive for the cardiomyocyte. Systemic inhibition of miR-221/-222 in mice increased cardiac viral load, prolonged the viraemic state, and strongly aggravated cardiac injury and inflammation. Similarly, in vitro, overexpression of miR-221 and miR-222 inhibited enteroviral replication, whereas knockdown of this miR-cluster augmented viral replication. We identified and confirmed a number of miR-221/-222 targets that co-orchestrate the increased viral replication and inflammation, including ETS1/2, IRF2, BCL2L11, TOX, BMF, and CXCL12. In vitro inhibition of IRF2, TOX, or CXCL12 in cardiomyocytes significantly dampened their inflammatory response to CVB3 infection, confirming the functionality of these targets in VM and highlighting the importance of miR-221/-222 as regulators of the cardiac response to VM. CONCLUSIONS The miR-221/-222 cluster orchestrates the antiviral and inflammatory immune response to viral infection of the heart. Its inhibition increases viral load, inflammation, and overall cardiac injury upon VM.

STAT3 activity is necessary and sufficient for the development of immune-mediated myocarditis in mice and promotes progression to dilated cardiomyopathy

Myocarditis, often triggered by viral infection, may lead to heart auto‐immunity and dilated cardiomyopathy. What determines the switch between disease resolution and progression is however incompletely understood. We show that pharmacological inhibition of STAT3, the main mediator of IL‐6 signalling and of Th17‐cell differentiation, protects mice from the development of Experimental Auto‐immune Myocarditis reducing liver production of the complement component C3, and can act therapeutically when administered at disease peak. Further, we demonstrate that STAT3 is sufficient when constitutively active for triggering the onset of immune‐mediated myocarditis, involving enhanced complement C3 production and IL‐6 signalling amplification in the liver. Disease development can be prevented by C3 depletion and IL‐6 receptor neutralization. This appears to be relevant to disease pathogenesis in humans, since acute myocarditis patients display significantly elevated circulating IL‐6 and C3 levels and activated heart STAT3. Thus, aberrant IL‐6/STAT3‐mediated induction of liver acute phase response genes including C3, which occurs as a consequence of pre‐existing inflammatory conditions, might represent an important factor determining the degree of myocarditis and its clinical outcome.

Novel regulators of cardiac inflammation: Matricellular proteins expand their repertoire.

More than 20years ago, Paul Bornstein coined the term matricellular protein to describe a group of secreted extracellular matrix proteins with de-adhesive properties. Though this is still true today, this family of proteins is vastly expanding with new emerging functions pushing the boundaries of this classic definition. In the heart, matricellular proteins have been extensively investigated in models of myocardial infarction, pressure overload, viral myocarditis and age-related cardiomyopathy with clear implications during cardiac fibrosis yet their involvement in regulating cardiac inflammation is less established. In this review, we describe our current understanding of the immune activation by damage- or pathogen-associated molecular pattern molecules during cardiac injury making a distinction between sterile versus non-sterile cardiac inflammation, and explain how matricellular proteins influence this crucial pathophysiological response in the heart.

Matricellular proteins and matrix metalloproteinases mark the inflammatory and fibrotic response in human cardiac allograft rejection

Aims The cardiac extracellular matrix is highly involved in regulating inflammation, remodelling, and function of the heart. Whether matrix alterations relate to the degree of inflammation, fibrosis, and overall rejection in the human transplanted heart remained, until now, unknown. Methods and results Expression of matricellular proteins, proteoglycans, and metalloproteinases (MMPs) and their inhibitors (TIMPs) were investigated in serial endomyocardial biopsies (n = 102), in a cohort of 39 patients within the first year after cardiac transplantation. Out of 15 matrix-related proteins, intragraft transcript and protein levels of syndecan-1 and MMP-9 showed a strong association with the degree of cardiac allograft rejection (CAR), the expression of pro-inflammatory cytokines tumour necrosis factor (TNF)-α, interleukin (IL)-6 and transforming growth factor (TGF)-β, and with infiltrating CD3+T-cells and CD68+monocytes. In addition, SPARC, CTGF, TSP-2, MMP-14, TIMP-1, Testican-1, TSP-1, Syndecan-1, MMP-2, -9, and -14, as well as IL-6 and TGF-β transcript levels and inflammatory infiltrates all strongly relate to collagen expression in the transplanted heart. More importantly, receiver operating characteristic curve analysis demonstrated that syndecan-1 and MMP-9 transcript levels had the highest area under the curve (0.969 and 0.981, respectively), thereby identifying both as a potential decision-making tool to discriminate rejecting from non-rejecting hearts. Conclusion Out of 15 matrix-related proteins, we identified synd-1 and MMP-9 intragraft transcript levels of as strong predictors of human CAR. In addition, a multitude of non-structural matrix-related proteins closely associate with collagen expression in the transplanted heart. Therefore, we are convinced that these findings deserve further investigation and are likely to be of clinical value to prevent human CAR.