Cardiac fibrosis: mechanistic insights and translational advances.

Cardiac fibrosis is a critical pathological process driving the progression of heart failure, characterized by excessive extracellular matrix deposition, collagen network remodeling, and expansion of the myocardial interstitium. While fibrosis may reflect a reparative response to tissue injury, it can also signify a maladaptive remodeling process that progressively impairs cardiac structure and function. Cardiac fibroblasts and myofibroblasts serve as the principal effector cells responsible for matrix accumulation, whereas cardiomyocytes and immune cells contribute to fibrotic expansion through inflammatory signaling, paracrine communication, and microenvironmental regulation. Transforming growth factor-β, the renin-angiotensin-aldosterone system, inflammatory cytokines, mechanical stress, and metabolic disturbances collectively orchestrate a profibrotic signaling network. By regulating extracellular matrix synthesis, degradation, and crosslinking, these pathways promote myocardial stiffening and functional decompensation. In this review, we discuss the histopathological patterns of cardiac fibrosis across various pathological contexts, the major cellular contributors, and the core molecular mechanisms involved, while summarizing current advances in diagnostic evaluation and translational therapeutic strategies. We further discuss the context-dependent role of sirtuin 3 (SIRT3), a mitochondrial nicotinamide adenine dinucleotide (NAD⁺)-dependent deacetylase, in linking mitochondrial homeostasis, oxidative stress, metabolic adaptation, and profibrotic signaling. More precise antifibrotic strategies require better definition of fibroblast states, fibrosis activity, and disease-specific remodeling patterns.