Neonatal mammals exhibit a remarkable capacity for cardiac repair that declines rapidly after birth and continues to diminish with age. This loss of regenerative potential is accompanied by age-dependent changes in macrophage behavior, shifting from pro-regenerative to pro-fibrotic responses following injury. We investigated whether extracellular matrix (ECM)-derived matrikines from different developmental ages regulate macrophage polarization. Cardiac ECM was isolated from neonatal (P2), adolescent (6-week), and adult (16-20-week) rat hearts through decellularization and pepsin digestion. ECM peptides were adsorbed onto tissue culture surfaces, and murine RAW 264.7 macrophages were cultured on ECM-coated or uncoated controls. After 24 hours, macrophage phenotype and gene expression were assessed using marker analysis and RNA sequencing. Macrophages cultured on neonatal cardiac ECM displayed reduced inflammatory activation and maintained expression of pro-reparative markers, even in the presence of inflammatory stimuli. Transcriptomic analysis revealed a distinct ECM-driven phenotype that differed from canonical M1 and M2 polarization states. Gene ontology analysis demonstrated significant downregulation of pathways associated with antiviral responses, immune activation, and interferon signaling in macrophages exposed to neonatal ECM. These effects were not observed with adolescent or adult ECM. Collectively, these findings suggest that neonatal ECM matrikines suppress interferon-mediated inflammatory signaling, potentially contributing to the reduced inflammation and enhanced repair observed following myocardial injury in neonatal hearts.
Nugnes, K., Costello, G., McCarey, N., Canas, E., Black, L. D.
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