Psoralen enhances direct cardiac reprogramming via activating PPARα and driving mitochondrial fission and improves cardiac function after myocardial infarction.

backgroundDirect cardiac reprogramming offers a promising strategy to regenerate cardiomyocytes for heart repair, but its efficiency and maturation remain limited. Psoralen, a natural compound isolated from Psoralea corylifolia L., has been widely studied for its bioactive properties. This study aimed to determine whether psoralen enhances chemical cardiac reprogramming and improves functional maturation, and to evaluate its therapeutic potential in myocardial infarction.

methodsMouse embryonic fibroblasts were treated with a chemical reprogramming cocktail containing RepSox and Forskolin, with or without psoralen. Gene expression was assessed by quantitative PCR and Western blotting. Sarcomere ultrastructure was examined by transmission electron microscopy. Mitochondrial content and morphology were analyzed using MitoTracker staining. Calcium handling was evaluated in Fluo-4 loaded induced cardiomyocytes. Metabolic profiles were measured with Seahorse assays. RNA sequencing and protein-protein interaction analysis were used to identify signaling pathways activated by psoralen. To investigate the functional role of mitochondrial fission in psoralen enhanced reprogramming, the DRP1 inhibitor Mdivi-1 was added to the reprogramming cocktail. An immortalized human skin fibroblast cell line was additionally used to evaluate cardiac marker expression and mitochondrial morphology following treatment with RepSox, Forskolin, and psoralen. For in vivo evaluation, a myocardial infarction model was generated in male C57BL/6J mice, which were subsequently treated for 7 days. Cardiac function was measured by echocardiography, and histological changes were assessed by HE and Masson's trichrome staining.

resultsPsoralen (10 µM) significantly increased the induction efficiency of induced cardiomyocytes, leading to the rapid appearance of beating clusters(day 1 vs. day 6-8) and marked upregulation of cardiac structural genes. Psoralen-treated cells displayed enhanced sarcomere organization, improved calcium transients, and a metabolic shift toward oxidative phosphorylation characterized by higher mitochondrial respiration and reduced glycolysis. Transcriptomic profiling identified activation of the PPAR signaling pathway, with PPARα, RXRG, and UCP1 as central nodes. Psoralen also enhanced mitochondrial fission by upregulating fission-related genes and proteins. Mdivi-1 attenuated psoralen-induced cardiac gene expression and mitochondrial fragmentation. In immortalized human skin fibroblasts, psoralen combined with RepSox and Forskolin increased cardiac marker expression and promoted mitochondrial fragmentation. In vivo, psoralen combined with RepSox and Forskolin enhanced cardiac function and reduced fibrosis after myocardial infarction compared to RepSox and Forskolin alone.

conclusionPsoralen enhances chemical direct cardiac reprogramming by activating metabolic and structural maturation programs through mitochondrial fission and PPARα-dependent signaling. The combined treatment provides functional benefits in myocardial infarction, highlighting psoralen as a promising small molecule for cardiac regeneration.