Cardiac remodeling—concepts and clinical implications: a consensus paper from an international forum on cardiac remodeling

Healing of myocardial infarction (MI) requires monocytes/macrophages These mononuclear phagocytes likely degrade released macromolecules and aid in scavenging of dead cardiomyocytes, while mediating aspects of granulation tissue formation and remodeling The mechanisms that orchestrate such divergent functions remain unknown In view of the heightened appreciation of the heterogeneity of circulating monocytes, we investigated whether distinct monocyte subsets contribute in specific ways to myocardial ischemic injury in mouse MI We identify two distinct phases of monocyte participation after MI and propose a model that reconciles the divergent properties of these cells in healing Infarcted hearts modulate their chemokine expression profile over time, and they sequentially and actively recruit Ly-6Chi and -6Clo monocytes via CCR2 and CX3CR1, respectively Ly-6Chi monocytes dominate early (phase I) and exhibit phagocytic, proteolytic, and inflammatory functions Ly-6Clo monocytes dominate later (phase II), have attenuated inflammatory properties, and express vascular–endothelial growth factor Consequently, Ly-6Chi monocytes digest damaged tissue, whereas Ly-6Clo monocytes promote healing via myofibroblast accumulation, angiogenesis, and deposition of collagen MI in atherosclerotic mice with chronic Ly-6Chi monocytosis results in impaired healing, underscoring the need for a balanced and coordinated response These observations provide novel mechanistic insights into the cellular and molecular events that regulate the response to ischemic injury and identify new therapeutic targets that can influence healing and ventricular remodeling after MI

https://rupress.org/jem/article-pdf/204/12/3037/1160364/jem_20070885.pdf

The healing myocardium sequentially mobilizes two monocyte subsets with divergent and complementary functions

Chronic kidney disease (CKD) is a worldwide public health problem associated with a high prevalence of cardiovascular disease (CVD) and impaired quality of life. Previous research for preventing loss of glomerular filtration rate (GFR) has focused on reducing blood pressure (BP) and proteinuria. Angiotensin converting enzyme inhibitors (ACEi) and angiotensin II receptor antagonists (ARB) are commonly used in patients with early CKD, but their value in advanced CKD (estimated GFR (eGFR) ≤30 ml/min/1.73 m2) is unknown. There remains a debate about the omission of ACEi/ARB in patients with advanced CKD and their use in association with CVD or heart failure. Does the potential gain in eGFR with ACEi/ARB cessation outweigh the potential adverse cardiovascular outcomes? This paper reviews the current literature that addresses this issue. Several controversies are discussed. Although lowering BP reduces cardiovascular events, evidence suggests that ACEi/ARBs are not superior to other antihypertensive agents. There are no studies assessing the benefits of ACEi/ARB therapy in cardiovascular risk reduction in advanced non-dialysis CKD. The STOP ACEi trial will strengthen the evidence base and shed light on the potential merits and dangers of ACEi/ARB use in advanced CKD on renal function and cardiovascular outcomes.

Should We STOP Angiotensin Converting Enzyme Inhibitors/Angiotensin Receptor Blockers in Advanced Kidney Disease?

https://www.thelancet.com/pdfs/journals/lancet/PIIS0140-6736(05)67861-0.pdf

Autologous bone marrow-derived stem-cell transfer in patients with ST-segment elevation myocardial infarction: double-blind, randomised controlled trial.

In adult mammals, massive sudden loss of cardiomyocytes after infarction overwhelms the limited regenerative capacity of the myocardium, resulting in the formation of a collagen-based scar. Necrotic cells release danger signals, activating innate immune pathways and triggering an intense inflammatory response. Stimulation of toll-like receptor signaling and complement activation induces expression of proinflammatory cytokines (such as interleukin-1 and tumor necrosis factor-α) and chemokines (such as monocyte chemoattractant protein-1/ chemokine (C-C motif) ligand 2 [CCL2]). Inflammatory signals promote adhesive interactions between leukocytes and endothelial cells, leading to extravasation of neutrophils and monocytes. As infiltrating leukocytes clear the infarct from dead cells, mediators repressing inflammation are released, and anti-inflammatory mononuclear cell subsets predominate. Suppression of the inflammatory response is associated with activation of reparative cells. Fibroblasts proliferate, undergo myofibroblast transdifferentiation, and deposit large amounts of extracellular matrix proteins maintaining the structural integrity of the infarcted ventricle. The renin–angiotensin–aldosterone system and members of the transforming growth factor-β family play an important role in activation of infarct myofibroblasts. Maturation of the scar follows, as a network of cross-linked collagenous matrix is formed and granulation tissue cells become apoptotic. This review discusses the cellular effectors and molecular signals regulating the inflammatory and reparative response after myocardial infarction. Dysregulation of immune pathways, impaired suppression of postinfarction inflammation, perturbed spatial containment of the inflammatory response, and overactive fibrosis may cause adverse remodeling in patients with infarction contributing to the pathogenesis of heart failure. Therapeutic modulation of the inflammatory and reparative response may hold promise for the prevention of postinfarction heart failure.

/pdf/the-biological-basis-for-cardiac-repair-after-myocardial-198isjzhg7.pdf

The Biological Basis for Cardiac Repair After Myocardial Infarction: From Inflammation to Fibrosis

Left ventricular remodeling is the process by which ventricular size, shape, and function are regulated by mechanical, neurohormonal, and genetic factors.1 2 Remodeling may be physiological and adaptive during normal growth or pathological due to myocardial infarction, cardiomyopathy, hypertension, or valvular heart disease (Figure 1⇓). This article will review postinfarction remodeling, pathophysiological mechanisms, and therapeutic intervention.



 Figure 1. 
Diagrammatic representation of the many factors involved in the pathophysiology of ventricular remodeling. ECM indicates extracellular matrix; RAAS, renin-angiotensin-aldosterone system; CO, cardiac output; SVR, systemic vascular resistance; LV, left ventricular; and AII, angiotensin II.



### Postinfarction Left Ventricular Remodeling

The acute loss of myocardium results in an abrupt increase in loading conditions that induces a unique pattern of remodeling involving the infarcted border zone and remote noninfarcted myocardium. Myocyte necrosis and the resultant increase in load trigger a cascade of biochemical intracellular signaling processes that initiates and subsequently modulates reparative changes, which include dilatation, hypertrophy, and the formation of a discrete collagen scar. Ventricular remodeling may continue for weeks or months until the distending forces are counterbalanced by the tensile strength of the collagen scar. This balance is determined by the size, location, and transmurality of the infarct, the extent of myocardial stunning, the patency of the infarct-related artery, and local tropic factors.1 3 

The myocardium consists of 3 integrated components: myocytes, extracellular matrix, and the capillary microcirculation that services the contractile unit assembly. Consideration of all 3 components provides important insights into the remodeling process and a rationale for future therapeutic strategies. The cardiomyocyte is terminally differentiated and develops tension by shortening. The extracellular matrix provides a stress-tolerant, viscoelastic scaffold consisting of type I and type III collagen that couples myocytes and maintains the spatial relations between the myofilaments and their capillary microcirculation.4 5 The collagen framework couples adjacent myocytes by intercellular struts that …

Norman Sharpe

Papers

Left Ventricular Remodeling After Myocardial Infarction Pathophysiology and Therapy