Cellular Mechanisms of Tissue Fibrosis. 2. Contributory pathways leading to myocardial fibrosis: moving beyond collagen expression

Abstract

While the term "fibrosis" can be misleading in terms of the complex patterns and processes of myocardial extracellular matrix (ECM) remodeling, fibrillar collagen accumulation is a common consequence of relevant pathophysiological stimuli, such as pressure overload (PO) and myocardial infarction (MI). Fibrillar collagen accumulation in both PO and MI is predicated on a number of diverse cellular and extracellular events, which include changes in fibroblast phenotype (transdifferentiation), posttranslational processing and assembly, and finally, degradation. The expansion of a population of transformed fibroblasts/myofibroblasts is a significant cellular event with respect to ECM remodeling in both PO and MI. The concept that this cellular expansion within the myocardial ECM may be due, at least in part, to endothelial-mesenchymal transformation and thereby not dissimilar to events observed in cancer progression holds intriguing future possibilities. Studies regarding determinants of procollagen processing, such as procollagen C-endopeptidase enhancer (PCOLCE), and collagen assembly, such as the secreted protein acidic and rich in cysteine (SPARC), have identified potential new targets for modifying the fibrotic response in both PO and MI. Finally, the transmembrane matrix metalloproteinases, such as MMP-14, underscore the diversity and complexity of this ECM proteolytic family as this protease can degrade the ECM as well as induce a profibrotic response. The growing recognition that the myocardial ECM is a dynamic entity containing a diversity of matricellular and nonstructural proteins as well as proteases and that the fibrillar collagens can change in structure and content in a rapid temporal fashion has opened up new avenues for modulating what was once considered an irreversible event--myocardial fibrosis.

Severe Pneumococcal Pneumonia Causes Acute Cardiac Toxicity and Subsequent Cardiac Remodeling

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Innate immune signaling induces expression and shedding of the heparan sulfate proteoglycan syndecan‐4 in cardiac fibroblasts and myocytes, affecting inflammation in the pressure‐overloaded heart

“…On the other hand, these cultures contain fibroblasts at different stages of myofibroblast differentiation, similar to what is observed in the pressure-overloaded heart in vivo. 157,159 Although neonatal cardiac cell cultures have shortcomings as model systems for the adult heart, they provide a controlled environment to study direct effects of physical or biochemical interventions on a specific cell type and are highly valued in cardiac research. In light of this, we used the primary cell cultures to investigate whether the matrix molecules we found to be upregulated in the diseased heart may act in an auto-or paracrine fashion to convey signaling effects on cardiac cells.…”

MicroRNA‐30c suppresses the pro‐fibrogenic effects of cardiac fibroblasts induced by TGF‐β1 and prevents atrial fibrosis by targeting TGFβRII

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