<scp>GDF15</scp> ‐Treated <scp>iPSC</scp> ‐ <scp>MSC</scp> ‐Derived Exosomes Alleviate Fibrosis Post‐Myocardial Infarction via Repression of the <scp>MFAP4</scp> / <scp>ERK</scp> /Drp1 Axis

Cardiac fibrosis post-myocardial infarction (MI) induces adverse cardiac remodeling, ultimately resulting in heart failure. Exosomes (EXOs) derived from mesenchymal stem cells (MSCs) have emerged as potent modulators of post-infarction remodeling, capable of limiting fibrotic responses. Our previous study showed that growth differentiation factor 15 as pretreatment promoted the protective effects of MSCs against myocardial fibrosis post-MI via paracrine actions. We investigated whether exosomes derived from GDF15-treated iPSC-MSCs (GDF15-iPSC-MSC-EXOs) could alleviate post-MI fibrosis and further explored the mechanistic pathways underlying their effects. In a mouse model of MI, EXOs released from iPSC-MSCs and GDF15-treated iPSC-MSCs were collected from culture supernatants and subsequently administered intramuscularly around the infarct area. Cardiac fibrosis was assessed by Masson's trichrome staining. A collagen synthesis model in mouse cardiac fibroblasts (mCFs) was established by transforming growth factor-β1 (TGF-β1) treatment in vitro. The mitochondrial morphology of mCFs under TGF-β1 stimulation was evaluated by Mitotracker staining. Delivery of EXOs from GDF15-treated iPSC-MSCs resulted in less fibrotic remodeling and better ventricular function after MI than exosomes from untreated cells. In TGF-β1-stimulated fibroblasts, both exosome types reduced fibrosis markers by preventing mitochondrial fission, with GDF15-iPSC-MSC-EXOs affording stronger protection. These effects were partly attenuated in the presence of the mitochondrial fission activator FCCP. Mechanistically, GDF15, which is rich in GDF15-iPSC-MSC-EXOs, inhibited TGF-β1-induced mCF activation via repression of the MFAP4/ERK/Drp1 pathway through a direct physical interaction with MFAP4. GDF15 conditioning strengthened the capacity of iPSC-MSC-derived exosomes to mitigate cardiac fibrosis following MI via inhibition of mitochondrial fragmentation in CFs by repressing the MFAP4/ERK/Drp1 pathway. GDF15 pretreatment is a novel strategy to enhance the cardioprotection of iPSC-MSC-EXOs against cardiac fibrosis post-MI.