Histaminylation alters collagen matrix mechanics and attenuates cardiac fibrosis post-myocardial infarction via mechanotransduction signaling axis

Abstract Histaminylation is a newly discovered monoaminylation catalyzed by transglutaminase 2 (TGM2), and its role in myocardial fibrosis has not yet been elucidated. Here, we identified histaminylation in cardiac type I collagen isolated from mice 7 days after acute myocardial infarction (AMI) by mass spectrometry. Using histamine-deficient Hdc −/− mice, we demonstrated an increase in TGM2-mediated γ-glutamyl-ε-lysine crosslinks and a higher myocardial Young’s modulus in the scar region of Hdc −/− mice than in wild-type controls, indicating that histaminylation might restrain the role of TGM2 in cardiac fibrogenesis after AMI. Furthermore, we reconstituted an in vitro crosslinking system, yielding unmodified collagen and histaminylated collagen. The results of mechanical indentation and electron microscopy demonstrated that histaminylation could reduce crosslink formation, lower matrix stiffness, and alter viscoelasticity. Subsequently, primary murine cardiac fibroblasts were cultured under cyclic stretch with TGF-β on different substrates, and the results revealed that histaminylated collagen strongly attenuated TGF-β-induced fibroblast-to-myofibroblast transition and reduced focal adhesion assembly. Mechanically, integrated single-cell and bulk RNA-seq analyses indicated that the PIEZO1/ITGB1 mechanotransduction axis was upregulated and mediated downstream signal transduction in the infarcted hearts of Hdc −/− mice. Finally, local delivery of a histamine-releasing hydrogel to Hdc −/− mice after AMI could significantly reinstate collagen histaminylation and reduce crosslink abundance and cardiac dysfunction. Collectively, these data reveal that collagen histaminylation limits TGM2-dependent crosslinking, softens the extracellular matrix, and inhibits the PIEZO1/ITGB1 axis, thereby mitigating myocardial fibrosis after AMI. This study also highlights a novel role of histamine in maintaining stress environment mechanical stability.