Nr4a1 modulates inflammation and heart regeneration in zebrafish.

Recent findings have highlighted the complex role of inflammation in zebrafish heart regeneration, demonstrating that although inflammation is essential for initiating transient fibrosis and tissue repair, chronic inflammation, and unresolved fibrosis, could impede full regenerative recovery. In this study, we identified the nuclear receptor Nr4a1 as a crucial regulator of this regenerative process in zebrafish. Loss of Nr4a1 function led to a prolonged and excessive inflammatory response, disrupted neutrophil migration, delayed fibrin clearance, and ultimately impaired heart regeneration. Transcriptome-wide RNA-seq analysis at different injury stages revealed molecular disruptions associated with dysregulated inflammation and fibrosis in nr4a1 mutants. Notably, partial inhibition of the pro-inflammatory cytokine Tnfα rescued heart regeneration in the nr4a1 mutants, highlighting the therapeutic potential of modulating inflammation. Our findings suggest that Nr4a1 plays a crucial role in orchestrating the immune response during heart regeneration and may serve as a valuable target for enhancing cardiac repair following injury.