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Advances in cardiovascular research have identified oxidative stress as an important pathophysiological pathway in the development and progression of heart failure. Oxidative stress is defined as the imbalance between the production of reactive oxygen species (ROS) and the endogenous antioxidant defence system. Under physiological conditions, small quantities of ROS are produced intracellularly, which function in cell signalling, and can be readily reduced by the antioxidant defence system. However, under pathophysiological conditions, the production of ROS exceeds the buffering capacity of the antioxidant defence system, resulting in cell damage and death. Over the last decades several studies have tried to target oxidative stress with the aim to improve outcome in patients with heart failure, with very limited success. The reasons as to why these studies failed to demonstrate any beneficial effects remain unclear. However, one plausible explanation might be that currently employed strategies, which target oxidative stress by exogenous inhibition of ROS production or supplementation of exogenous antioxidants, are not effective enough, while bolstering the endogenous antioxidant capacity might be a far more potent avenue for therapeutic intervention. In this review, we provide an overview of oxidative stress in the pathophysiology of heart failure and the strategies utilized to date to target this pathway. We provide novel insights into modulation of endogenous antioxidants, which may lead to novel therapeutic strategies to improve outcome in patients with heart failure.

Tissue homeostasis is perturbed by stressful events, which can lead to organ dysfunction and failure. This is particularly true for the heart, where injury resulting from myocardial infarction or ischemic heart disease can result in a cascading event ultimately ending with the loss of functional myocardial tissue and heart failure. To help reverse this loss of healthy contractile tissue, researchers have spent decades in the hopes of characterizing a cell source capable of regenerating the injured heart. Unfortunately, these strategies have proven to be ineffective. With the goal of truly understanding cardiac regeneration, researchers have focused on the innate regenerative abilities of zebrafish and neonatal mammals. This has led to the realization that although cells play an important role in the repair of the diseased myocardium, inducing cardiac regeneration may instead lie in the composition of the extra cellular milieu, specifically the extra cellular matrix. In this review we will briefly summarize the current knowledge regarding cell sources used for cardiac regenerative approaches, since these have been extensively reviewed elsewhere. More importantly, by revisiting innate cardiac regeneration observed in zebrafish and neonatal mammals, we will stress the importance the extra cellular matrix has on reactivating this potential in the adult myocardium. Finally, we will address how we can harness the ability of the extra cellular matrix to guide cardiac repair thereby setting the stage of next generation regenerative strategies.

Aims The prevalence of heart failure with a preserved ejection fraction (HFpEF) is increasing, but therapeutic options are limited. Oxidative stress is suggested to play an important role in the pathophysiology of HFpEF. However, whether oxidative stress is a bystander due to comorbidities or causative in itself remains unknown. Recent results have shown that depletion of 5-oxoprolinase (OPLAH) leads to 5-oxoproline accumulation, which is an important mediator of oxidative stress in the heart. We hypothesize that oxidative stress induced by elevated levels of 5-oxoproline leads to the onset of a murine HFpEF-like phenotype.Methods and results Oplah full body knock-out (KO) mice had higher 5-oxoproline levels coupled to increased oxidative stress. Compared with wild-type (WT) littermates, KO mice had increased cardiac and renal fibrosis with concurrent elevated left ventricular (LV) filling pressures, impaired LV relaxation, yet a normal LV ejection fraction. Following the induction of cardiac ischaemia/reperfusion (IR) injury, 52.4% of the KO mice died compared with only 15.4% of the WT mice (P Conclusion Oxidative stress induced by 5-oxoproline results in a murine phenotype reminiscent of the clinical manifestation of HFpEF without the need for surgical or pharmacological interference. Better understanding of the role of oxidative stress in HFpEF may potentially lead to novel therapeutic options.

Background— Syndecan-1 is a member of the proteoglycan family involved in cell–matrix interactions. Experimental studies showed that syndecan-1 is associated with inflammation in acute myocardial infarction and remodeling. The goal of this study was to explore the role of syndecan-1 in human heart failure (HF). Methods and Results— We analyzed plasma syndecan-1 levels in 567 patients with chronic HF. Primary end point was a composite of all-cause mortality and rehospitalization for HF at 18 months. Mean age was 71.0±11.0 years, 38% was women, and mean left ventricular ejection fraction was 32.5±14.0%. Median syndecan-1 levels were 20.1 ng/mL (interquartile range, 13.9–27.7 ng/mL). Patients with higher syndecan-1 levels were more often men, had higher N-terminal probrain-type natriuretic peptide levels, and worse renal function. Multivariable regression analyses showed a positive correlation between syndecan-1 levels and markers of fibrosis and remodeling but no correlation with inflammation markers. Interaction analysis revealed an interaction between left ventricular ejection fraction and syndecan-1 ( P =0.047). A doubling of syndecan-1 was associated with an increased risk of the primary outcome in patients with HF with preserved ejection fraction (hazard ratio, 2.10; 95% confidence interval, 1.14–3.86; P =0.017) but not in patients with HF with reduced ejection fraction (hazard ratio, 0.95; 95% confidence interval, 0.71–1.27; P =0.729). Finally, syndecan-1 enhanced risk classification in patients with HF with preserved ejection fraction when added to a prediction model with established risk factors. Conclusions— In patients with HF, syndecan-1 levels correlate with fibrosis biomarkers pointing toward a role in cardiac remodeling. Syndecan-1 was associated with clinical outcome in patients with HF with preserved ejection fraction but not in patients with HF with reduced ejection fraction.